Elemental characterization and source identification of PM2.5 using multivariate analysis at the suburban site of North-East India

Aerosol samples for PM2.5 were collected at a suburban site of India during Jan 2007 to Jan 2008. The sampling site is exposed to different antropic source emissions like vehicular emission, wood burning, coal based industries and other industrial activities. The mass concentrations of PM2.5, major elements (Al, Si, P, S, Na, K, Ca, Ti, V, Cr, Mn, Fe, Te, Co, Ni, Cu, Zn, Cd, Sn, Sb, and Pb) and major ions (Cl−, NO3−, SO42−, and NH4+) were determined for winter and rainy seasons. Their levels were found higher than those of in various European and American cities, however, comparable to those of some Asian cities. Analysis of variance (ANOVA) showed significant seasonal variation for concentrations of PM2.5, NO3−, SO42− and most of the elements. This seasonal variation is due to enhanced heating activities and stagnant climatic conditions in winter and removal of pollutants by wet deposition in the rainy period. Source apportionment was undertaken using enrichment factor (EF), Spearman's correlation and absolute principal component analysis. A five-factor model for explaining the observed PM2.5 levels was found to provide realistic results. Evaluation of element abundance at site indicates different pollution levels. The source identification of this study shows that PM2.5 levels were influenced by not only local and industrial activities but also long range transport. Traffic induced crustal sources (38%); coal combustion (26%), industrial and vehicular emissions (19%), wood burning (9%) and secondary aerosol formation (8%) are the major contributors to PM2.5 levels in the city.