【摘要】 根据对长江口水下三角洲31个表层样沉积物粒度、总有机碳(TOC)、总氮(TN)的测定,得出了粒度及有机质的分布特征,利用C/N比分析有机质来源及不同来源的贡献率。研究结果表明:1)长江口水下三角洲表层沉积物平均粒径介于3～8φ之间,存在由陆向海变细的趋势;2)TOC含量在0.1%～1.2%之间,平均值为0.52%;TN含量介于0.02%～0.08%之间,平均值为0.057%。TOC和TN含量的分布特征相似,具有自陆向海、由低至高的变化趋势,这主要是受到沉积物粒径的影响,但是TOC在崇明岛东侧和九段沙东侧有两个高值点,可能与人类活动或局地因素有关;粒度校正之后,TOC含量在0.40%～1.67%之间,平均值为0.68%;TN的含量介于0.05%～0.10%之间,平均值为0.07%。TOC含量在近岸地区略高,TN含量是北部地区略高于南部地区,并且TOC和TN都在崇明岛东侧和九段沙东侧有两个高值点;3)C/N比值在6～16之间,平均值为9.6;利用C/N比值估算得到的陆源有机碳含量在35%～90%之间,平均值为60%。C/N比和陆源有机碳含量在长江口南支外围邻近海域表层沉积物中较高,表明南支带来了大量的陆源有机质人海,并呈舌状向东北方向凸出;而在长江北支附近其值相对较低,表明北支径流影响相对减弱,潮流作用相对增强。研究表明,长江南支是主要的陆源有机质人海通道,而进入水下三角洲之后陆源有机碳分布受到了河口混合过程的显著影响。更多还原

【Abstract】 During April 2009,31 sediment cores were collected from the Changjiang subaqueous delta（30°40′ 31°50′N,122°00′～122°50′E;2～50m in water depth）.In this paper,we took the top 4cm surface sediment samples for analyses.Grain size,total organic carbon（TOC ）,and total nitrogen（TN ） distribution patterns were obtained,which can be used to trace the change in organic matter sources for the Changjiang subaqueous delta.The seabed sediment is composed mainly of clay-silt.From land to the sea,grain size shows a fining-seaward trend.TOC ranges between 0.1%and 1.2%,with an average of 0.52%.Likewise,TN ranges between 0.02%and 0.08%,with an average of 0.057%.The distributions of TOC and TN have a good correlation,and their contents in the estuarine waters to the west of 122°10′E are lower than those to the east.The spatial distribution patterns of TOC and TN contents are characterized by increase towards the sea,which is indicative of the effect of sediment grain size.An exception is that there are two high TOC content locations on the eastern side of Chongming Island and Jiuduansha, which may be related to human activities or localized processes.After grain size correction,TOC ranges between 0.40%and 1.67%,with an average of 0.68%.Likewise,TN ranges between 0.05%and 0.10%,with an average of 0.07%.The content of TOC is higher in the near shore areas,but the content of TN is slightly higher in the northern regions than the southern regions.And they both have two high content locations on the eastern side of Chongming Island and Jiuduansha.The C/N ratio ranges between 6 and 16,with an average of 9.6.Q_C/N,the terrestrial organic carbon content,as estimated by the C/N ratio,varies from 35%to 90%,with an average of 60%.These values show that the material source of the Changjiang subaqueous delta represents a mixture of terrestrial and marine materials. The values of the C/N ratio and Q_C/N are higher in the South Branch of Changjiang River estuary,which implies that the South Branch of the Changjiang River brings with it a lot of terrestrial material into the sea,than those associated with the North Branch.At the mouth of the South Branch,these two parameters both have a tongue-shaped distribution protruding towards the northeast,which is indicative of the effect of the Changjiang River diluted water. However,the runoff of the North Branch of the Changjiang River is relatively small and the tide effect becomes a dominant factor,so the values of the C/N ratio and Q_C/N in the North Branch of Changjiang River estuary become low.The results show that the discharge of terrigenous organic matter is mainly through the South Branch,but the composition of organic matter is changed by estuaring mixing processes.更多还原