Distribution and sources of lipid compound series in sediment cores of the southern South China Sea

Tahir, N Mohd; Pang, S. Y.; Simoneit, B. R. T.

Distribution and sources of lipid compound series in sediment cores of the southern South China Sea

2015

Tahir, N Mohd | Pang, S. Y. | Simoneit, B. R. T.

Three short sediment cores from inner continental shelf of the southern South China Sea (5–50 km) off Terengganu were analyzed for lipid contents (i.e., homologous aliphatic compounds and sterols) using gas chromatography-mass spectrometry. The concentrations of the total aliphatic hydrocarbons (TAHs) ranged from 0.152 to 6.91 μg/g dry weight. The n-alkane distribution was from nC₁₃to nC₃₆, with a carbon preference index (CPI₁₃–₃₅) from 1.08 to 4.28 and a carbon number maximum (Cₘₐₓ), depending on a sample, at 31 or 18. In addition, a strong odd-to-even carbon number predominance was observed in nC₂₅–nC₃₅range. The distribution of the n-alkanoic acids and n-alkanols in all samples exhibited an even-to-odd carbon number predominance and ranged from C₁₀to C₂₆and from C₁₂to C₃₄, respectively. The n-alkanols were dominated by the long-chain homologs with Cₘₐₓat 22; on the other hand, the n-alkanoic acid distributions showed a predominance of short-chain homologs with a Cₘₐₓat 16. The total sterol concentrations ranged from 0.41 to 3.57 μg/g dry weight. Cholesterol was most abundant at the offshore stations, whereas sitosterol was dominant at near-shore station. Pentacyclic triterpenoids such as friedelin and taraxerol α- and β-amyrins, which are known biomarkers for higher plants, were detected at all stations with a dilution trend offshore. In conclusion, the marine sediments off southern Terengganu can still be considered uncontaminated, where the compound sources are biogenic from terrestrial plants superimposed with a marine productivity input.

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