Pollution profiles of volatile organic compounds from different urban functional areas in Guangzhou China based on GC/MS and PTR-TOF-MS: Atmospheric environmental implications

Ozone is currently the main atmospheric pollutant in the Pearl River Delta region, China. The atmospheric volatile organic compounds (VOCs) are key participators in the formation of ozone. Thus, the pollution profiles of ambient VOCs in Guangzhou city were measured using both offline (gas chromatography-mass spectrometry (GC/MS)) and online (proton transfer reaction time-of-flight mass spectrometer (PTR-TOF-MS)) methods. Three different functional areas were selected as vehicle detection station (VSD), roadside of city expressway (RCE), and Higher Education Mega Center (HEMC). GC/MS measurement results demonstrated that the total concentration of VOCs (TVOCs) with mean values of 55.0, 44.9 and 24.5 ppb at VSD, RCE and HEMC sites, respectively. At VSD site, the dominant group is aromatic hydrocarbons (accounting for 41.4% of TVOCs), in which toluene accounts for the largest proportion (17.6%). In contrast, aliphatic hydrocarbons were the dominant group at RCE (50.2% of TVOCs) and HEMC (47.4% of TVOCs), in which n-hexane was the major compound (18.4% and 21.6% at RCE and HEMC sites, respectively). Comparatively, the mean TVOC levels analyzed with PTR-TOF-MS were much higher at all studied sites, because large quantity of oxygenated VOCs (OVOCs accounting for 72.0%, 76.3% and 73.5% of TVOCs at VSD, RCE and HEMC sites, respectively) could be detected, but not by GC/MS. Among OVOCs, methanol was found as the most abundant component at all three studied sites. The assessment of atmospheric photochemical activity showed that the average contributions to ozone formation potential (OFP) from VOCs were 8.5 x 10(2), 7.3 x 10(2) and 8.2 x 10(2) mu g m(-3) at VSD, RCE and HEMC sites, respectively, and OVOCs were the dominant contributors for OFP. The result can provide the references for local government to eliminate VOCs and attenuate ozone pollution.