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Please use this identifier to cite or link to this item: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/41092

Title: Efficient trapping of organic carbon in sediments on the continental margin with high fluvial sediment input off southwestern Taiwan
Authors: KAO Shuh-Ji
WANG Chung-Ho
LIU Kon-Kee
Contributors: 國立臺灣海洋大學:海洋環境化學與生態研究所
Keywords: Taiwan
Carbon burial
Organic carbon
Stable isotope
South China Sea
Date: 2006-12
Issue Date: 2017-02-08T06:40:29Z
Publisher: Continental Shelf Research
Abstract: Abstract: Accumulation rates of marine and terrigenous organic carbon in the continental margin sediments off southwestern Taiwan were estimated from the measured concentrations and isotopic compositions of total organic carbon (TOC) and previously reported sedimentation rates. Surficial sediments were collected from the study area spanning from the narrow shelf near the Kaoping River mouth to the deep slope with depths reaching almost 3000 m. The average sediment loading of Kaoping River is 17 Mt/yr, which yields high sediment accumulation rates ranging from 0.08 to 1.44 g cm-2 yr-1 in the continental margin. About half of the discharged sediments were deposited on the margin within 120km of the river mouth. Carbon isotopic compositions of terrestrial and marine end-members of organic matter were determined, respectively, based on suspended particulate matter (SPM) collected from three major rivers in the southwestern Taiwan and from an offshore station. All samples were analyzed for the TOC content and its isotopic composition (δ13Corg). The SPM samples were also analyzed for the total nitrogen (TN) content. TOC content in marine sediments ranges from 0.45% to 1.35% with the highest values on the upper slope near the Kaoping River mouth. The TOC/TN ratio of the SPM samples from the offshore station is 6.8±0.6, almost identical to the Redfield ratio, indicating their predominantly marine origin; their δ13Corg values are also typically marine with a mean of -21.5±0.3‰. The riverine SPM samples exhibit typical terrestrial δ13Corg values around -25%o. The δ3Corg values of surficial sediments range from -24.8%o to -21.2%o, showing a distribution pattern influenced by inputs from the Kaoping River. The relative contributions from marine and terrestrial sources to sedimentary organic carbon were determined by the isotope mixing model with end-member compositions derived from the riverine and marine SPM. High fluvial sediment inputs lead to efficient trapping of organic carbon over a wide range of water depth in this continental margin. The marine organic accumulation rate ranges from 1.6 to 70 g C m-2 yr-1 with an area weighted mean of 4.2 g C m-2 yr-1, which is on a par with the mean terrestrial contribution and accounts for ∼2.3% of mean primary production. The depth-dependent accumulation rate of marine organic carbon can be simulated with a function involving primary productivity and mineral accumulation rate, which may be applicable to other continental margins with high sedimentation rates. Away from the nearshore area, the content of terrigenous organic carbon in surficial sediments decreases with distance from the river mouth, indicating its degradation in marine environments.
Relation: 26(20)
URI: http://ntour.ntou.edu.tw:8080/ir/handle/987654321/41092
Appears in Collections:[海洋環境與生態研究所] 期刊論文

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