Nighttime removal of NO_x in the summer marine boundary layer

Abstract

The nitrate radical, NO 3 , and dinitrogen pentoxide, N 2 O 5 , are two important components of nitrogen oxides that occur predominantly at night in the lower troposphere. Because a large fraction of NO 2 reacts to form NO 3 and N 2 O 5 during the course of a night, their fate is an important determining factor to the overall fate of NO x (=NO and NO 2 ). As a comprehensive test of nocturnal nitrogen oxide chemistry, concentrations of O 3 , NO, NO 2 , NO 3 , N 2 O 5 , HNO 3 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 NO 3 and N 2 O 5 in converting NO x to HNO 3 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.