Abstract: The pollution characters, degree and correlations of the indexes in water and surface sediments from six lakes in Beijing were investigated to provide data for the eutrophication control of urban lakes. Results showed that nitrogen pollution of these urban lakes was serious, and the water total nitrogen (TN) of three lakes were all worse than that of National Environment Quality Standard for Surface Water Grade V during the investigation period. According to the Taihu Lake Basin Pollution Standard, the organic nitrogen content （ON%） pollution from the surface sediment of the six lakes were very serious: the minimum from which was three times of the pollution standard level. According to the standard of Canada, the ecological toxic of sediments TN from two lakes were both above serious toxicity standards, while that of other three lakes were all near to the serious toxicity standards. The correlation of nitrogen fractions and TOC content between index of water and surface sediment from the six urban lakes were calculated, and the results showed that the correlation between sediment TN and sediment TOC was the highest ( r =0.965, p <0.01), correlations between water TN and sediment TN and TOC was extremely significant ( p <0.01) as 0.960, 0.964, respectively. The investigation suggested that the control and reduction of TOC and TN in surface sediment (0~10 cm) of urban lake are of important significance to the control of nitrogen pollution in the lake water.

Key words: nitrogen fractions, sediment, pollution, urban lakes, nitrogen fractions, sediment, pollution