Within the atmospheric environment, multiphase media such as fog and clouds can differ substantially with respect to temperature, pH, and ionic strength depending on location, time of day, or air mass source. Understanding the extent that these factors affect atmospheric chemical processes would allow for the determination of the most adverse conditions for which the most reactivity is prone to occur. Evaluating the chemical processes within atmospheric droplets has an added complexity because these reactions occur both in the bulk aqueous phase and at the air-water interface. In this study, a thin film flow-tube reactor is used to assess how temperature, pH, and ionic strength, as well as the concentration of oxygen, affect reactions at the air-water interface. The thin film reactor allows for the simulation of atmospheric droplets in the micrometer scale by varying the aqueous film thickness within different experiments. In varying the film thickness (i.e. the film volume) over a known surface area, the thin film reactor also gives the advantage in that both bulk phase and interfacial properties can be obtained from a single reactor. In order to quantify how all these atmospheric conditions affect interfacial processes, the reaction of benzene with hydroxyl radicals, formed from the dissociation of hydrogen peroxide in the presence of UVB light, is followed as a kinetic study. Benzene, the simplest aromatic structure, is used as a model compound because it is both a common atmospheric pollutant and its two main products, phenol and biphenyl, are straightforward to follow. The rates of degradation and formation of benzene, phenol, and biphenyl within these various conditions are evaluated and compared. Activation energies and the bulk phase and interfacial phase rate constants are also obtained. This data combined allows for a better understanding of the fate of benzene and its byproducts in atmospheric aqueous media.

Atmospheric oxidation of benzene: Effect of temperature, pH, ionic strength, and oxygen content at the air-water interface

249th National Meeting (2015)

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