Source apportionment and potential source regions of size-resolved particulate matter at a heavily polluted industrial city in the Indo-Gangetic Plain

This study presents results from size-resolved particulate matter (PM) source apportionment in Ghaziabad, an industrial city adjoining New Delhi in the Indo Gangetic Plain (IGP). A full-year of measurement of PM2.5 and PM10 along with their chemical constituents was performed at two locations in the city. The annual average PM2.5 and PM10 concentrations were similar to 150 +/- 85 mu gm(-3) and similar to 270 +/- 140 mu gm(-3), respectively, with a ratio of 0.55, indicating the considerable influence of dust. USEPA PMF5 was applied to a combination of ions, elements, and carbon fractions of both PM2.5 and PM10. The model resolved eight factors, including combustion aerosol, secondary aerosol, vehicular emissions, resuspended dust I, resuspended dust II, brick manufacturing, copper smelter, and mixed metal processing. These factors were common to both sites and PM fractions, but with different contributions. Annually, the major contributors to PM2.5 were vehicular emissions (similar to 21-23%), secondary aerosol (20%), and combustion aerosol (similar to 17-19%) and to PM10, they were dust (similar to 44-54%) and combustion aerosol (similar to 23%). When daily average PM2.5dailyavg>90 mu gm(-3), brick processing, vehicular emissions, and secondary aerosols were found to be contributing to similar to 60% of the PM2.5 loading. However, when PM10dailyavg>250 mu gm(-3), combustion aerosol, and resuspended dust (I and II) were found to be contributing to similar to 70% of the PM10 loading. The likely PM source locations were local as well as regional, with the brick kilns and biomass combustion in the region and states in the upper IGP, namely Punjab, Haryana, and Delhi, being important source regions. Also, specifically for PM10, local construction activity and long-range transport of aged dust from the Arabian desert through western India were found to be the source regions. The results of this study suggested that lowering the contribution of combustion sources, including vehicles, industry, and brick kilns can significantly lower the PM2.5 loading by lowering primary particle loading and secondary particle generation. Controlling local dust resuspension can lower PM10 mass loading, enhancing local air quality.