A comparison investigation of atmospheric NMHCs at two sampling sites of Beijing city and a rural area during summertime

Abstract Atmospheric non-methane hydrocarbons (NMHCs) were measured synchronously at an urban site of Beijing city (BJ) and a rural site of Dongbaituo (DBT) in Hebei province from 1 July to 15 August 2016. The average concentration of the total NMHCs (TNMHCs) at DBT site were about a factor of 1.3 higher than that at BJ site. Ethane, ethylene, propane, acetylene, butane, isobutane, toluene and isopentane were the common species in the top ten NMHCs at the two sampling sites, and the contributions of the top ten NMHCs to TNMHCs at BJ and DBT sites were 65.6% and 75.1%, respectively. The diurnal variations of TNMHCs at BJ site exhibited one peak during the morning rush hours, whereas two peaks occurred at DBT site during the period from 3:00 to 8:00 (UTC/GMTC8). Based on the correlation coefficients of typical NMHCs pairs and the positive matrix factorization (PMF) results, the gasoline exhaust was found to be the dominant source (38.8%) for atmospheric NMHCs in Beijing, while coal combustion made the largest contribution (32.3%) at the rural site. Atmospheric ozone production over the BJ site was found to be NMHCs-sensitive, while it was in the transition regime at DBT site. Additionally, the largest contributions of atmospheric NMHCs groups to the ozone formation potential at BJ and DBT sites were alkenes and aromatics, with the proportions of 35.8% and 38.6%, respectively.