title: Atmospheric peroxides in a polluted subtropical environment: seasonal variation, sources and sinks, and importance of heterogeneous processes.
abstract: Hydrogen peroxide (H2O2) and organic peroxides play an important role in atmospheric chemistry, but knowledge of their abundances, sources, and sinks from heterogeneous processes remains incomplete. Here we report the measurement results obtained in four seasons during 2011-2012 at a suburban site and a background site in Hong Kong. Organic peroxides were found to be more abundant than H2O2, which is in contrast to most previous observations. Model calculations with a multiphase chemical mechanism suggest important contributions from heterogeneous processes (primarily transition metal ion [TMI]-HOx reactions) to the H2O2 budget, accounting for about one-third and more than half of total production rate and loss rate, respectively. In comparison, they contribute much less to organic peroxides. The fast removal of H2O2 by these heterogeneous reactions explains the observed high organic peroxide fractions. Sensitivity analysis reveals that the role of heterogeneous processes depends on the abundance of soluble metals in aerosol, serving as a net H2O2 source at low metal concentrations, but as a net sink with high metal loading. The findings of this study suggest the need to consider the chemical processes in the aerosol aqueous phase when examining the chemical budget of gas-phase H2O2.
authors.affiliation: Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University , Hong Kong, China.
authors.forename: Jia
authors.initials: J
authors.lastname: Guo
authors.forename: Andreas
authors.initials: A
authors.lastname: Tilgner
authors.forename: Chungpong
authors.initials: C
authors.lastname: Yeung
authors.forename: Zhe
authors.initials: Z
authors.lastname: Wang
authors.forename: Peter K K
authors.initials: PK
authors.lastname: Louie
authors.forename: Connie W Y
authors.initials: CW
authors.lastname: Luk
authors.forename: Zheng
authors.initials: Z
authors.lastname: Xu
authors.forename: Chao
authors.initials: C
authors.lastname: Yuan
authors.forename: Yuan
authors.initials: Y
authors.lastname: Gao
authors.forename: Steven
authors.initials: S
authors.lastname: Poon
authors.forename: Hartmut
authors.initials: H
authors.lastname: Herrmann
authors.forename: Shuncheng
authors.initials: S
authors.lastname: Lee
authors.forename: Ka Se
authors.initials: KS
authors.lastname: Lam
authors.forename: Tao
authors.initials: T
authors.lastname: Wang
mesh_terms: D000336:Aerosols; D000393:Air Pollutants / Q000032:analysis*; D003198:Computer Simulation; D004784:Environmental Monitoring / Q000379:methods*; D006723:Hong Kong; D006861:Hydrogen Peroxide / Q000032:analysis; D008670:Metals / Q000032:analysis; D008956:Models, Chemical; D010545:Peroxides / Q000032:analysis*; D055668:Photochemical Processes; D012621:Seasons; D014329:Tropical Climate; D055549:Volatile Organic Compounds / Q000032:analysis*
chemical_list: D000336:Aerosols; D000393:Air Pollutants; D008670:Metals; D010545:Peroxides; D055549:Volatile Organic Compounds; D006861:Hydrogen Peroxide