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Predictive isotopic biogeochemistry: Hydrocarbons from anoxic marine basins
Organic Geochemistry ( IF 3 ) Pub Date : 1994-06-01 , DOI: 10.1016/0146-6380(94)90009-4
K H Freeman 1 , S G Wakeham , J M Hayes
Affiliation  

Carbon isotopic compositions were determined for individual hydrocarbons in water column and sediment samples from the Cariaco Trench and Black Sea. In order to identify hydrocarbons derived from phytoplankton, the isotopic compositions expected for biomass of autotrophic organisms living in surface waters of both localities were calculated based on the concentrations of CO2(aq) and the isotopic compositions of dissolved inorganic carbon. These calculated values are compared to measured delta values for particulate organic carbon and for individual hydrocarbon compounds. Specifically, we find that lycopane is probably derived from phytoplankton and that diploptene is derived from the lipids of chemoautotrophs living above the oxic/anoxic boundary. Three acyclic isoprenoids that have been considered markers for methanogens, pentamethyleicosane and two hydrogenated squalenes, have different delta values and apparently do not derive from a common source. Based on the concentration profiles and isotopic compositions, the C31 and C33 n-alkanes and n-alkenes have a similar source, and both may have a planktonic origin. If so, previously assigned terrestrial origins of organic matter in some Black Sea sediments may be erroneous.

中文翻译:

预测同位素生物地球化学:来自缺氧海洋盆地的碳氢化合物

对来自卡里亚科海沟和黑海的水柱和沉积物样品中的单个碳氢化合物进行了碳同位素组成测定。为了识别来自浮游植物的碳氢化合物,根据 CO2(aq) 的浓度和溶解的无机碳的同位素组成,计算了生活在两地地表水中的自养生物的生物量预期的同位素组成。这些计算值与颗粒有机碳和单个碳氢化合物的测量 delta 值进行比较。具体来说,我们发现番茄红素可能来自浮游植物,而双萜来自生活在好氧/缺氧边界之上的化学自养生物的脂质。三种被认为是产甲烷菌标志物的无环类异戊二烯,五甲基二十烷和两种氢化角鲨烯具有不同的 delta 值,显然不是来自共同的来源。根据浓度分布和同位素组成,C31 和 C33 正构烷烃和正构烯烃具有相似的来源,并且都可能来自浮游生物。如果是这样,先前指定的一些黑海沉积物中有机物的陆地来源可能是错误的。
更新日期:1994-06-01
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