The Heavy Metal Pollution And Characteristics Of Migrants In The Ecosysterm Of Lake Caohai In Weining District Of Guizhou Province

Lake Caohai in Weining District of Guizhou Province is a National Nature Reserve, which was affected by zinc smelting activities and sewage from the surrounding area for a long time, and it is suffering from serious ecological risks. Concentrations and distributions of Zn, Pb, Cd, Ni in sediments in Lake Caohai were analyzed in this research based on atomic absorption and ICP-MS, and in the meanwhile, its influence on zoobenthos community and acquatics was analyzed. The results indicated that,(1) Concentrations of Zn, Pb, Cd in surface sediments exceeded the Canadian Environmental Quality Guidelines, this may due to the historical zinc melting activities. But concentrations of heavy metals in surface water and pore water of Lake Caohai were in normal range compared to the National Quality Standard for Surface Water(grade I), which indicated the influence of heavy metals concentration form contaminated sediments to pore water was limited. Concentrations of Zn, Pb, Cd, in the middle and the entrance area of the lake are higher than other sampling sites, and the coefficient between the content of Zn, Pb, Cd, and organic materials was positive in significant level(r=0.837, p?0.01; r=0.785, p?0.01;r=0.780, p?0.01), which means the content of organic materials played an important role in transformation and deposition of these heavy metals. Concentrations of Zn, Pb, Cd were rising and accumulating from 10 cm to the top of sediment profile in the middle of Lake Caohai, which could match with the history of zinc smelting activities in recent decades. Ni had opposite correlation with the other three researched heavy metals no matter in surface sediment or in sediment profile, probably because Ni came from natural background.(2) The contents of Pb and Cd in aquatics in Lake Caohai were exceeded the hygienic standard for fresh and frozen marine products of animal origin, and the pollution levels of Pb was higher than Cd. The pollution levels of zoobenthos are higher than other kinds of fish samples, which indicated that the high concentration of heavy metals in sediments of Lake Caohai had already influenced the aquatics. The survey of zoobenthos community structure indicates that the surrounding sampling sites had more species and higher density of zoobenthos than it was in the central area, with the comparision result of the heavy metals content of Procambarus clarkia in the central area and the surrounding area, and the correlation coefficient of the content of Zn, Pb, Ni between Procambarus clarkia and surface sediment was r=0.945, 0.837, 0.860, respectively,we could speculated that it was because the high content of heavy metals in Lake Caohai than the surrounding sites.(3) Different kinds of macrophytes have different enrichment ability to veriety heavy metals, same kind ofmacrophytes have different enrichment ability to veriety heavy metals, too. Although the content of heavy metals of macrophytes in Lake Caohai was more than other realtively no pollution area, but it was still lower than the content of heavy metals in sediments, which indicated that the mobility/bio-availability of heavy metals in sediments was quite low.