Applications of Equilibrium Thermodynamics - Elements of Environmental Engineering: Thermodynamics and Kinetics - page 143

high concentrations of polyaromatic hydrocarbons and chlorinated pesticides (Capel
et al., 1991; Glotfelty, Seiber, and Liljedahl, 1987).

4.2.3 D RY D EPOSITION OF A EROSOL -B OUND P OLLUTANTS
The transfer of aerosol-bound pollutants directly from air to water is called dry
deposition. The deposition flux is parameterized as

J Dry ( P ) = V d · C i a , (4.47)

where V d is the deposition velocity (cm/s). Typical deposition velocities are given in
Table 4.8. V d is composed of three resistance terms:

1
r al +

1
r bl +

1
r s ,

V d =

where r al is the aerodynamic layer resistance, r bl is the boundary layer resistance,
and r s is the surface resistance. V d is affected by environmental factors, such as type
of aerosol, particle size, wind velocity, surface roughness, atmospheric stability, and
temperature. An excellent summary is provided by Davidson and Wu (1992).

TABLE 4.8
Typical Dry Deposition Velocities for Gases
and Aerosols

Compound Range of V d (cm/s)

SO 2 (g) 0.3-1.6

N ox (g) 0.01-0.5

HCl(g) 0.6-0.8

O 3 (g) 0.01-1.5

SO 2 −
4

0.01-1.2

NH 4

0.05-2.0

Cl −

1-5

Pb 0.1-1.0

Hg 0

0.02-0.11

Ca, Mg, Fe, Mn 0.3-3.0

Al, Mn, V 0.03-3.0

PCB, DDT 0.19-1.0

Fine particles (1 μ m) 0.1-1.2

Source: From Davidson, C.I. and Wu, Y.L. 1992. Acid
Precipitation—Sources, Deposition and Canopy Inter-
action , Vol. 3, pp. 103-216. New York: Springer;
Eisenreich, S.J., Looney, B.B., and Thornton, J.D.
Environmental Science andTechnology 5, 30-38, 1981.