南极罗斯海氧化还原敏感元素沉积地球化学特征及其古海洋意义  

Sedimentary gochemical characteristics of the Redox-sensitive elements in Ross Sea,Antarctica:Implications for paleoceanography

作　　者：王家凯 李铁刚 熊志方[3,4] 常凤鸣 秦秉斌[3] 王琳淼 贾奇 WANG Jiakai;LI Tiegang;XIONG Zhifang;CHANG Fengming;QIN Bingbin;WANG Linmiao;JIA Qi(CAS Key Laboratory of Marine Geology and Environment,Institute of Oceanology,Chinese Academy of Sciences,Qingdao 266071,China;University of Chinese Academy of Sciences,Beijing 100049,China;Key Laboratory of Marine Sedimentology and Environmental Geology,First Institute of Oceanography,SOA,Qingdao 266061,China;Laboratory for Marine Geology,Qingdao National Laboratory for Marine Science and Technology,Qingdao 266061,China)

机构地区：[1]中国科学院海洋研究所海洋地质与环境重点实验室,青岛266071 [2]中国科学院大学,北京100049 [3]国家海洋局第一海洋研究所海洋沉积与环境地质国家海洋局重点实验室,青岛266061 [4]青岛海洋科学与技术国家实验室海洋地质过程与环境功能实验室,青岛266061

出　　处：《海洋地质与第四纪地质》2018年第5期112-121,共10页Marine Geology & Quaternary Geology

基　　金：国家自然科学基金项目"80万年来热带西太平洋上层水体pH和pCO_2演变及影响机理"(41230959);"MIS 6期以来罗斯海深层水流通性的变化及其对大气CO_2冰期旋回的影响"(41606216);青岛海洋科学与技术国家实验室鳌山科技创新计划项目(2016ASKJ13)

摘　　要：大洋深部氧化还原环境与深部水体流通状况以及表层水体生产力密切相关。表层生产力与深部流通性变化影响着有机碳-呼吸CO_2的转化及其在海洋-大气中的转移,最终与大气CO_2分压(pCO_2)变化密切相关。故探明大洋深部氧化还原环境的变化对于解决大气pCO_2冰期旋回机制具有重要意义。本次研究以中国第31和32次南极科考获得的南极罗斯海柱状岩心ANT31-R23及表层样为研究材料。通过元素钙、钛,以及氧化还原敏感元素(RSE)锰、钼、镍、钴、镉的测试分析,以表层样中RSE与Ti的比值作为判断ANT31-R23孔中相应RSE富集程度的背景值。结果显示,Mn在沉积期均表现出富集,表明罗斯海深部在该孔沉积期为氧化环境。根据Mn在不同层位出现的富集峰识别出4次强氧化脉冲事件,可能由南大洋底层水流通性增强和/或生产力降低导致。4次氧化脉冲事件层位中Mo、Ni、Co的明显富集,是由于锰(氢)氧化物对其捕获或吸附所致。此外,推测分析认为罗斯海对冰期大气pCO_2降低似乎没有明显贡献,但很可能对冰消期大气pCO_2迅速升高起重要作用。然而这些有关南极罗斯海深部氧化还原环境与大气pCO_2变化之间关联的推测,有待后续该孔精确年代模式的构建,方可进一步验证。Redox conditions of deep ocean are supposed closely related to deep ocean circulation and surface water production.Facts prove that surface water production and deep water circulation may strongly influence the formation of respiration carbon and its migration from ocean interior to atmosphere,which is closely related to the rise of atmospheric pCO2.Hence,verifying the redox environment evolution of the ocean could help us clarify the mechanism of variation in atmospheric pCO2 in glacial-interglacial cycles.Samples from core ANT31-R23 and the surface sediment of central Ross Sea,which were taken by R/V Xuelongin the 31^st and 32^th Chinese National Antarctic Research Expedition,are used as research materials in this study.Both the major and minor elements are analyzed,including calcium,titanium and the elements sensitive to paleoredox environment of deposition,so-called Redox-sensitive elements（RSE）,such as manganese,molybdenum,nickel,cobalt and cadmium.RSEs normalized by Ti are adopted as background values to estimate if the RSEs are enriched or depleted.The result shows that enrichment of Mn occurs in the entire core indicating an oxidizing condition.Four strong oxidation pulse events are identified based on Mn peaks in different depths,which may be related to stronger circulation conditions and/or lower surface water production in the Southern Ocean during late Quaternary.The layers enriched by Mo,Co and Ni in addition to Mn,are resulted from absorption,capture or scavenge by Mn-oxyhydroxides.These results suggest that the Ross Sea does not have significant contribution to the reducing of atmospheric pCO2 during glaciation.The strong oxidation pulse events,however,may play an important role in elevating atmospheric pCO2 during deglaciation.Nevertheless,the detailed processes of this mechanism will be effectively revealed by follow-up work after the establishment of accurate chronology framework.

关 键 词：罗斯海 氧化还原敏感元素 氧化脉冲 深部流通性 碳循环 

分 类 号：P734.2[天文地球—海洋化学]