Nitrogen forms and decomposition of organic carbon in the southern Bohai Sea core sediments

Sequential extraction process in natural grain size is used to study the existent forms of nitrogen of five core sediments in the southern Bohai Sea, and form characteristics of nitrogen and its diagenesis process are researched.Results indicate that transferable nitrogen accounts for 34.25% of total nitrogen(TN) and exists mainly in the form of OSF-N and IEF-N, which have different distributions and their early diagenesis varies distinctly.Organic nitrogen(ON) has the decomposition rate constant of 15.51×10^-3a^-3, and rate constant of C, N, P, Si has the sequence N > P > C > Si.The main reason for much lower C/N ratio than OC/ON is that abundant nitrogen is pr eserved during the early diagenesis.OC/ON ratio decreases with depth, which is due to two main reasons:abundant inactive components contained in ON and ON adsorption to clay minerals.In general, transferable nitrogen accounts for more proportion of TN in surface than in deep layer of core sediment.The stable forms can activate and become transfer able under some special circumstance, which induces the proportion of transferable nitrogen in TN in deep layer to he almost the same with in surface.