长江口表层沉积物中有机碳的来源、分布与成岩状态  

Sources,Distribution and Diagenetic State of Sedimentary Organic Carbon in The Changjiang Estuary

作　　者：赵彬[1,2] 姚鹏[1,3,4] 潘慧慧[1,2] 张婷婷[1,2] 李栋[1,2] 王金鹏[1,2] 

机构地区：[1]中国海洋大学海洋化学理论与工程技术教育部重点实验室,山东青岛266100 [2]中国海洋大学化学化工学院,山东青岛266100 [3]海洋科学与技术青岛协同创新中心,山东青岛266100 [4]中国海洋大学海洋有机地球化学研究所,山东青岛266100

出　　处：《中国海洋大学学报（自然科学版）》2015年第11期49-62,共14页Periodical of Ocean University of China

基　　金：国家自然科学基金面上项目(41176063);国家自然科学基金重大国际(地区)合作研究项目(40920164004);国家自然科学基金创新研究群体项目(41221004)资助

摘　　要：在长江口及其邻近海域采集了表层沉积物样品,分析了粒级组成、有机碳(OC)含量及其稳定同位素丰度(δ13 C)、木质素和沉积色素含量和相关指标,并结合基于蒙特卡洛模拟的三端元混合模型,讨论了此区域沉积有机碳的来源、分布和成岩状态。结果表明,长江口表层沉积物中OC含量为0.21%~0.63%,长江口泥质区和浙闽沿岸OC含量较高,而河口外陆架上含量较低;δ13C为-23.1‰^-20.9‰,显示沉积有机碳是海洋和陆地来源的混合。木质素含量(Λ8)为0.16~1.41mg/100mg OC,其组成特点显示了木质素的草本和木本被子植物的混合来源。沉积色素以叶绿素的降解产物为主,主要分布在河口外陆架上;类胡萝卜素中以岩藻黄素为主,表明硅藻是此区域浮游植物的优势类群。以δ13 C和Λ8为来源指标的端元混合模型显示长江口沉积有机碳主要来自海洋浮游植物,其贡献为54.3%~88.1%(平均70.2%),从河口向陆架逐渐升高,其次是土壤(9.3%~32.1%,平均22.3%)和C3维管植物(2.7%~13.6%,平均7.5%),两者贡献均在长江口和浙闽沿岸附近较高。沉积物粒级组成、OC含量、δ13C丰度和生物标志物含量之间显著的相关性和分布一致性表明水动力分选过程在决定陆源OC(包括土壤和C3维管植物OC)在河口外的输运和分布中发挥了重要作用。富含木质素的新鲜植物碎屑主要与粗颗粒物相联系,并主要沉积在河口附近,而贫木质素的土壤有机碳则主要赋存在细颗粒物上,可输运到离河口较远的位置。木质素降解参数,如酸醛比、3,5-Bd/V和P/(S+V)在长江口外陆架上的砂质区域相对较高,显示此区域陆源有机碳降解程度较高,而叶绿素降解产物的比例在长江口泥质区较高,则可能与泥质沉积物中较强的有机碳再矿化作用有关。The sources and fate of sedimentary organic carbon（SOC）in LDEs play a critical role in controlling the global carbon cycle.Surface sediments were collected from the Changjiang Estuary and its adjacent sea.Grain size composition,OC and stable carbon isotope composition,lignin-phenols and pigments were analyzed by combining the results of three end-member mixing model based on Monte-Carlo Simulation to discuss the sources,distribution and diagenetic state of SOC.The results showed that OC content of surface sediments from Changjiang Estuary ranged from 0.21% to 0.63%.Theδ13 C of TOC in this study ranged from-23.1‰ to-20.9‰,indicating a mixture of terrestrial and marine derived OC.The OCnormalized lignin phenols（Λ8）ranged from 0.16 to 1.41mg/100 mg OC and its composition characteristics showed that they originated from a mixture of woody and nonwoody angiosperms.The dominant fraction of sedimentary pigments was degradation products of chlorophyll and mainly distributed in outer shelf.The main fraction of carotenoid was fucoxanthin,indicating that diatoms were dominant species in the study area.Based on the three end-member mixing model,the contribution of marine OC increased from 54.3%in the river mouth to 88.1%in the outer shelf with an average of 70.2%.The contributions of soil（9.3to 32.1%,22.3%in average）and C3 vascular plant（2.7to 13.6%,7.5%in average）were relatively small and both were higher in the Changjiang Estaury and Zhe-Min coast.Significant correlation and coincidence in the distribution of grain size composition,OC,δ13Cand biomarker concentrations showed that hydrodynamic sorting processes play an important role on the transport of terrestrial OC.Fresh and lignin-rich terrestrial high plant debris mainly associated with coarse particles and settled on the estuary,whereas lignin-poor soil-derived OC mainly associated with fine particles and can be transported far away from estuary.The lignin degradation indices,such as ratios of acid and aldehyde,3,5-Bd/V and P/（S＋V）were rela

关 键 词：长江口 沉积有机碳 来源 水动力分选 早期成岩作用 

分 类 号：P734.5[天文地球—海洋化学]