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 μm) 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 μg/m³ (day) and 143?±?86 μg/m³ (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.