Evaluation of seasonal variations in abundance of BTXE hydrocarbons and their ozone forming potential in ambient urban atmosphere of Dehradun (India)

In Dehradun, ambient volatile organic compounds (VOC) samples were collected for three seasons viz. summer, winter and monsoon (during period 2012-2013) to investigate seasonal variations at five different sampling sites. The samples were quantified for aromatic VOCs by gas chromatography (GC-FID) to monitor benzene, toluene, m, p-xylene, o-xylene and ethylbenzene. BTXE comprise an important group of VOCs mostly prevalent in a typical urban environment. They were monitored because they are known to cause impacts on climate, health and on vegetation. Toluene was found to be the most abundant VOC among the measured ones in the atmosphere of Dehradun. The maximum mean concentration of VOCs was observed in winters and lowest during summers for BE species. Toluene ambient concentration was rather found to register highest during winters and lowest in monsoons. Kruskal-Wallis test showed statistically significant differences seasonally (p < 0.05). High toluene to benzene T/B (> 1) observed ratio indicates vehicular emission as their major source. BTEX were also evaluated for their ozone-forming potential (OFP). Toluene and xylenes were found as the highest contributing hydrocarbons towards ozone forming potential among BTXE.