Advances in Earth Science ›› 2022, Vol. 37 ›› Issue (4): 358-369. doi: 10.11867/j.issn.1001-8166.2022.013

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Indication to Redox Conditions of Re, Mo and U in Marine Environment

Xiaotong ZHANG 1 , 2 , 3( ), Huamao YUAN 1 , 2 , 3 , 4( ), Jinming SONG 1 , 2 , 3 , 4, Liqin DUAN 1 , 2 , 3 , 4   

  1. 1.CAS Key Laboratory of Marine Ecology and Environmental Sciences,Institute of Oceanology,Chinese Academy of Sciences,Qingdao 266071,China
    2.University of Chinese Academy of Sciences,Beijing 100049,China
    3.Marine Ecology and Environmental Science Laboratory,Pilot National Laboratory for Marine Science and Technology,Qingdao 266237,China
    4.Center for Ocean Mega-Science,Chinese Academy of Sciences,Qingdao 266071,China
  • Received:2021-06-27 Revised:2022-01-28 Online:2022-04-10 Published:2022-04-28
  • Contact: Huamao YUAN;
  • About author:ZHANG Xiaotong (1997-), female, Xingtai City, Hebei Province, Master student. Research areas include marine biogeochemistry. E-mail:
  • Supported by:
    the Strategic Priority Research Program of the Chinese Academy of Sciences "Technique and scheme of Chinese offshore environmental health assessment"(XDA23050501);The National Natural Science Foundation of China "Microbial regulation of arsenic cycling in eutrophic coastal sediments: a case study of the Yangtze River Estuary"(41976037)

Xiaotong ZHANG, Huamao YUAN, Jinming SONG, Liqin DUAN. Indication to Redox Conditions of Re, Mo and U in Marine Environment[J]. Advances in Earth Science, 2022, 37(4): 358-369.

Redox Sensitive Trace Elements (RSE), such as Re, Mo, and U, are often autogenetically enriched in sediments because of their different solubilities and/or affinities for particulates under various redox states at the time of sediment deposition when diffusing through the sediment-water interface. The enrichment of Re is primarily in a suboxic depositional environment but that of Mo is in an euxinic environment. In contrast, U has a relatively large depositional depth range in sediments. The special geochemical behavior of the RSEs makes it possible to indicate the redox state, as the autogenetic enrichment degrees in sediments have a good correlation with the redox conditions of marine sedimentary environments. Lower enrichments were recorded from sediments deposited in oxic (Re/Al<1.3×10-7, Mo/Al<0.4×10-4) and beneath seasonal oxygen minimum zone environments, while higher enrichments were recorded from sediments deposited within the perennial oxygen minimum zone (U/Al>5×10-4, Mo/Al>5×10-4) and euxinic (Mo/Al>5×10-4) environments. In addition to the relative enrichment degree, the paleoredox proxies of the enrichment coefficient (TMEF<1 means depletion; TMEF>1 means enrichment; TMEF>3 means obvious enrichment; TMEF>10 means significant enrichment), trace elements ratios (Re/Mo≤0.3×10-3 indicates an oxic environment; Re/Mo≈10×10-3~30×10-3 indicates an anoxic environment; Re/Mo≈0.7×10-3~0.8×10-3 indicates an euxinic environment), the trace elements covariant system (MoEF/UEF≈0.1×modern seawater value~0.3×modern seawater value indicates an oxic-suboxic environment; MoEF/UEF>1×modern seawater value indicates an anoxic environment; MoEF/UEF≈3×modern seawater value~10×modern seawater value indicates an euxinic environment), and isotope values (δ98/95Mo≈-0.7‰ in an oxic environment; δ98/95Mo≈-0.5‰~+1.3‰ in a suboxic environment; δ98/95Mo≈+1.6‰ in an anoxic environment; δ98/95Mo≈+2.2‰~+2.5‰ in an euxinic environment) could also be utilized to comprehensively unravel the history of depositional environments. It should be noted that the migration and transformation mechanisms under the different redox conditions of Re, Mo, and U are imperfect, and related datasets in modern marine systems are limited. The highly variable enrichment degrees of Re, Mo, and U reflect obvious regional differentiation, which is yet to be examined. In future, more observations and research in modern marine systems are needed to improve the indicative utility of RSEs combined with the paleo-marine system.

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