洱海底泥重金属污染及富营养化的特征分析与评价

Analysis and Evaluation of Heavy Metal Pollution and Eutrophication of Sediment in Erhai Lake

为了解云南省洱海底泥重金属分布状况和污染程度,在洱海湖区13个采样点共采集到11组底泥样品,采用氢化物发生-原子荧光分光光度法和火焰原子吸收分光光度法测定8种重金属(Mg、Mn、As、Hg、Cd、Pb、Zn、Cu)的含量,分析其在洱海湖区的分布特征与含量水平,并采用地积累指数法和潜在生态风险指数法对底泥重金属污染程度及所造成的潜在生态危害进行评估,同时测定了洱海底泥有机碳、总氮和总磷等环境因子指标.结果表明,洱海底泥不同重金属的含量存在较大差异,呈现为Mn>Mg>Pb>Zn>Cu>As>Cd>Hg的顺序.虽然底泥中检出的Hg和Cd含量相较其他重金属元素低,但两者含量均高于云南省土壤背景值,其中Hg和Cd的最高含量分别是云南省土壤背景值的5.79、4.94倍.底泥中重金属污染程度由重到轻依次为Hg>Cd>Pb>Zn>Cu>As.重金属Hg和Cd的污染程度最高,造成的潜在生态危害水平最大,下关镇、小关邑、南湖心等下游地区为主要污染区域,总体呈现南部>北部的趋势.此外,洱海底泥富营养化程度相对较高,但明显低于云南省滇池这个底泥污染严重的湖泊.

To understand the distribution and pollution degree of heavy metals in the sediment of Erhai Lake in Yunnan Province,11 groups of sediment samples were collected from 13 sampling sites in Erhai Lake.The contents of 8 heavy metals(Mg,Mn,As,Hg,Cd,Pb,Zn and Cu)were determined by hydride generation-atomic fluorescence spectrophotometry and flame atomic absorption spectrophotometry.The distribution characteristics and content level of heavy metals in Erhai Lake were analyzed.The geo-accumulation index method and potential ecological risk index method were used to evaluate the heavy metal pollution degree and the potential ecological harm caused by the sediment.At the same time,the environmental factors such as TOC,TN and TP in the sediment were determined.The results showed that the contents of different heavy metals in the sediment of Erhai Lake varied greatly,in the order of Mn>Mg>Pb>Zn>Cu>As>Cd>Hg.Although the contents of Hg and Cd in the sediment were lower than those of other heavy metals,the contents of both were higher than the soil background values in Yunnan Province,and the highest contents of Hg and Cd were 5.79 and 4.94 times of the soil background values in Yunnan Province,respectively.The degree of heavy metal pollution in the sediments ranged from high to low as Hg>Cd>Pb>Zn>Cu>As.The pollution levels of heavy metals Hg and Cd were the highest,leading to the greatest potential ecological hazards.Xiaguan town,Xiaoguanyi,Nanhuxin and other downstream areas are the main pollution areas,showing an overall trend of the southern part being more polluted than the northern part.In addition,the eutrophication level of the sediments in Erhai Lake was relatively high but significantly lower than that of Dianchi Lake in Yunnan Province,which is a lake with severe sediment pollution.