Pollution Characteristics and Key Reactive Species of Volatile Organic Compounds in Beijing-Tianjin-Hebei Area, China

ABSTRACT Volatile organic compounds (VOCs) are important precursors for the formation of ground-level ozone. In this study, the hourly mixing ratio of 61 ambient VOCs species was measured from 2018 to 2019 in 10 cities in Beijing-Tianjin-Hebei (BTH) area in China. The VOCs distribution, speciation and photochemical implications also was discussed in this study. The cities with the highest mixing ratio of VOCs were in the southern part as LF, BD, HD and SJZ, while the CD and ZJK were the lowest in the north part. Alkanes were the most abundant VOCs component (50%) in all cities, while ethane and propane were the most concentrated species in all cities. The mixing ratio of VOCs was characterized as a double peak value on the daily variation curve due to the photochemical reaction intensity and the inversion layer. Also, the loss rate of OH (LOH) was calculated to evaluate the chemical reactivity of VOCs. Results illustrated that the values of LOH of alkenes and aromatics exceed the highest mixing ratio of alkanes. The study of ozone formation potential (OFP) and secondary organic aerosol formation potential (SOAp) found that alkenes and aromatics had a higher OFP and SOAp than alkanes. Based on the analytical method of the diagnostic ratios of propane/n-butane, propane/i-butane, cis-2-butane/trans-2-butane, toluene/benzene and xylene/ethylbenzene, motor vehicle emissions contributed significantly to ambient VOCs in BTH area.