Reaction networks in environmental systems: connecting reactive oxygen species generation and particle formation during the oxidation of ferrous iron

国家科学基金会化学部的环境化学科学项目支持南卡罗来纳大学哥伦比亚分校约翰·L·费里教授的研究。已经有一些重要的工作描述了稀有(纳米分子)Fe(II)被氧气氧化的过程，也有许多描述了铁/铁固体在缺氧溶液中的电子转移。然而，这些还没有被整合到一个预测性的、以铁为基础的连续模型中，用于估计ROS的产量。在自然环境中，Fe(III)可以通过光化学过程、与还原剂(如硫化物)的直接反应或微生物介导的还原作用还原到Fe(II)状态。两个氧化态之间的净循环导致了ROS(包括过氧化氢自由基及其共轭碱超氧化物、羟基自由基和过氧化氢)的表观催化生成，并提供了元素Fe、O、C、S和N环之间的动力学和能量上的容易连接。研究人员开发了一种高通量的组合方法来探索溶液变化对Fe(II)氧化和Fe(III)存在下ROS产量的影响。提出的工作将检验特定的假设，即当生成的Fe(III)被隔离在可以与溶液相中的反应物进行原子转移和电子转移的相中时，ROS的产生是最大的。通过添加一系列有机探针，将在水相中测量ROS。溶解金属的浓度将通过分光光度技术和质谱学技术相结合来确定。固体将使用电子背散射和质谱学技术来表征56Fe和58Fe与O的比率。同位素标记的Fe(II)与颗粒Fe的交换将使用高分辨质谱学技术来确定。这些观测数据将与条件启动矩阵相关联，以形成描述系统ROS生成对氧添加的响应的响应面。这项研究的结果将导致对共溶质和胶体影响Fe(II)/Fe(III)循环速度的新理解。在副产品ROS(因此气候变化)驱动的碳周转以及公众健康问题的背景下，这些结果对普通公众具有重要意义。这项工作的成果将被纳入旨在教育该领域以外的学生和教职员工的研讨会中。这些讲习班将与德国德尔门霍斯特的汉斯高级研究所合作举办，并扩展到南卡罗来纳州博物馆。拟议的工作将为两名研究生和两名本科生提供支持。约翰·费里(John Ferry)和蒂姆·肖(Tim Shaw)教授在指导代表性不足的少数族裔和女性学生方面有着良好的记录；他们实验室的60名研究人员中有34名是女性，9名来自代表性不足的群体。

The Environmental Chemical Sciences Program in the Chemistry Division at the National Science Foundation supports the research of Professor John L. Ferry at the University South Carolina at Columbia. There have been several important works describing the oxidation of dilute (nanomolar) Fe(II) by oxygen and many describing electron transfer from ferrous/ferric solids in anoxic solutions. However, these have not been integrated into a predictive, Fe-based continuous model for estimating ROS production. In the natural environment, Fe(III) can be reduced to the Fe(II) state through photochemical processes, direct reaction with reductants (e.g. sulfides) or via microbially mediated reduction. The net cycling between the two oxidation states leads to the apparent catalytic production of ROS (which include hydroperoxyl radical and its conjugate base superoxide, hydroxyl radical and hydrogen peroxide) and provides kinetically and energetically facile connections between the elemental Fe, O, C, S and N cycles. The researchers have developed a high throughput, combinatorial approach to explore the effect of solution variation on Fe(II) oxidation and ROS yield in the presence of Fe(III). Work proposed will test the specific hypothesis that ROS production is maximized when resulting Fe(III) is sequestered in phases that can undergo atom transfer as well as electron transfer with reactants in the solution phase. ROS will be measured in the aqueous phase through the addition of a series of organic probes. The concentration of dissolved metals will be determined by a combination of spectrophotometric and mass spectrometric techniques. Solids will be characterized for 56Fe to 58Fe to O ratios using electron backscatter and mass spectrometric techniques. The exchange of isotopically labeled Fe(II) with particulate Fe will be determined using high resolution mass spectrometric techniques. These observables will be correlated to the conditional initiating matrix to develop response surfaces describing the systemic ROS generation response to oxygen addition.The outcomes of this study will result in a new understanding of how rapid Fe(II)/Fe(III) cycling is affected by co-solutes and colloids. These outcomes have significance to the general public in the context of carbon turnover driven by the by-product ROS (and hence climate change) as well as public health concerns. Results from this work will be incorporated into workshops designed to educate students and faculty outside of the field. The workshops will be developed in collaboration with the Hanse Institute for Advanced Study in Delmenhorst; Germany, and extended to the South Carolina State Museum. The proposed work will provide support for two graduate and two undergraduate students. Professors John Ferry and Tim Shaw have a well-documented record of mentoring underrepresented minorities and female students; 34 out of the 60 researchers in their laboratories have been female, and nine have been from underrepresented groups.