Abstract
The South Yellow Sea is an important carbon sink and a significant research area of carbon cycle. After studying the composition and distribution of n-alkanes in a 250 cm long sediment core in the northern part of South Yellow Sea, it can be found that all n-alkanes of sediment samples in this research are distributed in three types, that is, double peak groups, predominance of long-chain n-alkanes, and predominance of short-chain n-alkanes. The average values of∑C25−35/∑C15−21,∑C27+29+31/∑C15+17+19,∑C21-/∑C22+, and(C27+C29+C31+C33)/∑C14–38are 1.92, 4.22, 0.51, and 0.35, respectively; all above outcomes indicate significant predominance of terrigenous inputs. The average values of C31/C29 and ACL are 1.04 and 29.92, respectively; these results reflect that herbaceous plants and ligneous plants account for similar percentages in the sediment core samples. The average values of CPI1 of short-chain alkanes are 0.80, reflecting the apparent even predominance, which is the result of microbial degradation. The average values of CPI2 of long-chain alkanes of most samples are 2.77, reflecting the apparent odd predominance. The average values of CPI and Pr/Ph, as well as the Pr/nC17and Ph/nC18correlation diagram, reflect that the organic matter is immature and suggest reductive sedimentary environment.
Highlights
The organic carbon deposition rate of continental margin sea is 8–30 times higher than that of the ocean, and over 80% deposited organic carbon is buried in the continental shelf and continental slope area [1, 2]
The margin sea plays an important role in global carbon cycle [2]
The South Yellow Sea is typical semiclosed continental margin sea, into which a large amount of terrigenous matter was transported along streams since Holocene [5, 6]
Summary
The organic carbon deposition rate of continental margin sea is 8–30 times higher than that of the ocean, and over 80% deposited organic carbon is buried in the continental shelf and continental slope area [1, 2]. Organic matter source of the margin sea is an important scientific subject in the research on carbon cycle [3, 4]. Research on organic matter source of sediments in the Yellow Sea shows that nalkanes of South Yellow Sea are dominated by terrigenous inputs [5, 6, 21,22,23, 25, 26], and the terrigenous n-alkanes are mainly derived from higher plants waxiness [5]. Previous research on n-alkanes of organic matter in modern sediments of South Yellow Sea focuses on surface sediment samples [5, 6, 22, 23, 28]. This paper studies composition and distribution of n-alkanes of a 250 cm long sediment core in the northern part of South Yellow Sea and analyzes the geochemical significance
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