Abstract
Concentrations of non-methane hydrocarbons (NMHCs) were measured to investigate their temporal variations and major sources, and to explore the ozone formation potentials (OFP) of each NMHCs for the first time in December 2008 in Foshan. Ethane, propane, n-butane, i-pentane, 2,3-dimethylbutane, ethene, propene, ethyne, benzene and toluene were the 10 most abundant hydrocarbons, accounting for 82% of the concentration of total NMHCs. Concentrations of these hydrocarbons as well as their fractional contributions to the total NMHCs were higher in the morning and evening than in the afternoon, consistent with the variations in vehicle volumes during these periods. This suggests that the vehicular emission was likely the major source of NMHCs at this site. The mean B/T ratio (0.45 ± 0.24) further supported vehicular emission as the main source of the ambient NMHCs except for aromatic hydrocarbons. These aromatic hydrocarbons were mainly from solvent evaporation, as indicated by the diurnal variations in the ratios of toluene and m/p-xylene to benzene. The results from factor analysis also showed that combustion process and solvent usage were the major sources of NMHCs. On average, total Prop-Equiv and OFP were 153.0 ppbc and 863.4 μg/m 3 , respectively. Based on MIR (maximum incremental reactivity) scale, the leading contributors to OFP in decreasing concentrations were ethene, toluene, propene, i-pentane, m/p-xylene, 1-butene, ethylbenzene, o-xylene, 2,3-dimethylbutane and trans-2-butene, which in total explained 77% of the total OFP. Ranking by Prop-Equiv, the top 10 species were propene, toluene, ethene, 1-butene, i-pentane, m/pxylene, isoprene, 2,3-dimethylbutane, trans-2-butene and ethylbenzene, accounting for 66% of the total Prop-Equiv. Thus, alkenes played the most important role in O3 formation, followed by aromatics and alkanes during the study periods in Foshan.
Highlights
Foshan is one of the most populated areas in Pearl River Delta (PRD) in south China
Accompanying with the substantial economic development, large amounts of air pollutants were emitted into the atmosphere, which leads to a rapid deterioration of air quality in and around the area
The concentrations of the most abundant hydrocarbons were much higher in Foshan than those in other regions
Summary
Foshan is one of the most populated areas in Pearl River Delta (PRD) in south China. It is one of the largest manufacturing bases in the world. Air pollutants including ozone (O3), sulfur dioxide (SO2) and nitric oxides (NOx) in Foshan frequently exceeded the National Ambient Air Quality Standard (NAAQS). Among these pollutants, O3 is often the most concerned species due to its adverse effect on human health (Lai et al, 2009; Shao et al, 2009; Hwang et al, 2011). O3 is not emitted directly; instead, it is formed from photochemical reactions involving volatile organic compounds (VOCs) and NOx
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