Contrasting accumulation mechanisms of dissolved organic matter in coastal porewaters under steady-state and mobile mud sedimentary regimes

Coastal sediment porewaters function as highly active transient reservoirs in the global carbon cycle, yet how different sedimentary dynamic regimes determine the early diagenetic fate of porewater dissolved organic matter (DOM) remains poorly constrained. In this study, we investigated the optical and molecular signatures of porewater DOM, coupled with solid-phase geochemistry (grain size composition, sedimentary organic carbon (SOC), and stable carbon isotopes (δ13C)), in the Pearl River Estuary and adjacent coasts (PREC) in the northern South China Sea (SCS).海岸沉积物孔隙水是全球碳循环中高度活跃的暂时性储库，然而不同沉积动力体系如何调控孔隙水溶解态有机质（DOM）的早期成岩归宿，目前仍缺乏明确约束。本研究以南海北部（SCS）珠江口及邻近海域（PREC）为研究区，分析了该区域沉积物孔隙水溶解态有机质的光学与分子特征，并同步测定了固相地球化学指标，包括粒度组成、沉积有机碳（SOC）及稳定碳同位素（δ¹³C）。