Nitrogen Speciation Of The Sediments And Flux In Sediment-water Interface In North Bay Of Taihu Lake

Sediment cores from Taihu lake were selected to study the vertical distribution characteristics of nitrogen from the overlying water to porewater, and then try to calculatethe fluxes of ammonia(NH4+-N) from different areas of the lake by using a one-dimensional transport-reaction model based on the Fick’s First Law. By improving Ruttenberg phase-separation extraction method, the characteristics of Transferable nitrogen(EFN)、Mineralization Nitrogen and Fixed Ammonium and the connections among them in an attempt to discover the significance of sediments from the ecological and environmental perspective will be found.The experimental results and the major findings are as follows:1.In the whole, the concentration of ammonium nitrogen is lower than nitrate nitrogen in the main area in Taihu Lake. The ammonia nitrogen pollution in the central area is relatively slight, while nitrogen pollution of Taihu Lake North Bay is relatively severe, ZhushanLake and GonghuLake in particular. In Zhushan Lake, the concentration of nitrate nitrogen rapidly dectease and remains relatively stable when it enters across the sediment-water interface, but the rest of the porewater and overlying water of nitrate-nitrogen in sediment-water interface increases rapidly. It means these areas are mainly the overlying water release.2.The diffusion flux of ammonium nitrogen in the central lake area is lower, down from 12.5 mg·(m2·d)-1, while in Gonghu Lake and Meiliang Bay, Zhushan Lake, the diffusion flux of ammonium nitrogen is much higher. Ammonium nitrogen are released from sediment to overlying water in all regions, which shows that in Taihu Lake region there is a potential risk of nutrients(ammonium) release. Northern Lakes and daily load contribution of ammonium nitrogen in Lake area is 16.06 t·d-1, Lakes daily load of ammonium nitrogen contribution of 12.61 t·d-1, contribution to 78.5%.3.The total nitrogen(TN) in the surface of sediment reaches an average of 1.07 g·kg-1, lower than the average for other research areas in the country. EFN in the marsh is about 324.67 mg·kg-1, TN 39.85%, indicating that nitrogen in surface sediments of shallow lakes of Taihu Lake is limited. Four forms of acid leaching in nitrogen transformation of nitrogen forms with nitrogen as the subject is its advantage, with an average 67.09% per cent of transferable nitrogen, followed by strong oxidizer nitrogen leaching, alkali leaching nitrogen, ion exchanged nitrogen, respectively accounting for EFN, and 18.12%, 12.86% and 1.93%.4.Four types of EFN are different in different communities of the lake, and transformation of nitrogen in the Zhushan Lake is the highest, about 128.107 mg·kg-1, while lowest in the central area of the lake, about101.706 mg·kg-1. The vast majority of transferable nitrogen content in the samples in the sediments decreased with depth. The vertical variation of nitrogen in ZhushanLake shows more obvious fluctuations. The result has ecological significance by showing that nitrogen in bottom sediments in Taihu Lake is not easy to use, EFN in surface sediments is high.