[Characteristics and Source Apportionment of Ambient VOCs in Lhasa]

Due to the high altitude of plateau cities and strong ultraviolet radiation, the sources and fates of volatile organic compounds show unique characteristics. In this study, the atmospheric volatile organic compound (VOCs) samples were collected at two urban sites and one background site using tank sampling in Lhasa in 2019, and then the composition, concentration, and sources were characterized. The results showed that the average φ(VOCs) in Lhasa was 49.83×10^-9, of which the proportion of alkanes was the highest (61%), followed by OVOCs (12%), halogenated hydrocarbons (9%), olefin (9%), aromatic hydrocarbons (5%), and alkynes (4%). The respective contributions of VOCs sources at urban sites, such as Barkhor Street and Radiation Station in Lhasa, were as follows:combustion (64% and 48%) > traffic emission (17% and 31%) > industrial emission (14% and 14%) > solvents and coatings (3% and 3%) ≈plant+background (2% and 4%). The contribution of combustion was large mostly due to local incense burning (especially at Barkhor Street) and heating emissions. Traffic emissions contributed about one third to the VOCs at Radiation Station, which is related to its proximity to the transportation hub and the storage and logistics center upwind. Industrial emissions have a regional impact on ambient VOCs. Under the synergistic influence of meteorology and emissions, VOCs concentration, composition characteristics, and source contribution showed obvious seasonal variations and site differences in the Lhasa area.