Emission estimates of trace gases (VOCs and NOx) and their reactivity during biomass burning period (2003–2017) over Northeast India

Abstract

The study analysed spatio-temporal distribution of fire radiative power (FRP) and estimates of trace gases [volatile organic compounds (VOCs) and nitrogen oxides (NOx)] along with their reactivity during biomass burning period of March (2003–2017) over the northeast region (NER), India. Reanalysis data of FRP along with emission rates of trace gases have been retrieved from Global Fire Assimilation System. Results showed that average FRP was estimated to be 0.37 Wm^?2 with the highest value in Mizoram (0.16 Wm^?2) among 7-states of the study region. Temporally, relatively higher FRP occurred during the year of 2006 and 2010 while lowest in 2017. FRP-based VOCs and NOx emission estimates were 431 and 69.5?mg/m²/day, respectively which are consistent with observed FRP. Among different groups of VOCs, oxygenated species were the largest group (~56%) estimated followed by alkenes, alkanes, aromatics, and biogenic. Photochemical reactivities of VOCs were estimated using propylene-equivalent and maximum incremental reactivity methods which showed oxygenated species had the highest contributions in chemical reactivity. Based on the MIR scale, the top ten leading contributor species for ozone (O₃) formation were in descending order of formaldehyde, acetaldehyde, ethene, propene, toluene, butane, isoprene, methanol, pentene, and hexane which accounted for approximately 97% of total ozone formation. We also examined the ozone formation regime using VOCs/NOx ratios which indicated that O3 formation was likely to be VOC-sensitive over NER. Our results could be used for the understanding of FRP-based trace gas emissions during biomass burning and to establish effective preventive measures for reduction in O₃ pollution.