水源涵养和生态保育清洁小流域河流沉积物重金属的特征及潜在风险——以董铺—大房郢水库为例

Characteristics and Potential Risks of Heavy Metal in Sediments in Water Conservation and Ecological Clean Watershed——A Case Study at Dongpu-Dafangying Reservoir

[目的]为了解安徽省合肥市饮用水源地水源涵养和生态保育清洁小流域(董铺水库和大房郢水库)汇水河流表层沉积物中重金属对下游水库的影响。[方法]在该区域3条主要汇水河流采集了23个沉积物样品,分别测定了沉积物中7种重金属(Zn,Cu,Cr,As,Cd,Pb和Hg)的含量,并采用潜在生态风险指数法(I_R)和地累积指数法(I_(geo))评估其潜在生态风险,主成分分析法解析其可能来源。[结果]研究区域重金属分布存在差异,As和Cd在泗水河上的C_1和C2两点含量超过了维护人体健康的土壤环境质量二级标准限值,且Cd在此两点的易利用态占比为34.97%和37.67%,具有较强的生物有效性;Cd生态风险指数普遍偏高,达强度等级,其中泗水河上的C_1和C2两点达极强等级;同时S_8点Hg生态风险达到强度等级,其余6种重金属生态风险水平较低。该区域重金属主要来自于人与自然混合源和人为源,贡献率分别为51.11%和27.70%。[结论]在泗水河下游流域Cd污染较为突出,为减小其对下游水库的影响,应加强Cd的污染治理。

[Objective]We aim to investigate the effects of heavy metals in surface sediments of catchment rivers in drinking water source areas(Dongpu reservoir and Dafangying reservoir)in Hefei City of Anhui Province on downstream reservoirs.[Methods]Twenty-three sediment samples were collected from three major river catchment to determine the concentrations of Zn,Cu,Cr,As,Cd,Pb and Hg.The potential ecological risk was assessed by the potential ecological risk index(IR)and cumulative index method(Igeo).The principal component analysis was used to assess the possible sources of the heavy metals.[Results]The distribution of heavy metal in the study area was different.The contents of As and Cd in sampling locations of C1 and C2 on the Surabaya river exceeded the secondary standard limit of soil environmental quality for maintaining human health,and the available Cd in these two sites accounted for 34.97%and 37.67%of total Cd concentration,showing a strong biological availability.Cd ecological risk index was generally high,reaching the intensity level,among which C1 and C2 on the surabaya river reached the extremely strong level.In addition,the ecological risk of Hg for location S8 reached the intensity level,and the ecological risk level of the remaining6 heavy metals was relatively low.The heavy metals in this region mainly came from human-natural mixed sources and human-made sources,with contribution rates of 51.11%and 27.70%,respectively.[Conclusion]Cd pollution is more serious in the lower reaches of the Sishui River.In order to reduce its impact on the downstream reservoir,Cd pollution control should be strengthened.