南海北部神狐海域现代沉积物正构脂肪酸来源:加权平均碳同位素的建立与应用

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

对南海北部神狐海域表层沉积物中脂肪酸组分进行了分析,检测到的总正构脂肪酸含量为1.80~10.16μg/g(μg脂肪酸/g干沉积物),碳数分布为C12—C32,呈偶奇优势分布,以C16和C18为主峰碳。将90cm以上层位样品进行归一化,建立加权平均碳同位素讨论正构脂肪酸来源,结果表明,短链脂肪酸(n-C14~18)具有较正的碳同位素组成(加权平均为-26.7‰^-28.2‰),反映了化学自养细菌来源;大部分长链脂肪酸(n-C21~23,nC25,n-C29~32)具有偏负的碳同位素组成(加权平均为-29.6‰^-34.1‰),反映了陆源C3高等植物来源;而另外的长链脂肪酸(n-C24&n-C26~28)和n-C19~20中链脂肪酸(加权平均碳同位素为-26.1‰^-29.3‰)则可能反映了混合来源输入。沉积物75~80cm层位陆源输入和海洋输入含量达到最低,可能和Younger Dryas冷期旋回事件有关。

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 C12 32. The SaFAs fol- low an even over odd predominance distribution, with n-C16 and n-C18 being the two major compo- nents. In this paper, the samples above 90cm were combined into one sample to discuss the sources of SaFAs by n average δ13 C. The results revealed that short-chain fatty acids （n-C12-18） have relatively positive n-average δ3C values from --26.7‰ to --28.2‰, suggesting the chemical autotrophic bacte- ria sources, while most long-chain fatty acids （n-C21-23, n-C25, n-C29-32） have relatively negative n-aver- age δ3C values from --29.6‰ to --34. 1‰, suggesting the C3 higher plant sources, and the other LcFAs （n-C24 ＆ n-C26 28）, as well as n-C19 and n-C20 mid-chain fatty acids have n-average δ13C from -- 26.1%0 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.