Seasonal variation and sources of PM2.5 bound water-soluble ions at Jammu city in the foothills of the North-western Himalayas, India

Abstract

In this study, PM2.5 aerosols were collected from the campus of the University of Jammu situated along the Shivalik foothills of the North-western Himalayas in the Jammu urban area to understand the seasonal variability of PM2.5 mass concentrations and associated water-soluble inorganic ions (WSIIs). Results showed that the annual average PM2.5 mass concentrations were average 65.02 μg/m3 which significantly exceeded the annual National Ambient Air Quality Standards (40 μg/m3) by ~1.6 times. In addition, PM2.5 and WSIIs mass concentrations exhibited significant seasonal variability with the highest average concentrations observed during winter and the least during monsoon. Furthermore, WSIIs accounted for 24.56% of PM2.5 mass annually. Cl−, Na+, Ca2+ and Mg2+ depicted higher concentrations in summer whereas higher mass concentrations of SO42−, NO3− and NH4+ observed during winter pointed to their formation from gas to particulate conversion mechanisms. The variability of source strength during peak tourist seasons in holidays, festivities and new year appears to have significantly accounted for high PM2.5 in the study area. Additionally, meteorological conditions also appear to have played an important role in secondary aerosol formation which is noticeable from the high correlation observed among SO42−–NO3− (0.97), NH4+–SO42− (0.69), K+–Cl− (0.85), NH4+–NO3− (0.64), SO42−–K+ (0.63), NH4+–Cl− (0.65) at p