滇池湖体及其主要入湖河流沉积物中重金属生态风险的时空分布特征评价

为了表征滇池流域20多年来的底泥重金属生态风险,用Hakanson潜在生态危害指数评价法和Muller地积累指数法对滇池湖体及其5条主要入湖河流的重金属污染进行时空特征评价。就空间分析,得出以下结论:(1)对于滇池湖体,两种评价方法结果一致,即草海污染程度大于外海,并且滇池湖体中污染程度最高的重金属为Cd;(2)对于滇池主要入湖河流,两种方法得到一致的污染程度排序:运粮河>新河>船房河>盘龙江>大清河;(3)关于入湖河流中污染程度最高的重金属,潜在生态危害指数法评价为:船房河、大清河、盘龙江是重金属Hg风险最高,而运粮河和新河是重金属Cd的风险最高。而通过地累积指数评价法得到,5条河流均是重金属Cd的污染程度最高。评价结果的差异,主要是由于潜在生态危害指数法较之地累积指数法还另外考虑了污染因子的毒性特征而产生的。就时间变化分析,以1989年和2005年为例,除了重金属Cr有上升趋势,其余金属总体上呈现随时间下降的趋势,说明滇池流域20多年来的污染治理工作取得了一定的成效。

Assessment on Spatial and Temporal Distribution Characteristics of Ecological Risk of Heavy Metals in Sediments of Lake Dianchi and Its Major Tributaries

In order to characterize the ecological risk of the heavy metals in the sediments of Lake Dianchi watershed in the last twenty years,Hakanson's Potential Ecological Risk Index Method and Muller's Index of Geoaccumulation Method were used to assess Lake Dianchi and its major tributaries from both spatial and temporal perspectives.From the spatial perspective,the results were as follows.(1) For Lake Dianchi,the two assessment methods came to the same conclusion that the pollution of Lake Caohai was more serious than that of Lake Waihai,and Cd was the biggest polluter in Lake Dianchi.(2) For the five tributaries,the two methods came to the same sequence of pollution degree: Yunliang River > Xin River > Chuanfang River > Panlong River > Daqing River.(3) As for the biggest polluter of each river,when using Hakanson's method,it came to Hg for Chuanfang River,Daqing River and Panlong River,and Cd for the other two rivers.However,when using Muller's method the result was Cd for all.This difference may come from Hakanson's method,taking toxicological characterization of the metals into consideration.From the temporal perspective,when comparing 2005 with 1989,all metals showed a declining trend except for Cr,which indicated that the water pollution control management for Lake Dianchi and its tributaries was somewhat effective in the last twenty years.