海南八门湾红树林柱状沉积物中有机生物标志物的分布和降解

Composition and degradation of lipid biomarkers in mangrove forest sediments of Hainan Island,China

对海南岛红树林柱样中有机生物标志物等生物地球化学参数进行了初步研究。结果显示红树林中有机碳(OC)与总氮(TN)比值范围为5.35—7.47,碳稳定同位素(δ13C)值范围为?25‰—?22.9‰。脂肪酸与正构烷烃浓度分布范围分别为7.8—21.8μg.g?1(干重)和3.2—25μg.g?1(干重)。在表层沉积物中,红树林植物、细菌与浮游生物的脂肪酸生物标志物各占总脂肪酸的25.4%、12.9%和7.5%,结合较低的OC/TN比值和较高的δ13C值,表征了当地微生物和外源浮游植物的有机质贡献。各类脂肪酸在柱样中表现出不同的降解特征:多不饱和脂肪酸(PUFAs)优先被降解,而长链脂肪酸(LCFAs)则较为稳定,没有明显的降解。碳优势指数(CPI)和平均碳链长度(ACL)显示,埋藏深度越深,有机物的生物化学改造程度越大。

A series of organic biomarkers were analyzed,which was from a core sample collected in the mangrove sediment near the Bamen Gulf in Hainan Island to investigate source and degradation of organic matters in the sediment.The percentage of organic carbon（OC%）,the percentage of total nitrogen（TN%）,OC/TN ratio,δ13C value,and specific biomarkers were determined using the sample.Concentrations of total fatty acids ranged from 7.8 to 21.8 μg.g？1（dry weight）.High portions of bio-source organic matters were derived from micro-organism,with large contributions of bacteria and plankton derived fatty acids（12.93% and 7.45% of total fatty acids,respectively）,proved by low C/N ratio（5.35？7.47） and low δ13C value（？25‰ to ？22.9‰）.Polyunsaturated fatty acids（PUFAs） with high degradation rate were lost fastest during decomposition.Long chain fatty acids（LCFAs） were relatively stable and shown no significant difference during degradation.The carbon preference index（CPI）and the n-alkane average chain length（ACL） indicated organic matter generally became more mature in deeper sediments.