【摘要】 沉积物中重金属污染评价的常用方法——地累积指数法,可定量分析确定点位特定重金属污染程度,但在流域重金属污染评价或多种重金属复合污染评价中难以适用。针对特定重金属污染评价情景,本文将最大浓度与浓度平均值以内梅罗指数法引入地累积指数法中;针对复合污染评价情景,综合考虑重金属浓度及其生态毒性,提出"等当量生态毒性指数"的概念,以此为依据筛选出生态危害贡献最大的重金属,将其浓度变化指数及多种重金属浓度变化指数的平均值以内梅罗指数法引入地累积指数法中。改进的地累积指数法既考虑了重金属浓度的最大值,又兼顾各重金属的毒性特征。本文以丹江口水库支流朝北河沉积物中重金属的污染评价为例,验证改进的地累积指数法的评价结果。在评价流域特定重金属污染时,改进的地累积指数法避免了地累积指数取平均值忽视重污染点位的问题,能够有效识别出流域内Hg元素在个别点位存在的严重污染,各重金属污染等级排序结果更有利于全面反映流域内重金属污染情况。在评价重金属复合污染时,改进的地累积指数法与潜在生态危害指数法的评价结果总体一致,且有效避免了潜在生态危害指数法直接利用未修正重金属毒性系数造成的评价结果不合理的问题。更多还原

【Abstract】 The geo-accumulation index method(GAI)is a commonly used approach for the quantitative assessment of heavy metal pollution in sediments. However, it can hardly be adapted to conduct an integrated evaluation of multi-heavy metals pollution in an entire river basin as it focuses only on a specific heavy metal in individual sampling locations. This investigation presents a novel approach in which pollution of multi-heavy metals sampled from different locations in a basin can be systematically assessed. Two indicators of both maximum and average concentrations were embedded into the GAI method through the Nemerow index method. The concept of"Equivalent Eco-Toxicity Index"was proposed considering the integrated effects on environment as different heavy metals have different eco-toxicities and different concentrations. This improved approach used the maximum concentration of heavy metals that plays a key role in the assessment, as well as the eco-toxicity of all metals presented. Therefore, a more integrated assessment result was obtained. The improved Geo-Accumulation Index(IGAI)approach was employed and validated for evaluating heavy metal pollution in the sediments of the Chaobei river catchment(a river branch of Danjiangkou reservoir basin). That IGAI approach avoided the problem of averaging the heavy pollution points used by conventional GAI. It could effectively express the serious pollution condition of Hg at individual points. The results of the pollution ranking sequence of different heavy metals could systematically reflect the pollution status at the catchment. In assessing the composite pollution of heavy metals, the IGAI approach produced similar results as the Potential Eco-Hazard Index method, but with much less deviation caused by using uncorrected heavy metal toxicity coefficients as in the previous study.更多还原