Nighttime Oxidation of VOCs at Appledore Island, ME During ICARTT 2004

Ambient mixing ratios of trace gases important to nighttime chemistry of nitrate radical (NO3) were measured at Appledore Island, ME, USA from July 8 - August 15, 2004 as part of the International Consortium for Atmospheric Research on Transport and Transformation (ICARTT) campaign. These measurements were used to investigate the nighttime oxidation of volatile organic compounds (VOCs) and nitric oxide (NO) at Appledore Island during the campaign, utilizing ambient temperature and pressure measurements along with rate data for reactions that directly remove NO3 from the atmosphere. Additionally, ambient concentrations of dinitrogen pentoxide (N2O5) were estimated for the nighttime hours from the measured concentrations of nitrogen dioxide (NO2) and NO3 and the corresponding equilibrium constant. The estimated N2O5 concentrations and measurements of aerosol chemistry and size distribution were used to evaluate the importance of heterogeneous N2O5 hydrolysis to the overall nighttime removal of nitrogen oxides (NOx, = NO + NO2) relative to the gas-phase reactions of NO3 with VOCs.