鸭绿江河口西岸潮滩沉积物有机质对流域变化的响应

摘要

Riverine particle organic matter (POM)contains key information about terrestrial carbon cycle,and hu-man activities.The basin changes and interaction,between land and sea,can be reflected by the variation of organic matter in sediment from estuary.Four sediment cores and 23 surface samples were collected in tidal flat of west bank of Yalu Estuary in twice from 2010 to 2011.The elemental and C-and N-isotopic compositions of organic matter (OM)were determined,together with sediment grain size.The analysis results show that relationship be-tween TOC/TN andδ13 C decrease,as well as correlation betweenδ15 N and sediment grain size from estuary to west,indicating that reconstruction degree of OM get further and the source of OM get complicated.We useδ13 C to analysis OM’s source and its transport as the principal line,TOC/TN as auxiliary,and useδ15 N to evaluate ecologi-cal environment.The variations ofδ13 C in sediment cores are closely related with river sediment load.Intercepted by dams,the sediment load decreased gradually,causing the deposition rate of tidal flat getting slow,and increasing the marine OM content in sediment.Variation ofδ15 N in core sediment indicates the increasing sewage discharge. Otherwise,the rapid deposition rate in West Chanel Estuary reduced theδ13 C in surface sediments from land to sea. And the material,transported from sub-tidal and enriched in inter-tidal,caused theδ13 C increasing in landward di-rection in west tidal flat of Yalu Estuary.%河流颗粒有机质提供了陆地碳循环的重要信息以及人类活动的记录，通过河口地区沉积物有机质组成，可反映流域变化及海陆间相互作用。2010－2011年分两次于鸭绿江河口西岸潮滩采集柱样4根及表层样23个。对样品进行有机质碳氮总量（TOC、TN）、碳氮同位素（δ13 C、δ15 N）及沉积物粒度测试。分析结果表明，由河口向西，有机质受改造程度加深且来源逐渐复杂化，致 TOC／TN 与δ13 C的相关性逐渐降低，δ15 N 与沉积物粒度的相关性也随之降低。文中以δ13 C 为主线探讨沉积物有机质的来源及运移，TOC／TN 作为辅助，δ15 N 则用于指示生化条件的改变。柱样的δ13 C 分布与河流入海输沙密切相关，水库对入海泥沙的拦截，致河口潮滩沉积速率减缓，从而增加了沉积物中海源有机质的含量，δ13 C 随之增加。潮滩西侧柱样的δ15 N 增加指示了生活工业污水的大量排放。此外，表层样δ13 C 分布的方向性，指示了西水道门口处的快速堆积及潮下带物质的向岸运移，并在西岸潮滩向岸一侧富集。