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.