Variation of carbon monoxide at a suburban site in the Indo-Gangetic Plain: Influence of long-range transport from crop residue burning region

In the present study the diurnal, seasonal variability along with the comparison of ground-based and satellite retrieved carbon monoxide (CO) observations are reported at Agra. In addition, the impact of long-range transport of emissions from crop residue burning region (Punjab and Haryana) on CO concentrations at a downwind site was determined. Previous studies reported so far in India have mainly focused on the impact of crop residue burning activities on CO concentrations in the nearby regions while the present study is an attempt to identify the impact of these activities on a downwind site situated several kilometers away. The average concentration of in-situ measured CO at Agra was 518.7 +/- 487.9 ppb during 2015-2019. A good correlation between ground-based and satellite CO observations was found (y = 0.1 x + 129.4, R = 0.8). The highest seasonal average CO concentrations were observed during Oct-Nov, which corresponds with paddy residue burning in the north-west IGP (NW-IGP). These activities result in the emission of CO which can be transported to distant places due to its long lifetime (2 months) and can influence the air quality. It was observed that during the crop residue burning period the average concentrations of CO were higher by 19.8, 78.7 and 65.1 %, respectively in 2015, 2017 and 2019. Backward air mass trajectories and potential source contribution function (PSCF) suggested crop residue burning activities can be the potential source of CO at the study site during the crop residue burning period.