【作者】 蒲晓强；

【导师】 钟少军；

【作者基本信息】 中国科学院研究生院（海洋研究所） ， 海洋地质学， 2005， 博士

【摘要】 硫是海水的主要化学组分之一。硫在海洋沉积物成岩过程中的生物地球化学反应和循环导致了地球表面的氧化还原环境和大气组分的地质历史演化,直接影响和控制了海洋碳循环和一系列化学元素-尤其是对海洋生态环境有重要影响的重金属元素的海洋生物地球化学循环。另外,鉴于海洋硫循环和碳循环之间的密切关系,对硫循环的研究将对我们了解和探测埋藏在大陆坡沉积物深部的人类21世纪的新型能源-天然气水合物有重要意义。因此,海洋沉积物早期成岩过程中硫的生物地球化学循环很久以来一直是国际海洋研究的重点之一,在我国近年来也逐渐受到关注。本论文利用取自黄海陆架、胶州湾李村河口及南海陆坡三处不同沉积环境中的沉积物样品,用冷扩散法分析了沉积物中酸可溶硫化物(AVS)的含量,用逐级提取法分析了沉积物中黄铁矿的含量,结合沉积物粒度、有机质、活性铁、黄铁矿硫同位素及孔隙水中常量组分离子浓度等数据,并参考前人在东海所作的硫化物方面的工作,对中国不同典型海域沉积环境下,沉积物早期成岩硫循环过程中硫化物的形成及其主要控制因素进行了探讨。通过对胶州湾李村河口沉积物中痕量金属活性组分与黄铁矿化金属组分的分析,结合其与硫化物的关系,探讨了沉积物中AVS向黄铁矿的转化,以及痕量金属在AVS和黄铁矿组分中的分布。通过分析黄海沉积物中活性金属的分布特征,讨论了其对环境氧化还原条件的响应,从而有助于对硫循环中硫化物分布特征的理解。通过对南海NH-1孔沉积物粒度环境敏感组分的分析,探讨了NH-1孔的沉积环境变化特征,并结合AVS、黄铁矿硫同位素、无机碳及有机质等数据,探讨了可能下部来源有机碳(甲烷)存在对硫循环的影响,及其对水合物存在的指示。对南黄海和南海柱状沉积物粒度进行了测试与分析,探讨了不同前处理方法对沉积物粒度特征的影响。结果表明,不同前处理方法获得样品的粒度特征差异不大,样品在去除碳酸岩和有机质后所测的粒度结果能较好的反应陆源碎屑的粒度特征。南海NH-1对沉积环境敏感的粒度组分范围分别为1.3～2μm、10~15μm和28～50μm。其中细粒组分(1.3～2μm与10~15μm)组分可能代表了悬浮物沉降来的沉积物,而28～50μm可能是底床运动的产物。根据环境敏感组分含量在深度上的变化剖面可识别出9个明显的沉积物波动旋回。更多还原

【Abstract】 Sulfur is one of the major components in seawater. Sulfur cycle in marine sedimentsduring diagenesis resulted in the geological evolution of the redox condition on thesurface of the Earth and that of the atmospheric composition. It has direct influence andcontrol on the marine carbon cycle and the biogeochemical behaviors or cycles of largenumber of trace elements, particularly heavy metals that may play an important role in themarine ecosystem. In addition, as marine sulfur cycle is found to be intertangled with themarine carbon cycle, study on the marine sulfur cycle will certainly shed light on thegas-hydrate, a potential new energy resource for the 21th century, that are usually burieddeep in the continental shelf or slope sediments. Consequently, the sulfur cycle has longbeen an important subject of study, and recently, it started to attract the attention of theChinese marine scientists.In this dissertation, the sediment samples taken from the Yellow Sea continental shelf,the Licun estuary of the Jiaozhou Bay, and the South China Sea continental slope, wereanalysed for grain size, contents of acid volatile sulfide (AVS), contents of pyrite, reactiveFe, organic carbon, pore water sulfate concentration, pyrite and its sulfur isotope. Basedon our data and the data in the East China Sea from previous work by others, theformation of sulfide and its controlling factors in the process of sulfur cycle in theChinese marinal seas were discussed. Based on the analysis of the reactive metals and thepyritized metals in the sediments of the Licun estuary, the transformation of AVS to pyriteand trace metals distribution in AVS and pyrite were discussed. The redox condition,which is crucial for the distribution of sulfides in the sediments, was discussed throughanalysis of the reactive metal profiles in the sediments of the Yellow Sea. Based on theenvironmentally sensitive group of grain size data, the characters of sedimentaryenvironments were discussed. Combining AVS, sulfur isotope of pyrite, organic carbon,inorganic carbon and N/C ratio, the abnormality of the sulfur cycle caused by upwardmethane flux and the indication of gas hydrate formation at depth were discussed.We determined the gain sizes of sediments collected from the Yellow Sea and theSouth China Sea, applying three different pretreatment schemes. Our data indicated thatsediment grain size, measured after organic matter and carbonate removal, reflected wellthe characteristics of terrigenic fraction of the sediment. At site NH-1 of the South ChinaSea, three size fractions (i.e.,1.3～2μm、10~15μm, and 28～50μm) of sediment wereidentified to reflect sedimentary environments. The fine-grained fractions (1.3～2μm and10~15μm) consisted mainly of particles that settle from the upper water column, whilefraction 28～50μm were composed of materials that were transported by bottom watercurrents.AVS content in the sediments of the Yellow Sea and the South China Sea wasdetermined. We found that AVS content decreased in the following order: Licun estuary inthe Jiaozhou Bay > Jiaozhou Bay > the East China Sea continental slope > the Yellow Seacontinental shelf > the East China Sea continental shelf > the South China Sea slope.Based upon our results of sulfide, reactive metals, and pyritization of sediment corescollected from the Yellow Sea and South China Sea, and published results of sedimentsfrom the East China Sea, we concluded that sediment organic carbon content was themajor factor that controlled the formation of sulfide in sediments of the Chinese MarginalSeas. Reactive iron would become the controlling factor only in environments with veryhigh organic carbon supply, such as the Licun estuary. The quantity and quality of organicmatter, sedimentation rate, redox condition, bottom water temperature, and burial time allcould influence the formation, quantity and transform of sulfides in the sediments.In sediment core NH-1, retrieved from the South China Sea, a pyrite contentmaximum was found at the depth of 141.5cm. Extensive sulfate reduction took place atdepths between 120-141.5cm. Combining previous results obtained from cores collectedto the west of our core, we thought that the depth of 141.5cm might represent theboundary of Late Pleistocene glacial and Holocene post-glacial period. The high AVScontents appeared near the bottom of the sediment core, which was abnormal as AVS inmost marine sediments had mid-depth maximum. Both δ34S of pyrite and AVS contentshowed abnormal value at the 247.5～380.5cm interval of the sediment core NH-1,suggesting intensive methane upward flux and possibly the formation of gas-hydrate atgreater depth at this location.Both active Fe and Mn profiles showed maximums at the surface layer to subsurfacelayer. The depth of Fe maximum was usually deeper than that of Mn, which was inaccordance with the fact that Fe reduction began at deeper depth than Mn’s reduction.Reactive Mn, therefore, had a higher mobility in the sediment than reactive Fe. ReactiveMn enrichment in oxidizing environment and its absent in reducing environment couldserve as a sensitive indicator of bottom water redox conditions.更多还原