抚仙湖沉积物重金属垂向分布及潜在生态风险评价

基于环境放射性核素210Pbex和137 Cs计年法确定抚仙湖北、中和南部三个沉积物柱芯的沉积年代,分析了各个柱芯近150年的重金属(Cr、Cu、Zn、As和Pb)的垂向分布特征,并用潜在生态风险指数法进行了潜在生态风险分析。结果表明,抚仙湖不同湖区沉积物重金属的垂向分布存在明显差异,其中Zn、As和Pb呈现整体向上增加的趋势,Cr和Cu分别呈现微波动变化和下降趋势。重金属元素之间相关性表明Zn、As和Pb具有较好的同源性,而Cr和Cu来源不同。重金属元素与营养盐TP之间呈较好的相关性,与TN和TOC则相关性较差或无相关性存在。潜在生态风险指数评价显示近150年来抚仙湖不同湖区沉积物重金属污染水平差异明显,其中北部和南部As是主要的生态风险贡献因子,而中部Cu是主要的生态风险贡献因子。抚仙湖中部和南部沉积物重金属总体处于中等生态风险,而北部沉积物重金属由中等上升为较高生态风险出现在20世纪90年代末期。

Vertical Distribution and Potential Ecological Risk Assessment of Heavy Metals in Sediment Cores of Lake Fuxian

Based on the results of radionuclides (²¹⁰Pb and ¹³⁷Cs) dating of sediment cores from Lake Fuxian, the vertical distribution and potential ecological risk assessment of heavy metals in the past 150 years were analyzed. The results showed that the vertical distribution of heavy metals significantly varied among different sediment cores of Lake Fuxian. There was an increasing trend for Zn, As and Pb over the past years, whereas there was a microwave trend for Cr and a downward trend for Cu. The relationship between different heavy metals and nutrients demonstrated that significant positive correlations were found among Zn, As and Pb, suggesting that they are from the same pollution source, while poor correlations between Cr and Cu indicated that they are from the different pollution sources. The contents of heavy metals were significantly positively correlated with TP concentrations, but there was a poor or no correlation with TN and TOC concentrations, respectively. The Hakanson potential ecological risk index was applied for assessing the status of sediments heavy metals enrichment and the results indicated that different pollution levels were found in different parts of Lake Fuxian, and as was As the main pollutant in the north and south of the lake, while Cu was the main pollutant in the middle of the lake. The comprehensive ecological risk index grades in sites FX0702 and FX0703 were within the moderate range, while the site FX0701 was from moderate to high in the late 1990s.