【摘要】 河口及近海沉积物是重要的有机碳储存库，其在地质时间尺度上对碳的埋藏过程及对大气CO₂含量变化具有重要影响。有机碳的活性（可降解性）是决定其在海洋沉积环境中保存效率的关键因素之一。然而，目前对于海洋沉积物中活性有机碳的分布特征及其控制机制仍缺乏系统认识。本研究选取采集自长江口及邻近东海陆架区的6根沉积物岩心，通过化学氧化法区分并定量表征活性与惰性有机碳的含量特征，揭示了其随沉积深度的演变规律。结合沉积物中的叶绿素a含量、CT扫描数据以及理化参数（pH值、含水率）,系统探讨了影响沉积有机碳化学稳定性的主要环境控制因素。结果表明，岩心沉积物中总有机碳含量为0.16%～0.90%,整体以活性态组分为主，约占51%～88%,主要来源于海洋有机质。沉积物颗粒组分通过对活性有机碳的吸附作用，主导了总有机碳的含量分布。在研究区域范围内，较小的粒径、适中的含水率（70%）、中性略偏碱的环境（pH值为7.6～8.0）以及较弱的生物扰动强度（0～2%）有利于活性有机碳的保存。更多还原

【Abstract】 Estuarine and coastal sediments serve as significant reservoirs for organic carbon storage, play a crucial role in the long-term carbon burial process and influence atmospheric CO₂ content variations. The lability（degradability） of organic carbon is one of the key factors determining its preservation efficiency in marine sedimentary environments. However, systematic understanding of the distribution characteristics and controlling mechanisms of labile organic carbon in marine sediments remain limited. Six sediment cores collected from the Changjiang（Yangtze River） Estuary and the adjacent East China Sea continental shelf were selected in this study. Using chemical oxidation methods, the study distinguished and quantified the content characteristics of labile and refractory organic carbon to reveal their evolution with sedimentary depth. By integrating chlorophyll-a content, CT scan data, and physicochemical parameters（pH, water content）, the study systematically examined the primary environmental control factor influencing the chemical stability of sedimentary organic carbon. Results showed that the total organic carbon content in the sediment cores ranged from 0.16% to 0.90%, predominantly consisting of labile components（accounting for 51%-88%）, primarily derived from marine organic matter. Sedimentary particle composition dominated the distribution of total organic carbon through the adsorption of labile organic carbon. Within the study area, finer grain size, moderate water content（70%）, slightly alkaline pH（7.6-8.0）, and weaker bioturbation intensity（0-2%） were favorable for the preservation of labile organic carbon.更多还原