10. Lipids in Water-Surface MicroJayers and Foams
243
diameter wire, with ~60% open space) mounted in a 0.75 x 0.60-m aluminum
frame. During the sampling operation, the screen was lowered vertically to the
proximity of the water, then reoriented horizontally to enable contact with the
surface film, thus entrapping it between the wires of the mesh. The screen was
then immediately returned to its vertical position, and the liquid was drained into
an appropriate collection bottle. Several variations of the original metal screen
were used by other workers, including a stainless-steel model used by Sieburth
(1965) and Williams et ai. (1986). Duce et al. (1972) and Pojasek and Zajicek
(1978) used a polyethylene screen, particularly suitable for the analyses of metals
in sea-surface micro1ayers. This later screen material, however, reportedly
changes the surface potential of the surface water and therefore may not be an
adequate sampling device (MacIntyre, 1974).
Screen samplers are simple and inexpensive, but their use is limited due to the
time and effort involved in obtaining a reasonable volume of water. Moreover,
there are concerns about whether a thin, unmixed, and uncontaminated layer is
effectively sampled with these devices (Liss, 1975). To solve these problems, two
methods based on completely different operation principles were introduced: the
rotating drum (Hardy et ai., 1988; Harvey, 1966) and the freezing probe (Hamilton and Clifton, 1979).
Harvey (1966) pioneered the construction of a series of continuous samplers of
different materials (steel, ceramic, polyvinyl chloride [PVC]) based on the principle of a rotating hydrophilic drum. The first rotating micro layer collector
(Harvey, 1966) consisted of a ceramic-coated stainless-steel drum (0.38-m diameter; 0.60 m long). The drum collected a microlayer (60-100 f.Lm thick) that
adhered to its surface, which was then removed by a neoprene wiper and finally
collected into a plastic cup. This rotating drum collected about 300 ml of water per
minute. The main problem with this sampler is that it only works effectively under
calm conditions. Most earlier versions of the rotating samplers were coated with
relatively hydrophilic materials, such as ceramic (Harvey, 1966), PVC (Brockmann et ai., 1976), and glass (Carlson et ai., 1988), which obviously were not
ideal for collecting lipids. Furthermore, the use of neoprene and plastic materials
for the collection of lipids and lipophilic substances is always questionable due to
a great potential for introducing contaminants. Using the same basic principle of
the rotating drum, Hardy et ai. (1988) developed a new large-volume hydrophobic
sampler coated with Teflon (polytetrafluoroethylene [PTFE]). The PTFE rotating
drum efficiently sampled the biogenic lipids and anthropogenic contaminants
from the top 34 f.Lm of the surface microlayer (Hardy et ai., 1988).
Hamilton and Clifton (1979) developed the unorthodox freezing probe technique to sample the surface microlayer of estuarine and coastal waters. This
device consists of a polymethylmethacrylate (acrylic plastic) disk (0.25-m diameter), encased in a thin (0.1 mm) PVC membrane. The upper surface of the disk is
prechilled in liquid N2 and attached to a plastic rod with freezing water. The
freezing probe is brought into contact with the water surface, which immediately
freezes to a depth of about 1,000 f.Lm. The frozen surface micro layer can be
detached from the PVC membrane, stored, and later sectioned with a sledge
243
diameter wire, with ~60% open space) mounted in a 0.75 x 0.60-m aluminum
frame. During the sampling operation, the screen was lowered vertically to the
proximity of the water, then reoriented horizontally to enable contact with the
surface film, thus entrapping it between the wires of the mesh. The screen was
then immediately returned to its vertical position, and the liquid was drained into
an appropriate collection bottle. Several variations of the original metal screen
were used by other workers, including a stainless-steel model used by Sieburth
(1965) and Williams et ai. (1986). Duce et al. (1972) and Pojasek and Zajicek
(1978) used a polyethylene screen, particularly suitable for the analyses of metals
in sea-surface micro1ayers. This later screen material, however, reportedly
changes the surface potential of the surface water and therefore may not be an
adequate sampling device (MacIntyre, 1974).
Screen samplers are simple and inexpensive, but their use is limited due to the
time and effort involved in obtaining a reasonable volume of water. Moreover,
there are concerns about whether a thin, unmixed, and uncontaminated layer is
effectively sampled with these devices (Liss, 1975). To solve these problems, two
methods based on completely different operation principles were introduced: the
rotating drum (Hardy et ai., 1988; Harvey, 1966) and the freezing probe (Hamilton and Clifton, 1979).
Harvey (1966) pioneered the construction of a series of continuous samplers of
different materials (steel, ceramic, polyvinyl chloride [PVC]) based on the principle of a rotating hydrophilic drum. The first rotating micro layer collector
(Harvey, 1966) consisted of a ceramic-coated stainless-steel drum (0.38-m diameter; 0.60 m long). The drum collected a microlayer (60-100 f.Lm thick) that
adhered to its surface, which was then removed by a neoprene wiper and finally
collected into a plastic cup. This rotating drum collected about 300 ml of water per
minute. The main problem with this sampler is that it only works effectively under
calm conditions. Most earlier versions of the rotating samplers were coated with
relatively hydrophilic materials, such as ceramic (Harvey, 1966), PVC (Brockmann et ai., 1976), and glass (Carlson et ai., 1988), which obviously were not
ideal for collecting lipids. Furthermore, the use of neoprene and plastic materials
for the collection of lipids and lipophilic substances is always questionable due to
a great potential for introducing contaminants. Using the same basic principle of
the rotating drum, Hardy et ai. (1988) developed a new large-volume hydrophobic
sampler coated with Teflon (polytetrafluoroethylene [PTFE]). The PTFE rotating
drum efficiently sampled the biogenic lipids and anthropogenic contaminants
from the top 34 f.Lm of the surface microlayer (Hardy et ai., 1988).
Hamilton and Clifton (1979) developed the unorthodox freezing probe technique to sample the surface microlayer of estuarine and coastal waters. This
device consists of a polymethylmethacrylate (acrylic plastic) disk (0.25-m diameter), encased in a thin (0.1 mm) PVC membrane. The upper surface of the disk is
prechilled in liquid N2 and attached to a plastic rod with freezing water. The
freezing probe is brought into contact with the water surface, which immediately
freezes to a depth of about 1,000 f.Lm. The frozen surface micro layer can be
detached from the PVC membrane, stored, and later sectioned with a sledge