Chemical Characterization of Dissolved Organic Matter in Southeastern China Marginal Seas: Source and Biogeochemical Processes

River-influenced marginal seas play a pivotal role in the global carbon cycle due to their intricate sources and biogeochemical processes. For this research, we gathered 24 surface water samples across a transect stretching from the East China Sea (ECS) to the South China Sea (30.45 °N to 18.47 °N), encompassing four distinct regions: the Yangtze River Estuary (YRE), Zhejiang-Fujian Coast (ZMC), Taiwan Strait (TWS), and South China Sea (SCS). We investigated the concentration and composition of dissolved organic matter (DOM) utilizing various analytical techniques including total organic carbon analysis, ultraviolet-visible absorption (UV-Vis), fluorescence excitation-emission matrices spectroscopy (EEMs), and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS).