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PubMed2005

The Wheal Jane wetlands model for bioremediation of acid mine drainage.

Acid mine drainage (AMD) is a widespread environmental problem associated with both working and abandoned mining operations. As part of an overall strategy to determine a long-term treatment option for AMD, a pilot passive treatment plant was constructed in 1994 at Wheal Jane Mine in Cornwall, UK. The plant consists of three separate systems, each containing aerobic reed beds, anaerobic cell and rock filters, and represents the largest European experimental facility of its kind. The systems only differ by the type of pretreatment utilised to increase the pH of the influent minewater (pH <4): lime dosed (LD), anoxic limestone drain (ALD) and lime free (LF), which receives no form of pretreatment. Historical data (1994-1997) indicate median Fe reduction between 55% and 92%, sulphate removal in the range of 3-38% and removal of target metals (cadmium, copper and zinc) below detection limits, depending on pretreatment and flow rates through the system. A new model to simulate the processes and dynamics of the wetlands systems is described, as well as the application of the model to experimental data collected at the pilot plant. The model is process based, and utilises reaction kinetic approaches based on experimental microbial techniques rather than an equilibrium approach to metal precipitation. The model is dynamic and utilises numerical integration routines to solve a set of differential equations that describe the behaviour of 20 variables over the 17 pilot plant cells on a daily basis. The model outputs at each cell boundary are evaluated and compared with the measured data, and the model is demonstrated to provide a good representation of the complex behaviour of the wetland system for a wide range of variables.

Biochemistry↗
PubMed2005

Mercury contamination in farmed fish setup on former garimpo mining areas in the Northern Mato Grosso State, Amazonian region, Brazil.

The garimpo gold mining activity has released about 2.500 tons of mercury in the Brazilian Amazonian environment in the 1980-1995 period. The northern region of Mato Grosso State, an important gold mining and trading area during the Amazonian gold rush is now at a turning point regarding its economic future. Nowadays, the activities related to gold mining have only a low relevance on its economy. Thus, the local communities are looking for economic alternatives for the development of the region. Cooperative fish farming is one of such alternatives. However, some projects are directly implemented on areas degraded by the former garimpo activity and the mercury left behind still poses risks, especially by its potential accumulation in fish. The objective of the present study was to evaluate the levels of mercury contamination in two fish farming areas, Paranaíta and Alta Floresta, with and without records of past gold-washing activity, respectively. Data such as mercury concentration in fish of different trophic level, size, and weight as well as the water physical and chemical parameters were measured and considered. These preliminary data have shown no significant difference between these two fish farming areas, relatively to mercury levels in fish.

Animals↗
PubMed2006

Mobilisation and attenuation of boron during coal mine rehabilitation, Wangaloa, New Zealand.

Environmental mobility and fate of boron has been traced from source to discharge waters through the rehabilitated Wangaloa coal mine in southern New Zealand. The boron is derived initially from coal, which has up to 450 mg/kg B. The coal also contains pyrite (2-5 wt.% S), which oxidizes to yield a low-pH environment (typical pH 2-5). Weathering of coal-bearing waste rock liberates B into rainwater that infiltrates into waste rock or evaporates to leave a gypsum crust enriched in B, possibly as boric acid or colemanite as inferred from geochemical modelling. Surface waters dissolve this evaporative material periodically, yielding total B concentrations up to 6 mg/L, at pH<4.5. Some of the available B is taken up by plants that have been established on the waste rock, resulting in foliage B concentrations of up to 230 mg/kg (dry weight). Partial attenuation of dissolved B by adsorption to iron oxyhydroxide occurs as groundwater passes through waste rock, but this is inhibited by adsorption competition with dissolved sulphate (up to 600 mg/L). Groundwater flows from the mine through a pit lake and wetland, with total dissolved B near 1 mg/kg after dilution and limited adsorption attenuation has occurred. Despite the widespread B mobility throughout the rehabilitated mine, there is little evidence of B toxicity in plants. The B concentrations in discharging waters are in the environmentally safe range for most aquatic organisms, being neither deficient in B as a micronutrient, nor boron-toxic.

Boron↗
PubMed2006

Mobilisation of arsenic from a mining soil in batch slurry experiments under bio-oxidative conditions.

Laboratory investigations were performed to estimate the potential mobility of arsenic (As) from a highly contaminated gold-mining soil under bio-oxidative aerobic conditions as a potential remediation process. The selected soil was sampled from a gold-mining site in the South of France. It contained 27700 mg kg(-1) total As, with only 0.01% present under water-soluble forms. The nature of the immobilization mechanisms was identified by using complementary physical and chemical techniques. As was found to be strongly associated to iron (oxy)hydroxide solid phase by adsorption and/or co-precipitation. Determination of iron (Fe) and As mobility as a function of pH showed that the release of As was related with the dissolution of Fe (oxy)hydroxide at very low pH values. Bioleaching experiments were conducted with the objective to enhance the mobilization of As from the source material via biological oxidation of elemental sulfur (S degree) into sulfuric acid by autotrophic exogenous or indigenous bacteria naturally located in the soil (i.e. Acidithiobacillus species). Tests conducted at 30 degrees C in shaker flasks supplemented with S degree resulted in very acidic (pH < 1) and oxidative conditions (oxidation/reduction potential (ORP) around +800 mV vs. NHE) and induced the extraction of up to 35% of As over 84 days of incubation. Under the experimental conditions of the study (batch experiments), As mobilization was strongly correlated to the dissolution of Fe solid phases. As mobilization was probably limited by the saturation of the liquid phase. Chimiolithotrophic exogenous population appeared to have a minor effect on As bioleaching. Endogenous populations were shown to rapidly develop their capacity to oxidize S degree and mobilize As from the mining soil in the form of arsenate when elemental S degree was supplemented. The use of microbial population adapted to high As concentrations reduced significantly the lag period to reach optimal pH/ORP conditions, and increased As extraction rate to a maximum of 41% within 70 days of incubation. However, As reprecipitation was subsequently observed, suggesting that the solution should be periodically replaced in order to optimize the process.

Acidithiobacillus↗
PubMed1997

Acid leaching studies of chrysotile asbestos from mines in the Coalinga region of California and from Quebec and British Columbia.

The dissolution of magnesium (Mg) and silicon (Si) from various samples of chrysotile asbestos was measured in N HCl at 25 degrees C. Nine samples were used, five from Canada and four from the Coalinga deposit in California. With milled samples from Quebec, the fraction of Mg dissolving was linearly related to the square root of the leaching time until at least 65% had dissolved. With a hand-picked sample of ore from Quebec, the sample from British Columbia and all the Californian samples, the Mg leaching patterns were sigmoid. The leaching patterns for Si were sigmoid in shape for all the materials tested. Mean Mg dissolution rates were calculated for each leaching period. Considerable differences were observed between samples from the different mining regions and also between hand-picked and milled samples from the same mine. Initially, Mg dissolved more rapidly from milled Quebec chrysotiles than from the Coalinga samples. This difference is due in part to the rapid dissolution of non-structural brucite, present in all the samples from Quebec but not in those from California. An additional cause is greater damage to the fibre surfaces resulting from the milling to which the less readily-opened fibres, typical of the Quebec mining area, were subjected. Once this readily-available Mg had dissolved, there was little difference in leaching rates between milled and unmilled samples from the different regions. When the fraction of Mg dissolving is plotted against that of Si, all the materials follow a similar pattern, suggesting that the dissolution of Si (as silica) is the rate-controlling step in the dissolution of Mg.

Asbestos, Amphibole↗
PubMed2002

Evaluation of major constraints to revegetation of lead/zinc mine tailings using bioassay techniques.

The residues from the extraction of lead/zinc (Pb/Zn) ores of most Pb/Zn mines are permanently stored in tailings ponds, which require revegetation to reduce their environmental impact. This can only be done if the main constraints on plant establishment are evaluated. This can readily be done by field and greenhouse studies. To test this, the properties of different tailings from Lechang Pb/Zn mine located at the north of Guangdong Province in southern China have been studied. Physical and chemical properties including concentrations of metals (Pb, Zn, Cd and Cu) in the tailings and soils collected from different sites have been measured. The results showed that tailings contain low nitrogen (0.016-0.075%), low-organic matter (0.58-1.78%), high salt (3.55-13.85 dS/m), and high total and diethylene-tetramine-pentaacetic acid (DTPA)-extractable metal concentrations (total: 1,019-1,642 microg g(-1) Pb, 3,078-6,773 microg g(-1) Zn, 8-23 microg g(-1) Cd, and 85-192 microg g(-1) Cu; DTPA-extractable: 59-178 microig g(-1) Pb, 21-200 microg g(-1) Zn, 0.30-1.5 mcirog g(-1) Cd, and 4.3-12 microg g(-1) Cu). Aqueous extracts of tailings/soils (10%, 20% and 30%, w/v) from different sites were prepared for testing their effects on seed germination and root elongation of a vegetable crop Brassica chinensis and a grass species Cynodon dactylon. It was found that root elongation provided a better evaluation of toxicity than seed germination. The ranking of toxicity using root elongation was: high-sulfur tailings > tailing dam > sparsely vegetated tailings > densely vegetated tailings > mountain soil for both plants. This order was consistent with DTPA-extractable Pb contents in the tailings and soils. B. chinensis seedlings were then grown in the mixtures of different proportions of tailings and farm soil for 4 weeks, and the results (dry weights of seedlings) were in line with the root elongation test. All these demonstrated that heavy metal toxicity, especially available Pb, low content of nutrient, and poor physical structure were major constraints on plant establishment and colonization on the Pb/Zn mine tailings.

Biodegradation, Environmental↗
PubMed1999

Arsenic in the food chains of a revegetated metalliferous mine tailings pond.

The environmental distribution, transfer and ecotoxicological risk associated with arsenic in a grassland ecosystem established on metalliferous mine tailings has been determined. High levels of arsenic in the mine tailings (630 +/- 34 mg kg-1) were not reflected in live vegetation due to the physico-chemical nature of the tailings which mitigate against plant uptake. However, elevated levels of arsenic were associated with plant litter. Low concentrations of arsenic in herbivorous invertebrates mirrored those found in their food, although there was evidence of minor detrivoral food chain transfer. Dietary exposure of small mammals to arsenic was well below that demonstrated to induce a toxicological response, and tissue concentrations were consistently below analytical detection limits. There appears to be little ecotoxicological risk associated with arsenic residues at the mine site investigated.

Animals↗
PubMed2002

Distributions of arsenic and selenium in selected Chinese coal mines.

The contents of arsenic and selenium in 33 coals collected from the main coal mines in northeastern, northern and eastern China were determined by flow injection-hydride generation and non-dispersion atomic fluorescence spectrometry (HGAFS). The concentrations of As in the northeast region are relatively higher with the values > 100 microg g(-1); in the east they are lower with values < 100 microg g(-1). The contents of Se in these three areas are the opposite, most of them from the northeast mines are < 1 microg g(-1) and increase as the mine location advances south where the average contents are > 5 microg g(-1).

Arsenic↗
PubMed2004

Porphyrin metabolism in lymphocytes of miners exposed to diesel exhaust at oil shale mine.

The present study was carried out on the evaluation and application of new biomarkers for populations exposed to occupational diesel exhaust at oil shale mines. Since not only genotoxic effects may play an important role in the generation of tumors, the level of porphyrin metabolism was proposed as a biomarker of diesel exhaust exposure effects. The data on determination of 5-aminolevulinic acid (ALA) synthesis and heme formation in lymphocytes from groups of 50 miners exposed to diesel exhaust and 50 unexposed surface workers of oil shale mine are presented. All workers were examined and interviewed using structured questionnaires. The levels of benzene, carbon monoxide and nitric oxides in air as well as concentrations of 1-nitropyrene and elemental carbon in particulate matter were used for evaluation of exposure to diesel exhaust in mine. The levels of ALA and protoporphyrin (PP), activities of ALA synthetase (ALA-S) and ferrochelatase (FC), as well as levels of PP associated with DNA (PP/DNA) were investigated in lymphocytes spectrophotometrically. Significant differences in activity of ALA synthesis and heme formation between exposed miners and surface workers were found (207+/-23 vs. 166+/-14 pmol/10(6) lymp./30' for ALA-S and 46.1+/-3.8 vs. 54.8+/-4.1 pmol/10(6) lymp./60' for FC activities, respectively, P<0.001). ALA-S activity was higher and ALA accumulated in lymphocytes of exposed miners. Inhibition of FC activity caused PP cellular accumulation and an increase in the PP/DNA level (P<0.05). Tobacco smoking led to the increase of ALA biosynthesis in lymphocytes of both surface and underground smokers. The comparison of data obtained for non-smokers and smokers of both groups of workers has shown a significant difference (P<0.05). The work duration of underground or surface workers did not significantly influence the investigated biochemical parameters. The determination of ALA synthesis in lymphocytes could be a useful biomonitoring index of organism sensitivity to underground working. The alterations of PP levels, FC activity and PP/DNA association in peripheral lymphocytes of miners illustrate the harmful effects of exposure to diesel exhaust.

Adult↗
PubMed1999

The impact of the Aznalcóllar mine tailing spill on groundwater.

As a consequence of a mine tailing dam collapse on the 25th April 1998, more than 4000 ha of the Guadiamar riverflat and farmlands were flooded by 4 hm3 of sulphide slurry. A number of open wells (12 of the 47 analyzed) were also flooded and the water was contaminated. Before the spill, the groundwater in the aquifers was of calcium-carbonate and calcium-sulphate type, with moderate mineralisation and near neutral pH. With the exception of some of the wells close to the mine, this groundwater had a low concentration of the metals associated with the Aznalcóllar mine. After the flood the following metals had anomalous concentrations in well water: Zn, Mn, Pb, Co, Cd and Tl. Of these, Zn seems to be the best tracer of the contamination, owing to its high concentrations. During the 5 months following the spill, water from the unflooded wells did not show an increase in metal concentration. Apart from some exceptions in August, the metal concentration in the affected wells showed a progressive decrease reaching levels closer to those in the wells free from contamination. Nevertheless, in the following dry seasons the draw-down of the water level may lead to exposure and weathering of sulphides in the wells, which could cause an increase in pollution. Therefore, thorough cleaning of all highly contaminated wells is strongly recommended.

Accidents, Occupational↗
PubMed2003

Applying foraminiferal stratigraphy as a biomarker for heavy metal contamination and mining impact in a fiord in West Greenland.

Sulphidic mine waste disposed in marine environments constitutes an environmental risk to aquatic life due to potential uptake and accumulation of heavy metals in biota. Fiord sediments near the former Black Angel Mine in West Greenland are contaminated by lead and zinc as a result of submarine tailings disposal in 1973-1990. In 1999 cores were taken up to 10 km away from the disposal area. Analyses include heavy metals, radiochemical dating (210Pb) and high-resolution foraminiferal stratigraphy. The mining operation resulted in significant changes in the assemblage composition. In addition, up to 20% of the Melonis barleeanus population found in sediment deposited during nearby tailings disposal was deformed compared to a natural background of less than 5%. Throughout cores representing the last 100 years of sedimentation, the total numbers and frequency of morphological abnormalities among M. barleeanus revealed some correlation with heavy metals concentrations (up to r2 = 79%). We conclude that abnormalities among foraminifera may represent a useful biomarker for evaluating trends in the biological impact resulting of submarine tailings disposal as well as long-term environmental impact and subsequent recovery.

Animals↗
PubMed2004

Toxic effects of mining effluents on fish gills in a subarctic lake system in NW Russia.

The mining company Karelian Pellet in northwestern Russia extracts iron ore and processes it locally into pellets. The production operations affect the environment in the form of air pollution and wastewater emissions to lakes downstream from the factory. The toxic effects of the mining effluents on gills of perch (Perca fluviatilis) and roach (Rutilus rutilus) were studied. In lakes close to the factory, heavy metal concentrations in gills were not high, even though the metal content in sediment was elevated. In fish gills the relative proportion of phosphatidylcholine was elevated and cholesterol reduced, while the histological structure of the gills was changed. The number of mucus cells, as well as the sizes and the lengths of open areas in the chloride cells, had increased in spring and summer. The hypertrophy of chloride cells is possibly caused by the increased ambient concentrations of K+ and Li+. Changes in gill cholesterol and phospholipid proportions increase the fluidity of membranes and possibly strengthen their protective qualities, counterbalancing the adverse changes in chloride cell structure. The bioavailability and toxic effects of metals on fish are reduced by the hardness and high pH of water discharged by the mining plant.

Animals↗
PubMed2000

Sources of air pollution due to coal mining and their impacts in Jharia coalfield.

Indian coal consumption is about 5.5% of the world and the share of coal as energy went up to 66%. The increasing trend of opencast coal mining lead to release of dust and gaseous pollutants. The Indian reserve of coking coal is mainly located in Jharia coalfield and having reserves upto a depth of 1219m are 19339 Mt. The coalfield is subjected to intensive mining activities and accounts for 30% of the total Indian coal production. Coal mining in Jharia coalfield and the sources of air pollution along with the production of air pollutants have been described. The dust particles act as centres of catalysis for many of the chemical reactions taking place in the atmosphere. Characteristics and effects of the pollutants have been discussed. An estimate of the dust generated and discharged into the atmosphere can be made by using emission factor or prediction type equations. It is disirable that this exercise is to be undertaken in planning stage so that adequate and appropriate mitigating measures can be incorporated into the project at least cost.

Air Pollutants, Occupational↗
PubMed2001

Growth response of Sesbania rostrata and S. cannabina to sludge-amended lead/zinc mine tailings. A greenhouse study.

Legumes are ideal for revegetation of metal-mined wastelands which lack nitrogen (N). A greenhouse study was conducted to investigate the feasibility of using Sesbania rostrata and S. cannabina for the reclamation of lead/zinc (Pb/Zn) mine tailings and to evaluate the effects of organic amendment using sewage sludge (0%, 25%, 50%, and 75%, v/v). The results showed that both species could continue to grow on the highly toxic tailings substrata for at least 80 days, although their growth suffered from adverse effects. That S. rostrata with stem and root nodules had better growth (biomass, growth rates, and biomass of nodules) than S. cannabina suggested that S. rostrata is a better choice as a pioneer species for revegetation of the mine tailings. Stem nodules had less obvious adverse effects imposed by tailings than root nodules. Application of sewage sludge increased contents of total carbon (C), N, phosphorus (P), and potassium (K), and reduced total Zn, Pb, Cd, and DTPA-extractable Pb and Cd in tailings substrata. These, in turn, reduced metal (Zn, Pb, and Cd) uptake and accumulation in plant tissues, and improved plant growth performance, including biomass, growth rates, stem nodulation. Fifty percent (v/v) of sludge application rate was the best loading rate for plant growth.

Biomass↗
PubMed2002

Heavy metal concentrations in Squilla mantis (L.) (Crustacea, Stomatopoda) from the gulf of cadiz evaluation of the impact of the Aznalcollar mining spill.

After the Aznalcóllar mining spill (25th April 1998), considerable social concern arose amongst the inhabitants of the SW Iberian Peninsula concerning the consumption of local seafood. Squilla mantis was collected in four regions of the Gulf of Cádiz with a dual objective: to analyze the heavy metal levels for human consumption and as part of biomonitoring program. Heavy metal concentrations (Fe, Mn, Zn, Cu, Cd and Pb) were analyzed in soft tissues and cuticle. The highest values were found in the soft tissues for zinc, copper and cadmium and in the cuticle for iron, manganese and lead. The mean copper concentration in the soft tissue, corresponding to the edible part, was 27.1 microg x g(-1) wet weight. Approximately 80% of stations showed values higher than 20 microg x g(-1) wet weight of copper, the Spanish legal limit for the concentration of this metal in the crustacean for human consumption. For Zn and Cu no significant differences were found between regions, probably related with the capacity for regulation of S. mantis. The highest values found for copper in the Gulf of Cádiz compared to other areas is likely to be related with contamination from terrestrial mining activities (copper and pyrites) in the region, dating back to the times of Tartessians and Romans, rather than the effects of mining spill which was shown not to create any significant increases in heavy metal concentrations of organisms of the Guadalquivir River or the adjacent coastal area.

Animals↗
PubMed2004

Hydrochemical stratification in flooded underground mines: an overlooked pitfall.

The fact that flooded underground mines are commonly hydrochemically stratified is often not appreciated. Water samples taken from the water surface in partly flooded shafts are often wrongly assumed to represent the water quality existing throughout the entire water column. In some cases, treatment systems have been designed on the basis of these often misleading water surface samples. Stratification can build up within a slowly recovering system where there are few lateral inflows and outflows to the system. Less mineralised, shallow-sourced water enters at the top of the water column and more heavily mineralised water tends to remain at the base of the water column. This water has a high dissolved solids content due to dissolution of increasing amounts of pyrite oxidation salts and other minerals as the water level rises through the old workings. However, such stratification can easily be lost following hydraulic disturbance of the system (either by pumping or by natural decant when the water level reaches an outflow pathway from the mine system, such as an old adit or shaft collar) and often results in surface discharges of poor water quality. Test pumping of one such stratified system (Frances Colliery, Scotland) has provided useful information about how stratified systems develop, and how they can behave when disturbed. The water quality observed after stratification was disturbed by pumping was worse than would have been anticipated on the basis of water samples taken from the surface of the water column prior to pumping (with concentrations of contaminants such as iron and zinc being around two orders of magnitude greater than in water surface samples). Taken together with other information from the literature, the experience at Frances Colliery supports the proposal of criteria for recognising when stratification of mine water quality might be anticipated, thus facilitating the timely deployment of measures required for its detection at an early stage.

Disasters↗
PubMed2004

Assessment of the radiological impacts of historical coal mining operations on the environment of Ny-Alesund, Svalbard.

Mineral extraction activities, such as those conducted by oil, gas and coal industries, are widespread throughout the Arctic region. Waste products of these activities can result in significant contributions to the radioactive burden of the surrounding environment due to increased concentrations of naturally occurring radioactive materials (NORM) to levels that would not normally be found in the environment. Coal mining operations commenced in the early 1900s on Svalbard and have been conducted at a variety of locations on the archipelago since then. Coal contains radionuclides of the uranium and thorium series as well as 40K. Extraction and processing of coal can result in releases of these radionuclides to the broader environment with subsequent impact on the human and non-human inhabitants of the area. This paper presents the results of a study on environmental radioactivity resulting from historical coal mining operations conducted at Ny-Alesund, Spitsbergen, in the Svalbard archipelago. Activity concentrations of radionuclides found in materials associated with these operations are presented as well as the results of a spatial dosimetric survey conducted over an area affected by coal mining.

Arctic Regions↗
PubMed2003

Study of fractionation and potential mobility of metal in sludge from pyrite mining and affected river sediments: changes in mobility over time and use of artificial ageing as a tool in environmental impact assessment.

Sludge from mining exploitation can be a source of land and water contamination in the adjacent zone. Accidents such as the break of waste mining pools in the Aznalcollar Mine (Seville, Spain) in 1998 produce important ecological disasters. In this work is presented a study of the evolution of aqua regia leachable concentration and mobility of metals in sediment samples of Guadiamar River basin from the accident date up to 2001. The application of BCR standard extraction procedures provides valuable information about the mobility and toxicity of the spill and the metal mobility in Guadiamar River polluted sediments. As a rule, themobility of several metals in the initial sludge (sulphides) is low, except for copper. Otherwise, the results of aqua regia leachable concentration and mobility of metal obtained for sediments samples indicate that the cleaning and inertisation works carried out in the zone have been adequate but insufficient, being the metal levels observed in the zone are higher than natural levels. To establish the initial impact of the spill and the mobility changes with time, mineralogical composition of the pyritic sludge and its evolution after the natural weathering and after the induction, of accelerated ageing processes by light and temperature was studied in the laboratory. Oxidation of initial sulphides to sulphates was observed. Both environmental and laboratory oxidation of the metallic sulphides increase the mobility of all metals, especially of copper, zinc and lead. The proposed laboratory procedure allows to predict the changes in mobility and therefore in toxicity that can occur at short or long term after exposure of sludge at environ-mental conditions. The mobility results in sludge and sediment samples are interpreted in terms of the mineral composition of the samples.

Chemical Fractionation↗