Particulate pollutants and their water soluble ionic components were collected and analyzed on the occasion of high pollution episode days in the period 2009 to 2011. Among the water soluble ionic constituents at Mohal (valley base), SO42- (34%) was the largest contributor; followed by Cl- (20%), NO3- (17%), Ca2+ (9%), Na+ (7%), NH4+ (5%), F- (2%), Zn2+ (2%) and Mg2+ (1%). While at Kothi (hill slope), Cl- (27%) was the largest contributor; followed by SO42- (25%), NO3- (14%), Na+ (11%), Ca2+ (9%), NH4+ (7%), K+ (3%), F-(3%) and Zn2+ (1%). The average ratios of NO3- + Cl-/SO42- were 1.08 and 1.64 for Mohal and Kothi, respectively; indicating that a small fraction of HNO3 and HCl influenced the acidic nature of ions. The mass ratios of NH4+/NO3- and NH4+/SO42- were 0.29, 0.5 and 0.15, 0.28; at Mohal and Kothi, respectively. The ratios were below unity showing the predominance of NH4NO3 and (NH4)(2)SO4 in the atmosphere. The descending order of neutralizing factors were observed as Ca2+ > NH4+ > K+ > Mg2+ assuming that the origin is of a crustal source. The non-sea salt fraction for Mohal was found in the descending order of Cl-, Ca2+ and SO42- , which are more than 50% of the total ions except Mg2+ and K+. While for Kothi, the percentage of Cl- and SO42- stood to be more than 50% indicating that these ions are of non-marine origin. The first factor from principal component analysis for Mohal explains 75.59% of the total variance i.e., highly loaded with NH4+ (0.986), K+ (0.685), F- (0.935), Cl- (0.919) and Zn2+ (0.969) indicating influence of anthropogenic activities on PM10 concentration. While at Kothi, the first factor explains 45.41% of the total variance, highly loaded with K+ (0.981), SO42- (0.965), NO3- (0.953) and Zn2+ (0.948) also indicating influence of anthropogenic activities in the region.
