摘要
流域上游矿山开采和重金属冶炼等人类活动的影响使得洞庭湖水域重金属污染问题严重,制约了该区域社会经济的可持续发展.针对近100年来洞庭湖重金属污染不明的现状,本研究以东洞庭湖为研究对象,结合放射性核素210Pb定年技术,分析沉积物中7种重金属(As、Cd、Cr、Cu、Mn、Pb、Zn)的时空分布特征,并采用主成分分析方法,解析重金属污染物的来源.研究结果表明,近100年来东洞庭湖存在As、Cd、Pb、Cu、Zn污染情况.其中As的平均含量较高,在东洞庭湖自然保护区(DDTH)下层均值达184.05 mg·kg-1;除鹿角(LJ)下层,Mn元素平均含量均高于洞庭湖背景值,对其需引起重视.重金属含量在垂向上变幅较大,且沉积过程大体可分为3个阶段(1937年前;1937-1978年;1978-2020年).源解析结果表明,早期的东洞庭湖沉积物重金属污染主要来自"采矿源";中期主要受到"工业源"、"农业源"及"交通源"的共同影响;而近期为多种污染源共同支配形成的"混合源".本研究结果进一步明确了湖泊沉积物重金属的空间分布特征以及污染历史的演化过程,为湖泊环境管理提供理论支撑.
Abstract
The heavy metal pollution in Dongting Lake is serious due to the intensive human activities such as mining and heavy metal smelting in the upper reaches,which restricts the sustainable development of the region's society and economy.For the uncertain situation of the heavy metal pollution in Dongting Lakre over the past century,this study selected East Dongting Lake as the research object.The spatial and temporal distributions of seven heavy metals(As,Cd,Cr,Cu,Mn,Pb,and Zn)in sediments were analyzed with the help of 210Pb dating technique,and their source was identified by principal component analysis.The results showed that the East Dongting Lake was contaminated by As,Cd,Pb,Cu and Zn in the past 100 years.In DDTH(the nature reserve),the average content of As was relatively high with the value in the lower layer reaching 184.05 mg·kg-1.Except for the lower layer LJ(wharf),the average content of Mn in all the sites exceeded the background value,which needs more attention.The content of heavy metals showed obvious variation along the vertical direction,and the deposition process can be divided into three stages:before 1937,1937-1978,and 1978-2020.The source identification results showed that heavy metal pollution of sediments in East Dongting Lake was mainly from"mining sources"in the early period.In the middle period,it was mainly affected by the"industrial source","agricultural source"and"transportation source".In recent years,the"mixed source"formed the combined domination of the pollution sources.Our findings clarified the spatial distributions of heavy metals in lake sediments and their evolutionary processes of pollution history,and further provided theoretical support for lake environmental management.
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