Physico-Chemical Characteristics and Sources of Ambient Aerosol in India During 2001-2015: A Review

From the last few decades, the studies related to source apportionment of airborne particulate matter (PM) have gain more attention among global scientific community including India. The outcomes from these studies are utilized for better and effective policy design to control pollution level. However, these source apportionment results have been shown much divergence for India due to differences in sampling technique, analytical methods, selection of source maker chemical species, and application of mathematical and statistical methods, etc. So, this review presents the trends and advancement of ambient PM2.5 and PM10 particles source apportionment studies for special perspective of India for better understanding of these above highlighted issues. The ambient PM2.5 and PM10 source investigations related earlier research articles and reports from various regulatory agencies which published between the years of 2000 to 2015 for India were selected and categorized into three plateau regions for review. Few studies were carried out with source apportionment centered objectives for ambient PM2.5 and PM10 mass concentration and maximum reported studies were confined to address aerosol mass concentration and its chemical characterization to evaluate spatiotemporal variation. Higher number of data were reported for the Indo-Gangetic plain (IGP) region during the year of 2005 to 2007 with the annual average range from 56.2 to 136 μg m-3 and 134 to 306 μg m-3 for PM2.5 and PM10, respectively. The annual average for ambient PM2.5 and PM10 levels has been raised about 50 % and 14%, respectively during the first fifteen years of 21st century in Indian environment. The carbonaceous matter (TC) has been found as the major component of PM mass in Indian environment. The carbonaceous matter was reported as major abundant species which was about > 50 % of PM2.5 mass concentration with OC/EC ratio > 1. The distribution of different PM2.5 chemical components were reported to be 7 ± 15 %, 1 ± 3 %, 46 ± 49 %, 34 ± 24 % and 12 ± 9%, for crustal elements (Al, Ca, Fe, Na, Mg, Si), trace elements (Cr, Zn, Ni, Cu, Cd and Pb), ionic (Na+, NH4+, Cl−, NO3− and SO4 2−) and carbonaceous matter fractions, respectively. The following six major contributing sources for ambient PM2.5 pollution in India have been found during the assessment period i.e. road traffic emissions as the major contributor, followed by marine aerosols/sea salt, crustal, industrial emissions, secondary aerosols and biomass burning emissions.