Assessment of mercury bioavailability in garden soils around a former nonferrous metal mining area using DGT, accumulation in vegetables, and implications for health risk.

Mercury (Hg) is a toxic, non-essential element for living organisms, frequently present in high concentrations in soils from industrial areas. The total, dissolved, and labile Hg concentrations in garden soils and their accumulation in edible vegetables (onion, garlic, lettuce, and parsley) grown on contaminated soils in localities situated a former mining area were evaluated. The labile Hg fraction was estimated by diffusive gradient in thin films (DGT). The soil-to-vegetable transfer factors, as well as the health risk by exposure to Hg, were calculated based on the labile Hg concentration in soil. The total Hg concentration in soil varied widely (0.11-3.77 mg kg-1), Hg in soil solution ranged between 2.14 and 20.2 µg L-1 and labile Hg between 1.13 and 18.6 µg L-1. About 36-96% (84% on average) of the Hg concentration in soil solution was found in labile form. Multivariate analysis revealed significant correlations between the labile Hg concentration in soil and Hg accumulated in vegetables. The hazard indices showed that, although the study area is affected by legacy pollution, exposure to soil and consumption of locally grown vegetables do not pose health risks.

Assessment of Availability and Human Health Risk Posed by Arsenic Contaminated Well Waters from Timis-Bega Area, Romania.

Mobilization of As from geological materials into ground and drinking water sources may represent an important threat to human health. The objective of this study was to assess the As concentration and availability in underground water used as drinking water sources. Water samples were collected from public and private wells in Timis-Bega area of Pannonian Basin, West Romania. Total-dissolved As measured after "classical" filtration of water samples was in the range of 0.10-168 µg L-1, thus exceeding the guideline value in majority of the samples. The aim of this study was also to assess the "truly dissolved" concentrations of As considered as available concentrations, in well waters, after passive sampling by Diffusive Gradients in Thin-films (DGT). The results showed that over 70% of total-dissolved As is in available forms. The obtained data were used to evaluate the risks of using the wells as drinking water source. Hazard quotients for ingestion and dermal pathways and hazard index (HI) for exposure to As were calculated. The HI values > 1 found that majority of samples indicated a health risk for local residents.

Assessment of metals bioavailability to vegetables under field conditions using DGT, single extractions and multivariate statistics.

BACKGROUND: The metals bioavailability in soils is commonly assessed by chemical extractions; however a generally accepted method is not yet established. In this study, the effectiveness of Diffusive Gradients in Thin-films (DGT) technique and single extractions in the assessment of metals bioaccumulation in vegetables, and the influence of soil parameters on phytoavailability were evaluated using multivariate statistics. Soil and plants grown in vegetable gardens from mining-affected rural areas, NW Romania, were collected and analysed. RESULTS: Pseudo-total metal content of Cu, Zn and Cd in soil ranged between 17.3-146 mg kg-1, 141-833 mg kg-1 and 0.15-2.05 mg kg-1, respectively, showing enriched contents of these elements. High degrees of metals extractability in 1M HCl and even in 1M NH4Cl were observed. Despite the relatively high total metal concentrations in soil, those found in vegetables were comparable to values typically reported for agricultural crops, probably due to the low concentrations of metals in soil solution (Csoln) and low effective concentrations (CE), assessed by DGT technique. Among the analysed vegetables, the highest metal concentrations were found in carrots roots. By applying multivariate statistics, it was found that CE, Csoln and extraction in 1M NH4Cl, were better predictors for metals bioavailability than the acid extractions applied in this study. Copper transfer to vegetables was strongly influenced by soil organic carbon (OC) and cation exchange capacity (CEC), while pH had a higher influence on Cd transfer from soil to plants. CONCLUSIONS: The results showed that DGT can be used for general evaluation of the risks associated to soil contamination with Cu, Zn and Cd in field conditions. Although quantitative information on metals transfer from soil to vegetables was not observed.

Environmental and socioeconomic assessment of impacts by mining activities-a case study in the Certej River catchment, Western Carpathians, Romania.

BACKGROUND, AIM AND SCOPE: In the region of the Apuseni Mountains, part of the Western Carpathians in Romania, metal mining activities have a long-standing tradition. These mining industries created a clearly beneficial economic development in the region. But their activities also caused impairments to the environment, such as acid mine drainage (AMD) resulting in long-lasting heavy metal pollution of waters and sediments. The study, established in the context of the ESTROM programme, investigated the impact of metal mining activities both from environmental and socioeconomic perspectives and tried to incorporate the results of the two approaches into an integrated proposition for mitigation of mining-related issues. STUDY SITE: The small Certej catchment, situated in the Southern Apuseni Mountains, covers an area of 78 km(2). About 4,500 inhabitants are living in the basin, in which metal mining was the main economic sector. An open pit and several abandoned underground mines are producing heavy metal-loaded acidic water that is discharged untreated into the main river. The solid wastes of mineral processing plants were deposited in several dumps and tailings impoundment embodying the acidic water-producing mineral pyrite. METHODS: The natural science team collected samples from surface waters, drinking water from dug wells and from groundwater. Filtered and total heavy metals, both after enrichment, and major cations were analysed by inductively coupled plasma optical emission spectroscopy (ICP-OES). Major anions in waters, measured by ion chromatography, alkalinity and acidity were determined by titration. Solid samples were taken from river sediments and from the largest tailings dam. The latter were characterised by X-ray fluorescence and X-ray diffraction. Heavy metals in sediments were analysed after digestion. Simultaneously, the socioeconomic team performed a household survey to evaluate the perception of people related to the river and drinking water pollution by way of a logistic regression analysis. RESULTS AND DISCUSSION: The inputs of acid mine waters drastically increased filtered heavy metal concentrations in the Certej River, e.g. Zn up to 130 mg L(-1), Fe 100 mg L(-1), Cu 2.9 mg L(-1), Cd 1.4 mg L(-1) as well as those of SO(4) up to 2.2 g L(-1). In addition, river water became acidic with pH values of pH 3. Concentrations of pollutant decreased slightly downstream due to dilution by waters from tributaries. Metal concentrations measured at headwater stations reflect background values. They fell in the range of the environmental quality standards proposed in the EU Water Framework Directive for dissolved heavy metals. The outflow of the large tailing impoundment and the groundwater downstream from two tailings dams exhibited the first sign of AMD, but they still had alkalinity. Most dug wells analysed delivered a drinking water that exhibited no sign of AMD pollution, although these wells were a distance of 7 to 25 m from the contaminated river. It seems that the Certej River does not infiltrate significantly into the groundwater. Pyrite was identified as the main sulphide mineral in the tailings dam that produces acidity and with calcite representing the AMD-neutralising mineral. The acid-base accounting proved that the potential acid-neutralising capacity in the solid phases would not be sufficient to prevent the production of acidic water in the future. Therefore, the open pits and mine waste deposits have to be seen as the sources for AMD at the present time, with a high long-term potential to produce even more AMD in the future. The socioeconomic study showed that mining provided the major source of income. Over 45% of the households were partly or completely reliant on financial compensations as a result of mine closure. Unemployment was considered by the majority of the interviewed persons as the main cause of social problems in the area. The estimation of the explanatory factors by the logistic regression analysis revealed that education, household income, pollution conditions during the last years and familiarity with environmental problems were the main predictors influencing peoples' opinion concerning whether the main river is strongly polluted. This model enabled one to predict correctly 77% of the observations reported. For the drinking water quality model, three predictors were relevant and they explained 66% of the observations. CONCLUSIONS: Coupling the findings from the natural science and socioeconomic approaches, we may conclude that the impact of mining on the Certej River water is high, while drinking water in wells is not significantly affected. The perceptions of the respondents to pollution were to a large extent consistent with the measured results. RECOMMENDATIONS AND PERSPECTIVES: The results of the study can be used by various stakeholders, mainly the mining company and local municipalities, in order to integrate them in their post-mining measures, thereby making them aware of the potential long-term impact of mining on the environment and on human health as well as on the local economy.