Radical Clouds: Determining How Light Generates Free Radicals in Cloud Droplets in the Atmosphere

Polycyclic aromatic hydrocarbons (PAH) are organic molecules capable of forming free radicals, specifically reactive oxygen species (ROS) in the environment. These highly reactive radicals are created in the environment when fuel is burned. An excess of ROS can cause significant damage when ingested or inhaled because they react with chemicals in the body, resulting in adverse health effects including cardiovascular disease and oxidative stress (Brook et al. 2010). Previous studies have shown that brown carbon reacts with iron in the air makes iron more soluble in water. Soluble iron causes even more ROS to be made. To characterize the pathway for these PAH molecules becoming brown carbon, this project studied the reactive oxygen species formed from the intermediates of brown carbon, naphthoquinone. Electron paramagnetic resonance spectroscopy (EPR) was used to study these free radicals when in the presence of a spin trap which stabilizes the free radical for study. The results have suggested that there are intermediate reactive oxygen species in the pathway of naphthoquinone becoming brown carbon. Further exploring of these pathways further could be a novel concept to mediate the production of brown carbon in the environment.