高原深水湖泊沉积物重金属背景值研究及潜在生态风险评估

为了解青藏高原湖区典型深水湖泊——羊卓雍错沉积物重金属污染水平及当前生态风险，以表层沉积物为基础，采用参考元素法计算研究区的重金属背景值，并对重金属生态风险状况进行了初步评估.结果表明:①羊卓雍错沉积物中重金属Cr、Ni、Cu、Zn、As、Cd、Hg和Pb的背景值分别为（27.49±11.39）（22.53±4.74）（15.93±6.44）（28.22±9.68）（11.96±2.34）（0.22±0.11）（0.04±0.03）（11.59±5.29）mg/kg.②羊卓雍错表层沉积物重金属生态风险指数为66.96~227.79，平均值为119.45，各采样点重金属潜在生态风险均处于低风险或中等风险，流域整体处于低风险.③羊卓雍错表层沉积物中8种重金属的潜在生态风险顺序为Hg > Cd > As > Pb > Ni > Cu > Cr > Zn，各重金属生态风险指数范围为0.97~123.25，平均值在1.01~56.67之间，除Hg处于中等风险外，其余7种重金属均处于低风险状态.研究显示，参考元素法可便捷、准确地计算受人类活动影响较小湖泊的沉积物重金属背景值，当前羊卓雍错沉积物中重金属质量分数主要受背景值影响，而人类活动对重金属污染亦有贡献，需适当加强关注. 

Determination of Background Value and Potential Ecological Risk of Heavy Metals in Sediments of a Deep Plateau Lake

To survey the background value and understand the pollution level or the ecological risk of heavy metal in surface sediment from Yamdrok Lake, a typical deep-water lake in Qinghai-Tibet Plateau, reference element method was applied to calculate the background value, and the potential ecological risk (E_ri) of heavy metals in sediments was studied. The results indicated that the background value of Cr, Ni, Cu, Zn, As, Cd, Hg, and Pb in the sediment were (27.49±11.39) (22.53±4.74) (15.93±6.44) (28.22±9.68) (11.96±2.34) (0.22±0.11) (0.04±0.03) (11.59±5.29) mg/kg, respectively. Based on these background values, the ecological risk index of the heavy metals in the surface sediments from the Yamdrok Lake varied from 66.96 to 227.79 (the mean value of 119.45), and the potential ecological risks of the heavy metals in the Yamdrok Lake Basin were at low level. The (E_ri) value was Hg > Cd > As > Pb > Ni > Cu > Cr > Zn, ranging from 0.97 to 123.25, with the mean value of 1.01-56.67. The potential ecological risks of each heavy metal were low except Hg. The reference element and the statistical methods can conveniently and accurately calculate the background values of the heavy metals in the surface sediments from the lake which is less affected by the anthropogenic activities. The mass fractions of the heavy metals in surface sediments of the Yamdrok Lake are mainly affected by the background value, as well as the anthropogenic activities, which deserves more attentions.