Abstract:

The vertical distribution and seasonal variations of pore water nutrients of three typical columnar sampling sites were analyzed and compared by continual sampling and investigation in East Lake,a serious eutrophicated shallow lake in China.The results show that the highest value of pore water nutrient concentrations in East Lake sediment generally appearred in the above 5 cm,and a rapid decreasing process occurred between 5 cm to 10 cm,then it became stabilized with slight fluctuations between 10 cm to 26 cm.Nutrient concentrations in interstitial water in winter was significantly lower than other seasons,summer and fall was slightly high.It is suggested that the nutrient concentrations in sediment pore water was directly influenced by near by pollution sources,and related to that of overlying water,but not significantly.Low concentration of interstitial water nutrient pollution in the winter season,was mainly due to the decreasing of pollutant emissions which accelerated the upward diffusion of pore water nutrient to overlying water,reducing the deposition of nutrients on the surface of sediments,and the lower the temperature leading to reduced microbial activity and thus reduced the mineralization of organic matterand the amount of decomposition.Regular dredging depth can effectively remove the heavily polluted surface sediments of East Lake