Formation of secondary organic aerosols from the reaction of γ-terpinene with ozone: yields and morphology

Abstract Atmospheric secondary organic aerosols (SOAs), formed from condensable oxidation products of anthropogenic and biogenic volatile organic compounds (VOCs), are important constituents of the atmosphere accounting for a significant fraction of ambient tropospheric aerosol. In this study, the formation of SOAs from the gas-phase ozonolysis of γ-terpinene (1-isopropyl-4-methyl-1,4-cyclohexadiene), a monoterpene emitted by many different trees (elm, cypress, water hickory, maple trees …) has been studied in an indoor atmospheric simulation chamber (CHARME), at 294 ± 2 K, atmospheric pressure, under dry conditions (relative humidity, RH The overall organic aerosol yield (Y) was determined as the ratio of the suspended aerosol mass concentration corrected for wall losses (Mo) to the total reacted γ-terpinene concentration, assuming a particle density of 1 g cm−3. The aerosol formation yield increases as the initial γ-terpinene concentration raises. The presence of an OH radical scavenger (cyclohexane) leads to a decrease in the SOA yields (they varied from 0.11 to 0.54 and from 0.16 to 0.49, without and with, an OH radical scavenger, respectively). Y is a strong function of Mo and the organic aerosol formation can be expressed by a one-product gas/particle partitioning absorption model.