Unsaturated hydrocarbons, including alkenes, alkynes, and aromatic hydrocarbons, are important components of atmospheric volatile organic compounds (VOCs) and serve as key precursors for ozone, a major photochemical pollutant. This study aimed to characterize the sources and ozone formation potential of 29 unsaturated hydrocarbon VOCs in Beihai, a coastal city in southern China, on the basis of continuous online monitoring conducted during the summer of 2022. Continuous monitoring of unsaturated hydrocarbon VOCs in the ambient air of Beihai city during summer was conducted using a rapid online monitoring system for atmospheric VOCs. The results revealed that the total daily average concentration of unsaturated hydrocarbon VOCs was 1.21 ppbv, with an average concentration of 0.026 ppbv. The order of abundance was alkenes > aromatic hydrocarbons > alkynes. Source apportionment using the positive matrix factorization (PMF) model revealed that vehicle exhaust emissions were the primary source of unsaturated hydrocarbon VOCs in the city of Beihai, contributing 36.02%. Secondary sources included combustion sources (26.15%), solvent usage (18.55%), fuel evaporation (10.18%), and biogenic sources (9.10%). The contribution of unsaturated hydrocarbon VOCs to ozone formation was estimated using the ozone formation potential (OFP). Aromatic hydrocarbons contributed the most (51.22%), followed by alkenes (41.8%). Analysis of the diurnal variation patterns of unsaturated hydrocarbons revealed that combustion sources occurred during the night (01:00–02:00), suggesting that enhanced supervision and control measures during nighttime hours are warranted.
Wu et al. (Sat,) studied this question.