不确定背景值下浅水湖泊沉积物重金属生态风险评价

Potential ecological risk assessment of heavy metals in sediment with uncertain background impact in a shallow lake

基于安徽某湖泊沉积物柱状样重金属实测含量,研究了各类重金属的垂向变化趋势及来源;采用拉丁超立方抽样方法随机产生已知范围内的重金属背景值,计算沉积物重金属综合潜在生态风险水平,研究其结果不确定性,评价湖泊沉积物重金属污染程度.结果表明,沉积物重金属的含量及综合潜在生态风险水平沿深度方向呈逐渐降低的趋势,上层沉积物存在较高的综合潜在生态风险;不确定性评价方法可以在沉积物垂向上得到沉积物重金属综合潜在生态风险水平的包络面,不确定性的结果可以给出综合潜在生态风险超出风险阈值的可信度和特定置信度下的综合潜在生态风险指数置信区间;90%置信度下两个沉积物采样点上层重金属综合潜在生态风险指数(RI)的置信区间分别为340.08~412.89和271.61~327.67,处于重度综合潜在生态风险水平阈值附近的评价结果让不同风险偏好的决策者在面临修复、清淤等决策时可以做出符合自身预期的决策.

The vertical distribution and source of heavy metals in sediment were analyzed based on measured data in this study.Additionally,the potential ecological risk and pollution level of lake sediment were assessed by the Latin Hypercube Sampling method with empirical distribution of background value based on monitoring data.Results showed that the content of heavy metals and comprehensive potential ecological risk level gradually decreased with sediment depth,which indicated that the upper layer of sediment was accompanied by high risk.Uncertainty assessment method can obtain the envelope of comprehensive potential heavy metal ecological risk level in sediment vertically.Reliability of ecological risk beyond the threshold or confidence interval of potential ecological risk index with specific confidence could be given by uncertainty analysis.The comprehensive heavy metal potential ecological risk indexes with 90%confidence were in the range of 340.08~412.89 and 271.61~327.67 in the upper layers of two sampling cores,respectively.Decision-makers with different risk preferences can take restoration,sediment dredging,or other technologies based on the results,which was near the threshold of severe potential comprehensive ecological risk.This study aims to be useful for lake management and help decision-makers comprehensively assess soil and sediments risk.