渤海湾表层沉积物中有机碳的分布与物源贡献估算

ORGANIC CARBON IN SURFACE SEDIMENTS OF THE BOHAI BAY,CHINA AND ITS CONTRIBUTION TO SEDIMENTATION

依据渤海湾及其邻近海域163个表层沉积物样品的总有机碳(TOC)和总氮(TN)的分析数据,探讨了渤海表层沉积物TOC的空间分布与物源贡献。结果显示,渤海湾TOC呈现南高北低的空间分布特征,TOC与粒度有一定的相关性且TOC高含量区与泥质区相吻合,表明TOC分布在一定程度上受控于沉积动力环境。TOC和TN之间显著相关,在此基础上建立了TOC和TN的一元线性回归模型,估算了样品中无机氮(IN)的含量,得到了有机氮的校正值(ON)。扣除样品中IN的影响后,本区沉积有机质的C/N值介于4～17之间,平均值为9,显示本区TOC为陆源和海洋自生的混合来源。利用基于TOC/ON比值计算沉积有机质中陆源和海洋源贡献的方法,估算出了陆源有机碳和海洋自生有机碳对本区TOC的相对贡献,陆源有机质的输入在研究区起着主导作用。

Organic carbon and total nitrogen were analyzed for the 163 surface sediment samples collected from the Bohai Bay during the summer of 2006.In this paper,we mainly discuss the distribution of total organic carbon（TOC） and its contributors.Results show that the concentrations of TOC are high in the southern and low in the northern part of the study area.There is a positive correlation between TOC and median diameter of grain sizes of sediments,indicating that the distribution of TOC is controlled by depositional environment to some degree.A good correlation exists between TOC and TN in surface sediments.There is small amount of inorganic nitrogen in surface sediments,which may influence the application of TOC/TN ratios to identify the source of organic matter.Therefore,we removed the influence of inorganic nitrogen to the calculation.C/N ratios of samples in study area vary from 4 to 17 with an average at 9,suggesting the mixed origin of TOC from both marine and terrestrial sources.The contributions of terrestrial and marine sources to TOC were estimated,and the results indicate that the input of terrigenous organic carbon is the dominant contributor to the TOC in the study area,especially in the nearshore and estuarine areas.