Biogeochemistry of Ancient and Modern Environments

Biogeochemical systems are a product of the interacting evolutions of biosphere, atmosphere, hydrosphere, and lithosphere. They began with the appearance of life on Earth. But the appearance of objects we would unhesitatingly pronounce to be living is itself presumably only the end stage of a transitional process whose nature and antecedents are important parts of the story. If we include prebiotic chemistry, the process may have started in the space between the stars. That follows from the discovery by X-ray astronomers of interstellar hydrogen cyanide, formaldehyde, and the other important polyatomic organic molecules listed in Table 1.

Although life is not readily definable, its essence is the multiplication of a certain sort of matter (animate) at the expense of different matter (inanimate) which does not so multiply. Energy is necessary for this and subsequent transformations, but is not considered in the present paper; it has been thoroughly discussed elsewhere (e.g., by Broda, 1971). The central feature of the animate type of matter is the transmission of a particular material order to succeeding entities; this is the genetic aspect.

The simplest member of the porphyrin class of compounds is porphine — a planar molecule comprising four pyrrole rings linked by methene bridges. Strongly stabilized by aromatic conjugation, porphine absorbs in the visible range with electronic transitions giving rise to an intense absorption band in the optical blue: the Soret band just below 400 nm. Secondary absorption features appear in the red end of the spectrum, in most cases between 500 and 600 nm. The molecular weight of porphine is 310 in the unsubstituted and uncomplexed form.

Carbon is stored in the earth’s crust principally as two carbon species: reduced or “organic” carbon (C_org) and oxidized or “carbonate” carbon (C_carb). With most of the element concentrated in the sedimentary shell, the reduced and oxidized carbon constituents of terrestrial sediments make up the bulk of total carbon residing in the outer skin of the planet.

The two main processes that have been responsible for releasing O₂ to the earth’s atmosphere are photosynthesis and photodissociation. Both involve the decomposition of water molecules and the removal of hydrogen from the atmosphere. The energy for photosynthesis in plants and bacteria is provided by visible light while UV photons of wavelength shorter than 240 nm are required for the direct, abiotic, photodissociation of atmospheric water vapour.

Cloud (1965; p.33) wrote: “..... it is now generally agreed that the components of the present atmosphere came ultimately from within the earth, mainly by volcanism. Free oxygen, however, is not directly available from such sources; nor, in the absence of green plant synthesis, is it formed secondarily except in trivial and readily scavenged quantities from photolytic dissociation of CO₂ and H₂O. All who have considered the problem critically, therefore, agree that at an early stage in its history the terrestrial atmosphere was essentially anoxygenic, or reducing. Only at a later date, after the appearance of a photosynthetic source of oxygen could the atmosphere evolve towards its present oxygenic (and oxidizing) state.” It is fair to add that there is not universal agreement as to the nature of the earth’s atmosphere during past geological time. For example, Dimroth and Kimberley (1976) did not agree that an O₂-free atmosphere had existed at any time during the span of geological history recorded in well-preserved sedimentary rocks. However, such a stance is difficult to maintain in the face of abundant evidence which has been reviewed by workers such as McKirdy (1974), Biochenko et al. (1975) and Schidlowski et a1. (1975) all of whom, and others, have contributed to the hypothesis of a primordial atmosphere, possibly largely of methane, subsequently modified to being CO₂-rich by the addition of juvenile gases from the outgassing of the earth. Oxygen, generated both photolytically and photosynthetically, was probably a quite minor component of the atmosphere for a considerable period before oxidizable minerals became fully accessible to 02 in the atmosphere and in the hydrosphere.

Current thoughts on the early history of the earth have been greatly influenced by the models of Cloud (1972, 1976). These models have attempted to explain, in an internally consistent fashion, the evolution of the atmosphere, hydrosphere, biosphere and crust of the earth. Our concepts of the origin of one of the most enigmatic rock types in the geologic record — the early Precambrian banded iron formations — have also been greatly influenced by Cloud’s models. During the past several years, many advances have been made in the fields of isotopic age dating, geochemistry and sedimentology which are significant to our understanding of the early history of the earth and to the origin of early Precambrian banded iron formations. In this context, a review of some of these advances and their implications seems warranted.

Of all the geological sources of evidence that have been quoted as to the composition of the atmosphere and surface waters in the Archaean and early Proterozoic, banded iron-formations (BIF) deserve special attention. Not only to they occur in vast quantities and widely distributed on the continents, not only are they virtually restricted to rocks older than about 2 Gyr, but they are chemical sediments that exhibit extraordinary lateral continuity in individual bands, and also sudden changes in composition from one band to another that must ultimately depend on simultaneous changes in the composition of the water from which they formed.

Sediments are a major sink for chemical components of water bodies. As part of on-going limnological studies of two man-made, urban lakes in Canberra (Cullen et al., 1978a, b and Rosich et al., 1978), the chemistry of the sediments has been studied for comparison with other lakes and to attempt to elucidate some of the processes that control the formation of sediments and transformations within sediments. The biological availability of sediment components is an important issue, especially in water management, and the results of some studies of nutrient availability are presented in Rosich and Cullen (1980).

This paper reports an experiment to estimate the amounts of phosphorus in lake sediment that may be available to phytoplankton. It is known that sediment can continue to maintain a polluted lake in an eutrophic condition (Bjork et al., 1972; Bengtsson et al., 1975). This is obviously an important issue when decisions are to be made about the diversion of sewage or other external sources of phosphorus to lakes.

The Vestfold Hills are an ice-free area of approximately 520 km2 between the coast of Antarctica and the edge of the polar ice cap, located between 68° 22’S and 68°40’S, and 77°49’E and 78°33’E. Davis Station, established in 1957 by the Australian National Antarctic Research Expedition (ANARE), lies on the coast at 68°34’S, 77°58’E. The biology of the area has been summarized by Johnstone et al. (1973).

Bacteria have important roles in sediment processes such as nutrient cycling, decomposition of organic matter and as a food source for many animals. In shallow marine environments where macrophytes are the main primary producers, bacteria are a dominant component of the food chain because much of the organic matter cannot be digested (Fenchel, 1977). Accurate estimates of bacterial biomass are needed in studies on their trophic role, but these are difficult to obtain in sandy sediments. Direct measurement of bacteria stained with acridine orange has been used after homogenising the sand to release attached organisms, but these are minimum estimates because an undetermined number of bacteria can remain attached (Dale, 1974; Meyer-Reil et al., 1978).

In August 1973 some 15 scientists from CSIRO’s Division of Fisheries and Oceanography, and from several other organizations, began a study aimed at understanding the flow of carbon through various biological and chemical compartments in a small marine embayment: the South West Arm of Port Hacking (located about 30 km south of the center of Sydney, New South Wales, Australia: Fig. 1).

The biogeochemistry of sediments is mostly confined to the upper part of the sediment. It is very rare to find biological processes of major importance in the geochemistry of sediments below a depth of half a meter. More often the major chemical changes take place at the uppermost centimetres of the sediments. In anaerobic sediments (sediments with the redoxcline at or above the sediment/water interface) biological effects on chemical transformations are usually restricted to even more shallow depths than with aerobic sediments. In the Baltic Sea anaerobic sediments are unconsolidated with a water content of 70% or more (Fig. 1). These sediments occur at various water depths but are mainly situated below the halocline, that is below about 55 m. The biogeochemistry of these sediments is being studied with the use of an in situ simulation technique. The experimental site is at a water depth of 10 m. This depth was chosen to facilitate the necessary SCUBA diving.

Stratiform stromatolites, which occur in some modern intertidal and lacustrine environments, are organo-sedimentary structures commonly produced by the sediment-trapping activities of the cyanobactería (blue-green algae). Stromatolites were prominent in analogous Proterozoic environments and are often associated with sulfide mineral deposits (Mendlsohn, 1976). It has been suggested that this association implies a role for the biological activities of stromatolitic ecosystems in the formation of some base metal sulfide deposits (Renfro, 1974; Trudinger and Mendelsohn, 1976). This suggestion appears feasible since the accumulated organic matter in the stromatolites would have been a potential source of energy for sulfate-reducing bacteria and, furthermore, fractionation during bacterial sulfate reduction could account for particular sulfur isotope distribution patterns in some deposits.

Solar Lake is a stratified, hypersaline, heliothermal heated water body situated on the coast of Sinai of the Gulf of Aqaba. The lake is 140 × 70 m and its maximal depth is 5.5m. It is fed by seawater seeping through a 60 m wide terrestrial barrier which separates it from the sea. The lake is strongly stratified for a period of nine to eleven months per year (Cohen et al., 1977a,b). During this period a mesothermal profile develops with a maximum temperature of 65° measured at 2 m water depth. Previous papers have dealt with the limnological cycle of the lake (Cohen et al., 1977a), the distribution of photosynthetic and nonphotosynthetic microorganisms and their activities in the water (Cohen et al., 1977b,c), sulfur transformations in the chemocline of Solar Lake (Jørgensen et al., 1979a), and the contribution of the cyanobacteria to the sulfur cycle in the water column (Padan and Cohen, 1980).

Organic geochemical studies of contemporary algal mats and organisms play a very important role in furthering our understanding of the history of marine and freshwater sediments of predominantly algal and bacterial origin. Blue-green algae are of special interest because of their ability to survive under conditions, such as hypersaline and reducing environments, which favour the preservation of organic matter. Further interest in contemporary algae arises from the search for the origins of unicellular life on earth. Micro-structures referred to as exhibiting “algal-like” and “filamentous” morphologies occur in cherts from South Africa that are older than 3 Gyr (Schopf and Barghoorn, 1967).

The technique of pyrolysis-hydrogenation-gas chromatography (PHGC: McHugh et al., 1976, 1978) provides a convenient means of analysing the carbon-skeleton structures of coals and coal-derived kerogens. Catalytic hydrogenation of the pyrolysate has the advantage of simplifying its composition prior to analysis by GC (or gas chromatography-mass spectrometry, GC-MS) without significantly diminishing the amount of structural information available in the resulting pyrogram. Alkenes and heteroatomic compounds are converted to the corresponding alkane or aromatic hydrocarbon. In the present study we extend the application of PHGC to kerogens of microbial origin, i.e., insoluble sedimentary organic matter derived from algae and bacteria.

Various high altitude lakes are found on the inter-Andean plateau of Antofagasta province, Chile. Laguna Lejia is located in a caldera (23°30’S, 67°42’W) at an altitude of 4180 m. Its surface is approximately 1 × 2 km and the water depth is unknown. The water level appears to be maintained by active springs. A delicate algal mat (ca 0.5–1.0 cm thick, Fig. la) is found in the shallow water areas, followed by black anoxic mud (ca 1–5 cm) and below that, coarse volcanic rubble. Isolated flamingoes feed on the algal mats, and insects are common at the shore. The caldera is sparsely vegetated by coiron grass (closely related to Stipa Venusta Phil.), (areas on the distant mountain slopes, Fig. lb).. The afternoon westerly breezes generate a white foam on the lake surface, which accumulates on the eastern shore (Fig. lb). This shore is covered by about 50 cm of dried foam and detritus.

Micropalaeontological studies of carbonaceous cherts have revealed fossilized algae estimated to be 3.1 Gyr old (Schopf, 1970; Schopf and Barghoorn, 1967). R. Buick and J.S.R. Dunlop (1979, personal communication) have described microfossils occurring in a 3.5 Gyr old chert-barite bed. These fossilized organisms may have had affinities with cyanobacteria or sulfur-oxidizing bacteria. Algal fossils of the genus Collenia are similarly preserved in Precambrian black cherts of Central Australia. The alkanes, phytane and pristane, are present in these deposits, and C12/C13 ratios confirm their photosynthetic origin. Organic molecules likely to survive lithification are those with greatest thermal stability — hydrocarbons and porphyrins. Chlorophyll-derived porphyrins and chlorins are widely found in Precambrian deposits through to the present-day sedimentary off-shore marine muds. The isoprenoid alkanes, phytane and pristane, occur in nearly all Precambrian rocks (McKirdy, 1974). Near-shore deposits have yielded 7-methyl- and 8-methyl-heptadecanes (Sever and Parker, 1970).

Biological methanogensis, carried out by a mixed culture of bacteria, is an exceedingly common and widespread process in nature. Methane is produced in the soil, in peat bogs, in both fresh-water and marine sediments, in sanitary landfills, and in the anaerobic digesters used to dispose of sludge in sewage plants. Yet the process requires a rather specific set of environmental conditions, including the presence of suitable energy-yielding substrates, the usual nutrient elements, a pH near neutrality, a low Eh, and a sufficiently low concentration of inhibitory compounds. Substances found to be inhibitory include organic acids, ammonia, certain heavy metals, sulfide, sulfate and nitrate. Why, then, does the process appear to take place, sooner or later, whenever naturally occurring organic matter decays under anaerobic conditions? The answers appear to be in the realm of microbial ecology. Microorganisms widely distributed in nature alter the environment in such a way that the growth of methanogenic bacteria eventually is assured. Methanogenesis then proceeds until substrate exhaustion.

The initial stages in the decomposition of organic matter in upper horizons of the lithosphere include aerobic processes carried out by representatives of various classes of microorganisms.

Ace Lake (Fig. 1) is a permanently stratified lake, 23 m in depth (Fig. 2), protected from wind driven mixing for at least 10 months of the year by ice-cover and supporting thick mats of benthic cyanobacteria, planktonic communities of algae, and a copepod crustacean. Evidence indicates that the lake had a marine origin and has undergone a complex evolution involving evaporation, replenishment with local freshwater and the loss of 76% of the original seawater sulfur content by sulfate reduction (Burton and Barker, 1979).

Intensive study of the global cycle of sulfur in recent years has revealed the requirement for substantial natural inputs of sulfur into the atmosphere to balance the measured rates of deposition (Friend, 1973). Estimates of the oceanic contribution of reduced sulfur to the atmosphere, usually derived by difference rather than actual measurement, vary from 30 to 202 Tg yr−1. The role of H₂S in this process has been debated (Slatt et a1., 1978), and methylated sulfur compounds have been commonly suggested as transfer agents (Rasmussen, 1974; Nguyen et al., 1978). The evaluation of the true magnitude of these fluxes is not yet possible due to the scarcity of measurements of the concentrations of the volatile sulfur compounds in seawater and the marine atmosphere.

From the viewpoint of biogeochemistry, Clostridium pasteurianum is a relevant organism to study for many reasons. It is involved in cycling of carbon, nitrogen, sulfur, and selenium and is capable of stable isotope fractionation of these elements (Laishley et al., 1976; Rashid, 1978). An appreciation of its participation in the sulfur cycle has been overshadowed by the facts that this organism gained considerable importance in the elucidating of the mechanism of non-symbiotic N₂ fixation (Winter and Burris, 1976) and that SO₄2− reduction has usually been associated with the “classical” reducers, Desulfovibrio spp. and Desulfotomaculum spp. In considering the early development of biochemical systems, however, ferredoxin and 5S ribosomal RNA sequence studies provide evidence that the clostridia evolved prior to the classical sulfate reducers (Schwartz and Dayhoff, 1978).

In 1972, Lovelock coined the use of the Greek work Gaia to denote the globe encompassing the biosphere, pedosphere, hydrosphere and atmosphere as an entity which has developed a powerful homeostatic system to control the global environment. This is a very important concept and a necessary one if we wish to describe, quantify and understand the global biogeochemical cycles. In order to elucidate this self-regulating system with regard to the atmospheric composition of non-noble gases, it is necessary to develop an integration between the atmospheric sciences and biology, especially microbiology (Margulis and Lovelock, 1978).

Recent research by atmospheric scientists has created international concern that increased use of nitrogen fertilizers to aid world food production will increase emission of nitrous oxide (N₂O) from soils to the atmosphere via denitrification of fertilizer-derived nitrate and thereby promote destruction of the stratospheric ozone layer protecting the biosphere from biologically harmful ultraviolet radiation from the sun (see Council for Agricultural Science and Technology, 1976; McElroy et al., 1977; Crutzen and Ehhalt, 1977; Liu et al.,1977). This threat has stimulated extensive research on factors affecting N₂O emissions from soils and the effects of nitrogen fertilizers on these emissions. The purpose of this article is to report recent research in our laboratory relating to the mechanisms of N₂O production in soils.

13N, a radionuclide with a half-life of 10 min, has been used for a variety of purposes in medical and agricultural research and in a variety of forms, e.g. as 13N₂ for study of nitrogen fixation and translocation in plants, 13NH₄ and 13NO₃ for studying plant nitrogen uptake, 13NO₃ for studying denitrification, and 13N₂O in medical research (Straatmann, 1977). The advantages of 13N are the ease of detection, measurement and identification of volatile products, and the short half-life that permits several consecutive experiments on the same material. The very small quantities of the label used ensure that there is no alternation of equilibrium reactions,but the short half-life does mean that experiments must be of simple design and must be conducted with minimum preparation of substrate and near the production source of the isotope. Nitrogen flux in soil due to dissimilatory denitrification, a form of anaerobic respiration, is a major component of the nitrogen cycle (Nielsen and MacDonald, 1978) and, in the experiments reported, 13N was used to examine the movement of the major components of the cycle in a relatively undisturbed soil and the evolution of gases by different bacterial cultures and soil cores.

In Fig. 1 are depicted the nitrogen species of known or presumed biochemical importance in each formal valence state, and the known or presumed reaction pathways for the major biochemical nitrogen transformations. Certain intermediate species such as hydroxylamine and nitrous oxide are common to more than one biochemical pathway and a possibility exists for “leakage” of these species between reaction pathways under appropriate environmental conditions. In such cases, analyses of stable subtrates or end products may not provide complete information about the nitrogen biochemistry of the system studied, especially if the analyses do not include all possible substrates and the end products.

Prior to the industrial revolution, the biogeochemical cycling of nitrogen was powered by the diffuse flux of energy from the sun. Atmospheric N₂ was fixed into biomass using reduced compounds derived from photosynthesis, and some abiotic fixation occurred during electrical storms. The reduced products of photosynthesis also provided the means of returning fixed nitrogen to its less biologically active forms, N₂ and N₂O, through the process of denitrification. During the present century, these precultural fluxes of nitrogen have been greatly augmented on local and regional levels by the fixation of N₂ into NO_x during fossil fuel combustion and by the production of ammonia for fertilizer by the Haber process.

During the last few decades man has contaminated the earth’s atmosphere with a large number of chemical species. His influence is difficult to quantify because for many species, the magnitude of the natural emissions is not known; nor do adequate records of their past or present atmospheric concentrations exist.

A variety of bacteria have been found to be able to catalyze manganese oxidation. They can be divided into two major groups on a physiological basis. To one of these two groups are assigned those organisms that act on free Mn2+, and to the other group are assigned those organisms that can act only on Mn2+ bound to Mn(IV) oxide. Of the group that attacks free Mn2+ ions, some members seem to be able to derive energy from the reaction while others cannot. So far, all members of a group of seven different organisms that attack only Mn2+ bound to Mn(IV) oxide are able to get energy from the oxidation (Ehrlich, 1976, 1978a; unpublished data).

The existence of particular valency states of manganese is governed mainly by the pH and redox potential (Eh) of the appropriate system (Morgan and Stumm, 1965).

The abilities of a number of different bacteria to couple the oxidation of manganous manganese to the generation of useful energy have been reviewed (Ehrlich, 1978). The oxidation of manganese is believed to occur via the action of a Mn(II)-oxidoreductase, which catalyzes the transfer of electrons from manganese to the electron transport system of the cell. The electron transport system involved in this transfer of electrons has not been thoroughly explained. However, in the case of the soil bacterium Leptothrix discophora, it was found that cell-free, manganese oxidizing particles contained both b-type and c-type cytochromes, as well as a cytochrome oxidase (Hogan, 1973). Manganese oxidation by these particles was completely inhibited by 10−5 M KCN and 10−4 M NaN₃. The inhibition by CN− and N₃− and the results of spectral studies indicated the involvement of a cytochrome oxidase in Mn(II) oxidation. The involvement of the b-type or c-type cytochromes was not shown.

Electron microscopic analyses of ferromanganese concretions from the deep-sea have revealed in them a myriad of surface and internal structures, some of which have been identified or interpreted as being of microbiological origin (Dugolinsky et al., 1977; Greenslate, 1974; Harada and Nishida, 1976; LaRock and Ehrlich, 1975; Wendt, 1974; Xavier, 1976). These results, along with work showing the presence of manganese-oxidizing bacteria (Ehrlich, 1975; Nealson, 1978; Schütt and Ottow, 1978), indicate that microorganisms may greatly influence the growth of deep-sea concretions.

Iron is readily soluble constituent in groundwater and the solubility is further increased by its chelation with organic matter. Iron, and minor elements such as Mn, are undesirable in water supply systems as they cause problems of taste, odour, and discolouration, and clogging and deposition in the screens and pipelines which eventually leads to corrosive conditions. The removal of iron can be accomplished by a sequential treatment involving oxidation, settling, and filtration with various modifications but, as well as the high cost of the treatment, incomplete iron removal and associated problems are frequently encountered.

Naturally occurring organic matter is known to complex cations (Schnitzer and Khan, 1972). However, there are differing opinions as to the importance of organic matter binding of metals compared to inorganic ligand binding (Stumm and Morgan, 1970). Ramamoorthy and Kushner (1975a,b) have suggested that organic matter is an important component of the binding capacity of certain rivers for Hg2+, Cu2+, Pb2+. Sunda and Hanson (1979) have demonstrated that organic complexes are the principal forms of soluble copper in rivers. Giesy et al. (1978) showed a large effect of organics on Cu2+ and Pb2+ in the binding capacities of several surface waters in Maine, but no significant effect of organics in the binding capacities of European waters (Giesy and Briese, 1980). Finally, Schindler and Alberts (1975) in a study of Par Pond determined that humic type organics were relatively unimportant in this system for the removal or burial of cations, but may play a role in redox reactions of certain metals.

In order to model the transport of heavy metals in rivers it is necessary to take account of many physical and chemical effects. Not only are these components carried along in the bulk of the flowing waters, a process known as advection, they are simultaneously mixed or spread by dispersion. In addition these and other chemical components will be injected at various points by sources along the river. Sinks occur where components leave the flowing waters (mobile phase) to attach themselves to, or be trapped by, the bed or banks of the river (stationary phase).

Less than a decade has passed since McDonald in November 1970 (Dotto and Schiff, 1978) suggested to the U.S. Congress that H₂O released in the stratosphere in SST exhaust would, by destroying O₃, lead to an increase in skin cancer. Since then the list of potential modifiers of our UV-screen has grown to include NO_x (Crutzen, 1970; Johnston, 1971), Cl (Hoshizaki et al.,1973; Stolarski and Cicerone, 1974), Br (Wofsy et al.,1975), bremsstrahlung x-rays from relativistic electron precipitation events (Thorne, 1976) and modifiers of stratospheric temperature (Blake and Lindzen, 1973; Boughner and Ramanathan, 1975). While cosmic ray-produced negative ions (Ruderman et al., 1976) and stratospheric particles (Cadle et al., 1974) had been proposed as possible destroyers of O₃, these threats now appear to have been eliminated (Fehsenfeld et al., 1976; Olszyna et al., 1979).

Since Sydney Chapman first introduced the theory of photochemical production of O₃ in the stratosphere in 1930 there have been continuing efforts to reconcile theoretical models with the observational facts about atmospheric O₃. Recently this effort has intensified due to concern that humanity may inadvertently modify the ozone layer through various activities. In this paper we discuss the uncertain basis of current models of atmospheric ozone and then present some southern hemisphere measurements of trace gases that are involved in stratospheric chemistry.

During the last decade the increase in atmospheric CO₂ concentrations has been approximately 1 μg g−1 yr−1 (Bischof, 1977). The concentration in 1977 was ca. 329 μg g−1 (Keeling and Bacastow, 1977). This increase was mainly from the accelerated combustion of fossil fuels and Man’s increased disturbance of terrestrial ecosystems.

Efforts to increase forest productivity have resulted in a need for fertilizers. Mostly energy-consuming synthetic fertilizers are used. At the same time sewage plants produce an increasing amount of sludge with a high nutrient concentration, especially nitrogen. This sludge has become a disposal problem but it could instead be used as fertilizer in forests.

Polychlorinated biphenyls (PCBs) are highly-stable man-made compounds which have been used in a variety of applications since the 1930s. The accumulation of PCBs in nature was not known until 1966 (Jensen, 1972) but since then they have been found in waters, soils, sediments and living organisms from all parts of the world (Risebrough et al., 1968; Peakall, 1972, 1975; USDA et al., 1972; Finlay et al., 1976; WHO, 1976). The toxicity of PCBs to living things has been well documented (Peakall, 1972; Higuchi, 1976; WHO, 1976) and evidence suggests that they are accumulated by organisms at all levels of the food chains in the same fashion as DDT and its metabolites (Jensen, 1972).

The South West Coast Drainage Division, which extends over 3.14 × 109 km2 (Anon, 1975), is economically the most important part of Western Australia. Sadler (1976) examines problems associated with increasing water demands and limited resources, and possible conflicts with development of land resources in the region. Of particular concern is the degradation of quality of surface water resources, which has occurred in the 150 years since European settlement (Wood, 1924; Peck and Hurle, 1973; Loh and Hewer, 1977). Thirteen of the nineteen river basins (over 50% of the surface water resources of the region) yield water containing total soluble solutes greater than 500 mg 1−1. Some of these streams were fresher before settlement but are now too saline for many potential uses (Mulcahy, 1978).

Langelier (1936) described the state of saturation of natural waters with respect to CaCO₃ by Equation 1, 1% MathType!MTEF!2!1!+- % feaagCart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn % hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr % 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9 % vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x % fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaam4uaiaadg % gacaWG0bGaamyDaiaadkhacaWGHbGaamiDaiaadMgacaWGVbGaamOB % aiaaykW7caWGjbGaamOBaiaadsgacaWGLbGaamiEaiabg2da9iaadc % hacaWGibWaaSbaaSqaaiaad+gaaeqaaOGaeyOeI0IaamiCaiaadIea % daWgaaWcbaGaam4yaaqabaaaaa!4D21!]]</EquationSource><EquationSource Format="TEX"><![CDATA[$$Saturation\,Index = p{H_o} - p{H_c}$$ where, pH_o is the observed pH of a solution and pH_c is the calculated pH that the same solution would have if it was saturated with CaCO₃, but with no alteration in ionic composition. In effect, positive values of the Saturation Index mean that solutions are supersaturated with respect to CaCO₃ and there will be a tendency for carbonate to be deposited. This tendency is aggravated by temperature increases since the solubility of CaCO₃ decreases at elevated temperatures, such as are experienced in hot water systems.

Thiobacillus-like microbes capable of oxidizing ferrous iron at pH 1.6 and a temperature of 55° have been found in thermal springs (Brock et al., 1976; LeRoux et al., 1977), a large-scale copper leaching test system (Brierley and Lockwood, 1977), commercial dump leaching operations at the Chino Mine, Hurley, New Mexico (Brierley, 1978), the Bingham Canyon Mine, Bingham, Utah, the Vlaidov Vrah Mine, Bulgaria (Groudev et al., 1978), and ore deposits in the USSR (Golovacheva and Karavaiko, 1977). These microbes have a chemolithotrophic heterotroph or mixotrophic mode of metabolism. They oxidize ferrous iron, pyrite or other metallic sulfides for energy, but growth occurs only in media supplemented with a reduced carbon compound such as yeast extract or glutathione. These microbes do not appear to fix carbon dioxide (Brierley et al., 1978) and may not reductively assimilate sulfate (Brierley et al., 1979).

The leaching of sulfide minerals by Thiobacillus ferrooxidans involves a series of chemical and biochemical reactions. These have been set out in various publications (Tuovinen and Kelly, 1972: Brierley, C.L., 1978: Le Roux et al., 1974). It seemed possible that thermophilic microbes might be contributing to metal leaching in sulfidic environments where the exothermic reactions gave rise to elevated temperatures. The presence of such microbes has since been demonstrated (Brierley and Lockwood, 1977; Brierley, J.A., 1978). In order to examine the possibility of enhancing metal extraction rates at elevated temperatures, a moderately thermophilic bacterial culture, isolated from a geothermal area in Iceland (Le Roux et al., 1977), was examined using various sulfides as substrates. No attempt was made to purify this culture.

Colony formation is an important characteristic of a bacterial species. Using Scanning Electron Microscopy, (SEM), it is possible to examine detailed structures not observable by any other microscopic method (Roth, 1971). Such structures include the following: the inter-relationships between cells in a colony; the attachment of cells to the supporting surface and their modification of that surface as the colony grows; the way in which the bacterial cells are arranged within the colony as their numbers increase during growth; and the changes occurring in colony structure because of their growth.

Uranium commonly occurs in the tetravalent form [U(IV)] in uranium-bearing rocks and the solubilization involves its oxidation to the hexavalent uranyl ion.

The use of microcalorimetric techniques to investigate microbial processes has been increasing rapidly since easily-operable, high precision instruments became commercially available (Wadsö, 1970, 1973). Almost every process, chemical, physical or biological, occurs with either a gain or a loss of heat to the system. The heat quantities involved are related to the rate and extent of the process, and using microcalorimetry it is possible to measure heats of reaction in the order to microwatt quantities. Also, the process can be monitored for a considerable length of time without disturbing the system.

At the present time the biological leaching of copper is applied on industrial scale in several ways: mainly as dump and heap leaching of mining wastes, and more rarely, as underground leaching of low-grade ore material in situ. Nevertheless, in all cases the leaching processes are carried out by the respective indigenous microflora. The latter includes wild strains of various microorganisms but the most important role in leaching is played by the chemolithotrophic bacterium Thiobacillus ferrooxidans (Trudinger, 1971; Corrans et al., 1972; Rossi, 1974; Groudev et al., 1978a). Its activity can be enhanced by an artificial improvement of some of the rate-limiting environmental factors, and, nowadays, this is the one and only applicable way to increase bioleaching under natural conditions. It must be noted, however, that a quite different way exists, at least theoretically: to “seed” leaching operations with laboratory-bred strains (or with wild strains taken from other ecosystems) possessing a leaching activity higher than that of the indigenous strains. That second way is closely connected with the problem of strain screening and improvement of T. ferrooxidans.

The authors have studied the isolation of iron- and sulfur-oxidizing bacteria from mine water and carried out some investigations on the leaching of sulfide ores, in the hope that a technology of bacterial leaching of ores might be devised. The present paper is a brief summary of these results.

The reclamation of land made derelict by coal mining waste involves a number of decisions and actions. Amongst these are the methods to be used in correcting the acidity resulting from past oxidation of pyrite in the spoil and in preventing the oxidation of the residual pyrite in the spoil. Neutralisation or ‘liming’ of the spoil (in particular with agricultural limestone) is currently practiced both as a corrective and preventative measure. However, there is not yet an adequate basis for predicting the efficacy of liming or the amount of ‘lime’ required.

The interaction between bacteria and metals can vary considerably, depending on the level of oxygen and the pH of the system. By its limitation of the redox potential of a system, pH will consequently limit the species of bacteria existing under those conditions and will also constrain the redox reactions accessible to metals of variable oxidation states. Interest herein has been directed primarily towards determining the effect of reducible species such as vanadium(V) and to a lesser extent, chromium(VI) and molybdenum(VI), on the growth of Thiobacillus thiooxidans. We became interested in this topic through a study into the use of T. thiooxidans in the bioleaching of a petroleum coke derived from Athabasca oil sands bitumen (Zajic et al., 1978). It was observed that leached vanadium and iron were almost entirely in their lower oxidation states (+4 and +2 resp.) and that small concentrations of the metals chromium and molybdenum in their +6 oxidation states could curtail growth of the bacteria.

Ores amenable to microbial leaching often contain pyritic material which contributes to the formation of leaching agents, i.e. acidic ferric sulfate. The bacterial attack on pyrite involves either a direct oxidation mechanism or acceleration of the parallel chemical degradation of pyrite by ferric iron and sulfuric acid (Silverman, 1967; Tuovinen and Kelly, 1972, 1974d; Torma, 1977; Brierley, 1978a; Kelly et al., 1979; Manchee, 1979). Thus, pyrite is an important source of leaching agents for the microbial solubilization of ores. Iron-oxidizing thiobacilli (Thiobacillus ferrooxidans) are able to grow on FeS₂ but a prior adaptation to this substrate as well as to other sulfide minerals is required (Silver and Torma, 1974; Norris and Kelly, 1978a). Previous studies have shown that fine-grained particles of different materials (glass beads, fluorapatite, sand, quartz, U-bearing rocks, and pyrite ore) inhibit the iron oxidation activity of T.ferrooxidans (Soljanto et al., 1980). The inhibition of the bacteria was related to the shaking of the culture flasks and to the type, amount and particle size of the various materials studied. In the present work, high-grade pyrite was investigated in more detail with a view to determining its inhibitory nature for the iron-oxidizing thiobacilli. Other particles (coal, mixed copper-nickel ore) were also tested in the experiments to extend the previous observations.

Accumulation of peat, the precursor of coal, requires a humid climate to support lush vegetation and a high water table to permit prolonged accumulation of organic material in a reduced environment (Averitt, 1973). Most of the eastern and central US coal measures were periodically inundated by sea water during their formation. Sea water contains approximately 2,700 mg 1−1 sulfate (Garrels and Thompson, 1962) and when coupled with reducing conditions and readily oxidisable organic matter, as was the case during coal formation, significant sulfate reduction occurs. The sulfide produced may react rapidly with detrital ferrous ion (Fe2+) to form ferrous sulfide which is ultimately transformed into pyrite (FeS₂) (Berner, 1971; Rickard, 1972).

There have been two basic approaches to obtaining a description of liquid distribution in a packed bed. Tour and Lerman (1944) considered the flow through the packing to follow a random number of steps down to the left or right.

We have been investigating the possibility of recovering vanadium and other metals from petroleum cokes, using chemical and microbially-assisted leaching techniques (Zajic et al., 1977, 1978). The cokes examined were derived from bitumen processed from the Athabasca oil sands in the province of Alberta Canada. These bituminous sands occupy a vast area and represent the largest deposit of vanadium in Canada. Vanadium is much in demand as an additive in high-strength low-alloy steels (Brown et al., 1974).

An early step in the assessment of the amenability of a mineral-bearing material to microbially-catalysed degradation or modification is the determination of its behaviour under optimised conditions. The results can give some idea of “ceiling” performance and indicate whether it is likely to be profitable to proceed with longer-term testwork in columns or other devices in which the constraints of real field situations can be more accurately simulated. This first objective can be secured by the use of the time-tried, accelerated shake-flask technique, which has the advantage of relative cheapness and simplicity of equipment and of the simultaneous handling of a larger number of samples. It has the disadvantages of rather large sampling errors, lack of precision in the range of operating conditions easily attainable, and is increasingly costly in terms of manpower.

Presently, chemical leaching of uranium, particularly from an acidic gangue, involves acidic ferric iron solutions. The 6-valent uranium is soluble at the acidic pH values involved, whereas solubilization of 4-valent uranium involved oxidation to the 6-valent species with ferric iron as the primary oxidant. Under most commercial vat leaching conditions, the pH is modestly below the level at which microbiological leaching can occur. In heap or “in situ” leaching, microbiological leaching is responsible for a substantial proportion (in mine drainage situations for all) of the uranium solubilized. The bacterium, Thiobacillus ferrooxidans, oxidizes the sulfides of most metals to the corresponding sulfates, thus generating acidic solutions. Where iron sulfides are involved the iron moiety is solubilized and concomitantly oxidized to the ferric form. The acidic ferric solutions, thus generated, solubilize both the 4- and 6-valent forms of uranium. The pH values over which this microbiological action can normally proceed are in the approximate range of 1.8 to 2.6; the upper limit being the less absolute. As the 4-valent uranium is oxidized to the 6-valent form, the iron which is reduced to the ferrous form is quickly reoxidized to the ferric state by Thiobacillus ferrooxidans, thus enabling leaching to continue. Microbiological oxidation of ferrous to ferric iron is in no way dependent on the original source of the ferrous iron. Thus microbiological oxidation can interact with chemical leaching processes, where pH and other conditions permit.

According to the “Club of Rome” the continuously increasing world-wide demand for raw materials will cause an exhaustion of non-reclaimable resources within the next few decades (Meadows 1972). On the other hand, the resources are not regarded as a static magnitude but as a dynamic one which increases in accordance with scientific and technnological progress (Rechtziegler, 1973; Heilbroner, 1973). Hence, new deposits may be discovered by the improvement of conventional methods and by the development of new geochemical and geophysical prospecting methods. But discovering a new ore body does not mean that mining will be feasible because several factors may influence the metal winning process, e.g. low amount of total ore, low concentration of valuable metal, large dissemination of ore.

In previous studies (Torma and Subramanian, 1974; Torma and Guay, 1976) we have demonstrated that a decrease in the particle size of the solid metal sulfide results in an increase in the rate/or extent of the metal extraction by the chemolithotrophic Thiobacillus ferrooxidans. The use of fractions of a lead-zinc sulfide concentrate (Torma and Subramanian, 1974) smaller than 5 pm in diameter resulted in zinc extractions as high as 98.1% in five days of leaching. Only limited information is available from the literature regarding the bacterial leaching of solid particles where the size of the ore would approach the bacterial dimensions (which are about 0.5 pm wide and 1.5 to 2.0 pm long). Conventional milling techniques are not practical for producing these very small particle sizes. However, the attrition grinding techniques have shown to be quite effective in producing mineral particles below the one pm range (Sadler et al., 1975). The applicability of attrition grinding in hydrometallurgical operations is a subject of intensive research (Gerlach et al., 1973; Beckstead et al., 1976).

There is growing interest in the bacterial leaching of low-grade ore bodies in the Australasian region. Operational aspects of local heap leaching have been described by Andersen and Allman (1968). The experimental approach to this process frequently employs the use of percolation leaching columns (Madsen et al., 1975; Bruynesteyn et al., 1977; Le Roux and Mehta, 1978; Murr and Brierley, 1978). The results to be presented arise from laboratory leaching studies on copper porphyry ores from Bougainville Island, Papua-New Guinea. The detailed mineralogy of these rock types have been described by Lawrence and Savage (1975). Espie (1971) has described the Bougainville Copper Project mining operation.

The initial stages of leaching in Hungary may be traced back over a period of 500 yr (Podányi, 1977a; 1977b), whereas biohydrometallurgic research has a background of only one decade. The introduction of large scale in situ leaching experiments intensified with bacteria, to be realized in 1979–1980 may be considered as an important stage of development (Lakatos, 1976a; 1976b; Várhegyi et al., 1973).

The most important ores of manganese are oxides, although they may also include manganous carbonate (rhodochrosite) and silicate (rhodonite). Some of the oxide minerals of manganese are shown in Table 1. Since the manganese with oxidation states of +3 and +4 in these minerals is insoluble, its hydrometallurgical extraction requires its reduction to the divalent state. Industrially, this can generally be achieved by roasting with a suitable reductant such as gas, oil, or solid fuel, CO and H₂ being other examples of effective reducing agents (Sully, 1955).

Microorganisms are widely used in many technical processes. One of the main purposes of this paper is to report some of the changes which occur in mineral ores under the influence of different types of bacteria. Studies on these changes have made it possible to develop methods for the extraction of manganese, uranium, and especially copper, from some ores and other metal-containing products (Karavaiko et al., 1972; Kulebakin, 1978).

Rum Jungle, situated some 90 km south of Darwin, is reasonably well-known as a uranium mine that operated during the uranium boom of the fifties. Mining operations started in 1953 and carried through to 1971 when the mine was abandoned. Rum Jungle is also reasonably well-known as a mining operation which has had a marked impact on its environment. The major impact has been on the East Branch of the Finniss Fiver, which flows through the mine site, and on the areas alongside the overburden dumps. This impact stemmed from the high concentration of heavy metals such as copper, manganese and zinc in the water flowing from these dumps, and other areas of the abandoned mine, into the East Finniss. The major sources of pollution (Davy,1975a) are the overburden dumps and a dump of low grade copper ore from which extraction of the copper by a heap leaching technique was attempted.

Rum Jungle is an abandoned uranium mine located at latitude 13°S, about 90 km south of Darwin. Mining commenced in 1953 and ore processing ceased in 1971. The abandoned mine site contains three flooded opencuts, their associated overburden heaps and the remains of the tailings dam. Copper and lead were associated with the ore, and both the ore and the overburden contained significant amounts of pyrites.

In the course of uranium mining and extraction operations at Rum Jungle in the Northern Territory of Australia over the period 1953–70, processing materials were obtained from five opencuts and a sixth was excavated to just below the level of the ore body. In the monsoonal climate of Northern Australia, with its annual average rainfall of about 150 mm during the wet season, all opencuts became water-filled on the cessation of mining operations. Those in the Rum Jungle Mine area proper (Fig. 1) have become highly acidic and metal-polluted (Intermediate, White’s and Dyson’s Opencuts); the water in the other three opencuts (Rum Jungle Creek South, Mt Burton and Mt Fitch Opencuts) is neutral to slightly alkaline in reaction and the heavy metal content is negligible (Davy, 1975).

One of the by-products of oil production in the Athabasca oil sands, Canada, and indeed in most petroleum refining operations, is coke. At the Great Canadian Oil Sands plant there is a net production of about 500 Mg day−1 over and above that which is burned for fuel. This residual coke is currently stockpiled and could constitute an environmental hazard, depending on the susceptibility of elements in the coke to “natural” leaching. In order to assess this potential problem a number of cokes were leached with water and the toxicity of the leachates were examined (Zajic et al., 1978).

In many mining operations the mines are de-watered, i.e. water is pumped from the mines to prevent flooding of operations. The water often contains low concentrations of the elements being mined as well as other associated ions. These waters must be treated to meet governmental regulatory standards before being discharged. Some of the mine waters are used in milling processes, and become even more laden with soluble inorganic ions. These brines are pumped to tailings ponds for evaporation or eventual release to surface or ground water systems. Both mine waters and tailings solutions are valuable sources of metal and other ions, and it is both economically and environmentally sound to recover these elements. In the state of New Mexico, U.S.A., industries which must remove inorganic agents from large volumes of water are the uranium and molybdenum operations. Although precipitation, ion exchange, solvent extraction and electrowinning systems are available for soluble ion removal, these systems are quite often ion specific and very expensive when treating large volumes of water. An inexpensive and ion non-specific, accumulator system is the desirable alternative. The understanding and design of a functional bio-filter system for removal of uranium and other ions associated with uranium mining operations would alleviate discharge problems in the Grants, New Mexico, U.S.A. district (the producer of 46% of the U.S. uranium). Such a system would be applicable to other uranium-producing regions. The bio-filter process may also be applicable to other industries, with wastewater effluents containing trace elements. Among the extractive industries, the molybdenum operations have considerable need for economic and environmentally safe processes for purification of mill effluents.

One consequence of the industrial development experienced over the last fifty years has been the increasing demand for water for industrial purposes. This trend has also characterized the mining industry and, particularly, the mineral beneficiation plants. An average size flotation plant treating 5 Tg of run-of-mine ore per day has a water requirement of at least 20,000 m3. This not negligible amount of water must obviously be drawn from the natural hydrological resources of the area where the plant is located and, usually, for the most part, returns to it after the settling of the solids in appropriate tailings ponds.

The following paper intends to illustrate the comprehensive environmental program performed by a German mining company in order to avoid pollution of the existing ecosystem in the Red Sea. It will not present a detailed picture of the scientific results, but it intends to delineate the financial investments to be made and to show to what extent the mining industry takes care of protection of the marine environment.

Literature on the possibility of desulfurizing coal by microbiological leaching is limited. The earliest report was that of Zarubina et al. (1959) who indicated that 23 to 27% of sulfur was removed from their coal samples in 30 days. Other investigators (Silverman et al. 1961, 1963; Lorenz and Tarpley 1963; Clark 1966) commented on the beneficial effect of decreasing the particle size of coal samples and of adding small amounts of ferric sulfate to the leach solution. Recently, Dugan and Apel (1978) achieved an almost complete removal of pyrite from coal by using a mixed culture of Thiobacillus ferrooxidans and Thiobacillus thiooxidans Capes et al. (1973) reported that the surface properties of pyrite and coal were changed during the microbiological leaching to such an extent that the separation of pyrite from coal by the conventional flotation technique was considerably increased.

Mine waste pollution from Captains Flat mining area in New South Wales, Australia (Fig. 1), had degraded the biology of the Molonglo River, which flows into Lake Burley Griffin in Canberra some 50 km downstream, and reduced the usefulness of its waters. In the absence of immediate remedial works, there was a risk of increased pollution from accelerating erosion of the mine waste dumps and from the collapse of unstable areas.

Every activity of man causes some change to the environment. These changes range from barely discernable foot-tracks in recreation areas to the total reconstruction of the landscape in our cities. Of all man’s activities, agriculture and grazing have had the most widespread effect yet it is mining which, although affecting only very small areas, has received the greatest public attention.