Emissions of Volatile Organic Compounds from Biomass Burning Sources and their Ozone Formation Potential over India

Thousands of volatile organic compounds (VOCs) in the Earth's atmosphere exist which play an important role in various photochemical processes. However, the global model simulations of tropospheric chemistry deal with limited data of speciated VOCs. In the present study, we have used the Global Fire Emissions Database inventory of VOCs emitted from biomass burning in India during the period from 1997 to 2009. We have also analysed data of some VOCs measured in the upper troposphere over India for the year 2008. In this study, the major species analysed are C₂H₄, C₂H₄O, C₂H₆, C₂H₆S, C₃H₆, C₃H₆S, C₃H₈, C₅H₈, CH₃OH, higher alkanes, higher alkenes, terpenes and toluene lumps. The biomass burning emissions of VOCs show large inter-annual variation. For example, the annual emission estimates of non-methane hydrocarbons (NMHCs) and CH3OH varied in the range 100-470 and 46-211 Gg yr^-1 respectively. The major biomass sources were broadly categorized as deforestation, fuel-wood, forest and agricultural residues. The agricultural residue burning is the most dominant among the several biomass burning sources contributing to the emissions of CH₃OH (59%), isoprene (80%) and toluene (72%). On the other hand, the major sources for NMHCs emission were agricultural residues and deforestation during all the years. The fire count data detected using the satellite-based Along Track Scanning Radiometer have been used to directly refer to the seasonal and inter-annual variations of biomass burning activities. We have estimated the propylene-equivalent concentrations of different light NMHCs measured in the upper troposphere over India. Role of stratospheric intrusion in the distribution of NMHCs has been analysed using the potential vorticity data.