Modeling global secondary organic aerosol formation and processing with the volatility basis set: Implications for anthropogenic secondary organic aerosol

The volatility basis set, a computationally efficient framework for the description of organic aerosol partitioning and chemical aging, is implemented in the Goddard Institute for Space Studies General Circulation Model II' for a coupled global circulation and chemical transport model to simulate secondary organic aerosol (SOA) formation. The latest smog chamber information about the yields of anthropogenic and biogenic precursors is incorporated in the model. SOA formation from monoterpenes, sesquiterpenes, isoprene, and anthropogenic precursors is estimated as 17.2, 3.9, 6.5, and 1.6 Tg yr (1), respectively. Reducing water solubility of secondary organic gas from 105 to 103 mol L (1) atm (1) (1 atm = 1.01325 x 10(5) N m (2)) leads to a 90% increase in SOA production and an increase of over 340% in total atmospheric burden, from 0.54 to 2.4 Tg. Increasing the temperature sensitivity of SOA leads to a 30% increase in production, to 38.2 Tg yr(-1). Since the additional SOA is formed at high altitude, where deposition time scales are longer, the average lifetime is doubled from 6.8 to 14.3 days, resulting in a near tripling of atmospheric burden to 1.5 Tg. Chemical aging of anthropogenic SOA by gas-phase reaction of the SOA components with the hydroxyl radical adds an additional 2.7-9.3 Tg yr(-1) of anthropogenic SOA to the above production rates and nearly doubles annual average total SOA burdens. The possibility of such high anthropogenic SOA production rates challenges the assumption that anthropogenic volatile organic compounds are not important SOA precursors on a global scale. Model predictions with and without SOA aging are compared with data from two surface observation networks: the Interagency Monitoring of Protected Visual Environments for the United States and the European Monitoring and Evaluation Programme.