Influence

Water-soluble ionic constituents (Cl–, NO3–, SO42–, Na+, NH4+, K+, Mg2+ and Ca2+) of PM2.5 were measured using Ambient Ion Monitor coupled-to Ion Chromatograph (AIM-IC) with a time resolution of one hour at Ahmedabad (an urban location in semi-arid region of western India) during summer and winter to study the diurnal and seasonal variations. Maximum abundances of most of the species were observed during after-noon hours in summer, whereas minimum concentrations were found during winter at the same local time. During summer, the concentration levels of most of the constituents in a diurnal cycle are largely influenced by ambient relative humidity variation. During winter, the emission strength and boundary layer dynamics impact the diurnal cycle. Secondary inorganic species like NH4+, NO3 – and SO42– exhibit significant differences in their relative abundances during winter and summer. Four factors have been derived by Positive Matrix Factorization (PMF) analysis on water-soluble ionic constituents. These are secondary, sea-salt, mineral dust sources and the fourth factor is associated with K+, which is likely to be biomass burning emission