CAS: Oxidation from the Top Down and the Bottom Up by the OH Radical: Lifetimes and Fates of Important Ingredients of Pesticides, Pharmaceuticals, and Consumer Products

在化学系环境化学科学项目的支持下，加州大学欧文分校的Barbara Finlayson-Pitts教授和她的团队将研究环境中新出现的污染物的降解。这些包括广泛的人造产品，包括杀虫剂、药品和消费品。它们对人类和环境的有害影响往往只有在这些化合物在空气、水和土壤中广泛分布之后才会显现出来。这在很大程度上是由于它们在环境中降解形成比母体化合物毒性更大的意想不到的产物。这个项目的重点是含氮化合物。目标是测量这一组选定的成员，包括杀虫剂和药品，在与大气成分接触时降解的速度，并确定形成的产物。该项目产生的数据将构成评估这些合成化学品在大气条件下如何降解所需的核心。通过与当地环境正义社区组织的合作，来自历史上弱势社区的高中生将在夏季加入该团队，在他们的实验室工作。该研究还将为本科生和博士后提供实验与理论结合的培训，以解决当前重要的环境问题。将探索两种不同的与环境相关的氧化系统：羟基自由基（OH）从上到下的氧化，代表气相OH与固体的碰撞；羟基氧化从下到上，代表由亚硝酸盐离子或TiO2底物产生的OH对吸附有机物的氧化。自上而下的研究将使用衰减全反射-傅里叶变换红外(ATR)-FTIR光谱或流动系统中有机颗粒的原位氧化来探测有机薄膜的氧化。自下而上的研究将使用固体亚硝酸盐或TiO2在水的存在下光解产生的OH。有机物的损失和产物的形成将使用红外、紫外和各种质谱技术进行监测。利用半经验量子化学计算预测OH与有机物之间最强结合配合物的结构，并将分子动力学模拟应用于每个配合物，以便为实验结果提供分子基础的见解。这种实验和理论的结合将有助于阐明OH氧化在这两种不同氧化系统对这些合成化合物的降解和命运中的作用。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

With support from the Environmental Chemical Sciences Program in the Division of Chemistry, Professor Barbara Finlayson-Pitts and her team at the University of California, Irvine will study the degradation of contaminants of emerging concern in the environment. These include a broad spectrum of human-made products, including pesticides, pharmaceuticals, and consumer products. Their deleterious impacts on humans and the environment often become apparent only after such compounds have become distributed widely in air, water, and soils. This is to a significant extent due to their degradation in the environment to form unanticipated products that are more toxic than the parent compound. The focus of this project is on compounds that contain nitrogen. The goals are to measure how fast selected members of this group, which includes pesticides and pharmaceuticals, degrade on contact with atmospheric constituents, and to identify the products that are formed. The data generated in this project will form the core needed to assess how these synthetic chemicals are degraded under atmospheric conditions. Through a partnership with a local environmental justice community group, high school students from historically disadvantaged communities will join the team to work in their labs during the summer. The proposed research will also provide training to undergraduates and postdoctoral fellows in the integration of experiment and theory to address current important environmental problems.Two different environmentally relevant oxidation systems will be explored: hydroxyl radical (OH) oxidation from the top down, representing gas phase OH impinging on a solid, and OH oxidation from the bottom up, representing oxidation of an adsorbed organic by OH generated from a nitrite ion or TiO2 substrate. Top-down studies will probe the oxidation of thin films of the organics using attenuated total reflectance-Fourier transform infrared (ATR)-FTIR spectroscopy or in situ oxidation of organic particles in a flow system. Bottom-up studies will use OH from photolysis of solid nitrite salts or TiO2 in the presence of water. Loss of the organics and formation of products will be monitored using IR, UV and a variety of mass spectrometric techniques. The structures of the strongest binding complexes between OH and the organics will be predicted using semi-empirical quantum chemical calculations, and molecular dynamics simulations will be applied to each of these complexes in order to provide insights into the molecular basis for the experimental results. This combination of experiment and theory will help elucidate the role of OH oxidation in the degradation and fates of these synthetic compounds by these two different oxidation systems.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.