中国三个不同富营养化湖泊沉积物中Cu、Zn赋存特征及其与营养盐的相关性分析

The Chemical speciation of Copper and Zinc and their relationship with nutrients in the sediments from three eutrophic lakes in China

对太湖、南四湖、白洋淀三个不同富营养化湖泊沉积物进行采样，采用Tessier连续提取法，测定了3个湖泊表层沉积物中Cu、Zn两种重金属的赋存形态，并初步探讨了重金属各形态与沉积物及上覆水中营养盐的相关关系。结果表明，沉积物中重金属总量以白洋淀最高，太湖最低，但重金属污染程度为太湖＆gt;南四湖＆gt;白洋淀，太湖Cu污染指数为1.34~1.6，白洋淀Cu污染指数仅为0.79~1.17。沉积物中重金属赋存形态Cu主要以残渣态和有机质结合态为主（二者之和占73%以上）， Zn则以残渣态和Fe-Mn氧化态占优（二者之和比例达83%以上），含量最少的均为可交换态。不同湖泊沉积物重金属赋存形态差异较大，太湖残渣态重金属占总量的比例最小（Cu为43%~56%，Zn为49%~63%），南四湖残渣态占的比例最大（Cu为59%~82%、Zn为64%~77%）；可交换态比重在太湖中最高（Cu占3.2%~5.6%，Zn为1.3%~1.5%），在南四湖中最低（Cu为1.1%~2.9%，Zn未检出）。从“非稳定态”重金属（除残渣态外的四种形态之和）所占比例看，相较其它两个湖泊，太湖沉积物中重金属污染人为输入的活性态占较大比重，具有较高的二次释放风险。相关性分析得出，重金属Cu的可交换态与上覆水中总氮及总磷之间存在着极显著的正相关关系，碳酸盐结合态Cu与沉积物中营养盐呈现出显著的负相关性，说明水体的富营养化程度加剧可能会增强沉积物中Cu向水体释放的风险。

The chemical speciation of heavy metal Cu and Zn in the surface sediments of Tai Lake, Nansi Lake and Baiyangdian Lake was measured by Tessier sequential extraction methods. The relationship between heavy metal fractions and nutrients in sediments and overlying water was also discussed. Experimental results showed that the highest total contents of heavy metals＆amp;nbsp;occurred in Baiyangdian Lake and the lowest occurred in Tai Lake. The order of severities of heavy metal pollution were Tai Lake＆gt;Nansi Lake＆gt;Baiyangdian Lake. Pollution index for Cu was 1.34~1.6 in Tai Lake, and was 0.79~1.17 in Baiyangdian Lake. In sediments, Cu existed mainly in the form of residual and organic-bound fractions, accounting for more than 73%of the total content. The dominated fractions of Zn were the residual fraction and the Fe/Mn oxide fraction, accounting for more than 83%of the total content. The exchangeable fraction was the lowest for both Cu and Zn. The occurrence characteristics of heavy metals from different lake sediments have diversity. For the three lakes, the proportion of residual fraction in the Tai Lake was the lowest, with the percentage of residual Cu was 43~56%and the percentage of residual Zn was 49~63%. The proportion of residual fraction was the highest in the Nansi Lake, with the proportion of residual Cu and Zn were 59~82% and 64~77% respectively. The proportion of exchangeable fraction was the highest in the Tai Lake, with the proportion of exchangeable Cu was 3.2~5.6%and the proportion of exchangeable Zn was 1.3~1.5%. The proportion of exchangeable fraction was the lowest in the Nansi Lake, with the proportion of exchangeable Cu was 1.1~2.9%, and exchangeable Zn was undetected. This studies also showed the total“labile”fraction （the sum of four forms of heavy metal except residual fraction） extracted from heavy metals was the highest in Tai Lake, which might bring more serious ecological risk to the water ecological system, and should be paid more attention to. According to correlation analysis, the exchangeable fraction of Cu was significantly correlated to TP and TN in overlying water, and there was a negative correlation between the carbonate-bound Cu and nutrients in sediments, indicating that eutrophic level of water might have an important influence on the release of Cu. The aggravation of eutrophication might enhance the risk of Cu release from the sediments to water.