STUDY OF Ag AND Sn IN SURFACE SEDIMENTS OF THE CAU RIVER - THAI NGUYEN CITY: SPECIATION OF METALS AND ECOLOGICAL RISKS

Abstract

Ag and Sn are not classified as hazardous but both have potential impacts on the environment and ecosystems, so the control and assessment of contamination levels for them is still very necessary, especially today, the mining activities of minerals and nanomaterials are growing, leading to the release of more and more Ag and Sn. Therefore, this study focuses on two metals Ag, Sn in the sediments of the Cau river - Thai Nguyen. The fractions of Ag and Sn in the sediment were extracted by the modified extraction procedure of BCR and Tessier. The ecological risk levels of Ag and Sn were assessed through the geological accumulation index (Igeo), the risk assessment index (%RAC). The results showed that, the fractions of both Ag and Sn followed the order F5 > F3 > F4 > F1,2 (F1,2 - exchangeable and bound to carbonates; F3 - bound to iron and manganese oxides; F4 - bound to organic matter; F5 - residual) while the percentage of F4, F1,2 of Ag is tiny, that of Sn is higher. The concentration of Sn ranges from 21.04 mg/kg to 26.73 mg/kg while the Ag concentration is only from 2.08 mg/kg to 6.71 mg/kg. The contamination level of Ag is higher than that of Sn according to the Igeo index, but the ecological risk of Ag is lower than that of Sn according to the %RAC index.