AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Rainout, Washout and Dry Deposition Contributions to the Total Deposition Flux of Heavy Metal Aerosol onto Surfaces of a Small Urban Catchment (Pin Sec, Nantes)
STÉPHANE PERCOT, Véronique Ruban, Philippe Laguionie, Denis Maro, Pierre Roupsard, Dominique Demare, IRSN
Abstract Number: 15 Working Group: Urban Aerosols
Abstract Pollutants associated to atmospheric particles in urban areas throughout the world have been characterized in many studies. The nature of surfaces as well as weather conditions and atmospheric turbulence influence the aerosol deposition. Previous studies in Nantes (France) on the Pin Sec catchment allowed the estimation of wet and dry atmospheric deposition fluxes. Thanks to these results further studies can now estimate the origin of atmospheric heavy metals by distinguishing rainout (long range transport) and washout (local scavenging) processes. The objective of this communication is to present the rainout, washout and dry deposition contributions to the total deposition flux of heavy metal aerosol on this catchment. The experiment was conducted between the 1st of September 2010 and the 31st of August 2011. The dry deposition of heavy metals was estimated using the dry deposition velocity of the tracer Beryllium 7 measured on urban surfaces. Regarding monthly wet deposition, the flux is calculated as the ratio of the mass of pollutants collected in a covered pluviometer. The rainout/washout ratio was determined by a new method which used monthly integrated data: heavy metal elements concentrations in rainwater and in aerosol particle, scavenging coefficient, reload rate of the local atmosphere, and meteorological parameters. In average, over the 10-month survey period, heavy metals (except for vanadium and lead) are mainly deposited by rainout process, showing evidence of long range sources. The rest of the atmospheric deposition is composed of dry deposition and washout which is the lowest part of deposition. These results are in good agreement with results of source emission showing that there is no evidence of emission of pollutants from local activity. Lead behaves differently: dry deposition and washout contributions suggest the existence of a local source. The consequences of these results and perspectives will be further discussed at the conference.