摘要
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.