McKay, Donald. "Front matter" Multimedia Environmental Models ...

and
Adding gives
and
where
©2001 CRC Press LLC
f I – f A = N/D A
(f W – f A) = N(1/D W + 1/D A) = N/D V
N = D V(f W – f A)
1/D V = 1/D W + 1/D A = 1/k WAZ W + 1/k AAZ A
The groups 1/D A and 1/D W are effectively resistances that add to give the total
resistance 1/D V. It can be shown that
Thus,
D V = k OWAZ W = k OAAZ A
k OW/k OA = Z A/Z w = K AW
as before.
The net volatilization rate, D V(f W – f A), can be viewed as the algebraic sum of
an upward volatilization rate, D Vf W, and a downward absorption rate, D Vf A.
Expressions for intermedia diffusion become very simple and transparent when
written in fugacity form. The selection of one of two possible overall MTCs is
avoided. Each conductivity is expressed in identical units containing its own Z value.
The conductivities add reciprocally, as do electrical conductivities in series.
7.8 MEASURING TRANSPORT D VALUES
Measuring nondiffusive D values is, in principle, simply a matter of measuring
Z and G, the latter usually being the problem. Flows of air, water, particulate matter,
rain, and food can be estimated directly. The more difficult situations involve estimations
of the rate of deposition of aerosols and sedimenting particles in the water
column. The obvious approach is to place a bucket, tray, or a sticky surface at the
depositing surface and measure the amount collected. This method can be criticized,
because the presence of the bucket alters the hydrodynamic regime and thus the
settling rate. This problem is acute when estimating aerosol deposition rates on
foliage in a field or forest where the boundary layer is highly disturbed. Measure-