Space-time Variety of Organic Matter and Nutrient in Surface Sediments from Poyang Lake

The space-time variation of organic matter(OM),total nitrogen(TN) and total phosphorus(TP) in surface sediments from Poyang Lake was studied by analyzing historical data and testing sediment samples.The results indicated that:The OM,TN and TP contents in surface sediments decreased from south to north of Poyang Lake.The highest OM(0.420%-3.175%) and TN(0.026%-0.235%) contents were found in sediments from the rump parliament of 'five rivers',the center of lake was second,but the highest TP content was presented in sediments from the rump parliament of Gan River,Fu River and Xin River.The increment of water from 'five rivers' in flooding seasons significantly enhanced the OM,TN and TP contents in sediments from the Poyang Lake,especially for the north area of the lake,but the TN contents in sediments from the rump parliament of south lake in dry seasons were higher than those in flooding seasons.The OM,TN and TP contents in sediments of Poyang Lake trended to increase obviously from 1992 to 2008,especially for OM and TP.The pollution level of OM,TN and TP in sediments from Poyang Lake had reached or exceeded the level of that in sediments from the eutrophication lake.Comparing to the other four large fresh-water lakes,the water quality of Poyang Lake was well,but presented decrease trend.The higher TN and TP contents in sediments from Poyang Lake led to larger risk of eutrophication.