10. Lipids in Water-Surface Microlayers and Foams
249
origin (Marty and Choiniere, 1979) and were typical of the cuticular lipids of
terrestrial vegetation (Johnson and Calder, 1973).
In a similar study of a wind-generated foam in a remote high-latitude Andean
Lake (Laguna Lejia, Antofagasta, Chile), it was reported that lipids consisted of
hydrocarbons and a series of not-well-defined acyl esters, which included phospholipids (Simoneit et aI., 1980). The quantitation of the total hydrocarbon content in the foam of this apparently pristine environment is of particular interest
because it may represent baseline levels or biogenic constituents. Although the
total lipid content of the foam was ~ 2 mg . g - 1 of dry foam, hydrocarbons
accounted for ~ 1.4% of the total lipids. The hydrocarbon constituents of the foam
were mainly n-alkanes, ranging from n-C15 to n-C33 with maxima at C18 and
C29 and a strong odd-to-even carbon preference index (CPI, % hydrocarbons
containing an odd number of carbon atoms/% hydrocarbons containing an even
number of carbon atoms) of 3.5. This hydrocarbon profile is consistent with a
biogenic origin and is thought to derive, in part, from vascular plant waxes
(Simoneit et aI., 1980). Other hydrocarbons present in the foam were 7- and
8-methylheptadecane, which has been shown to be a major component of cyanobacteria species (Han et aI., 1968). The analysis of the water-surface microlayer of
Lake Sisjon, an unpolluted reservoir in Sweden, showed that triacylglycerols and
free fatty acids, but not hydrocarbons, were the major lipid components of the
hydrophobic organic matter (Larsson et aI., 1974).
Studies of the fractionation of organic matter and other chemicals between the
surface and the subsurface waters of large water falls are also of interest due to the
magnitude of gas injection into the water flow that occurs at these sites. For
example, the analysis of trace metals and lipids in the water and foam formations below Niagara Falls was of particular environmental concern, due to the
large inflow of municipal and industrial waste into the system (Warry and Chan,
1981). Concentrations of metals and various lipid classes were measured in the
foam and the subsurface water just below Niagara Falls (Johnson et aI., 1989).
The concentrations of total particulate (50 J..Lg . L - 1) and total dissolved lipids
(200 J..Lg . L -1) in Niagara Falls were similar to those reported in marine coastal
environments (Parrish, 1987). Foams presented a substantial enrichment of lipids
with respect to the bulk water, showing concentrations > 12,000 J..Lg. L - 1.
The foam lipids consisted of (in decreasing order of concentrations) "acetone
mobile polar lipids" (which include plant pigments and other polar compounds),
sterols, triacylglycerols, hydrocarbons, free fatty acids, phospholipids, and minor
amounts of wax esters, methyl esters, ketones, and fatty alcohols. Although hydrocarbons were not analyzed in detail by gas chromatography, their relatively
high concentration in the foam (~11 % of the total lipids) suggested a significant
contribution from petroleum sources. Regardless of the concentration of a particular lipid class in the bulk water, its enrichment factor in the foam (concentration of
a lipid in the foam divided by its concentration in the subsurface water) depended
on the polarity of the compounds; less polar lipids (hydrocarbons, wax esters, and
triacylglycerols) were enriched in foam by a factor of <25, whereas more polar
lipid classes (free fatty acids, sterols, and phospholipids) were enriched by a factor
249
origin (Marty and Choiniere, 1979) and were typical of the cuticular lipids of
terrestrial vegetation (Johnson and Calder, 1973).
In a similar study of a wind-generated foam in a remote high-latitude Andean
Lake (Laguna Lejia, Antofagasta, Chile), it was reported that lipids consisted of
hydrocarbons and a series of not-well-defined acyl esters, which included phospholipids (Simoneit et aI., 1980). The quantitation of the total hydrocarbon content in the foam of this apparently pristine environment is of particular interest
because it may represent baseline levels or biogenic constituents. Although the
total lipid content of the foam was ~ 2 mg . g - 1 of dry foam, hydrocarbons
accounted for ~ 1.4% of the total lipids. The hydrocarbon constituents of the foam
were mainly n-alkanes, ranging from n-C15 to n-C33 with maxima at C18 and
C29 and a strong odd-to-even carbon preference index (CPI, % hydrocarbons
containing an odd number of carbon atoms/% hydrocarbons containing an even
number of carbon atoms) of 3.5. This hydrocarbon profile is consistent with a
biogenic origin and is thought to derive, in part, from vascular plant waxes
(Simoneit et aI., 1980). Other hydrocarbons present in the foam were 7- and
8-methylheptadecane, which has been shown to be a major component of cyanobacteria species (Han et aI., 1968). The analysis of the water-surface microlayer of
Lake Sisjon, an unpolluted reservoir in Sweden, showed that triacylglycerols and
free fatty acids, but not hydrocarbons, were the major lipid components of the
hydrophobic organic matter (Larsson et aI., 1974).
Studies of the fractionation of organic matter and other chemicals between the
surface and the subsurface waters of large water falls are also of interest due to the
magnitude of gas injection into the water flow that occurs at these sites. For
example, the analysis of trace metals and lipids in the water and foam formations below Niagara Falls was of particular environmental concern, due to the
large inflow of municipal and industrial waste into the system (Warry and Chan,
1981). Concentrations of metals and various lipid classes were measured in the
foam and the subsurface water just below Niagara Falls (Johnson et aI., 1989).
The concentrations of total particulate (50 J..Lg . L - 1) and total dissolved lipids
(200 J..Lg . L -1) in Niagara Falls were similar to those reported in marine coastal
environments (Parrish, 1987). Foams presented a substantial enrichment of lipids
with respect to the bulk water, showing concentrations > 12,000 J..Lg. L - 1.
The foam lipids consisted of (in decreasing order of concentrations) "acetone
mobile polar lipids" (which include plant pigments and other polar compounds),
sterols, triacylglycerols, hydrocarbons, free fatty acids, phospholipids, and minor
amounts of wax esters, methyl esters, ketones, and fatty alcohols. Although hydrocarbons were not analyzed in detail by gas chromatography, their relatively
high concentration in the foam (~11 % of the total lipids) suggested a significant
contribution from petroleum sources. Regardless of the concentration of a particular lipid class in the bulk water, its enrichment factor in the foam (concentration of
a lipid in the foam divided by its concentration in the subsurface water) depended
on the polarity of the compounds; less polar lipids (hydrocarbons, wax esters, and
triacylglycerols) were enriched in foam by a factor of <25, whereas more polar
lipid classes (free fatty acids, sterols, and phospholipids) were enriched by a factor