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

Figure 7.10 Four-compartment Level III diagram.
to some extent on chemical transport properties such as diffusivities. The variation
in diffusivity is usually small compared to the variation in Z values, thus the use of
chemical-specific diffusivities is justified only for the most accurate simulations.
Most of these transport parameters can be expressed as velocities.
The values given vary considerably from place to place and time to time. If the
aim is to simulate conditions in a specific region, appropriate transport rate parameters
for that region can be sought.
The air-side and water-side mass transfer coefficients k VA and k VW have been
measured in wind-wave tanks and in lakes as a function of wind speed. Schwarzenbach
et al. (1993) have reviewed these correlations. The following correlations are
suggested by Mackay and Yuen (1983). Note that units are m/s.
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k VA = 10 –3 + 0.0462 U * (Sc A) –0.67 m/s
k VW = 10 –6 + 0.0034 U * (Sc W) –0.5 m/s
U * = 0.01(6.1 + 0.63 U 10) 0.5 U 10 m/s
where U * is the friction velocity, which characterizes the drag of the wind on the
water surface. Sc A is the Schmidt number in air and ranges from 0.6 for water to
about 2.5, and Sc W applies to the water phase and is generally about 1000. U 10 is
the wind velocity at 10 m height.
Changing the velocity units to m/h, substituting typical values for the Schmidt
number, and taking into account other studies, the following correlations are suggested.