Organic sulfur (OS)is an important sulfur pool in marine sediments.Sulfurization of organic matter (OM)helps to enhance the preservation of OM and exerts an important impact on mobility of trace elements. Chemical extractions were used to quantify base-extractable humic-acid sulfur (HA-S),fulvic-acid sulfur (FA-S) and non-chromium-reducible OS (non-CROS)in Jiaozhou Bay sediments,and sulfur stable isotope was used to trace their sources and mechanisms of formation.Results show that non-CROS,HA-S and FA-S contents are 1 9.1 to 52.6,3.35 to 7.82,and 27.3 to 38.6μmol/g,respectively,being at the lower ends of the respective contents in many other marine sediments.The three OS pools are mixtures of diagenetic and marine biogenic OS,with the HA-S and non-CROS dominated by biogenic OS (65% to 68% and 67% to 77%,respectively),while the FA-S dominated by diagenetic one (54% to 73%).Relative to the biogenic OS,diagenetic OS is more readily extracted by both base and acidic Cr(Ⅱ)solutions.Thus both base-extractable OS (i.e.,HA-S+FA-S)and non-CROS can-not truly reflect the compositions and sources of OS in the bulk sediments.Simultaneous downcore increase in con-tents of pyrite-S and diagenetic OS in humic substances suggests that pyrite formation has not competitively inhibi-ted OM sulfurization to a significant extent.%有机硫是海洋沉积物中重要的硫形态,其中成岩有机硫对有机质保存和微量元素形态具有重要影响。利用化学提取及硫稳定同位素研究了胶州湾沉积物中碱可提取的腐殖酸硫(HA-S)、富里酸硫(FA-S)以及铬不可还原有机硫(non-CROS)的垂直分布、来源及形成机制。结果表明,non-CROS、HA-S以及FA-S的含量范围分别为19.1~52.6、3.35~7.82和27.3~38.6μmol/g,均处于其他许多近海沉积物中含量的低值区,且3者均为海洋生物有机硫和成岩有机硫的混合物。HA-S 和 non-CROS以海洋生物有机硫为主,其份数分别为65%~68%和67%~77%,而FA-S则以成岩有机硫为主(54%~73%)。相对于生物有机硫,成岩有机硫更易被碱和酸性Cr(Ⅱ)溶液提取,因此腐殖质硫和non-CROS都不能全面反映沉积物中有机硫的组成和来源。黄铁矿和腐殖质中成岩有机硫含量随深度的同步增加表明黄铁矿形成并未明显地竞争性抑制有机质硫化。
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