10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Urban Substrates: Atmospheric Particle-bound Radionuclide Traps - The Example of Beryllium-7
PHILIPPE LAGUIONIE, Denis Maro, Luc Solier, Marianne Rozet, Didier Hébert, Pierre Roupsard, Olivier Connan, IRSN
Abstract Number: 12 Working Group: Remote/Regional Atmospheric Aerosol
Abstract In the context of chronic or accidental release of radioactive particles into the atmosphere, knowing atmospheric particle-bound radionuclide total (dry and wet) deposition flux on ground surfaces and the deposited radionuclide mobility is essential to assess risks both on populations and environment. Fluxes of deposition, of re-emission into the atmosphere, and of radionuclide transfer between rainwater and ground surfaces differ in urban and rural environments which are characterized by different surface types, heterogeneities and local micro-meteorologies. In particular, interactions between rainwater and urban surfaces have often been only considered as dry-weather deposited particles washing by rainwater flowing. First, this study investigated the ability of seven urban substrates (horizontal asphalt and grass, vertical façade coating and glass, and tilted zinc, slate and tiles) to permanently trap rainwater beryllium-7 at month scale. Beryllium-7 is a radioactive tracer naturally present in the environment (7Be, T1/2=50.3 days). Second, results were extended to a urban catchment (Pin Sec urban catchment in Nantes; area of 310 000 m²), knowing the repartition of each surface type in the total area of the catchment. The experimental set-up consists of two sets of each substrate: the first one was exposed to wet and dry atmospheric particle-bound 7Be deposition whereas the second one was only exposed to dry deposition. The results showed that mean urban substrate retention rates present disparities linked to the surface orientation (main factor) and the substrate nature (secondary factor). Retention rates of horizontal, tilted and vertical surfaces were respectively between 65% and 93%, 48% and 59%, and 3% and 4%. The results also showed that the Pin Sec urban catchment area could trapped between 57 ± 25% and 83 ± 33% of the rainwater 7Be at month scale.