巢湖南淝河河口底泥污染特征及疏浚决策

为了解巢湖南淝河河口区域底泥污染特征，为底泥疏浚提供决策依据，对该区域底泥中营养物、重金属含量及释放特征进行分析，并采用有机指数法、污染指数法及潜在生态风险评价对底泥的污染状况进行评估.结果表明，调查区域总氮（TN）、总磷（TP）以及有机质（OM）的均值为1461 mg·kg^-1、438 mg·kg^-1和1.77%，在表层（0~10cm）富集明显，随着底泥深度增加有逐渐降低的趋势.有机污染指数和污染指数结果表明，表层底泥（0~10 cm）总氮、有机质处于中度污染状态，而总磷处于重度污染状态，且随着底泥深度的增加，污染风险逐渐降低，并在30 cm以下处于低风险.静态释放结果发现底泥氨氮（NH₄⁺-N）和TP的平均释放通量分别为8.04 mg·（m²·d）^-1和0.19 mg·（m²·d）^-1，释放潜力较大，且与底泥营养物污染区域一致.对于底泥重金属而言，除Cr和Ni外的其它6种重金属含量均高于安徽省土壤背景值，其中Hg和Cd的含量超标最为严重，且重金属潜在生态风险结果表明，表层（0~20 cm）底泥均处于重污染风险等级，而30 cm以下底泥重金属降为低风险等级.底泥重金属浸出毒性实验结果表明，该区域底泥疏浚后重金属释放风险较低，不属于危险废物.根据以上结果，综合确定了南淝河口区域的重点疏浚面积（3.93 km²）和深度（30 cm），为底泥疏浚提供了重要依据.

Sediment Pollution Characteristics and Dredging in the Nanfei River Estuary, Chaohu Lake

To clarify the endogenous pollution characteristics of sediments in the Nanfei River estuary, Chaohu Lake, and provide a theoretical basis for the dredging works, the organic index, pollution index, and potential ecological risk were determined. The results show that the average total nitrogen (TN), total phosphorus (TP), and organic matter (OM) content of the sediment was 1461 mg·kg^-1, 438 mg·kg^-1, and 1.77%, respectively, showing enrichment in the surface layer (0-10 cm). The nutrient pollution status and TP pollution index show that the organic pollution level was moderate and the TP pollution was severe. Furthermore, the pollution risk gradually reduced with sediment depth, representing a low risk at depths below 30 cm. Static release results showed that the average release fluxes of NH₄⁺-N and TP in the sediment were 8.04 mg·(m²·d)^-1 and 0.19 mg·(m²·d)^-1, respectively, and showed highest release potentials consistent with areas of sediment nutrient pollution. Except for Cr and Ni, the concentrations of six heavy metals were higher than the soil background values for Anhui Province, and the concentrations of Hg and Cd far exceeded the standards. According to the assessment of potential ecological risk from heavy metals, the 0-20 cm sediments present a high level of risk and sediments below 30 cm have a low level of risk. Heavy metal leaching toxicity indicated that the risk of heavy metal release after dredging is low and non-hazardous. These results were used to determine the key dredging area (3.93 km²) and depth (30 cm) for the Nanfei River estuary, providing an important basis for future dredging activities.