Characteristics and diurnal variations of NMHCs at urban, suburban, and rural sites in the Pearl River Delta and a remote site in South China

Source attributions of hazardous aromatic hydrocarbons in urban, suburban and rural areas in the Pearl River Delta (PRD) region

“…These ratios consistent with the ratio observed in urban Guangzhou in 2005 (0.41, [5]), but lower than the ratio from boreal forest fire (0.80) [66]. Benzene, as a carcinogenic compound forbidden to be used in industry, were mainly from automobile exhausts in urban areas [5,24,64], so dominant contribution from vehicle exhausts in the urban site GEMC explained the higher benzene/acetylene ratio than at other sites [5,28]. As toluene, C 8 -aromatics and C 9 -aromatics were widely used as solvents in painting, coating, printing and cleaning processes in the highly industrialized PRD region [3,26,33,67], their high ratios to acetylene at WQS suggested substantial contribution of AHs from industrial emissions in the upwind city of Dongguan, a worldknown manufacturing center in the region.…”

“…The ratios of propane/acetylene, n-butane/acetylene and i-butane/acetylene at GEMC were 11.49 ± 3.79, 1.84 ± 0.28 and 2.61 ± 0.46, significantly higher (p < 0.01, two tails t-test) when compared to that of 1.24 ± 0.13, 0.60 ± 0.09 and 0.61 ± 0.10 at HEMC; 0.46 ± 0.06, 0.24 ± 0.06 and 0.23 ± 0.06 at ZC; and 0.82 ± 0.07, 0.55 ± 0.06 and 0.60 ± 0.07 at WQS, respectively, suggesting more significant influence of LPG-related sources in the urban areas, such as LPG-driven vehicles as well as home-use town gases for cooking. The ratios in urban GEMC were also higher when compared to that of 2.93, 1.05 and 0.56, respectively, observed at roadside in urban Guangzhou in 2005 [28]. This increase might be explained by the increased consumption of LPG for domestic cooking and LPGdriven vehicles.…”

“…Acetylene, for example, had been used extensively as a tracer for combustion [4,28,[60][61][62][63][64][65], and the ratios of hydrocarbons to acetylene were widely used to examine the impact of other emissions sources relative to combustion emissions. The ratios of propane, n-butane and i-butane to acetylene, for example, have been used to indicate their contribution from LPG leakage [28,60]. Ratios of AHs as well as propane, n-butane, and i-butane to acetylene at the four sites were showed in Fig.…”

“…This increase might be explained by the increased consumption of LPG for domestic cooking and LPGdriven vehicles. The number of LPG-driven buses and taxies in Since toluene is widely used as solvent and benzene's use is forbidden in industry, very high toluene to benzene ratios (T/B) were observed in typical industry emissions [28,68]; and T/B ratios in industrial cities [3,5] were comparatively higher than that in vehicle exhausts and roadside air samples [23,28,69,70] in which traffic-related emissions had dominant contributions. Biomass burning or coal burning showed much lower T/B ratios [66,71,72].…”

“…Studies showed that in the PRD region ozone formation was largely VOC-limited with AHs among the most important precursors [26][27][28][29], and AHs alone were responsible for over 75% secondary organic carbon in fine particles [20]. Therefore, emission control of AHs is vital to lower regional ozone pollution and SOA in the region.…”