The role of atmospheric volatile organic compounds (VOCs) in ozone formation around China's largest plywood manufacturer

The volatile organic compounds (VOCs) are a dominant contributor to the formation of ozone (O-3) in Linyi, the plywood capital of China. However, the temporal variations and source origins of VOCs in Linyi remain unclear. This study gathered ambient air samples (n = 214) from the urban center of Linyi during the period April to October of 2021-2023. The total volatile organic compounds (TVOCs) concentrations ranged from 28 ppbv to 32 ppbv with oxygenated volatile organic compounds (OVOCs) taking the large portion (50.76 %) of TVOCs, followed by alkanes (28.11 %), aromatics (13.71 %), alkenes (6.66 %), and alkynes (0.76 %). The OVOCs (44.10 %) were the dominant contributors to ozone formation potential (OFP). Formaldehyde, an OVOC and particular pollutant from plywood industries contributed the most to OFP (similar to 21.60 %). The average concentration of TVOCs in 2022 was the lowest (28.61 +/- 10.76 ppbv), with VOCs species, such as isobutane and propane having the lowest concentrations in 2022 (p < 0.05), reflecting a decrease in transportation activity due to the impacts of pandemic lockdowns. Concentrations of OVOCs were annually increasing because of the annual growth of plywood yield. The TVOCs and OVOCs levels were significantly correlated to O-3 levels (p < 0.01). The concentrations of TVOCs and OVOCs as well as O-3 were highest in June and September (p < 0.05), when the temperature and the degree of photochemical reactions were high. The source apportionment analysis found that plywood industries were the main source (32.90 %) of TVOCs, followed by liquefied petroleum gas (LPG, 21.32 %). Trajectory statistical models (TSM) analysis suggested that Linyi is greatly affected by regional transport from the southwest (31.63 %). This study provides new insights into the mitigation and management of VOCs and O-3 pollution in plywood industry cities.