Heterogeneous and Photochemical Transformations on Aerosol Surfaces: Understanding the Link between Hydrogen Peroxide and Carbonates Using Carbon and Oxygen Triple Isotopes

该项目采用了一种新的方法来测量过氧化氢和碳酸盐的原位形成，使用碳和氧三重同位素来帮助阐明气溶胶表面的非均质化学转化。臭氧分子在同位素上是独特的，因为它在氧的较重同位素中具有最高的富集（70-120%），并且作为涉及臭氧相互作用的化学反应的天然示踪剂。由于过氧化氢是在气溶胶表面形成的，在实验室中，臭氧、水和CaO对气溶胶表面新形成的过氧化氢的o -三重同位素测量表明，臭氧向碳酸盐的异常转移是通过过氧化氢进行的。本项目对La Jolla CA的环境空气进行了夜间和日间气溶胶采样（12h采样），以寻找大气中粗粒和细粒气溶胶中碳酸盐和过氧化氢的13C和氧三同位素组成（17O和18O）的昼夜差异。本项目中的同位素分析将有助于阐明气溶胶表面非均相反应机理的分子水平细节。这项工作将增强我们对气溶胶辐射特性、氧同位素在冰芯数据中的作用、气溶胶运输对生态系统的影响以及气溶胶对健康的影响的理解。研究结果将解决气溶胶表面薄膜的问题，同时在基础物理化学的重要领域取得进展。

This project incorporates a novel approach for measuring in-situ formation of peroxide and carbonates using carbon and oxygen triple isotopes to help elucidate heterogeneous chemical transformations on aerosol surfaces. The ozone molecule is unique isotopically as it possesses the highest enrichment (70-120%) in the heavier isotopes of oxygen and serves as a natural tracer of chemical reactions involving ozone interaction. Since hydrogen peroxide is formed on aerosol surfaces, O-triple isotopic measurements of the newly formed peroxide on aerosol surfaces in the laboratory with ozone, water, and CaO indicate that the transfer of anomaly from ozone to carbonates proceeds via peroxide. This project employs both night and daytime aerosol sampling (12h sampling) of ambient air in La Jolla CA to look for day/night differences in 13C and oxygen triple isotopic composition (17O and 18O) of atmospheric carbonates and hydrogen peroxide in coarse and fine fractions of aerosols. The isotopic analyses in this project will help elucidate the molecular-level details of the mechanisms of heterogeneous reactions at aerosol surfaces.This effort will enhance our understanding of the radiative properties of aerosols, the role of oxygen isotopes in ice core data, impacts of aerosol transport to ecosystems, and health impacts of aerosols. The results will address the issue of thin films on aerosol surfaces while at the same time make progress in areas of importance to fundamental physical chemistry.