Source, composition and reactivity of sedimentary organic carbon in the river-dominated marginal seas: A study of the eastern Yellow Sea (the northwestern Pacific)

We investigated the source, composition and reactivity of sedimentary organic carbon (OC) in a river dominated continental marginal sea, the eastern Yellow Sea. A multi-proxy approach was applied to 9 riverbank sediments and 69 marine surface sediments, combining bulk and molecular organic parameters. The riverbank sediments (n=9) have on average low C/N ratio (4.8 +/- 0.5) and enriched delta C-13(Toc) values (-21.5 +/- 0.6%) while the BIT index is on average 0.27. The sedimentary OC in the marine surface sediments appears to have a predominantly marine origin (on average C/N ratio=7.0 +/- 0.6 and delta C-13(TOC)=-21.9 +/- 0.5%, n=69) with minor contribution of continental (i.e. soil- and lake/river-derived) OC (on average BIT index=0.00 +/- 0.01, n=69). However, the Delta C-14 values were depleted (on average - 227 +/- 53%, n=8). Accordingly, our results highlight that fossil OC, potentially derived from erosion of sedimentary bedrocks in the catchment areas and/or human activities is being contributed to the sedimentary OC pool in the eastern Yellow Sea. More work is needed to better constrain the source, composition, and age of the organic material supplied to the eastern Yellow Sea, given the lack of biogeochemical data from the Korean rivers. (C) 2016 Elsevier Ltd. All rights reserved.We thank D.-H. Lee (Hanyang University) for his analytical assistance in the laboratory. We also thank to the crew of the R/V Eardo for retrieving the cores. This research was a part of the project entitled "The Study of Marine Geology and Geological Structures in Korean Jurisdictional Seas" funded by the Korean Ministry of Oceans and Fisheries (PM58731). This work was also supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (No. 2016R1A2B3015388)