Implications of Ambient Ammonia on Aerosol Acidity and Reactive Nitrogen Measurements

This study describes two projects involving recent research on atmospheric ammonia. The first project investigates differences in modelling techniques of aerosol acidity using data from two recent field campaigns. Our results show that allowing or disallowing gas-particle partitioning in the Extended Aerosol Inorganic Model (E-AIM) changed the average modelled aerosol activity of H+ from one campaign by seven orders of magnitude and that disallowing gas-particle partitioning may not accurately represent the chemical state of the aerosols. The second project investigates the interference of reduced nitrogen in commercial chemiluminescent nitrogen oxide monitors with molybdenum oxide catalytic converters. This phenomenon is strongly dependent on the temperature of the catalytic converter. Our results show these instruments can have high conversion efficiencies of gaseous NH3 and NH4+ salts to NO at typical reported converter temperatures, but conversion efficiency varies between instruments and may be the result of uncertainty in reported converter temperature.MAS