Open pits of abandoned lignite surface mines in the Lusatian and Mid-German mining districts of Germany cover a great area of landscape. Most of these open pits will be filled by the rising water table or by flooding with river water or a combination of both. Due to pyrite or marcasite oxidation many of the water bodies evolved (mining lakes, open pit lakes) are extremely acidic (pH <4) and several ions and metals are enriched in concentration. Some metals like iron, manganese or aluminium reach critical loads (Alpers et al., 1994; Friese et al., 1998; Schultze et al., 1996).
Sediments play an important role in the behavior of elements in lake environments acting as source and sink. The biogeochemical reactions and transformations that take place in the sediments lead to highly dynamic processes at the sediment water interface. To study the influence of these reactions on the lake chemistry and biology detailed depth profiles of the sediment porewaters were investigated. Porewater was obtained by centrifugation after coring and slicing the sediment cores in cm-intervals. The trace element composition was analyzed by several atomic absorption techniques (ICP-MS, ICP-OES) and the results will be discussed with respect to the lake water chemistry.
Alpers C N, Blowes D W (Eds), ) Environmental geochemistry of sulfide oxidation.- ACS Symp. Series, Washington, (1994).
Friese K, Hupfer M, Schultze M, In: Geller W, Klapper H, Salomons W (Eds) Acid Mining Lakes - Acid Mine Drainage, Limnology and Reclamation, Springer, 25-45, (1998).
Schultze M, Geller W, In: Reuther R (ed) Geochemical approaches to environmental engineering of metals, Environ. Sci. Series. Springer, 89-105, (1996).
Pyrite oxidation is the main source of the mine and/or rock water acidity and pollution. The large mine tailings impoundments had been formed in Banská Stiavnica (Central part of Slovakia) and Smolník (East part of Slovakia) mining regions as the results of the mining and processing of polymetalic- and of copper ore deposits. Both impoundments contain substantial amount of pyrite and can be potential source of the mining pollution. These impoundments are inactive for about ten years and products of pyrite oxidation appeared on a steeply impoundment dam. Evidently, the composition and properties of originally alkali sludges have changed in a dry, near-surface parts of the tailing impoundment. The character of pore water and ground water table position in impoundments are limited not only by the mine tailings porosity, permeability and chemical stability of tailing minerals, but also by the morphology and climatic conditions of the impoundment area, as well. After exposure to air oxygen in unsaturated horizons of the impoundment, pyrite and other sulphides (Cu, Pb, Zn) are oxidized. Decreasing pH values of antropogenic soils (Banská Stiavnica: soil pH H2O < 2, Smolník: pH H2O < 3 ) directly demonstrate the intensity of pyrite oxidation and soil acidification. Acid soils are quickly devoided of vegetation and are deeply eroded. Secondary sulphates (gypsum and jarosite) and Fe-oxy-hydroxides precipitate on the soil and/or on the tailings surface. These minerals are also formed on pyrite or other sulfide grains surfaces. Pyrite grains from various tailings depths reveal a different degree of oxidation and leaching.Smolnik tailings contain carbonate minerals, mainly Fe dolomite (ankerite) and acid-base neutralization take place within mine tailings. More stable and better crystallized forms of Fe oxyhydroxides, mainly goethite, with increased content of metals as Mn, Cu, Zn are formed in drainage channels. However, permanently increased (overlimited) Fe concentrations are detected in discharged tailings drainage waters. More detailed studies of mine tailings and drainage waters compositions and observation of ground water table stability on the both impoundments are needed to predict, if nowadays inactive impoundments will be a serious source of pollution in the future.
Knowledge of the background concentration of metals in soils and waters associated with mineral deposits in key areas is useful for predicting water quality in areas with similar geologic settings, as well as to serve as a tool when quantifying effects of future mining in a specific area. The main objective of this study was a pre-mining baseline study at the Liikavaara deposit in the Aitik area in northern Sweden. Liikavaara and Aitik are c. 1.9 Ga old biotite-amphibole-gneiss hosted Cu-sulphide deposits. Aitik, which is of porphyry type, is the largest sulphide mine in Europe, and is operated by Boliden Mineral AB. The Liikavaara ore will probably be mined in the near future. A baseline study in the planned mining area at Liikavaara started in the spring 1997. The sampling area is situated within 4 km from the open pit at Aitik. Dust originating from the mining activities must, therefore, also be considered in the Liikavaara area.
The water sampling program was performed every second week during more than one year, and include sampling of the dissolved phase in atmospheric deposition, soil water, groundwater and surface waters. The surface waters were also sampled for the suspended phase. Chemical analyses were performed by using ICP-AES, ICP-MS and High Resolution ICP-MS. A spodosol profile in mineralized till was analysed, and a sequential extraction was carried out with this material. The total metal concentrations (ppm) at a depth of 75 cm in the till were: Cu, 2310; Zn, 160; Pb, 70; Ni, 20.1; Co, 19.5. The sequential extraction showed that large fractions of the total concentrations of these metals are associated with secondary Fe-oxyhydroxides rather than primary sulphides. The soil water concentrations are highest in the E-horizon with declining concentrations towards depth. All water types have higher concentration of Cu in particular in comparison with an unmineralized reference area. High Cu concentrations in snow (2.2 µg/l), precipitation (0.42-1.1 µg/l) and throughfall (2.6 µg/l) indicate an important dust contribution from the Aitik mine. However, it is concluded that weathering of the mineralized till results in elevated concentrations of Cu and other elements in soil water, groundwater and stream water.
The underground Troya mine (The Basque Country) exploited a sulphide ore body located in a karstic aquifer. Important drainage work was carried out from 1982 to 1993 in order to exploit the ore, pumping at a rate of 50 L/s. The potentiometric level was depressed from an elevation of 435 masl to 190 masl, and the spring that had drained the aquifer up to that moment (34 L/s) dried up. After the mine was abandoned in 1993, the groundwater level recovery started; and in 1995, with the potentiometric level at 335 masl, water began to flow out from the North Adit, which is the mine access of lowest elevation. The discharging water has a high SO4 content (1500 mg/L), and noticeable dissolved metals - 50 mg/L of Fe and 5 mg/L of Zn - although the pH is neutral. Water pollution is caused by the oxidation of pyrite and marcasite; this process takes place when the ore minerals are in contact with both air and water in a zone where the mine rooms are partially flooded. The acidity generated by pyrite oxidation is neutralized by calcite dissolution and CO2 exsolution in an anoxic environment.
During a two-year period (1995-1997) the mine water outflowed directly to Gesala Creek, where the fish population was eliminated due principally to Fe(OH)3 (ochre) precipitation and the presence of toxic metals. From June 1997 to now, mine water has been diverted to the old tailings pond of Troya mine, and now the water entering the creek is dam overflow. The tailings pond is functioning as an arerobic wetland. This action has considerably improved the overflow water quality. The dissolved Fe is oxidated and Fe(OH)3 precipitates in the pond, and other metals coprecipitate with ochre. Overflow metal concentrations are 0.7 mg/L Fe and 0.9 mg/L Zn. Fish population in the Gesala creek has been recovered.
Between 1952 and 1990 the former SDAG WISMUT had dug approximately 3000 km of underground shafts at depths between 30 to 940 m below surface in the Uranium mining region of Ronneburg, Germany. The shafts were dug into intensively folded and faulted, incompetent and competent rocks of Paleozic age. The mining activities resulted in a groundwater depression cone of nearly 50 km2, 17 dumps with a total volume of 200 million m3, as well as in an open pit mine at Lichtenberg, now partly filled, with an original volume of 160 million m3. Several tributary rivers and brooks drain the area to the west into Weiße Elster and to the east into Pleiße.
The flooding of the Ronneburg uranium mine was intiated in the beginning of 1998 by the WISMUT GmbH. In the near future the groundwater will reach the surface and will discharge water of variable quality in local brooks. To quantify the amounts and the distritibution of the discharged flooding water, the pre-flooding condition of the brooks was investigated and will be presented.
The Gessenbach/Badergraben system is thought to be the main discharge area of groundwater in the post-flooding stage. This system is the most important drainage system in the western part of the uranium mining area. The orohydrographic catchment area is located between the cities of Ronneburg and Gera. In its upper section at elevations from 200 to 270 m AMSL the brook flows E-W through an area where as the result of mining, surface and subsurface show intensive anthropogenic modification. The brook system cuts rocks of Silurian to Permian age. Some of these rocks contain large amounts of markasite, pyrite and organic matter and have therefore a high acid forming potential under oxidizing conditions. In addition to more or less untreated sewage of adjacent towns, highly mineralized and acidic seepage water of various dumps is added diffusely in the Gessenbach/Badergraben system.
Geological, hydrogeological and geochemical studies provide the framework for the characterization of the pre-flooding situation. Diffuse inflows of highly mineralixed water in the meter-thick Quaternary valley sediments were used as tracers and provided information on the groundwater movement. First results of hydrogeological studies comprising data from the water balance for discrete sub-catchment areas, characterization and reconstruction of hydraulic parameters for some lithologic units with emphasis on fractured and fissured rocks, evaluation of hydrochemical analyses of surface and groundwater, and analyses of groundwater-level data are presented here. The valley sediments will be further characterized by geophysical methods. These studies will be used to forecast the behaviour of the groundwater flooding front.
Behaviour of geochemically close elements in modern processes of dissolving, migration, reprecipitation becomes very different. The main aim of our investigation was to find out the main factors, which influence on migration features of HM in aquatic system. The object of investigation is tailings dump of Salair plant, processing barite - polimetal ore (Kemerovo region, Russia). To estimate relative migration of Zn and Cd we use an elemental ratio in different substances: sphalerite, ore, waste, solid substance of bottom sediment, and water (surface, pore, drainage). We can see that Zn/Cd ratio decreases from the ore to bottom sediment and waters.
Sphalerite Ore Waste Sediment Pore Surface
water water
Zn 66.85 1.5 0.3 0.55 4000 350
Cd 0.23 0.0006 0.00035 0.0008 21 1.7
Zn/Cd 290 2500 800 450 200 150
The reason the above decrease is more intensive increase of Cd concentration in comparison with Zn in the chain "ore-waste-bottom sediment-pore water-surface water". Reverse migration of Cd is significantly complecated. Cd speciations in the water calculated with the help of computer code WATEQ4F (Ball, Nordstrom, 1987) are mainly ionic form (Cd2+aq) and sulfate form (CdSO40aq). As for Zn we can see several main forms: ionic (Zn2+aq) and sulfate (ZnSO40aq), carbonate (ZnCO30aq) and hydroxide (Zn(OH)2). Moreover, according to simulations Cd practically can not form suspended phase (it's possible only in pore water, where greenockite is formed), but Zn form such suspended speciation as cinkite (ZnO), smitsonite (ZnCO3), Zn(OH)2, ZnSiO3 and even sphalerite in pore water (ZnS). So we can regulate toxicity of Zn by changing the water composition (for instance, by adding carbonates). Suspended particles drop to the bottom and thus they are burried in the bottom sediment. Cd can not be burried in bottom sediment and migrates further. Therefore under these conditions Cd is very dangerous element for the environment.
Nordstrom DK & Ball JW, Mine Water, Granada, Spain, (1985).
Ball, JW, Nordstrom, DK & Zachmann, DW, Geological Survey Open-File Repor, 87-50, (1987).
Environment is only a recent concern in mining history. As a result, most societies are left with abandoned, often acid-producing, waste and mine-tailings. These end-products constitute a technical and economical challenge for environmental management, since 1) legal owners liable for acid and metals released to the environment are frequently vanished or insolvent, 2) no cash-flow is available for mitigation and neutralisation of acid mine drainage, as it is the case for an operating mine, and 3) nothing was implemented, in these earlier days, that could provide a minimal physical and chemical stability for these deposits, at least over a few decades after mine closure. Passive technologies directed toward the prevention of acid mine drainage, rather than its perpetual treatment, are often put ahead. They share a common approach that aims to cut oxygen access to sulphide minerals, either by synthetic membranes, water cover, multi-layer soil covers, etc. However, these techniques can hardly solve some specific problems related to old mine tailings. For instance, ancient mining practices often result into unconfined tailings deposits and large spill-over areas, extending well beyond the margins of a "normal" tailings impoundment. The placement of an extensive oxygen-tight cover becomes rapidly prohibitive in such a case. Old tailings are also filled with acid-prone pore-water, produced years before any mitigation takes place, if any. That water may need tens of year to be purged out, perpetuating an acid problem well after any intervention to block sulphide oxidation. A reactive cover consuming oxygen, rather than blocking its diffusion, is appealing for such cases. Wood wastes made up mainly of tree barks are efficient in the full scale cover placed over the East-Sullivan tailings, in north-western Québec, Canada. Moreover, organic compounds derived from the cover support anaerobic chemical reactions, such as sulphate reduction, that increases ground-water alkalinity and allows base metal precipitation. That capacity was demonstrated in closed vessels experiments, involving wood barks of various ages: pH increased from 1,5 to near neutral values, and accordingly SO42- and Fe2+ decreased from 2400 and 400 ppm to values as low as 10 and 5 ppm, respectively, within a few weeks. The oxygen barrier at East Sullivan is thus used for the interim treatment of acid water effluents collected around the impoundment, these being pumped over the organic cover.Sulphate reduction is the driving mechanism in the reducing wetland approach. However, the development of preferential surface flows, and a large interface with air that favours oxidation and hydrolysis of iron and lowers the pH, compromises the efficiency of such devices, especially under cold-weather climates. However, the reducing and insulating properties of wood wastes can counteract these problems. Devices that would intercepts effluents from spilled tailings and directed it into such reactive barriers are actually under design.
Finding new and improved methods for management of mining waste is truly a challenge. The large amounts of waste rock and tailings that are produced by mining of low grade ore calls for combined research efforts by geologists, geochemists, microbiologists, geohydrologists, geotechnical expertise, ecologists and botanists. Personnel from the mining industry and the authorities take active part in the work within the MiMi programme. The MiMi programme is financed by the Swedish Foundation for Strategic Environmental Research (MISTRA) with contributions from the mining industry. The first phase of the programme covers the years 1997 - 2000, with the intentions to be continued in additional phases.
The MiMi-programme consists of five projects: Field studies, Laboratory studies, Predictive modelling, Prevention and control, and Communication and commercialisation. Scientists and engineering specialists from different disciplines within the five projects work together in an integrated and co-ordinated way. To emphasise the truly co-operative approach, a common field site at the Kristineberg mine in northern Sweden has been chosen for the studies within the programme. An important part of the programme is the synthesis work where the findings and results of the different research activities are brought together, put into context and elucidated in a systematic way to identify potentially interesting ideas and explore new and improved methods for waste management. An overall obligation of the programme is to establish efficient ways to communicate the results to the end-users in industry, authorities, academia and other parties, to assure that the research findings lead to practical applications.
For the first phase of the MiMi programme the major efforts are concentrated to studies of the effects and efficiency of dry soil covers and water covers, barrier systems, wetlands and vegetation. During later phases of the programme, the work will gradually shift over to studies and tests of new methods. During the first years different hypotheses will be tested, for example: i) dry and wet covers are suitable and effective remediation methods, ii) the long-term performance of dry and wet cover methods can be demonstrated and predicted, iii) critical processes can be identified and controlled by new and improved remediation methods, iv) suitable combinations of remediation methods can further enhance the overall efficiency, v) ways to adapt and integrate the deposits with the surrounding biosphere can be found by stimulation of natural processes rather than isolating the deposits from the environment, and vi) by new and improved methods the costs can be significantly reduced without jeopardising the environment. This approach certainly requires the input from many different research and engineering disciplines.
In sulphidic tailings deposits, a distinct zonation is often developed above the groundwater table as a result of oxidation and weathering. There is generally an oxidised zone above the unweathered tailings, but there may also be a zone of secondary metal enrichment below the weathering front. This zonation is of importance for the result of the remediation. One method to prevent the formation of acid drainage from sulphidic mining waste is to limit the supply of oxygen by applying a dry cover on the waste. Studies of the efficiency of dry cover and other remediation methods are the major tasks of the MiMi-project (Mitigation of the environmental impact of mining waste) which started 1998 with the Kristineberg mine in northern Sweden as the main field site. The c. 1.9 Ga stratiform Kristineberg ore is situated in felsic metavolcanics overlain by metasedimentary rocks. The main sulphide minerals of both the ore and the tailings are pyrite, sphalerite and chalcopyrite. The tailings were deposited in five tailings impoundments (impoundments 1B,1, 2, 3 and 4) along a small valley during a period of almost 50 years. Impoundment 1 was remediated in 1996 by covering with till and by raising the groundwater table. The till cover applied to impoundment 1 consists of two different kinds of cover. One consists of 0.3m compacted till, and above that 1.5m with unspecified till whilst the other is 1.0m unspecified till only. In this paper we discuss the solid-water interactions in impoundment 1 two years after covering with till, based on geochemical and mineralogical analyses of the tailings, and geochemical analyses of pore water samples from the tailings.
In October 1998, the till cover and the tailings were sampled in 5 profiles using a drill rig. Each drill hole extended down to the underlying till. Pore water samples were extracted after the sampling in an argon-filled glove box. There is a zonation in the tailings, with the oxidation front extending between 50 and 100 cm below the tailings surface. The zonation of the tailings caused by oxidation before the remediation will be described in detail, and the interactions between primary and secondary minerals in the tailings and water will be discussed. The release of metals from secondary minerals as a result of the lack of oxygen caused by the till cover will be quantified.
One method to prevent the formation of acid drainage from sulphidic mining waste is to limit the supply of oxygen by applying a dry cover on the waste. Studies of the efficiency of dry cover and other remediation methods are are major task of the MiMi-project (Mitigation of the Environmental Impact from Mining Waste) which started 1998 with the Kristineberg mine in northern Sweden as main field site. The groundwater geochemistry of a tailings impoundment covered by till is presented in this paper. The c. 1.9 Ga stratiform Kristineberg ore is situated in felsic metavolcanics overlain by metasedimentary rocks. The ore was discovered as early as 1918, and the mining operations started in 1940 by Boliden Mineral AB. Mining is stillin progress but the processing plant was closed in 1991. Ore from the Kristineberg mine as well from the Kimheden, Hornträsk, Rävliden and Rävlidmyren mine was processed at Kristineberg. The main sulphide minerals of both the ore and the tailings are pyrite, sphalerite and chalcopyrite. The tailings were deposited in five tailings impoundments (impoundments 1B,1,2,3 and 4) along a small valley. Impoundment 1 was remediated in 1996 by covering with till and by raising the groundwater table.
Installation of groundwater pipes was performed in July and October 1998. A total of 16 pipes have been installed in impoundment 1 including 10 BAT groundwater pipes (Torstensson and Petsonk, 1988). The studies of the groundwater started in September 1998, and 8 of the BAT-pipes have been sampled regularly. The concentration of several elements are high in the groundwater. Concentrations as high as 440 mg/l Ca, 9.1 g/l Fe, 855 mg/l Mg, 17.7 g/l S and 663 mg/l Zn have been measured. The concentrations of Cd, Co, Cu, Pb and Ni are rather low (in the range 20-150 µg/l). The results from the investigations of the groundwater during 1998 will be discussed and compared with concentrations measured during 1983-1988 by Ekstav (1989) prior to the remediation.
Ekstav A, Metallbalans-Kristineberg, Kvartärgeologiska Avdelningen, Uppsala University, (1989).
Torstensson BA & Petsonk AM, Ground-Water Contamination: Field Methods, ASTM STP 963, 274-289, (1988).
Pyrrhotite is more reactive and oxidises more rapidly than pyrite. In the late sixties, a few hundred thousand tonnes of pyrrhotite concentrate were deposited as one of five tailings impoundments at the Kristineberg mine in Northern Sweden. The pyrrhotite was regarded as a potential raw material for production of sulphuric acid, but was later considered as waste. The pyrrhotite deposit was remediated in 1996 by covering with till. The cover consists of 0.5 m compacted till, and above that 1.0 m with unspecified till. Studies of the efficiency of dry cover and other remediation methods are the major tasks of the MiMi-project (Mitigation of the Environmental Impact from Mining Waste) which started 1998 with the Kristineberg mine in northern Sweden as main field site. In this paper we discuss the oxidation that occurred before remediation in this extremely reactive material, and the effects of the solid-water interactions two years after remediation. The interpretations are based on geochemical and mineralogical analyses of the pyrrhotite concentrate, and geochemical analyses of pore water samples and groundwater.
In October 1998, the till cover and the pyrrhotite deposit were sampled in 2 profiles using a drill rig. Both drill holes extended down to the underlying till, which was situated c. 7 m below the till cover. Pore water samples were extracted after the sampling in an argon-filled glove box. In July 1998, a BAT groundwater pipe was installed. This pipe has been sampled regularly. Before remediation, the pyrrhotite concentrate was oxidised down to the groundwater table, at a depth of c. 4 m. The zonation of the pyrrhotite deposit will be described in detail, and the interactions between primary and secondary minerals and water will be discussed. Since a large part of the pyrrhotite was oxidised before remediation, it is of particular interest to study the importance of release of metals from secondary minerals as a result of the lack of oxygen caused by the till cover.
Carbon dioxide and methane are the most important atmospheric trace gases contributing to the anthropogenic greenhouse effect. Their concentrations reached 358 ppmv for CO2 and 1.72 ppmv for CH4 in 1994 (global average), with an annual increase of 0.4% and 0.6%, respectively (Houghton et al., 1995). Anthropogenic CO2-emissions are mainly energy-related, whereas several sources contribute to the increasing methane concentration. For example, coal mining is assumed to emit about 5 to 12% of all methane on a global scale. In coal mining areas, the emission of methane-rich coal gases into the atmosphere via mine shafts is a well-known phenomenon. Emissions of methane through the lithosphere/atmosphere-interface are much less known for coal-bearing basins. To fill this gap in knowledge, we conducted more than 1000 flux chamber experiments in the field. Study areas are the Ruhr Basin and the Lower Rhine Basin, containing bituminous coals and lignite, respectively. Both research areas have been or are still subject to mining. Gas fluxes (methane and carbon dioxide) were measured and isotopic data determined at 17 localities during a period of two years. These areas differ in the structure of the geological subsurface, in soil type, in anthropogenic utilization at the surface and in mining intensity. Pronounced CO2 emissions were found at most places. Emission rates depend on temperature. Hence, CO2 emissions normally showed a seasonal variability with a maximum in summer. This is typical of bio-degradation of organic matter (Crill, 1991). The stable carbon isotopic composition of CO2 varied between -24 and -26‰ (13C-values vs. PDB), which are typical data of decomposing plant tissues (Saurer et al., 1995). At some places in the Ruhr Basin where this seasonal variability is missing, CO2 emissions are characterised by a lighter isotopic composition of -30 to -34‰, which indicates an admixture of thermogenic CO2 (Whiticar, 1990).
The methane fluxes across the lithosphere/atmosphere-interface show a different pattern. At all localities in the Lower Rhine Basin and many in the Ruhr Basin methane was consumed by methane oxidising bacteria in the soils. In both basins a distinct pattern of bacterial methane consumption was observed. Agricultural fields show less bacterial methane consumption than meadows or forests. The self-cleaning potential of soils towards methane emissions was balanced. We calculated an average of 2494 tons of methane consumption per year for the Lower Rhine Basin and 1428 tons for the Ruhr Basin, both with a tolerance of ± 37.9%. This is an average of -0.88 mg methane /(m2*d). Methane emissions were found in the Ruhr Basin, in regions of former and recent underground coal mining. There, it is possible to trace some subsidence troughs and especially their rims by methane emissions at the surface. Outside of areas with underground mining activities, no coal-bed methane emissions were measured. Thus, there seems to be a causal connection between underground coal mining and methane release.
Crill PM, J. Biogeochem. Cycles, 4, 319-334, (1991).
Houghton JT, Filho LGM & Callander BA, Climate Change, 1, 64-95, (1995).
Saurer M, Siegenthaler U & Schweingruber F, Tellus, 47B, 320-330, (1995).
Whiticar MJ, Org. Geochemistry, 16, 531-547, (1990).
To predict the scales and contamination degrees of adjacent territories, it is necessary to reveal a tendency of heavy metals to change their solid species during the storage sulfide-bearing tailings. Our report considers this problem in application to the sediments of the old pond.
Djukov tailings impoundment accommodates the cyanidation wastes of the oxidized Au-Ag-barite ores. Initially the pond sediments were represented by the silt material of tailings with interlayers of sand material. Hydro-micas ( up to 30%) and kaolinite ( up to 15%) dominate in the silt, and sand generally consists of quartz (up to 80%). The different contents of metals and their exchangeable fraction in silt and sand were caused by metals leaching from the penetrable sand material, their conservation in slightly penetrable silt material and the sorption capacity of the silt (table 1). During 23-year existence of the technogeneous lake formed from a pond, sedimentary layer of 2 cm thickness was formed there. The granulometric composition of this layer significantly differs from the tailing material (table 2), however, its mineral composition is close to the silt composition due to coagulation of clay particles. Formation of sediments during the pond-to-lake transformation was accompanied by the development of aquatic vegetation. As a result, the content of C org. in the lake product is 3 times higher than that in the initial tailing material. According to Table 1, the lake product is characterized by a drastic increase in the exchangeable fraction of heavy metals, but the bulk metal contents do not considerably differ from the tailing materials. We assume that increased content of C org is the reason for such a drastic increase of the exchangeable fraction. According to experiments of Frimmel and Huber (1996), humic substances significantly increase the capacity of various mineral phases (in particular, quartz and kaolinite) to sorb heavy metals.
It is necessary to emphasize that due to the pond-to-lake transformation and aquatic vegetation growing, heavy metals of sediments transfer into movable solid species, and even a slight change in physical-chemical conditions will provide intensive leaching of these metals.
Table 1. Concentration of the metals (ppm), their exchangeable fractions (ppm) and C org.
Material Pb Pb Zn Zn . Cu Cu Cd Cd Corg
total ex. total ex. total ex. total ex. %
Lake 8220 600.0 3572 446 506 4.8 14.2 7.2 1.54
Silt 10275 58.0 3561 20 530 1.1 15.1 3.3 0.38
Sand 1584 4.5 1669 39 144 0.6 4.4 0.7 0.51
Table 2. Content of the granulometric fractions (%).
Material -0.01 0,01- 0,05- 0,09- 0,06- 0,25-
0,05 0,09 0,16 0,25 0,5 +0,5
Lake 34.6 28.5 37.0 - - - -
Silt 74.7 17.6 2.0 - - - -
Sand 1.9 22.5 27.3 32 9.7 4 1.4
F. H. Frimmel and L. Huber, Environment International, 22, 507-517, (1996).
The objective of this investigation was to describe the aqueous chemistry of the Udden pit lake in northern Sweden. The Udden pit lake is situated approximately 30 km west of Boliden in northern Sweden. The mining of the deposit in Udden started in 1971 with an open pit. The average grade of the ore was; 0.8 g Au/ton, 41 g Ag/ton, 0.41% Cu, 4.72% Zn, 0.35%Pb, 0.1%As and 25.6%S and the surrounding rock consisted of vulcanite with a SiO2 concentration higher than 52%. A total of 690 000 tons of ore and 1 000 000 tons of surrounding rock was excavated from the open pit mine before the surface deposit was exhausted. The decommissioning program based on flooding started in 1991. After two years the open pit was filled with ground water creating a lake that is approximately 50 m deep, 150 m across and 390 m long. The water in the Udden pit lake has been sampled at three different occasions during the period June to September 1998. The samples were analyzed for concentration of Fe, Cu, Cd, Zn, Pb, As, SO42-, Cl- and total concentrations of N and P. Temperature, dissolved O2, conductivity, pH, and redox potential were measured in situ at different depths with a Hydrolab DataSonde. Four layers could be observed in the lake and the origin of these will be discussed in the poster. A thermocline was found at a depth of 5 m. pH increased downwards in the lake. The pH of the water column down to a depth of 20 m was between 4.7 and 5.2. Below 20 m the pH increased to >5.7. Oxygen is present down to 20 m. Except for changes in temperature no variation could be found between the three different sampling periods.
Drainage waters from sulphide containing mining waste are, besides low pH-values, characterised by high concentrations of heavy metals and sulphate. The mobility of heavy metals within the deposits and the recipients of drainage water can be strongly influenced by adsorption to mineral surfaces. Humic substances might enhance or inhibit the adsorption processes. In this study a filtered winter sample of a concentrated bog-water has been studied with respect to acid-base properties as well as complexation reactions to goethite (<alpha>-FeOOH) in both the presence and absence of sulphate. The humic sample was concentrated with a freezing out technique. The measurements were performed as potentiometric titrations, pH-stat and batch adsorption experiments in constant ionic media (0.1 M NaNO3 and 0.6 M NaCl) with the use of a glass electrode and UV- and DOC-measurements. The humic sample showed upon two buffering regions, pH < 6 and pH > 8. The first is ascribed to the presence of carboxylic groups and was characterised by fast equlibria. The second is ascribed to phenolic groups with considerably slower equlibria. A good fit was achieved for the assumption of a diprotic acid (H2A) in the carboxylic region and a monoprotic acid (HB) in the phenolic region. For the adsorption studies it was found that up to 95% of the humic substances adsorbed to goethite at a ratio in total concentration of 0.24 mmol C/g solid. The adsorption of organic substances onto goethite was described with a surface complexation model, in which electrostatic forces of charged particle surfaces were accounted for. Evaluation of the data set indicated formation of inner sphere complexes.
Mill tailings from the mining of sulfidic ores have the potential to produce acid mine drainage (AMD) over extended periods of time. Quantitative understanding and description of dominant processes is essential for prediction of the environmental impact of mining wastes. The main process behind the production of AMD is the oxidative weathering of iron sulfides, such as pyrite and pyrrhotite, with the associated release of protons. Subsequent transition to conditions of low pH can lead to mobilisation of heavy metals. The oxidation of sulfides takes place via several abiotic and biotic mechanisms occurring in parallel, with either oxygen or ferric iron as the oxidizing agent. The overall rate of sulfide oxidation depends critically upon, and participates in the regulation of, parameters such as pH and aqueous concentrations of dissolved oxygen and iron.
Remediation measures commonly aim at reducing the oxygen flux into the mill tailings, buffering the pH and/or decreasing the water flux through the waste deposit. The effectiveness of such measures in decreasing the contaminant release depends critically upon the response of the biogeochemical processes to changes in physical and chemical parameters. The complex interaction and feed-back mechanisms between the various processes and parameters require the use of predictive AMD models that include all dominant biogeochemical processes involved in different redox and pH zones to quantify the effect of different remediation measures.
In this study we develop an AMD model for investigating the relative importance of different oxidation mechanisms under various physical and chemical conditions that are relevant for mill tailings from a copper/zinc sulfide ore. Parameters investigated include concentration of dissolved oxygen, mineralogical composition of the mill tailings and water residence times in the impoundment. Empirical rate laws for slow, kinetically controlled processes, such as sulfide and silicate weathering reactions, have been coupled with equilibrium expressions for fast geochemical processes which regulate pore water speciation and mineral solubilities. Model results highlight dominant biogeochemical processes in AMD generation and indicate the sensitivity with respect to key physical and chemical parameters. The developed model is also applied to the Kristineberg site, Sweden, in order to quantify the effects of the two remediation measures: dry covers and raised groundwater level. Model results for the non-remediated site are compared to field data and contaminant fluxes for various remediation scenarios are evaluated.
The slag material from the Cu-Ni-smelter at Selebi Pikhwe, Botswana has been subject to SOXHLET leaching over a period of 50 days under pH3 and pH7 water input conditions. The grinded material is composed of fragments of a homogeneous type I glass, an inhomogeneous aggregate of type II glass, fayalite and magnetite with type I glass chemistry, and finally liberated sulphide spheres. The SOXHLET leachates of each 24 hours were analysed. Both experiments showed after a rapid decline an asymptotic progress for the dissolved elements. Whilst pH7 samples showed extremely low mobilisation the pH3 samples showed a by 100 times elevated output. The experiments were stopped after 50 days, frozen, cut, freeze dried and analysed in three vertical sections for changes in chemistry, specific weight and specific surface area. The specific weight increased from 3.5 g/cm2 in the starting material to 3.6 in the pH3 samples and decreased to 3.45 in the pH7 samples. The change in the specific surface area was dramatic. Starting with 0.8 m2/g the pH3 sample reached 8.5 m2/g and the pH7 samples 19.5 m2/g. The polished thin sections of the experiments showed hardened crusts of 7 mm and 0.8 mm thickness for pH3 and pH7, respectively. Whilst the pH3 crust was still porous, the pH7 crust showed a relatively dense Fe-hydroxide-gel coating. Within the pH3 sample the alteration does affect both types of glass. At pH7 the homogeneous glass at the rim almost quantitatively has been dissolved and has been reprecipitated as Fe-hydroxide gel agglutinating the relics and less altered inhomogeneous glass fragments. The sulphide spheres, being embedded in situ in the gel, do only show minimal alteration. To estimate the partitioning of both types of glass and the sulphide spheres in the process responsible for the gain in the specific surface area, the area proportions of the fragments and detailed views of individual fragments were taken with the microscope and the SEM-SE from the altered and the unaltered samples. The envelop of the section area of the selected fragments in the sections were measured. The envelop was attributed to an ideal disc and from this the surface area of a corresponding sphere was calculated. The difference in the surface area for fragments of comparable size according to the degree and type of alteration is significant. Different types of fragments contribute in different ways to the measured bulk surface area. Starting with a surface area contribution of about 0.1%, 25% and 74.9% for sulphide, homogeneous and inhomogeneous glass, respectively, these proportions shift in favour of the sulphide and the inhomogeneous glass, whilst shrinking core digestion of the homogeneous glass declines its contribution to the bulk surface area.
Slagheaps may consist of very reactive materials. The reactivity is a function of the water availability, the mineralogical and chemical inventory of the slag fragments, the grain size distribution, the accessible surface area and the degree of compaction. Additionally morphology of the area of deposition, the climatic conditions and the microbiological impact are of major importance. Some of these slagheaps clearly do show after a few years of deposition visible changes of the primary inventory. Besides erosion, the decomposition of primary phases, the development of secondary products, the extraction of soluble and mobile components and finally the development of hard crusts at various levels of a slagheap are the outstanding changes. Twelve column tests were designed to simulate unaltered (quartz, grain size <200µm, specific surface area 0.2 m2/g) and altered (silicagel, <200µm, 237 m2/g) material to show the impact of the specific surface area on the dynamics of the capillary force movement. The lower third of each column was filled with a homogenized mixtures of either quartz or silicagel with a magnetic concentrate of a silicate slag precursor. Primary phases of the concentrate are cohenite (Fe3C) which might be intergrown with an Fe-sulfide, magnetite, graphite and relics of silicate glass material. Alteration dominantly affected the cohenite producing Fe-hydroxide gel. Three columns of each filling were arranged around a holder with a mounted ventilator on top to increase evaporation. Two sets were used with different ventilation speeds (1.15 and 0.73 m3/min) at 22° ±2°C room temperature. The capillary transport in conjunction to the evaporation is reflected by a significant change in colour from white to yellow and orange at the top part of the columns right after 24 hours starting in the silicagel columns and after one week visible in the quartz columns, too. After 14 days a dramatic increase of the specific weight of silicagel from 2.13 to 3.7 and 3.0 g/cm3 for fast and slow ventilation, respectively, but a decrease for the quartz columns could be observed. The XRF-analyses of individual horizons show a distinct transfer of elements from the lower portion of the column to the crust. The SiO2 content shows a relative decrease due to selective addition of Ca-sulfate, Na, K, and some of the heavier metals such as Fe, Sr, Rb, Pb, Cu, Zn, etc. The element transport in the quartz filled columns appears to be retarded.The capillary force is elevated in the silicagel filled columns relative to the quartz filled columns by a factor of 1.5, documented by the water consumption per day. The higher ventilation speed does further increase the evaporation by a factor of 1.5, too.
The investigation deals with metal distribution and mobility in the surroundings of the pyrite-chalcopyrite-sphalerite mine of Libiola, in the Gromolo Valley, near Sestri Levante, in the Ligurian Apennines. The mineralization is hosted in pillow and brecciated basalts, and partially involves tectonically overlying serpentinites. The mine was already known in the Copper Age (about 2500 y B.C.), economic exploitation started in the XVII century and ended in 1965. Mining operations were active both in open pit and underground shafts. Nowadays several open galleries and waste dumps (covering an area of about 0.5 km2) testify the past mining activities. Acid drainage is locally present and causes evident environmental problems. Mine waste are reddish-yellowish, generally coarse-grained and stratified. The waste consists of a mixture of ultramafic, basalt-like and iron-rich phases, with relatively high concentrations of S (mean 0.3% S) and Cu (mean 0.3% Cu), and significant contents of Zn, As, Mo and Se.Acid drainage has pH values as low as 2.5 and is quite rich in dissolved Fe, Al, Cu, Zn, Mn, Ni. Repeated sampling revealed marked chemical variations, particularly in the mine waste area, depending on water flow conditions. When low-pH water mixes with normal surface water a sudden flocculation of amorphous hydrate iron phases (e.g. ferrihydrite, schwertmannite) takes place, as a striking example of alkaline geochemical barrier. The influence of the mine presence in the Gromolo river is testified by the orange coatings on boulders, downstream to the town of Sestri Levante, about 8 km from the mine. Stream sediments revealed anomalous contents of Fe, Cu, Zn, Sc, Y, La, Ce, and to a lesser extent of Cr, Co and Ni, these latter being also controlled by ultramafic lithologies outcropping within the basin. The data so far obtained allowed the delimitation of peculiar situations, the evaluation of stream sediment and stream water quality, and the identification of mechanisms controlling the metal dispersion in the surface environment.
The rate of oxygen diffusion in sulphidic mine waste deposits may be an important factor controlling the rate of sulphide mineral oxidation. Substantial reduction in the diffusive flux of oxygen could potentially be achieved by covering the waste with a material with a low effective diffusion coefficient, since such material may act as a barrier against oxygen diffusion. The effective oxygen diffusion coefficient is a function of parameters that may exhibit spatial variations within both the waste and the cover material. In particular, the effective diffusivity depends on the saturation conditions, which in turn are governed by the water flow and retention characteristics and hence by the physical properties of the material. Reasons for spatial variations in the physical properties can be heterogeneity within the mine waste and/or cover material as such, but also heterogeneities created during waste and cover material application. Another factor that may cause spatial variations is naturally occurring destructive processes, such as freeze-thaw cycles, erosion and the formation of fractures that may deteriorate the long-term integrity of the oxygen diffusion barrier.
This study involves a theoretical investigation of spatial variations in the physical properties of covered sulphidic mine waste deposits, and couples such variations to the rate of oxygen diffusion under static equilibrium hydraulic conditions. The physical properties governing the effective oxygen diffusion coefficient are assumed to have a random spatial distribution. The nature of the spatial distribution is discussed for different types of waste and cover heterogeneity structures. The potential effects of variability in the physical properties on the rate of oxygen diffusion are analysed within a stochastic framework, in which the rate of oxygen diffusion into covered mill tailings as well as covered waste rock deposits is addressed for various degrees of waste and cover material heterogeneity, and for different hydrologic conditions in terms of depth to the water table. Further, the potential impact on the rate of oxygen diffusion from spatial variations in the physical properties caused by cover deterioration is analysed for different types and magnitudes of cover deterioration. The theoretical results illustrate the potential effects of spatial variability by comparing the rate of oxygen diffusion into sulphidic mine waste deposits for heterogeneous conditions with the rate of oxygen diffusion for homogeneous conditions. Based on the results, quality demands on the physical properties and the long-term integrity of cover materials is discussed in terms of waste and cover material heterogeneity.
Lake Süßer See west of Halle, Germany, is a natural sink for heavy metals, which are abundant in the streams crossing the copper shale mining and smelting district of the Harz montains. The lake and its environment serves as a recreational area for the local residents. In order to estimate the future stability of the immobilised heavy metals in the lake sediments we study the vertical distribution of key elements like copper, lead, zinc and arsenic. In addition, in selected samples the species of the metals will be studied using several analytical methods including 6-step sequential leaching, x-ray diffraction and scanning electron microscopy.
The lake sediments contain up to 3% Zn, 4000 ppm Pb, 3000 ppm Cu and 2000 ppm As. These maximum values are reached at depths between 10 and 30 cm below the water-sediment boundary. There is a general trend of decreasing metal concentrations with depth.
Several potential potential sources of pollutants of geogenic and anthropogenic kind have to be taken into account. Pollutants of geogenic origin are heavy metals from the outcropping copper shale at the periphery of the Mansfeld syncline, rock salt from the saline deposits of Permian age and sediments by the erosion of rocks and soils washed away from the riverbanks (sandstone, loess). Man-made pollutants include seepage from the mine tailings and smelting products of copper shale mining (in particular fly ash), overflow of the sewage treatment plant Eisleben, waste water from adjacent communities as well as fertilizers and pesticides from agriculture. Element ratios in the lake sediments can serve as geochemical tracers. These tracers together with the bonding states of the heavy metals in the lake sediments compared to those of potential sources should help to identify the main sources of pollution. The data show that fly ash is the main carrier of the heavy metal contamination of the lake sediments.
Some mine induced earthquakes, are caused by mining operations which centers are located directly in underground openings. Most of them are registered in deep mines in India (Kolar Gold Fields) and South Africa (Witwatersrand). They are characterized by magnitudes Ì = 1¸5 and cause great damage to mining operations. Over 20 such earthquakes have occurred in the Russian mines over recent years with this number continuously increasing. For searching the potential centers of mine induced earthquakes two favorable circumstances are used: 1) limited space of mine fields and their location near the surface; 2) two stages of mining development, when at the first stage prospecting and preparation for excavation of ore are made, and at the second - their excavation is carried out. Systematic test on natural stress in a develompent workings net enables one to reveal the potential centers of mine induced earthquakes. The technique of searching the centers was illustrated on an example by Lovozero rare metal deposit in the Kola peninsula as an example. The mine workings of this deposit are situated at a depth of 200 to 400 m from the surface in burst-prone ground. The test on stress in workings was carried out by core discing in boreholes with an interval of 50 to 200 meters of an expansion of all mine workings. It has been ascertained, that mine induced earthquakes most frequently occur in tectonic-stressed massifs, in which the ratio of natural horizontal and vertical stresses >1. The potential centers of earthquakes in underground mines are tectonic ruptures and zones of their intersections, near to which the level of natural stresses >0.8 rock compressive strength.
About 700000 tons of wastes have been produced on Belovo Pb-Zn metallurgical plant (West Siberia, Russia) after smelting of base metal ores. This slag contains 1.5-3% of Cu and 1-0.5% of Zn. Wastes are stored as piles and are open to the effect of weathering agents. The important feature of slag is the high concentration of carbon (15-25%). The combustion of waste material takes place as a result of carbon oxidation. It could accelerate the metal transformation and migration.
The aim of this study was to understand the main steps of copper redistribution and migration during the slag storage. Solid samples of wastes were collected from the surface of piles as well as over their cross section. Seepage waters were sampled from a small stream. They were filtrated and pH was measured in situ.
According to microprobe data, copper is initially presented in four phase types: the thin veins (<0.5 mm) of metallic Cu (Cu - 92-98%, Fe - 2-5%), Cu-Fe-S phase (Cu - 46-57%, Fe - 14-23%, S - 22-25%), Fe pearls Fe (Fe - 93-86%, Cu - 4-6% S - 0.1-5%) and Fe-S-Cu phase (Fe - 59-61%, S - 34-35%, Cu - 3-4%). As a result of interaction of these phases with hot steam and carbon dioxide (t>70,oC), the secondary minerals of copper are formed. At the depth of 10-20 cm from the pile surface, the malachite (Cu2(OH)2[CO3]) and azurite (Cu3(OH)2[CO2]2) are deposited. On the surface near "fumaroles", the chalcontite Cu[SO4]·5H2O and hydrated zinc sulfates are observed. These minerals precipitate during cooling and evaporation of solutions. Copper and zinc sulfates are very soluble, therefore, they are washed off by atmospheric water and migrate to environment. This statement is confirmed by results of water analyses (AAS). The acid (pH=2.5-2.6) seepage water sampled from a ditch contains Cu - 0.5-0.7 g/l and Zn - 1-1.3 g/l. On the bottom of a ditch, the metallic copper is deposited on scrap iron. Downward the stream, the pH value of water increases up to 3.5-3.9, however metal concentrations don't change. A decrease in acidity (pH=7.7) and metal content (Cu - 0.6 mg/l and Zn - 0.5 mg/l) was observed after mixing the seepage waters with urban wastewater. Probably, the metal concentrations decrease because of their precipitation and dilution of the seepage water.
Thus, successive steps of copper transformation are as follows: the extraction from primary copper phases to pore solutions - precipitation in the carbonate form (malachite and azurite)-chalcontite formation - dissolution of chalcontite and migration with the seepage water - deposition of metallic copper from this water on iron scrap - precipitation in the flocculent form after mixing the seepage waters with urban wastewater.
There exist many studies that describe chemical reactions during pyrite oxidation (WISOTZKY, 1994). Our investigations stand in connection with the environmental problems of acid mine drainage in the area of former lignite mines. Pyrite reacts with oxygen and water to form following products:
FeS2+ 14 Fe3+ + 8 H2O react to15 Fe2+ + 2 SO4 2- + 16 H+
There is a seven electron difference in oxidation state between sulfur in pyrite and that in sulfate. Oxidation steps must occur by one or at most two electron transfers per reaction. That's why metastable oxidation intermediates were expected of us in the pathway.
Pyrite oxidation in laboratory was carried out under standardized conditions. We used a low pressure mercury lamp and hydrogen peroxide as oxidation agent to stimulate the oxidation reactions. Metastable sulfur oxyanions were identified by analysis of liquid phase using HPLC with fluorescence detector. The physical-chemical parameters pH, electric conductivity, temperature and Eh were simultanely measured. Like expected, the investigations show the decrease of pH while electric conductivity and Eh increase during the irradiation. Due to pyrite oxidation sulfate and metastable sulfur oxyanions like thiosulfate and sulfite were formed. The pyrite oxidation in laboratory scale could be influenced by dosage of Fe3+ as electron acceptor.
The results of laboratory experiments are compared with the analyses of groundwater in areas of former lignite mines. While in the laboratory experiments the metastable oxyanions could be detected in higher amounts, the field samples were influenced by two different reaction pathways for sulfur. In the investigated dumps obviously the oxygen supply for the oxidation reactions was limited by diffusion, so that aerobe zones changed to anaerobe. In oxidizing milieu only very low concentrations of thiosulfate and sulfite beside sulfate could be analysed as result of pyrite oxidation. This discrepancy to the laboratory results has still to be discussed. In the anaerobe strata secondary sulfate reduction takes place, producing higher concentrations of the metastable oxyanions.
Wisotzky F, Besondere Mitteilungen zum Deutschen Gewässerkundlichen Jahrbuch, Nr. 58, (1994).
Stream sediments geochemistry has been performed in the base metals mining district of Iglesiente-Sulcis (SW Sardinia). The first results, covering the Southern Iglesiente area (~150 km2) are presented here. Sampling has been carried out with a density of 3 samples per km2. On the whole, 249 samples have been analyzed for 35 elements; further 83 samples, derived from past geochemical survey of Ente Minerario Sardo and analyzed for 11 elements, have been also taken into account for data evaluation.
Cartography of element distribution was obtained by means of a GIS (Grassland). For the compilation of geochemical risk maps, the distribution of regional elements has been reclassified using as thresholds the known intervention criteria for agricultural, residential/recreational and commercial/industrial land use.
The main concentrations of heavy elements mainly follow the carbonate lithologies, where most of the ore deposits (MVT and Sedex) are hosted. Fairly high contents of Ag, Ba, Cd. Cu, Pb, Sb, Zn and As are strictly in agreement with the distribution of stream sediments sampled along the carbonate ridges bordering the area of the Iglesias syncline, in the heart of the mining district. Here are located also treatment plants, tailings and dumps. In the northern part of the syncline, the area around the Monteponi mine is characterized by impressive red dumps ("Fanghi Rossi"=Red Muds), made up by the residues of the treatment of Zn-oxides ores. However, the streams draining the Red Muds around the Monteponi mine contain also high concentrations of other elements, like As, Sb, Bi, Cu, Mn and W. Another polluted area is the swampy river mouth of Rio Sa Masa, near Gonnesa, draining not only the main mining sites of the Iglesias syncline, but also the small industrial areas around the town of Iglesias and of a few villages. This could explain the additional presence of high concentrations of metals not common in the local ores, as Sn, Bi and Co.
The geochemical risk maps have been compiled for 9 elements : Ag, As, Ba, Cd, Cu, Mo, Pb, Sb and Zn. Among those, the state of geochemical pollution is very serious for Ba, Cd, Pb, Zn and As, which are the main elements contained in the stratabound orebodies. The aforementioned elements show a broad distribution far away from their source areas: strictly considered, their contents should forbid any possible use of the territory, unless remediation is carried out.
Sediments of two mining lakes of a closed lignite mine in Mid-Germany (Goitsche near Bitterfeld) were investigated. One of the lakes is extremely acidic (pH 2,5-3) as a result of Fe-sufide oxidation in coal horizon and in the aquifer, where as the second "artificial" lake shows a neutral pH (6,5-7).The small water bodies (mining lakes) were formed as a result of ascending groundwater 6 years ago. In this time a sediment layer of 20 to 40 cm of was deposited.
In April, July and October of 1997 sediment cores were taken and the pore waters extracted. The solid phases and pore waters were analysed and evaluated. Special attention was focused on the distribution and behaviour of extremly enriched Fe in the sediments. Microbial investigations of abundance of Fe-oxidizing and Fe-reducing bacteria were carried out.
In contrast to natural lakes these sediments have a thick "Interface"-layer, which is comparable with a sediment suspension and consists of floc-like Fe-hydroxides. The investigations showed that the main compositions of solid phases of acid and neutral lake sediments were comparable. In the pore water profiles there were significant differences. In the acid mining lake sediments especially temporal changes of the distribution of pH, Fe and DOC in pore waters were observed. In both sediment types the Fe-oxidation and -precipitation on the sediment surface and the dissolution of Fe-hydroxides in the upper layers are the dominant biogeochemical processes in the system. In the acid mining lake sediments the intensity of this processes is dependent on the availability of organic matter. A sulfate reduction could only be proven in neutral lake sediments.
Published estimates for heavy metal emissions from the Ni-Cu industry on the Kola Peninsula in Northwest Russia are reexamined in the light of: a) Official Russian emission figures for 1993 and 1994, b) Modelled deposition based on data from snow and rain sampling in 1994, c) Chemical data on the composition of the ores being processed by the industry. The modelled depositions, official emission figures and chemical data are compatible for Ni, Cu and Co and indicate that assessments previously published in the environmental science literature seriously underestimated the emissions of Ni and Cu. Consideration of the published estimates for trace metal emissions in relation to the modelled depositions and to ore chemical data indicates that earlier assessments overestimated the emissions of several trace metals by up to several orders of magnitude, in some cases exceeding the calculated total input to the plants. These conclusions have implications also for estimates of emissions from the Ni-Cu industries in Siberia (the Noril'sk area) and in the Urals; published estimates of the emissions from these industries would appear to have neglected to recognise the implications of information on the nature of the ores being processed (in the case of the Urals) and on the chemistry of the ores (both Urals and Noril'sk).
Albania has a great potential of mineral resources. They are of a great importance for national economy. Ophiolitic formation has a very high metalogenic potential. Within this formation are concentrated big chromium ore deposits, copper ore deposits, lateritic iron-nickel, nickel-silicate deposits etc.
Albania is distinguished for a high chromium bearing potential, evidenced among the Mediterranean countries which have podiform chromium deposits. It ranks among the main producers and exporters of chromium ore, occupying up till 1990 the third place as the global producer in the world. Chromium ore reserves are estimated about 35 million tonnes with an average content of 32% Cr2O3.
Intensive geological and mining works are carried out during the last four decades. Numerous chromium mines, dressing plants and ferro-chromium smelters are still operating. Actually all chromium dressing plants are amortised, out of technical conditions. Used technological schemes are not modern, causing a considerable lost of chromite ore product. From different used exploitation systems, surface and subsurface in the neighbourhood of the mines is in a dangerous situation and exist the real risk of collapse phenomena, landslides and other natural risks. Enormous mine and technological wastes of chromium industry are widespread in our country, created many environmental problems. Enormous accumulations of chromium sterile stock piles near to the mines and the dams near to the dressing plants are a great environmental problem. Contaminants associated with these areas include heavy metals and from some acid drainage.
According some preliminary environmental studies (the level of contamination), the soils situated around the ferro-chromium dressing plants are strongly contaminated with chromium, nickel, iron and other heavy metal (the paper give the results of this study). The technological wastes of dressing plants have polluted also the ground water, surface water, air, flora and fauna. Nearly all the running water streams are used for the watering of the agriculture and for the other needs of habitants.
Environmental specialised studies for the management and the protection of the territories, where are installed the chromium mines and plants, are strongly needed.
In the Mátra Mts in N. Hungary several inactive dumps of the earlier sulphide ore mining can be found. These dumps may have an important role on heavy metal load of the near soils. The study area is a 20 km2 large drainage basin. This study deals with the effect of a dump on the surrounding soils in sense of heavy metal pollution. Additionally, the heavy metal buffering capacity of the soil in the surrounding area is also tested.The bedrock is Eocene andesite, the main soil type is brown earth. Rainfall is around 650-750 mm/y. A soil profile have been made at the dump, and two others away with a 50 m lag. Each profile has been sampled down to the bedrock at every 5 cms. The following variables were detected: Corg, pH, Cd, Cu, Co, Al, Fe, Mn, Ni, Zn, Pb using aqua regia exposure. Additionally, the mineral components of the soil were also determined using XRD (quartz, feldspars, kaolinit, illite, smectite).The concentrations of the heavy elements exceed significantly the soil average value. They never reach the health limit, but Cu in the topsoil (0-2 cm) is rather close to it (91 ppm). The semi-variogram analysis of the data coming from the soil profiles show that the effect of outer pollution along the profile is detectable down to 15-30 cms. The water infiltrating from the dump increased mainly the Zn, Cd and Cu content in the soil. Nevertheless, using the enrichment factor (proportion of concentration in the <2 m and the > 2 m grain size) the significan part of the heavy metal content in each profile can be regarded mainly lithogeneous. To determine the sensibility of the soil to heavy metals a buffer capacity map was constructed for each metal. In its present state, the soil buffers the elements Cu, Fe and Al well, while in the case of Mn, Ni, Co and Zn areas with lower buffer capacity also exist. Areas with average or low buffer capacity are the largest in the case of Cd. The dump studied is located in an area where Cd is insufficiently buffered. A theoretical model shows that even a slight decrease of pH would mobilize Cd and also Zn, Ni and Co making the dump dangerous for the environment.
Based on results of ecology-geochemical researches in Kamchatka for period of 1991-1997, the condition of an environment witin main gold ore areas were recognized and pollution influence on it from prospect holes were estimated.
Natural geochemical pollution. Gold ore deposits of Kamchatka are the main sources of natural pollution of an environment in ore areas, and could be subdivided into two groups. (1) - a low sulfite deposits (< 1%), in which the harmful impurity in ores such as As, Se, Te, Sb, Ag and to a lesser degree Pb, Zn, Hg, Mo, Mn, Ni, Cu, B occur. A level of pollution in soil is 2-15 LPC (Limit Permissible Concentration), in vegetation - 2-10 BC (Background Concentration), in bottom sediments -2-10 BC, and in superficial water is absent. (2) -deposits with increased sulfite content in ores (3-5%, rarely up to 20%) and wide spectrum of harmful and toxic chemical elements: Pb, Cu, Zn, Cd, Bi, Mn, Mo, As, Hg, Sb, Se. A level of pollution in soil is 3-20 LPC, in vegetation - 5-150 BC, in bottom sediments -5-50 BC, and in superficial water - 2-40 LPC.
Antropogenic geochemical pollution. The main sources of pollution for an environment within the areas of reconnoitered ore deposits are dumps from trenches and edits, miner and drainage water. Dumps of open pit mines occupy the area from 1 to 3-5 km2, on which the soil and vegetative cover were destroyed or essentially broken. They are the most powerful sources of local pollution of an environment. Concentration of Pb, As, Se and S in dumps from the deposits with increased sulfite content in ores 50-100 times exceed LPC, and concentration of Zn, Cu, Sb and Hg 5-10 times exceed LPC. Witin a low sulfite ore deposits, in dumps, concentration of As such as 30-60 LPC, and Se, Sr, Pb, Zn, Mo, Cu, Mnsuch as 2-8 LPC took place.
The pollution from the dumps propagates to on adjoining areas of river valleys (1000-3000 m2), where the content of chemical elements in soil, vegetation and bottom sediments by the order higher than background value. The miner water and drainage from under the dumps represents the greatest danger of pollution for reservoirs. The concentration of following elements in the miner water within the deposits with increased sulfite content in the ores exceed LPC: Zn - 600 times, Pb -5-10, and Se, Cd, Hg, Cu 2-3 times, while within low sulfite deposits the concentration of Zn reachs 13 LPC, As - 2-10 LPC, and Cu -7 LPC. Antropogenic influence of prospecting activity results in pH reduction of river water (up to 3-4) below dumps, increase of SO42- concentration up to 100 mg/l, and increase of the content of all ore elements in a water.
Conclusions: 1. The natural geochemical pollution in gold ore areas of Kamchatka essentially surpasses Antropogenic. 2. The intensity of Antropogenic pollution from dumps of open pit mines grows with increase of sulfite content in ores.
A high risk of sulfide tailings stored as waste piles is mainly determined by a formation of extremely mineralisated acid solutions, which disseminated over the environment as surface and drainage streams. In this presentation we show the results of field experiment demonstrating the reaction of a natural reservoir to inflow of such solutions. To perform of the experiment we had sampled surface and pore waters, which were partially accumulated near the pile foot as unique puddles or disseminated into different environmental components. Sampling had been pursued on the Bericul waste piles, which are the filter cakes for cyanidation of gold-arsenopyrite concentrate. High mineralization and acid medium of the solutions are caused by active interaction of rain waters and soluble salts of metals, which are abundantly formed on the pile slopes (pH = 1.1 - 2.4; content of metals reach up As to 4.5; Zn to 2.3; Cd to 0.04; Fe to 30 g/l). After 1/7000 dilution, a certain portion of the solutions were added into the bounded volume of the natural reservoir (so-called "mesocosm"). Detail observations and sampling at three levels of the water vertical column were carried out during 10 days for two mesocosms. Intervals between sampling were 2, 13 and further at 25 hours. The main objectives of this work were as follows: i) to establish a dynamic of metal elimination from the solutions into sediments; ii) to compare the behavior of different metals in this system; iii) to observe a response of biogeocenosis tto the penetration of high-toxic real solutions into the reservoir.
For all three levels (0, 1.5, 3 m from water surface) concentration of Zn and Cd in the solutions decrease linearly during 10 days. Concentrations of Cu varried irregularly, but ones of As increased. Obviously, these tendencies connect with complex processes of metal exchange between suspension (as organic, so inorganic) and solutions. Models of metal behavior will be discussed in the presentation.
Sharp decrease of phytoplankton number is observed during first day of the experiment due to alteration of physical-chemical conditions of the media. Decrease of zooplankton is a sequence of foot disappearance, direct influence of toxic solution had been not observed. On the base of these results we will show the biogeochemical model describing complex interactions in this system.
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