State of Contamination of the Waters in the Guadiamar Valley Five Years after the AznalcÓllar Spill

In April 1998, the Aznalcóllar mine tailings dam spilled 2 hm³ of slurry and 4 hm³ of acid waters into the Agrio River (affluent of the Guadiamar River). The pollutants reached the proximity of the Doñana National Park, 60 km downstream. The state of contamination of groundwaters and surface waters, from several samplings made subsequent to the spill, is described. Although the Guadiamar valley groundwaters remain contaminated, this situation cannot be attributed to the mining spill, but to the long history of pollution from mining activity at Aznalcóllar. Three zones can be distinguished: the most polluted zone, with pH values close to 4 and very high concentrations of metals (up to 18 mg/l of Al and 7 mg/l of Mn) and sulfates (up to 1263 mg/l); a second zone where pH values are higher (close to neutral) and, as a result, the concentration of metals is significantly lower; and a third zone, with pH exceeding 7, in which the concentration of metals has already fallen to normal levels but sulfate concentrations remain high (above 500 mg/l). The waters of the Agrio River present characteristics similar to those of the most-polluted groundwaters; on mixing with the waters of the Guadiamar River they are neutralized, precipitating firstly Al and then the rest of the metals. These metals remain deposited on the river-bed, where they are readily remobilized in later spates. Analysis of changes in groundwater quality shows a trend toward a lower content of Zn and the other metals in most wells.     

Occurrence of acidic groundwater in precambrian crystalline bedrock aquifers,Southwestern Sweden

The pH and alkalinity of groundwater from 7651 wells drilled in the Precambrian crystalline bedrock of southwestern Sweden has been evaluated. The wells are generally less than 100 m deep. Analytical results were collected from different laboratories and authorities in the region. In areas with thin soil cover or coarse-grained deposits overlying the bedrock, alkalinity is normally less than 100 mg HCO₃ L^?1. Below the marine limit, where clayey sediments predominate, alkalinity sometimes even exceeds 200 mg HCO₃ L^?1. When comparing pH and alkalinity of groundwaters from Quaternary deposits with bedrock groundwaters, the latter always have higher pH and alkalinity values. The most acidic bedrock groundwaters are found in small areas close to the city of Göteborg due to additional factors of high acid loadings, high groundwater discharge and thin soil layers. A study of data from 1949 to 1985 in the province of Värmland suggests that no regional acidification of importance is in progress. However, results from public water supplies support the hypothesis that the groundwaters which are most sensitive to acidification are those where discharge from wells in small bedrock aquifers induces rapid groundwater recharge of acidic surficial water.     

Background concentration ranges of heavy metals in Swedish groundwaters from crystalline rocks: A review

Concentration levels of heavy metals (Cr, Cu, Zn, Cd, and Pb) in groundwaters, primarily from igneous crystalline bedrock, are summarized. The groundwaters were sampled from 126 stations in Sweden during 1985–87 (1–6 times per year). The observed groundwater concentrations are generally at least qualitatively related to concentration levels in the bedrock as well as to pH of the water. Background concentration ranges for unpolluted groundwaters from the present bedrock environment are suggested.     

Groundwater Contribution of Metals from an Abandoned Mine to The North Fork of The American Fork River, Utah

Surface water discharge measurements and metals concentrations in the North Fork of the American Fork River, Utah, its tributaries, and the groundwater in the vicinity of the Pacific Mine were used to evaluate the impact of groundwater on loading rates of metals and As to the river. Fish in the river contain As, Cd, and Pb at concentrations that are hazardous to human health if consumed. The results suggest that dissolved As, Cd, Cu, Fe, Mn, Pb, and Zn enter the river when it is a gaining stream. However, the suspended metals load is significantly greater than the dissolved load, and generally decreases through the reach of river adjacent to the mine site. Cadmium and Mn travel as dissolved species while Cu, Fe, Pb, and Zn travel as suspended solids. Arsenic seems to travel both with the suspended solids and in the dissolved state. The geochemical modeling program PHREEQC and a diffuse double layer surface complexation model were used to investigate the chemical controls on metals mobility and attenuation in the surface and groundwaters at the site. Based on the PHREEQC results, the most important process in these waters is the precipitation of ferrihydrite, also referred to as hydrous ferric oxide (HFO). Copper, Pb, most importantly Zn, and to a lesser degree As sorb to HFO.     

Chromium speciation in natural waters draining contaminated land,Glasgow, U.K.

Historically, solid waste from chromite ore processing has been disposed of at a number of sites in Glasgow, Scotland. Leachate from these sites has been implicated as a source of chromium (Cr) contamination to both groundwaters and stream waters in the south east area of the city. In this study, chromium speciation has been determined in ground-, stream-, river- and pore waters, to assess the extent of contamination and the associated risk. The speciation of chromium is important, as the trivalent species of chromium (Cr(III)) is an essential form of the element, while hexavalent chromium (Cr(VI)) is a known carcinogen to humans via inhalation. Concentrations of total chromium have also been determined in sediments from the River Clyde, to assess the significance of local concentrations relative to those elsewhere in the catchment. High concentrations of Cr(VI) were found in groundwaters and streamwaters in the area immediately surrounding the contaminated sites, and high concentrations of chromium were also found in River Clyde sediments downstream of these sites. However, these concentrations rapidly decrease away from the chromium-contaminated south eastern side of the city. Data from porewaters suggest that some reduction of Cr(VI) occurs naturally in the sediments, indicating that the risk posed by high concentrations of Cr(VI) should be decreased over the longer term.     

铅锌银尾矿区土壤微生物活性及其群落功能多样性研究

通过对浙江省天台铅锌银尾矿区土壤微生物活性指标以及微生物群落功能多样性研究 ,结果表明 ,尾矿污染区土壤几种重金属含量比非矿区土壤有明显的增加。尾矿区土壤微生物特征发生了显著的变化 ,微生物生物量和可培养细菌数量显著降低 ,但土壤基础呼吸和微生物代谢商 (qCO2 )值却明显升高。Bi olog测试结果显示 ,随着重金属污染程度的加剧其土壤微生物群落结构发生了相应变化 ,尾矿区土壤微生物群落代谢剖面 (AWCD)及群落丰富度、多样性指数均显著低于非矿区土壤 ,且供试土壤间均达极显著水平差异 (p <0 .0 1) ,表明尾矿区重金属污染引起了土壤微生物群落功能多样性的下降 ,减少了能利用有关碳源底物的微生物数量、降低了微生物对单一碳源底物的利用能力     

Solute Transport at Low Flow in an Acid Stream in Appalachian Ohio

The spatial variability in chemical composition of water and sediments along Snow Fork, a stream draining 70 km² of southeastern Ohio, was investigated under low-flow conditions. The stream is affected by acid mine drainage (AMD) beginning atEssex Mine, an abandoned mine opening, and extending 23 km downstream to the confluence with Monday Creek. Volumetric discharge and changes in stream water and sediment metalconcentrations were examined to identify chemical interactionsand processes controlling the transport and fate of metalcontaminants. The stream loses water to the groundwater system insome sections. The water loss probably occurs through fracturesconnecting the stream to underlying underground coal mines. Massbalance (loading) and mineral saturation index calculations wereused to identify metal sources and sinks. Dissolved metal loadingincreases downstream along the length of Snow Fork, despite theprecipitation of metals as hydroxides in the streambed,indicating multiple groundwater sources of AMD along the flowpath. Relatively high dissolved metal concentrations and lowsediment metal concentrations occur where the pH is low,indicating that local sediment-water interaction dominates masstransfer between sediments and water. Calculated mineralsaturation indexes indicate that aluminum and iron hydroxidesprecipitate in some stream segments and dissolve in others. X-raydiffractograms of sediments show two distinct mineral groups.Amorphous or weakly crystalline minerals dominate one group foundnear the stream headwaters near the underground mine. Crystallinemineral phases dominate the sediments downstream. Thesediffractograms contain the primary peaks for quartz, kaoliniteand illite all of which constitute the local sandstones, shalesor underclay. Peaks of amorphous phases of iron and manganese,if present, are obscured. The implications of these findings arethat the transport of metals in sediments may be as important asdissolved metal transport in estimating the overall stream load,particularly if downstream sources of AMD may remobilize metalsfrom soluble precipitates.     

Heavy metal accumulation in the plinthic horizon of a ferric gleysol

The heavy metal status of an industrial production site (about 40000 m²) in the Lahn valley (middle Hesse) was investigated. In the upper soil layer (0 - 1 m) Fe, Pb-, and Zn-contents were determined in 42 sampling points. High heavy metal contents (up to 45% Fe, 4% Zn, and 2,5% Pb) were discovered in certain topsoil samples. The geostatistical analysis suggested that a spatially limited accumulation of Pb and Zn together with iron exists in the southern and western part of the area, where a continual bog iron layer in the oxidized horizon of the local gleysols had been detected. The profile distribution of Fe, Pb, and Zn also revealed a close coexistency of these elements together with SO₄ and other soluble salts in a distinct horizon. On the whole, no evidence was found for an industrial origin of the observed heavy metal accumulations. Since the base of the upper groundwater floor is formed by highly pyritic black shales, which obviously also contain Pb/Zn-ores, a geogenic heavy metal enrichment is proposed. The intense weathering of the black shales charges the groundwater with iron, heavy metals and sulfates. This salt load is deposited in the groundwaters capillary fringe forming a bog iron pan rich in heavy metals and soluble salts.     

Reactive solute transport in acidic streams

Spatial and temporal profiles of pH and concentrations of toxic metals in streams affected by acid mine drainage are the result of the interplay of physical and biogeochemical processes. This paper describes a reactive solute transport model that provides a physically and thermodynamically quantitative interpretation of these profiles. The model combines a transport module that includes advection-dispersion and transient storage with a geochemical speciation module based on MINTEQA2. input to the model includes stream hydrologic properties derived from tracer-dilution experiments, headwater and lateral inflow concentrations analyzed in field samples, and a thermodynamic database. Simulations reproduced the general features of steady-state patterns of observed pli and concentrations of aluminum and sulfate in St. Kevin Gulch, an acid mine drainage stream near Leadville, Colorado. These patterns were altered temporarily by injection of sodium carbonate into the stream. A transient simulation reproduced the observed effects of the base injection.     

Impact of Past Mining Activity on the Quality of Water and Soil in the High Moulouya Valley (Morocco)

Physical and chemical properties and the total content of potentially toxic metals (PTMs) in waters and soils were studied from the High Moulouya Valley (Morocco) in order to assess the impact of the past mining activity on their quality and to lay the foundations of a potential reclamation of the area. Surface water and groundwater samples were collected from the Moulouya River and mine pit lakes; tailings and soils were sampled inside and outside the mine sites of Zeïda, Mibladen, and Aouli. Both waters and soils were alkaline, due to the limestone environment, and contained Pb and Zn as main metallic contaminants. Pollution levels were highest within the Mibladen mining site, and soil pollution was mainly restricted to the areas where activities of metal concentration were carried out. Tailings and soils from these areas besides Pb and Zn were also polluted by As, Cd, and Cu showing clay fraction highly enriched in metal contaminants. At the time of study, all soils and wastes (including the highly polluted tailings) were in advanced stage of spontaneous herbaceous and arbustive revegetation. It is concluded that, in the High Moulouya Valley, the processes governing PTM transfer from the element-rich sites to the nearby environment are strongly influenced by pH, carbonate content, and semi-arid climate reducing metal mobility from the mining waste impoundments by dissolution. The transfer by wind and water erosion of metal-enriched fine waste particles is likely to be a much more important vector for metal dispersion. In this perspective, among a range of land remediation techniques available, natural and oriented revegetation could represent a low-cost and possible permanent solution.     

Environmental Impact on an Arctic Soil–Plant System Resulting from Metals Released from Coal Mine Waste in Svalbard (78° N)

Impact of acid mine drainage (AMD) from a coal mine waste rock pile deposited within a permafrost-affected Arctic ecosystem was investigated near Longyearbyen (Svalbard, 78° N). Analyses included metal concentrations (Al, Fe, Mn, Zn, Ni, Cr, As and Pb) in runoff, soil and plants. It was observed that impacts of AMD, such as plant degradation, were similar to impacts reported from non-arctic ecosystems. It was found that bio-available metal concentrations in soil samples were not useful in assessing potential plant toxicity, as metals were not accumulated in the most impacted area due to low soil pH (pH?<?4). Native graminoid plants in the high impacted area showed accumulation of all the investigated elements. Al, Mn and As were found at phyto-toxic concentrations. Metal uptake in two native graminoid plants was studied in the laboratory. Positive correlations were noted between metal concentrations and plant uptake for all metals investigated, except Fe. High Fe concentrations found in plant samples in the impacted area are considered a result of Fe-oxide precipitation (plaque) on leaves during the spring flush when runoff covers the plants. We conclude that the weathering products Al, Mn and Fe induce the largest negative impact on vegetation in the area, and that a major fraction of the annual uptake of metals occurs during spring flushes. During these flushes, metals produced from weathering processes throughout the winter are released in high concentrations, coinciding with low pH values, low infiltration rates due to permafrost and the start of the plant growth season.     

Methods for treating acid groundwater results and evaluation of long-term tests

Acid groundwater can corrode plumbing systems and solubilize metals in the soil or in the plumbing systems. Since the soluble forms of some metals are toxic, concerns regarding the effects of groundwater acidification on human health have been raised. A number of new methods for treating acidified groundwater have been developed and tested during the last decade. In addition conventional filter devices have been tested and evaluated. Seven methods of in situ alkalization, i.e. treatment of the soil around the well with an alkalizer, have been tested for 1–8 years. These methods involve the application of limestone or slaked lime in the recharge area of the well or in/near the well. Target values set for the tests were: pH>6,5 and alkalinity >60 mg/l. Almost all of these methods have led to improvements in water quality, but in some cases target values were not reached. Most of the treatments have resulted in significant reductions in iron and aluminium contents in drinking water. Eight types of more conventional devices for processing acidified well water have been tested for a couple of years. These de-acidification filters are installed indoors or in some cases inside the well. The majority of them performed well, providing acceptable values of pH and alkalinity under normal water flows. However,after periods of more intense water flushing, some of the filters showed a decreased capacity to neutralize the water. Inexpensive types of equipment, e.g. some of the filters placed inside the well, performed just as well as the more expensive types.     

凤县银洞梁铅锌矿区土壤重金属污染线性与非线性方法结合研究

选取凤县典型铅锌矿区银洞梁8个监测点的土壤样品,在实验室应用空气-乙炔火焰原子吸收分光光度法进行Cu、Zn、Pb、Cd、Cr五种重金属全量测定。应用密切值法对8个监测点的土壤重金属污染程度进行综合评价,结果表明该矿区土壤已受不同程度重金属污染,其中两个监测点达到了严重污染程度。考察了密切值法的综合评价与单因子污染指数法评价两结果之间的关系,结果表明具有较强迁移能力的矿区主要污染物Zn能够较好的表征矿区土壤重金属的综合污染状况。     

Zn and Pb release of sphalerite (ZnS)-bearing mine waste tailings

Background, aim, and scope  Contaminated mine drainage water has become a major hydrogeological and geochemical problem. Release of soluble metal contaminants and acidity from mining sites can pose serious chemical risks to surface and groundwater in the surrounding environment, and it is an important socio-economic factor addressed by working groups like SUITMA Morel and Heinrich (J Soils Sediments 8:206–207, 2008). The release of Zn and Pb from sulfide-bearing flotation residues of a small scale mine in Western Germany is investigated with focus on metal transfer to soil solution. Total contents of the soil material as well as soil water sampled with suction cups were analyzed. The influence of pH on leaching behavior was investigated with pH_stat tests. Isotopic analyses helped assessing seepage water velocity. The aim of this study was the assessment of the environmental behavior of zinc and lead caused by the weathering of sulfide-bearing mine tailings. Especially, we address in this paper the dissolution of sphalerite (ZnS) in contrast to the well-known dissolution processes of pyrite (FeS₂). Materials and methods  Total metal contents of the soil samples were analyzed by energy-dispersive X-ray fluorescence spectroscopy, total C concentration was measured using a CHNS elemental analyzer. X-ray diffraction (XRD) spectra were recorded from powdered soil samples. Soil water was sampled in nylon suction cups. Electrical conductivity (EC), pH, and temperature of the soil water samples were measured in the field immediately after sampling. Major anions (F, Cl, NO₂, NO₃, SO₄) were analyzed by ion chromatography, major cations (Ca, Na, K, Li) were analyzed by flame photometry, heavy metals (Zn, Pb, Fe, Mn, and Mg) by flame atomic absorption spectrometry. Tritium was analyzed by liquid scintillation counting (LSC), ¹⁸O and ²H were analyzed by isotope ratio mass spectrometry (IRMS). pH_stat tests were performed at four different pH values between 2 and 5. Results  Total Zn contents of the soil samples averaged 10 g kg⁻¹, Pb contents averaged 2.5 g kg⁻¹, Fe 22 g kg⁻¹, S 8.0 g kg⁻¹, and total carbon 4.0 g kg⁻¹. Below 2-m depth, soil samples had neutral pH values. Toward the surface, pH decreased down to pH 5.4 in P1 and P3, and to pH 5.9 in core P2, respectively. Dissolved contents of major ions (Mg, Ca, K, SO₄, and HCO₃) in the soil solution increased with depth. Metal concentrations (Fe, Mn, Zn) decreased with depth. The solution pH was neutral to slightly alkaline in samples below 2 m and slightly acidic (pH 6) at 1 m depth. Tritium values are around 7 TU and correspond to modern rain, i.e., after 1975. Stable isotope values plot on the global meteoric water line. The pH_stat tests provide two kinds of information, the acid neutralization capacity after 24 h (ANC24) and the release of metals depending on pH. The ANC24 increases linearly with decreasing pH from about 60 mmol(eq) kg⁻¹ at pH 5 to about 460 mmol(eq) kg⁻¹ at pH 2. Zn and Fe release show a strong increase with decreasing pH to 126 and 142 mmol(eq) kg⁻¹, respectively. Pb release increases at pH <4 and Mn release at pH <5, both to about 10 mmol(eq) kg⁻¹. Discussion  With an average of 10 g kg⁻¹, this field site is highly enriched in Zn. In the oxidized topsoil, Zn concentrations are significantly lower than in the anoxic subsoil. The distribution pattern of total Zn contents and soil pH values indicate that the topsoil, which is prone to oxidation and acidification, is already depleted in Zn. Only in soil core P2, Zn (and Fe) contents in the topsoil were higher than in the subsoil. Oxidation of the sulfidic material leads to redistribution into mobilizable species. High soil water concentrations (10 to 15 mg L⁻¹) can be found at acidic pH. The dominant Zn species in the soil solution is Zn²⁺. At neutral pH, Zn concentrations are below 0.001 mg L⁻¹. During the soil passage, the contaminated seepage water enters the anoxic subsoil with pH buffering carbonates. Results indicate that Zn is immobilized there. However, when the acid neutralization capacity is exhausted, a breakthrough of dissolved Zn to the groundwater has to be expected. Lead averages 2.5 g kg⁻¹ inside the flotation dump. In contrast to Zn, the first centimeters of the oxidized topsoil with high TOC contents show higher Pb contents than the anoxic subsoil. About 80% of the cation exchange capacity in the topsoil is occupied by Pb. In contrast to Zn, Pb is not abundant as aqueous species at slightly acidic pH. Values lower than pH 4 are necessary to mobilize Pb in higher amounts, as pH_stat experiments confirm. Hence, Pb is not expected to be leached out until the buffer capacity of the soil is exhausted. Conclusions  The environmental fate and behavior of Zn and Pb in the flotation dump is strongly depending on pH and redox conditions. Oxidation of sphalerite leads to a transfer of Zn from immobile to easily mobilizable species. Sulfide oxidation leads to an acidification of the topsoil where the buffer capacity is already exhausted due to the leaching of carbonates. At acidic pH, Zn is transferred to the aqueous phase and leached to the subsoil where soil pH is neutral. Electron supply and the buffer capacity of the material are found to be the main factors controlling the mobility of Zn. In contrast, the transfer of comparable amounts of Pb to the aqueous phase requires pH values <4. Since Pb is enriched in the topsoil, not leaching to the groundwater, but direct uptake (e.g., children, animals) and uptake by plants is the highest environmental risk. If the acidification of the soil proceeds with the same rate as in the last 40 years, it will reach the bottom of the tailing in about 200 years and a breakthrough of metals to the groundwater has to be expected. Recommendations and perspectives  The behavior of the different metals and their environmental impact depends on the different metal properties as well as on external conditions, e.g. pH, redox conditions, buffer capacity, and groundwater recharge. To assess the future release of metals from a flotation dump it is crucial to determine the main processes leading to acidification, the buffer capacity, and heavy metal binding forms. The release of heavy metals to the groundwater could be prevented by liming or other buffering techniques de Andrade et al. (J Soils Sediments 8:123–129, 2008). Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Hydrochemical Impacts of Limestone Rock Mining

Hydrochemical impacts of shallow rock industrial-scale mining activities close to sensitive constructed and natural wetlands were investigated. The shallow surficial groundwater and surface water in the Everglades Agricultural Area (EAA) were characterized. The chemical composition of sulfate and chloride in groundwater increased with depth. The average concentration of chloride averaged 182 mg?L^?1 at 6 m deep and increased gradually to 1,010 mg?L^?1 at 15 m deep, 1,550 mg?L^?1 at 30 m deep to reach 7,800 mg?L^?1 at 60 m deep. Comparatively, the surface water chemical composition in the surrounding areas showed much lower cationic and anionic charge. The specific conductivity and total dissolved solids of surface water in canals (close to the mining operations) are <900 ??S?cm^?1 and <600 mg?L^?1, respectively, which should be compared to groundwater quality in wells from the EAA area (>2,000 ??S?cm^?1 and >1,000 mg?L^?1, respectively). A steady-state groundwater fluid flow and transient solute transport modeling exercise was conducted to estimate surface/groundwater interactions. The modeled solute in surface water was transported downgradient through groundwaters, migrated approximately 30 m from the source area (after 5 years of operation), and needed more than 116 years to dissipate. An upward transport was also identified whereby chloride and sulfate, naturally present in deeper groundwaters, migrated approximately 200 m (after 1 year of mining) into the pristine shallower aquifer and reached the surface water with a concentration equaling 80% of that in the rock mining pit.     

Aspects of trace metal contamination in the coastal rivers of Israel

Nine trace elements of biological concern: Cr, Co, Cu, Cd, Ni, Pb, Hg, Zn and Ag were investigated in the sediments of the most important coastal steams in Israel. All of these are subjected to some degree of domestic and/or industrial sewage input with the consequent liability of contamination by trace metals. The Ayyalon, Gadura, Qishon and locally the Hadera rivers contain sediments exhibiting severe pollution effects. There is a danger of infiltration through the soils into the groundwaters as well as exposing nearshore fauna to sediments contaminated by possibly toxic trace metals. The other rivers bear smaller levels of trace metals; however, an increase of the Pb and the Zn levels occurs near major highways.     

Ecogeochemical Investigation: Stream Water Quality as an Indicator of Pollution in the Border Areas of Finland, Norway and Russia

The Geological Surveys of Finland and Norway, and the Central Kola Expedition, Russia, carried out an environmental geochemical mapping project, including investigation of stream water quality. The project was carried out in 1992–1993 in the border areas of Finland, Norway and Russia, covering an area of 12 000 km², to determine the impacts of smelting industries at Nikel and Zapoljarnij. Stream water was one of eight different indicators providing an estimation of the degree and distribution of contamination in the study area. Contamination of surface water was assessed by analyses of 44 samples, 41 variables were measured on each sample. Indicators of human activities in surface waters are NO₃, K, electrical conductivity (EC), SO₄, Na, Cl and acidification indicated by alkalinity and pH. On the coast Na and Cl contents are also affected by marine salts. The results show considerably higher contents of K, Ca, Mg, SO₄, Na, heavy metals and EC in the samples close to Nikel and Zapoljarnij smelters than those sites more distant from the polluting sources. Especially chemical effects of high emissions of Ni, Cu and SO₂ on stream water quality from Nikel and Zapoljarnij smelters are clearly seen near the sources of emissions.     

Heavy metal content and toxicity of mine and quarry soils

Purpose

Soils formed in metallic mines and serpentinite quarries, among other unfavourable features, have high levels of heavy metals. They can release into the environment causing surface and subsurface water contamination, uptake by plants, their accumulation in the food chain and adverse effects on living organisms. In this work, we studied the magnitude of the soils’ toxic effects not only on spontaneous plants but also on two species with phytoremediation potential.

Materials and methods

Several soils from two different exploitations were selected: a lead and zinc mine and a serpentinite quarry. Soils were characterized, and the pseudo-total and extractable contents of Co, Cr and Ni in soils from a serpentinite quarry were determined. The Cd, Pb and Zn pseudo-total and extractable contents were determined in soils developed in the Pb/Zn abandoned mine. Using a biotest, the chronic toxicity of the soil samples on higher plants was determined. Festuca ovina L., Cytisus scoparius (L.) Link., Sinapis alba L. and Brassica juncea L. were selected, the first two because they are spontaneous plants in the study areas and the last two because they have heavy metal phytoremediation potential.

Results and discussion

Pseudo-total contents of Co, Cr and Ni in the serpentinite quarry soils and of Zn, Pb and Cd in the Zn/Pb mine soils exceed generic reference levels. CaCl₂ is the reactant that extracts the highest proportion of Co, Cr and Ni in the quarry soils and EDTA the largest proportion of Pb Zn and Cd content in the mine soils. The germination index values based on seed germination and root elongation bioassays revealed increasing plant sensitivity to the mine soils in the following order: B. juncea?<?S. alba?<?F. ovina?<?C. scoparius. The wide range of GI values indicates that the response of test plants to soil heavy metals depended on their concentrations and soil characteristics, especially pH and organic matter content.

Conclusions

The pollution index indicates severe Cd, Pb and Zn contamination in the mine soils, as well as high Cr and Ni and moderate Co contamination in the serpentinite quarry soils. The performed biotests were suitable for identifying toxic soils and showed that the studied soils are toxic to the spontaneous plants, more to C. scoparius than to F. ovina. They also indicate that the mine soils are more toxic than the quarry soils for both species.

     

Groundwater Pollution by Heavy Metals in Historical Mining Area of Lavrio,Attica, Greece

This article deals with the impacts of past mining activities andinefficient water resources management on groundwater quality inthe Lavrio area. Thirty-three water samples were collectedduring March 1998 and were analyzed for major ions (Ca, Mg, Na,K, HCO₃, Cl, NO₃, SO₄, PO₄), trace elements(Fe, Pb, Ni, Zn, Mn, Cu, Cr, Cd) and water parameters (Temperature,pH, conductivity, hardness and SiO₂). High concentrationsof heavy metals (lead, cadmium, zinc, nickel) are recorded ingroundwater samples in the Lavrio area. The highestconcentrations are recorded in the unconfined aquifer (alluvialdeposits and schists), due to mining activities. Qualitydeterioration of groundwater is also decumented and attributedto seawater intrusion and nitrate pollution of agriculturalorigin. The data were subjected to simple correlation analysisand R-mode factor analysis in order to examine the relationshipsbetween the parameters. There is a relationship between theelements participating in the sulfide (Pb, Zn, Cu, Cd) andiron-manganese mineralization and a strong relationship betweenNi–Cr. In the factor analysis a four-factor model is suggested,which can explain 72.5% of the total variance. The contributionof each factor at every site is also computed and maps showingthe geographical distribution are illustrated. The areas withhigh concentrations of heavy metals are defined from these maps.     

Assessment of soil contamination by potentially toxic elements in the aljustrel mining area in order to implement soil reclamation strategies

Land pollution due to past mining activities is a major environmental issue in many European countries. The Aljustrel mine (SW Portugal), located in the western sector of the Iberian Pyrite Belt (IBP) presents a negative visual and environmental impact as a consequence of the mining activity that has developed since the Roman era. Its impacts are also a restraint on the life quality of the population. The exposure of pyrite and other sulphides to air are responsible for the pollution observed in soils, surface water and stream sediments. This paper investigates the pollution load of potential toxic elements in soil samples collected around the Aljustrel mining area. The aim is to assess the levels of soil contamination with respect to average concentrations of toxic elements in the region and to understand the partitioning and availability of pollutants in the area. The results showed severe soil contamination (mainly As, Cd, Cu, Pb and Zn). The concentrations of As (up to 3936 mg kg⁻¹) and certain heavy metals (up to 5414 mg kg⁻¹ Cu, 61·6 mg kg⁻¹ Cd, 20 000 mg kg⁻¹ Pb and 20 000 mg kg⁻¹ Zn) are two orders of magnitude above the regional South Portuguese Zone (SPZ) background values. The median concentrations of As, Cd, Cu, Pb and Zn exceed the values established for world soils, the European Union, Portugal and Andalusia. The results suggest that the distribution patterns of Co, Cr and Ni element concentrations in the Aljustrel area are primarily influenced by the lithology and geochemistry nature of bedrock. The soil background of this geological domain is characterized by relatively high heavy metal contents, essentially derived from the parent rocks. Copyright © 2010 John Wiley & Sons, Ltd.