Ranking of BTEX with Respect to Ozone Formation by Development of Ozone Reactivity Scale

The high concentration of ground-level ozoneis a serious problem in many areas. Ozoneformation is non-linear process and is produced from the photochemical interactions of volatile organic compounds (VOCs) and oxides of nitrogen (NOx) in the troposphere. Generally, MIR (Maximum Incremental Reactivity) scale is one of the popular ones in the assessment of ozoneformation potential of various VOC compounds. In this study, we have taken this scale into consideration for analysing the ranking of benzene, toluene, ethylbenzeneand xylene( BTEX) at selected sites which are divided on the basis of near to traffic intersection and less vegetation (Site I) and away from traffic intersection with dense vegetation (Site II) during winter season (Nov’10–Feb’11). The results showed that the average concentration of ozonewas found to be higher at Site I than Site II. As per MIR scale, irrespective of site and month, xylenes(m-/ p-xyleneplus o-xylene) are the most dominant contributor to ozoneformation amongst BTEX. Toluene is the second largest contributor to ozoneformation. Amongst all, ozoneformation potential of benzene is least but it is the most hazardous and carcinogenic species amongst BTEX. Thus, this scale is very useful for examining the relative importance of VOC compounds for their role in photochemical smog formation including production of ozone.