[1] 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

1] Concentrations of NO 3 and N 2 O 5 were measured using an in situ instrument aboard the NOAA research vessel Ronald H. Brown in the marine boundary layer along the United States east coast as part of the New England Air Quality Study (NEAQS) in the summer of 2002. We analyze the results in terms of the loss partitioning and sink budgets for both of these compounds. Analysis of the data on nights with large N 2 O 5 losses allowed for a determination of its heterogeneous uptake coefficient and gave g(N 2 O 5 ) = 0.03 ± 0.02. Reactions of NO 3 with terrestrially emitted biogenic volatile organic compounds (isoprene and monoterpenes), advected into the marine boundary layer, and with DMS emitted from the ocean surface were also important. In general, loss of NO 3 and N 2 O 5 was rapid, and the partitioning between NO 3 and N 2 O 5 losses was roughly equal. Because rapid N 2 O 5 loss consumes NO x at twice the rate of the reaction of NO 2 with O 3 , whereas rapid NO 3 loss leads to NO x removal at the same rate, the equal partitioning of losses indicates a nocturnal NO x loss rate of approximately 1.5 times the rate of NO 2 + O 3 . Activation of halogens from the uptake of NO 3 and N 2 O 5 on sea salt was calculated to have produced substantial amounts of active Cl on some mornings through the nocturnal formation and sunrise photolysis of ClNO 2 if the process proceeded at the rate determined by laboratory studies. However, there was no direct observational evidence to test the magnitude of the predicted source. Citation: Aldener, M., et al. (2006), Reactivity and loss mechanisms of NO 3 and N 2 O 5 in a polluted marine environment: Results from in situ measurements during New England Air Quality Study 2002,