Burial of organic carbon in Holocene sediments of the Zhujiang (Pearl River) and Changjiang (Yangtze River) estuaries |
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| Authors: | Shouye Yang Min Tang Wyss W-S Yim Yongqiang Zong Guangqing Huang Adam D Switzer Yoshiki Saito |
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| Institution: | 1. Key Laboratory of Marine Chemistry Theory and Technology, Ministry of Education, Qingdao 266100, China;2. College of Chemistry and Chemical Engineering, Ocean University of China, Qingdao 266100, China;3. Qingdao Collaborative Innovation Center of Marine Science and Technology, Qingdao 266100, China;4. Institute of Marine Organic Geochemistry, Ocean University of China, Qingdao 266100, China;5. Department of Geological Sciences, University of Florida, Gainesville, FL 32611-2120, USA;1. State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200062, China;2. Academy for Advanced Interdisciplinary Studies, Southern University of Science and Technology, Shenzhen 518055, China;3. Centre for Hydrological and Ecosystem Science, Department of Geography, Loughborough University, Loughborough LE11 3TU, UK |
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| Abstract: | The East Asian marginal seas are important sinks of terrigenous materials transported by large rivers. In this study two cores from the Changjiang (Yangtze River) and Zhujiang (Pearl River) estuaries and one core from the inner shelf off of Hong Kong were investigated to examine the burial of organic matter during the postglacial period and its possible links with paleoenvironmental changes. Based on a simple two end-member mixing model, the terrestrial organic matter supplied primarily from the Zhujiang and Changjiang dominates the estuarine areas while marine organic matter contributes more to the inner-mid shelf. The competing contributions of terrestrial and marine organic matter are responsible for the downcore variations of organic elemental compositions. The overall decreasing shifts of total organic carbon concentrations and total organic carbon to total nitrogen ratios in the Zhujiang estuarine sediments since 6.5 kaBP seems to support the notion that depth profiles of organic matter compositions deposited in the Zhujiang Estuary can aid in the reconstruction of monsoon history in the Holocene. Nevertheless, organic matter compositions in the Changjiang Estuary and inner shelf off of southeastern Hong Kong respond in a different and more complex way to freshwater discharges or precipitation changes (monsoon variability) in the catchments, owing to complex controls of deposition and preservation of organic matter in these estuarine and shelf environments. Caution is therefore needed in using organic elemental and isotopic compositions to decipher paleoenvironmental changes in East Asian continental shelves where intense river–sea interactions occur and sedimentary environments change drastically. |
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