[Characterization of Ambient Volatile Organic Compounds, Source Apportionment, and the Ozone-NO-VOC Sensitivities in...

Liucheng county, as a suburb of Liuzhou City in Guangxi province, has a prominent ozone (O₃) pollution problem; however, there have been no relevant analyses of the cause of local O₃ pollution reported. In order to investigate the causes of O₃ pollution, an online observation of 116 VOCs with a time resolution of 1 h was carried out in Liucheng county from October 1^st to 15^th, and the sensitivity of ozone to the relative changes in the NO and VOCs was analyzed. The results showed that the average value of φ［total volatile organic compounds (TVOCs)］ during the observation period was 27.52×10^-9, and the average value of φ(TVOCs) during the polluting process (October 1^st to 6^th) was 32.15×10^-9, which was 32.79% higher than that of the non-pollution process (October 8^th to 15^th). In terms of species concentration, oxygenated volatile organic compounds (OVOCs) contributed the highest, accounting for 43.70%, followed by alkanes (23.00%), aromatics (11.75%), and halocarbons (7.35%). In terms of ozone formation potential (OFP), OVOCs contributed the highest (41.96%) to OFP, followed by aromatics (32.60%) and alkenes (17.92%). During the observation period, VOCs mainly came from motor vehicle emissions (32.44%), biomass combustion sources (29.31%), solvent use sources (16.43%), plant sources (11.34%), and chemical industry emissions (10.49%). The contribution ratios of solvent use sources and plant sources in the pollution process increased by 28.58% and 28.53%, respectively. The EKMA curve shows that, during the observation period, Liucheng county was in a synergistic control area for VOCs and nitric oxide (NO). Therefore, in the high ozone-occurrence autumn of Liucheng county, the key will be to reduce both VOCs and NO emissions.