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m/z
value, characteristic of pyrolysis spectra of coloured humic materials
(Little and Jacobus 1985). This background decreased rapidly and other
individual components became prominent in the spectra with increasing
distance offshore.
Fig. 2
. Variations in surface microlayer chemical composition as shown by DEI-
MS spectra for three microlayers (SepPak eluates) collected along a cruise track
from Delaware Bay south-eastward across the continental shelf. Spectral intensi-
ties are normalised to the most abundant
m/z
intensity. The spectrum of the sample
in the upper panel, which was collected within the Delaware River plume, is
dominated by the presence of humic compounds that characteristically pyrolyse to
produce mass fragments at every
m/z
value. The contribution from humic materi-
als decreases markedly with distance from the estuary
Qualitatively, the Middle Atlantic Bight samples were very similar to
those collected in the California Bight. The predominant components were
the same in both locales, suggesting that a limited number of compound
classes are dominant in microlayer films, but present in varying propor-
tions. The specific mixtures of surfactants in the microlayers sampled in
this study strongly influenced air-sea interfacial quasi-static elasticity. Pre-
