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) 是一种新兴的全球环境问题的有毒非金属，与砷 (As) 有许多化学和毒理学相似之处。 由微生物介导的氧化或还原（“氧化还原”）反应控制着环境中锑和砷的迁移性和毒性。 As 只有一种稳定同位素 (75As)，而 Sb 有两种，即 121Sb 和 123Sb。 在还原反应期间，与较重同位素相比，动力学同位素效应通常有利于较轻同位素更快的反应速率（与氧化相关的效应通常较弱）。 这导致了分馏效应，由此反应产物中的同位素比率可能变得比反应物池中的更轻同位素更丰富。 尽管同位素分馏效应以前已被用来指示涉及自然界中其他有毒元素的氧化还原反应的发生和程度，但细菌循环分馏锑同位素的程度尚不清楚。这项研究将确定细菌氧化还原循环过程中锑稳定同位素分馏的程度。 鉴于 Sb 和 As 之间的地球化学和地球微生物学相似性，还可以推断，当两种元素同时出现时，从 Sb 同位素测量中检测到的氧化还原过程也会积极影响 As。 该项目更广泛的影响包括更好地了解控制污染环境中锑和砷行为的地球微生物过程。 研究人员还将通过针对代表性不足的学生的项目，每年培训两名硕士研究生和 4 至 6 名本科生。 该项目的范围是研究环境相关的 Sb(V) 和 Sb(III) 价态之间的地球微生物循环过程中锑 (Sb) 稳定同位素分馏。 研究人员将比较细菌还原和氧化过程中锑同位素分馏的程度和方向与化学（非生物）氧化还原反应过程中发生的情况。 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、高盐度和热液环境中获得的新菌株和微观世界进行实验。 在细菌氧化还原反应过程中，将定期对锑修正培养物中的液相和固体沉淀物进行取样，并测量反应物和反应产物之间的同位素分馏因子。 这些结果将有可能提供一种新的同位素工具，用于预测锑的环境行为或为锑和砷的生物修复新策略提供信息。 还可以利用古代地质材料的锑稳定同位素组成来识别过去地质中生物地球化学锑循环（以及砷循环）的存在。 这可能为假设的砷基代谢古代提供测试，或者作为评估古代地球古氧化还原条件的代理。