东海赤潮高发区沉积物柱状样中正构烷烃和脂肪醇的分布与来源

Distribution and Sources of n-alkanes and Fatty Alcohol in Core Sediments of Red Tide-frequent-occurrence Area in the East China Sea

选取了东海赤潮高发区4个站位的沉积物柱状样,通过测定δ13CTOC值,利用δ13C的双端元模型计算了沉积物中TOC的海源和陆源贡献率,并分析了正构烷烃和脂肪醇的组成与分布,探讨了其来源。结果表明,东海赤潮高发区沉积物中,正构烷烃以高碳数烷烃为主,有明显的奇碳优势,且呈双峰群分布;各站位总正构烷烃(T-ALK/$g/g)含量随深度有不同的变化;碳数奇偶优势指数(CPI)、陆源海源优势烷烃比(TAR)、平均链长(ACL)等正构烷分子指标,反映出在调查海区陆源正构烷烃的输入占主导,且以草本植物为主。直链烷基醇主要来源于陆地高等植物,4个站位的植醇经历了相似的生物化学过程,说明沉积环境较一致;菜籽甾醇与甲藻甾醇的比值指示了调查海区浮游植物种群的历史变化,由于水体富营养化的日益加重所导致的赤潮由简单的硅藻赤潮向硅藻甲藻混合型赤潮转变。

Sediment cores in four sites of the red-tide-frequent-occurrence area in East China Sea were selected and source apportionment was calculated using two end-member modeling for δ13CTOCto derive an inventory of marine versus terrestrial organic matter. The n-alkanes and fatty alcohols in sediment cores were analyzed to discuss composition,distribution and origins of organic matter. The results indicate that the n-alkanes have obvious advantages of longer carbon number,and the longer chain n-alkanes have a strong odd-over-even predominance and display bimodal distribution. Downhole variations of total n-alkanes( T-ALK /$g /g) contents are different among four cores. It is indicated by CPI,TAR,Pmar-aqand other n-alkanes that sedimentary organic matter is majorly from terrestrial inputs with predominance of herbaceous plants. The results of n-alkyl alcohol showed that organic matter mainly originated from terrestrial higher plants. The distribution of phytol in four stations are similar suggesting that they may experience through the similar biochemical process and the sedimentary environment may be relatively constant. Donwhole variation in the ratio of brassicasterol and dinoflagellatesterol indicates that red-tide blooms have changed from single diatom type into complex one with diatom and dinoflagellate due to deteriorated eutrophication.