Nighttime removal of NOx in the summer marine boundary layer

The nitrate radical, NO₃, and dinitrogen pentoxide, N₂O₅, are two important components of nitrogen oxides that occur predominantly at night in the lower troposphere. Because a large fraction of NO₂ reacts to form NO₃ and N₂O₅ during the course of a night, their fate is an important determining factor to the overall fate of NO_x (=NO and NO₂). As a comprehensive test of nocturnal nitrogen oxide chemistry, concentrations of O₃, NO, NO₂, NO₃, N₂O₅, HNO₃ and a host of other relevant compounds, aerosol abundance and composition, and meteorological conditions were measured in the marine boundary layer from the NOAA research vessel Ronald H. Brown off the East Coast of the United States as part of the New England Air Quality Study (NEAQS) during the summer of 2002. The results confirm the prominent role of NO₃ and N₂O₅ in converting NO_x to HNO₃ at night with an efficiency on par with daytime photochemical conversion. The findings demonstrate the large role of nighttime chemistry in determining the NO_x budget and consequent production of ozone.