Seasonal variation of inorganic nitrogen in water and sediment of intertidal flats on the Shanghai coast

In 1998-1999, contents of inorganic nitrogen (NH₄-N, NO₃-N and NO₂-N) in water and sediment of intertidal flats of the Shanghai coast were investigated at three stations (CY, DH and LY). Results show that the main form of inorganic nitrogen in water of intertidal flats is of NO₃-N with a wide range (37.2~226.1 mol · L ^-1); most of exchangeable N in surface intertidal sediments is of NH₄-N, accounting for 70%~85%; NH₄-N and NO₃-N are the main form of inorganic N in pore water of surface sediments. Content distributions of NH₄-N, NO₃-N and NO₂-N in water and sediment of intertidal flats vary seasonally. The basic factors affecting the seasonal variation of inorganic N were discussed. Moreover, the diffusion fluxes of NH₄-N, NO₃-N and NO₂-N between water and intertidal sediment interface were estimated, indicating that NH₄-N in sediments may play an important role in the Yangtze estuarine and coastal environment.