Dynamics of endogenous nitrogen release and sedimentation in small water bodies of the Taihu Lake Plain
To investigate the dynamics of endogenous nitrogen release and sedimentation in small water bodies,we conducted continuous monitoring of five such representative water bodies,including ditches,ponds,and streams,of the Taihu Lake Plain water network area from January to November 2023.Samples of the overlying water,sediment,and settling particulate matter were collected monthly,and the nitrogen concentrations and physicochemical factors were determined synchronously.The diffusion fluxes of NH4+and NO3-at the sediment-water interface,as well as their sedimentation and endogenous release fluxes,were calculated on the basis of the pore water diffusion model.The results indicated that the endogenous nitrogen released in small water bodies of this water network area was predominantly in the form of NH4+,with the total amount released ranging from 224 to 9 631 kg·km-2·a-1 and the diffusion fluxes ranging from 50 to 312 kg·km-2·a-1,contributing 2.2%to 15.1%to the nitrogen concentration of the water body.Compared with the proportion of endogenous nitrogen contribution from large water bodies,such as rivers and lakes,that from small water bodies was relatively low.Further analysis revealed that the concentration difference between the overlying water and sediment,as well as the flow velocity,were key factors affecting endogenous nitrogen release in small water bodies.Endogenous nitrogen pollution in small water bodies was severe.To effectively reduce such pollution,steps should be taken to strengthen sediment management,strictly control the input of exogenous pollutants,actively enhance the natural purification capacity of water bodies,reasonably regulate the water flow velocity,and establish a complete monitoring and early warning system.
small water bodyendogenous pollutionsediment-water interfaceendogenous nitrogen release
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