不同水情时期鄱阳湖沉积物-上覆水界面无机氮分布及交换通量分析OA

The objective of this study is to reveal the exchange process of inorganic nitrogen at the sediment-water inter-face and the characteristics of ＂source/sink＂ dynamics in Poyang Lake.Consequently,the investigation centered on the sediment and overlying water under varying hydrological conditions within the lake.Through meticulous analysis of the spa-tial and temporal distribution and exchange flux of inorganic nitrogen,we have successfully identified the ＂source/sink＂roles of these nitrogen forms.The findings demonstrate that the fluctuations in the concentrations of total nitrogen(TN),ammonium(NH3-N),nitrate(NO3--N),and nitrite(NO2--N)in the overlying water followed the sequence of:low wa-ter period＞high water period.The concentrations of TN,NO3--N,and NO2--N were higher in the northern and inlet are-as of the lake,while NH3-N concentrations were elevated in the central region.According to laboratory simulation experi-ments,during the wet season,the exchange fluxes of TN,NH3-N,NO3--N,and NO2--N ranged from 0.30 to 8.41,0.63 to 3.81,-3.32 to-0.13,and 0.03 to 0.12 mg·m-2·h-1,respectively.During the dry season,the exchange flu-xes ranged from 0.59 to 5.41,0.34 to 2.32,0.31 to 1.87,and 0.02 to 0.06 mg·m-2·h-1,respectively.The sedi-ment was found to be a"source"for TN,NH3-N,and NO2--N.During the dry season,the sediment functioned as a ni-trate source,whereas in the wet season,it served as a sink for nitrate.Correlation analyses reveal a strong correlation be-tween nitrogen exchange fluxes and chlorophyll a(Chl-a)and total phosphorus(TP).In order to prevent excessive growth of algae and reduce the risk of eutrophication in Poyang Lake,it is imperative to regulate the release of endogenous nitro-gen from sediments.The phosphorus ratio and Chl-a have substantial impacts on nitrogen exchange flux;It is suggested that TP concentration and chlorophyll concentration may be important factors affecting the change of nitrogen exchange flux in Poyang Lake.