Characteristics and secondary transformation potential of volatile organic compounds based on hourly variation to infer best ways to manage air quality

Abstract

Volatile organic compounds (VOCs) concentrations vary considerably across different times and locations, making high-resolution monitoring crucial for accurately representing the formation processes of secondary pollutants. In this study, we assessed the impact of hourly concentrations of VOCs and nitrogen oxides (NOx) on ozone formation potential (OFP) and secondary organic aerosol formation potential (SOAFP) at two sites in an urban-industrialized region of Brazil. The aim was to understand the effects of VOCs on SOA formation and identify optimal strategies for controlling their environmental impacts. An analysis of the urban-industrial and suburban sites revealed significant differences in pollution patterns. The region is influenced by local anthropogenic emissions such as residential/commerce (39%), vehicular exhaust (28%), industrial processes (18%), fuel evaporation (10%), and solvent usage (3%). The ES site showed higher and more varied VOC concentrations, elevated NOx, and distinct ozone production dynamics indicative of a VOC-limited regime. In contrast, the MO site exhibited lower VOC levels, suggesting a suburban pattern mainly influenced by aged air masses. Key VOCs like trimethylbenzene isomers and ethylbenzene dominate OFP calculated by measured VOCs (OFP_M) at the ES site, while a more even distribution among VOC species is observed at MO. SOAFP analysis highlights substantial contributions from benzene and ethylbenzene at both sites, with ES showing a closer match between SOAFP and measured PM_2.5 concentrations. The findings emphasize the necessity for site-specific air quality management strategies targeting major VOC contributors to effectively reduce ozone and PM_2.5 levels, thereby improving environmental health outcomes.