Distribution and sources of organic carbon, nitrogen and their isotopic composition in surface sediments from the southern Yellow Sea, China

The southern Yellow Sea (SYS) is a significant repository of sedimentary organic matter (SOM) and has been impacted by green tides since 2007; however, data on the distribution and quantitative contributions of different SOM sources has been scarce. TOC, TN and their delta C-13 and delta N-15 values were determined in 38 surface sediments. TOC and TN were high in central mud area and low in sand area. TOC was positively correlated with the abundance of fine-grained sediments, indicating that controlling factors of SOM were the sediment types and circulation system. The SOM included marine and terrestrial organic matter and anthropogenic nutrient inputs according to TOC/TN (5.8-14.3), delta C-13 (-25.1 parts per thousand to -21.0 parts per thousand) and delta N-15 (2.6 parts per thousand-6.4 parts per thousand). High terrestrial contributions in northern and western parts of SYS, were influenced by terrestrial materials and eroded substances of the abandoned Yellow River delta, respectively. In the central mud area of SYS, marine organic matter was dominant.