Validation of aerosols dry deposition velocity models with new experimental data

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1 Validation of aerosols dry deposition velocity models with new experimental data M. Talbaut 1, P.E. Damay 2, D. Maro 2, A. Coppalle 1, O. Connan 2, D. Hebert 2 1 UMR 6614 CORIA, St Etienne du Rouvray, France 2 Institut de Radioprotection et de Sûreté Nucléaire (IRSN), DEI/SECRE/LRC, Cherbourg-Octeville, France

2 Aerosol pollution in the atmosphere impact on the health impact on the ecosystem if deposition The impact of the aerosol pollution on ecosystem must be evaluated We have to study some transfer functions of particles on vegetated canopies : the dry aerosol deposition velocity, Vd - Air quality prediction and accidental release need to know this parameter - There are several models of aerosol dry deposition which take into account turbulence and particle size for a large range of sizes But

3 Evolution of Vd in function of the aerosol size for different models Vd (cm.s -1 ) m.s Alexandre Petroff (thesis, 2005) Diameter (µm) For neutral atmospheric conditions : Large uncertainties (more than two orders of magnitude) between dry deposition velocities calculated from various operational models on rural environment

4 ..and for nanoparticles (<100nm), there is not enough reliable experimental data Needing of experimental data on Vd - onto rural aeras - for different submicronic aerosol sizes Objectives of the work To develop a method to quantify dry deposition for submicronic aerosol : the Eddy Covariance method To provide experimental data of the dry deposition velocity in a rural environment To study the effect of micro-meteorology and aerosol size To make comparison with 2 models : Slinn and Zhang et al.

5 Vd Vd = = F C W' C' C Choice of the experimental site: Over a maize field Strong atmospheric stability variability between night and day Main hypothesis for using EC: Aerosol concentration stable for 30 min (no manmade sources) Horizontal homogeneity (fetch, footprint) Measurements in the constant fluxes layer

Anemometer 81000 Deposition Aerosols F Vd = c Sampling Tube Electrical low

6 Eddy Covariance Method using atmospheric aerosols WIND Deposition mechanism Atmospheric Eddies Turbulent fluctuation measurements Ultrasonic Anemometer Young Anemometer Deposition Aerosols F Vd = c Sampling Tube Electrical low Measurement pressure particle concentration device impactor (ELPI) w, w For 12 size classes c, c

w C W C Vertical aerosol flux 3 10-7 2 10-7 1 10-7 0-1 10-7 -2 10-7 -3 10-7 -4 10-7 -5 10-7 -6

7 w C W C Vertical aerosol flux Vd F W' C' = = For each 30 min period C C w c > 0 for emission flux w c < 0 for deposition flux

8 Important data processing See publication in Journal of Aerosol Science, 40, , 2009 : P. Damay, D. Maro, A. Coppalle, E. Lamaud, O. Connan, D. Hebert, M. Talbaut, M. Irvine Size resolved eddy covariance measurements of fine particle vertical fluxes, Data processing : Verticality correction (w=0) Filtration (to avoid the linearity between C and T) Quality tests : - Stationnarity (variation of the flux < 30%) - Constant flux layer (Turbulent characteristic integral < 30 %) Spectral analysis 7,0E+05 Cospectre -W'C' Cospectre W'T' 0,04 Spectral loss due to the low response time of the devices (ELPI) Spectral correction based on the similarity between the cospectra of the heat flux (w T ) and the cospectra of the vertical particule flux (w C ) n.w C (n) 6,0E+05 5,0E+05 4,0E+05 3,0E+05 2,0E+05 1,0E+05 0,0E+00 0,035 0,03 0,025 0,02 0,015 0,01 0,005 0 n.w T (n) -1,0E+05-0,005 0,001 0,01 0, adimensionned frequency (n.z/u)

9 Example of diurnal pattern evolution of the dry deposition velocity for 2 aerosol size Vd (m.s -1 ) 5.E-3 4.E-3 3.E-3 2.E-3 1.E-3 Stage 3 = µm Stage 4 = µm Friction velocity U* sensible heat flux H 0.E+0 0 0:00 6:00 12:00 18:00 0:00-1.E Time (UT) U* and H normalized Important variation between diurnal and nocturnal results for : -Dry deposition velocity Vd - Sensible heat flux H - Friction velocity U* max value of m.s -1 Similar shape for other size classes

10 Impact of micrometeorological parameters : Sensible heat flux H Vd increases with H y = 10-5 x + 0, R 2 = 0,7307 Aerosol size of 33nm But don t forget the influence of the mechanical turbulence Vd (m.s -1 ) H (W.m -2 ) The dispersion of the points can be due to : - experimental uncertainties - the mechanical effect of U*

11 Impact of micrometeorological parameters : the friction velocity U* Aerosol size of 33nm H < 50 W.m -2-2 H > 50 W.m low sensible heat flux high sensible heat flux Dispersion of the points For low thermal turbulence, (H small) : Vd is linear with U* Vd (m.s -1 ) Linear regression for H < 50 W.m -2 y = 0,0041x - 0,0003 R 2 = 0, U* (m.s -1 ) Vd/U* constant similar shapes for the other aerosol sizes (but only for the days where the values of H are contrasted between day and night)

12 Low values of H -> low thermal turbulence For neutral and stables conditions: Vd/U*=constant The average of Vd/U* can be plotted in function of the size 1 Experimental measurements Impact of aerosol size -Constant for little sizes -Low decrease -Strong increase for the biggest sizes Vd/U* Diameter (µm)

13 100 Brownian Diffusion Interception Impaction 10 Vd (cm.s -1 ) Diameter (µm) Sedimentation g r Deposition processes : -Brownian diffusion -Interception -Impaction -Sedimentation

14 Comparison with Slinn et Zhang analytic models Experimental measurements Slinn Zhang et al. Vd/U* Diameter (µm)

15 Brownian diffusion Experimental measurements Slinn Brownian diffusion Slinn Zhang et al. Brownian diffusion Zhang et al. A) Vd/U* Diameter (µm)

16 Interception-Impaction Sedimentation Experimental measurements 10 Zhang et al. Impaction Zhang et al. Interception Zhang et al. Slinn 1 Slinn Interception Slinn Impaction Experimental measurements Zhang et al. Sedimentation Zhang et al. Slinn Slinn Sedimentation Vd/U* 0.01 Vd/U* Diameter (µm) Diameter (µm)

17 Conclusion Development a new method based on Eddy covariance Data of dry deposition velocity on maize Effect of the micrometeorological parameters H and U* on Vd Mean Values of Vd/U* (in stable and neutral conditions) for different sizes : between 7 nm and 2 µm Effect of the aerosol size on the dry deposition Comparison with Zhang and Slinn models of deposition Future Measurements on other substrates ( grass, soil) have to be performed to study the effect of the substrate on the deposition A sensibility study could be realized to see the effect of each parameter used in the model because these parameters are often linked to measurements realized in wind tunnel and not in situ atmospheric conditions

Collaborations : Thanks for your attention Université d Edinburgh : Robert Clement Air Quality Research Division Environment of Toronto : Alexandre Petroff Université de Stockholm : Chirster

18 Collaborations : Thanks for your attention Université d Edinburgh : Robert Clement Air Quality Research Division Environment of Toronto : Alexandre Petroff Université de Stockholm : Chirster Johansson and Douglas Nilsson CORIA Rouen : Alexis Coppalle and Martine Talbaut INRA of Bordeaux : Éric Lamaud. Mark Irvine and Jean-Marc Bonnefond Université de Caen : Bertrand Pouderoux IRSN/DEI : Denis Boulaud IRSN/DSU/SERAC : Jacques Vendel, François Gensdarmes and Guillaume Basso IRSN/DEI/SECRE/LRC : Denis Maro, Pierre Damay, Olivier Connan and Didier Hébert Article : Damay, P. E., Maro. D., Coppalle, A., Lamaud. E., Connan, O., Hébert. D., Talbaut, M. et Irvine. M. (2009) Size resolved eddy covariance measurements of fine particle vertical fulxes. Journal of Aerosol Science 40, Congress : Damay, P. E., Maro. D., Coppalle, A., Lamaud. E., Connan, O., Hébert. D., Talbaut, M. et Irvine. M. (2008) Contribution à l'étude des vitesses de dépôt sec des aérosols submicroniques dans un écosystème prairial. 23 ième Congrès Français sur les aérosols. Paris. (Talk) Damay, P. E., Maro. D., Coppalle, A., Lamaud. E., Connan, O., Hébert. D., Talbaut, M. et Irvine. M. (2008) Measuring dry deposition velocity of submicronic aerosols in a prairie by eddy correlation using an electrical low pressure impactor. European Aerosol Conference. Thessaloniki (poster and back-up talk) Damay, P. E., Maro. D., Coppalle, A., Lamaud. E., Connan, O., Hébert. D., Talbaut, M. et Irvine. M. (2009) Mesure par corrélation turbulente de la vitesse de dépôt sec des aérosols submicroniques sur différents couverts naturels. 24ième Congrès Français sur les aérosols. Paris. (Talk) Damay, P. E., Maro. D., Coppalle, A., Lamaud. E., Connan, O., Hébert. D., Talbaut, M. et Irvine. M. (2008). New data of dry deposition velocity of submicron aerosol on several rural substrates and comparison with models. European Aerosol Conference. Karlsruhe (Talk) P. DAMAY Thesis defending - April 2010 Page 18

EQUIPMENT AND METHOD For this study of mesoscale atmospheric dispersion, two systems measuring

EQUIPMENT AND METHOD For this study of mesoscale atmospheric dispersion, two systems measuring CONTRIBUTION TO THE STUDY OF ATMOSPHERIC DISPERSION OF A MESOSCALE POLLUTANT: USE OF KRYPTON-85 RELEASED BY THE COGEMA LA HAGUE NUCLEAR SPENT FUEL REPROCESSING PLANT AS ATMOSPHERIC TRACER Denis Maro 1,