Sb Mine Research Articles

Speciation of antimony and arsenic in the soils and plants in an old antimony mine

The speciation changes of antimony (Sb) in soil–plant system are largely unknown as compared with those of arsenic (As). In this study, indigenous plants and associated soils were sampled at the Xikuangshan Sb mine (XKS), China. The Sb in the soils (441–1472mg/kg) were far greater than As (32–354mg/kg), and the Sb and As availabilities in the soils, were 5.5% and 3.9% in average, respectively. HPLC-ICP-MS revealed the presence of four species of Sb in the soils and plants, including SbIII, SbV, TMSb and UnkSb (unknown). The use of XANES revealed that the UnkSb consisted of inorganic Sb in the form of SbV. Inorganic Sb were prevalent in the soil and plant samples at the eight sites, whereas TMSb was observed in only a few of the rhizosphere soils, and, in plants at a few of the sites, primarily in the leaves and to a lesser extent in the stems. Arsenic was detected in the soils primarily as inorganic forms, while, DMA was detected in high proportions in all of the plant tissues at all of the sites. The methylation of Sb was far less than that of As in the indigenous plants at XKS. The results suggest that As and Sb differ in transformation characteristics in the soil–plant system in XKS.

Persisting impact of historical mining activity to metal (Pb, Zn, Cd, Tl, Hg) and metalloid (As, Sb) enrichment in sediments of the Gardon River, Southern France

In this study, we assessed past and present influence of ancient mining activity on metal(loid) enrichment in sediments of a former mining watershed (Gardon River, SE France), that is now industrialized and urbanized. A sedimentary archive and current sediments were characterized combining geochemical analyses, zinc isotopic analyses and sequential extractions. The archive was used to establish local geochemical background and recorded (i) increasing enrichment factors (EFs) for Pb, Zn, Cd, Tl, Hg, As and Sb throughout the industrial era, (ii) a contamination peak in 1976 attributed to a tailings dam failure, and (iii) current levels in 2002 and 2011 similar to those of 1969, except for Sb and Hg, reflecting a persisting contamination pattern. Inter-element relationships and spatial distribution of EF values of current sediments throughout the watershed suggested that both ancient and current contamination had a common origin for Pb, Zn, Cd, Tl and As related to the exploitation of Pb/Zn mineralization while old Sb mines and coal extraction area were the main sources for Sb and Hg respectively. This prevailing mining origin was reflected for Zn by a relatively uniform isotopic composition at δ66Zn=0.23±0.03‰, although slight decrease from 0.23‰ to 0.18‰ was recorded from upstream to downstream sites along the river course in relation with the contribution of the lighter δ66Zn signature (~0.08‰) of acid mine drainage impacted tributaries. Results from sequential extractions revealed that the potential mobility of the studied metal(loid)s varied in the order Sb<Tl≈As<Zn<Pb<Cd, with an increase of the mobile pool for Cd, Pb, Zn and to a lesser extent for As and Tl associated to increased enrichment. Altogether, these results tend to demonstrate that ancient mining activity still contributes to metal enrichment in the sediments of the Gardon River and that some of these metals may be mobilized toward the water compartment.

Removal of antimony (Sb(V)) from Sb mine drainage: Biological sulfate reduction and sulfide oxidation–precipitation

Antimony (Sb(V)) in Sb mine drainage has adverse effects on the receiving water environments. This study for the first time demonstrated the feasibility of using sulfate-reducing bacteria (SRB) to convert sulfate ions in SMD into sulfides that reduce Sb(V) to Sb(III) and to form complex with Sb(III) as precipitate. The principal compound in the precipitate was stibnite (Sb2S3) at pH 7 and pH 9. The Sb(V) removal mechanism is sulfate-reduction and sulfide oxidization-precipitation, different from the conventional SRB-precipitation processes for heavy metals. The Sb(V)/sulfate ratio is noted an essential parameter affecting the Sb removal efficiency from SMD.

Identification of Antimony- and Arsenic-Oxidizing Bacteria Associated with Antimony Mine Tailing

Antimony (Sb) is a naturally occurring toxic element commonly associated with arsenic (As) in the environment and both elements have similar chemistry and toxicity. Increasing numbers of studies have focused on microbial As transformations, while microbial Sb interactions are still not well understood. To gain insight into microbial roles in the geochemical cycling of Sb and As, soils from Sb mine tailing were examined for the presence of Sb- and As-oxidizing bacteria. After aerobic enrichment culturing with AsIII (10 mM) or SbIII (100 μM), pure cultures of Pseudomonas- and Stenotrophomonas-related isolates with SbIII oxidation activities and a Sinorhizobium-related isolate capable of AsIII oxidation were obtained. The AsIII-oxidizing Sinorhizobium isolate possessed the aerobic arsenite oxidase gene (aioA), the expression of which was induced in the presence of AsIII or SbIII. However, no SbIII oxidation activity was detected from the Sinorhizobium-related isolate, suggesting the involvement of different mechanisms for Sb and As oxidation. These results demonstrate that indigenous microorganisms associated with Sb mine soils are capable of Sb and As oxidation, and potentially contribute to the speciation and mobility of Sb and As in situ.

Multivariate and spatial analysis of heavy metal sources and variations in a large old antimony mine, China

Purpose Contaminations by multiple heavy metals in antimony (Sb) mines produce serious environmental and health problems; however, the spatial variations in various heavy metals relative to the sources and transportation of Sb have rarely been documented. To resolve this problem, we conducted a survey in an old Sb mine in Xikuangshan (XKS), China, to investigate the similarities and differences among the sources and diffusion characteristics of the heavy metals that were present as well as the factors influencing these patterns.

Antimony (Sb) and Arsenic (As) in Sb Mining Impacted Paddy Soil from Xikuangshan, China: Differences in Mechanisms Controlling Soil Sequestration and Uptake in Rice

Foods produced on soils impacted by antimony (Sb) mining activities are a potential health risk due to plant uptake of the contaminant metalloids (Sb) and arsenic (As). Here we report for the first time the chemical speciation of Sb in soil and porewater of flooded paddy soil, impacted by active Sb mining, and its effect on uptake and speciation in rice plants (Oryza sativa L. cv Jiahua). Results are compared with behavior and uptake of As. Pot experiments were conducted under controlled conditions in a climate chamber over a period of 50 days. In pots without rice plants, flooding increased both the concentration of dissolved Sb (up to ca. 2000 μg L(-1)) and As (up to ca. 1500 μg L(-1)). When rice was present, Fe plaque developing on rice roots acted as a scavenger for both As and Sb, whereby the concentration of As, but not Sb, in porewater decreased substantially. Dissolved Sb in porewater, which occurred mainly as Sb(V), correlated with Ca, indicating a solubility governed by Ca antimonate. No significant differences in bioaccumulation factor and translocation factor between Sb and As were observed. Greater relative concentration of Sb(V) was found in rice shoots compared to rice root and porewater, indicating either a preferred uptake of Sb(V) or possibly an oxidation of Sb(III) to Sb(V) in shoots. Adding soil amendments (olivine, hematite) to the paddy soil had no effect on Sb and As concentrations in porewater.

Arsenic and antimony contamination of waters, stream sediments and soils in the vicinity of abandoned antimony mines in the Western Carpathians, Slovakia

Abstract Environmental contamination with As and Sb caused by past mining activities at Sb mines is a significant problem in Slovakia. This study is focused on the environmental effects of the 5 abandoned Sb mines on water, stream sediment and soil since the mines are situated in the close vicinity of residential areas. Samples of mine wastes, various types of waters, stream sediments, soils, and leachates of the mine wastes, stream sediments and selected soils were analyzed for As and Sb to evaluate their geochemical dispersion from the mines. Mine wastes collected at the mine sites contained up to 5166 mg/kg As and 9861 mg/kg Sb. Arsenic in mine wastes was associated mostly with Fe oxides, whereas Sb was present frequently in the form of individual Sb, Sb(Fe) and Fe(Sb) oxides. Waters of different types such as groundwater, surface waters and mine waters, all contained elevated concentrations of As and Sb, reaching up to 2150 μg/L As and 9300 μg/L Sb, and had circum-neutral pH values because of the buffering capacity of abundant Ca- and Mg-carbonates. The concentrations of Sb in several household wells are a cause for concern, exceeding the Sb drinking water limit of 5 μg/L by as much as 25 times. Some attenuation of the As and Sb concentrations in mine and impoundment waters was expected because of the deposition of metalloids onto hydrous ferric oxides built up below adit entrances and impoundment discharges. These HFOs contained >20 wt.% As and 1.5 wt.% Sb. Stream sediments and soils have also been contaminated by As and Sb with the peak concentrations generally found near open adits and mine wastes. In addition to the discharged waters from open adits, the significant source of As and Sb contamination are waste-rock dumps and tailings impoundments. Leachates from mine wastes contained as much as 8400 μg/L As and 4060 μg/L Sb, suggesting that the mine wastes would have a great potential to contaminate the downstream environment. Moreover, the results of water leaching tests showed that Sb was released from the solids more efficiently than As under oxidizing conditions. This might partly explain the predominance of Sb over As in most water samples.

Distribution, speciation and availability of antimony (Sb) in soils and terrestrial plants from an active Sb mining area

Here, we present one of the first studies investigating the mobility, solubility and the speciation-dependent in-situ bioaccumulation of antimony (Sb) in an active Sb mining area (Xikuangshan, China). Total Sb concentrations in soils are high (527–11,798 mg kg−1), and all soils, including those taken from a paddy field and a vegetable garden, show a high bioavailable Sb fraction (6.3–748 mg kg−1), dominated by Sb(V). Elevated concentrations in native plant species (109–4029 mg kg−1) underpin this. Both chemical equilibrium studies and XANES data suggest the presence of Ca[Sb(OH)6]2, controlling Sb solubility. A very close relationship was found between the citric acid extractable Sb in plants and water or sulfate extractable Sb in soil, indicating that citric acid extractable Sb content in plants may be a better predictor for bioavailable Sb in soil than total acid digestible Sb plant content.

The Desorption of Antimony(V) from Sediments, Hydrous Oxides, and Clay Minerals by Carbonate, Phosphate, Sulfate, Nitrate, and Chloride

The desorption of antimony, Sb(V), from two sediment samples by phosphate, carbonate, sulfate, chloride, and nitrate at pH 8 was examined. One highly contaminated sediment sample was taken from an Sb mine (Goesdorf, Luxembourg); the other sample was the certified reference material PACS-2 (marine sediment). Phosphate was found to have a strong mobilizing ability, whereas that of carbonate was in general weaker. For comparison, and to understand better the possible importance of individual components of the sediments, desorption experiments were performed on pure phases (i.e., hydrous oxides of Fe, Mn, and Al) and the clay minerals kaolinite and montmorillonite. In the cases of hydrous metal oxides, Sb(V) was most effectively desorbed by phosphate, followed by carbonate. Phosphate also desorbed Sb(V) from the clay minerals, whereas carbonate had no effect. The pH dependence of adsorption of Sb(V) in the absence and presence of carbonate revealed that adsorption densities were higher (except in the case of montmorillonite) in the absence of carbonate, suggesting a competition between carbonate and [Sb(OH)] for surface sites generally and a lowering of surface charge in the case of hydrous aluminum oxide. The observations are unlikely to be due to ionic strength effects because activity coefficients in the blank and spiked solutions differ by <4%. Desorption experiments on sediments with varying concentrations of phosphate and carbonate demonstrated that at environmentally relevant concentrations, desorption by phosphate is negligible, whereas the effect of carbonate is not. Sulfate, chloride, and nitrate generally had little effect. The proportion of Sb desorbed in blank experiments coincides with that mobilized in the first fraction of the Bureau Communautaire de Référence (BCR) sequential extraction (easily exchangeable and carbonate-bound fraction).

Accumulation of antimony and other potentially toxic elements in plants around a former antimony mine located in the Ribes Valley (Eastern Pyrenees)

Soil contamination by Sb is of increasing environmental concern due to the use of this amphoterous p-block element in many industrial applications. However, still little is known about the response of plants to Sb. Here we report on the accumulation of Sb and other potentially toxic elements (mainly As, Pb and Cu) in plants growing around a former Sb mine in the Ribes Valley located in the Eastern Pyrenees. Soil and plant samples were taken at six locations with different concentrations of Sb, As, and polymetallic contamination. Aqua regia and EDTA extractable chemical elements from sites with low (sites 1 and 2), moderate (site 3 and 4) and high (sites 5 and 6) pollutant burdens were analyzed. While sites 1 to 4 had alkaline soil pH (7.4–8.7), sites 5 and 6 were acidic with values of 6 and 4.6, respectively. Different herbaceous plant species (Poa annua L., Echium vulgare (L.), Sonchus asper (L.) Hill, Barbera verna (Mill.) Asch.) at the low and moderately polluted sites were able to efficiently restrict Sb and As transport to the shoots showing average concentration ranges between 5.5 and 23mgkg−1 As and 1.21mgkg−1 and 4.9mgkg−1 Sb. However, at the highly polluted acidic sites (5 and 6) only Agrostis capillaris L. was found. This grass was able to withstand up to 240mg/kg As and 68mg/kg Sb in the shoots. Antimony tolerance in this A. capillaris ecotype was due to efficient exclusion, yet under lab conditions commercial, non-resistant A. capillaris plants sown into a 50% mixture of sand with this highly polluted soil showed severe toxicity symptoms and a shoot Sb concentration of 230mg/kg Sb. In the original mine spoil soil (100% without sand) from the highly polluted sites the commercial A. capillaris was unable to grow. The mechanism of Sb resistance in the mine spoil ecotype of A. capillaris deserves further investigation.

Identification and characterization of nanosized tripuhyite in soil near Sb mine tailings

In soil near tailings from an antimony (Sb) mine, we found micro-grains coated with an antimonyrich layer. These grains were characterized in detail using multiple advanced analytical techniques such as micro-X‑ray absorption near edge structure (μ-XANES), micro-extended X‑ray absorption fine structure (μ-EXAFS), micro-X‑ray diffraction (μ-XRD), transmission electron microscope (TEM), and electron probe microanalysis (EPMA). The EPMA showed that one soil grain (grain A) locally accumulated a large amount of Sb in the secondary phases (40-61 wt% Sb 2 O 5 ) with significant Fe (20-28 wt% Fe 2 O 3 ). The spatial distribution of Sb in the grain was similar to that of iron. Both Fe μ-XANES and μ-XRD of the Sb hot spots in grain A consistently showed that the secondary products were dominantly composed of ferric antimonate, tripuhyite (FeSbO 4 ). Fits to the Sb K-edge μ-EXAFS of this phase showed second-neighbor coordination numbers -30% smaller than in bulk tripuhyite, indicating that the tripuhyite included in grain A is nanoparticulate and/or has a high structural disorder. The TEM analysis suggests that the particle size of tripuhyite in grain A was around 10 nm, which is consistent with the size range indicated by μ-XRD and μ-EXAFS. This is the first report showing tripuhyite with nanocrystallinity in natural soil to date.

Health risk associated with dietary co-exposure to high levels of antimony and arsenic in the world's largest antimony mine area

Like arsenic (As), antimony (Sb) is known to be a genotoxic element in vitro and in vivo. Sb is now recognized as a global contaminant and has aroused the global concerns recently. However, knowledge is scarce concerning the transfer of Sb from the environment to humans and the related hazards to human health. In this pilot study, the health risk and main pathway of long-term human exposure to Sb and As for residents around Chinese Xikuangshan (XKS) Sb mine, the world's largest Sb mine, were evaluated by dietary exposure and hair accumulations survey. The concentrations and species of Sb and As in food samples (n=209) from three main categories and six subcategories, and in hair samples (n=89) were determined. Residents in the vicinity of XKS had an estimated dietary intake of Sb (554μg/day) which was 1.5 times higher than the tolerable daily intake (TDI) (Sb, 360μg/day), whereas their dietary intake of inorganic As (107μg/day) was slightly lower than the provisional tolerable weekly intake (PTWI) of 15μg/kg BW/week (equal to 129μg As/day). Hair Sb and As concentrations (Sb, 15.7mg/kg, DW; As, 3.99mg/kg, DW) in XKS residents are both above the normal/toxic level. Rice, vegetables (especially leafy vegetable), drinking water, and meat/poultry were the dominant dietary intake sources of Sb for the residents. In contrast, rice was the uniquely dominant dietary intake source of As. Antimonate (Sb(V)) was the dominant Sb species in vegetables, drinking water and residents' hairs. This study highlighted the difference of exposure characteristics between Sb and As. The preliminary results suggested that dietary exposures to Sb, rather than As, was the dominant health risk to local residents. Nevertheless, the adverse effects of As levels on the health of residents still can not be ignored since the elevated As concentrations in human hair have reached the critical level for health risks. In addition, this pilot study did not consider the possible Sb and As combined effects.

Arsenic, Antimony, and Bismuth Uptake and Accumulation by Plants in an Old Antimony Mine, China

Arsenic (As), antimony (Sb), and bismuth (Bi) are metalloids that share similar chemical properties, the objective of this study was to characterize the uptake and accumulation of these metalloids by plants colonized on heavy contaminated sites in an old Sb mine. Sixty-five plant samples from seven species as well as the associated soil samples were collected at ten sites of Xikuangshan (XKS), Hunan province, China. Concentrations of As, Sb, and Bi in plants and soils were measured. As, Sb, and Bi were found to be evidently elevated due to the long history and intensive mining and smelting activities; the respective ranges for the levels of As, Sb, and Bi at the sites were 40.02-400.2mgkg(-1) As, 610-54,221mgkg(-1) Sb, and n.d. to 1,672mgkg(-1) Bi. No correlation was found between As and Sb at the sites, while Bi was found to be positively correlated with As whereas negative with Sb at the sites. In general, the contents in the plants in XKS were in the order of As > Sb > Bi, and the contents of As was positively correlated with Sb and Bi in plants. The highest contents of As and Sb recorded was 607.8mgkg(-1) As in Pteris vittata and 90.98mgkg(-1) Sb in Hippochcaete ramosissima, while the highest Bi content as 2.877mgkg(-1) Bi was measured in Buddleja davidii. Bioconcentration factors defined as the ratios of metalloids in shoots of plants to those in soils for various plants were lower than 1. The results showed plants colonized at the heavy contaminated sites in XKS had great tolerance to As, Sb, and Bi, and demonstrated similarities in plant uptake and accumulation of these three elements.

Antimony Accumulation, Growth Performance, Antioxidant Defense System and Photosynthesis of Zea mays in Response to Antimony Pollution in Soil

Antimony (Sb) pollution in the downstream farmland soil of the Sb mine area has been of a great environmental concern to the local residents. However, effects of Sb on the growth and physiology of crops are still not well known. In the present study, Sb uptake and its effect on growth, antioxidant defense system, and photosynthesis of maize (Zea mays) were investigated. Our results demonstrated that accumulation of Sb in the maize increased with increasing Sb level in the soil. Sb could be easily translocated from root to shoot with a translocation coefficient over 2.05. Plant growth and biomass were reduced due to Sb pollution. Under Sb stress, the activities of peroxidase (POD), superoxide dismutases (SOD), and catalase (CAT) responded differently. The activities of POD and SOD were inhibited when the soil Sb concentration was higher than 50 mg kg−1. CAT activity showed an increasing trend with increasing soil Sb concentration. Chlorophyll synthesis and the maximum photochemical efficiency (F V/F M) were also inhibited significantly under stress of high-level Sb in soil.

Bioaccumulation of antimony, arsenic, and mercury in the vicinities of a large antimony mine, China

To study the characteristics of antimony (Sb) bioaccumulation under high Sb background values, aquatic, amphibious and terrestrial biological samples were collected in the vicinity of the Xikuangshan (XKS) Sb mine area in China. Hydride generation-atomic fluorescence (HG-AFS) analysis showed that Sb concentrations in terrestrial invertebrates (average 30,400 μg kg − 1 dry wt.) were higher than those in aquatic (average 5200 μg kg − 1 dry wt.) and amphibian (average 2300 μg kg − 1 dry wt.) biological samples. Within 1 km distance of the XKS Sb mine area, grasshoppers ( Acrida chinensis) and earthworms ( Pheretima aspergillum) had the highest Sb amounts of 17,300 ±3200 and 43,600 ± 47,700 μg kg − 1 dry wt., respectively. No Sb biomagnifications were observed. The bioavailability of Sb was found to be lower than those of As and Hg. A preliminary conclusion is that antagonistic effects exist between Sb and Hg accumulation in biological samples from aquatic environments. Our study is the first to report such antagonistic effects between Sb and Hg. If this deduction proves to be correct, it should be taken into consideration in assessing human health risks, especially when Sb and Hg concentrations in the aquatic environments are high.

Antimony(V) Incorporation into Synthetic Ferrihydrite, Goethite, and Natural Iron Oxyhydroxides

In this study, we investigated local structures of Sb species in synthetic Sb(V)-coprecipitated and -adsorbed ferrihydrite and goethite, which are common iron(III) oxyhydroxides in environment, at various Sb/Fe molar ratios by extended X-ray absorption fine structure (EXAFS) analyses. The EXAFS analyses showed that Sb(V) is adsorbed on ferrihydrite and goethite by the formation of an inner-sphere surface complex at pH 7.5. In the EXAFS spectra of the coprecipitated ferrihydrite and goethite, some features of the spectra significantly differed from those in the adsorbed samples. The EXAFS simulation indicated that the difference is due to the larger coordination number of the Fe atom to the Sb atom in the coprecipitation samples, indicating a structural incorporation (heterovalent substitution) of Sb(V) into ferrihydrite and goethite. The incorporation of Sb(V) into the structure was also confirmed in natural iron(III) oxyhydroxides in contaminated soil near an Sb mine tailing using mu-EXAFS. This study directly provided the first evidence for the structural incorporation of Sb(V) into the iron(III) oxide structure. Our findings are important for understanding the fate of Sb in the aquatic environment because the behavior of the elements incorporated into solids by such a substitution is not greatly influenced by aquatic factors such as the pH and ionic strength because of isolation of the incorporated metal(loid) ions from the aqueous phase.

Antimony, arsenic and mercury in the aquatic environment and fish in a large antimony mining area in Hunan, China

Antimony (Sb) has received increasing attention recently due to its toxicity and potential human carcinogenicity. In the present work, drinking water, fish and algae samples were collected from the Xikuangshan (XKS) Sb mine area in Hunan, China. Results show that serious Sb and moderate arsenic (As) contamination is present in the aquatic environment. The average Sb concentrations in water and fish were 53.6 ± 46.7 μg L − 1 and 218 ± 113 μg kg − 1 dry weight, respectively. The Sb concentration in drinking water exceeded both Chinese and WHO drinking water guidelines by 13 and 3 times, respectively. Antimony and As concentrations in water varied with seasons. Fish gills exhibited the highest Sb concentrations but the extent of accumulation varied with habitat. Antimony enrichment in fish was significantly lower than that of As and Hg.

Antimony speciation and contamination of waters in the Xikuangshan antimony mining and smelting area, China

Water samples from Xikuangshan (China), the world largest antimony (Sb) mine with a Sb mining and smelting history of more than 200 years, were analyzed. These water samples ranged from stream water in the vicinity of the mining and smelting area that received seepage from ore residues to the underground mine-pit drainage. The concentrations of total Sb, Sb (III) and Sb (V) of the samples were determined by HPLC-ICP-MS. In addition, water pH and concentrations of major cations and anions were analyzed. All 18 samples demonstrated total Sb concentrations with ppm levels from 0.33 ppm to 11.4 ppm, which is two to three orders of magnitude higher compared to the typical concentration of dissolved Sb in unpolluted rivers (less than 1 ppb). This is probably the first time that such high Sb contents have been documented with complete environmental information. Distribution of total Sb and Sb species was investigated, taking into account the respective local environment (in the mining area or close to the smelter, etc.). Sb (V) was the predominant valence in all 18 samples. Only trace levels of Sb (III) were detected in 4 of the 18 samples. Geochemical speciation modeling showed the dominant species was Sb(OH)(6)(-). It is also probably the first time that such high Sb contents have been documented in the natural environment with Sb speciation distribution information. Several potential oxidation pathways are also discussed that might have facilitated the oxidation of Sb (III) in the natural environment. Signs of intoxication were observed among local mine workers with extensive exposure to different forms of Sb for a long period of time.

μ-XANES Evidence for the Reduction of Sb(V) to Sb(III) in Soil from Sb Mine Tailing

The aim of this study was to determine the mechanism of Sb immobilization occurring under reductive soil conditions. In this work, we investigated the distribution and speciation of Sb in reductive soil formed in Sb mine tailing by micro-X-ray absorption near edge structure spectroscopy (micro-XANES) and electron probe microanalyzer (EPMA). EPMA and Fe K-edge micro-XANES analyses of the soil grains indicated that Sb in soil was strongly associated with Fe(III) hydroxides secondarily formed during sedimentation. The Sb concentrations in Sb hot-spot were found to be as high as 10-30 wt % (as Sb(2)O(5)). We also found quartz particles coated by secondary rims bearing Fe(III) hydroxides and Sb. The Sb K-edge micro-XANES analyses of the rims showed that a significant amount of Sb(III) was present only at the surfaces of the rims (thickness <10 microm), indicating that Sb reduction occurred in the reducing soil. The facts suggest that the reduction to Sb(III) in the system can be an important factor for Sb immobilization under reducing conditions, since the Sb(III) sorbs more strongly on Fe(III) hydroxides than Sb(V) and its solubility is also much lower than that of Sb(V) species.

Geochemistry of soils, stream sediments and waters close to abandoned W–Au–Sb mines at Sarzedas, Castelo Branco, central Portugal

ABSTRACT In the Sarzedas area, central Portugal, the Cambrian schist–metagreywacke complex predominates and is intersected by W–Au–Sb quartz veins and Sb–Au-bearing felsitic dykes, which were exploited for W, Au and Sb at the Gatas–Santa and Pomar–Galdins mines. The soils from the Gatas–Santa and Pomar–Galdins areas contain up to 11 000 and 21 600 ppm Sb, respectively. In the Sarzedas area, the stream sediments contain up to 840 ppm Sb. Only some surface waters contain Sb, which reaches 2.6 mg l −1 . The waters have pH values of 5.5–7.3; they are neutralized by carbonate intercalations in the schist–metagrawacke complex. The mine wastes contain ferberite and sulphides, and have goethite and ferrihydrite coatings, which have up to 8.10 wt% Sb 2 O 5 and 2.26 wt% As 2 O 5 and contain inclusions of stibnite, arsenopyrite and pyrite. The highest Sb and As concentrations in soils, stream sediments and surface waters are related to the mineralized veins and dykes and mine wastes. The good correlation between W, Sb and As contents in soils from Gatas–Santa and good correlation coefficients for W–Sb, W–Pb and Sb–Pb in stream sediments from Gatas–Santa and Pomar–Galdins are due to the weathering of ferberite, stibnite, arsenopyrite and galena from mineralized veins and dykes and mine wastes. Soils, stream sediments and waters from the Sarzedas area are contaminated, which is consistent with findings for comparable effects in historical Sb mine sites elsewhere in Europe and Australasia, but the Sarzedas waters contain the highest Sb concentration and the lowest As concentration.