鄱阳湖表层沉积物中砷及重金属赋存形态及其潜在生态风险

重金属污染是水体沉积物污染的主要问题之一，研究沉积物中重金属元素的赋存形态，探索水体中重金属的来源，可以为水体重金属污染治理修复提供理论基础。采用BCR三步连续提取法对鄱阳湖枯水期表层沉积物中As和7种重金属元素（Cd、Co、Cr、Cu、Ni、Pb和Zn）的赋存形态进行了研究，并基于重金属风险评价代码（Risk Assessment Code, RAC）方法评估了鄱阳湖表层沉积物中的As和7种重金属元素的潜在生态风险。结果表明，鄱阳湖表层沉积物中As、Co、Cr、Cu、Ni和Zn主要以残渣态的形式存在(6160%~8518%)；Pb主要以残渣态（5097%）和铁锰氧化物结合态（4102%）为主要的赋存形态，其可提取态所占比例为4903%，具有较高的二次释放潜力；Cd的赋存形态主要以弱酸提取态（4160%）和铁锰氧化态（2719%）为主，其可提取态所占比例高达7749%，潜在生态风险较大。RAC分析结果表明，鄱阳湖表层沉积物Cd的生态风险整体上位于高风险，需要加强对鄱阳湖Cd污染的关注。所有站点Cr的弱酸提取态所占比例均低于1%，表明鄱阳湖Cr污染的生态风险为无风险，As、Ni和Pb属于低风险，而Cu、Co和Zn位于低风险至中等风险

SPECIATION AND POTENTIAL ECOLOGICAL RISK ASSESSMENT OF AS AND HEAVY METALS IN SURFACE SEDIMENTS OF POYANG LAKE

Heavy metal pollution is one of the major problems in aquatic sediment. Studies on the sources and chemical speciation of heavy metals in aquatic sediment can provide a theoretical basis for the remediation of heavy metal pollution in aquatic sediment. BCR three stage sequential extraction procedure was applied to examine the chemical speciation of As and 7 heavy metals (Cd,Co,CrM,Cu,Ni,Pb and Zn) in sediments of Poyang Lake, and the potential ecological risks of As and these 7 heavy metals were assessed based on the risk assessment cod (RAC) criteria, which is based on the percentage of metal present in acid soluble fraction. The average total concentrations of As, Cd, Co, Cr, Cu, Ni, Pb, and Zn in sediment of Poyang Lake were 1574 mg/kg, 052 mg/kg, 1557 mg/kg, 6903 mg/kg, 3092 mg/kg, 2474 mg/kg, 6717 mg/kg, 8028 mg/kg, respectively, and the concentrations of all the trace elements were higher than their background values of soil in Jiangxi Province. The major speciation of As, Co, Cr, Cu, Ni and Zn in sediment of Poyang Lake was residual fraction (6160%-8518%). While Pb showed the highest percentages in the residual fraction (5097%) and Fe Mn oxide fractions (4102%), and the percentage of extractable Pb form was 4903%, implying that the potential risk of secondary release of Pb in Poyang Lake was high. Cd was mostly concentrated in acid extractable fraction (4160%) and Fe Mn oxide fraction (2719%), and the extractable Cd (F1+F2+F3) was as high as 7749%, indicating that Cd posed a high risk to local environments. According to the Risk Assessment Code (RAC), major portion of Cd was contained in acid extractable fraction (4160%), suggesting that the potential ecological risk of Cd in Poyang Lake was high, and more attention should be paid to the Cd pollution in Poyang Lake. Cr in acid soluble fraction at all the sampling sites was less than 1% of the total content and therefore came under the no risk category. Speciation pattern of As, Ni, and Pb showed low risk to aquatic environment health in Poyang Lake, and Cu, Co, and Zn showed low to medium risk to the environment. The extractable contents (F1+F2+F3) of As, Cd, Co, Cr, Cu, Ni, Pb, and Zn in sediment of Poyang Lake were 366 mg/kg, 042 mg/kg, 603 mg/kg, 824 mg/kg, 1200 mg/kg, 3205 mg/kg, and 2749 mg/kg, respectively, and their spatial variability coefficients were 2514%, 8453%, 4240%, 3421%, 13422%, 5078%, 3742%, and 5504%, respectively, suggesting that spatial distributions of Cd, Cu, Ni, and Zn in sediment of Poyang Lake are inhomogeneous