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Abstract
Aromatic hydrocarbons (AHs) are both hazardous air pollutants and important precursors to ozone and secondary organic aerosols. Here we investigated 14 C6–C9 AHs at one urban, one suburban and two rural sites in the Pearl River Delta region during November–December 2009. The ratios of individual aromatics to acetylene were compared among these contrasting sites to indicate their difference in source contributions from solvent use and vehicle emissions. Ratios of toluene to benzene (T/B) in urban (1.8) and suburban (1.6) were near that of vehicle emissions. Higher T/B of 2.5 at the rural site downwind the industry zones reflected substantial contribution of solvent use while T/B of 0.8 at the upwind rural site reflected the impact of biomass burning. Source apportionment by positive matrix factorization (PMF) revealed that solvent use, vehicle exhaust and biomass burning altogether accounted for 89–94% of observed AHs. Vehicle exhaust was the major source for benzene with a share of 43–70% and biomass burning in particular contributed 30% to benzene in the upwind rural site; toluene, C8-aromatics and C9-aromatics, however, were mainly from solvent use, with contribution percentages of 47–59%, 52–59% and 41–64%, respectively.
Highlights
Aromatic hydrocarbons (AHs) are emitted to the Earth’s troposphere mainly from anthropogenic sources including vehicle exhausts and solvent usage [1,2,3,4,5]
The urban site Guangzhou Environmental Monitoring Center (GEMC) showed significantly higher benzene levels (2642 ± 265, mean ± 95% C.I., pptv) than the suburban site Higher Education Mega Center (HEMC) or rural sites ZC and WQS (p < 0.01); the highest mean mixing ratios of toluene (5935 ± 2800 pptv) and C8-aromatics (3207 ± 422, pptv), were observed at WQS
The urban site GEMC showed significantly higher benzene levels than other suburban and rural sites (p < 0.01); the levels of toluene and C8-aromatics widely used as industry solvents were much higher at WQS, the rural site downwind the industry zones, than that at other sites (p < 0.05)
Summary
Aromatic hydrocarbons (AHs) are emitted to the Earth’s troposphere mainly from anthropogenic sources including vehicle exhausts and solvent usage [1,2,3,4,5]. They contribute an important fraction (∼20–30%, mass percent) of total nonmethane hydrocarbons (NMHCs) in the urban atmosphere [6]. Some AHs, like benzene, toluene, ethylbenzene and xylenes, are hazardous air pollutants; and for benzene, a known human carcinogen causing. In the PRD region, the rapid growth in economy has resulted in fast increase in anthropogenic emissions of air pollutants [21], and as an important class of anthropogenic volatile organic
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