Study On The Forms Of Nitrogen In The Sediments Of The East China Sea

Nitrogen forms in marine sediment play an important role in its biogeochemical cycle and may serve as an efficient proxy for marine sedimentary environmental changes. By far, the study on nitrogen forms in the sediments of the East China Sea is limited. This thesis focus on the forms of nitrogen in 6 core sediments of the East China Sea (stations E4, A13, E5, E6, P4, P5), and their contributions to nitrogen biogeochemical cycle in marine system are evaluated.In the sediments, Norg was the main form of nitrogen, accounting for 66 % of total nitrogen (TN); Nfix was lower than Norg, accounting for 32 % of TN, except for station E6 where Nfix was the main form of nitrogen accounting for 55 % of TN; NO3-ex was the least in the sediments, only accounting for 1 % of TN.The distributions of nitrogen forms in the sediments showed obvious regional characteristics for the difference in geographic environment. The contents of nitrogen adjacent to the Changjiang estuary (stations E4, A13) were high; the sediment (station P4) in the shelf slope of the East China Sea affected by the Kuroshio was also observed with high concentrations of nitrogen forms. While the content of nitrogen forms (station E6) were comparatively low in the middle shelf of the East China Sea, for terrigenous materials input was limited and the sediment consists mainly of coarse gravel.In the Changjiang estuary, the concentrations of nitrogen forms in upper layer of the core sediment decreased gradually with increase in depth. The concentration and distribution of nitrogen forms indicated the environmental effect of anthropogenic activities on the estuarine ecosystem.Correlation analysis among nitrogen forms and organic carbon (TOC) indicated that there were significant linear correlation between Nfix and TOC, NH4-ex and TOC. While there was no significant linear relationship between NO3-ex and TOC. There was a significant linear relationship between Norg and TOC in all stations, and the degradation rate of TOC was slower than Norg.