Ozone formation potential related to the release of volatile organic compounds (VOCs) and nitrogen oxide (NOX) from a typical industrial park in the Pearl River Delta†

Ozone (O₃) pollution has been recognized as the major air pollution in the Pearl River Delta (PRD) region, South China. Understanding O₃ formation sensitive to volatile organic compound (VOC)- and nitrogen oxide (NO_X)-limited regimes is a key step for alleviating O₃ pollution. Herein, measurements of VOCs, NO_X and O₃ were simultaneously performed at multi sampling sites in an industrial park of the PRD region during June, 2020. VOCs/NO_X ratios ranged from 0.5 to 5.7, suggesting that the O₃ formation was in the VOC-limited regime in the industrial park. The estimated O₃ formation potential (OFP) of VOCs showed that alkenes and aromatic hydrocarbons from motor vehicles and industrial sources contributed to 40% and 39% of the O₃ formation, respectively, in the industrial park. However, a low O₃ level (<50 ppb) was observed in the region where high OFP values (>194 ppb) were estimated. Further analysis found that the concentration of NOx (25 ± 10 ppb) in the high O₃ region was lower than that (36 ± 6 ppb) in the low O₃ region, mostly due to the titration reaction of NO and O₃ to form NO₂, therefore leading to the consumption of O₃. This result implies that NO_X control was not conducive to the O₃ pollution in the study region. Thus, O₃ pollution control in the study region should be taken into consideration in terms of the effect of NO_X titration and control of VOC emissions.