Atmos. Chem. Phys. Discuss., 10, 1309-1353, 2010
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This discussion paper has been under review for the journal Atmospheric Chemistry and Physics (ACP). Please refer to the corresponding final paper in ACP.
Nocturnal nitrogen oxides at a rural mountain-site in South-Western Germany
J. N. Crowley1, G. Schuster1, N. Pouvesle1, U. Parchatka1, H. Fischer1, B. Bonn2, H. Bingemer2, and J. Lelieveld1
1Max-Planck-Institut für Chemie, Atmospheric Chemistry Dept., Mainz, Germany
2Universität Frankfurt, Fachbereich Geowissenschaften, Frankfurt am Main, Germany

Abstract. A new, two-channel instrument for simultaneous NO3 and N2O5 monitoring was used to make the first comprehensive set of nocturnal NOx measurements (NO, NO2, NO3 and N2O5) at the Taunus Observatory, a rural mountain site (Kleiner Feldberg) in South-western Germany. In May 2008, NO3 and N2O5 mixing ratios were well above the instrumental detection limit (a few ppt) on all nights of the campaign and were characterised by large variability resulting from inhomogeneously distributed sinks. The concentrations of NO3, N2O5 and NO2 were consistent with the equilibrium constant, K2, defining the rates of formation and thermal dissociation of N2O5. A steady-state lifetime analysis showed that nocturnal NOx losses were generally dominated by reaction of NO3 with volatile organic compounds in this forested region, with N2O5 uptake to aerosols of secondary importance. Analysis of a limited dataset obtained at high relative humidity indicated that the loss of N2O5 by reaction with water vapour is less efficient (> factor 3) than derived using laboratory kinetic data. The fraction of NOx present as NO3 and N2O5 reached ≈20% on some nights, with night-time losses of NOx competing with daytime losses.

Citation: Crowley, J. N., Schuster, G., Pouvesle, N., Parchatka, U., Fischer, H., Bonn, B., Bingemer, H., and Lelieveld, J.: Nocturnal nitrogen oxides at a rural mountain-site in South-Western Germany, Atmos. Chem. Phys. Discuss., 10, 1309-1353, doi:10.5194/acpd-10-1309-2010, 2010.
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