The flux of reactive nitrogen compounds from eastern North America to the western Atlantic Ocean

This paper describes the measurement of reactive nitrogen compounds as part of the 1986 Western Atlantic Ocean Experiment (WATOX). Species measured include NO and NO Y (NO Y = NO + NO 2 + NO 3 + HNO 3 + 2N 2 O 5 + HONO + PAN + R‐ONOx + fine NO 3 , where PAN is peroxyacetyl nitrate). A ferrous sulfate converter, which was subsequently determined to respond to PAN, was used to measure NOx' (NOx' = NO + NO 2 + ˜0.7 PAN). Although concentrations of NO Y reached several parts per billion in offshore urban plumes, average levels of NO Y in the planetary boundary layer (PBL) resemble those measured at rural sites along the east coast. Free tropospheric concentrations of NO Y were near continental background levels observed in previous studies. Concentrations of NO were typically below the detection limit of 20 parts per trillion in the free troposphere, with higher concentrations detected in the PBL. By combining the odd nitrogen data set with calculations of ambient air mass fluxes observed on each flight, we calculate an instantaneous gross N flux through the area from 31.5 to 44.1°N and 0 to 3000 m to be 18.5 kg N/s. The dependence of the magnitude of this flux upon specific meteorological conditions is discussed. For comparative purposes, we also combine our odd nitrogen data set with climatological wind data for the eastern seaboard to estimate an annual gross N flux of 0.5 Tg N/yr, significantly less than previous estimates.