Photochemistry of Secondary Organic Aerosol Formed from Oxidation of Monoterpenes

Secondary organic aerosol (SOA) formed from atmospheric oxidation of monoterpenes has a complex and highly dynamic chemical composition. This chapter focuses on photochemical processes occurring inside biogenic SOA particles produced by oxidation of monoterpenes. The SOA material is found to significantly absorb solar radiation in the tropospheric actinic window (k > 300 nm). The ensuing photolysis of SOA constituents modifies the SOA chemical composition and leads to emission of small volatile molecules back into the gas-phase. A large number of observed products can be explained by photolysis of organic peroxides and carbonyls. These photochemical processes are likely to occur on atmospherically relevant time scales, and affect chemical properties and toxicity of monoterpene SOA particles.