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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。
Based on the measurements of grain size, total organic carbon (TOC) and total nitrogen (TN) of 31 surface sediments in the Yangtze River Estuary, the grain size and distribution characteristics of organic matter were obtained. The C / N ratio was used to analyze the source of organic matter and different sources The contribution rate. The results show that: 1) The average size of surface sediments in the submarine delta of the Yangtze River Estuary ranges from 3 to 8φ, and tends to decrease from the seaward to the sea; 2) the TOC content is between 0.1% and 1.2% with an average of 0.52% ; TN content ranged from 0.02% to 0.08% with an average value of 0.057%. The TOC and TN contents are similar in distribution characteristics, and have a trend from low to high from the seaward direction, which is mainly affected by the grain size of the sediments. However, there are two high points on the eastern side of Chongming Island and east of Jiuduansha, May be related to human activities or local factors; after the particle size correction, TOC content of 0.40% ~ 1.67%, with an average of 0.68%; TN content of between 0.05% ~ 0.10%, with an average value of 0.07%. TOC content is slightly higher in the nearshore area, TN content is slightly higher in the northern area than in the southern area, and both TOC and TN have two high spots on the eastern side of Chongming Island and east of Jiuduansha; 3) The C / N ratio is between 6 ~ 16, with an average of 9.6. The C / N ratio of terrestrial organic carbon estimated from 35% to 90% with an average of 60%. C / N ratio and terrestrial organic carbon content are higher in the surface sediments near the south branch of the Yangtze River Estuary, indicating that a large amount of terrestrial organic matter sea is brought from the southern branch and protrudes tongue-shaped to the northeast; while in the Yangtze River The value of the north branch is relatively low, indicating that the impact of runoff in the north branch is relatively weakened and the tidal current effect is relatively enhanced. The results show that the South Branch of the Yangtze River is the main terrestrial organic sea channel, and the distribution of terrestrial organic carbon after entering the submarine delta is significantly affected by the river mouth mixing process.