C1-C7 volatile organic compounds in sediments at DSDP Legs 56-57 Holes

Volatile C1-C7 components in sediments were examined for Japan Trench DSDP Sites 438, 439, 435, 440, 434 and 436, proceeding from west to east. Levels of all components are lowest in the highly fractured sediments of Sites 440 and 434. A number of alkenes, furans, and sulfur compounds were detected in concentrations higher than noted in any other DSDP sediments examined to date. The types, amounts, and specificity of occurrence are similar to those for 1-meter gravity cores we have examined which bear a significant biological imprint. Site 436 shows high levels of saturated and aromatic hydrocarbons, as well as olefins, including traces of dimethycyclopentanes and the highest level of cyclohexene detected in any DSDP sediment we have examined to date. The results from Site 436 were unexpected, considering the low organic-carbon content, absence of biogenic methane, and evidence of an aerobic depositional environment at this site.本研究按从西至东的顺序，对日本海沟深海钻探计划（Deep Sea Drilling Project，DSDP）438、439、435、440、434及436站位的沉积物中的挥发性C1-C7组分开展了分析检测。所有组分的含量在440与434站位的强破碎化沉积物中处于最低水平。本次检测中检出的多种烯烃（alkenes）、呋喃类化合物（furans）及含硫化合物（sulfur compounds），其浓度均高于迄今已分析过的其他所有DSDP沉积物中的对应组分浓度。上述组分的赋存类型、含量及分布特异性，与我们此前分析过的带有显著生物印记（biological imprint）的1米重力柱沉积物（gravity cores）样品特征高度一致。436站位沉积物中饱和烃（saturated hydrocarbons）、芳香烃（aromatic hydrocarbons）及烯烃（olefins）类组分含量均较高，其中检测到痕量二甲基环戊烷（dimethycyclopentanes），且其环己烯（cyclohexene）含量达到迄今我们分析过的所有DSDP沉积物中的最高值。结合该站位较低的有机碳含量、无生物成因甲烷（biogenic methane）产出以及存在有氧沉积环境（aerobic depositional environment）的相关证据，436站位的检测结果令人始料未及。