Development and Intercomparison of Methodologies to Measure Dissolved Ferrous Iron in Seawater

测量海水中溶解二价铁的方法的开发和比较

基本信息

批准号：
1459584
负责人：
James Moffett
金额：
$ 29.08万
依托单位：
University of Southern California
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2015
资助国家：
美国
起止时间：
2015-03-01 至 2017-12-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1459584&HistoricalAwards=false
关键词：
Development Intercomparison Methodologies Measure Dissolved

项目摘要

The trace metal iron is a key micronutrient throughout the oceans that plays an important role in regulating primary production. Iron (chemical symbol Fe) can exist in different ionization states in the environment, primarily as the reduced form Fe(II) and the oxidized form Fe(III), which impacts its chemical behavior within the water column, and ultimately the ability of researchers to accurately measure its abundance. There is an urgent need in the chemical oceanography community for accurate measurements of Fe(II) in the water column, as currently used methods may overestimate concentrations in water samples collected from certain depths. In this study, researchers from the University of Southern California will significantly redevelop an underutilized methodology to measure Fe(II), and carry out an evaluation and inter-comparison between the two methodologies. This work will enable the refinement of estimates of Fe(II) concentration, present a robust methodology for future use, and clarify conditions where the current methodology can be used effectively. This project will involve strong undergraduate research opportunities, and the research will be conducted in collaboration with an international researcher from India.Fe(II) is thermodynamically unstable in seawater in the presence of oxygen or nitrate, yet its presence has been reported both in surface waters and in oxygen minimum zones. A rigorous assessment of Fe(II) measurements is important because its chemistry and bioavailability are so different than Fe(III). Fe(II) forms weak complexes, is weakly hydrolyzed and highly soluble in seawater. Fe(III) forms strong complexes, is sparingly soluble and strongly hydrolyzed. The presence of even a modest fraction of Fe as Fe(II) under Fe-limited conditions could increase bioavailability by orders of magnitude. The most widely used methodology to determine Fe(II) at nanomolar to sub-nanomolar levels involves the Fe(II) catalyzed oxidation of luminol, a chemiluminescent (CL) reaction. There are potential artifacts with this methodology, especially in the euphotic zone, where other reduced species might interfere. Researchers will develop a new, modified version of a published alternative method to CL involving the preconcentration of Fe(II) complexed by a synthetic chelator. While this alternative method is prone to artifacts and contamination that has limited its value in the open ocean, new approaches create a plausible path to an accurate and sensitive protocol that is independent of the luminol method. Following the new method development, this project will implement inter-comparisons with the CL approach, which will be conducted in the laboratory, in an anoxic mesocosm system, at a coastal time-series station off the California coast, and in the Eastern Tropical North Pacific.

痕量金属铁是整个海洋中的关键微量营养素，在调节初级生产中起着重要作用。铁（化学符号Fe）可以在环境中的不同电离状态中存在，主要是为了减少形式的Fe（II）和氧化形式Fe（III），这会影响其在水柱中的化学行为，最终影响了研究人员准确测量其丰度的能力。化学海洋学社区迫切需要在水柱中准确测量Fe（II），因为目前使用的方法可能高估了从某些深度收集的水样品中的浓度。在这项研究中，南加州大学的研究人员将大大重新开发一种未充分利用的方法，以测量Fe（II），并在两种方法之间进行评估和相互比较。这项工作将使Fe（II）浓度的估计值进行完善，并提供一种可靠的方法，以供将来使用，并阐明可以有效使用当前方法的条件。该项目将涉及强大的本科研究机会，该研究将与来自印度的国际研究人员合作进行。FE（II）在氧气或硝酸盐的存在下在海水中在热力学上不稳定，但据报道其在地表水和氧气最小区域中的存在。对FE（II）测量的严格评估很重要，因为其化学和生物利用度与FE（III）的不同。 Fe（II）形成弱复合物，被弱水解且在海水中高度可溶。 Fe（III）形成强大的复合物，很少溶于溶解和强烈水解。 Fe（II）在Fe限制条件下的Fe（II）的存在可能会增加数量级的生物利用度。在纳摩尔到亚纳摩尔水平上确定Fe（II）的最广泛使用的方法涉及Fe（II）催化Luminol（化学发光（CL）反应）的催化氧化。这种方法有潜在的伪像，尤其是在舒适区，其他减少的物种可能会干扰。研究人员将开发一种新的，修改的已发表替代方法，以涉及由合成螯合剂复合的Fe（II）的预浓缩。尽管这种替代方法容易限制其在开放海洋中价值的伪像和污染，但新方法为准确敏感的方案创造了合理的途径，该方案独立于Luminol方法。遵循新的方法开发后，该项目将与CL方法实施综合子，该方法将在实验室，在加利福尼亚海岸附近的沿海时间序列站和东部热带北太平洋的沿海时间序列站中在实验室中进行。