防城港海域沉积物中正构烷烃分布和来源解析

Distribution and sources of n-alkanes in sediments in the Fangchenggang sea area

正构烷烃由于其化学性质稳定,在自然界中普遍存在,是表征有机质来源的良好标志物。利用气质联用仪(GC/MS)对2021年9月采集的防城港海域表层沉积物中的正构烷烃进行检测,对其含量、分布特征进行分析,运用特征参数对其来源进行解析。结果表明:正构烷烃含量在(67.51~850.08)×10^(-9)(干重)之间,均值为476.69×10^(-9)(干重),高值区主要分布在企沙半岛南部海域;主要由连续分布的n-C14~n-C35正构烷烃同系物组成,呈双峰分布,前峰群偶碳数优势,后峰群奇碳数优势;陆、海源烷烃比(ΣT/ΣM)、碳优势指数(CPI)和陆、海源烷烃优势比(TAR)均指示研究区正构烷烃受陆源影响明显;平均链长(ACL)、烷烃指数(AI)和Pmar-aq进一步表明其主要来源于陆源草本植物;T-ALK/C16比值表明研究海域受到石油污染影响;姥鲛烷和植烷比值(Pr/Ph)表明研究海域沉积物中正构烷烃形成于氧化环境。

n-alkanes,exhibiting stable chemical properties,are ubiquitous in nature.They are favorable indicators of the source of organic matter.Using the gas chromatography-mass spectrometry(GC/MS),this study detected n-alkanes in the surface sediments sampled from the Fangchenggang sea area in September 2021.It analyzed their content and distribution,as well as their source based on characteristic parameters.The results are as follows:①The n-alkanes of the Fangchenggang sea area manifested a content range of(67.51~850.08)×10^(-9)(dw),averaging 476.69×10^(-9)(dw),with high values primarily distributed in the southern sea area of Qisha Peninsula;②They were principally composed of extensive n-C14~n-C35 n-alkane homologues in a bimodal distribution.The former peak group displayed an even-carbon number advantage,while the latter showed an odd-carbon number advantage;③The terrestrialmarine alkane ratio(ΣT/ΣM),carbon predominance index(CPI),and terrestrial-marine alkane predominance ratio(TAR)all indicate a significant terrestrial influence on n-alkanes in the Fangchenggang sea area;④The average chain length(ACL),alkane index(AI),and Pmar-aq further suggest that n-alkanes were mainly from terrestrial herbs;⑤The T-ALK/C16 ratio implies that the Fangchenggang sea area experienced oil pollution;⑥The pristane/phytane ratio(Pr/Ph)reveals that n-alkanes in the sediments of the Fangchenggang sea area formed in an oxidizing environment.