白洋淀表层沉积物重金属形态分布特征及生态风险评价

为了研究白洋淀全域表层沉积物重金属污染程度，采用BCR 3步提取法分析了沉积物中6种重金属（Cd、Cr、Cu、Ni、Pb和Zn）的含量及其赋存形态，讨论了6种重金属的生物可利用性大小，并运用次生相与原生相比值法（RSP）、潜在生态风险指数法（RI）和聚类分析进行了生态风险评价及重金属污染来源探讨.研究表明，白洋淀表层沉积物中重金属Cd和Cu含量均值分别达到背景值的2.9倍和1.3倍.Cd的可交换态及碳酸盐结合态和铁锰氧化物结合态的质量分数达到51.20%，生物可利用性较大；Pb主要赋存于铁锰氧化物结合态；Cr、Cu、Ni和Zn以残渣态为主要的存在形式.白洋淀的首要污染因子是Cd，整体面临较高Cd风险.圈头片风险最高，端村片风险最低；南刘庄片区域内风险相差较大，其中N4为白洋淀全域最高风险点.源解析结果显示，Cd、Cu、Pb和Ni受人类活动因素较多，Cr和Zn则更多的受到自然因素影响.

Spatial distribution, fractionation and ecological risk of heavy metals in surface sediments from Baiyangdian Lake

The purpose of our study was to comprehensively investigate the pollution of the surface sediments by heavy metals in Baiyangdian Lake (BYDL). In our study, the contents of six heavy metals (Cd, Cr, Cu, Ni, Pb, and Zn) and their existing forms in the sediments were analyzed using the modified BCR protocol. The Rations of Secondary Phase and Primary Phase method (RSP), Comprehensive Potential Ecological Risk Index method (RI) and Cluster Analysis method were used for ecological risk assessment and heavy metal pollution sources identification. The results demonstrated that the average content of Cd and Cu in the surface sediments of BYDL was 2.9 times and 1.3 times of the background value, respectively. The water/acid-soluble fraction and oxidizable fraction of Cd accounted for a relatively high proportion of the Cd total content. Pb mainly existed in the oxidizable fraction, whereas Cr, Cu, Ni and Zn mainly existed in the residual fraction. The difference in heavy metal content between BYDL regions mainly resulted from changes in secondary phase content. Taken together, Cd posed the highest potential pollution risk among all the heavy metals. The ecological risk of Quantou area is the highest and the risk of Duancun area is the lowest among all the polluted areas. Additionally, the ecological risk of sampling sites in Nanliuzhuang area was quite different, among which N4 was the highest risk point in Baiyangdian Lake. Source analysis showed that Cd, Cu, Pb and Ni were mainly attributed to human activities, while Cr and Zn were affected by natural factors.