Characterization of Free-Fall Dust Aerosols at Two Different Heights in Delhi: Understanding the Influence of Carbon Fraction

Abstract

The free-fall dust in ambient atmosphere provides important information about the nature and sources of pollutants in urban settings, because it incorporates the particles settling under gravity influence irrespective of their size. In the present work, free-fall dust samples were collected at a 1.5- and 9 m (5- and 30-ft) height at different locations to understand the impact of immediate and ultimate pollution sources, respectively, in Delhi. Samples collected near traffic intersections exhibited vehicular emissions; resuspended road side dust; and carbon and trace metals, such as Zn, Cu, Pb, Ni, Cr, and Cd. Interestingly, the total carbon fraction contributed more than 10% of the total collected mass at all sites. Zn and Ba concentrations dominated over other trace metals in samples at both heights and for all the sites. The authors’ results suggest that the presence of carbon in higher quantities has caused a dilution effect on trace metal concentrations. The study confirmed that crustally derived materials dominated the total mass of free-fall dust at both heights. Also, a statistical analysis (ANOVA) was also performed to find out the differences in samples from the two heights. The ionic composition (