南方某城市典型供水水库沉积物重金属分布特征及生态风险

Distribution characteristics and ecological risk of heavy metals in sediments of a typical water supply reservoir in a southern city

水库在城市饮用水供给中发挥着举足轻重的作用,以南方城市某典型供水水库为研究对象,研究了8种重金属的水平及垂直分布特征,分析并评价了重金属的来源、污染程度及其潜在生态危害。数据显示:Hg、As、Pb、Cu、Ni、Cr、Mn、Zn的含量范围分别为0.019—0.128 mg·kg^(-1),0.86—4.81 mg·kg^(-1),51.2—83.2 mg·kg^(-1),2.3—22.8 mg·kg^(-1),3.2—98.3 mg·kg^(-1),5.2—121.6 mg·kg^(-1),233—706 mg·kg^(-1),33.7—241.7 mg·kg^(-1),Pb、Mn、Zn 3种元素全库沉积物平均含量超过广东省土壤元素背景值,Cr、Ni在库尾部大量蓄积。垂直方向上大部分金属的含量随着沉积物的堆积而增加。单因子污染指数、地累积指数均显示水库沉积物受到Mn、Pb、Zn的轻度污染,潜在生态风险指数显示水库目前处于较低的生态风险。相关性分析显示Cr、Ni极显著相关(P<0.01),主成分分析显示库区重金属主要来源于工农业生产、交通运输以及库区西北部的水土流失。总体来说,虽然整体库区处于轻微污染状态,但库尾部的污染风险不容忽视。在水库的管理过程中,库区周围的水土流失应引起有关部门的重视,应提高水库周围的植被覆盖度,并减少人类活动对水库的干扰。

Reservoirs play a vital role in supplying water for cities.Taking a typical water supply reservoir in a southern city as the research object,this paper researched the content and the vertical distribution characteristics of eight heavy metals in reservoir sediments.It also analyzed and evaluated the origins of those metals,the pollution degree,as well as the potential ecological risk.The data showed that the contents of Hg,As,Pb,Cu,Ni,Cr,Mn,and Zn in the sediments were 0.019-0.128 mg·kg^(-1),0.86-4.81 mg·kg^(-1),51.2-83.2 mg·kg^(-1),2.3-22.8 mg·kg^(-1),3.2-98.3 mg·kg^(-1),5.2-121.6 mg·kg^(-1),233-706 mg·kg^(-1),and 33.7-241.7 mg·kg^(-1).According to the data,the average content of Pb,Mn and Zn in the sediments of the reservoir exceeded the background values in Guangdong Province.And there were lots of accumulation of Cr and Ni at the tail of the reservoir.Vertically,the content of most metals increased as the accumulation of the sediments increased.The contamination factor and the geoaccumulation index both showed that the sediments of the reservoir were slightly polluted by Mn,Pb,and Zn.The potential ecological risk index showed that the reservoir was at a relatively low risk.The correlation analysis showed that Cr and Ni were significantly correlated(P<0.01).The principal component analysis showed that the heavy metals in the reservoir were mainly generated from the production of both industry and agriculture,the transportation,and the soil erosion in the northwest of the reservoir.All in all,though the whole reservoir is polluted slightly,the pollution risk in the tail area of the reservoir should not be neglected.While managing the reservoir,the soil erosion around the reservoir should be paid more attention.Moreover,the coverage of vegetation around the reservoir should be increased,and the interference of human activities on the reservoir should be reduced as well.