Distribution and sources of n-alkanes in sediments in the Fangchenggang sea area
n-alkanes,exhibiting stable chemical properties,are ubiquitous in nature.They are favorable indicators of the source of or-ganic matter.Using the gas chromatography-mass spectrometry(GC/MS),this study detected n-alkanes in the surface sediments sam-pled 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:① The 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;② They 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;③ The terrestrial-marine alkane ratio(ΣT/ΣM),carbon predominance index(CPI),and terrestrial-marine alkane predominance ratio(TAR)all indi-cate a significant terrestrial influence on n-alkanes in the Fangchenggang sea area;④ The average chain length(ACL),alkane index(AI),and Pmar-aq further suggest that n-alkanes were mainly from terrestrial herbs;⑤ The T-ALK/C16 ratio implies that the Fangchenggang sea area experienced oil pollution;⑥ The pristane/phytane ratio(Pr/Ph)reveals that n-alkanes in the sediments of the Fangchenggang sea area formed in an oxidizing environment.
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