Gschwend%20thesis.pdf

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Mass plots for ro/e l09 in the CI-CH4 GCMS analyses showed that,
while only one "octatriene" was found at station 3, additional isomers
had appeared in the surface seawater at station 6. Mass spectra
showed that these compounds were very closely related.
Pentadecane was also found in the upwelling region near Peru
(figurè 2-7). Surface samples contained the highest concentrations
except at the most nearshore station. The 20-m and 100-m samples at
the most offshore station showed atypically high pentadecane concen-
trations.
A comparison of filtered and unfiltered 5- and 20-m samples from
the Peru upwelling region showed 2 samples with 50-60% losses of
pentadecane and i sample with no significant difference on filtering
(Appendix I, Table 1-3). A filtering experiment done on coastal
seawater from Vineyard Sound also showed about one-half removal of
pentadecane on filtering. These losses may be due to a particle
association of a significant fraction of this hydrocarbon.
A particle association of pentadecane may also explain the high
variability observed for this compound in the Atlantic surface
seawater samples (Table 2-1). Replicate samples from the same depth
(e.g., Sargasso Seal lO m and w. Eq. Atl. 24/7 m) showed very poor
reproducibility. Gardner (1977) has found that a large fraction of
the particulate matter in a seawater sample will settle below the
outlet of a 30-liter Niskin. Particle concentrations may be 2-20 times
higher in the dregs of the 30 liter Niskin than in the remainder of
the water. Thus, factors such as the time of standing of the sampler
after retrieval and the sequence of subsampling may have affected the
particle distributions in the subsamples of this work, and as a
resul t, the pentadecane concentrations may have also varied.