Gschwend%20thesis.pdf

-117-
with 0.29 for o-xylene and 0.076 for heptanal) of this compound indicates
that it might not be stripped effectively; filtering experiments suggest
that about half of the naphthalene can be removed by a glass fiber filter
from seawater. Consequently, it is likely that the naphthalenes occur as
both dissolved and particulate species in seawater, and neither of these forms
are readily purged from water ~amples.
Alkanes. The temporal variations Of the Cl3 to Cl7 n-alkanes and of
pristane (2,6, 10, 14-tetramethyl-pentadecane) are shown in figure 3-16.
The levels were high in March, 1977 as a result of the oil spill. This
interpretation is supported by an odd-even carbon preference index ("CPI")
calculated as nCl5 + nCI7/nCI4+ nCl6 which at this time was 1.2 (figure
3-17). Pentadecane showed two maxima in the sumer of 1977 and another
beginning in the summer of 1978. Schwarzenbach et al. (1978) attributed
this to production by the extensive benthic algal growth in the area.
A biological source was also sugges.ted by the high "CPI"~. Heptadecane
also showed two concentration peaks in the summer of 1977, the second of
which corresponds to the s.econd pentadecane spike. Again, the high "CPI"
suggests a biological source of this hydrocarbon for both of these
concentration spikes. Benthic algae in this region are known to be rich
in these compounds (Clark and Blumer, 1967; Youngblood et al., 1971;
Youngblood and Blumer, 1973). The July peak demonstrated a nCl7/pristane
ratio of about 120 suggesting a green algal source (Clark and Blumer,
1969). The late summer peak in the concentrations of nCl5 and nCl7 may
reflect the onset of senescence in some of the seaweeds, or be due to
other physiological changes. As mentioned earlier, large washups of
seagrass and macroalgae were observed soon after these peak levels were
observed.