Gschwend%20thesis.pdf

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while at other times they were higher. Similarly, concentrations did not
always increase in the samples taken closer to Woods Hole harbor. The
inhomogeneity of o-xylene levels was much greater than can be explained by
the analytical error (I 10%). This variability is unexpected for a domin-
antly atmospheric source, assuming that the rate of removal of o-xylene
from surface seawater was similar at these stations.
Rain
Two rain samples were analyzed for the C2- and C3-benzenes (Table 4-1).
The C3-benzenes were present at very low concentrations, and consequently,
only the most abundant isomer, 1,2, 4-trimethyl benzene, is reported. The
2 samples contained very similar levels of C2-benzenes. The spring sample
had very much lower levels of C2-benzenes than seawater át that time, while
the fall rain sample had concentrations comparable to those of seawater.
If the rain was near equilibrium with respect to air concentrations of
these C2- and C3-benzenes, an estimate of the atmospheric concentrations
of these aromatic compounds may be calculated from the rain results.
These air concentrations may then be used to infer the direction of
air-sea exchange for the C2- and C3-benzenes at the time of rain collection.
From this approach, it appears that seawater was degassing the C2- and C3-
benzenes in June, but was near equilibrium in November.
These estimates of the atmospheric concentrations of the C2- and C3-
benzenes probably reflect the levels in air present during the entire rain
period. If these compounds occur as vapors, rainfall cannot efficiently
scrub the atmosphere of them since the partition coefficients (0.l-0.4)
are so low. Thus comparison of these estimated aromatic
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