青海湖流域沙柳河下游沉积物中重金属污染风险评价

对青海湖流域沙柳河下游沉积物中As、Cd、Pb、V、Cr、Mn、Ni、Cu和Zn 9种重金属元素的含量进行了分析测定,采用污染系数、富集系数、地累积指数和潜在生态危害指数评估了其污染程度。结果表明：无论在横向还是纵向上,重金属元素含量均低于青海湖土壤背景值;重金属元素污染系数和富集系数均小于2,且大多数样品的值低于1（高于1者多为Cd、Cu、Ni、Zn,且具高值）;地累积指数均为负值（除QB-19中Cd和Cu分别为0.10和0.02）;潜在生态风险因子大多低于30,潜在生态危害指数大多低于70。沙柳河下游沉积物尚未出现重金属污染,具有低的生态风险,但该流域重金属的人为排放确实存在（主要是Cd、Cu、Ni、Zn等）,而且在近代排放更为显著。

Pollution and Potential Ecological Risk of Heavy Metals in Sediment from the Lower Reaches of Shaliuhe River,Qinghai Lake Watershed

Heavy metals (including As, Cd, Pb, V, Cr, Mn, Ni, Cu and Zn) concentrations in sediment from the lower reaches of Shaliuhe River in Qinghai Lake watershed were investigated by inductively coupled plasma mass spectrometry. The pollution coefficient (P_i), enrichment factor (EF), geoaccumulation index (I_geo) and potential ecological risk index (RI) were applied for assessing the status of sediment heavy metal pollution and the extent of potential ecological risk. The results showed that the mean concentrations of As, Cd, Pb, V, Cr, Mn, Ni, Cu and Zn were 10.4±1.5 mg/kg, 0.12±0.05 mg/kg, 18.7±3.5 mg/kg, 63.6±7.7 mg/kg, 49.1±8.9 mg/kg, 618±100 mg/kg, 24.9±4.8 mg/kg, 19.7±6.6 mg/kg and 68.1±13.7 mg/kg, respectively. These heavy metals concentrations in both spatial and temporal sediments are lower than the average soil content of Qinghai Lake watershed. Both P_i and EF of all the elements in sediment samples are lower than 2, and most of them are lower than 1. The heavy metals that have high value of P_i and EF are mainly Cd, Cu, Ni and Zn. The I_geo of most elements are negative except Cd and Cu in QB-19. Besides Cd in three surface sediment samples (QB-19, QB-23 and QB-30), the potential ecological risk factor (E_i) of the heavy metals are lower than 30, and the RI of the heavy metals are lower than 70 except for the three surface sediment samples mentioned above. The results suggest that sediment in the lower reaches of Shaliuhe River has not been polluted, and it has low potential ecological risk. However, anthropogenic contribution for heavy metals (especially Cd, Cu, Ni and Zn) do exists in the Shaliuhe River watershed, and it was significant in modern times.