抚仙湖沉积物重金属时空变化与人为污染评价

The spatio-temporal variations of heavy metals in the sediment of Lake Fuxian and the contamination assessment

分析了抚仙湖表层沉积物及沉积短岩芯中10种金属元素含量,结合沉积年代学,定量研究了Cr、Cu、Ni、Pb、Zn的污染特征及时空变化规律;参考沉积物质量基准与潜在生态风险指数法探讨了表层沉积物重金属的潜在生态风险.结果表明,表层沉积物中重金属含量具有一定的空间差异性,近岸地区重金属含量总体上高于湖心区;Pb、Zn含量自1980s中期以来逐渐增加,而Cr、Cu、Ni含量呈下降趋势.重金属富集系数与聚类分析结果表明,抚仙湖沉积物主要重金属污染元素为Pb、Zn,污染开始于1980s中期,并逐渐加重.表层沉积物中Pb、Zn富集系数分别为1.6-4.1和1.4-2.6,已达到弱—中等污染程度,北部湖区污染程度略高于南部湖区;除此之外,北部湖区近岸区域Cr污染程度也略高于其他湖区.除了大气沉降来源之外,抚仙湖沉积物重金属污染还可能与入湖河流输入有关.单因子生态风险指数表明,表层沉积物中Cr、Cu、Ni、Pb、Zn具有较低的潜在生态风险;而综合潜在生态风险指数表明,表层沉积物中重金属具有中等程度的潜在生态风险,这与根据沉积物质量基准所获得的评价结果一致.

Concentrations of metals in the surface and core sediments of Lake Fuxian were determined. The spatio-temporal features of contaminations Cr,Cu,Ni,Pb and Zn were discussed,referencing to the enrichment factor method and the chronology of the sediment core. Potential eco-risks of the heavy metals in the surface sediments were discussed on base of combining the potential ecological risk index and sediment quality guideline assessments. The results showed that metal concentrations exhibited some spatial variations with general higher concentrations in the near shore area than in the lake center. Concentrations of Pb and Zn have increased typically since the mid-1980 s,whereas concentrations of Cr,Cu and Ni have decreased. Pb and Zn should be influenced by human contamination as indicated by the hierarchical analysis and the enrichment factors. The metal contamination began at the mid-1980 s and showed an increasing trend. Enrichment factors of Pb were between 1. 6-4. 1 and Zn between 1. 4-2. 6 in the surface sediments,reflecting minimal to moderate contamination levels,where the values were decreased from the north lake to the south. Moreover,the sediment in the near shore region of the north lake was also contaminated with Cr. The riverine input should be also a reason for the heavy metal contaminations in the sediment of Lake Fuxian,additionally the atmospheric deposition. Metals Cr,Cu,Ni,Pb and Zn in the surface sediments may have low potential eco-risk estimated on the potential ecological risk factor.However,the metals may be of a moderate potential eco-risk according to the potential ecological risk index,which is consitent with that from a baseline of the sediment quality assessment.