近150年呼伦湖重金属污染历史及潜在生态风险

Pollution history and potential ecological risk assessment of heavy metals in core sediments in Hulun Lake during the past 150 years

针对呼伦湖演化历史研究相对不足的现状,于呼伦湖中心采集柱状岩芯沉积物样品78个,测定分析了沉积物中Cr、Mn、Co、Cu、Zn、Cd、As、Pb等8种重金属元素的垂向分布特征。结合210Pb测年数据和粘土含量,采用Pearson相关分析和主成分分析法,判别不同沉积阶段重金属元素的可能来源,并对其进行潜在生态风险评价。结果表明:1865—1973年各种金属元素含量相对较低,以自然输入源为主,人类活动对湖泊影响微弱;1973—1992年重金属元素含量均呈现增加趋势,主要以工矿业和农业污水、交通源等人类活动释放源为主;1992年后除As、Pb外均出现下降趋势,受自然保护区建立的影响,自然来源为首要源,但仍存在农业污水、交通源和采矿业的人为源。生态风险评价结果表明,单元素污染系数Cd>As>Pb>Cu>Co>Cr>Mn>Zn,Cd潜在生态风险超强,As在1992年以后为中等潜在生态风险,其他几种元素均属于轻微生态风险,多种污染物的潜在生态风险近年处于较高水平,Cd和As是主要生态风险贡献因子。呼伦湖重金属污染历史能够较好地指示人类活动,自然保护区的建立对治理污染起到了一定的积极作用,但Cd、As污染应予以重视,呼伦湖的环境保护及治理有待进一步加强。

Understanding the evolution process of the historical environment is the foundation of lake ecosystem restoration. Heavy metals of Cr, Mn, Co, Cu, Zn, Cd, As, and Pb, fine particle sizes of clay, as well as210 Pb dating data were measured in the central core sediments of Hulun Lake, due to the scarce research of its historical pollution characteristics. The vertical distribution, possible sources, and potential ecological risk assessment of heavy metals were investigated using Pearson correlation analysis and principal component analysis. Results showed that the contents of all heavy metals were relatively low, and were derived from a natural input source from 1865—1973. Heavy metal concentrations increased from 1973—1992, while after 1994, all metals except for As and Pb showed a decreasing tendency with regard to the sources of natural and anthropogenic input. Single element pollution coefficients were in the order of Cd〉As〉Pb〉 Cu〉 Co〉 Cr 〉Mn〉 Zn, with the major and harmful ecological risk factors being mainly from Cd and As. The pollution coefficient of As ranged from 30~60 after 1992, which indicated a medium potential ecological risk, while other metals were minor ecological hazards. Therefore, heavy metals in the core sediments of Hulun Lake had potential risks, and appropriate attention must be paid to the pollution control of the lake. The current study can provide reference and basic data for the improvement of the ecological environment in Hulun Lake.