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PubMed2006

Evaluation of remediation of coal mining wastewater by chitosan microspheres using biomarkers.

Acidic mine waters have a marked influence on the surrounding environment and pose a serious threat through long-term environmental degradation. Therefore, it is important to improve and monitor water quality with the aim of decreasing the hazard presented by this effluent emission. The aim of this work was to evaluate the remediation of mining wastewater effluents by chitosan microspheres using biomarkers of exposure and effect. DNA damage (Comet assay) and several biomarkers of oxidative stress, such as lipoperoxidation levels (TBARS), superoxide dismutase (SOD), catalase (CAT), and glutathione S-transferase (GST) activities, and contents of reduced glutathione (GSH), were measured in blood and liver of tilapia (Oreochromis niloticus) exposed for 7, 15, and 30 days to dechlorinated tap water, 10% coal mining wastewater (CMW), and coal mining wastewater treated with chitosan microspheres (RCM). The results indicate that hepatic TBARS levels were significantly higher in fish exposed to CMW after 7, 15, and 30 days (100%, 86%, and 63%, respectively), and after remediation there was no significant difference in relation to the control group. Hepatic GSH concentrations were lower than control values for CMW after 7 and 15 days of exposure (34% decrease at both times), and this concentration was normalized by treatment with chitosan. SOD showed increased activity in liver after 15 and 30 days of exposure, 30% and 36%, respectively, and in fish exposed to RCM there was no change in this activity compared with the control group. Increased CAT activity in liver was observed during all experimental periods in fish exposed to CMW (46%, 50%, and 56% at 7, 15, and 30 days, respectively) compared with the control or treated-water groups. The highest increase in hepatic GST activity (106%) was observed only in fish exposed to CMW for 30 days. There was an increase in DNA damage in liver (50% at 7 and 15 days) and blood (79%, 77%, and 48% at 7, 15, and 30 days, respectively) after exposure to CMW. In contrast, the fish exposed to wastewater treated with chitosan microspheres exhibited DNA fragmentation indexes similar to the control group. The results obtained indicate the use of oxidative stress biomarkers as useful tools for the toxicity evaluation of coal mining effluents and also suggest that chitosan microspheres may be used as an alternative approach for remediation of coal mining wastewaters.

Animals↗
PubMed2006

Microbial studies of a selenium-contaminated mine site and potential for on-site remediation.

Surface water Selenium (Se) concentrations are above regulatory standards at several active and inactive phosphate mine sites in the US Western Phosphate Resource Area. The focus of the present study was to examine the impacts of the microbial communities on the oxidation state of Se in overburden waste from the Smoky Canyon phosphate mine in Idaho, USA. Microbial populations were found that reduce soluble selenate (SeO (4) (2-) ) to insoluble elemental Se. Microcosm experiments were conducted for molecular genetic analysis of this microbial community by rRNA gene profiling. An acetone pretreatment step was developed to remove interfering pre-petroleum hydrocarbons from the samples prior to extraction. PCR was used to amplify 16S and 18S rRNA genes present in the microbial community DNA. The amplified products were subjected to denaturing gradient gel electrophoresis (DGGE). Isolates and excised DGGE bands were amplified and sequenced for identification to determine the relative importance of culturable isolates to the total microbial population. Analysis of samples from different sites at the mine showed how Se contamination and previous remediation treatments changed the microbial populations across the site. Members of the family Enterobacteriaceae were dominant among the selenate reducing isolates from the site containing high Se levels. In particular, Serratia fonticola was isolated repeatedly from contaminated Smoky Canyon Mine site samples. Packed column studies were performed with seleniferous waste rock fractions from Smoky Canyon Mine. Column amendments consisted of combinations of iron, compost, and whey. Eh, pH, and extractable Se measurements were taken. Tests with infiltrated water showed columns containing an organic amendment combined with iron metal were the most resistant to Se leaching. Iron-based compounds from the corroding metal are thought to strongly bind the Se reduced by microbial activity, thereby stabilizing the Se in an insoluble form. We conclude that long-term stabilization of selenium at contaminated mine sites may require reductive microbial processes combined with abiotic immobilization by iron, either natural or engineered, to stabilize the Se and retard re-oxidation and release. Iron-selenide or iron-selenite compounds are more stable and resistant to leaching, especially when removed from active weathering.

Biodegradation, Environmental↗
PubMed2006

Human risk assessment for heavy metals and as contamination in the abandoned metal mine areas, Korea.

Cleanup goals for the contaminated sites are established on the basis of risk assessments and rely on the estimated toxicity of the chemicals of concern (COC). Toxicity estimates are based on bioavailability causing risk of adverse health effects on humans. In this study, bioavailability of As, Cu, Pb and Zn in soil was determined by SBET (Simple Bioavailability Extraction Test), and chemical analysis for groundwater and stream water collected from the abandoned mine areas (Dukeum, Dongil, Dongjung, Myungbong and Songchun mine areas) was conducted. High values of cancer risk for As (1.16x10(-5)) were detected through soil ingestion pathways in the Songchun mine area and assessed through water exposure pathways in the all mines except Dukeum. The hazard index value for As in the Songchun mine area (3.625) exceeded 1.0. The results indicated that the ingestion of As-contaminated soil and water by local inhabitants can pose a potential health threat in these mine areas.

Arsenic↗
PubMed2006

Geographic variability in radon exhalation at a rehabilitated uranium mine in the Northern Territory, Australia.

In this study, dry season radon flux densities and radon fluxes have been determined at the rehabilitated Nabarlek uranium mine in northern Australia using conventional charcoal canisters. Environmental background levels amounted to 31+/- 15 milli Becquerel per m(2) per second (mBq m(-2) s(-1)). Radon flux densities within the fenced rehabilitated mine area showed large variations with a maximum of 6500 mBq m(-2) s(-1) at an area south of the former pit characterised by a disequilibrium between (226)Ra and (238)U. Radon flux densities were also high above the areas of the former pit (mean 971 mBq m(-2) s(-1)) and waste rock dump (mean 335 mBq m(-2) s(-1)). The lower limit for the total pre-mining radon flux from the fenced area (140 ha) was estimated to 214 kBq s(-1), post-mining radon flux amounted to 174 kBq s(-1). Our study highlights that the results of radon flux studies are vitally dependant on the selection of individual survey points. We suggest the use of a randomised system for both the selection of survey points and the placement of charcoal canisters at each survey point, to avoid over estimation of radon flux densities. It is also important to emphasize the significance of having reliable pre-mining radiological data available to assess the success of rehabilitation of a uranium mine site.

Air Pollutants, Radioactive↗
PubMed2006

Atmospheric monitoring at abandoned mercury mine sites in Asturias (NW Spain).

Mercury concentrations are usually significant in historic Hg mining districts all over the world, so the atmospheric environment is potentially affected. In Asturias, northern Spain, past mining operations have left a legacy of ruins and Hg-rich wastes, soils and sediments in abandoned sites. Total Hg concentrations in the ambient air of these abandoned mine sites have been investigated to evaluate the impact of the Hg emissions. This paper presents the synthesis of current knowledge about atmospheric Hg contents in the area of the abandoned Hg mining and smelting works at 'La Peña-El Terronal' and La Soterraña, located in Mieres and Pola de Lena districts, respectively, both within the Caudal River basin. It was found that average atmospheric Hg concentrations are higher than the background level in the area (0.1 microg Nm(-3)), reaching up to 203.7 microg Nm(-3) at 0.2 m above the ground level, close to the old smelting chimney at El Terronal mine site. Data suggest that past Hg mining activities have big influences on the increased Hg concentrations around abandoned sites and that atmospheric transfer is a major pathway for Hg cycling in these environments.

Air Pollutants↗
PubMed2006

Influence of mining activities in the North of Potosi, Bolivia on the water quality of the Chayanta River, and its consequences.

Mining activity in the North of Potosi (Siglo XX mine, Ingenio Catavi-Siglo XX, Pucro mine and Colquechaca mine) produces minewater containing high concentrations of heavy metals such as As (0.02-34 mg/l), Cd (45-11,600 microg/l), Cu (0.35-32 mg/l), Fe (42-1,010 mg/l), Pb(33-3,130 microg/l), Ni(20-4,320 microg/l), and Zn (1.1-485 mg/l), that exceed considerably the limit values. The rivers in the North of Potosi (Katiri and Pongoma) that do not receive minewater contain clear water with rather low heavy metal concentrations. These rivers and also other rivers contaminated with minewater, are tributaries of the Chayanta River that transports water with a high concentration of heavy metals such as As (6-24 microg/l), Cd (260-2,620 microg/l), Cu (205-812 microg/l), Pb(10-21 microg/l) and Ni(110-332 microg/l). These elements result from mining activity, as indicated by a comparison with rivers not contaminated by minewater discharges. Water of the Chayanta River, used all year long by the population of Quila Quila, (a village situated at about 75 km from the mining centers), for the irrigation of crops such as potato, maize and broad bean, contains heavy metal concentrations exceeding for several elements the guidelines for irrigation. As drinking water the population of Quila Quila consumes spring water with a generally acceptable heavy metal concentration, as well as infiltrated water of Chayanta River (which is also used in animal drinking troughs) with a high concentration of Cd (23-63 microg/l), exceeding the limit value for drinking water. The metal concentration is significantly lower in the infiltrated water than in the water of Chayanta River. Some technological solutions are suggested to improve the quality of the water used. Surveys carried out on inhabitants of the region, showed that many people present health problems, probably to be attributed to the bad quality of the water they consume and use for irrigation.

Bolivia↗
PubMed1985

Multinomial logit analysis of injury severity in U.S. underground bituminous coal mines, 1975-1982.

Relationships among mine and injured miner characteristics and degrees of injury are examined for 91 404 injuries in underground bituminous coal mines in the United States from 1975 through 1982. Injury severity varies by the mining system, geographical region, circumstances surrounding the injury, the injured miner's age, whether the miner was using powered equipment, the year in which the injury occurred and the location in the mine where the injury happened. Injury severity is not related to the injured miner's total mining experience, job experience and experience in the mine in which the injury occurred.

Adult↗
PubMed1985

Investigation of mine and industry dumps in the FRG in relation to a possible release of natural radioactive elements.

More than 350 dumps of mines and industries in two federal states of the FRG were recorded, measured radiometrically, evaluated, and some of them sampled. Most of the mine dumps belonged to old and smaller residues from lead/zinc and iron ore mining, while the largest depositions contain tailings of modern ore beneficiation or flyash disposal. All mine dumps from uranium exploration in Baden-Württemberg and Bavaria were investigated. The highest doses, up to 100 mSv/a, were found on the piles of the uranium exploration. These depositions, which are supervised and licensed, are followed, in terms of surface dose, by the old uncontrolled mine dumps of silver/cobalt mining with doses up to 20 mSv/a. The numerous porphyry and granite quarries show doses between 1 and 2 mSv/a, as do flyash and slag dumps. The lowest doses were found on the dumps of the hydrothermal Pb/Zn and iron ore deposits, while the slag piles of iron ore processing showed higher thorium values. Assays for Ra-226 and Pb-210 of the materials deposited confirmed the radiometric results. Analyses of seepage waters and gallery waters showed only very few values exceeding the derived drinking water concentrations.

Environmental Pollution↗
PubMed2004

Occupational exposure of phosphate mine workers: airborne radioactivity measurements and dose assessment.

Under the Egyptian program for radiation safety and control, airborne radioactivity measurements and radiological dose assessment were conducted in some phosphate and uranium mines. Abu-Tartor mine is one of the biggest underground phosphate mines in Egypt. Airborne radioactivity, radon ((222)Rn) and its short-lived decay products (progenies) and thoron ((220)Rn), were measured in selected locations along the mine. The environmental gamma and workers dose equivalent rate (mSv/y) were measured inside and outside the mine using thermo-luminescence dosimeters (TLD). The results were presented and discussed. The calculated annual effective dose due to airborne radioactivity is the main source of occupational exposure and exceeding the maximum recommended level by ICRP-60 inside the mine tunnels. A number of recommendations are suggested to control the occupational exposures.

Air Pollutants, Radioactive↗
PubMed2006

Effect of solids concentration on removal of heavy metals from mine tailings via bioleaching.

Mining of mineral ore and disposal of resulting waste tailings pose a significant risk to the surrounding environment. The objective of this work is to demonstrate the feasibility to remove heavy metals from mine tailings with the use of bioleaching and meanwhile to investigate the effect of solids concentration on removal of heavy metals from mine tailings by indigenous sulfur-oxidizing bacteria and the transformation of heavy metal forms after the bioleaching process. This work showed the laboratory results of bioleaching experiments on Pb-Zn-Cu mine tailings. The results showed that 98.08% Zn, 96.44% Cu, and 43.52% Pb could be removed from mine tailings by the bioleaching experiment after 13 days at 1% (w/v) solids concentration and the rates of pH reduction, ORP rise and sulfate production were reduced with the increase of solids concentration, due to the buffering capacity of mine tailing solids. The results also indicated that solid concentration 1% was found to be best to bacterial activity and metal solubilization of the five solids concentration tested (1%, 2%, 5%, 8% and 10%) under the chosen experimental conditions. In addition, the bioleaching had a significant impact on changes in partitioning of heavy metals.

Biodegradation, Environmental↗
PubMed2004

Heavy metal bioaccumulation and macroinvertebrate community changes in a Mediterranean stream affected by acid mine drainage and an accidental spill (Guadiamar River, SW Spain).

In the 1998 Aznalcóllar mining accident, 5 million cubic meters of toxic waste were spilled into the Guadiamar River (SW Spain). This paper describes the likely effects of metal pollution on the macroinvertebrate community in the first 15 km of the river adjacent to the mine, 2 years after the spill. The contents of Zn, Cu, Pb, As, Cd, Tl, and Sb in water, sediment, and in the caddisfly Hydropsyche were analysed, together with some physico-chemical parameters. From the results of physico-chemical and community parameters, the studied area was divided into three sections: the first section contained upstream control stations, not affected by current mining activities, and with a diverse macroinvertebrate community structure (mean number of families = 19); the second section, close to the mine, was severely polluted, with more than 50 mg l(-1) of Zn or 1.6 mg l(-1) of Cu in water, a pH of nearly 4, and a very diminished macroinvertebrate community (three families); in the last section, 6-15 km downstream from the mine, the water quality improved, metal concentrations decreased, pH reached neutrality and the macroinvertebrate community comprised eight families. We also determined metal concentrations in the larvae of Hydropsyche and found increases of 3- to 35-fold (for Cu and Cd, respectively) compared to control sites. As far as we are aware, these values are the highest concentrations so far detected in this caddisfly anywhere in the world. Different patterns of metal and pH tolerance were identified in macroinvertebrates. Most of the species were intolerant to present pollution levels and were only present in control sites. Others were tolerant to metal pollution but not to low pH and were present in the main river downstream of the mine, while a very few species managed to live in the most polluted section, with very low pH and high metal concentrations.

Accidents, Occupational↗
PubMed2005

Accumulation of arsenic in Lemna gibba L. (duckweed) in tailing waters of two abandoned uranium mining sites in Saxony, Germany.

Accumulation of arsenic in Lemna gibba L. was investigated in tailing waters of abandoned uranium mine sites, following the hypothesis that arsenic poses contamination risks in post uranium mining in Saxony, Germany. Consequently, macrophytes growing in mine tailing waters accumulate high amounts of arsenic, which might be advantageous for biomonitoring arsenic transfer to higher trophic levels, and for phytoremediation. Water and L. gibba sample collected from pond on tailing dumps of abandoned mine sites at Lengenfeld and Neuensalz-Mechelgrun were analysed for arsenic. Laboratory cultures in nutrient solutions modified with six arsenic and three PO(4)(3-) concentrations were conducted to gain insight into the arsenic-L. gibba interaction. Arsenic accumulation coefficients in L. gibba were 10 times as much as the background concentrations in both tailing waters and nutrient solutions. Arsenic accumulations in L. gibba increased with arsenic concentration in the milieu but they decreased with phosphorus concentration. Significant reductions in arsenic accumulation in L. gibba were observed with the addition of PO(4)(3-) at all six arsenic test concentrations in laboratory experiments. Plant samples from laboratory trials had on average twofold higher bioaccumulation coefficients than tailing water at similar arsenic concentrations. This would be attributed to strong interaction among chemical components, and competition among ions in natural aquatic environment. The results of the study indicate that L. gibba can be a preliminary bioindicator for arsenic transfer from substrate to plants and might be used to monitor the transfer of arsenic from lower to higher trophic levels in the abandoned mine sites. There is also the potential of using L. gibba L. for arsenic phytoremediation of mine tailing waters because of its high accumulation capacity as demonstrated in this study. Transfer of arsenic contamination transported by accumulations in L. gibba carried with flowing waters, remobilisation through decay, possible methylisation and volatilisation by L. gibba need to be considered.

Araceae↗
PubMed2005

Metal contamination of soils and crops affected by the Chenzhou lead/zinc mine spill (Hunan, China).

In 1985, the collapse of the tailing dam in Chenzhou lead/zinc mine (Hunan, southern China) led to the spread of mining waste spills on the farmland along the Dong River. After the accident, an urgent soil cleaning up was carried out in some places. Seventeen years later, cereal (rice, maize, and sorghum), pulses (soybean, Adzuki bean, mung bean and peanut), vegetables (ipomoea, capsicum, taro and string bean) and the rooted soils were sampled at four sites: (1) the mining area (SZY), (2) the area still covered with the mining tailing spills (GYB), (3) the cleaned area from mining tailing spills (JTC), and (4) a background site (REF). Metal concentrations in the crops and soils were analyzed to evaluate the long-term effects of the spilled waste on the soil and the potential human exposure through food chains. The results showed that the physical-chemical properties of the soils obviously changed due to the different farming styles used by each individual farmer. Leaching effects and plant extraction of metals from some soils were quite weak. Certain soils were still heavily polluted with As, Cd, Zn, Pb and Cu. The contamination levels were in the order of GYB>SZY>JTC showing that the clean-up treatment was effective. The maximum allowable concentration (MAC) levels for Chinese agricultural soils were still highly exceeded, particularly for As and Cd (followed by Zn, Pb and Cu), with mean concentrations of 709 and 7.6 mg kg(-1), respectively. These concentrations exceed the MAC levels by 24 times for As and 13 times for Cd at GYB. Generally, the edible leaves or stems of crops were more heavily contaminated than seeds or fruits. Ipomoea was the most severely contaminated crop. The concentrations of Cd and Pb were 3.30 and 76.9 mg kg(-1) in ipomoea leaves at GYB, which exceeded the maximum permit levels (0.5 mg kg(-1) for Cd and 9 mg kg(-1) for Pb) by 6.6 and 8.5 times, respectively. Taro (+skin) could accumulate high concentrations of Zn and Cd in the edible stem, and rice and capsicum had high Cd concentration in the edible parts. However, the toxic element concentrations in maize, sorghum, Adzuki bean, soybean and mung bean remained lower than the threshold levels. The bio-accumulation factors (BAFs) of crops were in the order: Cd>Zn>Cu>Pb>As. BAF was typically lower in the edible seeds or fruits than in stems and leaves. The accumulation effect strongly depends on the crop's physiological properties, the mobility, of the metals, and the availability of metals in soils but not entirely on the total element concentrations in the soils. Even so, the estimated daily intake amount of Cu, Zn, Cd, and Pb from the crops grown in the affected three sites and arsenic at SZY and GYB exceeded the RDA (Recommended dietary allowance) levels. Subsequently, the crops grown in Chenzhou Pb/Zn mine waste affected area might have a hazardous effect on the consumer's health. This area still needs effective measures to cure the As, Cd, Pb, Zn and Cu contamination.

Accidents, Occupational↗
PubMed2006

Radon concentration in houses over a closed Hungarian uranium mine.

High radon concentration (average 410 kBq m-3) has been measured in a tunnel of a uranium mine, located 15-55 m below the village of Kovágószolos, Hungary. The mine was closed in 1997; the artificial ventilation of the tunnel was then terminated and recultivation works begun. In this paper, a study has been made as to whether the tunnel has an influence on the radon concentration of surface dwellings over the mining tunnel. At different distances from the surface projection of the mining tunnel, radon concentration, the gamma dose, radon exhalation and radon concentration of soil gas were measured. The average radon concentration in the dwellings was 483 Bq m-3. Significantly higher radon concentrations (average 667 Bq m-3) were measured in houses within +/-150 m from the surface projection of the mining tunnel +50 m, compared with the houses further than the 300-m belt (average 291 Bq m-3). The average radon concentration of the soil gas was 88.8 kBq m-3, the average radon exhalation was 71.4 Bq m-2 s-1 and higher values were measured over the passage as well. Frequent fissures crossing the passage and running up to the surface and the high radon concentration generated in the passage (average 410 kBq m-3) may influence the radon concentration of the houses over the mining tunnel.

Environmental Monitoring↗
PubMed1990

Alveolitis caused by exposure to coal mine dusts: production of interleukin-1 and immunomodulation by bronchoalveolar leukocytes.

Two kinds of coal mine dust, low rank with high quartz (bituminous) and high rank with low quartz (anthracite), were assayed for ability to induce alveolitis and to stimulate interleukin-1 release from normal alveolar macrophages in vitro. Dust-elicited bronchoalveolar leukocytes were also assessed for their effects on macrophage-depleted splenocyte mitogenesis and their ability to produce interleukin-1. Quartz and titanium dioxide were used for comparison as toxic and inert dusts, respectively. Both coal mine dusts caused substantial release of interleukin-1 from normal alveolar macrophages in vitro and the levels were higher than those caused by quartz. Bituminous coal mine dust provoked acute but rapidly subsiding macrophage/neutrophil alveolitis which was greater than that provoked by titanium dioxide; anthracite caused less alveolitis than titanium dioxide and quartz caused large scale, persistent alveolitis. Whole bronchoalveolar leukocytes, including polymorphonuclear neutrophils, elicited by exposure to dust, were less inhibitory to lymphocyte mitogenesis than normal alveolar macrophages and bituminous coal mine dust-induced neutrophils were augmentary to lymphocyte mitogenesis; macrophages from inflamed lungs were, on the whole, inhibitory to lymphocyte mitogenesis. Alveolar macrophages from bituminous coal mine dust- or titanium dioxide-exposed lungs showed increased ability to release interleukin-1 on stimulation in vitro. These findings suggest that bronchoalveolar leukocytes elicited by coal mine dust could modulate immunity by means of interleukin-1 release and enhancement of lymphocyte proliferation.

Animals↗
PubMed2003

Preventing collisions involving surface mining equipment: a GPS-based approach.

PROBLEM: An average of three workers a year are killed in surface mining operations when a piece of haulage equipment collides with another smaller vehicle or a worker on foot. Another three workers are killed each year when haulage equipment backs over the edge of a dump point or stockpile. Devices to monitor the blind areas of mining equipment are needed to provide a warning to operators when a vehicle, person, or change in terrain is near the equipment. METHOD: A proximity warning system (PWS) based on the global positioning system (GPS) and peer-to-peer communication has been developed to prevent collisions between mining equipment, small vehicles, and stationary structures. RESULTS: A final system was demonstrated using one off-highway haul truck, three smaller vehicles, and various stationary structures at a surface mining operation. The system successfully displayed the location of nearby vehicles and stationary structures and provided visual and audible warnings to the equipment operator when they were within a preset distance. SUMMARY: Many surface mining operations already use GPS technology on their mobile equipment for tracking and dispatch. Our tests have shown that it is feasible to add proximity warning to these existing systems as a safety feature. Larger scale and long-term tests are needed to prove the technology adequately. IMPACT ON INDUSTRY: A PWSs that incorporates a combination of technologies could significantly reduce accidents that involve collisions or driving over an edge at surface mining operations.

Accidents, Traffic↗
PubMed1997

Environmental contamination and seasonal variation of metals in soils, plants and waters in the paddy fields around a Pb-Zn mine in Korea.

The objective of this study is to investigate the extent and degree of heavy metal contamination of paddy fields influenced by metalliferous mining activity. Paddy soils, rice plants and irrigation waters were sampled along six traverse lines in the vicinity of the mine and nearby control site. Soil samples were taken 30, 80 and 150 days after rice transplanting, to study seasonal variation of their chemical properties and heavy metal concentrations. Sampling of rice plants and irrigation waters was also undertaken with seasons. The analysis of the samples were carried out using ICP-AES for 25 elements including Cd, Cu, Pb and Zn. Physical and chemical properties of soils (pH, loss-on-ignition, cation exchange capacity and texture) and waters (pH, Eh and temperature) were also measured. The properties of soils were similar to the average Korean soils, with the exception of some samples taken in the vicinity of the mine. Concentrations of Cd, Cu, Pb and Zn in paddy soils, rice plants and irrigation waters sampled in the immediate vicinity of the mine were relatively high due to the seepage of metals from mining dump sites. Although there was variation between sampling sites, soil pH values under reducing conditions were on average higher than those under oxidising conditions. Relatively low content of organic matter and low cation exchange capacity of soils were found at 80 days after rice transplanting (P < 0.05). No seasonal variations in metal concentrations were found in paddy soils throughout the period of the rice growing, in which soils ranged from flooded reducing conditions through most of the growing season to drained oxidising conditions before and at harvest. Relatively high metal concentrations were found in the rice stalks and leaves under oxidising conditions. The sequential extraction analysis of selected soil samples confirmed that high proportions of exchangeable fractions of the metals were found under oxidising conditions. It was shown that Cd and Zn concentrations in rice leaves and stalks and rice grain increased with increasing metal concentrations in paddy soils to a greater extent than for Cu and Pb. This difference in uptake is in agreement with the greater proportions of Cd and Zn, compared with Cu and Pb, in the exchangeable soil fraction extracted with MgCl2. Average daily intake from locally grown rice by the residents was estimated to be 121 micrograms Cd and 126 micrograms Pb. Thus, long-term metal exposure by regular consumption of the rice poses potential health problems to residents in the vicinity of the mine, although no adverse health effects have as yet been observed.

Cadmium↗
PubMed2003

Untreated abandoned mercury mining works in a scenic area of Asturias (Spain).

Mercury mining was a large and thriving industry during the last century in Asturias (NW Spain). At Brañalamosa, mining activity introduced significant quantities of wastes in spoil heaps located close to the mining operations. In these mining wastes, in addition to mercury, high concentrations of other potentially dangerous elements like As have been found. As a consequence, pollution and dereliction of the local environment occurred. This paper focuses on the environmental impact of these old mining operations and describes a preliminary assessment of the extent of contamination. This includes analytical data from systematic sampling of soils, stream sediments, wastes from spoil heaps, water and herbaceous plants in areas affected by mining activities. The potential risk that spoil materials imply for human health and the environment is documented on the basis of the application of EPA Risk Assessment methodology.

Arsenic↗