Impact of particle size on distribution of major ions in acid- and water-soluble components of PM10 atmospheric aerosols in the coastal region of Mumbai

In this study, the concentration of acid and water-soluble ions (Na+, K+, Mg++, Ca++, F−, Cl−, NO3− and SO4− −) in different particle size range (> 1.1–<2.0 μm, > 2.0–<3.3 μm, > 3.3–<4.7 μm, > 4.7–<5.8 μm, > 5.8–<9.0 μm and > 9 μm–<10 μm) of PM10 atmospheric aerosols collected by six stages Anderson Cascade Impactor were determined using conductivity suppressed ion-chromatography system. Suspended particulate matters in the form of respirable (PM10) aerosols were collected on the roof of a three storied building at a height of 20 m above the ground, at Bhabha Atomic Research Centre (BARC), Mumbai using Hi-Volume Sampler (HVS) with Whatman glass fiber filter paper during the period of March–June 2009. The sequence of solubility of ions in both extractants (acid + water) of PM10 aerosols from greatest to least was found to be Na+ > Ca++ > K+ > Cl− > F− > Mg++ > NO3− ≈ SO4−−. The average concentration of Na+, K+, Mg++, Ca++, F−, Cl−, NO3− and SO4−− in PM10 aerosols was estimated to be 13.36 g/kg, 3.76 g/kg,0.251 g/kg,3.771 g/kg,0.833 g/kg,1.17 g/kg, 81 μg/kg and 290 μg/kg respectively. The enrichment of particular ion in soluble components may be due to its high abundance in PM10 aerosols, less sorptivity with the tiny solid particles of atmospheric dust, high extractability and leachability, high solubility and mobility. By classifying the PM10 aerosols into two categories viz fine particle (< 2.5 μm) and coarse particle (> 2.5 μm–<10 μm), it was found that generally, in the fine particle, the geometric mean concentration of total soluble ions in acid and water components was found to be higher than coarse particle. Overall, it was also observed that generally as particle size increases, the geometric mean concentration of soluble ions in both extractants of PM10 aerosols decreases.