[Concentrations and ozone formation potentials of BTEX during 2008-2010 in urban Beijing, China]

Benzene, toluene, ethylbenzene and dimethylbenzene are typical anthropogenic emitted organics in the atmosphere, which not only endanger human health but also actively participate in photochemical reactions, generating O3 and secondary organic aerosols. In order to investigate the pollution level and its ozone formation potentials, concentrations of BTEX and O3 were parallel measured by the passive sampler and analyzed using GC-MS and ICS-90 during 2008-2010 in urban Beijing. The results show that toluene was the most abundant compound (8.7 +/- 3.1) microg x m(-3), followed by benzene, ethylbenzene and m/p-xylene, with concentrations of (7.1 +/- 3.3), (4.2 +/- 1.4) and (3.4 +/- 1.5) microg x m(-3), respectively. Concentrations of BTEX peaked in winter, followed by autumn, summer, and spring, with values of (26.8 +/- 12.1), (25.9 +/- 4.9), (24.7 +/- 2.8) and (16.8 +/- 1.4) microg x m(-3), respectively. Benzene concentrations were the highest in winter, while for toluene, the concentration was higher in summer than that in winter. Based on the maximum incremental reactivity scale, m/p-xylene was found to be the dominant contributor to ozone formation among BTEX. The ozone formation potentials of BTEX in Beijing were 65.2, 60.2, and 75.7 microg x m(-3) in 2008, 2009, and 2010, respectively, which were consistent with the measured values of 80.5, 65.0, and 101.9 microg x m(-3) during the corresponding period. Vehicular emission and solvent evaporation were the major sources of BTEX. Concentrations of benzene were affected by coal heating in winter, whereas BTEX concentration was more influenced by solvent evaporation in summer, which had an important contribution to the formation of O3 in urban Beijing.