Isotopic mapping of sedimentary organic matter in the northwestern Pacific marginal sea (Yellow Sea, East China Sea, East Sea)

We investigated physio-chemical properties, sedimentary bulk elements (C, N, S contents and heavy metals concentration), and isotopic compositions (δ¹³C, δ¹⁵N, ⁸⁷Sr/⁸⁶Sr) in the northwest Pacific marginal sea (Yellow Sea, East China Sea and East Sea; R/V Tamgu 3 and 9, February in 2019) to trace the distribution, origin, and reactivity of sedimentary organic matter (OM). Together with hydrodynamic influence (mainly freshwater input) near Yellow Sea and East China Sea, the spatial patterns of sedimentary bulk elements consider that there may be the potential accumulation of natural/anthropogenic derived-OMs transported from regional (Korea-China) river systems. Furthermore, δ¹³C and δ¹⁵N values in surface sediments may be characteristic of the mixture of autochthonous (e.g., algae)/allochthonous (e.g., C3 plant, soil, fertilizer) origins, suggesting the discriminative source contribution on the sedimentary OM distributions. Especially, compared to the isotopic end-members reported from Korean and China river estuaries, isotopic signatures of sedimentary OM may be regarded as the discriminative contribution of various terrestrial derived-origins within the Yellow Sea and East China Sea. Further, ⁸⁷Sr/⁸⁶Sr ratio indicated discriminative weathering impact and terrestrial origin OM transportation within the Korean and China river estuaries. Hence, with respect to the increase of anthropogenic activities near northwest Pacific marginal sea, the source tracing approach estimated via the multi-isotopic mapping may provide important insights for effectively understanding dramatic change of biogeochemical OM cycles from water column to sediments.