海洋沉积物甲烷厌氧氧化作用(AOM)及其对无机硫循环的影响

Anaerobic Oxidation of Methane(AOM) and Its Influence on Inorganic Sulfur Cycle in Marine Sediments

甲烷厌氧氧化作用(AOM)在调控全球甲烷收支平衡以及缓解因甲烷引起的温室效应等方面扮演着十分重要的角色,成为近些年来海洋生物地球化学领域的研究热点之一。一般而言,海洋沉积物孔隙水硫酸盐还原主要是通过2种反应途径来完成,即氧化有机质途径和AOM途径。长期以来,与有机质氧化途径相关的硫酸盐还原作用研究已有充分展示,而由AOM驱动的硫酸盐还原及其对自生硫化铁形成与埋藏的重要贡献却被严重低估。侧重从生物地球化学、同位素地球化学等角度,综述近些年来不同环境条件下海洋沉积物AOM作用发生的地球化学证据和AOM对沉积物孔隙水硫酸盐消耗比例的贡献大小及其调控因素。AOM过程产生的H2S会与沉积物中活性铁结合形成自生铁硫化物。与沉积物浅表层条件相比,AOM过程固定的自生铁硫化物不容易发生再氧化,更利于在沉积物中埋藏保存起来。AOM与海洋沉积物硫酸盐还原作用相偶联,由AOM驱动的硫酸盐还原过程对海底自生铁硫化物形成与埋藏的重要贡献不容忽视。该综述有助加深对海洋沉积物AOM作用的认识及其对硫循环的全面理解。

The process of AOM plays a significant role in regulating the global balance of methane budget and reducing the greenhouse effect driven by methane emission into atmosphere.Therefore,AOM occurring in marine sediments has become a hot research topic of biogeochemistry in recent years.Generally,sulfate reduction occurs mainly through two pathways,e.g.,oxidation organic matter and AOM.Currently,a lot of literatures documented the sulfate reduction driven by the organic matter,however,sulfur cycle driven by AOM was seriously underestimated.Here,based on the views of biogeochemistry and isotope geochemistry,we review the biogeochemistry evidence of AOM process occurring and the controlling factors of sulfate reduction through the AOM pathway.The process of AOM can produce H2S and it further react with reactive iron,forming the iron sulfur minerals.Comparing to the surface sediments,the iron sulfur minerals formation due to AOM are not easy oxidation and therefore buried favorably in the marine sediments.Thus,the roles of sulfate reduction and authigenic iron sulfide minerals formation driven by AOM should not be neglected.We hope this review paper will be helpful to better understand the AOM process and sulfur cycle in marine sediments.