Characterization and source apportionment of volatile organic compounds in Hong Kong: A 5-year study for three different archetypical sites.

Initial success has been achieved in Hong Kong in controlling primary air pollutants, but ambient ozone levels kept increasing during the past three decades. Volatile organic compounds (VOCs) are important for mitigating ozone pollution as its major precursors. This study analyzed VOC characteristics of roadside, suburban, and rural sites in Hong Kong to investigate their compositions, concentrations, and source contributions. Here we show that the TVOC concentrations were 23.05 ± 13.24, 12.68 ± 15.36, and 5.16 ± 5.48 ppbv for roadside, suburban, and rural sites between May 2015 to June 2019, respectively. By using Positive Matrix Factorization (PMF) model, six sources were identified at the roadside site over five years: Liquefied petroleum gas (LPG) usage (33%-46%), gasoline evaporation (8%-31%), aged air mass (11%-28%), gasoline exhaust (5%-16%), diesel exhaust (2%-16%) and fuel filling (75-9%). Similarly, six sources were distinguished at the suburban site, including LPG usage (30%-33%), solvent usage (20%-26%), diesel exhaust (14%-26%), gasoline evaporation (8%-16%), aged air mass (4%-11%), and biogenic emissions (2%-5%). At the rural site, four sources were identified, including aged air mass (33%-51%), solvent usage (25%-30%), vehicular emissions (11%-28%), and biogenic emissions (6%-12%). The analysis further revealed that fuel filling and LPG usage were the primary contributors to OFP and OH reactivity at the roadside site, while solvent usage and biogenic emissions accounted for almost half of OFP and OH reactivity at the suburban and rural sites, respectively. These findings highlight the importance of identifying and characterizing VOC sources at different sites to help policymakers develop targeted measures for pollution mitigation in specific areas.