1 Heterogeneous Chemistry and Tropospheric Ozone

Ozone is produced in the troposphere by gas-phase oxidation of hydrocarbons and CO catalyzed by hydrogen oxide radicals (HOx ≡ OH + peroxy radicals) and nitrogen oxide radicals (NOx ≡ NO+NO2). Heterogeneous chemistry involving reactions in aerosol particles and cloud droplets can perturb O3 concentrations in a number of ways including production and loss of HOx and NOx, direct loss of O3, and production of halogen radicals. Current knowledge and hypotheses concerning these heterogeneous processes are reviewed, and recommendations for O3 models are presented. Suggestions for experimental research are offered.