Isoprene Forms Secondary Organic Aerosol through Cloud Processing: Model Simulations
Isoprene accounts for more than half of non-methane volatile organics globally. Despite extensive experimentation, homogeneous formation of secondary organic aerosol (SOA) from isoprene remains unproven. Herein, an in-cloud process is identified in which isoprene produces SOA. Interstitial oxidation of isoprene produces water-soluble aldehydes that react in cloud droplets to form organic acids. Upon cloud evaporation new organic particulate matter is formed. Cloud processing of isoprene contributes at least 1.6 Tg yr-1 to a global biogenic SOA production of 8?40 Tg yr-1. We conclude that cloud processing of isoprene is an important contributor to SOA production, altering the global distribution of hygroscopic organic aerosol and cloud condensation nuclei.