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

Abstract

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 ∼150±85 μgm−3 and ∼270±140 μgm−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 (∼21–23%), secondary aerosol (20%), and combustion aerosol (∼17–19%) and to PM10, they were dust (∼44–54%) and combustion aerosol (∼23%). When daily average PM2.5dailyavg>90 μgm−3, brick processing, vehicular emissions, and secondary aerosols were found to be contributing to ∼60% of the PM2.5 loading. However, when PM10dailyavg>250 μgm−3, combustion aerosol, and resuspended dust (I and II) were found to be contributing 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 re-suspension can lower PM10 mass loading, enhancing local air quality.