Atmospheric chamber measurements of H2SO4: characterization of formation and loss rates during the ozonolysis and aerosol formation studies

Abstract

International audienceSulphuric acid, H2SO4, has been identified to play major role in atmospheric new particle formation and in subsequent particle growth. The oxidation of sulfur dioxide (SO2) to sulfur trioxide (SO3) initiated by the reaction with the hydroxyl radicals (OH) is assumed to be the dominant formation pathway of sulfuric acid (H2SO4) in the troposphere. It has been suggested in the recent years that the reactions of Criegee Intermediates (CIs) with SO2 may also contribute to the H2SO4 formation, although the significance of this pathway compared to the reaction of OH with SO2 is still under discussion. As the ozonolysis of anthropogenic and biogenic terpenes emitted into the atmosphere may represent an important source of OH and CIs a better understanding of the ozonolysis mechanism in relation to the H2SO4 formation is required. In this study, we present the results obtained during the investigation of the ozonolysis of several unsaturated volatile organic compounds, including tetramethylethylene, α-pinene and limonene, using a newly constructed large atmospheric simulation chamber, HELIOS (ICARE-CNRS, Orléans, France). The HELIOS facility consists of a large outdoor simulation chamber (volume of 90 m3) equipped with a wide range of in-situ on-line and off-line analytical instrumentation (FTIR, PTR-TOF-MS, GC-MS, CIMS (OH and H2SO4), SMPS, Figaero-API-TOF-CIMS, HCHO monitor and others). The results of kinetic and mechanistic studies of the reactions of different CIs with SO2 induced by the ozonolysis of the studied VOCs under different conditions will be presented. The H2SO4 loss on the Teflon chamber wall and by the aerosol uptake were characterized using direct H2SO4 and particle measurements. Keywords: ozonolysis, Criegee Intermediate, sulfur dioxide, sulfuric acid, HELIO