Chemistry Reference
In-Depth Information
Fig. 4.
The variation of static surface elasticity (H
o
) with surface pressure (3) for
air-seawater interfacial films with compositions corresponding to the F1 extracts
and mass spectra of Figure 3. The highest elasticities at a given film surface pres-
sure were observed for films dominated by lipid surfactants; lowest elasticities
were observed for films dominated by polyoxy surfactants
4. Summary
Surface microlayer films sampled in both coastal and oligotrophic waters
exhibited variable enrichments of surface-active compounds, including lip-
ids, biological and synthetic polymers, and humic materials. The relative
proportions of these compound classes in the films were shown to influ-
ence the overall film elasticity. Although the elasticity measurements in
this study were carried out on surface films reconstructed from artificially
fractionated film materials, the observed elastic moduli were very similar
to those reported for spontaneous films formed from unfractionated sea-
water (Barger and Klusty, cited in Peltzer et al. 1992); the latter exhibited
maximum elastic moduli of ~26 mN m
-1
at surface pressures <10 mN m
-1
.
In some of the few dynamic elasticity estimates made
in situ
, Lombardini
et al. (1989) reported elasticities generally ranging from 10 to 25 mN m
-1
.
They also suggested that variations in elasticity were caused by varying
proportions of water-soluble and water-insoluble surfactants, based on pa-
rametric fits to a wave damping model. Thus, it is likely that elasticity
variations are coupled to compositional differences in films
in situ
.
