Quantitative Elucidation of the Role of Natural Organic Matter Fractions and Models on the Redox Reactivity of Iron Oxide Minerals

化学系的环境化学科学计划资助了明尼苏达大学的李·潘教授和比尔·阿诺德教授进行这一项目。他们研究了在存在和不存在天然有机物(NOM)的情况下，在氧化铁矿物颗粒上发生的污染物降解反应。在大多数天然水域中都能找到NOM。它是由植物物质分解形成的，由藻类和其他微生物产生。NOM是一种复杂的分子混合物，一些分子抑制，另一些分子促进发生在液体-矿物界面的反应。这意味着NOM会影响污染物分子在环境中的持久性。当暴露在矿物表面时，环境中的NOM分子的类型会发生变化。留在水中的NOM会随着暴露于环境系统中的矿物质而演变，这一过程被称为分馏。关于NOM的不同部分如何影响氧化铁矿物表面的反应性，人们知之甚少。回答这个问题将弥合实验室和实地研究之间的主要差距。研究人员之间的合作结果将加深对环境系统中NOM的性质和演变以及NOM对涉及常见有机污染物的反应的影响的基本了解。这项工作的更广泛影响包括改善对环境系统中矿物表面化学行为的了解所带来的潜在社会效益。主要的教育部分通过与明尼苏达州公立学校的一名科学教师合作，重点放在高中生身上。学生接受指导和实践经验，如何使用定量照相手机比色法和模拟水处理，使用填充了各种材料的稻草柱，包括矿物涂层沙子和从生物物质中产生的碳。一个主要的项目重点是作为暴露在矿物表面的函数的NOM的逐步分馏。NOM的分馏是通过化学和物理相结合的方法来完成的。反应器中使用的NOM量归一化为总有机碳。研究了矿物和不同数量、不同形态的NOM对污染物的降解速率。此外，在反应前、反应中和反应后，使用先进的材料表征方法对矿物颗粒进行表征，以确定反应在颗粒上发生的位置以及NOM组分如何影响反应位置。结果有助于阐明对反应性影响最强(和最弱)的NOM组分的性质，从而有助于污染物的持久性。该团队使用从国际腐植酸物质协会(IHSS)获得的NOM标准和从环境中收集的NOM样本。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The Environmental Chemical Sciences Program in the Chemistry Division funds Professors Lee Penn and Bill Arnold of the University of Minnesota for this project. They study pollutant degradation reactions that occur on iron oxide mineral particles in the presence and absence of natural organic matter (NOM). NOM can be found in most natural waters. It is formed from the decomposition of plant material and produced by algae and other microorganisms. NOM is a complex mixture of molecules, with some inhibiting and others facilitating reactions that occur at the liquid-mineral interface. This means that NOM impacts the persistence of pollutant molecules in the environment. The types of NOM molecules in the environment change when exposed to mineral surfaces. The NOM remaining in the water will evolve with exposure to the minerals in environmental systems, a process called fractionation. Little is known about how different fractions of NOM impact the reactivity of iron oxide mineral surfaces. Answering this question will bridge major gaps between laboratory and field studies. Results from the collaboration between the investigators will deepen fundamental understanding of the nature and evolution of NOM in environmental systems and the impact of NOM on reactions involving common organic contaminants. The broader impacts of this work include potential societal benefits caused by improved understanding of the chemical behavior of mineral surfaces in environmental systems. The major educational component focuses on high school students through a collaboration with a science teacher from a Minnesota Public School. Students receive instruction and hands on experience in using quantitative camera phone colorimetry with simulated water treatment using straw columns filled with various materials, including mineral coated sands and carbon produced from biomass.A major project focus is the progressive fractionation of NOM as a function of exposure to mineral surfaces. NOM fractionation is accomplished by a combination of chemical and physical methods. The amount of NOM used in a reactor is normalized to the total organic carbon. The rate of pollutant degradation is studied in the presence of minerals and different amounts and fractions of NOM. In addition, mineral particles are characterized using advanced materials characterization methods before, during, and after reactions to identify where on the particles the reaction occurs and how the NOM fractions affect the reaction location. Results enable elucidation of the nature of NOM fractions that most strongly (and weakly) impact reactivity and thus the persistence of pollutants. The team uses NOM standards obtained from the International Humic Substances Society (IHSS) and NOM samples collected from the environment.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.