The Castilseras artificial water reservoir (Almadén, South Central Spain) is receiving runoff water from the most important Hg mines of the Almadén mining district and from other small Pb-Zn mines. This reservoir constitutes the only lentic medium located within the mining district and their sediments can be considered as a sink and/or source of contaminants in the aquatic ecosystem. Then, the ecological risk assessment of these sediments can be considered as priority target in order to assess the environmental quality of the fluvial ompartment and the potential uptake of heavy metals for the biota. For this objective, sediments collected in 12 sampling stations have been studied using the Sequential Extraction Procedure (SEP). Results were evaluated using Principal Component Analysis (PCA) and different risk criteria such as Pollution Degree, Mean Probable Effect Concentration Quotient, and Risk Index. general, the high contents in Hg and other elements such as As and Pb, can be attributed to environmental liabilities of decommissioned mines. The study of the different fraction steps and their statistical multivariate treatment by PCA, showed two differentiate groups of elements in the easily leachable fraction F1. This fact is indicative of the presence of sulfate salts and secondary precipitates of carbonates as the main sink for easily accessible metallic elements. In the reducible fraction F2, chemical analysis revealed a significant relationship between the majority of the analyzed elements and the Fe oxy-hydroxides, with exception of Co, Hg and Ni, which are preferentially associated with Mn oxy-hydroxides. In the oxidisable fraction (F3), a significant relationship between Cu, Fe, Hg and Zn (most representative metals of the ore deposits in the district) and sulfides/organic matter was observed. Finally, the residual fraction F4 showed a first group constituted by As, Ca, Co, Mg, Mn and Ni, elements which are related to the presence of silicates, and a second group related to sulfides or secondary sulfates. The environmental assessment based on the aforementioned criteria provides risk levels varying from moderate to high. The risk appears to be higher at the head of the reservoir, where the highest concentrations of heavy metals and metalloids in the sediment are due to a selective accumulation of fine-grained particles.

Heavy metal speciation and risk assessment in freshwater sediments of an artificial reservoir in the Almadén mining district, Spain

COVELLI, STEFANO;
2015

Abstract

The Castilseras artificial water reservoir (Almadén, South Central Spain) is receiving runoff water from the most important Hg mines of the Almadén mining district and from other small Pb-Zn mines. This reservoir constitutes the only lentic medium located within the mining district and their sediments can be considered as a sink and/or source of contaminants in the aquatic ecosystem. Then, the ecological risk assessment of these sediments can be considered as priority target in order to assess the environmental quality of the fluvial ompartment and the potential uptake of heavy metals for the biota. For this objective, sediments collected in 12 sampling stations have been studied using the Sequential Extraction Procedure (SEP). Results were evaluated using Principal Component Analysis (PCA) and different risk criteria such as Pollution Degree, Mean Probable Effect Concentration Quotient, and Risk Index. general, the high contents in Hg and other elements such as As and Pb, can be attributed to environmental liabilities of decommissioned mines. The study of the different fraction steps and their statistical multivariate treatment by PCA, showed two differentiate groups of elements in the easily leachable fraction F1. This fact is indicative of the presence of sulfate salts and secondary precipitates of carbonates as the main sink for easily accessible metallic elements. In the reducible fraction F2, chemical analysis revealed a significant relationship between the majority of the analyzed elements and the Fe oxy-hydroxides, with exception of Co, Hg and Ni, which are preferentially associated with Mn oxy-hydroxides. In the oxidisable fraction (F3), a significant relationship between Cu, Fe, Hg and Zn (most representative metals of the ore deposits in the district) and sulfides/organic matter was observed. Finally, the residual fraction F4 showed a first group constituted by As, Ca, Co, Mg, Mn and Ni, elements which are related to the presence of silicates, and a second group related to sulfides or secondary sulfates. The environmental assessment based on the aforementioned criteria provides risk levels varying from moderate to high. The risk appears to be higher at the head of the reservoir, where the highest concentrations of heavy metals and metalloids in the sediment are due to a selective accumulation of fine-grained particles.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11368/2845649
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