P. Gursumeeran Satsangi

Chemical and morphological study of PM 10 and PM 2.5 in Pune, India

PM10 and PM2.5 ambient samples were collected by a particulate sampler (APM 550, Envirotech) in the Department of Chemistry, University of Pune, India. Exposed filters were used to determine the mass, ionic composition and morphology of fine PM. The mean PM10 and PM2.5 concentrations were 16.69 ± 5.6 µg m–3 and 11.68 ± 4.1 µg m–3, respectively. Neutralisation factors for all major cations were computed and found to be higher for Ca2+ while for PM2.5 it was higher for NH4+. Calculation revealed that in particulate matter 25% of SO42– in both PM10 and PM2.5 and 30% of NO3– in PM10 is coming from anthropogenic sources, whereas other species are coming mainly from the natural sources. Morphology and chemical composition of 236 individual particles were determined by scanning electron microscopy-energy dispersive spectrometer. Based on morphological study, the particles were clustered as: Si-rich particles (56%), soot (16%), oxides (10%), sulphates (8%), carbonates (5%), metal-rich (4%), and biological particles (3%).

Genotoxic effects of PM 10 and PM 2.5 bound metals: metal bioaccessibility, free radical generation, and role of iron

The present study was undertaken to examine the possible genotoxicity of ambient particulate matter (PM10 and PM2.5) in Pune city. In both size fractions of PM, Fe was found to be the dominant metal by concentration, contributing 22% and 30% to the total mass of metals in PM10 and PM2.5, respectively. The speciation of soluble Fe in PM10 and PM2.5 was investigated. The average fraction of Fe3+ and Fe2+ concentrations in PM2.5 was 80.6% and 19.3%, respectively, while in PM2.5 this fraction was 71.1% and 29.9%, respectively. The dominance of Fe(III) state in both PM fractions facilitates the generation of hydroxyl radicals (·OH), which can damage deoxyribose nucleic acid (DNA), as was evident from the gel electrophoresis study. The DNA damage by ·OH was supported through the in silico density functional theory (DFT) method. DFT results showed that C8 site of guanine (G)/adenine (A) and C6 site of thymine (T)/cytosine (C) would be energetically more favorable for the attack of hydroxyl radicals, when compared with the C4 and C5 sites. The non-standard Watson–Crick base pairing models of oxidative products of G, A, T and C yield lower-energy conformations than canonical dA:dT and dG:dC base pairing. This study may pave the way to understand the structural consequences of base-mediated oxidative lesions in DNA and its role in human diseases.