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Journal of Atmospheric Chemistry 60, 3 (2009) 253-271
Rainfall chemistry: long range transport versus below cloud scavenging. A two-year study at an inland station (Opme, France)
Guillaume Bertrand ( ) 1, Hélène Celle-Jeanthon 1, Paolo Laj 2, J. Rangognio 3, Gilles Chazot 4, 5

The present study investigates the chemical composition of wet atmospheric precipitation samples on a daily and an intra-event timescales in Opme, an experimental meteorological station located near Clermont-Ferrand, France. The samples have been collected from November 2005 to October 2007. A total of 217 rainwater samples, integrated for 24 h, were collected and analyzed for pH, conductivity, Na+, K+, Mg2+, NH4+, Ca2+, Cl−, NO3− , SO42− , PO43− and HCO3−. The composition of the rainwater collected appeared to be controlled by the following potential sources: neutralisation process (association among calcium, ammonium with nitrate and sulphate), marine and terrestrial sources. In order to determine the role of long-range transport, the integrated events were classified according to four origins of air-masses: (1) West, (2) North and East, (3) South including Iberian and Italian Peninsulae and (4) local. This analysis allows identifying the source areas of the different association of elements defined. Although calcium is always dominant, total content of rainfall is variable and neutralisation process can be more or less efficient and specific. Rainout (long-range transport) and washout (below-cloud scavenging) were investigated through intra-event measurements of chemical species. Four rain-events have been selected according to the four classes of origins of air-masses. It appears that the first fractions are responsible for an important part of the chemical content of the whole event. Terrestrial species, locally emitted, induce the neutralisation process of acid species. Local meteorological conditions, such as wind's speed and direction, play an important role as they could provoke recharges of the below cloud air column during the event.
1 :  Laboratoire Magmas et Volcans (LMV)
CNRS : UMR6524 – Institut de recherche pour le développement [IRD] – INSU – Université Blaise Pascal - Clermont-Ferrand II – Université Jean Monnet - Saint-Etienne
2 :  Laboratoire de météorologie physique (LaMP)
CNRS : UMR6016 – INSU – Université Blaise Pascal - Clermont-Ferrand II
3 :  Groupe d'étude de l'atmosphère météorologique (CNRM-GAME)
CNRS : URA1357 – INSU – Météo France
4 :  Domaines Océaniques
INSU – Institut d'écologie et environnement – Institut Universitaire Européen de la Mer (IUEM) – Université de Bretagne Occidentale (UBO) – Observatoire des Sciences de l'Univers – CNRS : UMR6538
5 :  Université européenne de Bretagne (UEB)
PRES Université Européenne de Bretagne (UEB)
Planète et Univers/Sciences de la Terre/Géochimie

Sciences de l'environnement/Milieux et Changements globaux
Rainwater – Major ions – Sequential sampling – Air-mass back-trajectories – Chemistry – France
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J.Atmos-Chem-Chazot.pdf(906.1 KB)