A novel approach to source apportionment of VOCs with high potential for ozone and SOA formation using...

Volatile organic compounds (VOCs) include a wide range of chemicals, some of which act as precursors to tropospheric ozone and secondary organic aerosols. These compounds are released into the atmosphere from a wide range of sources. We conducted a source apportionment analysis of the hourly concentrations of 16 VOCs with the highest potential to contribute to O₃ and SOA formation. VOCs were monitored over an 18-month period in an urbanized and industrialized coastal region in Brazil. A novel approach not previously utilized in the literature, incorporating the Positive Matrix Factorization (PMF) model while accounting for intraday VOC patterns and their dependence on wind direction was used. This method enabled us to identify source contributions during specific times of the day when certain sources had stronger impact. The analysis revealed five factors representing contributions from solvent usage (6-13 %), industrial processes (11-13 %), fuel evaporation (4-13 %), vehicular exhaust (43-46 %), and coke ovens (25-26 %). Some VOCs exhibited hourly variations influenced by both time of day and wind direction, and their respective lifetimes, with long-lived species such as benzene, n-pentane, and ethylbenzene being prevalent between 00:00 and 11:59, correlating with aged air masses, while short-lived species like 1,2,4-trimethylbenzene showed greater directional variability, linked to prevailing winds, indicating recent contributions, suggesting the likely locations of sources. This intraday variation resulted in unique source impacts, highlighting a time dependence that influences source apportionment throughout the day. As a result, source apportionment based on these periodic VOC variations provided valuable insights for developing targeted mitigation strategies.