Abstract
ABSTRACT Water-soluble inorganic ions (WSII), organic carbon (OC) and elemental carbon (EC), and metals in the residue of the water-soluble fraction were studied in fine (PM2.5) and coarse (PM2.5-10) particles during winter over two urban cities, Amritsar (AMS) and New Delhi (DEL), in northern India. The PM2.5/PM2.5-10 mass ratios at DEL and AMS were 3.6 and 2.79, respectively. ∑WSIIs was nearly 25% of the total mass in two size fractions and was higher in PM2.5 than PM2.5-10 at both sites. The secondary ions SO42− and NH4+ were dominant at both sites. The adsorption of fine particles onto larger ones may be a possible source of soluble ions in PM2.5-10. SO42− and NO3− were neutralized by NH4+, and the formation of (NH4)2SO4 dominated over NH4NO3 in PM2.5, and by Ca2+ in PM2.5-10 over DEL. Coal burning, and agricultural and livestock emissions were potential sources of precursor gases of SO42− and NH4+. Plastic burning and the brick kiln industry contributed Cl− in the PM2.5. OC dominated over EC above both sites, and the total carbon (OC + EC) was higher over AMS than DEL. Emissions from low-temperature rather than high temperature combustion processes were dominant, as indicated by the higher quantity of char-EC than soot-EC. OC, EC, and K+ resulted from biomass burning over AMS, whereas they originated in multiple sources over DEL. The Al normalized ratios of elements in the samples compared to the crust were higher in PM2.5 than PM2.5-10. Fe, Ti, and Mn ratios of 0.5 indicated the spatial heterogeneity in the particle chemistry between the two sites. To improve the air quality and safeguard human health, biomass burning and the re-suspension of dust must be restricted.
Highlights
The PM2.5 aerosols in ambient atmosphere are catching scientific attention due to their role in climate change, human health and atmospheric chemistry studies (Singh and Kaskaoutis, 2014; Pant et al, 2015; Ram and Sarin, 2015)
They further suggested that the warming effect of BC is more when it is internally mixed with sulfate aerosols and the climate change mitigation policies should focus on reducing BC/sulfate ratio
Air quality was very poor throughout the winter season at both locations
Summary
The PM2.5 aerosols in ambient atmosphere are catching scientific attention due to their role in climate change, human health and atmospheric chemistry studies (Singh and Kaskaoutis, 2014; Pant et al, 2015; Ram and Sarin, 2015). Poor air quality and health problems in this region are largely on account of PM2.5 in the ambient atmosphere. Ramana et al (2010) have reported a good correlation between BC to sulfate ratio and the net warming over three cities in China. They further suggested that the warming effect of BC is more when it is internally mixed with sulfate aerosols and the climate change mitigation policies should focus on reducing BC/sulfate ratio. The studies on WSII, carbon content and metal distribution in fine and coarse particles become important in understanding the sources of pollution, chemical transformations, radiative forcing and health effects
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