Gas-particle partitioning and yield of organic nitrate under different VOC, NOx, and oxidation conditions

Particulate nitrate is a major aerosol component worldwide that acts as a reservoir of urban nitrogen oxides (NO_x=NO+NO₂). Chemical reactions of NO_x with volatile organic compounds (VOCs) will form organic nitrates that undergo gas-particle partitioning and therefore may influence the lifetime and transport of nitrogen compounds, impacting their deposition on ecosystems.

In this study, we use data collected in chamber experiments and in ambient air to investigate how emission profiles and ambient conditions affect the gas-particle partitioning and the yield of organic nitrate. Chamber studies during the SAPHIR-CHANEL campaign show that monoterpenes, higher NO_x, and reactions with the nitrate radical in the absence of light favor the formation of organic nitrate in urban NO_x-VOC mixtures. Similar results are found at a continuous monitoring site in rural central Netherlands where the type of organic nitrate during pollution episodes depends on the airmass source and the corresponding VOC and NO_x profiles. By combining results from chamber and ambient measurements, we provide new insights into atmospheric organic nitrate chemistry.