洞庭湖典型水域重金属含量的空间分布与来源解析

Spatial Distribution Characteristics and Source Analysis of Heavy Metals in Typical Water Areas of Dongting Lake

2016年12月选取洞庭湖及其8个入湖口为研究区域,对上覆水、悬浮物和沉积物中铜(Cu)、锌(Zn)、铅(Pb)、镉(Cd)、镍(Ni)、铬(Cr)、锰(Mn)、钴(Co)、钒(V)和铊(Tl)进行了采样分析,研究了悬浮物和沉积物中重金属含量的空间分布特征,并采用相关性分析和主成分分析对其来源进行了解析。结果表明,上覆水、悬浮物和沉积物中重金属含量分别在0.02-180μg·L^(-1)、0.01-486μg·L^(-1)和0.10-1451 mg·kg^(-1)之间。研究期内虽上覆水平均水质优于地表水Ⅲ类,但6个断面出现Mn元素超标,断面超标率达30%。悬浮物中大部分元素平均含量为背景值的23.4-154倍,Cr、Cd和Mn富集程度较高。沉积物中Cd为主要污染物,平均含量为背景值的64.2倍。入湖口悬浮物中松滋口(S5)的Cu、资江(S2)的Cd、新墙河(S7)的Zn、Pb、Mn和Tl以及澧水(S4)的Ni、Co和V含量最高;湖体悬浮物中大部分元素平均含量呈东洞庭湖>南洞庭湖>西洞庭湖分布,元素Mn和Co有所不同。入湖口沉积物中长江来水(S5)的V、湘江(S1)的Cu、Zn、Pb、Cd、Ni、Cr、Mn、Co和Tl含量最高;湖体沉积物中大部分元素平均含量呈南洞庭湖>西洞庭湖>东洞庭湖分布,元素Pb有所不同。悬浮物和沉积物中重金属含量空间分布存在不一致性。源解析表明,洞庭湖典型水域重金属主要来源于四水、汨罗江、新墙河和松滋河流域采矿、冶炼和造纸等行业含重金属的废水排放,在东洞庭湖和南洞庭湖部分区域则叠加了船舶采砂作业的影响。此外,Mn元素在鹿角、南嘴和蒋家嘴断面受码头污染的影响;Cu、Zn、Pb、Cr和V元素在东洞庭湖受农业面源污染的影响;Pb、Zn、Cd、Tl和Co元素受城市生活污水排放的影响;Cd、Ni、Cr和Co元素受流域风化等自然因素的影响。

Dongting Lake and its eight inlets were selected as research areas to analyze the spatial distribution characteristics of Cu,Zn,Pb,Cd,Ni,Cr,Mn,Co,V,and Tl in the overlying water,suspended solids,and sediments in December 2016.In addition,the sources of heavy metals were analyzed using correlation and principal component analyses.The results showed that the heavy metal contents in the overlying water,suspended matter,and sediment ranged from 0.02 to 180μg·L^(-1),0.01 to 486μg·L^(-1) and 0.10 to 1451mg·kg^(-1),respectively.Although the average water quality of the overlying water was better than the Class Ⅲ environmental quality standard for surface water,the Mn content was higher than the Class Ⅲ environmental quality standard for surface water in six sections,and the proportion of overlying water exceeded the standard by 30%.The average content of most elements in the suspended matter was 23.4–154 times that of the background value,and the enrichment of Cr,Cd,and Mn was high.Cd was the main pollution in sediment,and the average content of Cd was 64.2 times of background value.Among the suspended solids entering the lake estuary,content of Cu in Songzikou (S5),Cd in Zijiang (S2),Zn,Pb,Mn and Tl in Xinqiang River (S7) and Ni,Co and V in Lishui (S4) were the highest.The average contents of heavy metals (except Mn and Co) in suspended solids were in the order of East Dongting Lake>South Dongting Lake>West Dongting Lake.The Cu,Zn,Pb,Cd,Ni,Cr,Mn,Co and Tl contents in the sediments of the Xiangjiing River (S1) and V from the Changjiang River (S5) were the highest.The average contents of heavy metals (except Pb)in the sediments were from the South Dongting Lake,West Dongting Lake,and East Dongting Lake.This study showed that the spatial distribution of heavy metals,such as Cu,in suspended solids and sediments was inconsistent.Source analysis showed that heavy metals in typical waters of Dongting Lake were mainly from mining,smelting,and papermaking wastewater in the Xiangjiang,Lishui,Zijiang,Yuanjiang,Miluo,Xinqiang,and Songzi River basins.The influence of sand excavation was superimposed on some areas of the East and South Dongting Lakes.In addition,contents of Mn in Lujiao,Nanzui and Jiangjiazui were affected by the pollution of wharves,contents of Cu,Zn,Pb,Cr and V in East Dongting Lake were affected by pollution of agricultural non-point source pollution,contents of Pb,Zn,Cd,Tl and Co were affected by urban domestic sewage discharge,and contents of Cd,Ni,Cr and Co were affected by natural factors such as weathering in the basin.