Collaborative Research: Antimony stable isotope systematics during bacterial and abiotic redox cycling

合作研究：细菌和非生物氧化还原循环过程中锑稳定同位素系统学

• 批准号: 1650662
• 负责人: Thomas Kulp
• 金额: $ 18.09万
• 依托单位: SUNY at Binghamton
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-03-01 至 2021-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1650662&HistoricalAwards=false
• 关键词: Collaborative; Research; Antimony; stable; isotope

Antimony (Sb) is a toxic metalloid of emerging global environmental concern that shares many chemical and toxicological similarities to arsenic (As). Oxidative or reductive ("redox") reactions that are mediated by microorganisms control the mobility and toxicity of Sb and As in the environment. Whereas As has only one stable isotope (75As), Sb has two, 121Sb and 123Sb. Kinetic isotope effects often favor faster reaction rates for lighter isotopes compared to heavier isotopes during reduction reactions (with generally weaker effects related to oxidation). This causes a fractionation effect whereby the isotopic ratio in the reaction product may become enriched in the lighter isotope compared to the reactant pool. Although isotopic fractionation effects have previously been used to indicate the occurrence and extent of redox reactions involving other toxic elements in nature, the extent to which bacterial cycling fractionates Sb isotopes is unknown. This study will establish the extent of Sb stable isotope fractionation during bacterial redox cycling. Given the geochemical and geomicrobiological similarities between Sb and As, it may also be possible to infer that redox processes detected from Sb isotopic measurements are also actively affecting As when both elements co-occur. The broader impacts of this project include an improved understanding of the geomicrobiological processes that control the behavior of Sb and As in contaminated settings. Investigators will also train two MS graduate students and 4 to 6 undergraduate students per year through programs that target underrepresented students. The scope of this project is to investigate antimony (Sb) stable isotopic fractionation during geomicrobiological cycling between the environmentally relevant Sb(V) and Sb(III) valence states. Investigators will compare the magnitude and direction of Sb isotopic fractionation during bacterial reduction and oxidation to that which occurs during chemical (abiotic) redox reactions. They will conduct experiments with cultures of known Sb(V)-reducing or Sb(III)-oxidizing bacterial strains, as well as novel strains and microcosms obtained from a range of soil, freshwater, hypersaline, and hydrothermal environments. The liquid phase and solid precipitates in Sb-amended cultures will be periodically sampled during the course of bacterial redox reactions and the isotopic fractionation factors between reactants and reaction products will be measured. The results will potentially provide a new isotopic tool by which to predict the environmental behavior of Sb or to inform new strategies for bioremediation of Sb and As. It may also be possible to use the Sb stable isotopic composition of ancient geologic materials to identify the presence of biogeochemical Sb cycling (and, by proxy, As cycling) in the geologic past. This may provide a test for the hypothesized antiquity of As-based metabolisms, or alternately a proxy by which to assess paleo-redox conditions on ancient Earth.

锑（SB）是一种有毒的金属，具有新兴的全球环境问题，与砷具有许多化学和毒理学相似性（AS）。 由微生物介导的氧化或还原性（“氧化还原”）反应控制SB的迁移率和毒性以及环境中。 尽管只有一个稳定的同位素（75AS），但SB具有两个，121SB和123SB。 在还原反应期间，与较重的同位素相比，动力学同位素的作用通常有利于更快的反应速率（通常与氧化有关的较弱的效果）。 这会导致分馏效应，从而与反应池相比，反应产物中的同位素比可能富集在较轻的同位素中。 尽管同位素分离效应以前已被用来表明涉及自然界其他有毒元件的氧化还原反应的发生和程度，但细菌循环分级的SB同位素尚不清楚的程度。这项研究将确定细菌氧化还原循环过程中SB稳定同位素分馏的程度。 鉴于SB和AS之间的地球生物学相似性和地球生物学相似性，也可能可以推断出从SB同位素测量中检测到的氧化还原过程也正在积极影响，就像两个元素共发生时一样。 该项目的更广泛的影响包括对控制SB行为以及在受污染环境中的行为的地球生物学过程的深入了解。 调查人员还将通过针对代表性不足的学生的计划来培训两名MS研究生和4至6名本科生。 该项目的范围是研究在与环境相关的SB（V）和SB（III）价状态态之间的地球生物学循环期间，锑（SB）稳定的同位素分馏。 研究人员将比较细菌还原和氧化过程中SB同位素分馏的大小和方向与化学（非生物）氧化还原反应期间发生的氧化。 他们将使用已知的SB（V） - 还原或SB（III）氧化细菌菌株的培养物以及从一系列土壤，淡水，催眠盐和水热环境中获得的新型菌株和微观的培养。 在细菌氧化还原反应过程中，将定期采样SB培养物中的液相和固体沉淀物，将测量反应物和反应产物之间的同位素分馏因子。 结果可能会提供一种新的同位素工具，通过该工具可以预测SB的环境行为或为SB和AS生物修复的新策略提供信息。 也可以使用古代地质材料的SB稳定同位素组成来识别地质过去的生物地球化学SB循环（以及代理，作为循环）的存在。 这可以为基于AS的代谢的假设古代提供测试，或者是评估古代地球上古雷斯条件的代理。