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"Molecular Environmental Soil Science at the Interfaces in the Earth's Critical Zone" presents contributions from the 1st International Symposium of Molecular Environmental Soil Science at the Interfaces in the Earth's Critical Zone held in Hangzhou, China. It introduces new ideas, findings, methods, and experience on above new and emerging subject areas. A broad range of topics are covered: the role of mineral colloids in carbon turnover and sequestration and the impact on climate change, biogeochemical interfacial reactions and dynamics of vital and toxic elements, ecotoxicology of anthropogenic organics, environmental nanoparticles and their impacts, and ecosystem health. The book will be a valuable reference for researchers in soil chemistry, environmental chemistry, mineralogy, microbiology, ecology, ecotoxicology, and physics.

Jianming Xu is a Professor at the Institute of Soil and Water Resources and Environmental Science, Zhejiang University, China. Pan Ming Huang is a Professor at the Department of Soil Science, University of Saskatchewan, Canada.

Inhaltsverzeichnis

Frontmatter

Plenary Lectures by IUPAC Scientists

Frontmatter

Advances in the Use of Synchrotron Radiation to Elucidate Environmental Interfacial Reaction Processes and Mechanisms in the Earth’s Critical Zone

The employment of bright light sources generated at synchrotrons has greatly advanced our understanding of important environmental interfacial (mineral/water, mineral/microbe, plant/soil) reaction processes in the soil, environmental, and geological sciences over the past two decades. This plenary paper will provide background on principles and types of synchrotron radiation techniques with an emphasis on the use of synchrotron-based X-ray absorption spectroscopy (XAS), X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD) and microtomography to elucidate speciation of contaminants in heterogeneous soils, surface precipitation phenomena, mechanisms of rapid redox transformations, microbial transformations on mineral surfaces, air and terrestrial emanated particulate reactivity and composition, and metal reactivity and speciation in hyperaccumulator plants.

Donald Lewis Sparks

Microbial Role in Global Biogeochemical Cycling of Metals and Metalloids at the Interfaces in the Earth’s Critical Zone

Microorganisms are intimately involved in many processes of fundamental importance to geology, and these include biotransformations of metals and minerals, as well as related substances like metalloids, and metal radionuclides (

Gadd et al., 2005

;

Gadd, 2007

). Such processes are involved in bioweathering, mineral dissolution and formation, and soil formation and development. Integral to all mechanisms are interactions with metals, and microorganisms are intimately involved in metal biogeochemistry with a variety of processes determining mobility, and bioavailability (

Gadd, 2005

;

2008

). The balance between metal mobilization and immobilization varies depending on the organisms involved, their environment, and physico-chemical conditions. Metal mobilization can arise, e.g. from leaching mechanisms, complexation by metabolites, and methylation where this results in volatilization. Immobilization can result from sorption, transport and intracellular sequestration or precipitation as a variety of “organic” and inorganic biominerals, e.g. oxalates (fungi), carbonates, phosphates and sulfides (

Sayer et al., 1999

;

Burford et al., 2003

,

2006

).

Geoffrey Michael Gadd

The Role of Mineral Colloids in Carbon Turnover and Sequestration and the Impact on Climate Change

Frontmatter

Soils as Source and Sink of Environmental Carbon Dioxide

World soils contain 2500 Pg C to 1-m depth, comprising of 1500 Pg of soil organic C (SOC) and 950 Pg of soil inorganic C (SIC) (

Houghton, 2007;

Lal, 2004

). Therefore, the soil C pool is 3.1 times more C than the atmospheric pool (800 Pg and increasing at the rate of 4.1 Pg C·yr

−1

) and 4.0 times the biotic pool (620 Pg and decreasing at the rate of 1.6 Pg C·yr

−1

). The current global C budget comprises anthropogenic emissions of 8.0 Pg C·yr

−1

from fossil fuel combustion and cement manufacture, and 1.6 Pg C·yr

−1

from deforestation, biomass burning and soil cultivation. Of the total emission of 11.5 Gt C E (including CO

2

, CH

4

and N

2

O) in 2000, 14% (1.6 Pg) were those due to agricultural activities and 18% (2.1 Pg) from land use conversion. Thus, land use and agriculture contribute about one-third (32%) of total anthropogenic emissions. Confirmed sinks include atmospheric absorption of 4.1 Pg C·yr

−1

, oceanic uptake of 2.3 Pg C·yr

−1

, and a land sink of about 1.5 Pg C·yr

−1

(WMO, 2008). Thus, there is an unknown terrestrial sink of about 1.7 Pg C·yr

−1

.

Rattan Lal

Impacts of Mineral Colloids on the Transformation of Biomolecules and Physical and Chemical Protection of Soil Organic Carbon

Soil mineral colloids, along with enzymes, have the ability to catalyze the transformation of biomolecules, which are from biological residues, root exudates, and biological metabolites, to relatively recalcitrant humic substances (HS). Virtually all HS in a wide range of soils are bound to mineral colloids, especially short-range ordered (SRO) Al and Fe (oxy) hydroxides because of their large specific surface area, high density of reactive sites, and surface reactivity. Soil mineral-HS complexes may anchor unstable plant constituents by various adsorptive forces and/or chemical binding. Highly degradable proteins, for example, may be protected against rapid biodegradation by their neucleophilic addition to mineralcomplexes. Besides chemical protection, mineral colloids have the ability to interact with biomolecules and microorganisms to form microaggregates. Furthermore, organic substances serve as intraicroaggregate binding agents leading to the formation of macroaggregates through biogenic aggregation processes. The vast majority (90%) of soil organic C (SOC) in surface soil is located within aggregates. Undecomposed biological materials have turnover times in terms of years. Turnover times of occluded SOC increase with decreasing aggregate size. SOC in macroaggregates has turnover times in terms of decades and the turnover times are about centennials for SOC in microaggregates. Tounover times of chemically protected SOC through binding to mineral surfaces usually approach millennia. Therefore, mineral colloids play a vital role in governing the transformation and turnover of soil organic matter and the impact on climate change.

Pan Ming Huang

Unravelling the Biogeochemical Cycles of Carbon and Nutrients in Forest Ecosystems: Innovative Approaches with Advanced Stable Isotope and NMR Techniques as well as Soil Chemical and Physical Methods

Long-term impacts of global climate change (GCC) and local forest management on important biogeochemical cycles of carbon (C) and nutrient cycling in the soil-plant ecosystems are complex and difficult to assess, particularly under gradually and continuously rising atmospheric carbon dixoide concentration [CO

2

] and warming in the real world with multiple limiting factors. In this presentation, we highlight the recent developments and applications of advanced stable isotope, nuclear magnetic resonance (NMR) and bio-molecular techniques, in an integrated approach with innovative rhizosphere and tree ring methods, for improving our understanding and management of above- and below-ground C and nutrient cycling processes in forest ecosystems, particularly in response to GCC and local management practices as well as mitigation / adaptation strategies. The opportunities and limitations of these techniques for investigating C and nutrient cycling processes in forest ecosystems are discussed, in the context of both short- and long-term impacts on the above- and belowground processes. Improved understanding and knowledge of environmental fingerprints of the biogeochemical cycles embedded in tree rings can be effectively used to account for long-term forest productivity and C stocks at local, regional and global scale in response to the future GCC and management options.

Zhihong Xu

Effects of Soil Management from Fallow to Grassland on Soil Microbial and Organic Carbon Dynamics

Permanent 60 year fallow, arable and grassland soils from the Highfield Ley-Arable Experiment at Rothamsted Research, UK were used to investigate if extremes in soil management affected soil microbial biomass, microbial activity and microbial diversity. They were incubated under laboratory conditions, with and without amendment with a labile (yeast extract) and recalcitrant substrate (ryegrass). Microbial biomass ATP concentrations were not significantly different between the soils, with or without substrate addition. The biomasses in the three soils also mineralised the two substrates similarly and microbial biosynthesis efficiency (measured as biomass C and ATP) was similar. However, Phospholipid Fatty Acid (PLFA) analysis revealed that microbial community structure, with and without substrates, differed significantly between soils. Therefore substrate type drives soil microbial ecosystem response much more than does soil microbial biodiversity.

Yuping Wu, Sarah Kemmitt, Jianming Xu, Philip C Brookes

Effect of Long-term Fertilization on the Sequestration Rate of Physical Fractions of Organic Carbon in Red Soil of Southern China

Typical red soil samples were collected from 17 years long-term fertilization experiments in Qiyang county of southern China. Physical fractions of the red soil include free particulate organic carbon (fPOC), intra-microaggregate particulate organic carbon (iPOC) and mineral associated organic carbon (MOC), were measured and the effects of fertilization on changes of soil organic carbon (SOC) stocks were analyzed. The results indicated that application of manure and manure-mixed-chemical fertilizer (M, NPKM, 1.5NPKM) significantly enhanced SOC and changed its physical fraction distribution. The highest sequestration rate in fPOC (290.6∼408.3 kg·ha

−1

·yr

−1

), iPOC (162.0∼179.2 kg·ha

−1

·yr

−1

) and MOC (322.9∼514.5 kg·ha

−1

·yr

−1

) were observed in these treatments. However, the content of iPOC and MOC didn’t increase in unbalanced chemical fertilizer application treatments (NP, N) in red soil, and they maintained lower SOC sequestration rate. The percentage of SOC sequestration distribution in different physical fractions under balanced fertilization treatments (NPK) followed the order: MOC (45.2%∼62.7%) > fPOC (21.9%∼35.2%) < iPOC (15.1%∼20.0%). The highest percentage of MOC implied that SOC associated silt and clay were the primary mechanism of SOC sequestration in red soil.

Minggang Xu, Xiaogang Tong, Xiujun Wang

Abiotic Catalysis of the Maillard and Polyphenol-Maillard Humification Pathways by Soil Clays from Temperate and Tropical Environments

The Maillard reaction and integrated polyphenol-Maillard reaction are regarded as important pathways in natural humification. Little is known about the abiotic catalysis of these humification pathways by naturally occurring soils and sediments. Therefore, the objective of this study was to investigate the abiotic catalysis of the Maillard reaction and integrated polyphenol-Maillard reaction by two contrasting soil clays from a temperate (Canadian Prairies) and tropical (Northeastern South Africa) region. Treatments containing an equimolar amount of glucose and glycine (Maillard reaction) or catechol, glucose and glycine (polyphenol-Maillard reaction) in the presence of temperate Mollisol and tropical Oxisol clays, were conducted under environmentally relevant conditions, i.e., pH 7.0 and 45 °C, for a period of 15 days under sterile conditions. The nature of the humification products were examined through C and Al K-edge, and Fe and Mn L-edge NEXAFS spectroscopy. The Oxisol clay enhanced humification in the Maillard and integrated catechol-Maillard systems to a greater extent than the Mollisol clay, which is attributable to its high content of sesquioxides, particularly poorly-crystalline Mn oxides. The humic substances produced in the Oxisol- and Mollisol-catalyzed polyphenol-Maillard reaction systems were chemically distinct from one another. Changes were observed in the Al coordination and Fe and Mn oxidation states in the soil clays after humification. The Oxisol clay showed a much greater accumulation of organic C compared to the Mollisol clay in the Maillard and catechol-Maillard systems. These results reveal the important role of Fe(III) and Mn(III, IV) oxides present in soils in catalyzing the Maillard reaction and polyphenol-Maillard humification pathways. The findings of this study are of fundamental importance in understanding the role of soil clays from temperate and tropical regions in abiotic humification pathways and C stabilization in natural environments.

Ailsa Ghillaine Hardie, James Joseph Dynes, Leonard Myrell Kozaka, Pan Ming Huang

Effect of Organic Matter Application on CP-MAS-13C-NMR Spectra of Humic Acids from a Brown Soil

Organic matter (OM) applications can influence the amount and structural characteristics of humic acid (HA). The objective of this paper was to clarify the effect of long term OM application on the changes of structural characteristics in HAs, which provided new information for improving soil fertility by OM application. The experiment was carried out on a brown soil at Shenyang Agricultural University, Liaoning province, China. The experiment included three treatments: zero-treatment (

CK

br

), and two pig manure (PM) treatments (

O

1

and

O

2

) at the rates of 0.9 t·ha

−1

and 1.8 t·ha

−1

of organic carbon, respectively. The samples of the HA fraction were extracted, separated, purified and characterized by elemental composition, differential thermal analysis (DTA), δlg

K

value and CP-MAS-

13

C-NMR. The results indicated that the CP-MAS-

13

C-NMR spectra of the HA were quite similar to each other. But after OM application, the contents of alkyl C and O-alkyl C increased and the contents of aromatic C and carbonyl C decreased in HAs, indicating that the OM application decreased the content of aromatic C and was simplified the molecular structure in HAs.

Sen Dou, Kai Li

The Composition and Organic Carbon Distribution of Organo-mineral Complex in a black Soil as Influenced by Land-use Change and Long-term Fertilization

The aim of this experiment was to examine the impact of natural vegetation restoration and long-term fertilization on the composition and organic carbon distribution of organo-mineral complexes in a black soil. The results showed that the fine sand-size complex was the dominant particle of different size complexes. Contents of silt-size and fine sand-size complexes increased in the NP and NP plus animal manure (NPM) treatments, while the content of clay-size complexes decreased as compare with the non-fertilized treatment (NF). The contents of silt-size and clay-size complexes in the grassland (GL) and the bare land (BL) were the same as that in NF. Landuse change resulted in different dynamics in C sequestration in soil, which made cumulative CO

2

emissions differ significantly among the five treatments during the growing seasons. The content of <20 μm size complex in GL was more than those in NP and NPM. The GL has a potential of sequestering more C than tilled soils due to the stability of SOC stored in the <20 μm size fraction. The cumulative CO

2

emissions increased in the order of NP < GL < NPM. Long-term application of organic manure and vegetation restoration increased the organic carbon content of all sizes of complexes, but increased the cumulative CO

2

emissions. Nevertheless, these soil management practices have substantially increased C sequestration into the soil rather than net C losses.

Xiaozeng Hana, Xueying Hou, Haibo Li

Characterization of Dissolved Organic Matter Derived from Rice Straw at Different Decay Stages

This study characterized chemical and structural properties of dissolved organic matter (DOM) derived from different stages of rice straw decay under laboratory conditions. Ten different DOM samples were obtained and characterized using element composition analysis, Fourier-transform infrared spectroscopy, and

1

H,

13

C-nuclear magnetic resonance spectroscopy. The results showed that at the early stage of straw decay, lowweight- molecular components were dominant, such as carbohydrates, amino acids, and amino sugars. At the second stage, the contents of mono-, oligo-, and polysaccharides increased. At the later stage, aromatic products were dominant because of their strong recalcitrance for microorganisms. As straw decay proceeded, some small molecular chemicals (such as carbohydrates and acid amides) polymerized around the aromatic rings, suggesting that the DOM became more stable with decay time.

Hualin Chen, Jiangmin Zhou

Organic Fertility of Severely Eroded Soils: Effect of Organic and Inorganic Fertilization and Cropping Patterns

A study was conducted on farmer’s field for the restoration of fertility status of severely eroded soils in north west Pakistan during 2006 and 2007. Two factors viz fertilizer treatments included T1 (control), T2 (50% NP also called farmer’s practice), T3 (100% NPK) and T4 (20 t·ha

−1

farmyard manure integrated with 50% N and 100% PK as mineral fertilizers) whereas cropping patterns included C1 (maize-wheat-maize rotation), C2 (maizelentil-maize rotation) and C3 (maize-wheat+lentil intercrop-maize rotation). Experiment was started in Kharif 2006 and was carried out continuously for four seasons till Rabi 2007. At the end of the experiment, soil samples were collected from the surface (0∼20 cm) soil and analyzed for total N, microbial biomass N (MBN), mineralizable N, Organic matter (OM), microbial biomass C (MBC) at day 3, day 6 and day 10 incubation periods. Results suggested that the organic fertility of soil was significantly increased with fertilizer addition and the highest soil organic fertility was found in the treatment that received organic and inorganic fertilizers in integration (T4) which showed 52%, 14%, 17%, 60%, 56%, 57% and 60% increase in total N, mineralizable N, MNB, OM, MBC at day3, day 6 and day 10 over the control treatment respectively. Cropping patterns also affected soil organic fertility where cereal-legume rotation showed 21%, 13%, 6%, 17%, 21%, 22% and 13% increase in the above parameters and time. Fertilizers must be applied in integrated form which carries 50% N from inorganic source and the rest of 50% from organic sources to improve the level of organic fertility of eroded soils on sustained basis. Results further suggested that legumes must be entered into conventional cereal-cereal rotation to improve the N input and organic fertility of severely eroded soils.

Wiqar Ahmad, Farmanullah Khan, Muhammad Naeem

Biogeochemical Interfacial Reactions and the Transformation, Transport and Fate of Vital and Toxic Elements

Frontmatter

Role of Biomolecules in Influencing Transformation Mechanisms of Metals and Metalloids in Soil Environments

Characterizing the factors which affect the mobility, bioavailability, leaching and toxicity of metals and metalloids in soil environments is of paramount importance. Special attention is devoted to the influence of biomolecules, mainly roots exudates, as well as pH, nature of the sorbents, redox reactions on the transformation mechanisms of trace elements in cationic and anionic forms in soils. Time of reaction and the surface coverage have a great influence on the sorption/desorption processes of trace elements in the presence of organic ligands. Leaching and extraction tests are widely used for assessing trace element phytoavailability.

Antonio Violante

Biogeochemical Processes of Arsenic in Paddy Soils

Arsenic (As) is ubiquitous in the environment, and is regarded as class I carcinogen. For populations taking rice as the stable food, rice is the major pathway for human exposure to As. As dynamics in the soil-rice system is therefore critical in risk assessment and reduction for Southeast Asia, where As contamination widely distributes. The aim of this paper is to give an overview of biogeochemical processes in the soil-rice system, with strong focus on how molecular tools (physical, chemical and biological) can be used to unravel the mechanisms of arsenic transport, uptake and metabolism in this system.

Yongguan Zhu, Wenju Liu, Guilan Duan, Paul Williams, Guoxin Sun

Soil Microorganism-mineral-organic Matter Interactions and the Impact on Metal Mobility

Soils are huge reservoirs of micro-organisms. They contain all the main groups of microorganisms with a very large diversity of bacteria, fungi, algae, protozoa. In the upper layers of soils, bacteria can have a biomass of 1,000 to 4,000 kg·ha

−1

and an average number of 106 to 109 g

−1

of dry soil. Fungi have approximately the same to slightly higher biomass. Both bacteria and fungi are now well recognized as key agents of biogeochemical cycling of major and trace elements and as main actors of soil functioning. Other microorganisms as algae (photosynthetic organisms), present at the soil surface, are not so well known in soils and play a minor role, but are considered as endolithic pioner organisms involved in rock weathering particularly in cold and warm deserts. Lichens, a symbiotic association between algae and fungi, are also interesting as colonizing organisms and weathering agents.

Jacques Berthelin

Rhizosphere Processes and Management for Improving Nutrient Use Efficiency and Crop Productivity

High input, high output, low nutrient resource use efficiency and deteriorating environmental problems reflect the typical characteristics of intensive farming system in China. How to achieve synchronously high nutrient use efficiency as well as high crop productivity has become a great challenge in the intensive agriculture of China. In the past two decades, crop production has not proportionally been increased with increasing input of chemical fertilizers, leading to low nutrient use efficiency and increasing environmental problems. Traditional nutrient management strategy was highly dependent on external chemical fertilizer input, but ignored exploring biological potential of efficient acquisition and use of soil nutrient resources by plants intrinsically. Rhizosphere is the key centre of interactions among plants, soils and microorganisms; the chemical and biological processes occurring in the rhizosphere not only determine mobilization and acquisition of soil nutrients, but also control nutrient use efficiency by crops. The rhizosphere management strategy lays emphasis on maximizing the efficiency of root and rhizosphere processes in nutrient acquisition towards high-yield and high-efficiency sustainable crop production by optimizing nutrient supply in root zone, regulating root morphological and physiological traits, and manipulating rhizosphere processes and interactions. The strategies of rhizosphere management are proved to be an effective approach to increasing nutrient use efficiency and crop productivity towards sustainable crop production for main crops in China.

Fusuo Zhang, Jianbo Shen, Jingying Jing, Long Li, Xinping Chen

Effect of Soil Hg Stress on Expression of Heat Shock Protein Gene in Springtail Folsomia Candida

Transcriptional responses of hsp70 gene of the

Folsomia candida

were detected by relative real-time PCR assay when the springtail was exposed to a vegetable soil with different Hg concentrations or different exposure time. Results showed that the hsp70 gene expression level was significantly up-regulated when soil Hg was ≥0.25 mg·kg

−1

. The responses of this gene expression were strongly induced after 48 hours exposure under 1 mg·kg

−1

of soil Hg, which was probably due to the fast and sensitive response of the gene transcription to the Hg stress. Thus, the results suggested that the gene could be used as a biomarker to monitor the Hg pollution in soil and help early and fast environmental diagnostics or ecological risk assessment of Hg contaminated soils.

Yurong Liu, Yuanming Zheng, Yu Da, Jizheng He

Antimony, Arsenic and Other Toxic Elements in the Topsoil of an Antimony Mine Area

Twenty nine topsoil samples were collected from the Xikuangshan antimony mine and analyzed by ICP-MS, ICP-OES and HG-AFS for the following elements: As, Cd, Cr, Cu, Co, Ni, Hg, Pb, Sb and Zn. The objective of this study was to assess the level of topsoil contamination of Xikuangshan’s agricultural land. The concentration ranges (mg·kg

−1

) of the elements are: As 13∼267, Cd 0.7∼96.8, Cr 81∼315, Cu 23∼261, Ni 29∼86, Pb 27∼423, Sb 10∼2159 and Zn 68∼4217. Average concentrations of As, Cd, Sb and Zn exceeded the limits of agricultural production and human health. The accumulation of Cr, Cu, Ni and Pb in the topsoil of Xikuangshan area were minor than the other four heavy metals; these elements did not exceeded the threshold. Except for the background effect of the soils, anthropogenic factors are the major contributor to the the increased concentrations of heavy metals in soil. Combined with the principal component analysis, it was found that smelters and mining activities were the main sources of soil heavy metals while the lithology background of this area and agricultural practices play important roles in the accumulation of heavy metals.

Xiangqin Wang, Mengchang He, Jianhong Xi, Xiaofei Lu, Jun Xie

Microcalorimetric and Potentiometric Titration Studies on the Adsorption of Copper by P. putida and B. thuringiensis and Their Composites with Minerals

In order to have a better understanding on the interactions of heavy metals with bacteria and minerals in soil and associated environments, isothermal titration calorimetry (ITC), potentiometric titration and equilibrium sorption experiments were conducted to investigate the adsorption behavior of Cu

2+

by

Bacillus thuringiensis, Escherichia coli

and their composites with minerals. The adsorption capacity of Cu(II) by bacteriamontmorillonite composite was higher than that by their individual components, whereas bacteria-goethite composite adsorbed less Cu(II) than their individual components. Potentiometric titration revealed that some new adsorption sites were created in bacteria-montmorillonite systems and some adsorption sites were masked in bacteria-goethite systems. The thermodynamic parameters were obtained from the ITC experiments. The negative ΔG values indicated that the adsorptions of Cu(II) by bacteria, minerals and their composites were spontaneous processes. The ΔH values revealed that the reactive sites on bacterial surfaces were more important than those on minerals in binding heavy metals. The positive ΔS values suggested the dominant inner-sphere complexes of Cu(II) on the surface of bacteria, minerals and their composites.

Linchuan Fang, Peng Cai, Pengxiang Li, Wei Liang, Qiaoyun Huang

Sorption, Transformation and Migration of Zn in Some Soils with Percolated Water Regime

There were determined the parameters of applied Zn sorption by two taiga soils with different properties, composition of their formed species and the migration of their available ones. The laboratory and field experiments were used in this work. Laboratory experiments have identified the great potential absorption capacity of soils (especially of the upper organic horizons) towards applied zinc and ability to retain it relatively firmly. But this ability is not fully realized in artificial pollution under field conditions. This proves that the upper soil horizons are indeed a “critical area” of the crust even in the soils with percolated water regime.

Galina Vasilievna Motuzova, Natalia Jurievna Barsova

Speciation and Biochemical Transformations of Sulfur and Copper in Rice Rhizosphere and Bulk Soil—XANES Evidence of Sulfur and Copper Associations

The speciation of sulfur and copper in rice rhizosphere and bulk soil was investigated using integrated approach including sequential extraction and X-ray absorption near edge spectroscopy (XANES). Our results showed that Cu speciation exhibited a difference in rhizosphere and bulk soil of rice. In a flooded paddy soil, most Cu in the rhizosphere existed as Cu (II), whereas part of Cu transformed to Cu (I) in the bulk soil. Sulfur XANES showed the presence of multiple both oxidized and reduced states of sulfur in studied soil samples, with more oxidized sulfur in the rhizosphere than in the bulk soil. Copper and sulfur speciation changed depending on redox conditions. Changes in redox potential and microbial action shifted the sulfur oxidation and reduction reaction and affected the Cu speciation. Sulfur transformation played an important role on Cu speciation.

Huirong Lin, Jiyan Shi, Bei Wu, Jianjun Yang, Yingxu Chen, Yidong Zhao, Tiandou Hu

Population Dynamics of Ammonia Oxidizing Bacteria and Archaea and Relationships with Nitrification Rate in New Zealand Grazed Grassland Soils

The oxidation of ammonia (NH

3

) to nitrate (NO

3

) in different ecosystems is a key process in the global nitrogen (N) cycle which has major ecological and environmental implications both in influencing nitrous oxide (N

2

O) emissions and nitrate leaching. We investigated the population dynamics of ammonia oxidising bacteria (AOB) and ammonia oxidising archaea (AOA) under controlled laboratory conditions using quantitative polymerase chain reaction (qPCR or real-time PCR) in six different intensively managed dairy grassland soils sampled from across New Zealand. The AOA

amoA

gene copy numbers varied from 1.27×10

7

to 3.85×10

6

. The AOA to AOB ratio varied from 10.7 to 0.2. While the AOB population grew by 3.2 to 10.4 fold in response to the addition of a urine-N substrate and were significantly inhibited by a nitrification inhibitor, dicyandiamide (DCD), the AOA population remained largely unchanged irrespective of the urine-N and DCD treatments. A significant exponential quantitative relationship was found between the AOB population and the nitrification rate, whereas no such relationship was found with AOA. These findings suggest that nitrification rate is more closely related to the dynamics of AOB than to that of AOA in these grassland soils with high nitrogen loads.

Hong Jie Di, Keith C. Cameron, Jupei Shen, Jizheng He, Chris S. Winefield, Maureen O’Callaghan, Saman Bowatte

Plant Clonal Systems as a Strategy for Nitrate Pollution Removal in Cold Latitudes

Nitrate removal is a major challenge in drinking water systems of major cities of the world and these are more acute in colder latitudes where metabolic conversion rates of biological species in the winter are slower. In order to achieve rapid nitrate removal we need multiple strategies including use of constructed wetlands in localized controlled greenhouse environments. In such localized controlled micro-environments higher temperatures can be managed for plant growth in hydroponics system through which nitrate contaminated water is fed for denitrification. Denitrification is a process that converts nitrate to gaseous nitrogen. This process is also referred to as “removal of nutrients”. The advantage of denitrification is that less oxygen is needed for the digestion of organic compounds in the aeration basin and specifically selected plants are needed for effective strategy. In the overall strategy to develop effective plant systems for controlled environment removal of nitrate pollution we have developed plant tissue culture technologies to isolate cold tolerant plant species that can be grown in aquatic and hydroponic environments. The use of innovative tissue culture technologies allows isolation of plant clonal lines of single seed phenotype origin that can be screened for cold tolerance and nitrate removal in aquatic zones. Such single seed plant clonal isolations are being evaluated for nitrate removal in the range of 25∼50 mg·L

−1

in hydroponic environments. The results of optimal removal of nitrate in greenhouse hydroponic studies will be presented. One group of plant species that hold promise for use in controlled greenhouse environments are species of aquatic mints. Strategy for specific clonal screening and use in cold latitude wetlands and greenhouse system for temperature control in the winter will be presented.

Derong Lina, Lijiang Hua, Hong Youa, Dipayn Sarkar, Baoshan Xing, Kalidas Shetty

Effect of Ionic Strength on Specific Adsorption of Ions by Variable Charge Soils: Experimental Testification on the Adsorption Model of Bowden et al.

The intersection of adsorption-pH curves for phosphate and arsenate by variable charge soils were observed at different ionic strengths (a characteristic pH). Above this pH, the adsorption of the two anions increased with increasing ionic strength, whereas below it the reverse trend occurred. Under the acidic conditions, Cu(II) adsorption by goethite and γ-Al

2

O

3

also increased with the increasing ionic strength. The change of the adsorption plane potential on variable-charge soils and Fe/Al oxides with ionic strength was responsible for the variation of specific adsorption of the anions and Cu(II). The zeta potential of soil colloids and Fe/Al oxides changed with ionic strength as an opposite trend to their surface charges. This gave an experimental proof to support the interpretation.

Renkou Xu, Jun Jiang, Cheng Cheng

Estimation of the Electrostatic Repulsive Force among Charged Clay Particles in Aqueous Systems

Electrostatic force of charged particles is crucial for some important physical processes in a wide range of scientific fields, such as the bio-molecular assemblies in modern biophysics, diffusion-controlled chemical kinetics and ion transport in soils, as well as soil particle aggregation and dispersion, which may be closely relevant to soil erosion and water eutrophication in environment. In this report, an approach for theoretical estimation of the electrostatic repulsive force among clay particles in aqueous solutions was suggested. The results showed that:

1

) the suggested theory for the electrostatic force calculation was well verified by our experiment;

2

) the accurate surface potential value is the key in obtaining an accurate calculation of the electrostatic force;

3

) the electrostatic repulsive force among clay particles in aqueous solution will sharply increase with the decrease of electrolyte concentration in bulk solution of soil. The suggested approach may be important in the studies of soil particle interaction and charged particle transportation.

Hang Li, Jie Hou, Xinmin Liu

Kinetics of As(III) and Cr(III) Oxidation by OH-birnessites with Various Average Oxidation States (AOSs)

A series of alkaline birnessites (OH-birnessites), termed as Bir-OH1, Bir-OH2 and Bir-OH3, with average oxidation states (AOSs) of 4.02, 3.85 and 3.70 were synthesized. The PZCs of the OH-birnessites, around 1∼2, decreased with the increase of AOS. Oxidation of Cr(III) and As(III) by OH-birnessites in the initial reaction stage complied with the pseudo first order kinetics. The apparent reaction rate constants (K

obs

) in the initial reaction stage increased with the increase of AOS. The K

obs

of Cr(III) oxidation by the tested samples in order were: Bir-OH1 (0.0342 min

−1

) > Bir-OH2 (0.0178 min

−1

) > Bir-OH3 (0.0148 min

−1

). Those of As(III) oxidation were: Bir-OH1 (0.0951 min

−1

) > Bir-OH2 (0.0396 min

−1

) > Bir-OH3 (0.0071 min

−1

). The K

obs

also increased with increase of AOS. It was indicated that Mn(IV) and Mn(III) in birnessite had different reactivities, the AOS of OHbirnessites which was determined by the ratio of Mn(IV) and Mn(III) played an important role in affecting oxidation kinetics. In the initial stage of Cr(III) oxidation, Mn(II) release lagged behind Cr(VI) release. More and more Mn(II) were released to the solution as the reaction went on, and the ratios of released Mn(II) to Cr(VI) gradually approached the theoretical value of the reaction stoichiometry. While for As(III) oxidation, nearly no Mn(II) was detected in the whole oxidation process, the produced Mn(II) adsorbed to the surface of OHbirnessites and then formed precipitate, preventing the reaction from going on. It was implied that Cr(III) and As(III) oxidation had different kinetic behaviors on the surface of OH-birnessites.

Xionghan Feng, Jiali Xu, Fan Liu, Wenfeng Tan

Adsorption/Desorption Kinetics of Zn in Soils: Influence of Phosphate

Transport of heavy metals such as zinc in soils may be affected by several rate limiting processes including kinetic sorption and release. Batch kinetic experiments were carried out to evaluate sorption and desorption of Zn for soils having distinctly different properties. A second objective was to test the hypothesis that phosphate additions to soils increases zinc adsorption. Sorption isotherms exhibited strong nonlinearity as well as kinetic behavior. Distinct differences in the amount of Zn sorbed among the different soils where highest sorption was observed for the neutral Webster soil. In contrast Windsor and Olivier (acidic) soils exhibited lower sorption capacities where Windsor soil showed least sorption. The influence of P on increased Zn sorption was clearly manifested in the isotherms where similar trends were observed for the two acidic and neutral soils. Distinct discrepancies between adsorption and successive desorption isotherms indicate considerable hysteresis for Zn release the extent of which varied among the three soils. For the two acidic soils Zn released ranged from 50%∼60% of that sorbed whereas for the neutral soil only 10%∼15% of sorbed Zn was released over time.

H. Magdi Selim, Keli Zhao, Lixia Liao, Jianming Xu

Bioavailability and Redistribution of Trace Metals in Soil Washed with a Sulfosuccinamate Formulation

Leaching tests using single and sequential extraction procedures were conducted in four contaminated soils to evaluate changes in metal partitioning before and after washing with the anionic sulfosuccinamate surfactant Aerosol 22 (A22). Evaluation of metal redistribution is of major importance to understand trace metals behaviour and reduce environmental risks. For the four soils, differing in the level of contamination, the distribution of metals in the four fractions was altered after washing with A22, which may be due to the strong extraction and complexation potential of the carboxylate function in the sulfosuccinamate surfactant. Besides, results from sequential extraction showed that, in general, surfactant largely extracted the metals bound to the carbonates and organic matter, while only a minority percentage of extraction corresponded with the oxyhydroxides fraction. Single extractions confirmed that the presence of the sulfosuccinamate compound in soil increases metal bioavailavility and therefore comprises a risk for the environment.

Maria del Carmen Hernández-Soriano, Aránzazu Pea, Maria Dolores Mingorance

Fractions of Cd, Zn and Their Correlation with Soil Black Carbon in Contaminated Soils Affected by a Smelting Furnace

Investigation and analysis of soils in the heavily polluted farm field nearby a smelting furnace showed that heavy metal concentrations and organic carbon content in the soil decreased with increasing distance from the smelting furnace. Zinc (Zn) and cadmium (Ca) concentrations in surface soil decreased from 27107 mg·kg

−1

to 892 mg·kg

−1

and from 18.7 mg·kg

−1

to 1.04 mg·kg

−1

, respectively. It was found that soil organic carbon and black carbon had significantly positive relationship with the concentrations of total Zn and Cd in surface soils. BCR sequential extraction procedure was used to determine the concentration of Zn and Cd speciation forms in the contaminated soil. It was shown that Cd and Zn were predominant in exchangeable and reducible fractions. Heavy metal concentrations in soil size fractions tended to increase as particle size decreased.

Ling Liu, Na Li, Longhua Wu, Zhu Li, Jinping Jiang, Yugen Jiang, Xiya Qiu, Yongming Luo

Formation of the Metal Complexes between Protoporphyrin IX and Divalent Metal Cations in the Environment

Protoporphyrin IX is very slightly soluble in water whereas it is soluble in acidic as well as in basic aqueous solution. The UV-vis absorption spectrum of the protoporphyrin IX shows a very sharp and strong maximum absorption peak at 400 nm in acetonitrile-water mixture solution (1∶1v/v). The maximum absorption peaks reacted with divalent transition metal ions such as Cu

2+

, Zn

2+

, Fe

2+

were shifted to a longer wavelength and the absorbance of the maximum peak decreased as the contents of metal ions increased. However, the absorbance of the maximum absorption peak combined with representative divalent metal ion, Mg

2+

has nearly same value and the peak did not shifted. The formation constant (K

f

) of the metal protoporphyrin IX complexes reacted with Cu

2+

, Zn

2+

, Fe

2+

in acetonitrile-water mixture solution (1∶1v/v) were found to be 370, 418 and 24, respectively.

Chi-In Junga, Jeong-Im Yang, Cahul-Ho Park, Jebe-Bum Lee, Hyoung-Ryun Park

The Impact of Urban Activities on Heavy Metal Distribution and Bioavailability Index in Selected Tropical Urban Soils

The distribution and bioavailability of heavy metals in the environment is of particular concern because of their potential toxicity to the ecosystem. A study was conducted to investigate the impact of informal industries (commonly known in Kenya as

Jua kali

industries) on the heavy metal distribution and bioavailability indices in selected tropical urban soil samples from Nakuru town, Kenya. The study revealed that both the total metal contents and the bioavailability indices varied with the soil site and depended upon the intensity of industrial activities (painting, oil spills from engine overhauls, deposited wastes) on the sites. The informal industrial sites had higher levels of heavy metal content than the non-industrial sites, indicating that the informal industrial activities in these areas contributed to the elevated amounts of heavy metals. The mean heavy metal content in the informal industrial sites was highest for Zn followed by Fe, Pb, Mn and Cu. In the non-industrial sites, the trend was the same; however, lower values were obtained. The amounts of heavy metal extracted varied with the nature of the extractant. AAAc-EDTA extracted the highest amounts of the metals both from the industrial and nonindustrial sites. The AAAc-EDTA extractable metal could be taken as the bioavailability index of the metals for the soils studied. The study is of significance in developing regulations for setting up informal industrial sheds in relation to micro-urban farming.

John Onam Onyatta, Charles Kibii Chepkwony, Peter Olengo Ongoma

Nitrate Accumulation as Affected by Nitrogen Fertilization and Foliar Application of Micronutrients in Rocket Plant

Field experiment was carried out in season 2007/2008 in a special farm near El-Mansoura City Dakahlya Governorate, Egypt to estimate the effect of N fertilization levels (0, 70, 105 and 140 kg N· ha

−1

) in the form of NH

4

NO

3

33.5% N as soil application and foliar application of Fe-EDTA at the rate of 300 mg · kg

−1

, Mo as sodium molybdate at the rate of 50 mg · L

−1

and their mixture (Fe + Mo) at the same used rates, each treatment was replicated three times. The results can be summarized as follow: Increasing N levels from 70, 105 and 140 kg N · ha

−1

significantly increased all growth parameters i.e. plant height (cm), fresh and dry weight (g · plant

−1

) for rocket plant at marketing stage as compared to the control treatment. Foliar spraying of Fe or Mo either as a solely addition or in combination together on plants fertilized by N rates (70, 105 and 140 kg N · ha

−1

) significantly increased plant height, fresh and dry weight of rocket as compared to the untreated one. The average values of all growth parameters under study with foliar spraying of micronutrients were higher than that obtained without spraying under any level of N fertilization. Nitrate and nitrite concentrations in the fresh leaves of rocket plant were gradually and significantly increased due to increasing N level from 0 up to 140 kg N · ha

−1

. On the contrary of this trend, the activity of nitrate reductase enzyme (μ · NO

2

·min

−1

· g

−1

· FW) was sharply and significantly decreased as the level of N fertilization was increased. Foliar application of Fe or Mo either in a single form or combined together in the presence of N levels under investigation significantly decreased the mean values of NO

3

-N and NO

2

-N mg · kg

−1

in the leaves of rocket plant than those obtained for the plants treated with the same N levels only. As for the activity of nitrate reductase enzyme, foliar spraying of (Fe + Mo) was superior for increasing the mean values of this parameter at any level of N fertilization. Applying nitrogen at the rates of 70, 105 and 140 kg N · ha

−1

resulted in significantly increase the values of N% over the control treatment. Foliar spraying of Fe or Mo in single form combined with the same N rates under study led to an increase in the average values of N% rocket leaves compared with those obtained from the same N rates without Fe or Mo in foliar way. Such effect of Fe or Mo spraying was realized when (Fe + Mo) were foliarly applied tell the rate of 105 kg N · ha

−1

. Increasing the rate of N addition from 105 to 140 kg·ha

−1

in the presence of (Fe+Mo) had no significant effect on the values of N% in rocket leaves. The mean values of Fe and Mo in rocket leaves significantly decrease as the level of N fertilization was increased. The mean values of Fe and Mo in rocket leaves significantly decrease as the level of N fertilization was increased. An adversely effect was realized due to spraying of (Fe + Mo) combined with the investigated N rates, whereas the mean values of Fe and Mo in rocket leaves significantly increased as the level of N fertilizer was increased. The calculate values of N/Fe and N/Mo ratios did not increase due to an increase of N rates in the presence of (Fe + Mo) foliar addition, but it tended to be constant around (18 × 10

−2

) and (19 × 10

−3

) for N/Fe and N/Mo, respectively.

Ayman Mohamed El-Ghamry

Fractions of Heave Metals in Paddy Fields and Their Spatial Relationship to Rice Plant

To access the distribution in fractions of heavy metals in paddy fields in Wenling city in Zhejiang Province, China, extensive sampling was carried out to identify spatial correlation and bioavailability to rice grown on these soils at the regional scale. The results showed that Cd in soil were predominantly association with exchangeable and Fe-Mn oxide fraction; while Cu, Ni, Pb and Zn with residual fraction. Most heavy metals studied in rice were significantly (

P

<0.01) correlated with exchangeable fraction, which is considered as readily bioavailability to rice.

Keli Zhao, Xingmei Liu, Jiachun Shi, Jianming Xu

Competitive Sorption of Nickel and Cadmium in Soils

Competing ions strongly affect heavy metal retention and release in soils. In this study, we evaluated the sorption of Ni and Cd in single and binary Ni-Cd systems in three different soils; Windsor sand, Olivier loam and Webster loam. Nickel and Cadmium sorption isotherms were obtained after 24 hours of reaction and exhibited L-type patterns. Cd adsorption on the two acidic soils (Windsor and Olivier) was larger than Ni. In contrast, for Webster soil with a neutral pH, Ni sorption was larger than Cd. The Freundlich model was utilized to describe Ni and Cd adsorption isotherms. The estimates for K

f

indicated that Ni sorption by the soils was significantly inhibited by the presence of Cd. Similarly, the sorption of Cd was suppressed by the presence of Ni ions. It was also found that when the added metal concentration increased in Ni-Cd system, the suppressed effect of the metal ion competition increased. Moreover, kinetic batch experiments were carried out to study Ni retention behavior. Ni sorption increased with increasing reaction time for all soils and the rate of sorption varied among soils. Desorption of Ni was hysteretic in nature, which indicated a lack of equilibrium retention and/or irreversible or slowly reversible processes. Soil samples with highest Ni concentrations were analyzed through EXAFS. The EXAFS results provided evidence of irreversible reaction for Webster soil which exhibited strongest affinity for Ni.

Lixia Liao, Amitava Roy, Gregory Merchan, H. Magdi Selim

Interaction Effect between P and K Fertilization on Faba Bean Plant (Vicia faba L.) Grown under Salt Affected Soils

Two field experiment were carried in the winter seasons of 2006/2007 and 2007/2008. To study the interaction effect of P and K fertilization on growth, yield, nodules formation, proteins%, phytic acid% and nutrients uptake of faba bean plants grown under salt affected soils. The experimental soils used represent nonsaline (2.36 dS·m

−1

EC) and saline (5.6 dS·m

−1

EC). The effect of three P levels (0%, 50%, 75%, 100% from recommended dose as superphosphate 15.5% P

2

O

5

), the foliar K levels (0%, 1%, 2% from recommended dose in the form of potassium sulphate 48% K

2

O) and seeds (Skha1 cultivar) before sown inoculated by ryzobium. A split-split plot design with four replicates were used. The main findings could be summarized as follows: 1) Saline conditions decreased the plant height, No of branches/plant, seed weight/plant, 100-seed weight, seed yield (ardab/fed.), straw yield (ton/fed.) No. of nodules/plant, protein % and nutrients uptake (N, P, K Kg·fed

−1

) in both seasons. And the heights results were obtained from normal soils, while saline conditions increased significantly phytic acid%. 2) Adding 2% K(foliar) significantly increased all studied factors under study in both seasons except phytic acid%, where adding 1%K(foliar) casing rising values of phytic acid in both seasons. 3) 100% P treatment gave the highly significant increase in all factors in both seasons. 4) The interaction between all studied treatments on faba bean characteristics under study had a significant effect, which, the best results were obtained from the interactions of normal soils with 2% K and 100% P treatment at all studied factors except the interaction of saline soils with 0% K and 100% P gave the highest results for phytic acid%. 5) It can be noticed that, ryzobium can not act their roles well in nodules formation under saline conditions.

Mohamed Rida Abd EL-HadyMohamed Ebrahem, Adel Mohamed Abd EL-Hameed Abd EL-Mohsen

Design of a POSS-modified Zeolite Structure and the Study of the Enhancement of Ammonia-nitrogen Removal from Drinking Water

In this work, the mesoporous zeolite molecular sieve (ZMS) surface was modified using polyhedral ologomeric silsesquioxane (POSS) with carboxyl sodium terminal groups (POSS

−COONa

) as ion-exchange active groups. The characterization of the POSS

−COONa

structure by standard techniques (such as SEM, TEM, XRD, etc.) was investigated and discussed. With this approach, the exchange capacity of ammonia-nitrogen (NH

3

-N) in water would be greatly increased. The diffusion behavior of NH

3

-N in the pores of POSS-modified ZMS was calculated using a molecular dynamic simulation (MDS) program of the Materials Stutio (MS) software which facilitate to study the effect of POSS modification on pore structure and exchange capacity. The interface binding energy between POSS

−COONa

and ZMS was calculated using MDS, facilitating the study of a simple regeneration method for exchanged active groups. It was estimated that the weight of the POSS-modified ZMS could be reduced by 25% for the same 90% of NH

3

-N removal rate of the normal ZMS under the same conditions. If the removal rate of the normal ZMS for a higher concentration of NH

3

-N in water was 60%∼70%, the removal rate of the POSS-modified ZMS could be up to 80%∼90%.

Derong Lin, Lijiang Hu, Qun Zhang, Hong You

Study on Immobilizing Soil Exogenous Lead Using Phosphate Rock

The effect of phosphate rock (PR) on exogenous Pb fractions in yellow cinnamon soil (S1) and latosol soil (S2) were studied by Tessier’s sequential extraction procedures after PR was applied into the two soils at four levels of 0, 50, 500 and 2000 mg·kg

−1

. The results indicated that the content of exchangeable Pb in two soils decreased significantly with the rising of PR amount, which reached the minimum of 2.95 mg·kg

−1

for yellow cinnamon soil and 3.57 mg·kg

−1

for latosol soil under the treatment of 2000 mg P·kg

−1

soil (PR3). Both of the residual fractions of Pb in the two soils reached the maximum under the treatment of 2000 mg P·kg

−1

soil, 38.5 mg·kg

−1

for yellow cinnamon soil and 66.1 mg·kg

−1

for latosol soil. To sum up, the content of exogenous exchangeable Pb decreased and the residual fraction augmented conversely for both soils after the two soils being applied with testing PR. In conclusion, the result reflected that Pb had been immobilized effectively by PR in two tested soils.

Guanjie Jiang, Hongqing Hu, Yonghong Liu, Chang Yang, Haizheng Yang

Long-term Fertilizer Application Alters the Balance and Vertical Distribution of Phosphorus in a Calcarosol

The information on the distribution of P fertiliser in soil profile would be beneficial for better P management in farming systems. The aim of this study is to investigate how the long-term application of fertiliser P affects the vertical distribution of P in the soil and P balance. Soil samples were collected from a long-term permanent P fertiliser trial and were sequentially extracted for P fractions. There was a net negative P balance over the 66 years in the nil-P and low P (3 kg P·ha

−1

) treatments. In contrast, applying 12 kg P·ha

−1

to each wheat crop led to a highly positive P balance of 106 kg P·ha

−1

in this soil, resulting in P accumulation in the top 10 cm. Nil and low P application rates resulted in lower soil Picontent at 5∼20 cm depth. The transformation of the residual P fertiliser into all Pi fractions suggests that the applied P had transferred into different P forms which are either readily available or sparingly available to subsequent crops.

Dang Thanh Vu, Caixian Tang, Roger Armstrong

Nitrate Nutrition But Not Rhizosphere pH Enhances Zinc Hyperaccumulation in Thlaspi caerulescens(Prayon)

The Zn phytoremediation potential can be improved by applying nitrate fertilizers to increase the biomass and Zn content of shoots. However, it is uncertain whether this is due to assimilation of the nitrate specifically or as a consequence of a pH increase in the rhizosphere induced by nitrate uptake. A solution culture experiment was conducted to understand the effect of nitrogen form and solution pH on Zn phytoextraction and element composition in roots and shoots of

Thlaspi caerulescens

(Prayon). The plants were grown with basal nutrients including 300 μmol·L

−1

Zn and supplied with (NH

4

)

2

SO

4

, NH

4

NO

3

or Ca(NO

3

)

2

. The solutions were maintained at pH 4.5 or 6.5. The provision of NO

3

rather than NH

4

+

was more effective at either pH 4.5 or 6.5 in maximizing Zn accumulation in the shoots. The effect of N form on Zn and Ca accumulation was confirmed to be similar. The lower concentration of N in NO

3

-fed shoots suggests that it is the N compounds within the plant, and not the quantity of N, which increased Zn tolerance and promoted hyperaccumulation in

T. caerulescens

.

Alison C Monsant, Gaelle Ng Kam Chuen, Yaodong Wang, Caixian Tanga

Adsorption of Phosphate and Arsenate on New Al13-Oxalate Precipitate: Spectroscopic and Macroscopic Competitive Adsorption Investigations

Coprecipitates of aluminum-organics play important roles in the transport of phosphate and arsenate in soil environment. A new polynuclear aluminum organomineral precipitate (Al

13

-Oxalate precipitate) was prepared to investigate the adsorption behavior of phosphate and arsenate on a noncrystalline aluminum precipitate. Important thermodynamic parameters of adsorption reactions were evaluated using macroscopic adsorption data and the macroscopic competitive adsorption of two oxyanions also was investigated. The result shows that the adsorption reactions basically are a diffusion process, and that phosphate has a stronger chemical interaction with substrate than arsenate. FTIR spectroscopic studies have provided evidence for the formation of two different types of phosphate complexes in substrate, protonated bidentate and deprotonated bidentate complexes at pH 4 and pH ≥6, respectively. The XPS studies indicate that the precipitate substrate can acts as Lewis acid when adsorbing two oxyanions, and that more electron transfer relative to O in the substrate occurs during adsorption of phosphate compared to that of arsenate, meanwhile surface carboxylic carbon (COO−) is involved in the complexation reaction.

Jing Liu, Fenghua Zhao

Short-term Changes of pH Values and Aluminium Activity in Acid Soils after the Application of Nitrogen Fertilizers

Laboratory experiments were conducted to investigate the effects of nitrogen fertilizers on the soil pH, Al activity and Al phytotoxicity in 3 acidic soils. The results showed that application of urea and ammonium carbonate caused a significant increase in soil pH, and enhanced with the raising concentrations. However, application of ammonium sulfate induced a distinct decrease in soil pH. Moreover, application of urea and ammonium carbonate caused a profound decline in soil’ exchangeable Al. In contrast, application of ammonium sulfate induced a noticeable increase in soil’ exchangeable Al, and reinforced with the enhanced concentrations when compared with the no-fertilizer control. In our study, urea and ammonium carbonate significantly decreased exchangeable Al in acid soils, therefore reduced Al toxicity to maize seedlings. On the contrary, ammonium sulfate enhanced Al toxicity to maize seedlings and inhibited their growth.

Hejie Pi, Qingru Zeng, Zhaohui Jiang, Jianyu Liao, Xiaoyou Feng, Yulin Sun

Transformation of Nitrogen and Its Effects on Metal Elements by Coated Urea Application in Soils from South China

This paper studied the transformation of N and its effects on metal elements under supply of two types of urea. The results showed that hydrolysis rate of coated urea was lower than common urea. After 48 days incubation, the concentrations of NH

4

+

and NO

3

in soil were greater by coated urea application than that by common urea application. Urea application decreased in the first week, and then increased the concentrations of Al, Mn and Ca while the effect of treatment on soil pH followed the opposite pattern. In pH 4–8, concentrations of these elements were negatively correlated with soil pH.

Zhaohui Jianga, Qingru Zeng, Hejie Pi, Bohan Liao, Xiaoyou Feng, Yulin Sun

Impacts of Copper on Rice Growth and Yield as Affected by Pig Manure

A pot experiment was conducted to investigate the impacts of copper (Cu) on rice growth and yield grown in artificially Cu-contaminated paddy soil amended with 0%, 1% and 3% manure. Results showed that low level of Cu (i.e. 200 mg·kg

−1

) at 0% and 1% manure increased number of tillers significantly, while high levels of Cu (i.e. 600 and 800 mg·kg

−1

) caused significant reduction. Addition of 3% manure significantly decreased number of tillers at 100 and 800 mg·kg

−1

of Cu but increased obviously at 200 and 400 mg·kg

−1

. The average grain yield decreased along with increasing Cu levels at 0% manure and 30%∼72% reduction was observed at 400∼800 mg·kg

−1

. Grain yield was increased by 1% manure at 100, 200 and 400 mg·kg

−1

but decreased by 38% and 41% at 600 and 800 mg·kg

−1

compared to the control. In contrast to 0% and 1% manure, average grain yield for 3% manure was lowest at 100 and 200 mg·kg

−1

, while it was highest at 600 mg·kg

−1

compared to the corresponding control. Concentrations of Cu in rice grains increased with the increase of soil Cu levels at 0% manure, whereas application of 1% and 3% manure substantially decreased Cu contents in the grains and the effect of 3% manure was more remarkable. The results also showed that manure application decreased the amount of DTPAextractable Cu and reduced Cu bioavailability, which resulted in the reduction of Cu uptake by rice.

Jianjun Wu, Xiuling Yu, Zaffar Malik, Hao Chen, Jianming Xu

The Effects of Several Amendments on Forms of Lead and Its Uptake by Two Cultivars of Brassica Chinensis in an Acid Red Soil

We conducted a greenhouse study to examine the effects of various amendments on forms and bioavailability of Pb in red soils, and the differences in responses of two cultivars of

Brassica Chinensis

with contrasting resistance to Pb. The results showed that red soils with Pb contamination could be remedied by the amendments, and the uptake of Pb in plants could be decreased. The growth of plants was affected by the bioavailable forms of Pb and soil pH. The two cultivars differed in responses to the treatments. The best treatment was calcium magnesium phosphate which immobilized Pb to more residual forms, and significantly reduced the uptake of Pb in plants.

Xia Li, Jiachun Shi, Jianming Xu, Jianjun Wu

Does Iron Plaque Improve the Uptake and Translocation of Lead by Broad-leaf Cattail in Lead-contaminated Soils

The inhibited or enhanced uptake of heavy metals by iron plaque has been observed. The relationship between amounts of adsorption and accumulation of heavy metals and iron plaque on roots of wetland plant is still unclear. This study examined the effects of iron plaque on lead (Pb) absorption and translocation between underground and above-ground parts of a wetland plant species. Broad-leaf cattail (Typha latifolia L.) was grown in soil for four weeks under waterlogged conditions in a greenhouse. The soils were treated by Pb as lead nitrate at four levels (0, 100, 500 and 1000 mg Pb·kg

−1

) and waterlogged for two weeks. The results showed that the amount of iron plaque in the treatment with addition of 500 mg Fe·kg

−1

was general higher than that of the treatment with addition of 100 mg Fe·kg

−1

, Lead concentrations in both shoots and roots treated by 500 mg Fe·kg

−1

was more than that of the treatment with 100 mg Fe·kg

−1

. When the ratio of added Fe and Pb was 1, the accumulation of Pb in plants was higher than that of other treatments at the same Pd level. Appropriate amount of iron supplied will benefit lead accumulation in plant, which help the removal or stabilization of lead in constructed wetland.

Shunqin Zhong, Jianming Xu, Jiachun Shi, Jianjun Wu

The Influence of Zn2+ and Mn2+ on Pb2+ Adsorption Behaviors of Birnessite

The present study comparatively investigated Pb

2+

adsorption behaviors of the birnessite with high Mn average oxidation state (AOS) before and after treatment of preadsorption with Zn

2+

and Mn

2+

, respectively. The association of vacant Mn octahedral sites with Pb

2+

adsorption was further understood from the variances of birnessite AOS, d(110)-interplanar spacing, maximum Pb

2+

adsorption, maximum Zn

2+

and Mn

2+

release during the Pb

2+

adsorption before and after treatments. The birnessite AOS and d(110)-interplanar spacing were almost unchanged as the concentration of Zn

2+

increased, indicative of the unchanged vacant Mn octahedral sites, whereas the maximum Pb

2+

adsorption decreased from 3190 to 2030 mmol·kg

−1

due to occupancy of the treating Zn

2+

in adsorption sites. However, the AOS of the Mn

2+

-treated birnessites decreased and most of the treating Mn

2+

were oxidized to Mn

3+

and located below or above vacant Mn octahedral sites or migrated into vacant Mn octahedral sites. Increasing Mn

2+

concentration from 1 to 2.4 mmol·L

−1

increased the d(110)-interplanar spacing of the treated birnessites from 0.1416 to 0.14196 nm but decreased the maximum Pb

2+

adsorption of the treated birnessites from 3190 to 1332 mmol·kg

−1

, indicating the decrease in the amount of vacant Mn octahedral sites, mainly due to the increase of the produced Mn3+ migrating into vacant Mn octahedral sites. Therefore, birnesstie Pb

2+

adsorption capacity was largely determined by the number of Mn site vacancies.

Fan Liu, Wei Zhao, Wenfeng Tan, Xionghan Feng

Removal of Arsenite in Water Using Biogenic Schwertmannite as Adsorbent

Synthesis of schwertmannite through oxidation of ferrous sulfate by

Acidithiobacillus ferrooxidans

cells and adsorption of arsenite [As(III)] from water were investigated in the present study. Furthermore, the stability of As(III)-sorbed biogenic schwertmannite was studied. Results showed that hedge-hog like schwertmannite formed after reaction for 72 h were spheroid particles with a diameter of approximately 2.5 μm and its chemical formula could be expressed as Fe

8

O

8

(OH)

4.42

(SO

4

)

1.79

. As(III) in water could be effectively removed by biogenic schwertmannite with a maximum adsorption capacity of 113.9 mg As(III) per g of adsorbent and the optimum pH for As(III) adsorption was in the range of 7∼10. The As(III) removal was unaffected by the competing monovalent anions such as Cl

and NO

3

, whereas PO

4

3−

and SO

4

2-

greatly decreased the As (III) removal efficiency only when the molar ratio of P to As and S to As in solution reached 75∶1 and 750∶1, respectively. Furthermore, As(III)-sorbed biogenic schwertmannite exhibited no mineralogy phase change after ageing at pH 6.0 and 8.5 for 90 d. And As(III) could be effectively immobilized in biogenic schwertmannite, indicating that the transformation of metastable schwertmannite to goethite was significantly inhibited by sorption of As(III). The study shows that synthetic biogenic schwertmannite can be a very efficient innovative adsorbent for removing As(III) from water.

Yuehua Liao, Jianru Liang, Lixiang Zhou

Wien Effect Measurements in Soil Colloidal Suspensions: A Novel Method for Characterizing the Interactions between Charged Particles and Counter Ions

Adsorption is one of the most important chemical processes at the interface between soil particles and water. It determines the quantity of plant nutrients and pollutants which are retained on the surfaces of soil particles, and therefore, is one of the primary processes that affect transport of nutrients and contaminants in soils. The Wien effect, i.e., the dependence of the electrical conductivity of soil suspensions on electrical field strength, was proposed as the basis of a new method to characterize energy relationships between cations and soil particles. The results showed that the mean Gibbs free binding energies of the heavy metal ions with yellow-brown, black and brown soil particles decreased in the order of Pb

2+

>Zn

2+

>Cu

2+

>Cd

2+

, Pb

2+

>Cu

2+

>Zn

2+

>Cd

2+

and Pb

2+

>Cd

2+

>Cu

2+

>Zn

2+

, respectively, where the range of binding energies for yellow-brown soil (7.16∼8.54 kJ⋅mol

−1

) was less than that for black soil (9.05∼9.88 kJ⋅mol

−1

). The electrical field-dependent mean Gibbs free adsorption energies of these heavy metal ions for yellow-brown, black and brown soils descended in the order of Cu

2+

>Cd

2+

>Pb

2+

>Zn

2+

, Cu

2+

>Zn

2+

>Pb

2+

>Cd

2+

, and Cu

2+

>Pb

2+

>Cd

2+

>Zn

2+

, respectively. The mean Gibbs free adsorption energies of Cu

2+

, Zn

2+

, Cd

2+

and Pb

2+

at a field strength of 150 kV⋅cm

, for example, were in the range of 1.23 to 2.15 kJ⋅mol

−1

for the three soils.

Yujun Wang, Dongmei Zhou, Chengbao Li, Haowen Zhu, Wei Wang, Jun Zhou

Can Zn, Ca and Sulfate Amendments Affect Cadmium Uptake in Rice (Oryza sativa L.)

To investigate the effect of Ca, Zn and sulfate on Cd uptake and cultivar differences, a greenhouse experiment was carried out using two cultivars (

indica

type Teqing and

japonica

type Jefferson) of paddy rice with different levels of Zn sulfate and gypsum amendments. Total concentrations of Cd, Ca, Zn and S were measured in rice shoots and grain. Cd uptake by rice plants was affected significantly by Cd-amendment (

p

< 0.001). No difference in Cd uptake was measured between the treatments with and without Zn-amendment. However, the experiment exhibited a difference in Cd uptake as affected by rice cultivar. At the high Cd loading, there appeared to be the same uptake tendency in the Teqing cultivar for Cd, Zn and Ca. Reduction of plant Cd followed that of S during the maturation of the Teqing cultivar, whereas plant Ca decreased as the Zn concentration increased with maturation in the Jefferson cultivar.

Linfei Hu, Jianming Xu, Jianjun Wu, Murray B. McBride

Dynamics of As Species in the Interface of Soil and Rice Roots under Three Water Regimes

Arsenic (As) is an ubiquitous metalloid, widely distributed in the environment through both natural and anthropogenic pathways. A compartmented soil-sand culture system with rhizo-bag was used to investigate the dynamics of As and Fe species in the soil solution of rhizosphere under three water regimes in whole growing stages of rice plants. The results showed that flooded regime increased significantly concentrations of arsenite and arsenate at booting stage and grain-filling stage (

p

<0.001, the highest concentration: 2.67 mg·L

−1

) comparing with other two water regimes, unflooded and flooded-unflooded. There were significantly positive correlations between As and Fe species in soil solution of rhizosphere, between As concentrations in iron plaque and amounts of iron plaque formed as well.

Wenju Liu, Lina Chen, Ying Wang

Extra Supply of Calcium Is Not Required for Maximal Root Growth in the Nitrate and Phosphorus-rich Patch in an Acid Soil

Subsurface acidity is a major concern in agricultural soils. Surface application of lime is not effective and therefore alternative approaches are being tested to combat subsurface acidity. The supply of NO

3

increases excess anion uptake and results in rhizosphere alkalisation which can use as a method of biological amelioration. A glasshouse study was conducted with wheat to examine the effect of localised supply of P and Ca alone or combination with NO

3

on subsurface root proliferation and rhizosphere alkalisation in an acid soil. The results show that localised supply of NO

3

plus P in the subsurface maximises root proliferation without extra Ca supply.

Chandrakumara Weligama, Caixian Tang, Peter W. G. Sale, Mark K. Conyers, Liu De Li

Effect of Natural Acid Peat Application on the Phytoextraction of Cadmium from Contaminated Soils

Cadmium (Cd) poses a major environmental and human health threat because of its constant release to the environment through anthropogenic activities. Therefore, cost-effective remediation procedures for Cd contamination should be developed to restore ecosystem heath. Phytoremediation, the use of plants to extract contaminants from soils and groundwater has revealed great potential. However, it is limited by the fact that plants need time, nutrient supply and, moreover, have a limited metal uptake capacity. To increase Cd uptake by plants, the effects of the application of natural acid peat and the resulting decrease in soil pH on the amount of Cd taken up by plants were investigated in a pot experiment using two paddy soils contaminated artificially with Cd. An experiment was conducted using a root-bag technique, and four treatments of peat were applied: control(no peat treatment) and peat application (2.5, 5.0, 10.0 g·kg

−1

). The peat was applied to the soil at two Cd dosages(2.5 and 5.0 mg Cd·kg

−1

soil). The uptake of Cd by plant

Brassica campestris ssp. Chinesis L

was determined and its relation to the amounts of total and bioavailable Cd in the soil was investigated. It was found that the amount of bioavailabile Cd of the soils, as determined by diethylenetriaminepentaacetic acid (DTPA) extraction, was little affected by applications of the peat, but plant uptake of Cd was enhanced, in some cases up to 114.6%∼123.6%. At the contamination level of 2.5 mg Cd·kg

−1

soil, the peat added at a rate of 5.0 g·kg

−1

soil increased the Cd concentration in the shoot from 9.7 to 11.6 mg·kg

−1

in the blue clayed paddy soil and from 13.1 to 16.1 mg·kg

−1

in the yellow mettled paddy soil. At the contamination level of 5.0 mg Cd·kg

−1

soil, the peat added at a rate of 10.0 g·kg

−1

soil increased the Cd concentration in the shoot from 25.3 to 29.8 mg·kg

−1

and from 29.1 to 33.4 mg·kg

−1

in the blue clayed paddy soil and the yellow mettled paddy soil, respectively. The amount of Cd in shoots (mg·plant

−1

) was also significantly increased by the application of 5.0 and 10.0 g peat·kg

−1

soil. The enhancement is attributable to the decrease in pH and chelate-assisted phytoextraction, resulting in higher Cd availability.

Iksong Ham, Jianming Xu, Linfei Hu, Pan Ming Huang

Anthropogenic Organics, Crop Protection and Ecotoxicology

Frontmatter

Interaction of Anthropogenic Organic Chemicals with Organic Matter in Natural Particles

This lecture will review sorption to organic substances in soils and sediments including natural organic matter (NOM) and black carbon (BC) materials. In it I will discuss molecular-level interactions separately from the point of view of the sorbing molecule and the sorbent matrix.

Joseph J. Pignatello

Decontamination of Soils through Immobilization of Anthropogenic Organics by Biotic and Abiotic Catalysts

Processes that cause immobilization of contaminants in soil are of great environmental importance because they may lead to a considerable reduction in the bioavailability of contaminants and may restrict their leaching into groundwater. Previous investigations demonstrated that pollutants can be bound to soil constituents by either physical or chemical interactions (

Calderbank, 1989

). From an environmental point of view, chemical interactions are preferred, because they frequently lead to the formation of strong covalent bonds that are difficult to disrupt by microbial activity or chemical treatments. Humic substances resulting from lignin decomposition appear to be the major binding ligands involved in the incorporation of contaminants into the soil matrix through stable chemical linkages (

Bollag et al., 1997

;

Gevao et al., 2000

).

Jean-Marc Bollag

Effects of “Aging” on Bioreactive Chemical Retention, Transformation, and Transport in Soil

The fate of a bio-reactive organic chemical, such as a pesticide, in the soil environment is governed by the retention, transformation, and transport processes, and the interaction of these processes. Retention is the consequence of interaction between the chemical and the soil particle surface or soil components thereon. The retention processes, frequently described as adsorption or simply sorption, may be reversible or irreversible. Understanding the sorption process for a pesticide is important as it can retard or prevent pesticide movement, and affect availability of the pesticide for plant or microbial uptake or for biotic or abiotic transformation. While sorption is affected by the physical and chemical properties of both the pesticide and the soil particle resulting in a variety of retention mechanisms, increased contact time (i.e. aging) may also result in the formation of a stronger bond or a change in the binding mechanism between pesticide and soil, matrix deformation, diffusion of pesticide into remote sorption/binding sites (i.e. microsites in soil micropores), physical entrapment or sequestration of the pesticide in soil organic matter or clays, or a combination of these processes, all of which may affect the retention or sorption/desorption of the chemical in soil and in turn affect the processes of its transformation and transport (

Cheng, 1990

;

Cheng et al., 1994

;

Cheng and Koskinen, 2002

).

Hwei Hsien Cheng, William C. Koskinen

Interaction of Bttoxin with Organo-mineral Surfaces and Consequences for Its Fate in the Environment

About 40% of genetically modified crops contain the insecticidal trait engineered from the soil bacterium

Bacillus thuringiensis

. Plants produce an insectidal protein and it is important to understand how the interactions of this protein with soil influence its persistence and its biological properties. We have used various techniques to monitor the interactions of one such toxin, Cry1Aa with soils and minerals. We have investigated the persistence of the toxin as a function of soil properties and microbial activity and conclude that microbial decay is not the determinant factor in the observed decline of toxin in soil.

Nordine Helassa, Sylvie Noinville, Philippe Déjardin, Jean-Marc Jano, Hervé Quiquampoix, Siobhán Staunton

Microbial and Abiotic Interactions between Transformation of Reducible Pollutants and Fe(II)/(III) Cycles

This study provides fundamental information on the interactions between iron cycles and transformation of reducible pollutants transformation. We introduce 2 cases of microbial and abiotic interactions (

1

) Interactions between reduction of iron oxides and dechlorination of 1,1,1-trichoro-2,2-bis(

p

-chlorophenyl)- ethane (DDT) by dissimilatory Fe(III)-reducing bacterium (DIRB) S12; (

2

) Interactions among CY01, and reduction of iron oxides and reduction of 2,4-dichlorophenoxyacetic acid (2,4-D). We found that the transformation of DDT and 2,4-D could be enhanced in a system of dissimilatory iron-reducing bacteria and iron oxides. This contribution demonstrated the important role of DIRB and Fe(II)/Fe(III) cycles on the transformation of pesticides under anaerobic environments, and provided scientific information for in-situ bioremediation of pesticide pollutants in Fe(III)-rich environments.

Fangbai Li, Shungui Zhou, Xiaomin Li, Chunyuan Wu, Liang Tao

Assessment of Availability of Phenanthrene and Pyrene in Aging Soil

The availability of polycyclic aromatic hydrocarbons (PAHs) in aging soils has not been well elucidated. In this study, sequential extraction was utilized to evaluate the availability of phenanthrene and pyrene as representative PAHs in four typical zonal Chinese soils with aging period for 16 weeks. The tested PAHs were fractionated into two groups: the extractable fractions and bound residues. The former, including desorbing and non-desorbing fractions, is the available fractions in soil that can be taken up by plants and/or soil-inhabiting animals. Both the desorbing and non-desorbing fractions were observed to generally decrease over time, primarily due to microbial biodegradation of the available residues, the desorbing fractions were more readily biodegradable (>91.4% and >71.2% for phenanthrene and pyrene, respectively) than the non-desorbing fractions. Attenuation of the desorbing fraction accounted for more than 92.1% and 76.8% of the observed reduction of the available residues of phenanthrene and pyrene, respectively. The observed concentrations of bound PAH residues were much lower than those of the available residues. In comparison with microbial biodegradation, the transformation of available fractions to bound residues accounted for only a negligible reduction of the available residues of the PAHs tested. These results are useful for risk assessments of PAHs related to human health and environmental contamination.

Wanting Ling, Yuechun Zeng, Yanzheng Gao, Xuezhu Zhu

Levels, Distributions and Profiles of Polychlorinated Biphenyls in Paddy Fields from Two Towns in a Typical Electronic Waste Recycling Area of Eastern China

Surface soil (0∼10 cm) samples from Zeguo and Wenqiao, two towns in a typical electronic waste (E-waste) recycling area of eastern China, were collected and analyzed for polychlorinated biphenyls (PCBs). The mean concentration of total 58 PCBs congeners in Zeguo and Wenqiao were 62.8 and 144.8 μg·kg

−1

(dry weight), respectively, with a range from 13.3 to 242.2, and 27.1 to 526.3 μg·kg

−1

, respectively. The concentrations of total PCBs decreased in the order of paddy fields near E-waste recycling workshops (NEW) > paddy fields near E-waste recycling plants (NEP) > paddy fields in open burning villages (OBV) > paddy fields in other villages (OV). The difference of PCBs composition in OBV or OV areas between Zeguo and Wenqiao indicated that the PCBs concentration in paddy fields were affected significantly by atmospheric transportation and direct discharge. Furthermore, the composition of PCBs in Zeguo and Wenqiao was different, Zeguo soils near the E-waste recycling working plants and workshops contained more high chlorinated PCB congeners and less low chlorinated PCBs compared with Wenqiao soil, possibly indicating the difference of PCBs major source were different. The results of present study suggested that the soil in Zeguo and Wenqiao towns was heavily polluted by PCBs because of E-waste recycling activities. Compared with the large scale E-waste recycling plants, the small simple household workshops have been contributing more PCBs pollution to the soil environment. However, due to the lack of data about the human exposure in this area, it is unconvincing that the analysis of soil samples collected from the crude and inappropriate E-waste recycling area would pose significant threat to human. It is expected to learn much more about the extent and long-term effects of these particular E-waste activities on environmental and human health.

Xianjin Tang, Chaofeng Shen, Wenli Liu, Congkai Zhang, Yingxu Chen

Phytoremediation of Contaminated Soils with Polycyclic Aromatic Hydrocarbons and Its Ecologically Enhanced Techniques

In this paper, a series of research results with respect to the phytoremediation of PAH-contaminated soil were introduced, including the remediation potential of plant species, the utilization of earthworm, the interaction techniques of plants, earthworm and aboriginal microbe, etc.. The results derived from this study may offer an improved knowledge for the scientific evaluation of phytoremediation of PAHs polluted soil.

Shiqiang Wei

The Contribution of Rhizosphere to Remediation of Polycyclic Aromatic Hydrocarbons (PAHs) and Their Toxicity in Soil: Evaluating with Sequential Extraction and Toxicity Risk

To investigate the effects of rhizosphere process on PAHs bioavailability, a sequential solvent extraction experiment was implemented to identify extractable and non-extractable PAHs in rhizosphere and bulk soils of horsebean. The results showed that the primary fraction was methylene chloride (DCM)-extracted and crude-humin-bound PAHs among extractable and non-extractable fractions, respectively. The proportions of sum toxicity concentrations of DCM-extracted fraction decreased sharply in rhizosphere. The partial least square regression model indicated that the partition tendency of PAHs to plant tissues was similar with that to organic Cenriched humin. The contribution of absorption of plant to PAHs remediation, however, can be neglected comparing with that of soil. In conclusion, rhizosphere poses a vital contribution to PAHs remediation in soil, especially when evaluating with toxicity risk.

Bin Ma, Huaihai Chen, Yan He, Jianming Xu

Spectral Studies of the Toxin of Bt Adsorbed by Minerals

The persistence of the toxin of

Bacillus thuringiensis (Bt)

may constitute risk to the soil ecosystem, and toxin structure in soils could affect their persistence, insecticidal activity, and decomposition. The structural changes of

Bt

toxin during adsorption and desorption on montmorillonite, kaolinite, goethite and silicon dioxide were investigated by infrared spectroscopy (IR) and fluorescence spectroscopy. A comparison between the IR spectra of native toxin and toxin-mineral complexes indicated no obvious structural changes appeared, and the C-N radicel played a key role on the adsorption of the toxin by minerals. Fluorescence spectroscopy showed that two fluorescence peaks of the

Bt

toxin were at 338 nm and 314.5 nm by the excitation at 282 nm, which attributed to tryptophan and tyrosine residues, respectively. The maximum fluorescence emission (λ

em

, 338 nm) of

Bt

toxin desorbed from kaolinite and montmorillonite were red-shifted 5 nm and 9.5 nm, respectively, while λ

em

of

Bt

toxin desorbed from goethite and silicon dioxide did not shift obviously. This investigation may help evaluate the behavior and fate of

Bt

toxins in the soil ecosystem.

Qingling Fu, Hongqing Hu, Shouwen Chen, Li Huang, Qiaoyun Huang, Tongmin Sa

Genotypic Differences in Responses of Wheat (Triticum durum) Roots to Oxytetracycline

A pair of oxytetracycline (OTC)-sensitive (cv. Heyou 1) and OTC-tolerant (cv.Yannong 21) wheat (

Triticum durum

L.) was grown hydroponically to investigate the effects of OTC on morphologic characteristics and loss of membrane integrity of roots. The number, total length, total surface area, and total volume of roots of both tested wheat cultivars were significantly decreased by OTC. The number of roots was more sensitive to OTC than other indicators such as total length, total surface area, and total volume of roots. The inhibitory effect of OTC on root growth was larger in the sensitive cultivar than in the tolerant. The number and the total surface areas of roots were decreased by 89.6% and 75.9% respectively for sensitive cultivar, and only 87.5% and 68.7% respectively for tolerant cultivar. The cell membrane of Yannong 21 roots was more integrative, and was less oxidative damage than Heyou 1 under the stress of OTC. These results suggested that OTC is toxic to wheat, being similar to other organic pollutants such as herbicides. The root number could be taken as the indicator to predict the risk of OTC to plants at the early stage. The risks of OTC to agriculture would be alleviated through planting the OTC-tolerant wheat cultivars in the OTC-contaminated soils.

Zhaojun Li, Xiaoyu Xie, Alin Song, Ruihuan Qi, Fenliang Fan, Yongchao Liang

Dynamics of Dissolved Organic Carbon in the Rhizosphere of Ryegrass (Lolium multiflorum L.) Induced by PCBs Pollution

The objective of this study was to examine ryegrass for phytoremediation of polychlorinated biphenyls (PCBs)-contaminated soils. A rhizobox was designed to allow the harvest of an intact layer of rhizosphere soil from plant root without the removal of the root material itself. Ryegrass was grown under controlled conditions in rhizobox for 45, 90 and 135 days. Results indicated that dissipation of PCBs in the rhizosphere were much higher at various layers compared to the no-plant control soils. The DOC concentrations suggested a trend over time. Dissolved organic carbon (DOC) concentrations at 45 days occurred as high as 11.63 mg·L

−1

in the rhizosphere, then decrease rapidly to 7.86 mg·L

−1

at 90 days after sowing. Finally, there was no significant change from 90 days to 135 days in DOC concentration. Moreover, dissipation rates of PCBs correlated positively with DOC concentrations at 45 days and 90 days after sowing. In this study, an average 6.8% loss of PCBs occurred due to the biotic activity without ryegrass planted.

Na Ding, Malik Tahir Hayat, Yan He, Haizhen Wang, Jianming Xu

Dynamic Behavior of Persistent Organic Pollutants in Soil and Their Interaction with Organic Matter

Persistent organic pollutants (POPs) pose threat to environment because of their potential for longrange atmospheric transport, bioaccumulation and toxicity. The POPs behave dynamically in the environment according to their nature of action like volatilization, sorption, desorptin and transportation from their source of production to some where. These POPs migrate on air currents from warmer regions of the globe towards the colder Polar Regions. Once they reach colder temperatures they condense, precipitate out, and are deposited again on the earth’s surface. Environmental variables like temperature, soil pH, moisture have serious effects on the POPs behavior in the soil. Inorganic minerals also have good interaction with the xenobiotics and play an important role in the transformation of xenobiotics. The manganese and iron oxides and clay minerals (e.g. smectites containing Fe(III)) have well-documented properties to promote the oxidation of a number of organic pollutants. Organic matter is considered the most important factor limiting availability and mobility of POPs in soil and a substantial percentage of the total amount of an organic contaminant applied to a soil may become associated with the humic fraction of that soil. Organic pollutants strongly adsorb to carbonaceous sorbents such as black carbon. In particular, activated charcoal (AC) is known for a strong adsorptive capacity due to its high specific surface area. Adsorption to activated charcoal can render hazardous organic pollutants in soils and sediments less available to organisms and hinder their dispersal into unaffected environments. Some studies also show that some sorbents from natural organic materials, such as peat, soybean stalk and pine needle under superheated temperature/ pressure conditions, for sorption of polycyclic aromatic hydrocarbons (PAHs) in contaminated soils. Natural materials significantly decrease the extractability and bioavailability of PAHs from contaminated soils. Main objective of this review article is to compile some valuable information regarding the existence, dynamic behavior, effect of environmental variables on POPs and their interactions with organic matter.

Malik Tahir Hayat, Jianming Xu, Na Ding, Tariq Mahmood

Effect of Crude Water Extract of Fructus Gleditsiae Sinensis on the Removal of Phenanthrene and Pyrene from Contaminated Soils

Polycyclic aromatic hydrocarbons (PAHs) in soils can be mobilized by surfactants and other mobilizing agents such as dissolved organic matter (DOM). DOM from

Fructus Gleditsia sinensis

contains a large amount of natural non-ionic surfactant triterpenoid saponins and thus can be considered as a natural complex of general DOM and natural non-ionic surfactants. In this study we use crude water extract of

Fructus Gleditsiae Sinensis

Lam. (CWE-FGS) as a removal agent with no purification procedure to investigate the possibility of developing a more green and more cost effective remediation agent that may compete for the chemically synthesized “manmade” surfactants or purified or partially purified natural biosurfactants. Results showed that the removal rates of phenanthrene and pyrene from contaminated soils by 5% of CWE-FGS were 59% and 52%, respectively. The removal capacities of Tween 80 and rhamnolipids for PAHs from contaminated soils were also studied for comparison. The removal capacity of CWE-FGS for PAHs from contaminated soils was lower than that of Tween 80, but higher than that of rhamnolipids. Thus, it can be safely conclude that CWE-FGS can be a potential natural remediation agent for PAHs from contaminated soils.

Ran Wei, Jun Wang, Hongyu Yang, Yi Chen, Peifen Liu, Jinzhi Ni

Distribution Pattern, Sources and Potential Risks of Polycyclic Aromatic Hydrocarbons in Urban Soils of Fuzhou City, China

Polycyclic aromatic hydrocarbons (PAHs) were analyzed in 64 surface soil (0∼5 cm depth) samples collected from Fuzhou city, China. The sampling sites were randomly selected from various functional zones including parks, colleges and universities, residential areas, agricultural fields, industrial areas, and gas stations. Total PAHs (ΣPAHs) concentrations ranged from 14.0 to 5442.9 μg·kg

−1

with a mean of 578.1 μg kg

−1

. The mean concentration of ΣPAHs in soil samples from different functional zones decreased in the order of gas stations (1140.9 μg·kg

−1

) > industrial areas (1131.6 μg·kg

−1

) > agricultural fields (514.3 μg·kg

−1

) > residential areas (393.3 μg·kg

−1

) > colleges and universities (245.8 μg·kg

−1

) > parks (222.0 g·kg-1). The calculated PAH isomer ratios indicated that pyrogenic origins such as motor vehicle exhaust, industrial activities and coal burning were the dominant sources. The total carcinogenic potency for each sampling site was calculated using toxicity equivalency factors (TEFs) to convert concentration of individual PAH to an equivalent concentration of benzo[a]pyrene (BaP

eq

). Comparing with the reference total carcinogenic potency calculated as a sum of Dutch target value for unpolluted soil with appropriate BaP

eq

, above 42% soil sampling sites in this study, especially for the sampling sites of gas stations, had certain potential ecological risks to human health.

Jinzhi Ni, Xiaoyan Li, Juan Guo, Jun Wang, Hongyu Yang, Ran Wei

Thermal Degradation of Chloroteracycline in Animal Manure and Soil

Veterinary antibiotics used in livestock and poultry production may be present in manure and slurry as the parent compound and/or metabolites. The environment may therefore be exposed to these antibiotics due to the application of animal manure to agricultural land. In order to reduce the amount of veterinary antibiotics ultimately released into the environments, it is necessary to treat properly animal manure before its application in agricultural land. In this paper, the effect of temperature on degradation of chlortetracycline (CTC) in animal manure and soil was investigated under laboratory conditions. Degradation of the CTC in both animal manure and soil under different temperature conditions followed first-order kinetics. Increasing temperature greatly accelerated CTC degradation, and thermal degradation became significant at high temperature (>30 °C). The degradation rate of the CTC was faster in animal manure than manure-amended soil and soil, suggesting that CTC may become persistent in the environment once it was released from manure into soil.

Mingkui Zhang, Huimin Zhang

Enhancement of Atrazine Degradation in Paddy Soils by Organic Amendments

The effect of three organic amendments, e.g. decomposed pig manure, rice straw and Chinese clover, on soil microbial biomass carbon content (SMBC) and the degradation of atrazine in three paddy soils spiked with atrazine at a rate of 10 mg·kg

−1

soil were studied. The results showed that SMBC significantly (

P

<0.01) increased with the application of organic amendments in all three soils. The largest increment of SMBC was observed in the treatment of decomposed pig manure, followed by addition of Chinese clover, and the smallest increase occurred in the application of rice straw. The dissipation of extractable atrazine was significantly enhanced by the organic amendments. Compared with the unamended treatment, the average half-life of atrazine in soil was reduced by 2, 1.6, and 1.4-fold in the treatments with decomposed pig manure, Chinese clover and rice straw, respectively. These results suggest that application of organic fertilizers in paddy fields may significantly alter soil microbial communities and affect the fate of agrochemicals such as atrazine. As the use of organic wastes is an important practice in rice production in many regions in Asia, such interactions should be considered when evaluating the fate and risk of pesticides in the environment.

Chaolan Zhang, Jianming Xu, Bin Yao

Environmental Nanoparticles: Distribution, Formation, Transformation, Structural and Surface Chemistry, and Biogeochemical and Ecological Impacts

Frontmatter

Soil Science at the Nanoscale: A New View of Structure, Stability, and Reactivity

A revolution is occurring in science and technology as new methods and approaches allow scientists and engineers to investigate materials and processes at the nanoscale and to engineer new nanomaterials. Materials from ∼1 to 100 nm in size, where 1 nanometer = 10

−9

m, or 10Å, are generally considered to be nanomaterials. Nanomaterials are uquitous in near-Earth-surface environments, and often have properties that are distinct from those of single, small molecules or of larger, bulk materials. Many of the key components of soils, such as humic substances; iron, aluminum, and manganese oxides; and aluminosilicate clays may occur as nanoparticles or with nano-scale components or domains.This presentation will define terminology in the field of nanoscience and nanotechnology as applied to soil science, and will describe some of the special properties and behaviors of nanomaterials in soils, drawing primarily from examples of Fe (hydr)oxides. The presentation will emphasize the importance of nanoscience as a new frontier in soil science, along with how the unique experience of soil scientists can benefit broader nano-scale research.

Patricia A. Maurice

Environmental and Colloidal Behavior of Engineered Nanoparticles

Engineered nanoparticles (ENPs) are increasingly used in various industries and can be readily found in the products surrounding our everyday life. They are increasingly attracting attention from scientists, government regulators, and the public due to the concern over their potential toxicity and harms. Because of the widespread use of ENPs, they are most likely to release into the environment; however, scientific understanding on their environmental fate and behavior is very limited. Therefore, environmental and colloidal behaviors of carbon nanotubes (CNTs), fullerene, and oxide nanoparticles were examined using various spectroscopic and microscopic techniques. CNTs could greatly adsorb organic contaminants including PAHs and endocrine disrupting compounds, which may affect the toxicity and fate of both CNTs and organic contaminants in the environment. Adsorption mechanisms are also discussed. Dissolved organic matter (DOM) is able to adsorb on both CNTs and oxide ENPs, thus could increase their dispersion and suspension stability. Preliminary data demonstrate that oxide ENPs are more toxic than their bulk counterparts to nematode (

C. elegans

) and three bacteria species. Also, ZnO ENPs could inhibit plant growth and may be taken up by plant. This work highlights the importance of a better understanding of environmental impact of ENPs and calls for safe design, development, and use of nanoparticles.

Baoshan Xing

Humic Substances as Natural Nanoparticles Ubiquitous in the Environment

Humic substances (HS) are recognized to be the most widespread and ubiquitous components of natural nonliving organic matter (NOM) in the global environment. The estimated level of soil organic carbon (SOC) on the earth surface occurring as HS is 30 × 10

14

Kg. In particular, approximately 60%∼70% of the total SOC has been estimated to occur in HS. These substances consist of a physically and chemially heterogeneous mixture of relatively high-moleular weight, yellow to black organic compounds of mixed aliphatic and aromatic nature, formed by secondary synthesis reactions (humification) of products of the microbial and chemical decay and transformations of biomolecules released from organisms into the surrounding environment both during life and after death. The HS are universally recognized as the most relevant and chemically, biologically and physically active components of NOM thanks to their typical composition, macromolecular structure, polyfun-tionality, surface properties, presence of multiple reactive sites, variable sizes and shapes, and intrinsic porosity.

Nicola Senesi

Degradation of Organochlorine Compounds Using Zero Valent Iron (ZVI) Nano Particles Impregnated in Hydrophobic Modified Bentonite

The degradation of perchloroethylene (PCE) adsorbed on hydrophobic modified bentonite was investigated. The degradation occurred via reduction of iron particles with zero valence (ZVI) incorporated in hydrophobic surface of bentonite. We compared two different systems, one containing ZVI and another without ZVI. The degradation of PCE was accompanied by decreasing concentrations of PCE and the increase of resulting compounds such as trichloroethylene (TCE), 1,2-dichloroethylene, trans and cis forms, (1,2-cis-DCE and 1,2- trans-DCE). The results show that the PCE is rapidly adsorbed and in contact with ZVI particles is degraded to less toxic compounds, while in the systems without ZVI no significant decrease of PCE was observed, clearly demonstrating that the degradation process occurs through the reduction with ZVI. The rate constant for the system containing ZVI was 0.215 h

−1

, while for the system without ZVI it was only 0.031 h

−1

. The results agree with other research, however the reaction was conducted in columns and the clay was zeolite. It can be concluded that the system impregnated with ZVI is extremely interesting as an alternative application for removal of organic compounds containing chlorine due to their persistence and toxic effect on the microorganisms. The system can also be applied as barrier content.

Sandro Froehner, M. Maceno, E. C. Da Luz, K. S. Machado, F. Falcão

Effect of Electrolyte on Adsorption/Desorption of Cu2+ on Nano-particle Mn Oxide

Oxides are the active and important component in soils and sediments. They are generally in fine particles and attached to surface of soil clay as a cutan or coating. Therefore, they play an important role in controlling chemical reactions of soil interface, and thus affect bioavailability and transformation of heavy metals in soils and sediments. At the common pH range of the natural environment, Fe and Al oxides possess positive charge. The adsorption amounts of heavy metals on Fe and Al oxides increased and their desorption percentage decreased with increasing ionic strength. However, Mn oxide has a low point of zero charge (PZC) and thus displays negative charges in the natural environment. It is unclear how electrolyte affects adsorption-desorption by Mn oxides. This paper studied the influences of electrolytes (KNO

3

, KCl) on Cu

2+

adsorption and desorption on synthetic birnessite. The PZC and specific surface area (SSA) of birnessite was 2.5 and 75 m

2

·g

−1

, respectively. The birnessite consisted of clusters or ball-like aggregates with a size of 50∼100 nm. The pH of birnessite in suspension increased slightly with increasing electrolyte concentration, but the effect of KCl solution was higher than in the effect of KNO

3

at a given concentration. The amount of Cu

2+

absorbed on birnessite decreased gradually with increasing ionic strength. However, the desorption percentage of Cu

2+

absorbed on birnessite surface increased with increasing electrolyte concentration. Furthermore, the desorption percentage of Cu

2+

was higher in KCl solution than in KNO

3

solution. These results are different from the adsorption/desorption of Fe and Al oxides.

Wenfeng Tan, YuanPeng Wang, Fan Liu, Xionghan Feng

Sorption of Selected Organic Compounds in Two Black Carbon Particles

Black carbons (BCs) have been reported to exhibit an extremely strong sorption of organic compounds in the environment. The basic physicochemical properties of two selected black carbons characterized and showed mainly non-polar. The polarity of BC1 was slightly higher than BC2. Sorption coefficients of selected organic compounds on two BCs were investigated by a reversed-phase liquid chromatography (RP-LC) method. Sorption coefficients of organic chemicals on BC1 were larger than those on BC2 because BC1 had more surface area. Normalized surface area sorption coefficients of BC2 were larger than those of BC1, indicating that not only surface area but surface heterogeneity is also responsible for the resulting sorption capacity. By the regression of the sorption coefficients of organic compounds on these black carbons with the properties of organic compounds, two linear solvation energy relationship (LSER) equations were obtained. The main interactions involved in the adsorption process are generally London dispersion forces and π- and n- pair electron interactions. These LSERs can facilitate to predict the adsorption coefficients and evaluate the sorption mechanism of organic contaminants on black carbons through the molecular properties of sorbates and sorbents.

Yang-hsin Shih, Po-Hsin Su

Adsorption and Inhibition of Butyrylcholinesterase by Different Nanoparticles

Nanoparticles may have potential neurotoxicity. This study used 5 nanoparticles including 2 metal nanoparticles and 3 oxide nanoparticles to test their adsorption and inhibition on BChE. We used a modified Ellman method to measure BChE activity. At 800 mg · L

−1

, the adsorption and inhibition of BChE by Cu were the highest, 54% and 86%, respectively. While Al nanoparticles showed the lowest adsorption (6.8%) and inhibition rates (3.3%). Inhibition was caused mainly by the adsorption of BChE on tested nanoparticles and partly by ions released in nanoparticle suspensions. Inhibition of BChE by Cu

2+

ions was higher than 39%. Other ions had slight or little effect on BChE activity. The contribution of ions to nanoparticle inhibition followed a decreasing sequence of Al (66%)>Cu (46%)>Al

2

O

3

(44%)>SiO

2

(4%). Our results indicate that these nanoparticles may have neurotoxicity.

Zhenyu Wang, Kai Zhang, Jian Zhao, Fengmin Li, Dongmei Gao, Baoshan Xing

Characterization of Soil Clay Minerals Using Mid-infrared Spectroscopy

Clay mineral is one of the most important components in soil, and the characterization of soil clay is very useful to study the interactions between soil clay and soil organic materials. Chemical analysis of soil clay is time-consuming, while the infrared spectroscopic method seems promising. In this research, the characterization of three source clay minerals, i. e. illite, kaolin and montmorillonite, were analyzed using three mid-infrared spectroscopic techniques (attenuated total reflectance (FTIR-ATR), transmittance spectroscopy, and photoacoustic spectroscopy (FTIR-PAS)). For the FTIR transmittance spectra of the three source clays, there were three main absorption regions: 2600∼3800 cm

−1

, 1300∼1800 cm

−1

, and 500∼1200 cm

−1

, and sharp differences could be found in each region; for the FTIR-ATR spectra of the three source clays, there were absorptions with minor difference in the region of 800∼1200 cm

−1

; for the FTIR-PAS spectra of the three source clays, there were also three similar absorption regions as FTIR transmittance spectra, but more absorptions were found in the FTIR-PAS spectra comparing with FTIR transmittance absorptions. Comprehensively, FTIR-PAS spectroscopy showed more merits in the characterization of soil clays among the three infrared spectroscopic techniques. The FTIR-PAS was applied to charactrize three soil types, and the interactions between soil clay and soil organic materials could be studied using the step-scaning function of FTIR-PAS.

Changwen Du, Guiqin Zhou, Jing Deng, Jianmin Zhou

Investigation Mechanism of MTBE on Wall of Carbon Nanotube (CNT) to Other Products from Air-groundwater (in Environment): MNDO

Gasoline and heating oil travel through pipelines and are also distributed by truck to above ground and underground storage tanks. Through its extensive use as a fuel oxygenate, methyl tert-butyl ether (MTBE) is found nearly ubiquitously throughout the environment. MTBE, a widely used gasoline additive, is recently being scrutinized for potential environmental damage in groundwater and in the atmosphere. The calculations have quantum mechanical detail and are based on a semi-empirical (MNDO method), which is applied to the evaluation of both the electronic structure and of the conductance. We study the structural, total energy, thermodynamic and conductive properties of absorption MTBE on CNT, which convert to CO and H

2

O.There are four situations for MTBE near by SWNT that we have investigated adsorption it on CNT and is converted to other products. The properties thermodynamic are calculated for them.

Leila Mahdavian, Mahmoud Raouf

Extraction of Nanoparticles from Argosols and Ferrosols

Soil nanoparticles are ubiquitous and play an important role in migration and transformation of pollutants in nature. The present study was aimed to obtain soil nanoparticles from Argosols and Ferrosols, which are two typically zonal soils distributing in the north and south China, respectively. Ultrasonic-centrifugal method was used to disperse the soil and extract soil nanoparticles. The nitrogen adsorption-desorption method was employed to determine the specific surface area of soil nanoparticles. More soil nanoparticles were obtained from Argosols than from Ferrosols. The soil nanoparticles from Argosols could not, however, keep stable in water even at 4 °C. To preserve in solid, it should be freezing dried immediately. Furthermore, the nanoparticles from the two soils were different in the physical characteristics including fractions and morphology. After ultrasonic extraction, the specific surface area of two soils had increased nearly four times.

Wenyan Li, Jianming Xu, Pan Ming Huang

Surface and Adsorption Characteristics of Black Carbon from Different Sources

Two black carbon (BC) samples, new BC and soil BC isolated from the burning residues and soil repectively, were characterized for their surface areas, surface acidity, zero point of charge, and adsorption capacity for metal (Cu) and organic pollutant (oxytetracycline). Compared with new BC, soil BC had a low surface area but a high surface acidity and thus a low isoelectric point. Soil BC had a stronger capacity for adsorbing Cu(II), but less for oxytetracycline. This study demonstrated that BC may be an important adsorbent of heavy metals and organic pollutants in soil, and the adsorption capacity of BC may be significantly influenced by soil environmental conditions where BC was formed.

Mingkui Zhang, Zhaoyun Liu

A High-resolution TEM Investigation of Nanoparticles in Soils

Soil nanoparticles are nanometer-sized (−1∼100 nm) crystalline to amorphous solid material formed in soil environment. It is now possible to understand their very interesting structure and properties using techniques developed for nanotechnology such as transmission electron microscopy. Structures and chemical composition of nanoparticles in red soil (Ultisol) were studied by high-resolution transmission electron microscopy (HRTEM), electron diffraction and elemental analysis (EDX). Electron-dense, well crystalline iron oxide nanoparticles were identified. The iron oxide phase usually coated and/or embedded on the surface of larger size aluminosilicate phase. High-resolution studies using HRTEM and EDX of nanoparticles in soil have a great potential for understanding physical properties, chemical reactivity and environmental processes of nanoparticles in the soils.

Rui Zhu, Shenggao Lu

Adsorption and Desorption of Tylosin on the Colloidal Fractions of Black Soil

Adsorption and desorption of tylosin on different colloidal fractions from Black soil were studied. The adsorption isotherms of tylosin conformed to the Langmuir equation. The amount of Tylosin adsorbed followed the order: fine organic clay > fine inorganic clay > coarse organic clay > coarse inorganic clay. Marked decreases in the adsorption of tylosin on soil colloids were observed in the presence of Na

+

and Ca

2+

ions, and the influence of Ca

2+

was stronger than that of Na

+

. The sorbed tylosin on soil colloids was sequentially desorbed by 10 mmol · L

−1

Tris, 100 mmol · L

−1

NaCl and 100 mmol · L

−1

phosphate solutions at pH 7.0. The percent desorption by Tris and NaCl was 79%∼105%, showing that electrostatic interaction played an important role in the adsorption of tylosin by soil colloidal components.

Chunhong Wang, Aifang Xue, Wei Liang, Peng Cai, Qiaoyun Huang

Environmental Processes and Ecosystem Health

Frontmatter

Spatial and Temporal Dimensions of Environmental Processes in Soils — An Integrated Approach

We explain the spatial and temporal dimensions of physical, chemical and biological processes in the soil pore space through an integrated approach.

Winfried E. H. Blum

Emission, Fate and Exposure Risk of Polycyclic Aromatic Hydrocarbons in China

An Euler atmospheric transport model was applied to model the near ground atmospheric concentration of polycyclic aromatic hydrocarbons (PAHs) in China based on a high-resolution emission inventory. The results were used to assess inhalation exposure and lung cancer risk of Chinese population. Monte Carlo simulation was conducted to address the uncertainty and variability in exposure concentration, intake rate and cancer risk. Frequency distributions of inhalation rate and lung cancer susceptibility were used for the simulation. For the latter, the frequencies of various genotypes for genes associated with the metabolism of PAHs and DNA repair were collected and a dose-response relationship between the number of at-risk alleles and DNA adduct level was derived from the literature. The distribution of the risk-related genotypes was transformed to the distribution of DNA adduct level as an indicator for individual susceptibility. It was found that the means of the total PAH concentration and banzo[a]pyrene equivalent concentration were 200 (106∼370 as interquartile range, IR) ng · m

−3

and 2.43 (IR 1.29∼4.50) ng · m

−3

, respectively. 5.8% (IR 2.0%∼11%) of territory where 30% (IR 17%∼43%) of population live, exceeded the national standard for PAHs. The calculated extra life-long lung cancer morbidity of Chinese population due to inhalation exposure to PAHs was 51.5×10

(IR 27.3×10

−5

∼95.3×10

−5

). Due to interindividual viabilities in inhalation rate and susceptibility, size of the populations with very low or very high lungcancer risk increased and the size of population with PAH induced extra lung-cancer morbidity greater than 100×10

−5

were 11% (IR 3.3%∼24%) and 22% (IR 15%∼32%) with or without taking the inter-individual viabilities into consideration.

Shu Tao, Yanxu Zhang

How Do Microbial Extracellular Enzymes Locate and Degrade Natural and Synthetic Polymers in Soil

In soils, microorganisms encounter complex organic matter that is rich in the energy, carbon and nutrients that are required for cell maintenance and growth. Cellulose and lignin are two of the most abundant biopolymers. However, bacteria and fungi do not have the ability to transport these into the cytoplasm; instead they depend on the activity of enzymes that are secreted into their immediate environment. These extracellular catalysts decompose organic compounds and generate soluble chemicals that are recognized by cell wall receptors and transported into the cell. Many organic pollutants in soil are polymeric, and poorly soluble and these also require extracellular catalysis prior to uptake, metabolism and detoxification. The complexity and diversity of extracellular enzymes and the macromolecules that they degrade will be reviewed and the many locations and multiple fates of these enzymes discussed. Ways in which extracellular enzymes overcome the destructive or inhibitory properties of the soil matrix and various strategies they adopt for effective substrate detection and utilization will be described.

Richard G. Burns

Influence of Solution Composition on the Exfoliation of Organic Matter from a Model Soil System

It has recently been demonstrated that small perturbation of hydrophobic interactions and hydrogen bonding via small changes in solution composition can greatly alter the conformation of dissolved organic matter. This work investigates if the same holds for in-situ soil organic matter (SOM) by exfoliating it with solvent systems (SSs) of different compositions. The effects of aqueous solutions composed of 4.6 × 10

−3

mol·L

−1

acetic acid (AA), acetonitrile (ACN), dimethyl sulfoxide (DMSO), hydrochloric acid (HCl), and methanol (MeOH) as well as 18 MΩ H

2

O were investigated. Only the ACN SS showed marked difference in the amount and type of organic matter exfoliated compared to that exfoliated by H

2

O only, as monitored by UV/Vis absorbance, fluorescence, attenuated total reflectance Fourier transformed infrared (ATR-FTIR), and

13

C cross polarization magic angle spinning (CP-MAS) spectroscopy. It was found that after 20 days the ACN exfoliation solution had turned brown while the other solutions remained yellow, and that this color change could be attributed to more of the humified materials being exfoliated. It was also found that an additional 25 days allowed for a larger amount of the less humified material to be subsequently exfoliated. Based on these findings, a solvation model is put forward along with an explanation for the differences seen for the ACN SS. Both are relevant to hydrophobic organic compound sorption, remediation, and soil wetting processes.

Charisma Lattao, Robert L. Cook

Transfer of Soil Nickel to Crops in Suburban Areas and Their Healthy Risk in Fujian Province, Southeast China

To understand the bioavailability and soil-to-plant transfer of nickel (Ni), rice and 20 commonly consumed vegetable species with their corresponding soil samples were collected from the suburban areas of some major cities of Fujian Province. The total concentrations of Ni in soil ranged from 1.41 mg·kg

−1

to 79.24 mg·kg

−1

with a mean of 17.05 mg·kg

−1

. Both the DTPA-extractable Ni and the available Ni fractions were significantly correlated with the total Ni, pH, free Fe and clay. The Ni concentrations in the edible parts of the crops varied from not detected to 3.685 mg·kg

−1

with a mean of 0.221 mg·kg

−1

(fresh weight). The Ni concentrations of 5 crops showed significant correlations with total soil Ni while those of 10 corps were significantly correlated with DTPA-Ni. The transfer factors based on DTPA-Ni (TFDTPA) of crops varied between 0.001 and 2.478. In general, the TF

DTPA

of the crops decreased in the order of beans > gourds > rice > leafy vegetables. Daily consumption of rice and some Ni-rich vegetables could result in an excessive intake of Ni, according to the reference dose (RfD) of Ni recommended by USEPA.

Dan Luo, Yanhui Chen, Guo Wang

Transformation Dynamics and Memory Effect of Soil Amino Sugars Amended with Available Substrates

Combination of the isotope tracing technique and the identification of amino sugars is efficient to explore the microbial immobilization of extraneous nitrogen. In the present study, the transformation dynamics and memory effect of soil amino sugars amended with available substrates were investigated. The results showed that the compound-specific

15

N enrichment represented the transformation pattern of individual amino sugars and the calculated

15

N-labeled portion was derived from the immobilization of the extraneous NH

4

+

. The

15

N enrichment in glucosamine was increased slowly and the unlabeled glucosamine was quite stable during the accumulation of newly-synthesized portion. The transformation of muramic acid was more rapid than glucosamine in short term, but the formation of

15

N-labeled muramic acid was concomitant with the decomposition of inherent portion. It was indicated that bacteria were more competitive than fungi to assimilate liable substrates initially, but fungus growth was dominant at later stage by utilizing the intact or metabolized substrates. Furthermore, bacterial cell wall residues were easily decomposed to be involved in the soil organic matter (SOM) turnover, while fungus-derived residue was mainly contributed to the stabilization of SOM.

Hongbo He, Xudong Zhang

Evaluating the Maturity and Quality of Solid Waste Compost through Phospholipid Fatty Acid Biomarkers

Maturity and quality of compost when used as soil amendment are very important and need to be taken into consideration. Phospholipid fatty acids (PLFAS) composition has high correlation with chemical and biological parameters for compost maturity. This study was undertaken for making compost from sewage sludge and municipal refuse with some additives to enhance decomposition. The municipal solid waste(MSW) was mixed with equal weight of de-watered sewage sludge(DSS), and then treated with these additives in separate bioreactors as: control (no amendment), zeolite, clayey soil, fly ash, lime, and effective microorganisms (EM) inoculum. Composts were analyzed for C:N ratio and microbial diversity during decomposition. Thirty nine types of PLFAs were identified, which belonged to nine major categories. Results from all the treatments depicted that straight, monounsaturated fatty acids (SMUFA) and straight, saturated fatty acids (SSATFA); SSATFA both representing for fungi were in the highest amount. These were followed by branched, saturated fatty acids (BRANCHED FAMES) that signify the presence of G +ve bacteria and actinomycetes. The straight, hydroxyl fatty acids (SOH-FAMES) specifying the anaerobic microbes were the lowest among all. A small number of aerobic G -ve bacteria was also noticed by the presence of branched, saturated, and hydroxyl fatty acids (BSHFA) and cyclopropyl fatty acids. The C:N ratio was at the lowest with EM that enhanced decomposition more than with other amendments. The EM as well as lime increased the concentration of all the PLFAs as compared with control. Therefore, both EM and lime can be the best choice amendments for rapid composting leading to early maturity and better quality of the compost product.

Ghulam Jilani, Jianming Xu, Yuping Wu, Zhongzhen Liu

Effects of Depleted Uranium on Soil Microbial Activity: A Bioassay Approach Using 14C-labeled Glucose

The short and long term influence of depleted uranium (DU) on soil microbial populations remains largely understudied. To understand short term effect of DU on soil microbial activity, an incubation study was conducted using

14

C-labeled glucose. Two soils of contrasting texture (Eurtic cambisol and Haplic podzol) were amended with increasing concentrations (0.5 mmol·L

−1

to 10 mmol·L

−1

) of either potassium nitrate (KNO

3

) or DU as uranyl nitrate UO

2

(NO

3

)

2

. Following addition,

14

C-labeled glucose was then added to the soil and

14

CO

2

production from the mineralization of glucose measured at different time intervals (1 h to 14 d) to assess microbial activity. Glucose mineralization by the microbial community showed non-significant effect by different concentrations of DU on both soils. Fitting a double first order kinetic equation revealed that 87%∼92% of the added glucose was retained in the microbial biomass prior to mineralization. However, comparison of the kinetic values for different concentrations of KNO3 and DU also showed non-significant difference in both soils. The results imply that there is no significant deleterious effect of DU on soil microbial activity in the short (<24 h) or longer term (<30 d).

Rizwan Ahmad, David L. Jones

Is the Alkalinity within Agricultural Residues Soluble

A laboratory experiment was carried out to determine the contribution of whole residues of canola, chickpea and wheat and their fractions (insoluble/soluble) to soil pH changes during a 14-day incubation. Residues were added (1% w/w) to Frankston and Shepparton soils of initial pH of 4.45 and 6.20, respectively. Increases in pH were greatest for chickpea, less for canola and the least for wheat. The experiment confirmed that the soluble fraction of residues is important for the alkalinity release within initial stages of decomposition and also the source of components responsible for pH decreases in subsequent incubation. However, the relative differences of whole residues and the fractions were influenced by the initial soil pH.

Clayton R Butterly, Jeffrey A Baldock, Jianming Xu, Caixian Tang

Soil Micro-interfaces Control the Fate of Pollutants in Soil Environment

Environmental soil micro-interfaces are the collection and continuum of surfaces of soil clay minerals, oxides, organic matters, plant roots and microbes. The soil colloidal interfaces could be simply described as a diffuse electrical double-layer structure on the interface of soil particles and solutions. These heterogeneous micro-interfaces can be divided into three types based on their surface structure characterizations: siloxane, hydrous oxide and organic matter surfaces. The transport, transformation and degradation of pollutants in the soil are dynamic processes, including a series of reactions of sorption/desorption, precipitation/dissolution, complexation/chelation, and oxidation/reduction. Rhizosphere interface is the most active area in soil-plant ecosystems with intensive interactions among soil particles, organic compounds, plant roots and microorganisms. It is the channel of pollutant transporting to plants and linking with food chain. Microbial interface plays important roles not only in sorption and redox reactions of heavy metals, but also degradation and transformation of organic pollutants. As a dynamic continuum, different soil heterogeneous micro-interfaces interact with each other and control the forms, bioavailability, toxicity, transformation (degradation) and transport of pollutants in soil-plant ecosystems. Therefore, they are of significance in soil pollution control and remediation.

Jizheng He, Yuanming Zheng

Soil Microbial Biomass and pH as Affected by the Addition of Plant Residues

The soil microbial biomass is involved in the decomposition of organic materials and thus, the cycling of nutrients in soils. Reductions in the size and activity of the microbial biomass are frequently used as an early indicator of changes in soil chemical and physical properties resulting from management and environmental stresses in agricultural ecosystems. In a laboratory-incubated soil, we found a strong relationship between microbial biomass C and microbial biomass N. Irrespective of the type of plant residues added, soil pH was significantly correlated with microbial biomass C and microbial biomass N. Different C/N ratio of the residues was the main characteristic that affected soil microbial biomass C, N and soil pH. Microbes played a main role in plant residues decomposition and indirectly influenced of soil pH.

Yunfeng Wang, Ling Zhou, Jianjun Wu, Clayton R Butterly, Caixian Tang, Jianming Xu

Changes of Soil Enzyme Activities in the Process of Karst Forest Degradation in Southwest China

Sample plots (15 m × 20 m) were set up in the karst areas in Guizhou Province with an attempt to reveal the changes of soil enzyme activities under karst forest degradation. The results showed that the extent of degradation of plant communities was enhanced leading to the clayification of soil, the drastic decrease in SOM contents, and the reduction of soil nutrients available for plants. The urease activities, peroxidase activities and alkaline phosphatase activities of the soils had also decreased significantly.

Fang Liu, Shijie Wang, Xiuming Liu, Yuansheng Liu, Jian Long

Effect of cry1Ab Gene Transformation on the Microbial Mediated Decomposition of Rice Residues under Intensive Rice Cropping System

Although genetically modified (GM) plants can offer many benefits, the planting of transgenic crops has raised a number of concerns, including the ecological impact of these plant residues on soil ecosystems. In this study, the effects of rice expressing the

Bacillus thuringiensis

Cry1Ab protein (

Bt

rice) on the residue decomposition processes were assessed in comparison with parental rice variety (non-Bt rice) under rapeseed-rice cropping system and surface or incorporated placement conditions. Bacterial and fungal communities associated with residue decomposition were studied by terminal restriction fragment length polymorphism (T-RFLP) method and additive main effects multiplicative interaction (AMMI) analysis model. After 276 days and residue decomposition in the field condition, bacterial and fungal communities associated with decomposition were strongly affected by the temporal factor which represented the grouping of T-RFLP fingerprint according to the time factor alone IPC 1. The placement effect on soil bacterial and fungal communities was also detected which represented the grouping of T-RFLP fingerprint alone IPC 2. Although some differences were found between Bt and non-Bt rice varieties in some special stages and placements, the impact of

cry1Ab

gene transformation on microbial mediated decomposition was lower than temporal and placement factors.

Haohao Lu, Weixiang Wu, Yingxu Chen

Characterization of Microbial Community and Phosphorus-releasing Bacteria in the Sediments of a Eutrophic Shallow Lake, Eastern China

To understand the interactions between phosphorus (P) and microbial community and characterize some P-releasing bacteria, ten representative sediment samples were collected in a small eutrophic lake and a clean wetland. Total P concentration in wetland sediment was much lower than that in the lake, while NaOH-extractable P was relatively high in wetland which indicated high releasable risk. According to Standards Measurements and Testing Program of the European Commission (SMT protocol), P in lake rooted in agricultural runoff and P in wetland was mainly of anthropogenic origin, and the microbial communities were significantly different between these two kinds of sediment. Enumeration of inorganic P-releasing bacteria (IPB) and organic P-releasing bacteria (OPB) showed these groups were not very rich in the ecosystem. Molecular identification indicated there were various kinds of bacteria involved in the P transition cycle, but the P release abilities of different bacteria were dissimilar.

Yichao Qian, Yingxu Chen, Jiyan Shi, Liping Lou

Carbon Compounds Differ in Their Effects on Soil pH and Microbial Respiration

The mechanisms of soil pH change after the addition of organic matter to soil are not fully understood. The aim of this study was to investigate changes in pH after addition of carbon compounds over a 60-d incubation period. Seven organic compounds commonly found in plant residues (acetic acid, malic acid, citric acid, benzoic acid, ferulic acid, glucosamine hydrochloride and glucose) were selected based on the number and type of functional groups, and added at 0.5 mg C·g

−1

soil to two soils differing in initial pH. Addition of organic acids (R-COOH) immediately decreased pH. The magnitude of the pH decrease depended on dissociation constant of the acid and the initial soil pH. In subsequent incubation, pH was slowly returned to original levels as organic anions were mineralized, consuming H

+

ions. Glucose which contains hydroxyl (R-OH) group did not alter soil pH. However, carboxyl (R-COOH) and amine (R-NH

2

) groups changed pH significantly. Soil respiration was also increased by the addition of C compounds. Cumulative respiration was higher in soil with malic acid, citric acid, ferulic acid and glucose than with other compounds. The addition of glucose, citric acid and malic acid resulted in priming as cumulative respiration was greater than the actual amount of C added.

Fatima Rukshana, Clayton R Butterly, Jianming Xu, Jeffrey A Baldock, Caixian Tang

Effects of Soil Water Content on Soil Microbial Biomass and Community Structure Based on Phospholipid Fatty Acid Analysis

Three different kinds of soils collected from Heilongjiang, Jiangsu and Guangxi province of China were used to test the effects of different water contents on soil microbial biomass and community structure. Soils were moistened to 40%, 60% and 80% of water holding capacity (WHC) first. Then the moist soils were incubated in the dark room at 25° for 56 days. Phospholipd fatty acid (PLFA) analysis were carried on days 0, 3, 7, 14, 28 and 56 to track the changes of soil microbial organisms. The results showed that soil microbial biomass and community structure based on PLFA analysis did not response to the different soil water contents. Soil microbial organisms might get used to a wide range of soil water contents.

Yuping Wu, Yan He, Haizhen Wang, Jianming Xu

Effects of Cadmium and Mercury alone and in Combination on the Soil Microbial Community Structural Diversity

To assess effects of cadmium (Cd) and mercury (Hg) alone and in combination on soil microbial community structural diversity, an incubation experiment was conducted, employing two soils, namely, the marine sediment silty loam soil and the yellowish red soil, in which five levels of Cd, Hg or Cd and Hg in combination were added. After incubated 56 days, phospholipid fatty acids (PLFAs) were tested. The results showed that the composition of the microbial communities changed significantly after different levels of metals application. The principal component analysis (PCA) of PLFAs indicated the structure of the microbial community was also significantly influenced by the pollution of metals, with the increases in PLFAs biomarkers for fungi and actinomycetes, and the increases in the ratio of Gram-positive to Gram-negative bacteria. By comparing the effects of Cd, Hg alone and in combination, the results revealed that the combined pollution of Cd and Hg had higher toxicity to soil microbial community structural diversity than that of Cd or Hg applied alone.

Min Liao, Haijun Zhang, Shouna Yu, Chengli Chen, Changyong Huang

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