Distribution and mobility of arsenic in the Río Dulce alluvial aquifers in Santiago del Estero Province, Argentina
| Autor: | Mattias Claesson, Gunnar Jacks, Juan M. Thir, Jens Fagerberg, Ondra Sracek, Raul A. Martin, Angel del R. Storniolo, Prosun Bhattacharya, Jochen Bundschuh |
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| Rok vydání: | 2004 |
| Předmět: |
chemistry.chemical_classification
Environmental Engineering 0207 environmental engineering Mineralogy Sediment 02 engineering and technology 010501 environmental sciences 01 natural sciences Pollution 6. Clean water Volcanic glass chemistry.chemical_compound chemistry 13. Climate action Environmental chemistry Environmental Chemistry Carbonate Organic matter Leaching (agriculture) 020701 environmental engineering Waste Management and Disposal Dissolution Groundwater 0105 earth and related environmental sciences Volcanic ash |
| Zdroj: | The Science of the total environment. 358(1-3) |
| ISSN: | 0048-9697 |
| Popis: | Factors controlling arsenic (As) mobilization in the aquifers of the Río Dulce alluvial cone were investigated. Groundwater analyses show severe As contamination (average concentration of 743 mug/L) from geogenic sources, but spatial variability of As concentration is considerable. Sequential leaching of sediment samples from unsaturated zone using de-ionised water, bicarbonate, acetate, and oxalate extracted As to different extents. Sediment oxalate extraction showed that Al and Mn oxide and hydroxides are more abundant than Fe oxides and hydroxides, in spite of similar total Fe, Mn, and Al concentrations in the sediment. Speciation calculations performed for saturated zone samples indicated that Fe and Al oxides and hydroxides are stable in groundwater, suggesting that As adsorption processes may be to some extent controlled by the presence of Fe and Al mineral phases. Principal Component Analysis (PCA) showed that As is related to F, V, Mo, B, Si, most likely due to their common origin in volcanic ash. This suggests the volcanic ash as the probable source of groundwater As. Locally, elevated pH values linked to carbonate dissolution, cation exchange, and dissolution of silicates promote release of adsorbed As. Another factor contributing to the release of As locally may be the input of organic matter from excessive irrigation. The conceptual model of As release includes: i) As influx from dissolution of volcanic glass in volcanic ash, ii) adsorption of As on the surface of Fe and Al mineral phases in relatively low pH zones, and iii) high mobility of As in high pH zones. Future work should be focused on the determination of mineralogical forms of As in volcanic ash and on detailed investigation on factors controlling As mobility. |
| Databáze: | OpenAIRE |
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