渤海南部海域柱状沉积物中氮的形态与有机碳的分解

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

海洋沉积物中氮形态的研究是研究其生物地球化学循环的重要前提 ,柱状沉积物中氮的形态分布在一定程度上反映了其早期成岩作用的进程及结果 .利用分级浸取分离方法首次对渤海南部海域自然粒度下 5个柱状沉积物样品进行了分析 ,依据是否可由试剂提取将其分为可转化态和非转化态 ,系统地研究了可转化态中各形态氮的分布特征及早期成岩作用 .研究表明 ,渤海南部海域自然粒度下柱状沉积物中 ,OSF -N和IEF -N是可转化态氮的优势形态 .各形态氮的含量随深度变化趋势不同 ,成岩作用亦不同 .沉积物中有机氮的分解速率常数为 1 5 51× 1 0 -3 a ,且对各生源要素的分解速率常数有N >P >C >Si;OC/TN比值远小于OC/ON ,说明沉积物中保留了大量无机氮 (IN)和非转化的有机氮 ,OC/ON值随深度增加而减小是由于沉积物中富集了ON ;柱状沉积物中 ,表层比深层可转化态氮占其总量的比例高 ,在局部区域由于深层沉积物中氮的“再活化”

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 -3 a -1 , 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 preserved 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 transferable under some special circumstance,which induces the proportion of transferable nitrogen in TN in deep layer to he almost the same with in surface.