Collaborative Research: Transformations of soluble Mn(III) along horizontal and vertical oxygen gradients

合作研究：可溶性 Mn(III) 沿水平和垂直氧梯度的转化

• 批准号: 1558692
• 负责人: Bradley Tebo
• 金额: $ 43.4万
• 依托单位: Oregon Health & Science University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-03-01 至 2020-02-29
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1558692&HistoricalAwards=false
• 关键词: Collaborative; Research; Transformations; soluble; Mn

Manganese (Mn) is an important trace nutrient for biological growth in marine organisms. In the past, all Mn dissolved in seawater was thought to exist in only one chemical form: Mn(II). Recent work in waters and sediments with little or no oxygen has shown that Mn(III) can be the dominant form of dissolved Mn and can even be present in oxygenated water if attached to specific organic molecules called ligands. This research will further investigate these discoveries, aiming to quantify the chemical and microbiological processes responsible for Mn(III) cycling under varying oxygen concentrations. The research will compare field sites in the Broadkill River wetland, the Chesapeake Bay, and the Lower St. Lawrence Estuary; measuring the water column and sediments known to have strong oxygen gradients and different organic carbon sources that could change the availability and binding strength of ligands that would stabilize dissolved Mn(III). In some chemical forms, Mn tends to act like iron, so this research may have broader implications by helping marine chemists to understand more about iron cycling in similar oxygen gradients. With growing concerns over diminished oxygen concentrations (hypoxia) in the ocean, and particularly in coastal regions, understanding the reactions of Mn(III) with organic ligands across oxygen gradients could become important for understanding Mn availability to organisms. The project includes support for the participation and mentoring of one graduate student and two postdoctoral researchers, and there will be a U.S.-Canada collaboration. A variety of public outreach activities are planned with a K-12 teacher to be selected as a participant on a research cruise.Mn(III) has only recently been recognized as an important redox state for Mn in seawater. Previously, it was widely accepted that all Mn that passes through a 0.2 or 0.4 µm filter is dissolved Mn(II) while the retained portion is solid Mn(III, IV) oxide. Research in the Black Sea, the Baltic Sea, and the Chesapeake Bay has shown that soluble Mn(III) can be up to 100% of the dissolved Mn in the water column. Also, Mn(III) can exist as complexes with organic ligands in oxygenated seawater. This project will quantify and constrain the mechanisms surrounding weak and strong Mn(III) ligand transformations across vertical and horizontal oxygen gradients. Field sites to be studied include systems with a variety of organic carbon sources and oxygen dynamics: the Lower St. Lawrence Estuary, Chesapeake Bay, and Broadkill River wetland estuary. This research will continue to inform the fundamental shift that is taking place in our current understanding of Mn biogeochemistry in coastal systems. The results should also be applicable to redox processes involving Fe(III) ligand transformations, since Mn and Fe tend to exhibit similar redox chemistry under similar environmental conditions.

锰（MN）是海洋生物生物生长的重要痕量养分。过去，所有溶解在海水中的MN仅以一种化学形式存在：Mn（ii）。在几乎没有氧气或没有氧气的水和沉积物中的最新工作表明，如果与特定的有机分子（称为配体）相连，则Mn（III）可能是溶解的Mn的主要形式，甚至可以存在于氧化水中。这项研究将进一步研究这些发现，旨在量化在不同的氧气浓度下导致MN（III）循环的化学和微生物过程。该研究将比较Broadkill河湿地，切萨皮克湾和下圣劳伦斯河口的野外场所；测量已知具有强氧梯度和不同有机碳源的水柱和沉积物，这些含量可以改变稳定溶解的Mn（III）的配体的可用性和结合强度。在某些化学形式中，MN倾向于像铁一样起作用，因此这项研究可能会通过帮助海洋化学家了解有关类似氧梯度中铁循环的更多意义。由于人们对海洋氧气浓度（缺氧）的越来越关注，尤其是在沿海地区，因此了解MN（III）与氧气梯度跨氧气梯度的反应对于了解对组织的MN可用性很重要。该项目包括对一名研究生和两名博士后研究人员的参与和心理化的支持，并将进行美国加拿大的合作。计划与K-12老师一起选择各种公共外展活动。以前，通过0.2或0.4 µm滤光片的所有MN均溶解Mn（II），而保留部分为实心Mn（III，IV）氧化物。在黑海，波罗的海和切萨皮克湾进行的研究表明，固体Mn（III）最多可达水柱中溶解的MN的100％。同样，Mn（III）可以作为具有氧化海水中有机配体的复合物存在。该项目将量化并限制跨垂直和水平氧梯度跨弱和强Mn（III）配体转化的机制。要研究的现场现场包括具有各种有机碳源和氧气动态的系统：下圣劳伦斯河口，切萨皮克湾和Broadkill河湿地河口。这项研究将继续为我们当前对沿海系统中MN生物地球化学的理解所发生的基本转变提供信息。结果也应适用于涉及Fe（III）配体转化的氧化还原过程，因为MN和FE在相似的环境条件下倾向于存在相似的氧化还原化学。