蓝藻生消对巢湖沉积物重金属环境行为的影响

为探究蓝藻生消对巢湖表层沉积物重金属环境行为的影响,文章分析蓝藻休眠期和繁盛期沉积物中Cr、Co、Ni、Cu、Zn、As、Cd、Pb、Hg元素的含量水平、空间分布以及赋存形态的变化;采用地累计指数法和潜在生态风险指数法评估重金属污染情况和潜在生态风险。结果表明:蓝藻暴发后,每千克沉积物中Cd和Cr元素平均质量分别增加了0.70倍和0.35倍,其他元素质量有所下降,大部分元素质量空间分布向更加均衡的趋势转变;除Cd和Hg外,其他元素在蓝藻休眠期和繁盛期均以残渣态为主,占比为58%~97%;蓝藻繁盛期,元素各生物有效态占比发生不同程度的变化,但除Cd外其他元素生物有效态总量占比及残渣态占比变化不大,Cd迁移转化流动性最高;2个时期中,Cd和Hg环境风险均相对较高;蓝藻繁盛期重金属综合潜在生态风险有所增加,且单一元素环境风险趋向于空间均衡化。

In order to explore the impacts of cyanobacterial growth and decline on the environmental behaviour of heavy metals in surface sediments of Chaohu Lake, the content level, spatial and chemical form variation of Cr, Co, Ni, Cu, Zn, As, Cd, Pb and Hg in the sediments during the dormancy and bloom periods of cyanobacteria were analyzed. The pollution status and potential ecological risk of heavy metals in sediments were assessed by the geoaccumulation index method and the potential ecological risk index method. The results showed that the average contents of Cd and Cr per kilogram sediment increased by 0.70 and 0.35 times, respectively, while that of other elements decreased due to cyanobacteria outbreak. There was a shift towards a more even spatial distribution pattern for almost all studied elements during the bloom period. The elements were primarily present in residual form with the ratios of 58%-97% during the dormancy and bloom periods, except for Cd and Hg. During the bloom period, ratios of each bioavailable form of the elements changed in varying degrees, while total ratios of bioavailable forms and ratios of residual form barely changed, except for Cd, which showed the highest migration and mobility. Cd and Hg had higher environmental risks in two periods. The comprehensive potential ecological risks increased, while the individual element showed more balanced spatial distribution during the bloom period.