Title: A new method for assessing the aerosol to rain chemical composition relationships
Citation: ATMOSPHERIC RESEARCH vol. 118 p. 295-303
Publication Year: 2012
JRC N°: JRC68075
ISSN: 0169-8095
URI: http://www.sciencedirect.com/science/article/pii/S0169809512002566
DOI: 10.1016/j.atmosres.2012.07.020
Type: Articles in periodicals and books
Abstract: Measurements were conducted at three sampling sites located at different altitudes in the centre of France during two years, both in the rain and aerosol phases. The rain was sampled at a boundary layer site while the aerosol particles were collected at two different altitudes, which allow a better characterization of the vertical atmospheric column being washed out. Various chemical analyses were performed to characterize reactive (NO3-, SO42-, NH4+ and K+) and inert (7Be, 210Pb and 137Cs) species transfer from the aerosol to the rain phase. This set-up was ideal to calculate the washout ratio (WR) using different concentrations of the aerosol phase. Using the classical WR calculated with the aerosol concentration sampled at the same altitude than the rain collectors, we observed a seasonality of WR, with higher value in winter and lower value in summer for radionuclides. At the higher altitude site, local contaminations do not influence the aerosol concentration, which then should be representative of the whole atmospheric column. The annual variability is high at this site maybe because aerosol concentrations can be less concentrated than the whole atmospheric column when this later one is not well mixed. In order to increase the reliability of theWR, we propose a newmethod for calculating washout ratio from measurements at the rain collector level. This new calculation takes into account the height of the boundary layer, we observed that it decreased the variability of the washout ratio (for 7Be, 210Pb and NO3-), with less dependence to the season.
JRC Directorate:Health, Consumers and Reference Materials

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