Spatiotemporal responses of nitrogen and phosphorus loads in sediments and overlying water of Nansihu Lake
南四湖沉积物对上覆水氮磷负荷的时空响应

Characteristics of spatial distribution in September 2010 and temporal variation from 1960 to 2010 of total nitrogen and total phosphorus load in Naisihu Lake were analyzed using SWAT model and water quality monitoring. Total organic carbon, total nitrogen and total phosphorus in surface sediments and sedimentary cores obtained in September 2010 were determined. Spatial distribution of total nitrogen and total phosphorus in September 2010 and temporal variation in recent 50 years in the sediment of Naisihu Lake were analyzed. The spatiotemporal responses of total nitrogen and total phosphorus loads in sediments and overlying water were studied. The results indicated that spatially, phosphorus in sediment had the good responses to that in the overlying water with the correlation coefficient of 0.895, because the phosphorus in sediment and water were mainly inorganic phosphorus. The major form of nitrogen in sediment was organic, but the nitrogen in water was mainly inorganic, leading to insignificant responses. Temporally, nitrogen and phosphorus in sediment had good responnses to those in the overlying water. The change of nitrogen and phosphorus can roughly be divided into 3 sections, but the responds of sediment lagged behind the water. This change was similar to the change of GDP in Jining, which was the largest city in Nansihu basin, so it was indicated that human activity was closely related with lake pollution.