环境治理对红枫湖水生食物链中汞积累的影响

Effect of Environmental Improvement on the Accumulation of Mercury in the Aquatic Food Chain of Hongfeng Reservoir

于2015年以贵州省贵阳市饮用水源地红枫湖的水生食物链作为研究对象,通过测定不同营养级生物的汞含量及稳定碳氮同位素,并结合2007年红枫湖的数据,对比红枫湖水体的汞含量及水生食物链中的汞含量、食物链长度及生物放大率的变化。结果发现:相比于2007年,湖水中的总汞浓度降低了40%,但鱼体总汞和甲基汞含量分别增加了140%与210%,甲基汞在总汞中占的比例平均增加了18%。食物链长度增加一级,汞的生物放大率降低。可能的原因是:2008年政府对红枫湖进行综合治理后,水体富营养化程度降低,湖中食物链结构发生改变,鱼类生长速度减慢,使得鱼体内汞的生物稀释作用减弱,鱼体的汞含量相对升高。同时,高强度捕捞,使得鱼样个体普遍偏小,导致生物放大率较低。

In this study, we analyzed the total mercury （THg）, methylmercury （MeHg）, stable carbon and nitrogen isotopes （δ^13C and δ^15N） for different trophic levels organisms from Hongfeng Reservoir （HF） in 2015. Combining with previous data of HF in 2007, we compared the variations about the mercury concentrations in organisms, food chain length, and the bio-magnification in aquatic food chain in HF. The results showed that concentrations of THg and MeHg in fishes increased by 140% and 210%, respectively. The ratio of MeHg to THg increased by 18%, and the food chain length increased by one trophic level, while the bio-magnification rate decreased in food chain. There are some possible reasons that, as a result of a comprehensively pollution control by the local government,the eutrophication degree in water body decreased significantly in Hongfeng Reservoir since 2008, which changed plankton community, abundance and fish growth rate. Therefore, mercury concentration in fish increased slightly and low biomagnification due to a weak biodilution effect and small size by high-intensity fishing in HF.