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首页> 外文期刊>Environmental Science & Technology >Trace Element Profiles in Sediments as Proxies of Dead Zone History; Rhenium Compared to Molybdenum
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Trace Element Profiles in Sediments as Proxies of Dead Zone History; Rhenium Compared to Molybdenum

机译：沉积物中的痕量元素剖面作为死区历史的代理； hen与钼相比

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摘要

Warm-season dead zones-volumes of coastal water containing too little O_2 to support macrofauna-are a growing global menace. Trace elements that are deposited in sediments in response to reducing or sulfidic conditions can provide proxy records for reconstructing dead zone evolution. Based on relative enrichment in reduced vs oxidized marine sediments, Re seems promising as a dead zone proxy. Here, Re is determined by isotope dilution mass spectrometry in sediments underlying the summertime dead zone in Chesapeake Bay. Contrary to expectation, Re becomes only modestly (～2-fold) elevated during the 20th century and fails to track the historic record of summertime O_2 depletion. Rhenium enrichments are watershed-specific and apparently controlled by anthropogenic sources, not by redox-linked authigenic processes. In contrast, Mo enrichments do track historic O_2 depletion. Three factors cause redox control to override anthropogenic control in the case of Mo: relative to weathering fluxes, anthropogenic Mo fluxes are weaker than Re fluxes; during anoxic periods, Mn refluxing amplifies Mo but not Re concentrations near the sediment surface; and high pore water sulfide-polysulfide promotes Mo fixation in pyrite while promoting formation of organo-Re adducts; the latter are too mobile and reactive to preserve a reliable historic record under seasonally fluctuating redox conditions.
机译：暖季死区-沿海水域的O_2含量太少，无法支撑大型动物-是全球威胁日益严重的地区。响应还原或硫化条件而沉积在沉积物中的痕量元素可以为重建死区演化提供代理记录。基于还原和氧化海洋沉积物中的相对富集，Re似乎有望成为死区代理。在这里，Re是通过同位素稀释质谱法在切萨皮克湾夏季死区下面的沉积物中确定的。与预期相反，Re在20世纪仅略微升高（约2倍），而无法追踪夏季O_2消耗的历史记录。的富集是特定于流域的，显然是由人为来源控制的，而不是由氧化还原相关的自生过程控制的。相反，Mo富集确实跟踪了历史O_2的消耗。在Mo情况下，有三个因素导致氧化还原控制优于人为控制：相对于风化通量，人为Mo通量比Re通量弱；在缺氧时期，锰的回流会增加沉积物表面附近的Mo而不是Re的浓度；高孔隙度水硫化物-多硫化物促进黄铁矿中的Mo固着，同时促进有机-Re加合物的形成。后者的活动性和反应性太强，无法在季节性波动的氧化还原条件下保存可靠的历史记录。

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  • 来源
    《Environmental Science & Technology》 |2013年第3期|1257-1264|共8页
  • 作者

    George R. Helz; Jordan M. Adelson;

  • 作者单位

    Department of Chemistry and Biochemistry, University of Maryland, College Park Maryland 20742, United States;

    Department of Chemistry and Biochemistry, University of Maryland, College Park Maryland 20742, United States,NAVSEA Quality and Credentialing Office, 1661 Red Bank Road, Goose Creek SC, 29445;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);美国《化学文摘》(CA);
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  • 正文语种 eng
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