珠江口外近海沉积有机质化学及稳定同位素组成的早期成岩改变

张凌; 陈繁荣; 杨永强; 张德荣

珠江口外近海沉积有机质化学及稳定同位素组成的早期成岩改变

1.
中国科学院南海海洋研究所, 广东, 广州, 510301
2.
中国科学院广州地球化学研究所, 广东, 广州, 510640

基金项目: 中国科学院知识创新工程重要方向性项目:珠江河口及近海生态环境演化规律与调控机制研究(ZKCX2-SW-212)

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出版历程
- 收稿日期: 2006-12-26
- 修回日期: 2008-07-29

Chemical and isotopic alteration of organic matter during early diagenesis:evidence from the coastal area offshore the Zhujiang Estuary in China

1.
South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China
2.
Guangzhou Institute of Geochemistry, Chinese Academy of Ciences, Guangzhou 510640, China

摘要

摘要: 理解早期成岩过程中有机质的化学和同位素分馏对于研究海洋和湖泊环境中的生物地球化学过程是很重要的。将珠江口外近海生物成因有机质分为可水解氨基酸、碳水化合物、脂类和酸不溶四个部分,分析了有机质的化学和同位素组成(δ¹³C,δ¹⁵N),借以讨论沉积有机质在埋藏的早期成岩过程中所发生的化学和同位素改变,结果表明,从浮游生物→悬浮颗粒物→表层沉积物→沉积柱内部,易降解组分可水解氨基酸、碳水化合物、脂类占样品总有机碳的份额依次降低。沉积物及四个有机部分的稳定碳同位素组成在纵向上随深度保持相对恒定,而在不同有机部分之间差异明显。不同类型有机物的分解速率差异在改变有机质化学成分的同时,导致其δ¹³C发生小幅度负向漂移;细菌有机质的形成和分解对有机质化学成分和同位素组成演化也有重要贡献,并且在一定程度上抵消了上述δ¹³C的负向漂移,其结果导致沉积有机质的δ¹³C略低于浮游生物;另一方面,由于异养菌生长过程中的氮同位素分馏系数与可利用氮源的特征和培养基的性质等多种因素有关,导致沉积物的δ¹⁵N变化范围增大。在这里δ¹³C可以可靠地指示该海域沉积有机质的来源,而δ¹⁵N变化范围较大且规律不明显,难以用作沉积有机质来源的指示。
- 有机碳含量 /
- 稳定碳、氮同位素组成 /
- 早期成岩 /
- 分馏 /
- 细菌 /
- 珠江口
Abstract: Under standing the chemical and isotopic alteration of organic matter duringearly diagenesis is crucial to the studies of biogeochemical processes in marine and lacustrine environments.The isotopic composition(δ¹³C and δ¹⁵N),total organic carbon(TOC)and total nitrogen(TN)contents of sediment cores as well as plankton and suspended particulates from the coastal area off shore the Zhujiang Estuary were determined,and the fractional carbon content of total hydrolysable amino acids(THAA),total carbo hydrates(TCHO),total lipid and acid-insoluble organic compounds(AIOC)and their respective δ¹³C were analyzed,based on which,the magnitude and mechanismof chemical and isotopic fractionation of organic matter were investigated.Results showed that the degradable fractions of THAA、TCHO and lipid decreased from plankt on to POM to surface sediments and to the buried sediments,and δ¹³C of TOC and organic fractions kept stable with depth,but differed distinctly among the four fractions.The different degradation rates oforganic compounds and the formation and degradation of bacteria organic matterare the major mechanisms causing the chemical and isotopic alteration oforganic matter duringearly diagenesis1 Because of the lower carbohydrate content in the plankton and the rapid degradation of lipid,the carbon isotopic fractionation caused by selective degradation of compounds could be relatively small and was partially canceled by the addition of bacterial synthesized organic matter,resultingin the observed conservative nature of δ¹³C duringearly diagenesis.On the other hand,the addition of bacteria organic matter may account for the depletion and variation of δ¹⁵N caused by early diagenesis.The above studies suggested that δ¹³C can be a reliable proxy to the sources of organic matter,but δ¹⁵N cannot be used to indicate the origin of sedimented o rganic matterin the study area.
- TOC /
- stable isotopic composition /
- early diagenesis /
- fractionation /
- bacteria activity /
- Zhujiang Estuary in China

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参考文献(22)

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