长江口不同沉积环境沉积物中碳的分布和来源

Distributions and sources of various forms of carbon in different sedimentary environment of Changjiang River Estuary

利用2004年5月在长江口门区获得的R3、N3、S3和S1四个沉积物柱状样品,对其各种形态碳的含量和垂直分布、TOC/N值以及同位素δ13Corg值进行了分析,并结合该区域的水文悬沙特征,探讨了影响沉积物中碳埋藏的因素及其物质来源,结果表明:长江的径流量和沉积速率是影响长江口碳埋藏的两大重要因素,对各种形态碳在沉积柱中的垂直分布及波动程度产生重要影响,其中长江口南、北支口门3个站位中的总氮(TN)与有机碳(TOC)关系密切,两者呈极显著的正相关关系(P<0.01),有机碳中海洋自生TOC的比例随离岸距离的增加而增加,而TN主要是以有机氮的形式存在;水下三角洲前缘的S1站位TOC含量与TN含量的相关性较差,故其氮除了以有机氮的形式存在之外,还有一些以其它形式存在的氮。长江口南、北支口门和水下三角洲前缘区域有机质来源为海、陆混源,沉积物中有机质同时受到了海源和陆源物质的双重影响,相对来说,水下三角洲前缘区域受到海源物质影响更明显。

Based on the data of proportion and vertical distribution of carbon,TOC/TN ratio and the values of δ13Corg in the core sediments of R3、N3、S3 and S1 collecting in May 2004,combined with the region＇s hydrological characteristics of suspended matters,the affecting factors of carbon burial and their sources have been discussed.The results show that the runoff and sedimentation rates are the main factors to control the carbon burial in Changjiang River Estuary.They influence the vertical contents of various forms carbon obviously.The TN and TOC in three stations in south branch and north branch have clear positive correlationship（P0.01）.The proportions of pelagic organic carbon increase with the offshore distance increases and the organic nitrogen takes the main parts in the TN nitrogen.The relativity of TOC and TN in the core S1 which is far from estuary compared with other stations is not good because of other form nitrogen existed.The organic matters in south branch and north branch of Changjiang River Estuary as well as in front of subaqueous delta are mixed with both terrigenous and pelagic sources,but sediments in front of subaqueous delta are relatively more influenced by pelagic source.