Acid rain 2000

In present study, pollutant effects on needle surface characteristics of Pinus sylvestris in the area affected by a nitrogen fertilizer plant have been investigated over 1994–1997 year period. Near the factory, sites with 15–25-year-old trees on a 0.5–22 km interval were chosen. Mean monthly concentrations of NO₂ and NH₃ varied across the transect in the range of 1.8–8.8 μg m-3 and 1.8–69.3 μg m-3, respectively. NH₃ concentrations exceeded the critical level (>23 μg m-3) only in the 0.5 km vicinity. Assesment of needle surface wettability by measuring contact angles (CA) of water droplets and surface quality by measuring stomatai area covered by structural wax (SW) revealed significant (p<0.05) needle age, site, and year of sampling related differences. Comparison of SW between sites showed reliably (p<0.05) higher surface wax erosion on one-year-old needles sampled in the area, where ammonia concentration exceeds critical level. Significant correlations between site SW on one-year-old needles and distance from the pollution source, NO₂ and NH₃ concentrations were detected (r = 0.539; r =-0.495; r =-0.426; p<0.001, respectively). Correlations between CA and factors mentioned were lower.

Air pollution induced changes in pine needle chemistry were observed at sample sites in the surroundings of the Pechenganikel smelter. Close to the smelter, elevated concentrations of Ni, Cu and S were found (Ni: 0.7-1 mmol/kg, Cu: 0.4-0.5, and S 40-60 mmol/kg). Close to the pollution source, needles were enriched in Ni and Cu by needle age. Correlation and principal component analyses show that changes in the element composition of pine needles depended on air pollution and on natural factors as well. The contribution from air pollution increased with needle age. Besides direct input of pollutants from atmosphere, soil contamination and nutritional disturbance contributed significantly to the observed changes.

This paper outlines the results to date of the continuing acidic deposition study from 1997 in three teak plantations at the Na Pralan, Klangdong, and Donglan villages of Thailand. The aim of this study was to examine the impact on teak plantations of acid deposition — the increasing flow of chemical compounds including CO₂, SO₂, NO₂, and NO_X into the atmosphere. The 1997–1999 results showed no symptoms of acidity of the precipitation in the teak plantations at the treated sites (Na Pralan and Klangdong). During this period, the pHs of stemflow and throughfall were still over 7; and the pHs of the rainfall were around 7, except at Klandong where it dropped to around 5 in 1999. The pH and EC values were higher at the polluted sites than at the control site; this may be attributed to contamination with lime dust from nearby industrial plants, including cement factories and quarrying mills.Fresh leaves were contaminated with Sulphur to quite high levels at the Na Pralan site. This contamination seems to have affected the physiology, biomass and chemical content of the leaves. It might be due to pollution gases (SO₂ and NO_X) from the heavy trucks on the nearby Phaholyothin road. However, these gases could not be detected by a gas detector even though pollution seemed quite heavy. This study did not detect acid rain damage to the teak plantations.

C. japonica leaves were sampled monthly in a heavily damaged area (a-I: Saitama), a slightly damaged area (a-II: plains in Ibaraki), and a healthy area (a-III: mountainous areas in Ibaraki) in Kanto. The leaves were analyzed for apparent cuticular transpiration rates, amounts of epicuticular wax, and contact angles. Sb in aerosols deposited on the leaves was also analyzed. The transpiration rates and the increase in transpiration with leaf aging were higher in a- I than in a-II and a-III. Erosion rates of the wax were higher in a-I and a-II than in a-III. The decrease of contact angles with aging tended to be higher in a-I and a-II than in a-III. Rates of aerosol-Sb deposition on the leaves were in the order a-I ≫ a-II > a-III. The transpiration rates correlated with the values obtained from a linear binomial function that included the amounts of wax and aerosol-Sb as variables (r = 0.855, P < 0.01). In a-l, the large quantity of aerosols on the leaves (and probably gaseous air pollutants) may have increased the transpiration rates by ca. 50% owing to erosion of the wax and stomatal malfunction, placing C. japonica under chronic water stress.

Soil-growing randomized mixtures of ten European silver birch (Betula pendula Roth) clones, showing different ozone sensitivity, were exposed to ambient air (control) or 1.4–1.7x ambient (elevated) ozone over five growing seasons using free-air fumigation (FACE) approach. During the last season, the juvenile trees were measured for growth, net assimilation rate and starch content. In elevated-ozone plants, significant effects were observed as 21–28% reduced new leaf development, 44.8% lower dry mass of leaves and 33.8% lower dry mass of roots, as well as 7.6% lower RGR of leaves and 27.8% lower RGR of roots, leading to 16% lower root/shoot ratio. In addition, net assimilation rate and starch content were slightly (8.9% and 14.3%) reduced in ozone-stressed plants. The results indicated cumulative ozone-induced growth reductions over five years. Ozone-stressed trees with declined root growth may become susceptible to other environmental stresses such as water and nutrient deficiency, and lose belowground competitiveness, which may affect tree survival.

Effects of enhanced N, S and NS Acid additions, up to approximately 100 kg N and S ha-1y-1, are described for a 15-year-old Sitka spruce forest growing on an acid peat in Scotland. Groups of 10 trees, replicated over 4 blocks, have been treated at canopy height on approximately 50 or 100 occasions with 2 mm precipitation equivalent, between April and November, since 1996. Relative stem volume increment (RSVI) has been consistently higher in the NS Acid treated trees compared with control or N treated trees since the second year of treatment, although no dose response was found. Litterfall was also considerably increased in the NS Acid treatments and showed a clear dose effect but was not correlated with RSVI. Base cation concentrations in soil waters, collected using zero tension lysimeters reflected the presence or absence of the spray treatments and showed a dose related increase in response to NS Acid inputs. Treatment with 2NS Acid increased NH₄-N and NO₃-N by an order of magnitude. Results after 4 years of treatment showed a positive growth and litterfall response to NS Acid inputs but no effect of N alone. Enhanced stemwood growth may be linked to the higher base cation and phosphate concentrations measured in the soil water in the presence of NS Acid and S treatments.

Young trees of 14 species were exposed to ambient ozone (O₃), (charcoal-filtered air [CF] or non-filtered air [NF]) and/or acid mist (pH 5 or 3 : SO₄2, NO₃, Cl- at equivalent 1:2:1 ratio) over three seasons (from June 1993 to November 1995) using tunnel-type open-top chambers at two sites (Abiko: 25 ma.s.l. and Akagi: 540 m a.s.l.)in Japan. Ambient, 12-hr (0600-1800) mean O₃ concentration for April-September during the period of experiment at Akagi (41 ppb) was 40% higher than that at Abiko (30 ppb). The NF- and CF-chambers had 90% and 30% of ambient O₃, respectively. Significant decreases in biomass in the NF treatments were observed in Pinus densiflora, Larix kaempferi, Picea abies, Abies firma, Abies homolepis, Abies veitchii, Cryptomeriajaponica, Populus maximowiczii, Betula platyphylla, Fagus crenata and Zelkova serrata as compared with the CF treatment. These results indicate that the current ambient level of O₃ in Japan is high enough to have adverse effects on the growth of all tree species examined, except Pinus thunbergii, Chamaecyparis obtusa and Quercus mongolica. Increasing acidity of mist caused no growth decreases in all tree species examined However, the growth decreases by O₃ were greater at pH3 mist treatment than at pH 5 mist treatment on Abies veitchii and Fagus. this suggested that the O₃ effect on tree growth can be exacerbated by the deposition of acid mist, possibly associated with nitrate.

The effects of ozone (O₃) and soil water stress, singly and in combination, on the growth and photosynthesis of Fagus crenata seedlings were investigated. Four-year-old seedlings were exposed to charcoal-filtered air (<5 nmol mol-1 O₃) or 60 nmol mor-1 O₃, 7 hours per day (11:00)-18:00), for 156 days from 10 May to 11 October 1999 in naturally-lit growth chambers at 20/15C (6:00-18:00/18:00-6:00). During the same period, half of the seedlings in each gas treatment received 250 mL of water at the 3-day intervals (wellwatered treatment), while the rest received 175 mL of water at the 3-day intervals (water-stressed treatment). The exposure of the seedlings to O₃ caused reductions in the leaf, stem, root and whole-plant dry weights. The net photosynthetic rate at 350 μmol mol-1 CO₂, the maximum net photosynthetic rate at saturated CO_2- concentration, carboxylation efficiency of photosynthesis and Rubisco content were significantly reduced by the exposure to O₃. The soil water stress induced reductions in the stem, bud and whole-plant dry weights, transpiration rate and leaf water potential during the midday. The additive effects of O₃ and soil water stress were observed on the dry matter production, leaf gas exchange rates and leaf water potential. As a result, the whole-plant dry weight of the seedlings exposed to both stresses was markedly reduced compared with that of the seedlings exposed to charcoal-filtered air and grown in the well-watered treatment.

The effects of ozone (O₃) and excess soil nitrogen (N), singly and in combination, on growth, needle gas exchange rates and ribulose-l,5-bisphosphate carboxylase/oxygenase (Rubisco) contents of Pinus densiflora seedlings were investigated. One-year-old seedlings were grown in 1.5-L pots filled with brown forest soil with 3 levels of N supply (0, 100 or 300 mg N-L-1 fresh soil volume). The seedlings were exposed to charcoal-filtered air or 60±5 nL.L-1 O₃ (8 hours a day) in naturally-lit phytotrons for 173 days from 22 May to 11 November.The exposure to O₃ or high N supply to the soil caused a significant reduction in the dry weights of the seedlings. Although no significant interactive effects of O₃ and excess soil N were detected on the dry weight growth of the seedlings, the whole-plant dry weight of the O₃-exposed seedlings grown in the soil treated with 300 mg N-L-1 was greatly reduced compared with the control value. Ozone reduced net photosynthetic rate at 350 μmol mol-1 CO₂ (A₃₅₀), carboxylation efficiency (CE) of photosynthesis and Rubisco content without a significant change in the gaseous phase diffusive conductance to CO₂ (gs) of the needles. The excess soil N reduced the A₃₅₀,, CE, gs and Rubisco content of the needles. These results suggest that the reduction in the dry weight growth of Pinus densiflora seedlings induced by the exposure to O₃ and/or excess soil N was caused by reduction in the net photosynthetic rate mainly due to the decrease of Rubisco quantity in the chloroplasts.

Sulfuric acid mist exposure of bush bean leaves at a low rate of precipitation suggested that acid on the leaf surface was neutralized by cations leached from leaf tissues and that Ca-S compounds were accumulated on the leaf surface (Kohno, 1994). This report summarizes visual observations of the neutralization process of acid on leaf surfaces as determined by a pH-imaging microscope. Small droplets of sulfuric acid were placed on the adaxial leaf surface and allowed to air dry under laboratory conditions. Droplets (0.1μ1) of sulfuric acid took about 7–8 minutes to dry. Leaf samples were cut at various times after the acid droplets dried. The adaxial leaf surface was placed on the pH-adjusted agar film layer on the pH-imaging sensor of the microscope. Hydrogen ions dispersed into the film layer and resulting pH distributions were visualized as pH distribution patterns. The size of the acidic area generated became smaller with time after the acid was added and allowed to dry. Results indicate that leaves could neutralize the surface acid probably by ion exchange with cations from their surface tissues and could recover from strong temporary acid stress imposed by acid rain or acid fog in a relatively short period of time. Our findings indicate that acidic precipitation at current acidity levels does not pose a direct threat to plants.

There is a concern that soil acidification by acidic deposition, along with the resulting depletion of the labile pool of nutrient cations (e.g. Ca, Mg) and enhanced leaching of Al from soil may contribute to forest dieback. The molar ratios of Ca/Al or (Ca+Mg+K)/Al in the soil solution have been widely used as a criterion for risk of tree damage due to acidification. Intensity and quality of the crown and branch structure transformation due to formation of secondary shoots in successive series is a very sensitive indicator of long-term tree damage, and the subsequent regenerative processes. Soil water chemistry and crown structure transformation of Norway spruce were observed at 16 forest plots within the Czech Republic with the following results: parameters, expressing degradation processes in the crown (defoliation of primary structure), regeneration processes (percentage of secondary shoots) or synthetic stages of crown structure transformation showed high correlation with soil water (Ca+Mg+K)/Al ratio in organic horizons. No relationships were found for mineral horizons. The correlations between soil water and crown status parameters were considerably stronger when using the (Ca+Mg+K)/Al ratio rather than the Ca/Al ratio.

Acid atmospheric deposition results in increased levels of mobile aluminium (Al) in forest soils. Laboratory studies suggest that increased binding of Al to soil organic matter (SOM) in the forest floor results in decreased mobility of organic matter in soil water, viz. lower concentrations of dissolved organic carbon (DOC). Other laboratory studies indicate decreased decomposition rates of SOM as a result of Al binding. So far, little field evidence supporting these effects of Al on the lability of SOM have been reported. Here we present a field manipulation experiment in mature Norway spruce forest in Norway, where the content of Al in soil and soil water was increased. Increased Al in the forest floor caused a pronounced decrease in the leaching of DOC. Simultaneously, the decomposition rate of SOM decreased by 30% to 40%. This suggests that elevated Al in the forest floor stimulates accumulation of SOM. In a companion paper we present the effect of increased Al on forest vitality.

Aluminium (Al) has been considered to be a central element for risk evaluation of forest damage due to acidification. It has been hypothesized that Al reduces root growth, nutrient uptake and forest vitality. However, forest monitoring studies fail to show correlations between soil acidification and forest health. In general, no direct relation between Al concentration and forest health has been established. Here, Al concentrations in soil solution were manipulated by weekly additions of dilute AlCl₃ to levels that are believed to be unfavorable for plant growth. Four treatments (in triplicate), including a reference and three Al addition levels, were established. Effects of enhanced Al concentrations on fine root growth, nutrient uptake and crown condition in a mature Norway spruce forest in Norway were tested (1996–1999). After three years of manipulation, crown condition, tree growth and fine root growth were not affected by potentially toxic Al concentrations. However, the Mg content in current year’s needles decreased at the highest Al addition treatment. The Mg/Al ratio of fine roots of the same treatment had declined too, which suggests that Al blocked Mg uptake at the root surface. The manipulation will be continued for two more years.

Soil solutions were taken from three forest areas with granite bedrock in Japan (Abukuma, Tateyama and Hiroshima) to investigate pH values, forms of Al and the molar BC/A1 ratios. In each area, 10 sites were chosen for study. At each site, a target tree was selected, and two soil solution samples were taken from 10 cm depth at points 10 cm and 100 cm from the trunk of the tree to evaluate the effects of stemflow and throughfall on soil solution chemistry. Values of pH of samples taken 10 cm from the trunks (referred to as S samples) and 100 cm from the trunks (referred to as T samples) ranged from 3.66 to 6.52 and from 4.55 to 6.48, respectively. For Japanese cedar (Cryptomeria japonica) and Japanese cypress (Chamaecyparis obtusa) trees, S samples showed lower pH than T samples, whereas the inverse relation was observed for broadleaf trees. In the Abukuma and Tateyama areas, the concentrations of monomeric Al (Al_m) were mostly below 30 μmol L-1. In the Hiroshima area, however, extremely high Al_m concentrations (up to 293 μmol L-1) were observed at some sites. The molar ratio of BC (= Ca + Mg + K) to inorganic monomeric Al was higher than 1 for all samples, except for an S sample from the Hiroshima area having a ratio of 0.72.

Dry matter production, net photosynthetic rate, leaf nutrient status and trunk anatomical characteristics of Fagus crenata seedlings grown in brown forest soil acidified by adding H₂SO₄ solution were investigated. The soil acidification leaded to decreased (Ca+Mg+K)/Al molar ratio in the soil solution. Dry mass per plant of the seedlings grown in the soil treated with H+ at 120 mg.L-1 was significantly reduced compared with the control value at 0 mg-L-1. When net photosynthetic rate was reduced in the seedlings grown in the soil treated with H+ at 120 mg-L-1, the carboxylation efficiency and maximum net photosynthetic rate at saturated CO₂-concentration were lower than the control values. The addition of H+ to the soil at 120 mg-L-1 induced a reduction in the concentration of Ca in the leaf. By contrast, the concentration of Al in the leaf was increased with increasing the amount of FT added to the soil. The annual ring formed in the seedlings grown in the soil treated with H+ at 120 mg-L-1 was significantly narrower than that at 0 (control), 10, 30, 60 or 90 mg-L-1. Based on the results obtained in the present study, we conclude that Fagus crenata is relatively sensitive to a reduction in the (Ca+Mg+K)/Al molar ratio of soil solution compared with Picea abies.

Aluminium has a strong effect on many plant species, and there are reports of differing responses to Al between coniferous and broadleaf trees. A study was conducted on the effect of various concentrations of Al in nutrient solutions on tree root systems, using Chamaecyparis obtusa Sieb, (hinoki) and Quercus serrata Thumb, (konara) seedlings. Konara showed a tendency to enhance its root growth with increasing Al concentration in nutrient solution. The ability to change the rhizosphere pH decreased for both hinoki and konara with increasing Al concentration, but konara showed a higher pH change ability. It is suggested that konara and hinoki have different strategies to adjust the pH of acid soil.

Earthworms commonly dominate the soil fauna and they play important roles in terrestrial ecosystems, but their numbers decrease in acidic conditions. Their sensitivity to low pH was studied in Europe and their distributions were explained by their sensitivity. These kinds of studies have not been conducted in Japan. Sensitivity of a common Japanese earthworm, Allolobophora japonica, to acidified soils was studied. Worms withdrew its prostomium (oral organs) abruptly from Clark-Lubs buffer solutions of pH 3.9-4.1 when they were dipped into the solutions. The species did not burrow into soils of pH (H₂O)<3.6 and died on and in the soils of pH (H₂O) <4.0. It seemed that the species did not tolerate the soils of pH (H₂O)<4.0. The responses to acid soil were almost same as those of European species. Soils should be maintained above pH 4 for this species.

Variations in soil acidity and in biodiversity were analysed in the National Natural Park “Russian North”, European Russia. Improving soil quality from podzol, podzolic soil, dernopodzolic soil, brown earth to pararendzina leads to increase in diversity and changes in floristical composition, followed by changing of pine and spruce forest to mixed and birch forests. In PCA ordination species diversity, richness and evenness of trees, shrubs and vascular plants are closely connected with each other, and are represented by the first principal component. They are strongly correlated to the thickness of Al horizon, pH_h20 and pH_CaC12 in organic, surface and subsurface mineral horizons. Only bryophyte species richness and diversity are directly related to the thickness and weight of organic horizon, soil exchangeable acidity, and inversely related to the thickness of Al horizon and pH. Thus, the ordination of the major species diversity variables is highly related to soil pH, suggesting that pH is the best soil related predictor of species diversity parameters. Our study shows that plants notably respond to soil acidification in boreal forest ecosystems.

Integrated monitoring of ecosystems (IM) is an international co-operative programme (ICP) to control effects of air pollution and climate change on water, soil and biological systems. It is a part of the Convention on Long-Range Transboundary Air Pollution (CLRTAP) of the United Nations Economic Commission of Europe (UN/ECE). The ICP-IM is undertaken on sites/catchments to investigate acidification, eutrophication and heavy metals with an integrated approach. In Sweden, long-term time series from forest ecosystems, with a long and stable continuity, will reveal trends and changes in processes and enable modelling to be undertaken. Investigations of acidity/alkalinity in relation to mineral and organic acids indicated the importance of atmospheric deposition. Recent results show very high inorganic nitrogen retention (99%), a net loss of sulphur originating mainly from organic horizons, and a high inorganic aluminium content in the illuvial soil horizons which could be detrimental to forests. Forest deficiency could also be caused by an observed ongoing translocation of Zn to deeper soil layers implying a movement towards increased release to surface waters.

The foliar N content of bryophytes and Calluna vulgaris (L.) has been shown to be an indicator of atmospheric N deposition in the UK at a regional scale (1000km) and more recently on a smaller scale in the vicinity of intensive livestock farms. This work extends the geographical scale of the relationship between foliar N concentration of Calluna vulgaris and other ericaceous shrubs and N deposition with 2 measurement transects, one extending from northern Finland to southern Norway (2000 km) and the other extending from central Sweden to Stockholm, south east Sweden (330 km). Included in the second transect is a region of complex terrain in the Transtrand uplands, where the variation in N deposition with altitude and canopy cover was quantified using 210Pb inventories in organic soil. The relationship between foliar N (F_N) and N deposition was shown to increase linearly with N deposition (N_D) over the range 0.8% N to 1.4% N according to F_N = 0.040N_D + 0.793 (r2 = 0.70). The data are entirely consistent with earlier studies which together provide a valuable indicator of critical loads exceedance, the threshold value being approximately 1.5% N, which is equivalent to a N deposition of 20 kg N ha-1 y-1.

Increases in N deposition (wet and dry) have been associated with a decline in seminatural plant communities, adapted for growth on nutrient poor soils in the UK and Europe. The impacts of N deposition applied as either wet NH₄+ or gaseous NH₃ on vegetation (7 species) from acid moorland in SE Scotland were compared in a dose-response study. Wet N deposition at 0, 8, 16, 32, 64, 128 kg N ha-1 y-1 was applied as NH₄C1, and dry deposition as gaseous NH₃ (2, 6, 20, 50, 90 μg NH₃ m-3) under controlled conditions in open-top chambers. A strong linear doseresponse relationship (p<0.05) was found between foliar N content in all seven plant species and applied NH₄-N. However, in the NH₃ treatment, only C. vulgaris and P. commune showed a significant response to increasing N additions. NH₃ was found to increase the rate of water loss in Calluna in both autumn and winter by comparison with wet deposition. For Eriophorum vaginatum, the NH₃ and NH₄+ treatments showed significant N dose response relationships for biomass. A significant increase in above ground biomass, proportional to the added N, was found for Narthecium ossifragum when N was applied as NH₃ compared to NH₄+.

The effects of ammonium sulphate (NS) on the accumulation of nutrients in above and below ground biomass and soil were studied in a Norway spruce stand in south-west Sweden during 1988–1993. Ammonium sulphate addition resulted in nitrogen accumulation with 326 and 16 kg ha-1 in above and below ground biomass, respectively. Corresponding figures for the control plots (C) were 34 and 3 kg ha-1. Nitrogen accumulation in forest floor of NS was 266 kg ha-1 and 47 kg ha-1 in mineral soil. About 70% of added sulphate by fertiliser was retained in NS plots (482 kg S ha-1) of which 274 kg ha-1 was adsorbed in the mineral soil. The sulphate addition resulted in increased leaching of nitrogen, magnesium, calcium and sulphur. It is suggested that the spruce stand at the study site has a high capacity to accumulate nitrogen with a high above ground production. The high input of ammonium sulphate may in the long run result in increased losses of cations to ground water.

Ionic fluxes in a semi-mature stand of Sitka spruce (Picea sitchensis (Bong.) Carr.), on a spodosol in eastern Ireland, were monitored over an eight-year period, 1991-1998. The paper focuses on the long-term viability of forests in this region. Input-output balances, proton budgets and critical loads suggest that the long-term sustainability of forests in the region is threatened unless atmospheric emissions of anthropogenic substances can be controlled.

In a laboratory incubation experiment, nitrification potential, methane oxidation, N₂O and CO₂ release were studied in the organic soil layer (0-10 cm) of field lysimeters containing reestablished soil profiles from a 100-year-old Scots pine (Pinus sylvestris) forest of Norway. The experiment was designed as a full factorial (3 factors; N fertilisation rates, soil acidification, and plants), with three replicates. The more acidic irrigation (pH 3) significantly reduced nitrification potential and N₂O fluxes, methane oxidation and CO₂ release. We concluded that the reduction in soil N₂O release by severe acid deposition is partly due to reduction in nitrification potential. The highest N₂O fluxes were observed in the combination of fertilised planted and less acidic pH treatment. N fertilisation (90 kg N ha-1 y-1 with NH₄NO₃) increased soil N₂O release by a factor of 8 and decreased CH4 oxidation by 60–80% . Plant effects on soil nitrification potential and methane oxidation rates are discussed.

Critical loads of acidity have been used by the UNECE Convention on Long Range Transboundary Air Pollution for the development of protocols to control the emissions of acidifying pollutants. Since soil acidity has an effect on the mobilisation of heavy metals in the environment, it is important to understand the relationships between acidity and heavy metal pollution. This paper examines the relationships between soil acidification and heavy metal (cadmium, copper, lead and zinc) concentrations in topsoils and in stream sediments. It makes use of published heavy metal data and two indices of acidification: soil pH and soil acidity critical loads. For cadmium and zinc, a general increase in the ratio of stream sediment to toposil metal concentrations is seen with a decrease in soil pH and soil acidity critical loads. This demonstrates that where soils are more acidic and acid sensitive the metal concentration in the stream sediments is greater relative to that in the topsoil, suggesting mobilisation of these metals under acid conditions. Results for copper are similar but the relationship weaker. However, for lead the ratios tend to decrease with a decrease in pH and critical loads suggesting that where soils are more acid, lead remains in the soil rather than being mobilised into streams and precipitating onto stream sediments. This reflects the association between soil lead concentrations and soil organic matter content, which tends to be greater in acidic, peaty soils.

A 5-year Chinese-Norwegian research project was launched in the autumn of 1999. Forested sites for intensive studies are or will be established in the Chongqing municipality and in Guizhou, Hunan and Guangdong provinces in southern China. Previous studies have shown that harmful effects of acid deposition are likely to be most severe in this region. The research and monitoring sites shall give information about acidification mechanisms and effects on vegetation in order to improve policy oriented acidification models and critical load estimates as well as function as interdisciplinary training centers for acid rain research. Furthermore, the project shall improve the basis for developing an efficient regional acid rain monitoring system. At one site in Guizhou and one in Chongqing, research on soil and soilwater chemistry has been ongoing for several years. The forest at these sites appears to show symptoms of reduced vitality. The sensitivity of Chinese forests to acidification is uncertain and will be focused. Decision-makers should get an improved basis for optimal mitigation measures through the project.

Rain water at two forested sites in Guangzhou (south China) show high concentrations of SO₄2-, NO₃ and Ca2+ and display a remarkable seasonal variation, with acid rain being more important during the spring and summer than during the autumn and winter. The amount of acid rain represents about 95% of total precipitation. The sources of pollutants from which acid rain developed includes both locally derived and long-middle distance transferred atmosphere pollutants. The seasonal variation in precipitation chemistry was largely related to the increasing neutralizing capacity of base cations in rainwater in winter. Soil acidification is highlighted by high H+ and Al3+ concentrations in soil solutions. The variation in elemental concentration in soil solution was related to nitrification (H+, NH₄+ and NO₃-) and cation exchange reaction (H+, Al3+) in soil. The negative effect of soil acidification is partly dampened by substantial deposition of base cations (Ca2+, Mg2+ and K+) in this area.

The effect of acidic deposition on the soil under red pine forest in Chunchon, Korea was investigated. Precipitation, stream water, and soil solution chemistry were monitored at the watershed from 1997 to 1998. Acidity of the open-bulk precipitation was often neutralized by large amounts of ammonia (NH₃) that might have originated from livestock farming and fertilization. Estimated elemental budget at the watershed showed a positive correlation between loss of base cations and proton (H+) production due to nitrogen transformation in soil (ΔH+_NT:. When ΔH+_NT increased, concentrations of nitrate in soil solutions also increased. Consequently, pH values of soil solutions decreased, although ion exchange with base cations contributed to buffer reaction. Since acid buffering capacity of the red pine forest soil was small, it was concluded that the input of ammonium nitrogen enhanced nitrification in soil thus causing soil acidification represented by loss of base cations from the watershed.

Virgin fir trees have been dying on Mt. Oyama, which is located in the southwestern part of Kanto Plain, although the frequency of death seems to be reducing recently. We report elevational patterns of acid deposition in precipitation and throughfall under fir and cedar canopies and nitrogen saturation in the forest ecosystem on Mt. Oyama. The deposition fluxes of major inorganic ions in precipitation were nearly constant regardless of elevation except for hydrogen and ammonium ions, whereas the deposition fluxes of all major inorganic ions in throughfall among cedar increased. The 5-year average of annual nitrate deposition in precipitation from 1994 to 1998 showed 19.3–23.5 kg ha-1 yr-1 (annual inorganic total N deposition: 9.6–10.7 kgN ha-1 yr-1) at four sites ranging in elevation from 500 to 1252 m, whereas the deposition in both cedar and fir throughfall was over 6 times greater than that in precipitation. The average soil surface nitrate concentration in 1998 was 140 μg g-1 (the range: 21.1-429 μg g-1, n=80) and the 7-year average of nitrate concentration in stream water from 1992 to 1998 was 4.81 mg L-1 (the range: 2.38–20.6 mg L-1, n=317). Our results indicate that nitrogen saturation is occurring in the forest ecosystem because of high N deposition, probably via acid fog, on Mt. Oyama.

Nitrate leakage to a stream from a small forested watershed on Kureha Hill in Toyama Prefecture, Japan was investigated in order to assess its acid-base chemistry. Kureha Hill, located in Toyama City, receives high nitrogen loading from the atmosphere. In this area, there are several small streams characterized by a high concentration of nitrate and low ANC. Hyakumakidani, one of the most acidic streams on that hill, the average pH and ANC were 5.2 and-8 μeq/l, respectively. The weighted average nitrate concentration, which was 125 μeq/l, increased up to 370 μeq/l during high-discharge periods caused by heavy rainfall, while ANC decreased to-24 μeq/l at the same time. Our preliminary study using a two-stage tank model simulating the flow paths in the soil indicated that during high-discharge periods, the increased subsurface flow containing a high concentration of nitrate contributed to the increased nitrate concentration. In this watershed, the annual nitrogen budget from Aug. 1998 to Aug. 1999 showed that the loss of nitrogen exceeded the bulk nitrogen deposition, indicating that this watershed is under condition of nitrogen saturation. However, no visible attenuation has been observed.

High nitrogen, especially ammonium, input has been observed in Shichinohe, Aomori Prefecture, northeastern Japan. A monitoring study on precipitation, throughfall, and stream water has been carried out to estimate the stage of nitrogen saturation since 19%. Fifty-two to 70 % of nitrogen input in throughfall was retained in forest ecosystems. Nitrate concentration in stream water tended to decrease throughout the study. There was no symptom of nitrogen saturation at Japanese cedar stands in Shichinohe, although high nitrogen input in open bulk has been observed. Ammonium (NH₄+) was retained in the canopy. The ratio of NH₄+ input in throughfall to that by open bulk was 0.40–0.47. Total inorganic nitrogen input under the canopy amounted 0.68–0.72 kmolc ha-1 yr-1 (9.6–10.0 kg N ha-1 yr-1). Our results suggests that atmospheric nitrogen input has benefitted the tree growth.

High nitrogen, especially ammonium, input has been observed in Shichinohe, Aomori Prefecture, northeastern Japan. The monitoring study on soil and soil solution has been carried out to determine soil acidification status since 1996. Soils and soil solutions in Minamitonai and Haginosawa are not strongly acidic. Fluctuations in nitrate concentrations coincided with sodium (Na+) or calcium (Ca2+). Produced protons due to nitrification were exchanged with Ca2+ or neutralized by weathering process. Exchangeable Ca2+ accumulated in surface layers, particular in the older Japanese cedar (Cryptomeria japonica) stand (42 years old). Exchangeable Ca2+ affected soil solution chemistry and the Ca2+ concentration was significantly higher in the older Japanese cedar stand than that in the younger stand (22 years old). Base cations, especially Ca2+, accumulation prevented soil (solution) acidification in Shichinohe site.

To assess the influence of acidic deposition on the forest ecosystem, it is necessary to evaluate the gross amount of acidic deposition. In this paper, we discuss the variation of sulfate (SO₄2) and nitrate (NO₃) loads as well as related concentration from 1991 to 1999 in the Hinoki (Chamaecyparis obtusa) plantation in Kochi, southwest Japan. The annual precipitation varied significantly from 1,700 to 3,900 mm during the study period. The annual sulfate concentration of rainfall was about 15 μmol L-1, including about 80% non sea salt sulfate, while the annual nitrate concentration of rainfall was increased. The sulfate and nitrate concentrations of the through fall and the nitrate concentration of the stem flow were equal to or slightly higher than those of rainfall. However, the sulfate concentration of the stem flow was higher than that of rainfall, 21 to 55 μmol L-1. The sulfate and nitrate loads of rainfall were measured to be 27 to 46 and 14 to 43 mmol m-2 y-1, respectively. The sulfate and nitrate loads of the through fall were the same or slightly higher than those of rainfall. In contrast, the sulfate and nitrate loads of the stem flow were less than those of rainfall. Combined sulfate loads of the through fall and the stem flow reached about 1.5 times that of the sulfate load of rainfall.

SO₄2- NO₃- and H+ depositions are estimated in the Brazilian territory based on the existing rainfall chemical data and on annual rainfall distribution over the whole territory. Local and regional depositions are estimated. Rainfall chemical data over the Brazilian territory shows that the average pH values are usually low (between 4.0 and 5.5). These values are observed in the tropical Amazon forest as well as in urban areas. However, the rainwater acidity in the tropical forests are due to organic acids naturally produced by the vegetation while in urban areas the acidity is mainly due to acidic anion deposition (NO₃- and SO₄2-). In some Amazonian areas, the average input values through rainfall for NO₃- is about 0.06 keq.ha.yr-1 and for SO₄2- is between 0.23 and 0.54 keq.ha-1.yr-1. On the other hand, in some urban centers, such as São Paulo, values of .072 keq.ha-1.yr-1 for NO₃- and 1.16 keq.ha-1.yr-1 of SO₄2- are found and in sites where sulfate sources (coal mining) are present, as for the area of Florianópolis, values as high as 5.59 keq.ha-1. yr-1 for SO₄2- are found.

Recent advances in desert afforestation underlines its viability and importance in combating global warming and acidification. In this paper, the inter-relation between afforestation, global warming and acid rain has been analyzed. Numerical simulations indicate that afforestation of deserts has distinct advantage as carbon sink and as an important factor for changing microclimate of the region rather than a source of energy. Acidic deposition may well be utilised as fertiliser in nutrient deficit soil of tropical arid areas. However, past trends and projections of acidic deposition in arid areas adjacent to Thar deserts indicate an early efforts are required to cap the opportunity. Delays may contribute towards more incidences of failures.

The scientific support of negotiations on emission reductions under the framework of the Convention on Long-range Transboundary Air Pollution of the UN Economic Commission for Europe has been based during the last decade on the integrated assessment of sources, including abatement costs, and risks to receptors (e.g. forests, lakes) quantified by critical loads. The shift from a single-pollutant (sulfur) protocol in 1994 to a multi-pollutant protocol in 1999 necessitated an extension of the methods by which critical loads were computed and mapped. Instead of a single critical load for acidification, methods were now developed to assess the risk of acidifying effects of both sulfur and nitrogen deposition as well as the eutrophying effects of nitrogen on sensitive elements of the environment. Collaboration with a scientific network of 24 national institutions ensured a successful implementation of the proposed methodology across countries. This paper summarizes the methodology, describes the latest input data and presents critical load maps on the basis of which about 98% and 78% of European ecosystems would be protected against acidification and eutrophication, respectively, by the year 2010 according to the multi-pollutant multi-effect protocol.

The excess of acidic and eutrophying depositions over critical loads (critical load exceedances) is considered a measure for the risk of harmful effects on sensitive elements of the environment. The magnitude and the geographical distribution of critical load exceedances over Europe vary with the extent to which national emissions of sulfur dioxide, nitrogen oxide and ammonia are reduced. The scientific support of negotiations on emission reductions in the framework of the Convention on Long-range Transboundary Air Pollution (LRTAP) of the UN Economic Commission for Europe has been based on the integrated assessment of sources, including abatement costs, and risks to receptors (e.g. forests, lakes) using critical load exceedances. The shift from a single-pollutant (sulfur) protocol in 1994 to a multi-pollutant protocol in 1999 necessitated an extension of the methods by which critical load exceedances are computed and mapped. The focus changed from the protection of the most sensitive ecosystem against excessive deposition of one pollutant, to an assessment of the accumulated exceedance by more pollutants of all ecosystems. This paper presents and compares the different characterisations (“gap-closure methods”) used in those negotiations. It is shown that the approach finally used has several appealing features, but treats the exceedance as a linear damage function, thus going beyond the critical load definition as a simple on-off limit value.

The maximum critical load of sulfur and its exceedance by the sulfur deposition of 1994-1997 were mapped for South Korea with a spatial resolution of 11 X 14 km using the steady-state mass balance method. The Korean soil and geological maps were used as basis for the estimations of the critical alkalinity leaching and the weathering rate of base cations. The normalized difference vegetation index data obtained from the Advanced Very High Resolution Radiometer (AVHRR) together with the observed primary productivity of plants were used for the estimation of the critical uptake of base cations. Wet deposition of the non-sea-salt base cations was derived from measured base cation concentrations in precipitation, precipitation rate and air concentration of total suspended particulate while dry deposition of base cations was estimated using the inferential technique using scavenging ratios. The predominant ranges of base cation weathering, uptake and deposition were estimated to be of 200 – 600 eq ha-1 yr-1, 200 – 400 eq ha-1 yr-1 and 400-600 eq ha-1 yr-1, respectively. Critical alkalinity leaching was mainly in the range of 1000 – 2000 eq ha-1 yr-1 due to relatively high value of precipitation runoff. Exceedance of sulfur critical load was found at 40 % of the ecosystems considered mainly in the southeastern part of Korea, and about 60 % of Korea ecosystems were sustainable against sulfur acidity loadings.

The aim of the AIR-CLIM project is to perform an integrated analysis of the linkages between climate change and regional air pollution in Europe and to produce results that are relevant to European policy-making. Key elements of the analysis are on the impact side the exceedances of critical thresholds for air pollution and global change and on the cost side the estimates of costs to reduce emissions of greenhouse gases and air pollutants. The integrated modeling framework set up to meet these objectives consists of two state-of-the-art integrated models covering regional air pollution in Europe (RAINS) and global climate change (IMAGE), supplemented by new components. Based on a preliminary analysis it can be stated that climate change will make European vegetation in most regions less sensitive to acid deposition. Taking into account the emission trends the impacts of regional air pollution will decrease while the impacts of climate change increase. Different problems will be important in different regions: regional air pollution in Central and northern Europe, and climate change in southern Europe.

Although decades of acid deposition have apparently not resulted in surface water acidification in China, some surface waters may have the potential trend of being acidified, especially those in southern China. In this paper, a dynamic acidification model-MAGIC was applied to 100 surface waters in southern and northeastern China to evaluate the impact of acid deposition to surface waters and to determine their critical loads of S deposition, both regions having distinguishing soil, geological and acid deposition characteristics. Results indicate that most surface waters included in this paper are not sensitive to acid deposition, with critical loads of S for these waters comparatively high. On the other hand, surface waters in southern China, especially those in Fujian, Jiangxi and Guangdong provinces, are more susceptible to acidification than those in northeastern China, which coincides with their different patterns of soil, geological and acid deposition conditions. Among all the waters, a few small ponds, such as those on top of the Jinyun mountain and Emei mountain, are the most sensitive to acid deposition with critical loads of 1.84 and 3.70 keqha-1.yr-1, respectively. For the considerable ANC remaining in most 100 surface waters, it is not likely that acidification will occur in the near future for these waters.

Critical loads are used in international negotiations to reduce acid deposition resulting from emissions of sulphur and nitrogen compounds within Europe. For freshwater ecosystems, the First-order Acidity Balance (FAB) model is used to generate national maps of critical loads and exceedances for both sulphur (S) and nitrogen (N). In Wales, two survey datasets have been used to calculate critical loads and exceedances; one based on water bodies selected to be “mostsensitive” to acidification within a 10 km grid and the other based on a random selection of standing waters. Both datasets indicate that critical loads were exceeded in 1990 in a significant proportion of Welsh lakes and streams; 36% of sites in the grid-basea survey and 31% of sites in the random survey. However, implementation of the Gothenburg Protocol would protect all but 6% of sites in the grid-based survey and all sites in the random survey. Assessment of the relative success of the Gothenburg Protocol in protecting Welsh freshwater ecosystems therefore depends on the site selection strategy employed.

In the UK the “critical loads” approach has been used to derive maps based on the 10km x 10km national grid. However, this grid based approach is inappropriate for catchment scale management and these maps cannot be used for “stock at risk” assessments of the number of water bodies or lengths of streams in a given area that may be vulnerable to acidification. Critical loads are determined across two large river catchments in England (The Duddon) and Wales (The Glaslyn). High resolution, digital datasets are used to characterise the attributes of each subcatchment in terms of land cover, soil, geology, topography and topology. Empirical models used to examine the relationship between these attributes and critical loads indicate that the former can be used to account for significant variation in the latter. However, these relationships can vary from catchment to catchment. Thus, although this approach provides the potential for identifying sensitive surface waters on a catchment wide basis, it is likely that models will need to be parameterised on a catchment specific basis.

Acidification has the potential to become a widespread problem in parts of Asia. Just how widespread this risk may be is discussed by comparing sulphur deposition to critical load estimates, taking into account neutralising base cation deposition from soil dust. Two scenarios for the sulphur emission in 2025 are used as inputs to the MATCH atmospheric transfer model to estimate sulphur deposition scenarios. Net acidic deposition using a low and high base cation deposition input is compared to a map of sensitivity of terrestrial ecosystems to acidic deposition. Two ranges of critical loads assigned to this sensitivity map are used. The variability in the maps showing risks of acidification using low and high estimates for critical loads and base cation deposition for two different development pathways is discussed. Certain areas are shown to be at risk in all cases whereas others are very sensitive to the values used to estimate risk.

A number of positive changes have taken place since Estonia regained its independence in 1991. Air pollution from stationary sources has decreased over 2.5 times during 1990-1999, emissions of solid particles and SO₂ have declined 74% and 60%, respectively. The content of heavy metals in Estonian mosses has decreased in comparison with the early 1990s. Last five years occurrence of different kind of damages on decidious trees has not been frequent.Those facts indicate that air pollution with heavy metals and other pollutants has diminished during the last few years. As the pH of precipitation fluctuates in different parts of Estonia, it is very important to study the effect of precipitation on ecosystems on the basis of critical loads. Results indicate that, as for eutrophicating nitrogen, the actual nitrogen deposition in North-East Estonia and West-Estonian islands roughly coincides with the limits for pollution endurance. This pattern also applies to the total deposition of sulphur and nitrogen in South, North and North-East Estonia, although in some Northern and North-Eastern areas pollution endurance limits have been exceeded.

Critical loads of acid deposition for ecosystems in South China are derived by synthesizing the critical loads of acid deposition for soils, the critical loads of SO₂ dry deposition for ecosystems, as well their exceedance. The results show in the southeast of Sichuan province around Chongqing municipality, the central and north of Guizhou province around Guiyang municipality, and the most areas of Jiangsu province, both the critical loads for soils and critical loads of SO₂ dry deposition are exceeded. In Guangxi Zhuang Autonomous Region and some areas among Jiangxi, Zhejiang and Anhui provinces, the critical loads of SO₂ dry deposition is the only restricting factor. There is no area where the critical load for soil is the only restricting factor in South China, so only the critical load for soil is not enough to be the basis to make sulfur abatement scheme.

Critical loads of acidity were calculated using the PROFILE model to assess the forest ecosystem sensitivity to acid deposition in the Asian part of Russia — Siberia. The main input parameters and the output were mapped. At present atmospheric inputs of acid forming pollutants to the study territory are mainly related to transregional and transboundary pollution from Europe. It was shown that the most sensitive to acid loading are ecosystems of the Tundra zone and of the East Sayan mountains’ coniferous forests with dystric cambisols and gleysoils, critical loads of actual acidity (CL(Ac)) = 0-0.3 keq/ha/yr. The most tolerant ecosystems are ecosystems of deciduous forests with podsoluvisols, luvisols and humic luvisols of South Taiga zone in West Siberia, CL(Ac) = 3.5-7.0 keq/ha/yr. Generally the values of critical loads are increasing from the North to the South and from the East to the West following the bioproductivity, annual soil temperature and alkalinity of deposition increases.

Critical loads of nutrient and acidifying nitrogen, as well as of sulphur and acidity, were derived for various ecosystems in China using the steady state mass balance (SSMB) equations. The weathering rates of major soils necessary for applying SSMB were calculated through the PROFILE model on the basis of mineralogical data from experimental analysis. The growth uptakes of nitrogen and base cations were also derived by multiplying the annual increases in biomass with the element contents of the vegetation. Using a geographical information system (GIS), l°(latitude)xl°(longitude) critical load maps of China with different percentiles were compiled. Results indicate that low critical loads of S (< 0.5 keq.ha-1a-1) occurred predominately in southwest and northeast China, and the critical loads of southeast China were intermediate and in the range of 0.5-1.0 keq.ha-1a-1. In addition, the critical loads of N were very low for desert ecosystems in northwest China and high for agricultural ecosystems in east China. Among the ecosystems with intermediate critical load of N, coniferous forests may be more sensitive to N deposition than broad-leaf forests and temperate steppes.

Uncertainties in the assessment of critical loads for acidic deposition are caused by the choice of biological indicators (BI), critical chemical values (CCV), the current methods used to determine critical loads for an ecosystem, and deficient field data. This paper focuses on the present steady-state mass balance (SSMB) approach, dynamic models and the importance of changes in atmospheric base-cation deposition (BCD), particularly in China. It is argued that 1) for the SSMB approach much uncertainty may come from the choice of BI and the related CCV, and long-term and large-scale monitoring data on weathering rates and growth uptake are urgently needed, especially in China, 2) significant uncertainty may be caused by changes in BCD during SO₂ emission controls, particularly in China, 3) constructing a mechanistic Al submodel may be a promising direction for dynamic models, and 4) the nutrient cycle in the vegetation through biogeochemical processes should be incorporated into dynamic models but the input requirements should be moderate for broad application considerations. Generally higher BCD, different soil components and characteristics and different vegetation types in China compared to Europe and North America suggest that more field investigations on BI and their corresponding CCV be carried out before application of current approaches to specific areas, particularly in China.

Acid deposition has been monitored in the natural vegetation of the western part of Tokyo, especially in the Okutama Mountains and surrounding areas. However, it is difficult to grasp the condition of acid deposition and the possible impacts on the vegetation in the whole area. Therefore, we attempted to make gridded acidic deposition maps and critical load maps. The grid size was 30 seconds latitude and 45 seconds longitude. Monthly wet deposition in the fiscal year of 1997 was calculated by multiplying concentration of wet deposition and precipitation. Concentration of wet deposition was estimated by averaging the data monitored at the nearest three stations with the inverse of distance as the weight. Precipitation was estimated by step-wise multiple regression with geographical factors as explanatory variables. Critical loads were estimated using the steady-state mass balance model with some modifications. As result, it was found that sulfur deposition had exceeded in most of the western part of Tokyo.

The European steady-state Simple Mass Balance (SMB) model and the dynamic soil acidification model SAFE were used to assess the risk of future forest soil acidification in Switzerland. 2010 deposition forecasts on a 150x150 km grid resolution as well as corresponding ecosystem protection levels were obtained from RAINS model runs based on the 1999 Gothenburg Protocol obligations under the UN/ECE LRTAP Convention. Deposition values for 2010 on the national resolution were derived by scaling down present l x l km deposition values according to the deposition trends at the 150x150 km grid resolution. Meeting the Protocol obligations will reduce the percentage of Swiss forest ecosystems not protected against acidification between 1990 and 2010 from 41 to 4% according to the RAINS assessment and from 63 to 16% according to the assessment with the SMB at the lxl km resolution. The dynamic approach indicates, however, that soil conditions may not improve as much as these steady-state models suggest. By 2010, 39% of the sites considered will still have soil solution Bc/Al molar ratios below 1 at least in one soil layer. Nevertheless, deposition reductions obtained from the implementation of the new protocol will prevent the major part of Swiss forest soils from further acidification. Aiming at recovery of the more sensitive forest ecosystems would require emission reductions beyond the Protocol’s obligations.

Many ecosystems in Switzerland suffer from eutrophication due to increased atmospheric nitrogen (N) input. In order to get an overview of the problem, critical loads for nutrient N were mapped with a resolution of 1x1 km applying two methods recommended by the UN/ECE: the steady state mass balance method for productive forests, and the empirical method for seminatural vegetation, such as natural forests, (sub-)alpine or species-rich grassland and raised bogs. The national forest inventory and a detailed atlas of vegetation types were used to identify the areas sensitive to N input. The total N input was calculated as the sum of NO₃,-NH₄+, NH₃, NO₂ and HNO₃ wet and dry deposition. Wet deposition was determined on the basis of a precipitation map and concentration measurements. Dry deposition was calculated with inferential methods including land-use specific deposition velocities. The concentration fields for NH₃ and NO₂ were obtained from emission inventories combined with dispersion models. Reduced N compounds account for 63% of total deposition in Switzerland. As indicated by exceeded critical loads, the highest risk for harmful effects of N deposition (decrease of ecosystem stability, species shift and losses) is expected on forests and raised bogs in the lowlands, where local emissions are intense. At high altitudes and in dry inner-alpine valleys, deposition rates are significantly lower.

In many countries there has been much concern over maintaining biodiversity in natural ecosystems in the face of pressures such as changing land use and pollution. The 1992 UN Convention on Biodiversity calls upon signatories to develop national strategies for the conservation and sustainable use of biodiversity. In the UK, the potential impacts of sulphur and nitrogen deposition at the national level are being assessed using national critical loads and modelled deposition maps, together with available information on the occurrence of habitats and plant species. This simple approach gives an indication of the areas where atmospheric deposition may have impacts on biodiversity. The results of the analyses are presented and the strengths and weaknesses of the methods used are discussed. This first approach to considering the effects on biodiversity shows the importance of including the effects of atmospheric deposition in any biodiversity action plan. It also highlights those areas where more or improved information is required for the national strategy. With the modelled deposition data available, it would seem that reduced impacts are to be expected by 2010. However, higher resolution deposition data, better estimates of ammonium deposition, consideration of temporal aspects and the dynamics of change, and the use of higher resolution biological data sets are likely to suggest greater impacts than current predictions.

Environmental organisations in the UK have shown increasing interest in freshwater critical loads and acid sensitivity maps as a means of assessing pollution at the local and regional level. These maps can be used to identify sensitive areas when considering catchment management plans. The use of national data sets to map the sensitivity of freshwaters to acidification, highlighted the problems of relating national datasets to smaller, localised areas. The study described here investigated the use of detailed large-scale maps to predict the sensitivity of surface waters to acidification for two river catchments. Three large-scale acid sensitivity maps were produced and validated using measured freshwater critical loads. In addition, a score system relating to the buffering capacity for each soil and geology type was devised. The score value was found to have a better correlation with water chemistry and freshwater critical loads than the acid sensitivity maps. The study concluded that it was not necessary to use the largest scale data available in order to improve predictions of sensitive areas.

The weathering rates of forty-seven stream catchments in the English Lake District were calculated using 1) critical element ratios; 2) mass-balance budgets; and 3) the MAGIC model. There was a great deal of variability in the weathering rates of the five different parent material groups (greywacke, slate, andesite, tuff and granite) found in the study area. However when individual catchments were considered, the three methods provided consistent base cation weathering rates. This suggests that any of the methods could be employed for future catchment weathering studies. This paper also explores the implications of the weathering results when considering the possibility of the area becoming acidified due to increased loads of sulphur and nitrogen in the future.

Adaptation of the steady-state soil chemistry model PROFILE was studied, on the following two parts, to calculate the critical loads for East Asian soils: (1) Dissolution rate coefficients of volcanic glass were derived from published experimental data, and calculated field weathering rate was compared with the rate estimated based on Sr isotope analysis. When BET surface area of sand fraction was regarded as mineral surface area, the calculated rates fairly agreed with the estimate, suggesting that sand fraction surface area is a reasonable estimate of weatherable mineral surface area of volcanic soils. (2) In repeated leaching experiments, Al solubility of a number of Japanese soils was explained by a model which assumed complexation of Al to soil organic matters. Such an Al solubility model is more appropriate for predicting soil chemistry than apparent gibbsite dissolution equilibrium.

Acid deposition in eastern Asia will increase and freshwaters in Japan are likely to become acidified in future. In order to make long-term predictions about freshwater acidification, it is necessary to evaluate acid neutralization mechanisms in Japanese watersheds. Ikeda and Miyanaga (1999) earlier proposed a method of separating acid-neutralization capacity into chemical weathering and cation exchange. By this means, we were able to assess the effect of hydrogeochemical properties on chemical weathering and stream water chemistry for three watersheds in Japan. On the basis of this assessment, acid-neutralization stream water chemistry was predicted using the ILWAS (Integrated Lake-Watershed Acidification Study) model. The main factors determining acidification are the thickness of weatherd profile and chemical weathering rates. The principal results are: (1) for non-acidified watersheds in Japan, acid deposition is neutralized by chemical weathering of primary minerals; (2) freshwaters in Japanese watersheds will not acidify even if acid deposition increases to the extent found in an acidified watershed in the U.S.A.

Base cation (BC) concentrations of rain, throughfall, percolation from leaf litter, and soil solution were periodically measured in two forests: Kannondai (red pine stand on volcanic soil) and Yasato (deciduous stands on granitic soil). Calculation of a BC budget gave the rate of BC release from soils; the BCs originated from mineral weathering and cation exchange. Weathering rates under field conditions were estimated from the Sr isotope ratios (87Sr/86Sr) of water and soil samples. Isotope ratios decreased in the order rain > throughfall > percolation > soil solution. Clay and silt had extremely high isotope ratios; this suggests that the sandy fraction, whose isotope ratio was smaller than that of the soil solution, was the main contributor to mineral weathering. Estimated BC weathering rates (kmol_c-ha-1y-1) were 1.16 for Ca and 0.57 for Mg at Kannondai, and 0.82 for Ca and 0.51 for Mg at Yasato. The unexpected high weathering rate of granitic soil in Yasao was due to the wide coverage of the original parent material by volcanic ash. The contribution of cation exchange derived by subtraction was a little smaller than the weathering rates and was similar to the values estimated from a dynamic model that we developed.

The essential parameters needed for the calculation of critical load of sulfur, CL(S), are base cation weathering rate, base cation uptake, acid neutralizing capacity leaching and base cation deposition. These parameters are estimated and mapped for the most area of terrestrial ecosystems of Thailand using data of national data soil survey. The values of CL(S) range from <200 to 2,225 eq.ha-1yr-1 and about 70% of terrestrial ecosystems are characterized by low values (<200 eq.ha-1yr-1). These CL values reflect the sensitivity of Thai ecosystems to sulfur deposition.

Because of the deleterious effects of acid rain and the need to predict reversibility of acidification, various scientific tools such as modeling, stable isotopes and flux/budget calculations have been used in biogeochemical sulfur (S) research. The aim of this study was to evaluate consistencies and discrepancies between these different tools. While modeling has been seemingly successful in predicting S dynamics in soil solution and stream water by considering inorganic sulfate sorption and desorption only, stable S isotopes indicate that biological S turnover plays a crucial role for the sulfate released to soil solution and stream water. A comparison of budget calculations with soil S pools reveals that inorganic sulfate sorption and desorption are the controlling processes as long as deposition is high (> 15 kg S ha-1yr-1) and soils have a high sulfate sorption capacity. This explains the successful model predictions of the last two decades. However, for soils with low sulfate sorption capacity and under low sulfate deposition, organic S seems to be a significant source for stream water sulfate and has to be considered in future modeling.

In addition to strong natural stresses forest ecosystems in the Kola Subarctic, Russia, . receive high loads of sulphur and heavy metals from the nickel smelter. To estimate soil response to acid deposition we compared the soil field data along a pollution gradient and simulated time effects. Multivariate technique was applied to investigate spatial distribution of soil field data. Time response of soils to acid deposition was evaluated with the SMART model. According to field observations there is no evidence for strong soil acidification effects close to the smelter. Concentrations of exchangeable Ca and base saturation increase, while acidity decrease in lower soil mineral horizons towards the pollution source. However, some features seem to reflect the early stages of the started acidification. Most soil profiles have low pH values. Despite increasing of exchangeable Ca and Mg towards the smelter in lower mineral horizons due to geological inheritance, they do not reveal the same trends in the upper ones. Concentration of exchangeable K in organic horizons decreases towards the smelter, thus confirming the starting acidification. As result, exchangeable base cations are depleted in the considerable part of shallow soil profiles. According to model simulation the present acid load does not effect considerably on forest soils in background areas, however, dramatic shift in soil chemistry near the smelter is expected within several decades. Due to low pool of exchangeable base cations and low weathering rate continued acid deposition can lead to increased soil acidification and nutrient imbalance.

Concern about acidification in upland areas has brought about the need to model the stream hydrochemical response to deposition and land-use changes and calculate critical loads. Application of dynamic models such as MAGIC are preferable to steady-state methods, since they are able to produce an estimate of the time scale required to meet some water chemistry target given a reduction in acid deposition. These models typically consider annual changes in stream chemistry at one point. However, in order to protect biota from ‘acid episodes’, quantification of temporal variability needs to encompass event responses; in addition spatial variability across the catchment also needs to be considered. In this paper, modelling of both spatial and temporal variability is combined in a new framework which enables quantification of catchment hydrochemical variability in time and space. Both low and high flow hydro-chemical variability are quantified in terms of statistical distributions of ANC (Acid Neutralisation Capacity). These are then input as stochastic variables to an EMMA (End-Member Mixing Analysis) model which accounts for temporal variability and ANC is hence predicted as a function of time and space across the whole catchment using Monte-Carlo simulation. The method is linked to MAGIC to predict future scenarios and may be used by iteration to calculate critical loads. The model is applied to the headwaters of the River Severn at Plynlimon, Wales, to demonstrate its capabilities.

The model SONOX has been developed that replicates the sequence of events on the way from emission of sulfur and nitrogen to the potential risk to forest ecosystems as reflected by critical loads exceedance. The model produces a set of emission, deposition and critical load maps in various spatial resolutions as well as maps of critical loads exceedances dynamically generated in response to various sulfur and nitrogen emission scenarios. Optionally, also the share of forest areas protected or unprotected against acidification is spatially presented. The model provides a decision tool to develop strategies aimed at the abatement of excess sulfur and nitrogen emissions. The present version of the model has been tailored to and implemented for Polish conditions. This model has been used to analyse the trends in impacts of acid deposition on Polish forest ecosystems.

This study is based on research of throughfall formation and soil chemistry processes. Through the experimental verification of the cation exchange part of the simulation model; making use of results of the flux of acid deposition on the forest and the chemical weathering of soil mineral, we predicted the future soil acidification. The result indicated that chemical weathering occupies the important portion of acid neutralization capacity of the soil and that significant soil acidification will not occur in this field within 40 years, even if the present acid load continues in the future.

The geochemical model MAGIC has been applied to the Abborrträsket lake catchment in northern Sweden for the period 1843-2000. The two objectives were to 1.) simulate historical biogeochemical fluxes and pools and 2.) test whether the MAGIC model of biogeochemical cycling contradicts the published diatom record of a relatively stable pH (around 6) during the last two centuries in this weakly buffered, acid sensitive lake. Abborrträsket has received elevated sulfur and nitrogen deposition in the second half of the 20th Century and had a large part of its catchment clearcut in 1975. The MAGIC simulation of very small pH decline from 6.1 to 5.9 between 1843 and 1987 was comparable to the published diatom reconstructions of almost stable lake water pH up until the lake was limed in 1988. MAGIC also simulated the modern soil and water chemistry, including lake liming. Thus the diatom indication of stable pH cannot be dismissed as necessarily incorrect.

Since 1988, a network of lakes and streams has been monitored in areas of the UK sensitive to surface water acidification. Analysis of 10 years data has focused on the identification and quantification of time-trends in chemical parameters, to establish whether declines in emission of acidifying pollutants have resulted in recovery of acidified surface waters. A national decline in S deposition in the UK since 1988 has not generally been accompanied by a significant improvement in freshwater chemistry. At the three sites where xSO₄ concentrations have declined, NO₃ has increased and there has been no increase in pH or alkalinity. Upward trends in pH and alkalinity observed at several other sites are not associated with downward trends in acidic anions. Temporal variation in xSO₄, NO₃, acidity, DOC and other important meaures of surface water quality can all be linked to decadal-scale variation in climate, and this has important implications for the detection of recovery-related trends.

A two year study of planktonic and littoral microcrustaceans (Cladocera and Copepoda) from 15 lakes in the southeastern part of Norway, Østfold county, document the recovery of acidified lakes due to liming. Six lakes that where limed about 10 years ago, seven acid and two neutral reference lakes, were sampled twice a year (1998 and 1999). One acid lake was limed in autumn 1998. Qualitative nethaul samples from the deepest part of the lake and from the most frequent habitat in the littoral zone were used. The limed lakes had a species composition which indicates that these lakes are about to recover. Species associated with neutral lakes dominates while acid-tolerant species were rare. The acidsensitive species, Daphnia longispina and D. cristata, were found in the limed lakes. This study shows the usefulness of a low-cost sampling program where microcrustaceans are used as bioindicators of recovery.

Increased pH in acid lakes changes the crustacean fauna from communities dominated by acid-tolerant species to communities dominated by more acid-sensitive species. Studies from Canada (Killarney) and southeastern Norway (østfold county) have demonstrated that planktonic and littoral crustaceans can be used as indicators of such recoveries. In both places the cladocerans Alona rustica and Acantholeberis curvirostris were found in acidic lakes, whereas Alona costata and the copepod Eucyclops macrurus were found in near neutral lakes. The calanoids Diaptomus minutus in North America and Eudiaptomus gracilis in Europe, both dominate in acidic water, and may ecologically be equivalent species. Sometimes the same species occur at different pH in the two continents. Bosmina longirostris and Alonella excisa may serve as examples, but a pertinent question is whether or not they are really the same species.

Multivariate methods were used to relate microcrustacean (pelagic and littoral) richness and composition (presence/absence) to water quality and other environmental variables. All acidification variables (pH, aluminium, ANC) snowed significant correlation with both species richness and composition. The variation in microcrustacean richness was best explained by the combination of dissolved organic carbon (DOC), fish species richness and lake area. Of 16 variables tested, pH showed strongest correlation with the main gradient in the crustacean composition explaining between 13 and 16% of the variance in the species data (CCA). pH, elevation, lake area, average depth, DOC., conductivity and fish species richness explained 30–54% of the total variance. Stronger correlation was obtained between species composition and environmental data in analyses which included the between-year differences than analyses based on the cumulative species records. Analyses based on the pelagic species exclusively gave similarly stronger correlation than analyses based on all crustacean species. Small changes in the species composition during the three years of study may be an indication of recovery of microcrustaceans in Killarney lakes.

On a large scale, the acidified River Bjerkreim, southwestern Norway, has been treated with lime since the autumn 1996. During the Atlantic salmon (Salmon salar) smolting period pH has been above 6.2 and LAI concentrations below 10 μg L-l. Before 1996, only the western part of the watercourse harboured acid-sensitive species, such as the Atlantic salmon, snails, mayflies, daphnids and Gammarus lacustris. Prior to liming in 1996, Atlantic salmon fry (0+) and parr (≥1+)were found in 4 of 20 sampling sites, contrary to 17 (fry) and 12 (parr) in 1999. Atlantic salmon catches have increased from about 0.8 tons in 1994 to about 10 tons in 1998 and 1999. Acid-sensitive invertebrates have invaded the limed parts of the river.

Experimental addition of phosphate to enclosures in an acidified lake in Southern Norway was performed to study the effect on nitrate, pH and labile aluminium along a gradient of phosphate from 4-19 μg P L-1. Nitrate decreased from 180 μg L-1 to below detection limit after three weeks at P-concentrations > 17 μg L-1, due to phytoplankton uptake. pH increased from 4.9 to 5.2, corresponding to a 50% decrease of H+-equivalents from 12 to 6 μeq L-1 due to algal uptake of H+-ions when assimilating NO₃-ions. Due to the increased pH and probably also precipitation with phosphate, concentrations of labile aluminium decreased from 150 to 100 μg L-1 within the P-interval 4–19 μg L-1. Algal biomass increased from 0.5 to 6 μg chlorophyll a L-1 along the same P-gradient. The results suggest that moderate P-addition (< 15 μg P L-1 to avoid eutrophication problems) can improve water quality in moderately acidified lakes, and also increase nitrate retention in strongly acidified lakes. In humic lakes, the treatment will be less efficient due to light limitation of primary production and the presence of organic acids.

Due to acidification, 18 Norwegian stocks of Atlantic salmon are extinct and an additional 8 are threatened. In the two southernmost counties, salmon is eradicated. Due to the high acid sensitivity, production of salmon was greatly reduced as early as 1920, several decades before acid rain was recognized as an environmental problem. International agreements on reduced atmospheric emissions will reduce acidification effects in Norway substantially during the coming 20 to 50 years. However, the extreme acid sensitivity of salmon makes the destiny of this species in Southern Norway uncertain. Liming is an effective measure to protect and restore fish populations in acidified waters. Liming of acidified salmon rivers has become important in Norway in recent years which in combination with reduced emissions will be an important contribution to protection of the Atlantic salmon species. In this paper we give an overview of the effects of acidification on Norwegian salmon and discuss different aspects of mitigation measures; the expected effect of international agreements on reduced atmospheric emissions, the expected effect of liming on salmon production and the possibilities of re-establishing self sustaining salmon stocks in limed rivers.

The Atlantic salmon population in the River Otra, southern Norway was lost during the 1960’s due to acid rain and industrial and municipal pollution. The industrial and municipal pollution sources were sanitized by 1995. A concurrent reduction in acid deposition has during the last 10 years raised pH from 5.2 to 5.7 and reduced inorganic monomeric Al from 71 to 28μg Al L-1 above the industrial area. The water quality improvement resulted in salmon fry again being caught from 1995. Physiological measurements (blood parameters and seawater tolerance) performed on smolts of Atlantic salmon exposed within the river during the spring of 1999 suggests that the smolts were fully smoltified and seawater tolerant, despite having moderate gill morphological changes and having moderate high gill Al concentrations (70–80μg Al g-1 dw). The smolt quality measured suggests that the river again can support a native salmon population, provided no negative change in water quality. Winter episodes and acid tributaries within the watershed can, however, offset the recovery process.

Temporal changes in densities of young brown trout (Salmo trutta ), mainly of age 0+, and in water quality (pH and alkalinity) were assessed by means of electrofishing in lake tributaries in three acidic, softwater watercourses in western and southwestern Norway; Gaular and Vikedal (1987–1999) and Bjerkreim (1988–1999). Approximately 74 sites were sampled each year. Most of the streams were acidic with mean annual pH levels between 5.1–5.9. Alkalinity and pH increased significantly in all three areas during the study period. Brown trout fry densities increased significantly during the period in Vikedal and Bjerkreim. Also in Gaular, the density of young brown trout has exhibited a positive trend in recent years. We suggest that the increase in the density of young brown trout is because the study areas have became less acidified during recent years due to reduction in sulphate deposition.

In order to test whether major reductions in acid inputs had improved water quality sufficiently for fish populations to recover, we stocked wild European perch (Perca fluviatilis) in three highly acidified lakes that had previously supported this species, and in one limed lake. The fish, which were introduced from a local lake (donor lake), generally ranged from 12 to 16 cm in total length, and were stocked at densities of 117–177 fish ha-1. The untreated lakes were highly acid, with minimum pH values and maximum inorganic aluminium concentrations (Al_i) during the spring of 4.6–4.7 and 118–151 μg L-1 respectively. In the limed lake, the corresponding values for pH and Al_i ranged between 5.8 and 6.6 and 5 and 19μig L-1 respectively. Gill-netting in two subsequent years after the introduction yielded only a few recruits (0+) and one adult in one of the three acidified lakes in one year only. However, stocked perch reproduced successfully in both years in the limed lake. There was a significant linear relationship between the catches (CPUE) of juvenile perch (age 0+) in the different lakes in the autumn and the water quality in May (time of hatching), both in terms of Al_i (r2=0.934, P<0.05) and pH (r2=0.939, P<0.05). Our data suggest unsuccessful recruitment in waters of pH <5.1 and Al_i> 60 μg L-1.

The perch population of Lake Vähä Valkjärvi, a two hectare clear-water lake in southern Finland, decreased due to acid precipitation during the 1980s. During the early 1990s a decrease in acidic deposition resulted in slight improvement of water quality of the lake. This was followed by recovery of the reproduction of perch starting in 1991. A mark and recapture experiment in spring 1995 indicated a hundred fold increase in the population size of perch in a four year period. A decrease in the abundance of aquatic invertebrates was recorded during 1989– 1996. This decrease well coincided with the recovery of the perch population, suggesting that increased predation by fish was responsible for the decrease. The occurrence of goldeneye young also dropped in L. Vähä Valkjärvi since 1993. This was thought to be due to increased food competition with perch.

Since the early 1980s, the acidic deposition in the northern Europe has decreased substantially. This has resulted in corresponding improvements of the water quality in some acid sensitive small lakes of southern Finland. Among the fish of these lakes, the first signs of recovery were recorded in the early 1990s, when the European perch (Perca fluviatilis L.) started to reproduce in some sparse populations. Since then, the reproduction of perch has been successful in several years. The appearance of strong year-classes in lakes earlier almost empty of fish indicates recovery. This development has resulted in increased population densities, decreased mean sizes of fish and decreased growth rates. In a more acid sensitive species, roach (Rutilus rutilus (L.)), no clear indications of recovery have been recorded this far. However, schools of small roach (age 1+) were observed in the summer of 1998 in two acidic lakes that were inhabited by sparse roach populations during 1985–1995.

This paper deals with benthic invertebrate population responses to acidification and liming in the lower part of River Vikedal. In 1979 the river showed signs of increasing acidification. Highly sensitive invertebrates like the mayfly Baetis rhodani were present in the river in low abundance, but disappeared in the subsequent years. In order to re-establish a nontoxic water quality for fish, liming of the spring snowmelt to a minimum of pH 5.7 was started in 1987. During the later years liming has been successively increased. The invertebrate fauna showed a slow, but positive, response during the first years after liming, especially during autumn. B. rhodani recolonized the river in low density, but the spring cohort was still weak. Since 1994 the lime dosage was increased to secure a minimum pH of 6.3 during spring snowmelt. This has resulted in an overall increased biodiversity in the limed section of the river. Several acid-sensitive species, like both cohorts of B. rhodani and freshwater snails have colonized this part of the river. Simultaneously biodiversity in the unlimed reference sites has slightly improved during the last years. This is correlated with decreased sulphur deposition and improved surface water chemical conditions.

The sublittoral chironomid fauna of 22 lakes in Killarney Park, Ontario, Canada were examined for their response to different levels of acidification. Included in the analysis were naturally acidic lakes, lakes acidified by atmospheric deposition but now recovering, and unacidified circumneutral lakes. pH in the study lakes ranged from 4.6 to 7.7. No correlation was found between species richness and pH, nor between abundance and pH. Acid neutralizing capacity (ANC), the temperature at the sampling depth, pH, and dissolved organic carbon were the variables contributing significantly in a canonical correspondence analysis of the abundance data. ANC was the most important variable in describing the chironomid community, accounting for about 9 % of the variance in the species data. This study is the first step in an effort to model the changes in the chironomid community of recovering acidified lakes and the results suggest that ANC may be an important predictor variable.

The amphipod Gammarus lacustris was earlier a main food item of brown trout in Lake Svartavatnet at the Hardangervidda mountain plateau in South Norway. In the middle of the 1980’s, G. lacustris disappeared from the trout diet due to increased acidification. In order to preserve a unique genetic variant of brown trout living in the area, a liming programme was initiated in 1994. During the first years after liming, G. lacustris was absent both in fish stomachs and in lake littoral samples. In 1999, it reappeared in brown trout stomach samples together with two other strongly sensitive species, the tadpole shrimp Lepidurus arcticus and the freshwater gastropod Lymnaea peregra. Data from monitoring indicate that the water chemical conditions of L. Svartavatnet are still close to the critical limits of these animals. They have probably survived in small refuges of acceptable water quality, either in areas of inflowing groundwater or in the littoral, below the more acidic surface layer. The fact that these sensitive animals have not yet been found in benthic samples emphasise fish diet as an important tool in early registration of the presence/absence of invertebrates with low abundance or patchy distribution.

Studies in the 1980’s showed that there had been extensive loss of fish and invertebrates in lakes and streams in upland Wales due to acid deposition. A regional survey of these waters in 1995 showed that, despite large reductions in sulphur emissions, acidification was still widespread and no biological improvement was detectable. Policy options are needed which should include reductions in nitrogen as well as sulphur, the contribution of land use (especially conifer afforestation), liming and the introduction of species. This paper describes a screening study comprising the construction of an evaluation matrix, the use of decision workshops of expert stakeholders and trade-off analysis to identify possible combinations of options. The resulting output is being used to construct a regional strategy for achieving measurable ecosystem recovery within the next 10 years.

Critical loads (CLs) for soils and surface waters and their exceedances have been the basis for negotiations of emission reductions in Europe and elsewhere. In Sudbury, Canada, large reductions in sulphur emissions have resulted in reduced critical load exceedances of many lakes in the Killarney Provincial Park. To achieve a more complete chemical recovery even larger reductions of acid deposition are necessary. We extended the FAB (First-order Acidity Balance) model to include in-lake retention of nitrogen in upstream lakes and applied it to calculate CLs for Killarney lakes. Three different approaches were compared; one-lake, big-lake and lake-system. Use of “lake-system” resulted in the highest N retention and thus highest CLs, indicating that lakes at the end of chains are less sensitive to nitrogen deposition than calculated by the previous version of the model. Proper description of in-lake retention in such lake systems, as well as good data on catchment properties like land use and land cover, are important for CL-calculations used for the evaluation of future emission reduction policies.

In the regulated river Ekso, Western Norway, liming of the headwater has been introduced as a mitigating action to improve the water quality for Atlantic salmon (Salmo salar L.). Supply of lime from a dosing plant situated 5 km above the salmon producing part of the river, aims to raise pH from 5,0 to 6,5 during the smolt period for Atlantic salmon, and to 6,2 for the rest of the year. Hydrological modelling based on the relationship between CaCO₃ and pH is applied for the evaluation of the liming strategy, based on monitoring data from the spring 2000. The water quality demand was satisfied 80% of the time in the upper part of the salmon area, and 40% of the time in the lower part, influenced by power plant discharge. Flood forecasting and overdosing of lime ahead of floods will reduce the effects of acidified and unlimed tributaries. An additional lime doser is recommended to supply the power plant discharge.

The situation in northern Sweden did not figure prominently in the intense period of research during the 1980’s that laid the basis for many acidification-related policies now in effect in Europe and Sweden. Northern Sweden has not only relatively low acid deposition levels and significant sources of natural acidity, but also intense episodes of pH decline during spring flood that are a major focus of liming activity. Controversy over that liming and natural acidity has led to scientific advances. These include discovery of a correlation between sulfur in snow and the anthropogenic contribution to the subsequent spring flood ANC decline, but also that natural organic acidity is responsible for most of the spring pH decline in the region. This paper compares the developments in liming policy with the scientific developments of relevance to the region during the last decade. Considerable discrepancies are noted which create opportunities for revising remediation policies to better reflect the state of knowledge in 2000.

Sulphur deposition has diminished by about half during the last decade. For Sweden consistent estimates of total deposition are available for 1991, and 1994–97. Based on these estimates and using GIS the deposition for large drainage areas during one decade are calculated. These values are compared with the measured S transport in rivers covering about 85% of the Swedish territory, thus enabling the construction of a S budget for Sweden. The majority of the drainage areas have a net loss of S, which can be attributed to desorption of S in the soil. During the period of high deposition in the 1980:s (>60 meq m-2 yr-1 in southern Sweden) S was adsorbed, and retarded acidification. There still seems to be some S-adsorption in the northern parts of the country, where the deposition is less (now <20 meq m-2 yr-1).

Acid sensitive headwater lakes (n=163) throughout Finland have been monitored during autumn overturn between 1987–1998. Statistically significant decline in sulphate concentration is detected in 60 to 80 percent of the lakes, depending on the region. Median slope estimates are from-1.1 μeq L-1 in North Finland to-3.3 μeq L-1 in South Finland. The base cation (BC) concentrations are still declining especially in southern Finland (slope-2.5 μeq L-1), where every second lake exhibits a significant downward trend. The BC slope is steeper for lakes with less peatlands, more exposed bedrock, longer retention time and southerly location, but these factors are inter correlated. Gran alkalinity slope medians for the three regions range from 1.4 to 1.8 μeq L-1 yr-1 No significant negative alkalinity trends were detected. The similarity in the slopes of SO₄, BC and alkalinity in this data compared to seasonal sampling data from Nordic Countries can be regarded as indirect evidence that autumnal sampling is representative for long term monitoring for these ions. There are no indications of increased organic carbon in lakes, as found in some recent trend analyses of similar regional data sets. Although the processes behind the positive development in these lakes have to be revealed with site- specific intensive studies, this data suggests, that the initial recovery from lake acidification in Finland is a regional phenomenon.

Concentrations of sulphate in precipitation in southern Norway have decreased by 50– 60% from 1980–1999. This has caused a decrease in sulphate concentrations in lakes of 30–40% from 1986–1999. Nitrogen in precipitation has decreased slightly over the last 10-years. In lakewater there has also been a significant but slight decrease. Concentrations of non-marine base cations in precipitation have decreased by 40% from 1980–1999. In lakewater, non-marine base cation concentrations have been at about the same level the last 10 years. This indicates that acid deposition has decreased sufficiently such that the pool of exchangeable base cations in the soil is now being replenished. The acidification situation in lakes in Norway has thus shown a clear improvement over the last 8–10 years. pH, alkalinity and ANC (acid neutralising capacity) have all increased. Concentrations of inorganic (toxic) aluminium species have decreased. The trends in H+ and Aln+ do not follow the relation expected if Aln+ concentrations were governed solely by a single solid phase of A1(OH)₃.

A 38 ha near-barren experimental catchment area near an abandoned Cu and Ni smelter in Sudbury, Canada was treated with 410 tons of coarse dolomitic limestone in 1994. An additional 54 tons of pelletized fine dolomite were added to 15 wetlands within the experimental catchment in 1995. The treatments significantly increased the pH and base cation concentrations in the outlet stream. Cu and Ni concentrations initially rose after the wetland treatment, but then declined to levels below those of the reference site. Bioassay tests revealed that the toxicity of the drainage water was greatly reduced by the liming, but some localized inputs of highly toxic groundwater still posed a problem for aquatic biota. The pH of surface water in the wetlands has been maintained at >6.0 for over 4 years. The wetland liming appeared to be highly effective at neutralizing drainage water, however there may be some adverse effects on wetland plant communities as a consequence.

Precipitation, soils and soil water in a forested catchment in western Poland have been studied during the period 1992 – 96 (see also Vogt et al., this conf.). The S-deposition in the area during the study period was 2 – 3g S m-2 yr-1. In spite of decreasing anthropogenic emissions the S-deposition in the area did not change much during the study period mainly because the first years were exceptionally dry. However, the S-deposition was considerably higher during the previous decade. Based on soil water sulphate concentration, pH, acid neutralising capacity and the ratio of Al3+/(Ca2+ + Mg2+), there is apparently an amelioration in the conditions. A study using inter alia principal component analysis, indicates that this improvement is mainly due to more precipitation in the later part of the study period. Variations in precipitation amount have a pronounced effect on the soil-water chemistry, which makes it difficult to establish trends caused by changes in anthropogenic deposition. Long time series are therefore necessary to establish recovery due to reduced S-emissions.

In Chongqing City, the rapid growth of the economy has accompanied an increase of sulfur dioxide emissions from coal combustion, bringing about an expansion of acid rain affected areas and acidification of soil. Recently, we reported that coal-biomass briquettes so-called bio-briquettes (BB), which are produced from pulverized raw coal, biomass, and a sulfur fixation agent (Ca (OH)₂) under 3 to 5 tons cm-2 pressure, have high sulfur-fixation efficiency. The BB ash contains nutritive substances such as Ca and Mg, and has a large acid-neutralizing capacity. Thus, in order to improve the acid soil in the Chongqing area, we analyzed the chemical composition of the original acid soil and the ash-amended soil, and investigated their leaching characteristics under simulated acid rain (SAR). It was found that plants and crops in Chongqing area would be injured if the present acid rain continues. We carried out a SAR leaching experiment and studeid the potential toxic effects of leachate from soil containing added ash. The results indicated that the contents of most toxic elements, with the sole exception of chromium, were below the environment standard for irrigation water. Because the BB ash was highly alkaline, the leaching aluminum (Al) species would be hydroxide rather than free Al3+ ion.

The main results of the International Co-operative Programme on Effects on Materials, including Historic and Cultural Monuments (ICP Materials) within the United Nations Economic Commission for Europe (UN ECE) are summarised. The 8-year field exposure programme involves 39 test sites in 12 European countries and in the United States and Canada. Doseresponse functions (DRF) expressing the effect of dry and wet deposition as individual terms have been obtained for a wide range of materials including bronze, copper, weathering steel, zinc, aluminium, nickel, tin, stone materials, paint coatings and glass materials. The DRF’s includes parameters that are easily available on different geographical scales and can be used for mapping areas of increased corrosion rates and for calculation of costs.

Copper plates were exposed under shelters at 13 sampling sites in East Asia and their corrosion was analyzed. The corrosion products were first dissolved in water and then oxalic acid. Sulfate, nitrate and chloride in the solutions were measured by ion chromatography. The amounts of the three anions significantly differed depending on the atmospheric environment at the sites. Sulfate was a major part of the anions at Chongqing and Shanghai in China. Especially, at the urban sites in Japan, nitrate remarkably changed with the seasons, and often became the large anionic component in the summer. The amounts of chloride at most sites were at higher concentration levels compared with those at the rural sites in Japan. The anions in the copper corrosion must mainly reflect the impact of acid deposition.

Corrosion damage to materials including objects of cultural heritage due to acid deposition has been shown to cause large costs in several studies in Europe and in the United States. So far no similar extensive studies have been performed in developing countries. The World Bank has therefore initiated and financed a study of the corrosion costs in China based on available data in the literature and obtained through contacts and visits to several institutes and organisations in China. An initial assessment of the corrosion costs in China due to acidifying pollutants has been performed using a model originally developed and applied in Europe, which has been adapted to conditions in China. Here, the model is described using zinc as an example. In the calculation of corrosion costs it is assumed that the stock of materials at risk can be allocated to census data, which enables a separate calculation of the cost for each province in China. The significant differences in corrosion attack is illustrated for zinc with a corrosion map of China based on environmental data and a dose-response function adapted for Chinese conditions including the dry and wet acid deposition effects as separate terms.

In the Scandinavian countries, Norway and Sweden, increased weathering rate of cultural property such as rock carvings, mostly dated between 4200-500 BC, has become a serious problem. Observations during the last decades have shown severe deterioration due to a combination of natural and anthropogenic influences. In order to study the rate of weathering of the rock carvings an interdisciplinary group from Norway and Sweden was formed to carry out environmental monitoring on one site in each country, one of them belonging to the UNESCO World Heritage List. The results from this investigation have elucidated the problems concerning weathering of silicate rock surfaces and the different parameters causing the deterioration. Based on the obtained results some counter measures in order to preserve the rock carvings have been tested.

In the study the long-term exposure tests to simulated acid rain were performed in order to clarify the effect of acid rain on deterioration of concrete. Mortar specimens with 40 mm in width, 15 mm in thickness and 160 mm in length were used for the tests. At each time after the fixed rainfall was attained, those were tested physically and analyzed chemically. Finally total rainfall of 9000mm was given to the specimens. From the test results, it was confirmed that the eroded depth of the specimen has a good linear relation to the total rainfall under simulated acid rain with various pH. Surface erosion rates of the mortar specimens with an ordinary mix proportion under simulated acid rains with pH 3.0 and 2.5 were about 1.2 and three times larger than that under pH 5.6, respectively. It was also confirmed that flexural strength of the specimens with an ordinary mix proportion hardly changed under low pH simulated acid rain even after total rainfall of 9000mm was given.

Urushi (Japanese lacquer) plates were exposed to indoor air in 7 cities in East Asia from summer 1995 through winter 1997. The plates, collected every 3 months, were optically observed by using a gloss meter, a digital microscope and a microscopic infrared spectrophotometer for evaluation of seasonal impact by acidic air pollutants. The gloss losses were high on the urushi surface in autumn, when fog frequently appeared. Numerous fine spots were observed in 0.2–0.3 mm in diameter on the surfaces of the plates exposed at Chongqing, China, Taejon, Korea and Nara, Japan, where dense fog occurred. The spots were dark and opaque at Chongqing, where heavy air pollution was observed. A dark and opaque core was observed in each semitransparent spot at Taejon and Nara, while no spots were observed at Kyoto and Ishikawa, where fog often appeared but air pollution was at a low level. Carbonyl group, identified by microscopic infrared spectrometry, was found in the spots on the urushi surfaces. The carbonyl group may be formed by oxidation of a side-chain in urushiol (a major component of urushi sap, alkyl phenol). Urushi lacquer may be damaged by high concentration of sulfate anion, included in acid fog.

Major reductions in emissions of sulphur dioxide and nitrogen dioxide in Europe have significantly reduced the ambient concentrations of both sulphur dioxide, paniculate sulphate and nitrogen dioxide, as well as of sulphate in precipitation at Norwegian monitoring sites. In this study, trends in ambient air concentrations were studied in relation to air mass origin by sector analysis. Associated trends in ambient concentrations were derived by non-parametric statistical methods and evaluated on the basis of emission figures within the various sectors. The observed trends correspond well with reported trends in emissions.

Rainwater has been sampled weekly from five sites (nos. 1–5) in northeastern Vietnam in the period of May 1997 to Apr. 2000 (except Hoabinh site, from Aug. 1999 to Apr. 2000). Since Aug. 1999, weekly dry deposition samples including acidic gas and aerosol have been additionally collected at Hanoi (no. 4) and Hoabinh (no. 5) using filter pack system. In general, the pH in rainwater was frequently higher than 5.0. However, the trend of lower pH was observed during the winter and the beginning of autumn (from Nov. to Apr.). Interestingly, the highest frequency of the acidifying rainwater (32 %) and the lowest pH value (min. pH = 4.0) were observed in Hoabinh site. Acidic pH of rain water was also observed in Viettri (no. 3) and Hanoi (no. 4), indicating the local effects of human and industrial activities. Ca2+ and were generally found as predominant in both rainwater and aerosol. SO₂ and NH₃ in Hanoi and Hoabinh were monitored out of corresponding environmental features.

The results of ambient sulfur dioxide (SO₂) and nitrogen dioxide (NO₂) concentrations measured in ten cities of China and Korea by the improved passive samplers are reported. The property of this sampler is the utilization for the long-term exposure to the high level of SO₂ and NO₂. In this method, the conversion coefficients from the analytical data to the ambient concentrations were obtained from the comparison with the direct concentrations through the automatic analyzers for SO₂ and for NO₂, respectively. The interesting monthly variations were observed in the ambient SO₂ and NO₂ concentrations measured by this passive sampler method, which seems to give important information to the formation of acid rain in these countries.

The use of samplers for rainfall, throughfall, and stemflow was studied in Chamaecyparis obtusa forest in Kobe to develop a suitable simplified collection method for long-term monitoring of the effect of acid deposition on the forest ecosystem. A filtrating bulk sampler, widely used in Japan due to its convenience, was modified for rainfall- and throughfall-sampling. The pH value, and concns. did not change within a two-week sampling period, and the collection efficiency of the modified type relative to the wet/dry sampler was 97% (mean). The three samplers (shampoo-hat, vinyl chloride tube, and gauze type) were used for stemflow sampling. Collection efficiency of the samplers was in the order of shampoo-hat> vinyl chloride tube> gauze and that of the gauze type varied significantly with rainfall condition.

Fog water and precipitation were collected and analyzed to study fog and precipitation chemistry. The research was carried out through one year from April 1997 to March 1998 at Mt. Rokko in Kobe. Higher fog occurrence and larger volume of fog water were observed in summer, corresponding to the trend of seasonal variation in precipitation amount. The annual mean pH value of fog water (3.80) was lower by ca. one pH unit than that of precipitation (4.74). The concentration of chemical species in fog water was ca. 7 times that in precipitation. The highest anion and cation concentrations were and in fog water and Cl- and Na+ in precipitation, although the C1-/Na+ equivalent ratio in both fog water and precipitation was almost the same value as that in sea water. It is considered that in the longest fog event, and nss- in fog water mainly scavenged as (NH₄₂SO₄, mainly derived from (NH₄₂SO₄ (aerosol) in the atmosphere, NH₃ was scavenged at the growing stage, and SO₂ was also scavenged after the mature stage. in this fog event was mainly absorbed as HNO₃.

Nowadays, acid rain is generally noticed as a global environmental problem. While acid rain has very much to do with the air pollutants, the relation between air pollution and chemical constituents in precipitation is not understood clearly yet. It is important to measure a variation of ion concentration in precipitation in short term for understanding the formation mechanism of acid rain. Therefore, an automatic continuous measurement system of chemical constituents in precipitation was developed and put into practical use in this study. The developed system was able to collect automatically every lmm of precipitation and analyze major ions within 20 minutes.

Measurements of air and precipitation quality have been carried out within the EMEP programme under the Convention on Long Range Transboundary Air Pollution (LRTAP) since 1978. Approximately 100 rural sites are currently in operation. The Meteorological Synthesising Centre-West (MSC-W) operates two EMEP models estimating transboundary fluxes of air pollutants, a two-dimensional Lagrangian model and a three-dimensional Eulerian model. Traditionally kriging has been used to produce gridded concentration fields from observed data for comparison with modelled data. This paper describes a method for producing optimal fields based on both point measurements and. The difference between modelled and measured values in each measurement point is interpolated to give a smooth two-dimensional expression for the discrepancy between the two data sets. A combined map is derived by adjusting the modelled values with the interpolated difference weighted by the distance to the nearest measurement point. The method has been applied to sulphur and nitrogen measurements in air and precipitation from the EMEP network and modelled results in a 150x150 km grid from the EMEP Lagrangian model. The combined maps give improved regional concentration fields combining characteristics from both the measured and modelled data sets depending on the distance to the measurement points. Comparison with results from the higher resolution Eulerian model shows good agreement.

The Influence of acid deposition on stream and lake water chemistry was studied in a forested watershed of Hyogo prefecture, Japan. Monthly sampling of four streams, one artificial lake, and precipitation was carried out from 1995 to 2000. The pH of the monthly bulk precipitation and rainwater were ranged from 4.06 to 7.10. No trends were evident during the monitoring periods. The pH and alkalinity in the four streams, which flow into the artificial lake, ranged from 6.37 to 8.72 and 0.077 meqL-1 to 0.485 meqL-1, respectively. The differences in the water quality of the four streams were related to the geology of each watershed. Lower pH and alkalinity were observed during high- discharge periods. On the other hand, the pH and alkalinity of the outflow from the lake ranged from 6.47 to 7.36 and 0.195 meqL-1 to 0.339 meqL-1, respectively. No acidification of the aquatic environment was observed during the investigated periods. The results suggest that this forested ecosystem has the capacity to neutralize incoming acid deposition.

Acid Neutralising Capacity (ANC), calculated as the difference between base cations and acid anions, is widely used as a measure of freshwater acid status, and an indicator of biological conditions. Unlike pH and alkalinity, ANC is conservative with respect to CO₂ degassing and reactions with aluminium or organic species. However, since ANC is calculated as the residual of a large number of individual ion determinations, it is potentially sensitive even to relatively small analytical errors. For the Round Loch of Glenhead, SW Scotland, consistency of ANC estimation has been assessed based on a duplicate set of major ion analyses undertaken at different laboratories over an 11 year period. Results indicate that, while the two sets of individual ion determinations correspond well, correlation between calculated ANC values is poor. Consequently, estimated ANC trends exhibit severe discrepancies between datasets; one indicates substantial recovery, the other no apparent trend. These problems with ANC estimation are believed to be general to acidic waters and are of particular concern for long-term monitoring, where ANC changes may be small and difficult to detect (although nonetheless potentially biologically significant). In these situations, it is possible that a more stable measurement of ANC may be obtainable based on titration alkalinity, DOC and aluminium concentrations. Using this method, a small but highly consistent increase in ANC is observed over the study period, although much of this can be attributed to a shift from mineral to organic acidity, rather than an overall reduction in acidity.

The ozone concentration measurement results at two rural stations in Lithuania are presented. Ozone measurements have been carried out at the coastal site since 1980 and at the forested one since 1994. Both stations are far from the influence of the local pollution. The established ozone concentration trends at the coastal station were upward in cold and not so distinct in warm seasons during this monitoring time. The tendency even of a decreasing level in some summer months was established: in June and August. These trend results were very close to the results obtained at other European stations.Comparing ozone levels and courses at both stations, significant differences were determined. Clear differences between monthly daytime and daily ozone concentration averages are observed during the warm season. They were three times larger at a forest site as compared with the results at a coastal one.

The investigation of SO₂, NO₂,soot and benzo(a)pyrene (BP) has been performed at the background station on the eastern coast of the Baltic Sea since 1980. A significant decreasing trend has been observed for SO₂ and NO₂, while soot and BP concentrations were changing insignificantly. The decreasing SO₂ and NO₂ high concentrations ( >10μg·m-3) have been determined in the air masses coming from the Western and Central Europe to Lithuania since 1990. The concentration of SO₂ in a range of 0-5μg·m-3 and the concentration of NO₂ in a range of 0– 10μg·m-3 are characteric of the background atmospheric air.

Measurements of peroxide concentrations in fog water were conducted near the summit of Mt. Norikura (altitude, 2770m) in central Japan, and at the midslope of Mt. Oyama (altitude, 680m), southwest of the Kanto Plain. The concentrations of peroxide at Mt. Norikura, far from industrial regions, ranged from 3 to 120 μ M during the summer and early autumn in 1993. The potential capacity for SO₂ oxidation appears to be very high near the summit of Mt. Norikura. Analysis of the chemical composition of three-stage size-fractionated fog water samples collected at Mt. Norikura showed that the concentrations of peroxide were apparently independent of droplet size, whereas the concentrations of chemical constituents mainly derived from secondary aerosols and the acidity were higher in smaller droplets. Peroxide concentrations in fog water were low (< 5 MM) at Mt. Oyama, located near heavy industrial areas, and lower than those in rain water sampled simultaneously (0.2–33 μ M). Especially, peroxide was scarcely detected in strongly acidic fogs (< 0.2 μ M). Peroxide might have been decomposed by SO₂ (S(IV)) oxidation in the aqueous-phase.

In order to clarify the long-range transport of atmospheric pollutants in the East Asian regions, we have studied the components in rime ice on Yakushima Island, located in southwestern Japan near the China continent. The presence of a large number of particles has been found in the rime ice. Very small particles whose diameters are around in were identified as coal fly ash. The air mass at an altitude between 1500 m to 2000 m was probably long-range transported in association with a stable atmospheric layer in which the particles were efficiently scavenged by supercooled droplets. A back trajectory analysis also indicated the predominance of a north wind in the winter and in the other seasons as well. Such transport and deposition mechanisms may produce the greater pollutant deposition sometimes observed in mountain areas. Similar events may not be rare and could make an important contribution to the annual pollutants.

LAPAN has measured rain acidity in Bandung, the location is Cipedes since 1985, with average pH in 1985 was 6.25. The pH condition 1985–1999 as follow: The monthly average of pH in period 1985– 1992 was >5.6: in the middle of 1996–1997 it had big variation and than decrease until now. The monthly average of pH in 1997 until now was <5.6.The pH has decreasing trend, the reason was increasing fuel combustion for transportation and household because the area around the observation was change from rural to be transportation and settlement areaThe rain acidity comparison in Cipedes (rural site), Cicahuem (busy site), and Tanjungsari (remote site) hold in 1986–1987, the result was Tanjungsari the remote site had the lowest pH. It’s suggested the reason was sulphur compound from Kamojang crater and air pollution from industrial area in south-east of Bandung were blown by the wind through this place.The influence of air pollution to acid rain was studied by measurement and in 5 places around Bandung, the results were: North of Bandung had the lowest concentration because the traffics were low: but had the highest concentration; it’s caused by emission of sulphur compounds from Tangkuban Perahu Montain. South of Bandung had the highest concentration because the traffics were crowded and a lot of industries around it. In general Bandung had concentration higher than concentration, it’s suggested due to the influence of sulphur compound from Tangkuban Perahu Montain.The observation rain acidity in Ciater at Tangkuban Perahu Montain started in 1996, the result in period 1996–1998 as follow: The pH had decreasing trend, it’s due to the traffic near this observation increase, so the air pollution around this area increase, it will influence the rain acidity. The maximum monthly average of ph was 6.78 and minimum was 4.63, the pH monthly average generally < 6. In El NINO year 1997, the monthly average of pH in April and December were < 6.5.

Naturally occurring isotope systems, such as strontium and lead, are very useful for characterizing sources of pollution and producing background information. The phase-out of lead additives to gasoline in Northern Europe has for example not phased out the lead contamination of the environment. The stable lead isotope method shows the contribution from small local sources to the lead contamination of the Oslo air during a period when the combustion of gasoline, the major source of lead contamination, has been decreasing. Wood combustion for domestic heating is one of these polluting sources in Norway. Strontium analyses show that roadsalt from de-icing of a nearby road is accumulated in the soil surrounding an about 4500 year old rock carving. At rainfall this salt is re-dissolved and drained over the rock carving. The impact from the road is confirmed by lead isotopes. Lead and strontium analysis of teeth show the contribution from industry and traffic on todays humans and the differences in nutrient intake during the Medieval era are compared with today. The isotope signatures of the Medieval teeth also show that a person living along the coast can be distinguished easily from a person living in the central parts of the country, and that the Medieval individual mainly lived on locally produce, while the contemporary person to a great degree lives on industrially manufactured food.

Sequential leaching experiments using H₂O, H₂O₂, NH₄C1, and HC1 were performed on surface soils on an andesite substrate at four sites in the Kawakami mountainous area, central Japan. The solutions extracted from the dehydrated soil by H₂O, H₂O₂, and NH₄C1 have relatively constant ratios with respect to Ca, Mg, and Sr, while they have variable 87Sr/86Sr ratios depending on the site. The elemental ratios and Sr isotopes in the extracted solution are different from those of the soil minerals but identical to those of the soil solution and the plants. Sr isotopic data indicate that the residues after extraction from fine-grained minerals by NH₄C1 and HC1 are a mixture of acid-resistant minerals derived from bedrock and from arid areas in China. We suggest that there is a vital exchange of Sr and other cations between plants and the soil pool of exchangeable cations through the soil solution, while soil minerals, except chlorite, do not participate in the exchange reaction.

A cation-exchange high-performance liquid chromatography with high resolution inductively coupled plasma mass spectrometric detection (CE-HPLC/ICP-MS) was developed for the determination and the speciation of aluminum in environmental samples. Three types of aluminum species (Al3+) were separated from one another, and were determined with the present system. The comparison of the present system with an established CE-HPLC with fluorimetric detection using 5-sulfo-8-quinolinol (CE-HPLC/FL) was described. The present system showed better sensitivity for aluminum than CE-HPLC/FL. Moreover, the analytical results for soil extract and lake water samples obtained with both methods were in good agreement with each other.

A monitoring programme should be designed for duration. This means that methods should not only be appropriate with respect to detection limits and accuracy, but they should also be as simple as possible and they should be documented in such a way that measurements will be comparable over many decades. In this connection, it is particularly important to understand that results are dependent on methods, instruments and procedures. Within the European monitoring network (EMEP) there are several different sampling procedures for the main air components, SO₂, NO₂, + HNO₃, and co-located experiments have therefore been initiated to quantify the difference between the measurements. Reference methods and reference instruments corresponding to the recommendation in the EMEP Manual have been run together with the usual measurements at EMEP sites in several countries. The results are generally satisfactory, especially in the case where identical methods are used. However, there are also some unacceptable differences, e.g. when comparing NO₂ and SO₂ monitors with the reference methods. The monitors do have a main advantage of providing easily accessible data with short time resolution; nevertheless, the accuracy at low concentrations is usually poor. The traditional reference methods need development and simplification in the direction of the more appealing automatic instruments.

To determine the characteristics of single raindrops as a function of their size, the collodion film method was newly applied to the sampling of single raindrops. Sampling of single raindrops was performed at a height of 20 m above ground level of the Kyoto University building located in Uji, Japan during rain events from September to November 1999. It was possible to get successfully replicas of raindrop by collodion film method. And we tried to analyze the elemental components of the nuclei and pollutants that were incorporated into the developing raindrop. To the analysis of single raindrops, Particle Induced X-ray Emission (PIXE) was applied. Several elements including S in single raindrops were detected by PIXE. The concentrations of every element increased with decreasing drop diameter. Furthermore, to acquire more detailed information such as inner-structure and mixing state in single raindrops, micro-PIXE analysis was performed. The nucleation centers of single raindrops were successfully analyzed by micro-PIXE. Ca, S and Fe were apparently detected by scanning beam of 1 ~2 μm diameter and about 70 pA beam current.

The changes in ionic contents were studied in acidic precipitation samples collected for precipitation events in Taipei, which is near the sea. The storage cases under investigation include filtration, refrigeration, and light. Thus the experimental design leads all precipitation samples collected in the same rain event stored under different conditions. They were then analyzed six times successively within two months to provide the information containing potential ionic composition change. The measured constituents are H+, K+, Na+, Ca2+, Mg2+, and Cl-. The comparison of measured ionic concentrations corresponding to different storage methods yield no significant difference. The increases of and decreases of with time were observed to be of similar magnitude, while the variation of pH values is significant. The presented study indicated the important role played by sample storage in determining the ionic composition of precipitation samples.

Participating countries of the Acid Deposition Monitoring Network in East Asia (EANET) launched the preparatory-phase activities from April 1998. For the recognition and improvement of the analytical precision and accuracy, the Interim Network Center (INC) carried out the inter-laboratory comparison on the analysis of artificial rainwater samples and soil samples. Relevant laboratories submitted their analytical data to the INC for the evaluation. Submitted data were summarized and evaluated in terms of precision and accuracy, and were compared with the Data Quality Objectives (DQOs) of EANET. These inter-laboratory comparisons made clear the present conditions of laboratories as well as the major constraints that should be solved in the future.

Acidifying emissions from energy production and industry have decreased considerably during the last two decades in Finland. Especially the emissions of sulphur dioxide have dropped sharply with 85% in 1980-1998, although the energy use has increased 30% during the same period. The reduction has occurred through two mechanisms: by replacing the combustion of heavy fuel oil with cleaner energy carriers, and by direct emission reduction controls, e.g. flue gas desulphurization. In this study the Finnish cost curves for SO₂ and NO_x were first calculated to produce a consistent comprehensive view on further emission reduction costs and potentials. The data on technical and cost-related parameters were based on actual national experiences from power plants and industry. Most of the cost-efficient sulphur emission controls were already in use. For NO_x, a large share of further reduction potential still remained. Second, a case on the emission reductions and costs for fuel switching in a 205 MW_th peat power plant of Tampere Power Utility in Finland was studied. Fuel switching to natural gas was found less cost-efficient in SO₂ and NO_X emission reduction when compared to flue gas cleaning techniques. The findings provided new information on fuel switching as an alternative potential reduction measure, which is not considered in international assessments. Keywords: air, cost curves, emissions, fuel switching, reduction costs

Fine spatial-scale measurements of acidic deposition have been made over two time frames: 1987/1988 and 1999/2000. Over this period, dramatic reductions in precursor emissions have occurred. The two sets of data are compared in order to quantify deposition reductions. Orographic enhancement of wet deposition from the seeder-feeder mechanism is important in the UK at high-elevation sites such as these and the measurements were corrected for this process using a standard methodology. The data were also modelled using a simple long-term Lagrangian acid deposition model and comparisons made with both sets of observations at a resolution of 5 km _ 5 km. Future scenarios (2010) of emissions were modelled to examine the impact of UK and other European sources in order to determine optimal protection of ecosystems in this region.

It is mainly SO₂ that bring about acid rain in China. Changchun City, which is located in Northeast China, is a typical city that is polluted by SO₂ from coal combustion in winter. In winter, the daily mean concentration of atmospheric SO₂ is about 0.10mg/m3 and about 5 times as high as in summer, and the daily highest concentration usually appears in daybreak and nightfall. The monitored lowest pH value of rainwater was 4.8 in spring and the range of pH value of rain /snow was 5.2–6.0 in winter, 4.8–5.8 in spring, 5.4–6.4 in summer, 5.6–6.4 in autumn, and the annual mean pH value of rainfalls was 5.8 (1999–2000). Because the alkaline aerosol from soil, meteorological conditions etc., is unfavorable to acid rain formation, even though high SO₂ emission intensity existed in winter, the acid rain did not appear obviously. The aerosol character, climate conditions in Northeast China are important factors for the acid rain formation, although SO₂ emission is the original cause.

The extensive use of coal as an energy carrier in China has led to high deposition of sulfur in a large part of the country. In the southern part of China large areas receive acid deposition, while in the northern part of the country the acidity of the emissions is neutralized by alkaline dust from the desert areas. In this paper we demonstrate the importance of knowing the sources and deposition patterns of base cations when assessing the effects of changes in sulfur emissions. Regional-scale data of both sulfur and calcium deposition from modeling and monitoring are combined in order to demonstrate how the acidity of deposition in China has changed historically and may change in the future. The importance of base cation deposition is also demonstrated using the dynamic acidification model MAGIC with input data from an intensive monitoring site outside Guiyang. It is not known what fraction of the deposited base cations is of natural origin and anthropogenic origin, respectively. The relative source strength varies greatly between regions. Future effects of emission changes are highly dependent on the relative reduction in sulfur and base cation emissions.

The International Cooperative Programme on Integrated Monitoring (ICP IM) is part of the effects monitoring strategy of the UN/ECE Convention on Long-Range Transboundary Air Pollution. We calculated input-output budgets and trends of N and S compounds, base cations and hydrogen ions for 22 forested ICP IM catchments/plots across Europe. The site-specific trends were calculated for deposition and runoff water fluxes and concentrations using monthly data and non-parametric methods. The reduction in deposition of S and N compounds, caused by the new Gothenburg Protocol of the Convention, was estimated for the year 2010 using atmospheric transfer matrices and official emissions. Statistically significant downward trends of SO₄, NO₃ and NH₄ bulk deposition (fluxes or concentrations) were observed at 50% of the ICP IM sites. Implementation of the new UN/ECE emission reduction protocol will further decrease the deposition of S and N at the ICP IM sites in western and northwestern parts of Europe. Sites with higher N deposition and lower C/N-ratios clearly showed an increased risk of elevated N leaching. Decreasing SO₄ and base cation trends in output fluxes and/or concentrations of surface/soil water were commonly observed at the ICP IM sites. At several sites in Nordic countries decreasing NO₃ and H+ trends (increasing pH) were also observed. These results partly confirm the effective implementation of emission reduction policy in Europe. However, clear responses were not observed at all sites, showing that recovery at many sensitive sites can be slow and that the response at individual sites may vary greatly.

In recent years, acid rain has been a social problem all over the world. In Japan, it is also a big problem especially in the metropolitan area. Then, we have measured major ions such as H+, Na+, K+, Mg2+, Ca2+, Cl-, and in precipitation and dry deposition samples which had been collected at 9 sampling sites at Hiyoshi, Mita, Kashiwa, Shiki, Fujisawa, Yokosuka, Mitaka, Hachiouji, and Ashikaga in Tokyo Metropolitan area for 10 years since 1990. The average pH of precipitation in their sites was 4.56 (n=1906). As the results of multiple regression analysis showed that pH of precipitation was determined by 5 ions such as, nssCa2+(non sea salt calcium), nssCl(non sea salt chloride), (non sea salt sulfate) in the most of the sampling sites. Therefore, it is very important to investigate the behavior of these ions to understand the acidification of rain in Tokyo Metropolitan area. In this study, a long term trend of each ion concentration in precipitation and wet deposition was also investigated the base on the data we had observed at 7 sites for 10 years by the statistical method.

Abashiri is a rural city on Hokkaido Island, Japan. It lies directly to the south of the Okhotsk Sea, which is the lowest latitude sea to freeze. We collected daily deposition samples over two periods: from Jan. 1997 to Mar. 1998, and from Nov. 1998 to Mar. 1999. The average concentrations of anthropogenic chemical species (non-seasalt(nss)-) were relatively low and those of seasalt species (Na+, Cl-, Mg2+) were high Japanese precipitation samples. During the period of study, we found that, when sea ice forms and approaches the coast, concentrations of seasalt species become lower, while almost no changes are found in the anthropogenic chemical species.

Long-term study on acid precipitation monitoring at suburban forests in Sapporo city showed that bulk precipitation pH were below 4.8 in recent years. Throughfall and stemflow chemistry for two main coniferous species (Abies sachalinensis and Picea jezoensis) showed different regime for pH and element deposition. The mean annual pH values of throughfall and stemflow in Picea stand were 1.0 to 1.3 units higher than that of rain collected outside the forest. In contrast, mean annual pH of throughfall and stemflow in Abies stand were 0.3 to 0.5 units higher than that of rain. Mean annual inorganic nitrogen input via throughfall and stemflow were estimated 0.41 ± 0.11 gN/m2/yr in Abies stand, 0.44 ± 0.13 gN/m2/yr in Picea stand. Cation input via throughfall, especially for K, in Picea stand was 1.4 times as large as that in Abies stand. Mean annual input of S in both stands was the same level. The possible effects on surface soil properties and nutrient cycling in northern evergreen conifers was discussed.

Aerosol and precipitation samples were obtained at the summit of Mt. Fuji, the highest peak (3776m a.s.l.) in Japan, in the summers of 1997, 1998, and 1999. The mountaintop might be affected by valley wind during the afternoon, but is located in the free troposphere during the morning. The temporal variations of chemical species in the aerosol and precipitation samples correspond with meteorological conditions. The in the aerosol and precipitation exhibits high concentration with low temperature air mass, indicating the influence of long range transport from the Asian Continent. The contribution of the free troposphere to the chemical species obtained at the summit is estimated to be at least 30% during the summer season.

The geographical and temporal variations of chemical constituents in winter precipitation collected in the areas along the coast of the Sea of Japan (AASJ) were discussed by analyzing the data obtained in the 1st and 2nd National Add Deposition Survey by Japan Environmental Laboratories Associatioa In western Tohoku (WT) and Hokuriku (HR) areas in AASJ, in spite of large amounts of precipitation in winter; concentrations of non sea salt (nss-) are not as low as the other areas, and nss in these areas is lower than the other areas. As a result, FT concentrations of precipitation in these areas are somewhat higher than other areas. From the temporal analysis of daily sampled data and back trajectory analysis of air mass, it was found that the concentrations of nss-, and nss- are correlatively varied when air mass come from the Asian Continent, showing higher concentrations at the western sites in AASJ and depending on the meteorological conditions such as the direction of in flow air mass.

The following measurements were carried out to clarify acid deposition in Niigata Prefecture, an area facing to the Sea of Japan. 1) Acid deposition fluxes and sulfur isotopic ratios of atmospheric deposition were measured at 9 sites in the prefecture in 1999. 2) Atmospheric deposition was collected daily at one site in 1997, to measure the sulfur isotopic variations of sulfate together with the air mass trajectory for each deposition. It became clear that: (a) The major component that acidifies atmospheric deposition is sulfuric acid (b) Sulfate deposition increases in winter in the whole study area, (c) The sulfur isotopic ratios indicate that sulfur dioxide emitted from China affects the whole study area in winter, (d) Winter deposition of sulfate estimated to derive from coal combustion in China account for half of nss-sulfate deposition in average at 9 sites.

Increased industrialization and urbanization lead to the atmospheric acidity which causes acid rain. However, in India, the nature of rain water has been observed to be alkaline. The reason for alkaline nature of rain water is found to be the buffering of acidity by soil-derived aerosols which are rich in Ca. Over the Indian Ocean where concentrations of soil dust are negligible, the acid rain has been observed to be a common phenomenon during INDOEX campaigns. In the Indian subcontinent, observations have indicated that rain becomes acidic when the buffering potential of rain water is weak. The weak buffering potential may be due to less interference of soil dust, acidic nature of soil or very high influence of industrial source.

The application of a new, spatial nitrogen leaching/retention model NEXRET to the Oulujoki river basin (22800 km2) in Finland is discussed. The model utilizes remote sensing-based land use and forest classification and evaluated export coefficients obtained from detailed small catchment studies. The present and future N depositions were estimated with the regional deposition model DAIQUIRI. Based on source apportionment, N deposition, forestry and agriculture each contribute 16–17% of the total export, with pronounced variation between the different sub-basins. The effect of changing forestry and deposition on N fluxes is assessed by using N deposition scenarios based on recent international emission reduction agreements.

Thirteen streams in the province of Jämtland in northern Sweden were monitored during spring in 1995 (December 94 — July 95) to study changes in water chemistry and metal concentrations during snow melt. The brooks are not treated with lime, with one exception, and can be approximately divided into three groups according to watershed characteristics; A) > 65% above tree line, B) > 65 % wetland, C) > 55% forested. During peak flow, pH dropped 0.5–2.5 units and alkalinity generally to zero. The brooks above tree line were lowest in base cations and reached the lowest pH-values (4.4–4.6) during peak flow, while sulphate levels were about the same as in the forested watersheds. During peak flow, organic anions showed the highest increase in the wetland and forested catchments. Compared to base flow, Al, Zn, Pb and to some extent Mn was enriched during peak flow. The results also illustrate the difficulties in generalising the reasons for alkalinity losses during spring flood in this kind of streams. In some of the brooks, the use of either base cations or silica, when calculating dilution effects, gave deviating results concerning the relative contribution of strong acids in the snow pack.

The concentrations of major ions and spheroidal carbonaceous fly-ash particles (SCPs) in bulk deposition were determined in weekly samples from six European mountain lakes during 1997/98. SCPs are produced only from high temperature combustion of fossil-fuels and therefore provide an unambiguous indicator of atmospheric deposition from this source. Positive correlations were observed between SCPs and and at all sites except for some determinands at Jorisee (Switzerland) and Starolesnienske (Slovakia). Correlations between SCPs and were always more positive than for SCPs with ‘total acid ions’. This is in agreement with the expectation that the contribution to deposition made by fossil-fuels is negligible. Good positive correlations between SCPs and all acid anions were observed at Estany Redo (Pyrenees); lower but still positive correlations were observed for all acid ions with SCPs at Gossenköllesee (Austria), Lochnagar and Kørvatn (central Norway), whilst little trend in correlation was observed for Jorisee and Starolesnienske. It is suggested that this gradient reflects the influence of fossil-fuels on acid deposition in these areas. A high positive correlation was observed between SCP and Cl-1 at Gossenköllesee possibly as a result of HC1 from coal combustion.

We found that river water is acidified not only in the first stage but also in the later stage of the snowmelt season in Japan, which differs from the so called acid shock occurring in the first stage of the snowmelt in the northern Europe. The acid shocks depend on the regional characteristics of the melt-refreeze processes forming the internal distribution of acid materials within snow crystals under the warm metamorphism. In a warm climatic region like the central Japan, there are possibilities to have the complicated distribution structure of acid materials within granular-snow crystals due to the repeated melt-refreeze processes even in midwinter. Consequently, the pH value of meltwater does not always increase as the snowmelt proceeds. Then, we showed the possibility by using the X-ray computed tomography that the domains with the acid materials exist in the inner parts of snow crystals. So, the acidification of the river water may occur even in the later stage of the snowmelt

Stream waters were sampled weekly during spring and monthly during summer and autumn in 1998. The streams are more or less acidified, and some have been treated with lime. The aluminium fractions (total monomeric Al, organic monomeric Al, inorganic monomeric Al) were determined colourimetrically with pyrocatechol violet combined with cation exchange using Continuous Flow Analysis (Autoanalyzer I). The levels of inorganic monomeric aluminium varied substantially, between <3 to 271 μg/1. The levels were higher in untreated than in limed waters and twice as high in the most humic waters as in less humic waters. The importance of aluminium mobilisation from the catchments was obvious, with higher aluminium concentrations in surface runoff (unbalanced stream waters) compared to lake outlets (balanced and precipitated lake water). The highest mean levels were measured at spring, whereas the highest single peaks occurred during summer. Inorganic monomeric and total monomeric aluminium was best correlated to ion ratio and pH whereas acid soluble aluminium and organic monomeric aluminium was best correlated to TOC, water colour and iron.

Industrial development has increased fast in China the last decades. This has led to a range of environmental problems. Deposition of heavy metals to forest ecosystems via the atmosphere is one potential problem. In this paper we report results from a pilot study where the heavy metal levels in forest soils at four different sites have been measured. Three of the sites are located relatively close to the large cities Chongqing, Guiyang and Guangzhou; one site is located in a remote, mountainous area in Guizhou province. Total metal contents as well as fractions according to Tessier’s scheme were determined. With a few exceptions, the metal concentrations can be characterized as low; i.e. in most cases within the range of what has been reported as typical background values in the literature. High content of arsenic (up to 100 ppm) was found in the samples from the site outside Guangzhou, most likely due to naturally high arsenic levels in the soil. Metals bound to organic matter and to iron- and manganese oxides were the dominant fractions. No clear differences in metal levels were found between topsoil and subsoil samples, indicating that the atmospheric deposition of heavy metals has been low.

The aim of this study was to evaluate qualitatively as well as quantitatively the response of typical soils of the Wielkopolski National Park to simulated acid rain. The experiments with simulated acid precipitation were performed on soil monoliths of unchanged structure. The artificial rain used for the simulations was diluted sulphuric acid of pH 2.0, 3.0 and for the control experiments distilled water was used. Changes in the soil pH and Ca/Al molar ratio of specified soil genetic horizons were described. A quantitative description of the leaching dynamics of calcium, magnesium, sodium, potassium and aluminium, dependent on the kind of sprinkling was given. The results proved that simulated acid rain washed out significant amounts of nutrients and released toxic amounts of aluminium. Humus and clay fraction colloids were noted to have a buffer effect.

Chongqing is among the heaviest polluted cities in China Combustion of coal with relatively high sulfur content causes high sulfur emission and deposition in the area. Effects on soils and waters of the acid deposition in the Chongqing area have been studied in the field at a forested site outside the city. Deposition chemistry and fluxes, soil and soil water chemistry as well as surface water chemistry are presented for the period 1996–1998. There are some stress symptoms at the forest in the area and severe forest damage has been reported at Nanshan, closer to Chongqing center. Monitoring of the acidification situation in the area must be followed closely as impacts may be expected if the deposition is not reduced in the future.The deposition of sulfur, H+ as well as calcium at the site is high. Wet deposition of sulfur is estimated to 4.7 – 5.7 g S m-2 yr-1 during the three years sampled; dry deposition is probably of similar size. Annual volume-weighted pH in bulk deposition was 4.0 – 4.2 and the calcium wet deposition flux was 2.6 – 3.6 g Ca2+ m-2. There are considerable seasonal variations in the concentrations, related to the seasonal variations in precipitation amount (dry winter, wet summer). The soils at the site are acid with median base saturation of 12% and 8% in the topsoil and subsoil, respectively. In soil water, aluminum concentrations are typically in the range 3–8 mg L-1. However, due to the high base cation deposition, the Al/(Ca2++Mg2+) molar ratio is below unity in most samples, indicating little damage of forest due to aluminum in soil water.

Impacts of air pollutants and especially acidification in ecosystems have been of serious concern in the Nordic countries since the 1970s. The current approach to assess several pollutants (sulfur and nitrogen oxides, ammonia, volatile organic compounds) and their effects (acidification, eutrophication and ground-level ozone) simultaneously is extremely complex. This study explored the relative role of nitrogen oxides in environmental impacts in the Nordic countries. The share of NO_X in the exceedances of critical loads, the long-term ecosystem protection targets, was found to be roughly 25% in acidification and 50% in eutrophication. The contribution of NO_X emissions to ground-level ozone formation was considered important, as NO_X is the limiting precursor in ozone formation in the Nordic countries. The comparison of observed and modeled accumulated ozone concentrations (AOT40) for the early 1990s shows noticeable differences in the Nordic area, partly due to the sensitivity of the AOT40 indicator to the 40 ppb threshold value.

The Swedish liming programme was initiated in 1977 to counteract the effects of anthropogenic acidification on aquatic ecosystems until the acid deposition has been reduced. Ecosystem development in limed waters has been followed since 1989 in a programme for integrated studies of the effects of liming acidified waters (ISELAW). The main objectives are to assess a) the long-term ecological effects of liming, b) to what extent ecosystems recover to a pre-acidification state, and c) to elucidate possible detrimental effects of lime treatment. The programme comprises monitoring of water chemistry, phyto- and Zooplankton, vegetation, ben-thic invertebrates and fish in 13 limed and 5 non-limed lakes, and 12 limed and 10 non-limed streams. Paleolimnological studies are performed to reveal pre-acidification lake history. The results show that lime treatment detoxifies the water, although chemical and biological development varies among and within sites. In general the long-term changes are small compared to the initial changes associated with first treatment. Water chemical changes over time are reflected as reduced sulfur concentrations and increased nitrogen concentrations. Treated ecosystems seem not to recover fully to the situation before acidification, and due to re-colonization failure, several species are lacking in the limed waters.

Semi-quantitative biomass-size distributions (BSD’s) along a joint axis of individual size provided an integrated illustration of aquatic communities sampled at different taxonomic and trophic levels. The approach was applied within the Swedish ISELAW-programme (integrated studies of the effects of liming acidified waters) to test the general hypothesis that aquatic communities in limed lakes are not systematically different from communities in comparable non-limed circumneutral lakes. Input data included pelagic phytoplankton and Zooplankton, sublittoral/profundal macroinvertebrates, and benthic fish, within twelve Swedish lakes (six limed, two acidic and four circumneutral reference lakes). The four compartments were sampled on different spatial scales, but each designed for between-lakes comparisons. There were no clear-cut differences in overall size distribution between the three categories of lakes. The mean BSD of limed lakes was indeed more similar to the mean BSD of circumneutral lakes than to that of two acidic lakes. Due to high variation within categories, however, acidification status alone can not be used for reliable prediction of BSD in a certain lake.

Metals in water have been monitored for up to 18 years in acidified regions of Sweden. The concentrations of metals (Al, Cd, Cu, Fe, Mn, Mo, Pb, Zn) were determined by AAS and ICP-MS, the dissolved fractions after separation by in-situ dialysis. Elements showing negative pH-correlation were primarily Al, Zn, Cd, Mn, and Pb, while Mo was positively correlated to pH, indicating a predominance of negatively charged ionic forms. Zn, Cd, and Mn occurred primarily in the dissolved fractions, especially at the lower pH levels. Fe, Al, Pb and Mn were further enriched in humic waters. During the study period, some of the sites were subject to lime treatment, which had a marked influence on most elements, causing the mean levels and the seasonal fluctuations to decrease. Treatment on the lake surface was less effective than wetland liming to reduce seasonal fluctuations, especially for metals mainly originating from the catchments, as Fe and Al.

Water chemistry and plankton has been monitored in three Lakes in Tyresta National park SE of Stockholm since 1977. Liming operations started in Lake Langsjön and Lake Trehörningen in 1978 and were repeated every 3–5 years, while Lake Årsjön is an unlimed reference Lake. During 1991–1999, the annual pH median in Lake Langsjön and Lake Årsjön ranged between 6.6–7.1 and 5.2–5.8, respectively, and the composition of phyto- and Zooplankton in these lakes did not change markedly. After a final treatment in 1991, the liming of Lake Trehörningen was terminated intentionally. As a result, pH decreased from an annual median 7.1 in 1991, to 6.1 in 1999 (5.8 in 1998). Total organic carbon (TOC) did not change markedly during this period, while the levels of calcium decreased. Metals, known to be influenced by acidification, especially cadmium, manganese and aluminium (Al), increased. The labileinorganic forms of Al also reached higher levels, especially in 1998. Following the decreasing pH, the total number of phytoplankton taxa decreased by ca 40%. Among Zooplankton, the cladocerans Holopedium gibberum, Diaphanosoma brachyurum and Daphnia longispina, common during the limed period, became rare.

Ecosystem development in lime-treated waters in Sweden has been followed since 1989 in a programme for integrated studies of the effects of liming acidified waters (ISELAW). Observations after prolonged liming (>10 y) indicate a phosphorus depletion in the limed lakes which contrasts to the increased phosphorus supply often following within the initial years after lime treatment. After prolonged liming, the levels of total phosphorus are lower as compared to neutral reference lakes at identical TOC, and the phosphorus/TOC-ratio is consequently lower in limed lakes. Depletion of dissolved inorganic nitrogen during the summer is also lower in limed as compared to neutral reference lakes. Phytoplankton biomass and species number also lower in the limed lakes as compared to unlimed neutral references. Furthermore the bacterial number per unit TOC is lower in the long term limed lakes, possibly as a result of phosphorus limitation. As to the higher trophic levels, the benthic soft-bottom fauna of limed lakes (specifically the sublittoral fauna) is poorer in terms of species diversity and abundance. Also fish community composition indicates lower productivity in the limed lakes. Taken together there is thus evidence that the long term limed lakes have a lower trophic level than reference lakes.

Atmospheric sulfur oxides, participate matter and deposits (wet and dry deposits) were collected from July 1998 to June 1999 at Kyushu Island, Japan. The isotopic composition of sulfur (δ34S) was measured to identify the source of sulfur in the samples. The monthly δ34S values were always low in the order of the sulfur oxides, sulfate in particulate matter and deposits. The δ34S values of the sulfur oxides ranged from-2.7 % to-0.4 % and were close to those of fossil fuels used in Japan. The δ34S values of sulfate in the particulate matter and deposits correlated with seasalt contribution, so that the δ34Snss value was calculated for non-seasalt sulfate. The δ34Snss values of sulfate in the particulate matter and deposits trended higher in winter than summer, suggesting the possibility of isotopic fractionation during chemical transformation (SO₂ to) and of contribution of sulfate derived from sulfur sources with higher δ34S values.

The paper gives a general description of a numerical regional-scale air quality forecast model, with emphasis on solution schemes for all possible processes (emissions, transport, deposition, chemistry, and initial boundary conditions) considered in the Eulerian transport/deposition model. In order to improve forecast efficiency we first introduce a looking-up table method for treatment of NO_X and ozone chemical processes instead of the coupling method. Meteorological field is forecasted by the Eta model, which is driven by NCEP data. Several-week regional-scale air quality in China is forecasted using the numerical model system. Comparison and analysis indicate that the air quality levels of key cities over China and the time evolution of pollutants over most places of China can well be forecasted by the numerical model system. Further improvements in some important aspects are needed and presented.

Atmospheric air pollution levels and long-term effects on the environment caused by simultaneous presence of SO₂ and oil shale alkaline fly ash during the last five decades (since 1950) were investigated. The annual critical value of SO₂ for forest (20 μg m-3) was surpassed in 1% (~35 km2) of the study area where the load was 30–40 μg m-3. No effect of long-term SO₂ concentrations of up to 10–11 μg m-3 (0.5-h max up to 270 μg m-3) and simultaneous fly ash loads of up to 95 μg m-3 (1000 μg m-3) on the growth and needle longevity of Pinus sylvestris was established. The yearly deposition (average load up to 20–100 kg S ha-1) was alkaline rather than acidic due to an elevated base cation deposition in 1960–1989. Since 1990, the proportion of SO₂ in the balance of components increased: about 70–85% of the total area was affected while the ratio of annual average concentrations of SO₂ to fly ash was over 1. The limit values of fly ash for Sphagnum mosses and conifers in the presence of SO₂ are recommended.

Observations of air pollutants were conducted at Chengshantu in January 1996 to clarify the extent of trans-boundary pollution from the Asian continent. A nested air quality prediction modeling system (NAQPMS), which included parameters on emission, transport, diffusion, deposition and transformation of sulfur oxides, was performed to compile sulfur concentrations over the observation site. The model calculation reproduced the observed variations of sulfur oxides and sulfate well, although the model calculations could not reproduce the extensively low sulfate concentrations. Using nesting improves the ability of the modeling system to capture peak episodes seen in the observations. Calculation of the origins of deposited sulfur in each country with the NAQPMS shows that the long-range transport of sulfur is very serious. For Japan, 49% of sulfur deposition was from other countries during the campaign period.

Health effects of air pollution in Asia have been assessed as part of a programme on Regional Air Pollution in Developing Countries. The impacts of air pollution on health have been studied in North America and Europe for many decades, but research on effects on health in developing countries is less advanced. A key question is whether the dose-response models that are based on research conducted in developed countries can be applied to exposures to air pollution in developing countries. The study considered this issue and examined the factors that may lead to either increased sensitivity or increased human tolerance of air pollutants. It is suggested that although there are factors in developing countries that may increase or decrease human sensitivity to air pollution, overall, a similar range of sensitivity can be expected by individuals in these countries responding to the same effective dose as those in developed countries.

The ambient concentration of SO₂, NOx and O_x in the atmosphere of Hiroshima, Fukuyama and Fuchu city which were monitored by the prefectural monitoring stations, are examined to give a picture of the typical air pollution at these sites. Results show that the yearly concentrations of SO₂ in these areas are significantly fall from 20 to 6 ppb during 1978 –1996 when the NOx concentrations having no such significant change which varies from 40 to 30 ppb. The Photochemical Oxidant (Ox) increases annually at the rate of 0.3 ppb to 0.6 ppb in Hiroshima city only. To know the present situation of air pollution the Differential Optical Absorption Spectroscopy (DOAS) system is used in the city of Higashi Hiroshima. The daily average concentrations of SO₂ NO₂, O₃ and HONO measured during the period of August 1999 to March 2000 ranged from 1.4 ppb to 2.8 ppb, 13 ppb to 26.9 ppb, 21 ppb to 53. 6 ppb and 1 ppb to 4.3 ppb respectively. The patterns of concentrations of NO₂ and O₃ measured by DOAS look similar to the seasonal patterns of NOx and Ox by the conventional system.

The acute effects of air pollution on human health and the environment are well understood and the arguments for measures to prevent local, gross pollution are strong. Governments and the public will accept the need for controls where effects are obvious. At the broader scale where effects may be more subtle, and where the costs of abatement are high, a convincing case is necessary before acceptable solutions are adopted An education process is needed to provide the relevant facts in an understandable form. For major air pollutants, where international agreement for control of emissions is required, effect-based instruments have proved successful in Europe. These are designed to be cost effective by offering protection to the more sensitive areas by targeting the cheapest emission controls on the sources responsible for effects. This level of complexity has demanded improved education and communication for ail those involved in the decision-making process. The principles and approaches that have provided success are discussed Attention to these is needed in the future if more stringent and costlier measures are to be agreed.

Countries that will ratify the new Protocol to abate acidification, eutrophication and ground-level ozone, also known as the Göteborg-protocol, are committed to meet national emission ceilings for SO₂, NOx, VOCs and NH₃ in 2010. AEA Technology calculated impacts and monetised benefits for four scenarios used during the preparation of the new Protocol, each scenario compared with the situation 1990. The calculated benefits were compared with the costs calculated by the International Institute for Applied Systems Analysis (IIASA) using the RAINS model. The overall conclusion is that the benefits are likely to exceed the costs of implementing the scenarios considered in the study, by a factor of between two and three. Based on the principal set of assumptions followed in the study, it appeared that impacts on haity and materials were negligible. Impacts on ecosystems remained unqualified.

Long-range tropospheric transport of acidic and non-acidic contaminants into or across the Pacific Ocean from sources originating in Pacific Rim countries and beyond (trans-Pacific air pollution, for short) is an emerging international environmental issue. This paper provides a definition of trans-Pacific air pollution; summarizes some of the scientific evidence for what seems to be the dominant pollutant pathway in the Asia-Pacific region, transport on westerly winds from Asia to North America; discusses a recent conference on trans-Pacific air pollution; and analyzes some of the political implications of the problem. Evidence for trans-Pacific air pollution comes from three main sources: observational data, computer simulations, and research on concentrations of pollutants in various media. Trans-Pacific air pollution is of political consequence. There may be wide-ranging physical and chemical effects if the relatively pristine air of the Pacific troposphere is altered. Domestic air quality along the west coast of North America may be altered. Degradation of the Arctic environment may be accelerated. The issue reinforces the need for greater international cooperation on environmental issues in the Asia-Pacific region.

Integrated assessment models were applied to analyze the side-benefits of structural changes in the energy systems of Finland and the EU to reduce acidity critical load exceedances in Finland. The acidification reduction potential of structural measures, induced by the need to restrict carbon dioxide (CO₂) emissions, was compared with international agreements limiting acidifying emissions. The impacts of the UN/ECE Gothenburg protocol and the European Commission’s proposal for a National Emission Ceilings (NEC) Directive were assessed together with domestic and bilateral policy scenarios. The study utilized point-source emission databases of Finland and the neighboring areas and a meso-scale deposition model together with the Europe-wide transfer matrices of the EMEP/MSC-W and European emission scenarios of IIASA. Further technical reduction measures in the adjacent large sulfur emission sources in Russia would reduce considerably deposition to nearby Finnish areas. Energy saving and shifts in the EU energy system towards less carbon-intensive fuels instead of further technical emission controls were found to have significant potential in limiting acidifying deposition. Implementation of the Kyoto protocol in the EU could reduce the Finnish areas at risk of acidification more than the Gothenburg protocol and the NEC Directive together.

Several multilateral initiatives on acid rain control were advocated in the 1990s, and extended through multiple channels in East Asia There is, however, little coordination between those initiatives. The geopolitical make-up of the region has also hampered further progress in regional cooperation on the issue.In this paper we first examine the major features and weaknesses of existing regional environmental cooperative schemes. Second, we review collective initiatives on the acid rain issue, and examine how further progress has been hindered by the inherent inadequacies of the schemes. Finally, we consider whether and how regional cooperation on the acid rain issue may be promoted, and try to draw some implications from the European experience that might help enhance regional cooperation.

We analyze the history of acid rain in China over the last three decades in the light of the relationship between China and Japan. China has been aware of the problem of acid rain and has been conducting scientific research since the late 1970s. However, little effort has been put into practical countermeasures. In the early 1990s, acid rain was re-evaluated as an international environmental problem. Meanwhile, Japan became concerned about trans-boundary air pollution from China What is important is that Japan’s concern strongly influences China’s acid rain policy. In the context of growing international concern for environmental problems, China has taken remarkable steps to control acid rain. In this respect, dealing with acid rain is an issue of national pride for China

15 years ago an interim report for an intense environmental program was compiled concerning the location of the islands of Japan at the meteorological down stream of the East Asian Countries. Parts of sulfur dioxide and other air pollutants, those supposed to cause acid deposition are emitted from the eastern parts of the Asian continent, especially in China. The air pollutants flow down to the east to spread over these islands. This acid deposition is projected to cause damage to forest resources of Japan in the future by increasing air pollutants emanating from the continent. A long term project by a research group at Keio University commenced in 1985 to identify ways of preventing this damage to the forests. The group formed the JACK Air Surveillance Network in China and South Korea in order to collect the first precise air pollution data in this region, as well as to identify a reliable partner for the project. On the completion of the JACK project, a highly cooperative group was formed between the researchers of Keio University and those in Chengdu, Sichuan province of China and has effectively worked since 1991. The goal of the project is the formation of an Inland Environmental Information Center in inland China to be accomplished by 2005. To launch a 10 year project by the center, a nation wide campaign is planned to raise the awareness of the population, specifically the lower socio-economic group on the effect of environmental issues. It is suggested that this education campaign take effect in inland China no later than 2025 for the preservation of the forests on the Islands of Japan.