Distribution of Gaseous and Particulate Organic Peroxides Formed in the Ozonolysis of α-Pinene

Abstract:

Organic peroxides, an important species in the atmosphere, will affect HO_x cycling, promote SOA aging, and cause adverse health effect. However, the formation, distribution and evolution of organic peroxides are extremely complicated and still unclear. In this study, we investigate in laboratory the production of peroxides and gas-particle partitioning in the ozonolysis of α-pinene. The molar yields of hydrogen peroxide (H₂O₂), hydromethyl hydroperoxide (HMHP), performic acid (PFA), peracetic acid (PAA) and total peroxides (TPO, including unknown peroxides) and contribution of peroxides to SOA mass are carefully determined. Comparing the gaseous and particulate peroxides, we find that more than 75% peroxides formed in the ozonolysis remain in the gas phase, and water vapour will significantly influence the formation and distribution of peroxides. Such an unexpected large amount of gaseous peroxides deserves more attention, especially to their effect on HO_x cycling.