35 P 05 The theory of the interaction of atmospheric aerosol with underlying surface

J. Aerosol Sci., Vol. 24, Suppl. I, pp. $389-$390, 1993 Printed in Great Britain.

0021-8502/93 $6.00 + 0.00 Pergamon Press Ltd

35 P 05

THE THEORY OF THE INTEMCTION OF ATHOSPHERIC AEROSOL WITH UNDERIYING SUP~ACE M.V. Buikov Institute of Radioecology of Ukrainian Academy of Agricultural Sciences,L. Tolstoy str.,14,252033 Kiev KEYWORDS Aerosol particles, resuspension, dry-deposition, turbulent near-surface air layer, turbulent diffusivity,sedimentation, equilibrium concentration Interaction of wind with underlying surface through resuspension makes great contribution to the total amount of atmospheric aerosol. Dry deposition process results in cleaning of atmosphere and contamination of near-surface air layer, soil and vegetation. The exact solution of the problem of turbulent transportation of pollution taking into account resuspension and dry-deposition may be useful for the interpretation of observational data and for the improvement of the calculation methods to describe aerosol exchange of surfase with air. For horizontally homogeneous condition the equations describing the exchange process are O#z

(u,~za~-~z + v q

)=0

(a )

a-Wa Q = vdq (% ,t)-7 Q(t)=-j(t).

( 2 )

v and vd are friction, sedimentation and dry deposition velocities; zo is rougness height; ~ is von Karman' s constant; 7 is resuspension intensity. The equation (2) is Blinn's boundary condition. (Blinn,1976). The time to reach steady state to aerosol exchange of air with surface (~ I/V) is very great and it may be taken that q corresponds to Q(t). The exact solution $389

$390

M. V BUIKOV

of the equations (I) and (2) is q(z,t)=(q(zl)-j/v )(z~/zo)~ + j/v;

Z : v/m u,.

(3)

Q(t)=Qm+ (Qo-Q0o)exp(-t/to).

Qo: Q(o);

q~= q(z,) L ~17; ~ = (z,/Zo)~.

(5) (6)

j :-(Qo-Qo0) exp(-t/to)It o. t-*= o 7/(I+va(~-I) %) "

(7)

q(z) is the known air-borne concentration at z:z,. The equation ( 3 ) is similar to that obtained by Gillette et Gl (1974). Some consequenses may be derived from this solution. I. The equilibrium value of Qw(Q) can never be reached (to is equal to some days); nevertheless it may play ~ortant part: e.g. when QoQm" 2. It can be shown that Q(t)~ t if 7 is equal to zero. 3. The total vertical pollution flux may be splitted in n a ~ l way into two components; down-up one, connected with resuspension (j,) and up-down one connected with dry-deposition (j~)(Wyngaard,Brost,1984). 4. The formula for 7 which may be useful in experimental procedure to measure 7 can be derived: 7 : [1+v (~-1)Iv ] [ 1 - j ~ l q ( z ) v ] I t ; Q = O. ( 8 ) 5. The theory developed can be applied for the est~tion of rate of spreading due to resuspension and dry deposition from polluted area to clean one. It may be shown that the rate of spreading and level of relative contamination are low

enough. REFER~OES

Gillette D.A.., Blifford I.H., F r i a r geophy8~c,GZ ~ c h , voi.79,~-4078.

D.W. (1974) J o ~ l

slinn w (1979),,4moap'B~c J~u~~,vol.lO ~ 3. wm~mrd J.o. , ~ s t R.A., (1984),Jo~.'r~l ot A t t i c

vol. 4,102-112.

oJ"

Peae~ch,