The Effects of Fuel Evaporation and Biomass Burning on Toluene Concentrations in an Urban Area

Abstract

Using an automated gas chromatography system coupled with an online sampling/thermal desorption module, benzene, toluene, and their alkylated derivatives were measured in Las Vegas, Nevada from 3 July to 28 August 2008. The levels of hydrocarbons were comparable to those typically found in urban environments. Statistically significant (at 95 % level) higher concentrations were measured on mid-week days as compared with those measured during weekends. This was correlated to a local traffic pattern rather than traffic on highways. The concentrations of aromatic hydrocarbons also increased during periods when transport of smoke from wildfires in central and north California was identified by remote sensing but these levels were comparable to other days with volatile organic compounds concentrations. The high toluene/benzene ratios and the estimated photochemical age of air masses implied the contribution of other local sources. Fuel evaporation accounted for the vast majority of toluene enhanced concentrations in early July (as compared with those measured in June) for sites within the urban grid, but very little for sites located outside the urban area.