Experimental Characterization of Cyclic Siloxane Oxidation with Hydroxyl Radicals, Oxidation Flow Reactor (OFR) Results.

Cyclic volatile methyl siloxanes (cVMS), such as decamethylcyclopentasiloxane (D5), are manmade high production chemicals used in a variety of personal care products that their primary fate in the atmosphere is oxidation with hydroxyl radical. While there are many studies on the fate of the parent compound in the atmosphere, the fate of its oxidation product in the atmosphere is less studied. In this work, we perform chamber experiments to investigate particulate products of D5 oxidation with hydroxyl radicals in the Potential Aerosol Mass Oxidation Flow Reactor (PAM OFR). In particular, we inject D5 into the PAM OFR using different injection systems and oxidize it with hydroxyl radicals to generate aerosols, varying concentration, residence time, OH/HO2 ratio, and presence and composition of seed aerosols. Characterization is by aerosol yield and particle size distribution. The mass and size distribution of generated aerosols is determined by Scanning Mobility Particle Sizer (SMPS) and compared limonene oxidation yields and to previous work on D5 oxidation at higher precursor concentrations.