Measurements of changes in the atmospheric partitioning of bifunctional carbonyls near a road in a suburban area

Bifunctional carbonyls are ubiquitous in the atmosphere and are important contributors to atmospheric aerosols through heterogenous reactions. However, the actual contributions of bifunctional carbonyls to atmospheric aerosols have been little measured because of their capacity to coexist in both the gaseous phase and the particulate phase, making it difficult to sample them in both phases simultaneously. Using a short time resolution (2 h), we measured the atmospheric partitioning of semivolatile species to understand their contributions to atmospheric aerosols. Our results indicate that equilibrium between the gaseous phase and the particulate phase was due not only to thermodynamic partitioning but also to an aging process. Fresh emissions from motor vehicles affected the partitioning, and partitioning coefficients stabilized when the aerosols aged. The contribution of bifunctional carbonyl compounds to atmospheric aerosols was 3–8 orders of magnitude higher than that estimated by thermodynamic predictions, corroborating previous findings.