The Role of Organic Nitrates in the Chemistry of the Continents: An Assessment Using WRF-CHEM

Abstract:

Nitrogen oxides (NO_x) play a fundamental role in the chemistry of atmospheric oxidation and affect air quality and climate. Recent experiments have shown that formation of organic nitrates is a more important immediate sink of NO_x than nitric acid in the rural continental locations. In particular, in regions with high emissions of biogenic volatile organic compounds (BVOCs), isoprene and monoterpene derived organic nitrates can be expected to control the fate of nitrogen oxides, and consequently the ozone production efficiency. Thus understanding of the complex production and loss processes of organic nitrates are required for determining the lifetime of NO_x in the present day and in preindustrial times. Using the chemical transport model WRF-Chem, we investigate impacts of organic nitrate chemistry on the NO_x and ozone budgets of the southeastern United States. We evaluate changes to the NO_x budget in response to decreases in anthropogenic NO_x emissions. The model has been updated with recent advances in representation of BVOC oxidation chemistry and deposition rates, including a detailed representation of organic nitrates. We compared simulations to measurements from the Southern Oxidant and Aerosol Study (SOAS) campaign in central Alabama in summer 2013 and examine the sensitivity to emission rates.