Estimation of SO4 contribution by dry deposition of SO2 onto the dust particles in India

Dustfall deposition fluxes of major water-soluble components Cl, NO3, SO4, NH4, Na, K, Ca and Mg were estimated at five different sites of Delhi. The pH of water extracts of samples has been observed minimum at NPL ranging from 5.8 to 7.1 and maximum at Iqbalpur ranging from 7.9 to 8.7. The high values of pH of dustfall deposition suggest the dominance of crustal components that add higher alkalinity due to presence of components like Ca, Mg, etc. Dustfall fluxes were observed highest for Ca. considering the importance of alkaline nature of dust particles; the fraction of SO4 contributed by dry deposition of SO2 on the dust particles was estimated. Using these estimates, further the ambient concentrations of SO2 were calculated which were in a very good positive agreement with experimental concentration of SO2.