长江口柱状沉积物中甾醇的组成特征及其地球化学意义

The distributions and geochemistry of sterols in core sediment from the Changjiang Estuary in China

通过对长江口两个柱状沉积物中有机质的GC-MS分析,检出C27—C29甾烷醇、C27Δ5,C28Δ7和C29Δ22甾烯醇以及C30Δ22烯醇(4α,23,24-三甲基-5α-胆甾-22-烯醇)7种主要甾醇生物标志化合物.8站位沉积物中以陆源输入为主的C29甾醇的相对丰度最高,在17站位深层沉积物中也以C29甾醇为主,而其表层沉积物中则是以海洋浮游动物输入为主的C27甾醇的相对丰度最高.在所有的样品中甾醇都经历了较强的加氢还原作用,相同碳数的甾烷醇的相对丰度远远高于其相对应的甾烯醇的相对丰度.随着沉积深度的增加,甾烯醇的加氢还原作用越强,且由于两个站位不同的沉积环境,8站位甾烯醇的加氢还原作用更强.

Two core sediments, from the Changjiang Estuary, China, were analyzed for sterols. Severn sterols named as cholest-- 5 -- en-- 3β-- ol, 5α- cholestan-- 3β-- ol, 24 -- methyl -- cholest -- 7 -- en-- 3β-- ol, 4 ： 24--methyl-- 5α- cholestan-- 3β-- ol, 24-- ethyl-- cholest-- 22en-- 3β-- ol, 24-- ethyl-- 5 α- cholestan-- 3β-- ol and 4α, 23,24-- trimethyl-- 5α- cholest-- 22en-- 3β-- ol were identified by means of GC-- MS analysis. The relative abundance of C29 sterols, which mainly originate from terrigenous input, is the highest in all the sediment from Site 8. In Site 17, the relative abundance of C27 sterols mainly from zooplankton input is the highest in the surface sediment, while that of C29 sterols is the highest downwards. In all the samples, the relative abundances of sterols are much higher than those of sterols at the same carbon number for the strong hydrogenation. The reductive hydrogenation of sterols is stronger downward with the depth, and that is much stronger in Site 8 than in Site 17 due to the different sedimentary circumstances.