Abstract:
In order to explore the spatial and temporal nutrient distribution characteristics of the overlying water and sediment in Dongting Lake, samples of overlying water and sediment from 13typical sites including inflow river, lake region and outflow river were collected and analyzed in January and June, 2012. The content of nitrogen and phosphorus and the trophic levels were analyzed. The results show that the average concentrations of total nitrogen (TN), total phosphorus (TP), ammonia (NH
4+-N) and nitrate (NO
3--N) in the overlying water were 2.34,0.06,0.27and 0.54mg/L, respectively. The average contents of TN, TP, NH
4+-N and NO
3--N in the sediment were 1220.47, 678.97,8.94and 4.41mg/kg, respectively. The highest concentration of phosphorus and nitrogen occurred in the estuary of the inflowing river, especially the Xiangjiang River. The average concentrations of phosphorus and nitrogen in the eastern part of Dongting Lake were higher compared with other regions of the lake. The concentrations of nitrogen and phosphorus in June part of generally higher than those in January, especially for TN in the overlying water (P<0.01). The average value of the comprehensive nutrition state index was 45.93, and its spatial and temporal distribution characteristics were similar to those of TN and TP. Compared with other eutrophic lakes, alga blooms at a large scale did not happen with relatively higher concentrations of TN and TP in the overlying water and the sediment in Dongting Lake, which could be explained by the shorter hydraulic retention time and larger water flow rate.