SOURCE OF SATURATED FATTY ACIDS IN MODERN SEDIMENTS IN SHENHU AREA, NORTHERN SOUTH CHINA SEA AND IMPLICATIONS: APPLICATION OF N-WEIGHTED AVERAGE CARBON ISOTOPE

The saturated fatty acids (SaFAs) in the surface sediments from the Shenhu Area, northern South China Sea were examined. The total SaFA concentrations are distributed within a range of 1.80-10.16 μg/g(μg FA/g dry sediment), and the carbon numbers range from C_12-32. The SaFAs follow an even-over-odd predominance distribution, with n-C₁₆ and n-C₁₈ being the two major components. In this paper, the samples above 90cm were combined into one sample to discuss the sources of SaFAs by n-average δ¹³C. The results revealed that short-chain fatty acids (n-C_12-18) have relatively positive n-average δ¹³C values from -26.7‰ to -28.2‰, suggesting the chemical autotrophic bacteria sources, while most long-chain fatty acids (n-C_21-23, n-C₂₅, n-C_29-32) have relatively negative n-average δ¹³C values from -29.6‰ to -34.1‰, suggesting the C₃ higher plant sources, and the other LcFAs (n-C₂₄ & n-C_26-28), as well as n-C₁₉ and n-C₂₀ mid-chain fatty acids have n-average δ¹³C from -26.1‰ to -29.3‰, suggesting the mixed marine and terrigenous sources. The lowest concentrations of terrigenous and marine inputs at depths of 75-80cm may be related to Younger Dryas event.