Seasonal patterns in rice and wheat residue burning and surface PM2.5 concentration in northern India

Abstract

Rice-Wheat production system of the Indo-Gangetic Plain (IGP) in northern India generates large amounts of crop residues annually, substantial amount of which is burned in-situ. Due to this, people in this region and nearby cities are exposed to extremely high concentrations of atmospheric pollutants, especially in late autumn to winter. Multiple factors affect air quality, the main ones being pollutant emissions and meteorology. We generated a high-resolution (0.05° × 0.05°) multi-year (2012–2020) fine particular matter (PM 2.5 ) dataset of pollutant emissions from wheat and rice residue burning for the IGP by combining production data and satellite active fires from the Visible Infrared Imaging Radiometer Suite (VIIRS) 375-m product. We used surface PM 2.5 concentrations and meteorological data from Modern-Era Retrospective Analysis for Research and Applications version 2 (MERRA-2) atmospheric reanalysis to characterize the seasonal PM 2.5 concentrations and their relationships with anomalies in meteorological conditions. Results showed a much higher number of fires during from rice, with an interannual average of 79,385 total fires versus 33,096 from wheat. Emissions are higher during the rice harvest period: 406 Gg/year versus 245 Gg/year, respectively for rice and wheat. Emissions and PM 2.5 concentrations from rice harvest are higher than those of wheat as a consequence of a higher number of fire spots, emissions, and atmospheric conditions that prevent their dispersion. PM 2.5 concentrations are in addition strongly related to the amount of biomass burned and the number of fires and their intensity. In terms of meteorological anomalies, the planetary boundary layer height, wind speed and the surface thermal inversion strength have a stronger association with PM 2.5 concentration during the rice residue burning period. Conversely, PM 2.5 concentration and emissions anomalies during the wheat harvest shows a stronger correlation with factors associated with the amount of residues burned in the field. • Fire spots and PM 2.5 emissions from both rice and wheat residue burning concentrate over the west area of north India. • Maximum PM 2.5 emissions from rice (post-monsoon) residue burning are about twice those from wheat (pre-monsoon). • Post-monsoon PM 2.5 concentrations from rice residue burning are about three times higher than from wheat residue burning (pre-monsoon). • PM 2.5 shows a greater association with inversion strength and relative humidity during the rice harvest period.