Investigating the Impacts of Nonacyl Peroxy Nitrates on the Global Composition of the Troposphere Using a 3-D Chemical Transport Model, STOCHEM-CRI

Abstract

Nonacyl peroxy nitrates, RO2NO2, act as a reservoir species for NOx in the upper troposphere. The low thermal stability of these compounds means that they only become a significant sink of NOx at the low temperatures observed in the upper troposphere. The chemical processes involved with the formation and degradation of methyl peroxy nitrate (CH3O2NO2) and an additional 44 RO2NO2 have been incorporated into the global three-dimensional chemical transport model, STOCHEM-CRI. The study investigates the effect of the addition of RO2NO2 chemistry on the budget of NOx, which in turn impacts the ozone, hydroxyl radical (OH), and nitrate radical (NO3) formation. This investigation found that the addition of CH3O2NO2 led to an increase in the tropospheric burdens of NOx (+3.0%), ozone (+2.0%), OH (+4.0%), and NO3 (+8.8%). However, the other 44 RO2NO2 contribute a significant increment of tropospheric global burdens of NOx (+4.4%), ozone (+3.4%), OH (+5.5%), and NO3 (+11.1%) with the largest mixing ratios of NOx of up to 25%, ozone up to 14%, OH up to 20%, and NO3 up to 50%. The increase in the global burden of oxidizing species such as OH due to the addition of 44 other RO2NO2 led to a significant decrease in the lifetimes of greenhouse gases such as methane (∼6%). The modeled mixing ratios of CH3O2NO2 were in reasonable agreement with measurements, the only extensive data set available.