35
Properties of Pesticides and Contaminants
relatively high Henry’s constants and their nonideal aqueous solutions. This
phenomenon was also observed during the Exxon Valdez oil spill in Prince
William Sound, Alaska, in 1989. In addition to volatilization from the ocean
water column, signifcant volatilization also occurred from the crude oil
deposited on the beaches. Workers hired to clean the beaches experienced
long-lasting health effects due to their exposure to the volatile components of
the crude, even though they wore protective equipment (Ott, 2005).
This phenomenon is further illustrated by the volatilization of dimethylmercury from ocean water and the deposition of the mono-methyl cation in rainwater and fogwater along the California coast (see Chapter 7).
Dimethylmercury has a high Henry’s constant driving the fux to the air as
ocean water hits the coastline. This explains in part the enrichment of mercury
along the Pacifc Ocean coastline and in air along the coast. Volatilization of
organic compounds from water is usually described by the two-flm model
(Lewis and Whitman, 1924), which assumes that all of the resistance to volatilization is in thin flms of water and air at the interface between the phases.
The resistances of these flms are assumed to be in series and, therefore, additive. Liquid- and gas-phase mass transfer coeffcients are related to chemical
properties and fuid fow conditions:
k = D /a , k = D /a
l
l
l
g
g
g
(3.10)
The mass transfer coeffcients are k l and k g for liquid phase and gas phase,
respectively (cm/sec), D l and D g are the corresponding diffusion coeffcients
(cm 2 /sec), and a l and a g are the hypothetical thicknesses of the liquid flm
and gas flm, respectively, adjacent to the interface (cm) (Figure 3.5).
In addition to the two flms, other factors that affect volatilization of organic
compounds from water are water temperature and wind speed, leading to
turbulence in air and water. The hypothetical flm thicknesses are assumed
to be a function of the extent of turbulent kinetic energy and subsequent
FIGURE 3.5
Schematic representation of the two-flm model for the fux of organic compounds from water.
Properties of Pesticides and Contaminants
relatively high Henry’s constants and their nonideal aqueous solutions. This
phenomenon was also observed during the Exxon Valdez oil spill in Prince
William Sound, Alaska, in 1989. In addition to volatilization from the ocean
water column, signifcant volatilization also occurred from the crude oil
deposited on the beaches. Workers hired to clean the beaches experienced
long-lasting health effects due to their exposure to the volatile components of
the crude, even though they wore protective equipment (Ott, 2005).
This phenomenon is further illustrated by the volatilization of dimethylmercury from ocean water and the deposition of the mono-methyl cation in rainwater and fogwater along the California coast (see Chapter 7).
Dimethylmercury has a high Henry’s constant driving the fux to the air as
ocean water hits the coastline. This explains in part the enrichment of mercury
along the Pacifc Ocean coastline and in air along the coast. Volatilization of
organic compounds from water is usually described by the two-flm model
(Lewis and Whitman, 1924), which assumes that all of the resistance to volatilization is in thin flms of water and air at the interface between the phases.
The resistances of these flms are assumed to be in series and, therefore, additive. Liquid- and gas-phase mass transfer coeffcients are related to chemical
properties and fuid fow conditions:
k = D /a , k = D /a
l
l
l
g
g
g
(3.10)
The mass transfer coeffcients are k l and k g for liquid phase and gas phase,
respectively (cm/sec), D l and D g are the corresponding diffusion coeffcients
(cm 2 /sec), and a l and a g are the hypothetical thicknesses of the liquid flm
and gas flm, respectively, adjacent to the interface (cm) (Figure 3.5).
In addition to the two flms, other factors that affect volatilization of organic
compounds from water are water temperature and wind speed, leading to
turbulence in air and water. The hypothetical flm thicknesses are assumed
to be a function of the extent of turbulent kinetic energy and subsequent
FIGURE 3.5
Schematic representation of the two-flm model for the fux of organic compounds from water.