Abstract
This study assesses temporal variability and source contributions of PM1 (particles with aerodynamic diameter ≤ 1.0 µm) samples (n=51; November 2009–February 2010) from an urban location at Kanpur (26.30°N; 80.13°E; 142 m above mean sea-level) in the Indo-Gangetic Plain (IGP). A study period from November to February is preferred owing to massive loading of particulate matter in entire IGP. PM1 varies from 18 to 348 (Avg±SD: 113±72) µg m−3 in this study. A total of 11 trace metals, five major elements and four water-soluble inorganic species (WSIS) have been measured. Mass fraction of total metals (∑metals=trace+major) centres at 18±14 %, of which nearly 15 % is contributed by major elements. Furthermore, ∑WSIS contributes about 26 % to PM1 mass concentration. Abundance pattern among assessed WSIS in this study follows the order: ≈> > Cl−. The K-to-PM1 mass fraction (Avg: 2 %) in conjunction with air-mass back trajectories (AMBT) indicates that the prevailing north-westerly winds transport biomass burning derived pollutants from upwind IGP. A recent version of positive matrix factorisation (PMF 5.0) has been utilised to quantify the contribution of fine-mode aerosols from various sources. The contribution from each source is highly variable and shows a strong dependence on AMBT. Events with predominant contribution from biomass burning emission (>70 %) indicate origin of air-masses from source region upwind in IGP. One of the most interesting features of our study relates to the observation that secondary aerosols (contributing as high as ~60 % to PM1 loading) are predominantly derived from stationary combustion sources (/ ratio: 0.30±0.23). Thus, our study highlights a high concentration of PM1 loading and atmospheric fog prevalent during wintertime can have a severe impact on atmospheric chemistry in the air-shed of IGP.
Highlights
Indo-Gangetic Plain (IGP) is considered as the most populated and highly polluted regions in India
Source apportionment of PM1 using positive matrix factorisation (PMF) has been assessed for various sources contributing to fine-mode aerosols at the Kanpur region
For the determination of water-soluble inorganic species (WSIS) (NH4', NO3(, SO42 ( and Cl(), aerosol sample was extracted with Milli-Q water using a standardised sonication technique (10 mL )3; 5 min each) and the particles were allowed for gravity settling
Summary
Indo-Gangetic Plain (IGP) is considered as the most populated and highly polluted regions in India. Previous studies have made attempts to highlight the source regions of large-scale biomass burning emissions in upwind IGP. Temporal variability and emission budget from upwind IGP further suggests that biomass (post-harvest agriculturalwaste and bio-fuels) burning emission is a predominant source of fine-mode aerosols on an annual and seasonal basis (Rajput et al, 2014a, 2014b; Rastogi et al, 2014; Singh et al, 2014). Biomass burning emissions and fossil-fuel combustion are all-year active sources of fine-mode aerosols in IGP. Based on recent unequivocal evidences, it can be summarised that IGP outflow under NW-wind system shows characteristics with predominance of biomass burning emissions (Srinivas et al, 2011; Rajput et al, 2013). Source apportionment of PM1 using positive matrix factorisation (PMF) (version 5.0) has been assessed for various sources contributing to fine-mode aerosols at the Kanpur region
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