Simulation For Seasonal Distribution Of Bacteria In The Sediment-water Interface Of The Superficial Shallow Limnic Sediments

The shortage of water resources has become one of the severe problems to affect the strategies of sustainable development in our country. Although the Yangtze River region is a more concentrated area of freshwater lakes, eutrophication is now becoming more and more serious and even the water quality can not be ignored. In the natural water environment, bacteria play an important role in the migration system, circulation, biological transformation and bio-mineralization of pollution in the contaminants of water and sediments. Sediment has been proved for its important role for both reservoir and potential source of pollution, and it has a great significance of studying bacterial genus for sediment, bacteria, quantity, and distribution in the context of environmental chemistry of water ecosystems.In this thesis, based on the collected samples of overlying water and sediment in Poyang Lake in autumn 2007, the seasonal simulation was done in our laboratory. The nitrifying bacteria, denitrifying bacteria, ammonification bacteria, sulfur bacteria and total bacteria were counted. Those results revealed the vertical distributions of bacteria in sediments and the correlation of bacteria with nitrogen, sulfur and other elements, and the seasonal effects of inner pollution resources were also carried out. The main conclusions are presented as follows:①In the count of nitrifying bacteria by MPN method, the method was successfully modified after an excess amino acid amine added as a masking agent in the detection, and result showed much better than the previous procedure.②The distribution of aerobic bacteria such as nitrifying bacteria, ammonification bacteria, sulfur bacteria are from surface to bottom of sediment. It showed the underlying trend of decline by the content of oxygen and other factors. But the higher values may occur locally, it may relate to the higher levels of pollutants locally.③The contents of nitrifying bacteria and ammonification bacteria are the highest in 15℃, the contents of denitrifying bacteria and sulfur bacteria are the highest under 25℃stirring. In addition to the lowest level of sulfur bacteria in 15℃, the other three occurred at 25℃or 25℃under stirring conditions.④In addition to nitrifying bacteria, the distributive trend fluctuations of the denitrifying bacteria, ammonification bacteria, and sulfur bacteria are larger than that at the same temperature under stirring conditions, which may be due to changes of the material cycle in the natural state, and then we could infer that human activities have a certain impact on the natural environment.⑤The distributions of nitrifying bacteria and denitrifying bacteria have a strong correlation with mature pyrite sulfur (PS) and total reducible sulfur (TRS), which has a certain relationship with sediment redox state, because it influence the strength of nitrification and nitrogen conservation. Therefore it positively correlated with the ammonia nitrogen (AN) in strong reducing environment, and this result shows the negative correlation in the weak reducing environment. Sulfur bacteria has low correlation with other factors at 5℃, but the correlation coefficients of sulfur TRS and AN were significantly increased when the temperature increased. This result indicates that the change of temperature in their living environment had influenced the number of sulfur bacteria.