The Chemistry of Hydrogen Peroxide in Cloudwater

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Acid rain has become a major concern during the past decade. Rain has a natural acidity due to dissolved carbon dioxide. The acidity of rain is made even greater by the emission of certain gases from human endeavors. Coal burning power plants emit substantial quantities of sulfur dioxide and high temperature combustion processes, such as automobile engines, yield nitrogen oxides. These gases are eventually converted into acids. A description of the chemical processes involved in changing these gases into acids and the speed of these reactions are important keys to understanding the geographic distribution of acid rain and the impact of particular sources of the precursor gases. Sulfur dioxide dissolves into water droplets which provide a chemical medium for the oxidation of sulfur dioxide into acid. A vital species in this reaction is hydrogen peroxide. It is therefore important to understand the mechanisms by which hydrogen peroxide is formed and destroyed in the atmosphere. Hydrogen peroxide is highly soluble and is known to have deleterious effects on plants. In contrast to the gas phase chemistry of hydrogen peroxide, the chemistry in droplets is not well understood. This project focuses on examining the aqueous chemistry of hydrogen peroxide with emphasis on laboratory studies of the reactions that form and destroy hydrogen peroxide under conditions approximating those found in cloudwater. The chemistry will be investigated by the technique of radiolysis in synthetic precipitation, i. e., aqueous solutions of known composition approximating that of cloudwater. These laboratory studies will provide data to test the applicability of various models of cloud chemistry.