Distribution of vehicular pollutants in street canyons of Varanasi, India: a different case Santosh K. Prajapati & B. D. Tripathi & Vinita Pathak Received: 22 September 2007 / Accepted: 20 December 2007 / Published online: 11 March 2008 # Springer Science + Business Media B.V. 2008 Abstract In present study horizontal and vertical distribution of traffic-related pollutants (CO and SO 2 ) within the street canyons in (CO and SO 2 ) Varanasi, India was monitored. The results showed that average horizontal profiles of traffic-related pollutant concentrations within street canyon at leeward side were approximately same as that of windward side. However, the vertical concentration of both the pollutants decreases with height above the ground and study indicated that CO and SO 2 concen- trations at different heights below the roof showed clear vertical self-gradient. CO and SO 2 concentration decreased with height and the minimum value occurred at the roof. It was concluded from the observed results that pollutants from vehicular ex- haust emissions in the street canyon of Varanasi were evenly distributed. This result may be due to the fact that wind vortices are not formed. Therefore, urban planners can use this type of streets so that there is proper ventilation and dispersal of pollutants. Keywords Street canyons . Leeward . Windward . Vehicular emissions Introduction Vehicular emission is becoming a major source of air pollution in the urban environment having densely packed buildings adjoining narrow streets and uncon- trolled increase in motor vehicles. Population and traffic density are relatively high in urban streets and human exposure to harmful pollutants is expected to significantly increase (Selberg 1996). Knowledge of pollutants dispersal in urban streets can help urban planners to take into account urban geometry with best possible natural ventilation. Dispersion character- istics in urban streets canyons have been investigated by (Hoydysh and Dabberdt 1988; Xia et al. 2001). Parameters that dominates the pollutant dispersion process in street canyon such as street layout effects, including building geometry and structural design as well as street canyon dimensions have been exten- sively studied mainly with wind-tunnel experiments (Baker and Hargreaves 2001; Kastner-Klein and Plate 1999; Kastner-Klein and Fedorovich 2001) and numerical models (Nicholson 1975; Chan and Dong 2002; Wang and Huang 2002; Huang et al. 2000; Baik and Kim 2002; Xie and Huang 2005) and few with full-scale experiments (Berkowicz 1996; Croxford 1998). Oke (1998) and Sini et al. (1996) studied the thermal effects on pollutant dispersion in street canopy. Lots of studies have been conducted through field monitoring, wind tunnel and mathe- matical model simulation. Georgii et al. (1967) showed in their experiment that the CO concentration Environ Monit Assess (2009) 148:167–172 DOI 10.1007/s10661-007-0148-7 S. K. Prajapati : B. D. Tripathi (*) : V. Pathak Botany, Banaras Hindu University, Pollution Ecology Research Laboratory, Varanasi 221005, India e-mail: sntshprjpt@rediffmail.com