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首页> 外文期刊>Journal of oceanography >Contrasting Chemical and Isotopic Compositions of Organic Matter in Changjiang (Yangtze River) Estuarine and East China Sea Shelf Sediments
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Contrasting Chemical and Isotopic Compositions of Organic Matter in Changjiang (Yangtze River) Estuarine and East China Sea Shelf Sediments

机译：长江口和东海陆架沉积物中有机质的化学和同位素组成对比

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摘要

To examine the source and preservation of organic matter in the shelf sediments of the East China Sea (ECS), we measured bulk C/N and isotopes, organic biomarkers (n-alkanes and fatty acids) and compound-specific (fatty acids) stable carbon isotope ratios in three sediment cores collected from two sites near the Changjiang Estuary and one in the ECS shelf. Contrasting chemical and isotopic compositions of organic matter were observed between the estuarine and shelf sediments. The concentrations of total n-alkanes and fatty acids in the shelf surface sediments (0-2 cm) were 5-10 times higher than those in estuarine surface sediments but they all decreased rapidly to comparable levels below the surface layer. The compositions of w-alkanes in the estuarine sediments were dominated by C_(26)-C_(33) long-chain n-alkanes with a strong odd-to-even carbon number predominance. In contrast, the composition of n-alkanes in the shelf sediment was dominated by nC_(15) to nC_(22) compounds. Long-chain (> C_(20)) fatty acids (terrestrial biomarkers) accounted for a significantly higher fraction in the estuarine sediments compared to that in the shelf sediment, while short-chain (< C_(20)) saturated and unsaturated fatty acids were more abundant in the shelf surface sediments than in the estuarine sediments. Stable carbon isotopic ratios of individual fatty acids showed a general positive shift from estuarine to shelf sediments, consistent with the variations in bulk δ~(13)C_(TOC) TOC. These contrasts between the estuarine and shelf sediments indicate that terrestrial organic matter was mainly deposited within the Changjiang Estuary and inner shelf of ECS. Post-depositional diagenetic processes in the surface sediments rapidly altered the chemical compositions and control the preservation of organic matter in the region.
机译：为了检查东海（ECS）陆架沉积物中有机物的来源和保存，我们测量了体积C / N和同位素，有机生物标记物（正构烷烃和脂肪酸）和化合物特异性（脂肪酸）的稳定性从长江口附近的两个地点和ECS架子的一个地点收集的三个沉积物核心的碳同位素比。在河口和陆架沉积物之间观察到有机物的化学和同位素组成不同。架子表面沉积物（0-2厘米）中总正烷烃和脂肪酸的浓度比河口表面沉积物的总正烷烃和脂肪酸浓度高5-10倍，但它们都迅速下降到表层以下的相当水平。河口沉积物中正构烷烃的组成主要由C_（26）-C_（33）长链正构烷烃（具有奇数至偶数的碳数占优势）主导。相反，架子沉积物中正构烷烃的组成主要由nC_（15）至nC_（22）化合物决定。相较于陆架沉积物，长链（> C_（20））脂肪酸（陆地生物标志物）占河口沉积物的比例要高得多，而短链（

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