| 摘要: |
The Wuli Estuary and its offshore area, the Bay of Jinzhou, have received large amount of wastewater and smelting slag from a non-ferrous smelter for decades. We collected three sediment cores from the Wuli Estuary, the middle and the mouth of the Bay of Jinzhou, respectively. Chemical sequential extraction and X-ray absorption near edge structure spectrometry (XANES) for arsenic (As) accompanying with Fe, Mn, TOM, S, and Ca analyses were conducted to investigate As retention and remobilization in this estuary–bay system. The concentrations of As in the sediment (up to 3400 μg/g) and porewater (up to 1100 μg/L) have been significantly elevated in the Wuli Estuary and serious As contamination has been spreading to the Bay of Jinzhou. Sequential extraction displayed that adsorbed As was the dominant form of As in sediments from the Wuli Estuary. But in the Bay of Jinzhou, XANES data showed that a portion of As (b10%) was precipitated as As sulfides. Correlation analysis showed that total As (AsT)/HCl extractable As (AsHCl) in sediment correlated well with total Fe (FeT) and HCl extractable Fe (FeHCl) in the estuary, with FeHCl, total S (ST) and acid volatile sulfur (AVS) in the middle of the bay, and with AVS in the mouth of the bay. The results indicated that As retention in the Wuli Estuary is very likely Fe-controlled region while the impact of S becomes more pronounced in the Bay of Jinzhou. Pseudo partition coefficients (pseudo-Kd) for AsT (the ratio of dissolved AsT in porewater to AsT in sediment) decreased systematically from the Wuli Estuary to the mouth of the Bay of Jinzhou, indicating that mobility of As decreased during the migration and digenetic processes. The dominant form of dissolved As in porewater was present in the form of AsIII (87–100%) in the Wuli Estuary. The reduction of arsenate (AsV) to arsenite (AsIII) (23–91%) mediated by microbial activities was the most important cause for As release from solid to aqueous phase, whereas the role of reductive dissolution of Fe in remobilization of As was likely very limited. |
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