Articles | Volume 17, issue 11
Atmos. Chem. Phys., 17, 6907–6923, 2017
https://doi.org/10.5194/acp-17-6907-2017
Atmos. Chem. Phys., 17, 6907–6923, 2017
https://doi.org/10.5194/acp-17-6907-2017

Research article 13 Jun 2017

Research article | 13 Jun 2017

Diurnal fluxes of HONO above a crop rotation

Sebastian Laufs1, Mathieu Cazaunau2,3, Patrick Stella4,5, Ralf Kurtenbach1, Pierre Cellier4, Abdelwahid Mellouki2, Benjamin Loubet4, and Jörg Kleffmann1 Sebastian Laufs et al.
  • 1Physikalische und Theoretische Chemie, Fakultät 4, Bergische Universität Wuppertal, Gaußstraße 20, 42119 Wuppertal, Germany
  • 2ICARE-CNRS, 1 C Av. de la Recherche Scientifique, 45071 Orléans CEDEX 2, France
  • 3LISA, UMR7583, CNRS, Universités Paris Est Créteil et Paris Diderot, 94010 Créteil, France
  • 4UMR ECOSYS, INRA, AgroParisTech, Université Paris-Saclay, 78850, Thiverval-Grignon, France
  • 5UMR SADAPT, AgroParisTech, INRA, Université Paris-Saclay, 75005, Paris, France

Abstract. Nitrous acid (HONO) fluxes were measured above an agricultural field site near Paris during different seasons. Above bare soil, different crops were measured using the aerodynamic gradient (AG) method. Two LOPAPs (LOng Path Absorption Photometer) were used to determine the HONO gradients between two heights. During daytime mainly positive HONO fluxes were observed, which showed strong correlation with the product of the NO2 concentration and the long wavelength UV light intensity, expressed by the photolysis frequency J(NO2). These results are consistent with HONO formation by photosensitized heterogeneous conversion of NO2 on soil surfaces as observed in recent laboratory studies. An additional influence of the soil temperature on the HONO flux can be explained by the temperature-dependent HONO adsorption on the soil surface. A parameterization of the HONO flux at this location with NO2 concentration, J(NO2), soil temperature and humidity fits reasonably well all flux observations at this location.

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Short summary
Sources of nitrous acid (HONO), a major precursor of the OH radical, are still under controversial discussion. Since mainly ground surface sources have been proposed, HONO fluxes were measured above an agricultural field. Positive daytime fluxes were observed which showed strong correlation with the product of the NO2 concentration and J(NO2). These results indicate HONO formation by photosensitized heterogeneous conversion of NO2 on soil surfaces as observed in recent laboratory studies.
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