Distribution characteristics of organic matter and their implications on environment change in the mud area on the eastern shore of Liaodong Peninsula

In order to investigate the influence of human activities within the Yalu River catchment, in terms of the import of terrestrial inputs from the Yalu River, on the sedimentary environment of the estuary and continental shelf mud deposition area, two sediment cores, Q02 and Q04, were collected from the mud deposition area of the eastern Liaodong Peninsula.Subsequently, the content of ²¹⁰Pb dating, grain size, total organic carbon (TOC), total organic nitrogen (TN), stable carbon isotope (δ¹³C) were analyzed; finally, the C/N ratio and δ¹³C value were used to analyze the contribution of different organic matter source.The results show that:(1) TOC and TN were gradually increased during the past 100 years.The C/N ratio ranged from 9 to 11, indicating that the organic carbon is characterized by terrestrial and marine mixing sources. (2) The organic carbon proportions originating from terrestrial and marine source indicated a decreasing and increasing trends, respectively, implying that the eastern and western of the study area suffered from different controlling factors.In the eastern area, the sedimentary environment is mainly affected by catchment environment change and land-sea interaction:reclamation, natural disasters and wars caused the vegetation cover reduced, and the reservoir construction decreased the input of terrestrial organic carbon.The sedimentary environmentof eastern area is mainly controlled by human activities and water eutrophication:"Closure" Policies result in the destruction of vegetation cover, and the ports construction, aquaculture lead tothe increase of nutrients in the water bodies, which cause deterioration of the marine environment.