Preventing biogenic secondary organic aerosols formation in India

Abstract

Biogenic secondary organic aerosols (b-SOA, a subset of PM2.5) are generally assumed uncontrollable, as their precursors are of natural origin. The underlying science that anthropogenic pollutants aid in transforming biogenic volatile organic compounds (b-VOC) into the b-SOA opens the avenue to prevent b-SOA formation through anthropogenic emission control. Sixty customised Weather Research and Forecasting-Chemistry (WRF-Chem) model simulations were undertaken for India in 2018. Five pollutants, TC(BC + OC), NOx, NMVOC, NH3 and SO2, were considered for emission reductions at three levels 25, 50 and 75%, and the resulting prevention of b-SOA formations was examined. TC and NOx emission control showed maximum potential in preventing b-SOA formation. A 10% reduction in TC emission prevented 4.5% b-SOA formation, and a similar reduction in NOx prevented 3.7% b-SOA across all seasons and regions. The residential combustion contributing 57% of TC emissions was one single important source for TC control, and for NOx, it was vehicles and coal-based power plants (emission share over 80%). Specific reductions in anthropogenic emissions have been presented seasonally and regionally to prevent b-SOA formation.