Source Apportionment of Ambient VOCs in Summer in Urban Shenyang Based on Photochemical Loss Correction
Online measurements of volatile organic compounds (VOCs) were conducted in the central urban area of Shenyang from June 1 to August 31, 2022, to analyze concentration levels and ozone formation potential (OFP). The initial concentrations of VOCs were estimated using the photochemical age parameter method to correct for photochemical losses. Positive matrix factorization (PMF) was applied for source apportionment. The average mass concentration of total VOCs (TVOCs) was (27.29 ± 15.96) μg·m−3, with alkanes (50.3%) as the dominant component; key species included propane, ethane, methanethiol, and ethylene. The OFP of TVOCs was (64.30 ± 66.41) μg·m−3, with alkenes (63.5%) as the main contributor; key reactive species were ethylene, propylene, m/p-xylene, toluene, and isoprene. Daytime photochemical loss of VOCs reached 2.40 μg·m−3, with alkenes (67.1%) dominating. PMF based on initial concentrations identified five major sources: vehicle emissions (56.2%), solvent usage (21.5%), combustion sources (8.9%), industrial emissions (7.5%), and natural sources (5.9%). Compared to PMF results based on directly monitored concentrations, contributions from vehicle emissions, combustion sources, and solvent usage decreased, while industrial emissions increased. The organic chemical industry source was not identified, and a new natural source contribution was recognized. These findings underscore the importance of photochemical loss correction in source apportionment and highlight key species and sources for ozone pollution control in Shenyang.