中文摘要：

通过分析长江口外海域不同区域有机碳和氮的分布特征及其影响因素，了解了底部沉积物中有机碳和氮同位素的生物地球化学特征，探讨二者对长江口外海域底部沉积物中有机物来源的指示意义。运用质量混合模型，计算了长江输入的陆源有机物的贡献及其空间变化。结果表明，长江口外海域沉积物中TOC和TN的分布和东海陆架的环流体系有着密切关系，与环流的分布相对应，如果大致沿31°N和123°E作为分界线，整个研究区的TOC和TN的分布可划分为4个具有不同分布特征的区域。TOC、TN、δ^13C和δ^15N分别与沉积物的平均粒径呈线性相关关系，因此，粒度效应是控制长江口外海域沉积物中有机物分布和稳定同位素碳、氮的一个重要因素。研究区内的C／N比值能够在一定程度上体现有机物的来源信息，但δ^15N表现出了与C／N和δ^13℃不同的区域分布和变化特征。陆源有机物来源比重较高的区域与长江口外海域赤潮突发频率最高的地区相对应。长江口附近沉积物中的陆源有机物来源最高，超过了50％，且等值线呈舌状向东北方向凸出，表明了长江冲淡水的影响。陆源颗粒态有机物沉海底后，要不断经历早期成岩作用和生物作用，因此在在相同地点，陆源有机物对沉积物中有机物的贡献，要明显小于对悬浮颗粒态有机物的贡献。

英文摘要：

In this paper, 34 superficial sediment samples were collected in Changjiang River Estuary and its adjacent sea area. Subsequently, grain size, total organic carbon, total nitrogen, carbon and nitrogen isotope compositions were also analysized. Finally, organic carbon and nitrogen spatial distribution patterns in Changjiang River Estuary and its adjacent sea area were studied; characteristics of stable carbon and nitrogen isotope in seabed sediments and their implications for tracing organic matter source were discussed; and contributions of different organic matter sources in seabed sediment were calculated. The spatial distribution patterns of total organic carbon and total nitrogen show apparent correlation with currents of East China Sea shelf. Corresponding to distributions of these currents, the study area could be divided into four different parts. Total organic carbon, total nitrogen, and organic carbon and nitrogen stable isotope in sediments shows linear correlation with mean grain size, respectively, thus ＂grain size effect＂ is an important factor that influences their distributions. C/N ratio can reflect source information of organic matter to a certain degree. In contrast, nitrogen stable isotope shows different spatial distribution patterns with C/N and organic carbon stable isotope, according to their relationships and regional distributions. The highest contribution （more than 50%） of the terrestrial organic carbon appears near the Changjiang River Estuary, and their isolines project towards northeast, indicating the influence of Changjiang dilution water. The terrestrial particulate organic matter suffers from effects of diagenesis, benthos and incessant inputting of dead organic matter of plankton, after depositing in seabed. Therefore, the contribution of terrestrial organic carbon to particulate organic matter is obviously greater than that to organic matter in sediments in the same place.