| Lakes are an important part of fresh-water and are playing an important role in the process of social and economic development. With the progress of industrialization, many of them were polluted, especially by nitrogen, phosphorus and heavy metals. Baihua Lake is one of the five drinking water resources for Guiyang City, and the lake was located on the upstream of Yangtze River, therefore its pollution status has a close relationship with social development of Guiyang area and ecology of Yangtze River watershed.Studied in this research were organic matter, nitrogen, phosphorus, heavy metals,alkaline phosphatase and four types of bacteria involved in the nitrogen cycle in the sediments from Baihua Lake, and the results are as follows:1. The content of organic matter (OM) in Baihua Lake ranged from 11.62% to 18.02%, and the average value was 13.81%. The average value of nitrogen was 0.558%, and that of phosphorous was 1745.1 mg/kg (dry weight). The Pearson correlation coefficient between phosphorous and OM was up to 0.722 (p< 0.05, 2-tailed). DP, Al-P, Fe-P, Ca-P and OP were studied as well in this investigation. The average percentages of DP, Al-P, Fe-P, Ca-P and OP in the sediments from Baihua Lake were 0.12, 5.28, 9.97, 20.95 and 26.47, respectively.2. The average populations of ammonifier, ammonium -oxidizing bacteria, nitrite-oxidizing bacteria and denitrifier in the sediments from Baihua were 46.3×10~4 CFU/g, 122.6×10~4 MPN/g, 31.9×10~4 MPN/g and 103.6×10~4 MPN/g, respectively. The activity of alkaline phosphatase ranged from 62.37 to 199.11 U/100g.3. The method for evaluating potential ecological risk index presented by H?kanson was applied to assess the potential ecological risk of heavy metals to the water body. The highest background values of heavy metals in normal particulate of sediments before the global industrialization and the environmental background values of heavy metals in soil for Guiyang area were used to analyze the accumulation coefficient and potential ecological risk coefficient for each heavy metal. The potential ecological risk index for each sampling location was also discussed. The distribution of various heavy metal contents reveals the regional distributive characteristics. When the highest background values of heavy metals in normal particulate of sediments before the global industrialization were taken as references, the accumulating order for these heavy metals was: Hg> As> Zn> Cu> Cd> Pb, and the order of potential ecological risk was: Hg> Cd> As> Cu> Zn> Pb. When the heavy metals background values for Guiyang area worked as references, the accumulating order was: Hg> Cd> Zn> As> Cu>Pb, and the order of potential ecological risk was: Hg> Cd> As> Cu> Zn> Pb. Hg and Cd were the main contributors of heavy metals pollution for Baihua Lake.4. The sequential extraction procedure presented by Tessier et al.was applied to analyze speciation of Cr, Cu and Zn. The results have suggested that: (1).Cr and Zn were mainly distributed in Residual phase, and Cr had a low level distribution in Carbonate, Reducible and Oxidizable phases, and Zn exhibited a minor distribution in Carbonate and Oxidizable phases. (2).Cu was mainly distributed in Oxidizable and Residual phases and Cu showed a rather limited distribution in Carbonate and Reducible phases; (3). Mobility and toxicity of Cu were lower than those of Zn and Cr, because Cu was mainly distributed in Oxidizable and Residual phases, in which heavy metals mobility was lower than in the other phases.
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