Sebastian Laufs1, Mathieu Cazaunau2,3, Patrick Stella4,5, Ralf Kurtenbach1, Pierre Cellier4, Abdelwahid Mellouki2, Benjamin Loubet4, and Jörg Kleffmann11Physikalische 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, UMR 7583, CNRS, Université s Paris Est Créteil et Paris Di derot, 94010 Créteil, France 4UMR ECOSYS, INRA, AgroParisTech, Université Pa ris-Saclay, 78850, Thiv erval-Grignon, France 5UMR SADAPT, AgroParisTech, IN RA, Université Paris-Saclay, 75005, Paris, France
Received: 18 Nov 2016 – Accepted for review: 08 Dec 2016 – Discussion started: 09 Dec 2016
Abstract. Nitrous acid (HONO) fluxes were measured above an agricultural field site near Paris during different seasons, above bare soil and different crops 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 indicate 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.
Laufs, S., Cazaunau, M., Stella, P., Kurtenbach, R., Cellier, P., Mellouki, A., Loubet, B., and Kleffmann, J.: Diurnal fluxes of HONO above a crop rotation, Atmos. Chem. Phys. Discuss., doi:10.5194/acp-2016-1030, in review, 2016.