长江口表层沉积物中正构烷烃的高分辨分布特征及有机碳来源解析

王春禹; 姚鹏; 赵彬

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王春禹,姚鹏,赵彬.长江口表层沉积物中正构烷烃的高分辨分布特征及有机碳来源解析[J].海洋学报,2020,42(10):1-13

长江口表层沉积物中正构烷烃的高分辨分布特征及有机碳来源解析

High-resolution distribution of n-alkanes and source apportionment of organic carbon in surface sediments of the Changjiang River Estuary

投稿时间：2020-02-08 修订日期：2020-05-02

DOI：10.3969/j.issn.0253-4193.2020.10.001

中文关键词: 长江口沉积有机碳正构烷烃高分辨来源和分布

英文关键词:Changjiang River Estuary sedimentary organic carbon n-alkanes high-resolution source and distribution

基金项目:国家自然科学基金重点国际（地区）合作研究项目（41620104001）；国家自然科学基金面上项目（41676063）。

作者	单位	E-mail
王春禹	中国海洋大学海洋化学理论与工程技术教育部重点实验室，山东青岛 266100
姚鹏	中国海洋大学海洋化学理论与工程技术教育部重点实验室，山东青岛 266100 青岛海洋科学与技术试点国家实验室海洋生态与环境科学功能实验室，山东青岛 266237	yaopeng@ouc.edu.cn
赵彬	中国海洋大学海洋化学理论与工程技术教育部重点实验室，山东青岛 266100

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中文摘要:

于2014年3月对长江口及邻近海域的表层沉积物进行了高分辨率采样，分析了沉积物粒级组成、比表面积、总有机碳含量及其稳定碳同位素组成(δ¹³C)、正构烷烃及其相关分子指标，讨论了此区域沉积有机碳和正构烷烃的高分辨分布特征，并结合基于主成分分析-蒙特卡洛模拟的三端元混合模型，对沉积有机碳的来源进行了定量解析。结果表明，长江口及其邻近海域表层沉积物中总有机碳含量为0.45%±0.16%，近岸泥质区总有机碳含量较高，外海砂质区含量较低。总正构烷烃(C₁₄-C₃₅)的绝对含量和相对于总有机碳的含量分别为(1.42±0.73) μg/g和(0.34±0.21) mg/g。泥质区以长链正构烷烃占优势，具有较强的奇碳优势；砂质区以短链正构烷烃占优势，且具有一定的偶碳优势。长江输入、老黄河口输入、闽浙沿岸小型河流输入和水动力分选等因素制约了正构烷烃的输运和分布特征。模型结果显示此区域沉积有机碳来自海源、土壤和高等植物的混合输入，其中以海源为主，其贡献为42.70%±18.18%，由陆地向外海贡献逐渐升高，其次是土壤和高等植物，其贡献分别为28.99%±15.37%和28.31%±17.12%。在水动力分选作用的影响下，两种陆源有机碳在入海之后的输运过程中存在明显的分异，土壤有机碳主要与细颗粒物结合，并沿闽浙沿岸向南输运，而高等植物来源有机碳则在长江口存在东北方向的输运。

英文摘要:

Surface sediments were collected by high-resolution sampling from the Changjiang River Estuary and its adjacent shelf in March, 2014. Grain size composition, Specific Surface Area (SSA), Total Organic Carbon (TOC) and stable carbon isotope composition (δ¹³C), n-alkanes and its related indices in sediments were analyzed to discuss the high-resolution distribution patterns of sedimentary organic carbon (OC) and n-alkanes in this region. A three end-members mixing model based on Principal Component Analysis (PCA) and Monte-Carlo Simulation was constructed to characterize the sources of sedimentary OC quantitatively. The results showed that TOC contents were 0.45%±0.16%, which were relatively higher in coastal mud area than offshore sandy area. Absolute contents (Σn-Alk) and relative contents (Σn-Alk/TOC) of total n-alkanes (C₁₄ to C₃₅) were (1.42±0.73) μg/g and (0.34±0.21) mg/g , respectively. There was a strong odd to even carbon preference of long-chain n-alkanes in muddy sediments, while there was an even to odd carbon preference of short-chain n-alkanes in sandy area. Inputs from the Changjiang River, the Old Yellow River Estuary and small rivers in the Zhe-Min coasts and hydrodynamic sorting restricted the transport and dispersal patterns of n-alkanes. The results of the three end-members mixing model indicated a mixture input of marine, soil and higher plant derived OC in this region. Among them, sedimentary OC was dominated by marine source (42.70%±18.18%), increasing from coast to outer sea gradually. Contributions of soil OC and higher plant OC were 28.99%±15.37% and 28.31%±17.12%, respectively. Influenced by hydrodynamic forces, obvious differentiation of these two terrestrial OC pools occurred during transport after entering into ocean. Soil OC was mainly associated with fine grains, and was transported southward along the Zhe-Min coast, while higher plant derived OC was mainly transported along northeast direction in the Changjiang River Estuary.

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