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，利用碳和氧三重同位素测量原位形成的过氧化氢和碳酸盐，以帮助阐明气溶胶表面的非均相化学转化。臭氧分子在同位素上是独一无二的，因为它在较重的氧同位素中具有最高的丰度(70%-120%)，并且是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，在实验室用臭氧、水和CaO对气溶胶表面新形成的过氧化氢进行的O-三同位素测量表明，异常从臭氧到碳酸盐的转移是通过过氧化氢进行的。该项目采用加利福尼亚州拉霍亚地区环境空气的夜间和日间气溶胶采样(12小时采样)，以寻找大气碳酸盐的13C和氧三同位素组成(17O和18O)的昼夜差异以及气溶胶粗馏和细馏分中的过氧化氢。该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，这将有助于我们更好地了解气溶胶的辐射特性、氧同位素在冰芯数据中的作用、气溶胶对生态系统的影响以及气溶胶对健康的影响。这些成果将解决气溶胶表面的薄膜问题，同时在对基础物理化学具有重要意义的领域取得进展。

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.