Chemical composition of fine mode particulate matter (PM2.5) in an urban area of Delhi, India and its source apportionment

In this paper, the chemical constitutes of PM2.5 mass [organic carbon (OC), elemental carbon (EC), water soluble inorganic ionic components (WSIC), and trace elements] was estimated for its chemical characteristics and source apportionment study at Delhi, India during January 2013 to May 2014. In the present case, the average mass concentration of PM2.5 was recorded as 125.5 ± 77.2 μg m− 3 (range: 31.1-429.5 μg m− 3). The average concentration of major and trace elements (Na, Mg, Al, P, S, Cl, K, Ca, Cr, Ti, AS, Br, Pb, Fe, Zn and Mn) was accounted for ~ 22% of PM2.5 mass. Strong seasonal variation was observed in PM2.5 mass concentration and its chemical composition with maxima during winter and minima during monsoon seasons. The chemical composition of the PM2.5 was reconstructed using IMPROVE equation from the analyzed elemental composition of PM2.5 mass. In reconstructed PM2.5 mass, the highest contribution accounted from particulate organic matter (27.5%) to other components e.g., soil/crustal matter (16.1%), ammonium sulphate (16.1%), ammonium nitrate (13.1%), sea salt (17.1%) and light absorbing carbon (10.2%). In the present study, Positive Matrix Factorization (PMF) was used for identifying the PM2.5 sources at the observational site of Delhi. The major source of PM2.5 was identified as secondary aerosols (23.2%), soil dust (22.5%), vehicle emissions (18.5%), fossil fuel burning (13.1%), biomass burning (12.3%), industrial emissions (6.3%) and sea salts (4.1%) at Delhi.