| Summary: | The concentrations of the reactive nitrogen species NO2, NOx(= NO + NO2), NOy (the sum of all compounds of nitrogen and oxygen with the exception of N2O), particulate NO3 −, and volatile NO3 − were measured from ship and aircraft platforms over the western North Atlantic Ocean as part of the GCE/CASE/WATOX experiment. Air masses sampled were divided into continentally influenced and typical marine on the basis of trajectories, and radon and black carbon measurements. From the NO3 − measurements on size separated aerosol and the altitude variations of volatile NO3 − and particulate NO3 −, a significant interaction between volatile NO3 − and sea salt aerosol was indicated. The average marine concentrations measured were: 18 nmol m−3 for NO2, 29 nmol m−3 for NOx, 46 nmol m−3 for NOy, and 10 nmol m−3 for total inorganic NO3 −. The reactive nitrogen species were present at concentrations some 40 times those encountered in the remote Pacific Ocean, whereas the inorganic NO3 − was only 3 times higher.
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