Studying On Eutrophication And Blue-green Algae Bloom Of Urban Lakes In Beijing

Chang River, important part of Beijing city water system and waterway of the source water, is being confronted with the menace of the eutrophication. The community and density of phytoplanton determined the elementary productivity of Chang River , based on the research from 2003 to 2004.Two hundreds and four species were identified ,which belongs to 8 division and 87 genera. The structure of phytoplankton community was of Cyanophyta-Chlorophyta type. The cell density of phytoplankton was 41150×10~4/L,increased by 62.88 times from 1987. Microcysis, Oscillatoria, Scenedesmus, Chlorella, Cyclotella and Melosira ,the eutorphicational or hyper-eutrophicational indicator species, were the dominant species of phytoplanton in Chang River. Water bloom with prior blue green algae occurs every summer,the pollution state of urban lakes in Beijing is eutrophic or serious eutrophic.Chang River water body has low transparency (0.52m) and high level of nutrient salts (with TN 1.667mg/L,TP 0.144mg/L). TSI_M of five targets(TN, TP, CODmn, SD, chla) are form 54 to 88,whicn showed eutrphication of Chang River. According to GB3838-2002,the state standard of water environmental quality for surface water ,the water quality in the inlet of Zhongnanhai, Zhonghak Zanhai and outlet of Tongzi River was Grade IV, the water quality in inlet of Beihak Houhak Qianhak Maizhongqiao was Grade V and the water quality in Gaoliangqiao, Xihai, Songlinzha was exceed Grade V.Combined with the experiment of algae growth potential, the influence of various environmental factors on eutrophication in Chang River were investigated and the main controlling factors of eutrophication in the lake identified.According to the preliminary investigation and results of experiment , the situation of eutrphicational waterbody and the reasons of Microcystis bloom are analyzed .The principal factors of eutrophication in Chang river are (l)the pollution of nutritive material are serious;(2)owing to increasingly shortage of the water resources ,the ecological environment water consumption is low;(3)the lake ecological system ,food chain and rood net have seriously destroyed to such an exetent that loss of biodiversity came into being.The paper provides references for the controal of eutrophication and pollution of water body in Biejing urban zone.