Gschwend%20thesis.pdf

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The Quashnet River and Sippewissett Marsh (low tide) were sampled in
August, 1977 and July, 1977, respectively. Both samples showed lower levels
of C2~ and C3~benzenes than seawater collected on the same day (Table 4-2).
These observations, together with those on the Oyster Pond samples, suggest
that runoff in the summer dilutes seawater with respect to these aromatic
hydrocarbons.
Air Measurements.
Air samples in August and September, 1978 were analyzed for C2- and C3-
benzenes. Air at CD was pumped through a 5-liter round bottom flask for
is minutes at a rate of about 2 liter/min. After this flushing, the air
was rerouted through a charcoal trap for is min. Repeating this sequence
4 more times allowed the analysis of 25 liters of air.
Figure 4-7 shows the result of a midweek air analysis. Standards
(added to the charcoal trap just prior to extraction and indicated in the
figure by dots) indicate the 1. 6 ng/l~air concentration level. First, one
can see that the concentrations of the alkylated benzenes were quite low.
Moreover, a reBtrip of the same air onto a fresh charcoal trap showed
significant levels of these compounds relative to the first strip. This
suggests that 15 min. for the first strip was insufficient for complete
recovery from 5 liters; and therefore, the concentrations of these compounds
in air may be underestimated by these analyses. Finally, an analysis of
exhaustively prestripped air is shown and reveals that the procedural blank
was very good.
Table 4-3 shows the observed levels for o-xylene in air. Highest
values were found on Saturday and Monday of the Labor Day holiday weekend"