长江口及其邻近海域表层沉积物的有机质物源变化分析

2013~2015年，在长江口-杭州湾及其邻近海区采集表层底质样品112个，进行总有机碳（TOC）、总氮（TN）、有机碳同位素（δ13C）、有机氮同位素（δ15N）和C/N的测定，得到碳氮元素的空间分布特征；并与2006年的数据对比，观察TOC、TN和有机碳δ13C的空间变化。将研究区划分为北部的长江水下三角洲和南部的浙闽内陆架沉积区两部分，结果表明:TOC和TN在北部由陆向海先升高后降低，在浙闽内陆架沉积区表现为向海增加，并在122°~123°E范围内的29°N附近出现高值；有机碳δ13C由陆向海变轻，且在长江水下三角洲比浙闽内陆架沉积区要低，变化较南部慢；2006年和2015年的数据对比表明，近年来，TOC和TN降低，有机碳δ13C变轻，碳氮元素的空间分布更加均一，这些变化在123.5°E以西的长江口地区表现得尤为明显。

Change of organic matter sources in surface sediments over Changjiang estuary and its adjacent waters

In order to investigate the variations of organic matter in surface sediments over Changjiang estuary and Hangzhou bay, 112 surficial sediments were collected, and the content of total organic carbon (TOC), total nitrogen (TN), stable carbon isotope (δ13C) and stable nitrogen isotope (δ15N) were analyzed.Two regions were identified within the study, which were subaqueous Yangtze delta in the north and Zhe-Min inner shelf deposition in the south.The results indicateed that TOC and TN, whose higher content were found around 29°N ranging from 122°E to 123°E, increased at first and then decreased from land to sea in subaqueous Yangtze delta, and an increasing trend was observed to Zhe-Min inner shelf deposition.δ13C, increasing towards sea, in the north was lighter than that of south.Since 2006, TOC and TN had significantly decreased, and δ13C had become lighter, the distribution of TOC or TN showed a more uniform pattern especially in Changjiang estuary, which performed more apparently in the west of 123.5°E.