In this work, we propose to investigate the effect of dry deposition on mass concentrations of fine particulate matter in Pune(18.5203° N, 73.8567° E), Mumbai (19.0760° N, 72.8777° E) and Delhi (28.7041° N, 77.1025° E) during November 2016 and compare the results for these western and northern Indian megacities. We shall also investigate the dry deposition flux of particulate matter with respect to particle sizes of coarse, fine and ultrafine particles in Delhi (November 2017) as a case study. It is observed that coarse particles had a greater deposition velocity of ~0.0036m/s when compared to fine particles, which had deposition velocity of ~0.0002m/s and ultrafine particles with deposition velocity of ~3.569 x 10-5m/s. In still air, gravitational forces on large particles govern the air quality by virtue of their significant dry depositions. These deposition velocities are used to estimate deposition fluxes and airborne mass after elapse of time at breathing height. On an average, it was found that around 88.47% mass concentration of coarse particles settled during a time span of 1 hour due to dry deposition, whereas, only 11.31% mass concentration of fine particles had settled during the same period of time. It was hence observed that the deposition velocity of particles was directly proportional to the square of particle diameter and settled mass concentration directly depended on the settling velocity of depositing species.
Keywords: deposition velocity; anthropogenic contaminants; particulate matter; mass concentrations;