Organic sulfur (OS) is an important sulfur pool in marine sediments and has important influence on the preservation of organic matter and geochemical cycle of various elements. Sulfur K-edge XANES spectroscopy has been used to investigate, on the molecular level, the speciation and relative fractions of humic acid sulfur (HA-S), fulvic acid sulfur (FA-S) and non chromium reducible organic sulfur (non-CROS) in sediments of the East China Sea inner continental shelf. Results show that oxidized OS is generally the predominant species in both the HA-S and FA-S, on average accounting for 56%and 69%of HA-S and FA-S, respectively. However, reduced OS is the predominant components of the non-CROS. For both the HA-S and FA-S, strongly reduced OS accounts for the majority of the reduced OS. Sulfonates and ester-sulfates are the major components of the oxidized OS in the HA-S, and ester-sulfates are the major components of the oxidized ones in the FA-S. The formation of the strongly reduced OS in the HA-S, FA-S, and non-CROS can be ascribable to sulfurization/biogenesis, sulfurization, and biogenesis, respectively. If non-CROS is really an approximate representation of total OS in marine sediments, it follows that total OS is characterized by high fraction of highly reduced components in the sediments. Thus high fraction of oxidized components in humic sulfur (HA-S + FA-S) indicates that base-extractable humic sulfur cannot comprehensively reflect the compositions and the sources of OS in the bulk sediments.%有机硫是海洋沉积物重要的硫形态，与有机质保存及多种元素的地球化学循环密切相关。利用硫的K 边 XANES 谱从分子水平研究了东海内陆架沉积物中腐殖酸硫(HA-S)、富里酸硫(FA-S)以及铬不可还原有机硫(non-CROS)的形态及相对含量。结果表明， HA-S和FA-S总体上均以氧化态有机硫为主，其相对平均含量分别为56%和69%，而non-CROS则以还原态有机硫为主(>86%)。HA-S和FA-S的强还原态硫为还原态有机硫的主要组成，磺酸盐和硫酸酯为H A-S中氧化态有机硫的主要组分，硫酸酯为FA-S中氧化态有机硫的主要组分。FA-S的强还原态有机硫为硫化成因， HA-S的强还原态硫可能与硫化和生物成因有关，而non-CROS的强还原态有机硫则主要为生物成因。如 non-CROS能近似代表海洋沉积物中的有机硫总量，则表明该沉积物中总有机硫以还原态硫为主；而腐殖质硫(HA-S+FA-S)较高比例的氧化态硫则表明腐殖质硫不能全面反映沉积物中有机硫的组成和来源。
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