中文摘要：

利用气相色谱法对南海北部和海南岛附近海域表层沉积物中正构烷烃（n-alkanes）和脂肪酸进行测定和分析,结合粒径、比表面积（specific surface area,SSA）、有机碳（OC%）、碳稳定同位素（δ~（13）C）等参数研究有机物来源和降解状态,并对其影响因素进行分析。研究结果表明：沉积物主要以粉砂为主,平均粒径分布范围在10.97—517.21μm之间,选取的16个站位的比表面积平均值为8.05m~2/g,最大值是S23站位的24.46m~2/g,最小值是S29站位的1.73m~2/g,OC%含量在0.15—1.18之间,δ~（13）C值为–23.05‰—–21.24‰。沉积物中正构烷烃碳链的分布范围是nC_（14）—nC_（33）,低碳数峰群以nC_（16）、nC_（18）为主峰碳且具有偶碳数优势,高碳数峰群以nC_（29）为主峰碳。脂肪酸的碳数分布范围是nC_（14）—nC_（30）,低碳数单峰型分布,短链饱和脂肪酸（short chain saturated fatty acids,SCSFA）和单不饱和脂肪酸（monounsaturated fatty acids,MUFA）的含量占总脂肪酸含量的70%以上,长链饱和脂肪酸（long chain saturated fatty acids,LCSFA）的含量不到10%,据此说明这两个区域有机质均以海源输入为主。在有机物保存和降解方面,海南岛附近海域有机质载荷（OC/SSA）和δ~（13）C之间的正相关,表现了良好的陆源和海源的有机物更替,但是珠江口附近海域系列样品却未见相似过程。不仅在物源更替方面,在有机质降解特征上珠江口附近海域中的有机物与海南岛附近海域和南海陆架深水区也有很大的差别。海南岛附近海域和南海陆架深水区有机质的降解符合一般规律,随着水深的增加降解程度逐渐变大,然而珠江口附近海域随着水深的增加有机质却越来越＂新鲜＂。结合前人对珠江口附近海域黏土矿物组成的研究,本文认为珠江口附近海域沉积物中有机质之所以会出现上述＂异常＂可能是因为该研究区域黏土矿物?

英文摘要：

The South China Sea receives sediments from multiple sources of adjacent lands and islands and hosts rich in fossil fuel resources. To understand organic carbon （OC） origination, transportation, and degradation in water and sediment, surface sediments were sampled in two maritime regions, i.e., the northern South China Sea along Zhujiang （Pearl） River delta （ZJ） and waters to the east of Hainan Island （HN）, two major marine oil-gas productive fields of China. Sedimentological （grain size, specific surface area （SSA）） and geochemical （OC%, δ13C-OC and n-alkanes, fatty acids） studies were performed. Samples were mostly fine-grained sand-silt sediments and showed a tendency of fining away from land. Parameters of OC% （0.15-1.18）, δ13C （-23.05‰--21.24‰） were determined, and molecular biomarkers （n-alkane carbon preference index and types of fatty acids） were measured. Correlation between SSA and OC% was not significant. Correlation between OC load （OC/SSA） and δ13C in HN samples was positive, showing good transition from terrestrial to marine origination from land to ocean, which is normal; however, this phenomenon was not observed in the ZJ samples. We believe that the difference shall be resulted from selective adsorption by clay minerals different in species and fraction between the two sets of samples. ZJ samples are affected by multiple sources from South China continent, Taiwan and Luzon Islands, while that of HN from nearby single Hainan Island.