Secondary Organic Aerosol Formation from OH-Initiated Oxidation of o-cresol

Cecilie Carstens, David Bell, FÉLIX SARI DORÉ, Jens Top, Clément Dubois, Yanjun Zhang, Sebastien Perrier, Imad El Haddad, Matthieu Riva, CNRS-IRCELYON

     Abstract Number: 233
     Working Group: Aerosol Chemistry

Abstract
Secondary organic aerosols (SOA) have significant effects on visibility, human health, and climate. They are formed in the atmosphere from the oxidation of volatile organic compounds (VOCs), leading to less volatile oxidation products that can subsequently partition into, or react with existing, aerosol particles. Biomass burning (BB) is the largest combustion-related source of VOCs in the atmosphere, and extreme fires has been estimated by United Nations Environment program to increase with up to 30% by 2050, which underlines the necessity to study how BB affects the SOA formation.

Recent studies have shown that oxygenated aromatic compounds account for almost 60% of the SOA formed under dry conditions from BB emissions. In this study we used an oxygenated aromatic BB marker, i.e., o-cresol (C₇H₈O), to study the chemical processes leading to the formation of biomass-derived SOA. Experiments were performed in a 9m³ Teflon atmospheric simulation chamber at the Paul Scherrer Institute. Numerous mass spectrometers were used to investigate gas- and particle-phase oxidation processes under wet and dry conditions.

Preliminary results show that OH-initiated oxidation of o-cresol leads to the subsequent formation of SOA under wet and dry conditions. Notably, humidity greatly influences the distribution of particle-phase products, especially for nitrogen-containing compounds (ONs). Particulate ONs are formed to a greater extent under wet conditions. This can potentially influence the recycling of nitrogen oxides (NO_x) and change the NO_x budget on a global scale with the increase of BB from e.g., wildfires.