Characterization and risk assessment of ambient VOCs in Qingyang city, China.

INTRODUCTION: Atmospheric volatile organic compounds (VOCs) are critical pollutants that significantly affect urban air quality and drive photochemical reaction processes. Industrial cities, especially those in western China, often face unique VOC pollution characteristics due to regional industrial structures and geographical conditions. OBJECTIVE: This study aimed to characterize VOC composition, concentrations, photochemical reactivity, sources, and health risks in a western Chinese industrial city. METHODS: Gaseous VOC samples were collected from four sampling sites (three urban sites and one rural site), and their compositional characteristics were analyzed in detail. To evaluate the photochemical reaction activity of the detected VOCs, the ozone formation potential (OFP) and propylene equivalent concentration (Propy-Equiv) method were adopted. Principal Component Analysis (PCA) was applied to identify VOC sources. Additionally, a health risk assessment was conducted to identify key pollutants posing non-carcinogenic risks. RESULTS: The results showed that the average volume fraction of total volatile organic compounds (TVOCs) in the atmosphere of the study city was 47.94 ± 23.04 ppbv, with a total of 112 VOC species detected. Based on their molecular structures, these VOCs were classified into six categories, including 29 alkanes, 11 alkenes, 1 alkyne, 16 aromatics, 34 halogenated hydrocarbons (HHCs), and 21 oxygen-containing organic compounds (OVOCs). The volume ratio contributions of these categories to TVOCs were as follows: OVOCs (29.17%), alkanes (27.12%), HHCs (19.86%), aromatic hydrocarbons (12.33%), alkenes (10.67%), and alkynes (0.86%). Furthermore, TVOC concentrations were significantly higher in urban areas than in rural areas, and the photochemical reactivity of atmospheric components in urban areas was also higher than that in rural areas. Health risk assessment results indicated that acrolein was the primary species contributing to non-carcinogenic risks. CONCLUSION: Controlling alkenes and OVOCs is critical to reduce VOC pollution and photochemical risks. These findings support local air quality management.