Carbon-coated annular denuders and ion chromatographic measurements for the determination of nitrogen-containing species (NO2 and NOy) in remote atmospheres

Nitrogen oxides play a major role in determining the chemical properties of the atmosphere. Measurements of these species in remote areas are rare, although their relevance is well established. This is particularly true for polar sites. In order to fill this gap, an annular diffusion denuder system, with an alkaline carbon surface, for the simultaneous collection of nitrogen dioxide (NO2) and peroxyacetyl nitrate and other organic nitrates has been developed. In the collection stage, nitrogen dioxide (NO2) and NOy yield nitrite (NO2-) and nitrate (NO3-) ions, respectively. These are extracted after sampling and analysed by ion chromatography. The experimental set-up was tested during two expeditions carried out in sites located in Arctic and Antarctica. The Arctic concentrations were found between 10 and 170 ng m(-3) for NO2 and between 100 and 600 ng m(-3) for NOy while in Antarctica concentrations were found between 10 and 300 ng m(-3) for NO2 and between 300 and 700 ng m(-3) for NOy. Results obtained from these expeditions demonstrate that the minor components may be measured at levels as low as a few nanograms per cubic meter in remote atmospheres using the suggested technique. The reported concentrations are to be considered among the first observations of gas phase nitrogen compounds in polar areas. (C) 1999 Published by Elsevier Science B.V. All rights reserved.