摘要:

Atmospheric peroxides play important roles in atmospheric chemistry, acting as reactive oxidants and reservoirs
of HO_x and RO_x radicals. Field measurements of atmospheric peroxides were conducted over urban Beijing from
2015 to 2016, including dust storm days, haze days and different seasons. We employed a box model based on
RACM2 mechanism to conduct concentration simulation and budget analysis of hydrogen peroxide (H₂O₂) and
peroxyacetic acid (PAA). In this study, heterogeneous reaction is found to be a significant sink for atmospheric
H₂O₂ and PAA in urban Beijing. Here, we recommend a suitable uptake coefficient formula considering the
water effect for model research of peroxides. It is found that H₂O₂ and PAA unexpectedly maintained considerable
concentrations on haze days, even higher than that on non-haze days. This phenomenon is mainly
ascribed to relatively high levels of volatile organic compounds and ozone on haze days. In addition, high levels
of water vapor in pollution episode can promote not only the heterogeneous uptake to aerosol phase but also the
production of H₂O₂. Atmospheric PAA formation is suggested to be sensitive to alkenes and NO_x in urban
Beijing. In particular, with the help of peroxides, sulfate formation rate from heterogeneous uptake could increase
by ∼4 times on haze days, indicating the potential effect of peroxides on enhancement of aerosol oxidative
property and secondary sulfate formation.

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