[Characterization of Ambient Volatile Organic Compounds, Source Apportionment, and the Ozone-NO x -VOC Sensitivities in Liucheng County, Guangxi].

Liucheng county, as a suburb of Liuzhou City in Guangxi province, has a prominent ozone (O ₃ ) pollution problem; however, there have been no relevant analyses of the cause of local O ₃ pollution reported. In order to investigate the causes of O ₃ 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 _x 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 _x ). Therefore, in the high ozone-occurrence autumn of Liucheng county, the key will be to reduce both VOCs and NO _x emissions.