太湖湖区“黑水团”成因及危害分析

Cause and impact analysis of black water cluster in Taihu Lake

跟踪观测太湖湖区"黑水团"形成过程,在室内对蓝藻死亡过程进行模拟试验。结果表明:①"黑水团"形成过程中,溶解氧迅速降低,最低值可为零,氨氮、化学需氧量均高于常值,发生剧烈的藻体分解矿化过程;②2008年太湖竺山湖湾及附近出现的"黑水团"与2007年引发无锡自来水供水危机的贡湖水源地"黑水团"特征基本一致;③蓝藻大规模聚集并堆积、死亡,在温度较高、风力较小、气压较低、复氧能力弱的条件下,蓝藻死亡后分解释放产生挥发性硫化物、二甲基三硫等硫醚类物质,硫化物与底泥中的重金属化合而形成致黑物质,在吸附凝聚过程中受湖泊风浪及水动力条件影响,悬浮而成"黑水团"。

The formation of black water cluster was observed through field investigation and indoor simulation experiments on the course of death and decomposition of blue algae.The results showed the following：（1） During formation of black water cluster,the DO content reduced rapidly,the lowest value was nearly 0 mg/L,the contents of NH＋4-N,COD were greater than the normal values,and the process of the decomposition and mineralization of the dead blue algae occurred intensively.（2） The characteristics of black water cluster in the bay of Zhushanhu Lake in 2008 were in line with those in the Gonghu Lake in 2007.（3） A large number of blue algae were accumulating and dying under conditions of high water temperature,slow wind,low air pressure,and weak reoxygenation capacity.Thioethers substances like volatile sulfide and dimethyltrisulfide were released after the decomposition of dead blue algae,the sulphide and heavy metal from sediments were combined chemically,and colored matter was formed.Furthermore,the phenomenon of black water cluster occurred during the process of agglomeration in response to wind,waves,and hydrodynamic conditions.