四海龙湾表层沉积物中有机质的组成特征及其源解析

为研究玛珥湖四海龙湾表层沉积物中有机质的组成特征及来源,采集四海龙湾表层沉积物样品,并对其中的有机质进行了分析. 结果表明,四海龙湾表层沉积物中w(TOC)(TOC为总有机碳)为6.7%、w(TN)为0.6%、δ13C_org(TOC同位素丰度)为-28.0‰、δ15N_total(TN同位素丰度)为2.2‰. 可溶性有机质主要包括脂肪烃、脂肪醇、脂肪酸和GDGTs(甘油二烷基甘油四醚脂)等,其中脂肪酸是可溶性有机质的主要组分,约占可溶性有机质总量的68.8%,主要来源于内源性的藻类和厌氧菌； 脂肪烃主要来源于陆源的C3木本植物；结合态脂肪醇具有明显的内源来源特征,而游离态脂肪醇却呈现陆源来源特征. 四海龙湾沉积物中含有丰富的GDGTs,主要来源于陆源土壤,包括支链类GDGTs和类异戊二烯类GDGTs,其中类异戊二烯类GDGTs以GDGTⅣ和GDGTⅤ为主,但其在四海龙湾沉积物中的含量相对较小. 研究显示,四海龙湾流域陆源是沉积物中可溶性有机质的主要来源,陆源有机质的大量流入改变了四海龙湾的营养水平；不同种类可溶性有机质表现出不同的来源特征,这主要是由于微生物对不同种类有机质降解速率的不同所致,并且导致降解所产生的二次有机质数量也不同. 

Composition and Source Identification of Organic Matter in Surface Sediments of Lake Sihailongwan, China

The total organic carbon (TOC, 6.7%), total nitrogen (TN, 0.6%), δ13C_org (-28.0‰), δ15N_total (2.2‰), aliphatic hydrocarbons, fatty alcohols, fatty acids and glycerol two alkyl glyceryl ether lipids (GDGTs) were determined in surface sediments in Lake Sihailongwan Maar, in order to investigate the composition and sources of the organic matter. The results indicated that fatty acids were the main component of the dissolved organic matter in the sediments of the lake, accounting for 68.8% of TOC, which were mainly endogenous algae and bacteria. The aliphatic hydrocarbons were mainly from terrestrial sources, with C3 plants being major contributors. The bound alcohols were mainly from endogenous sources, while the free alcohols were mainly from terrigenous sources. The GDGTs, including branched GDGTs and isoprenoids GDGTs, were rich in the sediments of Lake Sihailongwan, and were mainly from the terrestrial soil. The isoprenoids GDGTs were dominated by GDGTs Ⅳ and Ⅴ, but their contents were limited in the surface sediments of the lake. The present study indicated that the organic matter from the watershed of Lake Sihailongwan was the major source in the surface sediments, while the influx of terrigenous organic matter was the main reason for the eutrophication level changes. The different kinds of dissolved organic matter showed different source characteristics, which was mainly attributed to the different degradation rates for microbes to different kinds of organic matter. In addition, the number of secondary organic matter from microbial degradation was also different.