The Assessment of the Present Eutrophication Status and Characteristic Analysis of Xingkai Lake

Based on the analysis of the water quality monitoring data of Xingkai Lake in 2008, the eutrophic level of the water body was evaluated through a comprehensive trophic state index method. The results showed that the comprehensive trophic state index (CTSI) was 47.7 for Da Xingkai and 50.1 for Xiao Xingkai, which indicated that Da Xingkai is in a mesotrophic state and Xiao Xingkai in a light eutrophic state. The eutrophic characteristics were analyzed. There was a negative correlation between total nitrogen (TN) and chlorophyll-a (Chl-a) of Da Xingkai as well as Xiao Xingkai. The content of total phosphorus(TP) was high in Da Xingkai, more than 0.08 mg/L, which showed a negative correlation with Chl-a.While a low content of TP, lower than 0.1 mg/L, showed a positive correlation with Chl-a in Xiao Xingkai. The ratio of nitrogen and phosphorous density was between 2:1 and 4:1. Nitrogen was the limiting nutrient salt of eutrophication in Da Xingkai. The ratio of nitrogen and phosphorous density in Xiao Xingkai reached 14.1:1, within the optimum ratio range of algae growth.