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

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.