Pollution status of organochlorines and heavy metals in surface sediment of southern Lake Taihu

Abstract

对南太湖水域表层沉积物中的19种有机氯化合物及6种重金属的含量、分布及其生态风险进行了研究和评价.所测样品中有机氯农药(OCPs)和多氯联苯(PCBs)含量范围分别为0.51-4.98、1.49-15.15ng/g(dw), 与国内其它水域沉积物中OCPs、PCBs的含量相比处于较低水平.OCPs中的主要污染物是α-六六六, PCBs中含量最高的是八氯联苯CB194和三氯联苯CB28.所采沉积物样品中6种重金属的含量水平分别为Cu:14.4-79.7mg/kg、Zn:69.3-214mg/kg、Cr:65.0-99.5mg/kg、Ni:24.8-48.7mg/kg、Pb:12.3-39.2mg/kg及Cd:0.015-0.563mg/kg.用风险评估低值(ERL)和风险评估中值(ERM)对有机氯化合物进行了生态风险效应评价, 发现所测沉积物中滴滴涕(DDTs)的值90%处于ERL值以下, γ-六六六与PCBs的值100%小于ERL.利用潜在生态危害指数法对研究区沉积物进行生态危害评价, 结果表明, 沉积物中重金属的生态危害程度都较小, 单项生态危害指数相对较高的重金属是Cd, 各采样点中XMK-0重金属的潜在生态危害相对较高.总体而言, 南太湖表层沉积物中上述有机氯化合物和重金属的含量水平较低, 未对生态构成严重威胁.但考虑到这两类污染物的生物积累性和毒性, 仍需注意预防此类污染。;Concentration and distribution of 19 organochlorines and 6 heavy metals in the surface sediment of southern Lake Taihu were studied and the relevant risk assessment was carried out.The results showed the concentrations of organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) detected ranged from 0.51-4.98ng/g(dw) and 1.49-15.15ng/g(dw),respec-tively,which was at a low contamination level compared to other fresh water sediments in China.The congener of α-hexachlorocy-clohexane (α-HCH) was the dominant pollutant among OCPs and CB194,and CB28 were the dominant PCBs.The concentration rangesof Cu,Zn,Cr,Ni,Pb and Cd in the surface sediments of southern Lake Taihu were 14.4-79.7mg/kg,69.3-214mg/kg,65.0-99.5mg/kg,24.8-48.7mg/kg,12.3-39.2mg/kg and 0.015-0.563mg/kg,respectively.Effects range low (ERL) and effects range median (ERM) were used to evaluate the ecological risk of organochlorines.It was found that 90% of the sampling sites had a dichlorodiphenyltrichloroethanes (DDTs) value lower than the ERL,and the γ-HCH and PCBs values of all sites were lower than the ERL.The risk assessment was completed on heavy metals in sediments by using the potential ecological risk index (RI).The results indicated that the overall ecological risk caused by heavy metals was low.The potential ecological risk index of Cd was relatively higher,and the RIs of several heavy metals in XMK-0 were relatively higher than that in other sites.Al-though the concentration levels of the above organochlroine and heavy metal pollutants in the surface sediments of southern Lake Taihu were low and no serious threat has been observed to the ecological system,the prevention to these contaminations should not be ignored for their accumulative effect and toxicity in the environment.