Gschwend%20thesis.pdf

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Three known incidents of hydrocarbon spills occurred in the region
during the study period. In January, 1977 a barge carrying Bouchard no. 2
fuel oil spilled part of its cargo at the head of Buzzards Bay (ca. 16
km. from CD). Some time later.. ice ~ laden with some of this oil, was
observed in the waters near CD. Also, in March, 1978 a large
gasoline spill occurred near Block Island in Long Island Sound (ca. 80
km. from CD). Finall~ in April of 1978, a second barge spilled
oil near the west end of the Cape Cod Canal (ca. l6 km. from CD). Only
the first of these accidents could be clearly related to the level of
volatile organic compounds at CD (see below and Schwarzenbach et al.,
1978) .
Variations of Volatile Organic Compounds
Alkylated Benzenes. The seasonal changes in the concentrations of
the C2- and C3-alkylated benzenes are shown in figures 3-8 and 3-9. All
of these compounds, except ethyl benzene (see later discussion), closely
covary. The C2-benzenes usually appear at an isomer ratio of ethyl
benzene: m + p-xylenes: o-xylene = 1: 2: I. These isomers were always more
abundant than the C3-benzenes. Still more highly substituted benzenes
were also observed at lower concentrations and their temporal distribu-
tions parallel those of the lower homologues.
In order to demonstrate the nature of a source of the alkylated
benzenes, one of them, o-xylene (or mOLe properly, I, 2-dimethyl benzene)
has been replotted including three samples taken the three days immedi~
ately following the Memorial Day weekend (May 27-29, 1978) (figure 3-l0).
One can see a tremendous fluctuation in the concentration of this compound
at this time over a very short time interval. Indeed, the sample
following the weekend shows the highest concentration found all year.