RESEARCH ARTICLE Sources of submicron aerosol during fog-dominated wintertime at Kanpur Tarun Gupta & Anil Mandariya Received: 8 October 2012 / Accepted: 13 February 2013 / Published online: 27 February 2013 # Springer-Verlag Berlin Heidelberg 2013 Abstract The main objective of this atmospheric study was to determine the major sources of PM 1 (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 gravi- metric and quantitative chemical analyses for determining water-soluble ions (NH 4 + ,F - , Cl - , NO 3 - , and SO 4 2- ) using an ion chromatograph and trace elements using an induc- tively coupled plasma–optical emission spectrometer. The mean PM 1 mass concentrations were recorded as 114± 71 μg/m 3 (day) and 143±86 μg/m 3 (night), respectively. A significantly higher diurnal contribution of ions (NH 4 + ,F - , Cl - , NO 3 - , and SO 4 2- ) in PM 1 mass was observed during the fog-affected days and nights throughout the winter sea- son, for which the average values were recorded as 38.09± 13.39 % (day) and 34.98±12.59 % (night), respectively, of the total PM 1 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. Keywords Submicron particles . Fog . Elemental composition . Source-receptor modeling . UNMIX Introduction In the past decade, PM 1 (particulate matter ≤1 μm in aero- dynamic diameter) has emerged as a major concern and has been correlated directly with the decrement in human health as well as with the poor visibility in the urban air sheds. PM 1 may consist of the primary particulate matter, emitted di- rectly into the atmosphere from sources such as road traffic, resuspension of road dust, construction and agricultural activities, power plants, industrial processes, biomass burning, etc., as well as secondary pollutants formed through the pho- tochemical transformations of gas phase species (Hildemann et al. 1991; Schauer et al. 1996; Kleeman and Cass 1998; Chakraborty and Gupta 2010). The two major secondary components of the atmospheric inorganic aerosol are particu- late sulfate and nitrate. They are formed via two main path- ways: photochemical oxidation of SO 2 and NO x precursors in the gas phase to highly soluble acids followed by uptake into preexisting aerosol or cloud droplets and oxidation in the aqueous phase, followed by evaporation of cloud droplets (Raes et al. 2000). In fact, PM 1 is a better marker for the anthropogenic sources consisting of mainly water-soluble ions (Na + , NH 4 + , Ca 2+ , Cl - , SO 4 2- , and NO 3 - ), elements, organic carbon, and elemental carbon (Lin and Lee 2004; Lee and Hopke 2006; Shen et al. 2009). Trace elements associated with fine particles are nonvolatile in nature and are less likely to get chemically transformed, thus remaining in their original form even after undergoing long-range atmospheric transport. Hence, the use of elemental signatures to appor- tion aerosol into major regional sources requires an under- standing of the behavior of aerosol-bearing trace elements during different seasons. This is coupled to the fact that industrial outputs are not generally seasonally dependent, whereas airborne concentrations of crustal material are af- fected by seasons. There are very limited data currently available on the concentration and availability of PM 1 in Responsible editor: Gerhard Lammel Electronic supplementary material The online version of this article (doi:10.1007/s11356-013-1580-6) contains supplementary material, which is available to authorized users. T. Gupta (*) : A. Mandariya Department of Civil Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India e-mail: tarun@iitk.ac.in Environ Sci Pollut Res (2013) 20:5615–5629 DOI 10.1007/s11356-013-1580-6