NMVOC emissions and their formation into secondary organic aerosols over India using WRF-Chem model

Abstract

Non-methane volatile organic compounds (NMVOC) emissions from anthropogenic, open burning, and biogenic sources, and their formation into secondary organic aerosols (SOA) over India have been examined. The emissions databases EDGAR-HTAP (v2.2), Fire Inventory from NCAR (FINN), and the Model of Emission of Gases and Aerosol (MEGAN) were used. India emits 3% of annual global NMVOC at 30.45 Tg (anthropogenic:8.97; open burning: 2.01; biogenic: 19.47 Tg/year). Spatial and temporal variations for SOA were simulated using the WRF-Chem model combined with a secondary organic aerosol model for the year 2018. WRF-Chem model was expanded to include a scheme of parameterization for estimating isoprene-derived SOA. Annual estimated SOA production was 2.93 Tg/year, 4% of the global SOA.The annual SOA concentration over India was 3.19 ± 2.18 μg/m3 (post-monsoon: 5.16 ± 3.29, winter: 3.74 ± 2.55, summer: 2.62 ± 1.78, and monsoon: 1.24 ± 0.84 μg/m3). WRF-Chem model underestimated the SOA levels, possibly due to incomplete emission inventories and missing NMVOC precursors, including biogenic and primary organic carbon emissions that add to SOA formation. The annual anthropogenic and biogenic SOA had a near equal contribution of 50% mostly from populated regions and evergreen forests.