AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Model Evaluations of Heterogeneous Nitryl Chloride Production Sources during CalNex 2010
WAYNE CHANG, Nicole Riemer, University of Illinois at Urbana-Champaign
Abstract Number: 162 Working Group: Aerosol Chemistry
Abstract Recent ambient observations of nitryl chloride (ClNO$_2), a nighttime precursor of the reactive chlorine radical, showed direct correlations with dinitrogen pentoxide (N$_2O$_5) levels. This points towards the N$_2O$_5 heterogeneous hydrolysis on chloride-containing aerosols as the main ClNO$_2 production pathway. However, when state-of-the-art parameterizations for N$_2O$_5 heterogeneous reaction rates and ClNO$_2 production yields were implemented in air quality models, simulation results always under-predicted ambient ClNO$_2 concentrations. Sources of model uncertainty are both the parameterization of heterogeneous reaction rates as a function of meteorological conditions and aerosol compositions, and the emission inventory for gaseous chlorine species that can partition into the particle phase. In our work we incorporated a new hybrid N$_2O$_5 heterogeneous hydrolysis parameterization into the WRF/Chem model, taking into account both the uptake enhancement by the presence of particulate chloride and the uptake suppression by organic coating. Our modeling domain is the South Coast Air Basin of California and the modeled episode is the CalNex 2010 measurement campaign. We will present the sensitivity of ClNO$_2 production to spatial and temporal variations in anthropogenic chlorine emission sources, as well as the resulting impact on criteria pollutants in the South Coast Air Basin of California.