246
G.E. Napolitano and D.S. Cicerone
< 1.4/-Lm (Stobbe and Peschel, 1997; Metzik et aI., 1973; McCafferty et aI., 1970).
The reduction of the dielectric constant of the water in thin films affects its
characteristics as a solvent and should result in an increment of the solubility of
lipids and other organic hydrophobic substances. As E decreases, the intermolecular forces in the liquid water decrease and so does the energy needed for the
organic molecules to "insert" themselves into water. To the best of our knowledge,
the changes in the dielectric constant of the water-surface microlayer, the associated changes of the solubility of hydrophobic organic matter, and the resulting
implications for the assessment of the biogeochemistry of natural waters have
been overlooked.
Low aqueous solubility (hydrophobic character), a low relative density (0.80.9), low vapor pressure, and the presence of natural and anthropogenic surfactants stabilize organic material in the surface microlayer. Studies of the behavior
of natural films in the micro layers have shown that, at low lipid densities, the lipid
layers resemble a two-dimensional gas, in which loosely arranged molecules
move freely on the water surface (Gaines, 1966). At higher lipid concentrations,
the film can be in the liquid or solid state, depending on molecular interactions
leading to cohesive forces between molecules. Straight-chain saturated fatty acids
in microlayers manifest strong hydrophobic interactions because of the overlap of
the lineal hydrocarbon chains, which produces a tightly packed film. Unsaturated
fatty acids, however, produce less cohesive films even at relatively high concentrations, because of the bends in the hydrocarbon chain produced by the double
bonds (Norkrans, 1980).
The processes that influence the distribution of material in the surface microlayer described by Garret (1972, 1967) and Jarvis (1967) are summarized in
Figure 10.3. Bubble production is a common natural phenomena at the surface
water of marine and freshwater environments and a critical process in surfacelayer chemistry. Bubbles may be caused by the activity of organisms, breaking
waves, and/or turbulent flows. They serve as a two-way transport system, removing salt nuclei, surface active material, and particles into the deeper water as well
as collecting material from the near-surface layers (air phase) into the surface film
(Blanchard, 1968, 1964, 1963; Baylor et aI., 1962). At the water surface, the
bubbles may burst, ejecting aerosol droplets into the air (Lai and Shemdin, 1974;
Blanchard and Syzdek, 1972; Paterson and Spillane, 1969). In the process of
production of aerosols, some fractionation of salts and the preferential removal of
some fractions of the organic matter by production of aerosols and by evaporation
are well documented (Volz, 1972; Blanchard, 1964; Wilson, 1959). Transport by
bubbles is more extensively described in the chemical engineering literature (Karger and DeVivo, 1968; Dorman and Lemlich, 1965).
Wind and wave action contribute to the equilibration of atmospheric gases into
the surface layer, enhancing the rates of evaporation and dissolution altered by
surface active compounds in the surface microlayer (Wu, 1974; Mallinger and
Mickelson, 1973; Healy and La Mer, 1964; Garrett and Bultman, 1963). Wind and
waves also contribute to the formation of bubbles and the cycling of particles
through the surface micro layer. Accumulation of bacteria on the surfaces of
bubbles, with the subsequent transfer to the surface film, has been demonstrated
G.E. Napolitano and D.S. Cicerone
< 1.4/-Lm (Stobbe and Peschel, 1997; Metzik et aI., 1973; McCafferty et aI., 1970).
The reduction of the dielectric constant of the water in thin films affects its
characteristics as a solvent and should result in an increment of the solubility of
lipids and other organic hydrophobic substances. As E decreases, the intermolecular forces in the liquid water decrease and so does the energy needed for the
organic molecules to "insert" themselves into water. To the best of our knowledge,
the changes in the dielectric constant of the water-surface microlayer, the associated changes of the solubility of hydrophobic organic matter, and the resulting
implications for the assessment of the biogeochemistry of natural waters have
been overlooked.
Low aqueous solubility (hydrophobic character), a low relative density (0.80.9), low vapor pressure, and the presence of natural and anthropogenic surfactants stabilize organic material in the surface microlayer. Studies of the behavior
of natural films in the micro layers have shown that, at low lipid densities, the lipid
layers resemble a two-dimensional gas, in which loosely arranged molecules
move freely on the water surface (Gaines, 1966). At higher lipid concentrations,
the film can be in the liquid or solid state, depending on molecular interactions
leading to cohesive forces between molecules. Straight-chain saturated fatty acids
in microlayers manifest strong hydrophobic interactions because of the overlap of
the lineal hydrocarbon chains, which produces a tightly packed film. Unsaturated
fatty acids, however, produce less cohesive films even at relatively high concentrations, because of the bends in the hydrocarbon chain produced by the double
bonds (Norkrans, 1980).
The processes that influence the distribution of material in the surface microlayer described by Garret (1972, 1967) and Jarvis (1967) are summarized in
Figure 10.3. Bubble production is a common natural phenomena at the surface
water of marine and freshwater environments and a critical process in surfacelayer chemistry. Bubbles may be caused by the activity of organisms, breaking
waves, and/or turbulent flows. They serve as a two-way transport system, removing salt nuclei, surface active material, and particles into the deeper water as well
as collecting material from the near-surface layers (air phase) into the surface film
(Blanchard, 1968, 1964, 1963; Baylor et aI., 1962). At the water surface, the
bubbles may burst, ejecting aerosol droplets into the air (Lai and Shemdin, 1974;
Blanchard and Syzdek, 1972; Paterson and Spillane, 1969). In the process of
production of aerosols, some fractionation of salts and the preferential removal of
some fractions of the organic matter by production of aerosols and by evaporation
are well documented (Volz, 1972; Blanchard, 1964; Wilson, 1959). Transport by
bubbles is more extensively described in the chemical engineering literature (Karger and DeVivo, 1968; Dorman and Lemlich, 1965).
Wind and wave action contribute to the equilibration of atmospheric gases into
the surface layer, enhancing the rates of evaporation and dissolution altered by
surface active compounds in the surface microlayer (Wu, 1974; Mallinger and
Mickelson, 1973; Healy and La Mer, 1964; Garrett and Bultman, 1963). Wind and
waves also contribute to the formation of bubbles and the cycling of particles
through the surface micro layer. Accumulation of bacteria on the surfaces of
bubbles, with the subsequent transfer to the surface film, has been demonstrated