Spatial Distribution Difference of Different Forms of Nitrogen and Phosphorus in Caohai Lake in Dianchi Lake during Low Water Period

Based on the analysis results of TN,TP,DTN,DTP and cyanobacteria density at 16 stations in Caohai of Dianchi Lake in November 2016,the spatial distribution characteristics of different forms of nitrogen and phosphorus,cyanobacteria density,eutrophication characteristics of the Caohaiwaterbody were studied as well as the correlation between these indicators and the similarity of water environment at each monitoring point. The results showed that the average TN concentration was 3. 54 mg/L,exceeding Class V Standard of Surface Water,and the average TP concentration was 0. 096 mg/L,which met Class IV Standard. DTN and PP were the main forms of nitrogen and phosphorus. The spatial distribution of TP and TN concentration decreased gradually from north to South and then increased. The spatial distribution of cyanobacteria density increased gradually from north to south along with the flow direction,and the spatial distribution of DTN and DTP concentration decreased gradually from north to south along with the flow direction. K-means cluster analysis was used to divide the sampling points into three groups. The density of cyanobacteria was significantly correlated with TN and DTP. Phosphorus might be a limiting nutrient.