Characteristics of Atmospheric VOCs Distribution in the Guro Area of Seoul Using PTR-ToF-MS

This study monitored volatile organic compounds (VOCs) in a mixed residential-industrial area of Guro-gu, Seoul, continuously from December 2024 to July 2025 using Proton Transfer Reaction-Time of Flight-Mass Spectrometry (PTR-ToF-MS). We comprehensively analyzed the concentration, compositional proportion, seasonal variation, high-concentration episode frequencies, and diurnal patterns of oxygenated VOCs (OVOCs), anthropogenic VOCs (AVOCs), and biogenic VOCs (BVOCs). The average total VOC (TVOC) concentration was 31.54 ± 17.90 ppb, dominated by OVOCs (64.5%), followed by AVOCs (33.0%), and BVOCs (2.5%). The summer concentrations of all VOC groups were 1.9–2.0 times higher than those in winter. Diurnal variation analysis indicated that certain OVOCs (e.g., acetaldehyde and acetone) exhibited patterns driven by daytime secondary photochemical formation, whereas methanol and acetonitrile were primarily influenced by direct emissions and mixing-height variations. Isoprene showed an atypical increase in concentration in the evening, attributed to accumulation within a shallow boundary layer rather than direct emissions. Correlation analysis with benzene as a primary emission tracer revealed that winter VOC concentrations were predominantly governed by primary emissions (r2=0.53–0.87), whereas summer daytime correlations declined markedly, implicating secondary photochemical formation of OVOCs and biogenic emission of isoprene. This study highlights the substantial contribution of OVOCs to urban atmospheres and underscores the need for season- and time-specific VOC management strategies.