Sources of submicron aerosol during fog-dominated wintertime at Kanpur

The main objective of this atmospheric study was to determine the major sources of PM1 (particles having aerodynamic diameter < 1.0 mu m) within and near the city of Kanpur, in the Indo-Gangetic Plain. Day and night, 10 h long each, filter-based aerosol samples were collected for 4 months (November 2009 to February 2010) throughout the winter season. These samples were subjected to gravimetric and quantitative chemical analyses for determining water-soluble ions (NH4 (+), F-, Cl-, NO3 (-), and SO4 (2-)) using an ion chromatograph and trace elements using an inductively coupled plasma-optical emission spectrometer. The mean PM1 mass concentrations were recorded as 114 +/- 71 mu g/m(3) (day) and 143 +/- 86 mu g/m(3) (night), respectively. A significantly higher diurnal contribution of ions (NH4 (+), F-, Cl-, NO3 (-), and SO4 (2-)) in PM1 mass was observed during the fog-affected days and nights throughout the winter season, for which the average values were recorded as 38.09 +/- 13.39 % (day) and 34.98 +/- 12.59 % (night), respectively, of the total PM1 mass. This chemical dataset was then used in a source-receptor model, UNMIX, and the model results are described in detail. UNMIX provided a maximum number of five source factors, including crustal material, composite vehicle, secondary aerosol, coal combustion, and iron/steel production and metallurgical industries, as the dominant air pollution sources for this study.