大冶湖及周边港渠水-沉积物重金属污染评价分析

Heavy-metal Pollution in Water/Sediment of Daye Lake and Neighboring Tributaries and Ditches:Evaluation and Analysis

该文以大冶湖流域中典型城市湖泊大冶湖、三里七湖和尹家湖及周边港渠为研究对象,共布设44个采样点位,分别采集水、表层沉积物样品和湖泊沉积柱样品,分析测试Cu、Zn、Se、As、Hg、Cd、Cr、Pb、Fe、Mn、Mo、Co、Be、Sb、Ni、Ba、V、Ti和Tl等含量水平,采用Pearson相关性分析法和因子分析法对湖泊及周边港渠水和表层沉积物中重金属污染特征,沉积柱中重金属空间分布特征进行分析,结合单因子评价、地累积污染指数和潜在生态危害风险指数评价湖泊及周边港渠水环境质量状况,沉积物中重金属累积污染程度和潜在生态危害风险。结果表明:湖泊及周边港渠中重金属浓度介于0.01~2960μg/L,湖泊及周边港渠水环境中部分点位Cd、Pb和Se浓度劣于地表水Ⅳ类(含Ⅳ类)水质标准,Fe、Mn、Tl浓度超出标准限值;表层沉积物重金属含量介于0.01~4432 mg/kg,较沉积物背景参考值均有不同程度的富集,沉积柱中重金属空间分布特征以中层富集型为主,峰值集中出现在深度12~18 cm层;湖泊及周边港渠表层沉积物中重金属地累积污染指数介于-2.5~3.4,Cu、Zn、Se、As、Hg、Cd等存在不同程度污染,其中三里七湖受重金属Cd污染最为严重;湖泊及周边港渠表层沉积物中重金属单因子潜在生态危害指数介于0.6~125235,综合潜在生态危害指数介于247~128967,不同点位中重金属单因子潜在生态危害指数差异较大,平均综合潜在生态危害风险为“很强”等级,主要是因Cu、As、Hg和Cd等单因子潜在生态危害指数贡献较大所致。大冶湖、三里七湖和尹家湖及周边港渠受工业排放源、城镇生活污染源和规模化畜禽养殖污染源影响严重,造成水环境和沉积物中金属富集严重,潜在生态危害风险很强,需要积极开展污染防治和加强生态环境保护。

This article is intended to evaluate the heavy-metal polluted urban lakes with respect to Daye Lake Watershed in Daye City whith embraces a group of waters like Daye Lake,Sanliqi Lake and Yinjia Lake as well as the neighboring tributaries and ditches.Within the watershed,monitoring was carried out involving 44 sampling points set up to collect water samples,top-sediment and lake sediment column samples,and testing and analysis of the content levels of heavy metals including Cu,Zn,Se,As,Hg,Cd,Cr,Pb,Fe,Mn,Mo,Co,Be,Sb,Ni,Ba,V,Ti,Tl and so on.Then,Pearson correlation analysis and factor analysis were adopted to analyze the pollution characteristics of heavy metals in the water and top-sediments of lakes and neighboring tributaries and ditches,as well as the spatial distributive characteristics of heavy metals in the sedimentary column;and subsequently the water environmental quality of the watershed was evaluated by combining single factor evalu-ation,as well as the cumulative pollution degree of heavy metals in sediments,and the potential ecological hazard risks were evaluated by local cumulative pollution index and potential ecological hazard risk index.The water monitoring results showed that the concentrations of heavy metals ranged from 0.01 to 2960μg/L with concentrations of Cd,Pb and Se not conforming to the Environmental Quality Standard for Surface Water(ref.to Class IV),and the concentrations of Fe,Mn,and Tl exceeding the limits of the Standard.In regard to top-sediments,heavy-metal concentration ranged 0.01~4432 mg/kg,and there existed enrichment of different degrees compared with the reference background values.The spatial distribution characteristics indicated that heavy metals were mainly enriched in the middle layer in the sedimentary columns,and the peak concentration appeared in the layers of depth(12~18 cm).The cumulative pollution index of heavy metals ranged from-2.5 to 3.4 in the top-sediments of lakes and neighboring tributaries and ditches,with the pollution mainly of Cu,Zn,Se,As,Hg,Cd and As,especially the serious pollution of Cd in Sanliqi Lake.As for the potential ecological hazard risks,the single factor potential ecological hazard index ranged from 0.6 to 125235,and the comprehensive potential ecological hazard index from 247 to 128967.In addition,the single factor potential ecological hazard index at different sampling points differed a lot,and the average comprehensive potential risk belonged to the strong level mainly owing to the great contribution of potential ecological hazard indexes of single factors such as As,Cu,As,Hg and Cd.In summary,the environment of Daye Lake,Sanliqi Lake,Yinjia Lake and the neighboring tributaries and ditches were severely affected by the industrial emission sources,municipal pollution sources,as well as by the pollution of the of-scale livestock and poultry breeding,thereby resulting in serious heavy-metal accumulation and enrichment in the environment of water and sediments,alongside with considerable potential ecological hazard risks.So,it is imperative to actively implement the pollution control and prevention,strengthening the ecoenvironmental conservation.