The Stable Carbon Isotopic Compositions of n-Alkanes in Sediments of the Bohai and North Yellow Seas: Implications for Sources of Sedimentary Organic Matter

Stable carbon isotopic compositions of n-alkanes in surface sediments of the Bohai and North Yellow Seas were investigated to elucidate sources of sedimentary organic matter in these seas. The long-chain n-alkanes in surface sediments are predominantly long-chain C-27, C-29, and C-31 types, with obvious odd carbon predominance. The delta C-13 values of long-chain n-C-27, n-C-29, and n-C-31 alkanes are -30.8%+/- 0.59 parts per thousand, -31.9%+/- 0.6 parts per thousand, and -32.1%+/- 1.09 parts per thousand, respectively, within the range of n-alkanes of C-3 terrestrial higher plants. This suggests that sedimentary n-alkanes are derived mainly from terrestrial higher plants. Compound-specific carbon isotopic analysis of long-chain n-alkanes indicates that C-3 terrestrial higher plants predominate (64%-79%), with angiosperms being the main contributors. The n-alkane delta C-13 values indicate that mid-chain n-alkanes in sediments are derived mainly from aquatic emergent macrophytes, with significant petroleum pollution and bacterial degradation sources for short-chain n-alkanes.

Automated summary

Stable carbon isotopic compositions of n-alkanes in surface sediments of the Bohai and North Yellow Seas show that terrestrial higher plants are the main source of sedimentary organic matter, with angiosperms being the major contributors. On the other hand, mid-chain n-alkanes in sediments are mainly derived from aquatic emergent macrophytes, with significant petroleum pollution and bacterial degradation sources for short-chain n-alkanes.