Environmental Engineering Reference
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distance upgradient of the well; DNAPL has not been
detected in this well. Between 2000 and 2007 concentrations
of benzene, toluene, and naphthalene decreased from their
highest measured concentration by 80%, 99%, and 68%,
respectively.
During this time period, concentrations of the compounds
did not decrease steadily, but rather fluctuated from low to
high back to low concentrations. An annual, seasonal varia-
tion in concentrations of these dissolved-phase contaminants
was observed. For example, in 2001, 2003, and 2005, the
lowest concentrations of benzene, toluene, and naphthalene
were observed during the spring-summer sampling events,
when transpiration increases to maximum and groundwater
uptake potential increases to highest, and the highest
concentrations were observed during the fall
winter sam-
pling months.
Fig. 13.4
Measurement of sap flow in a 7-year old hybrid poplar tree
using the heat-balance method (Photograph by author).
Fig. 13.5
Concentrations of
benzene (
●
), toluene (
○
),
▾
), and dissolved
oxygen (DO) (
□
) in monitoring
wells A3-T1 (
top
) and CM-03A
(
bottom
), 2000-2007, at the
former MGP site, Charleston, SC.
Vertical dashed lines represent
calendar year divisions.
naphthalene (
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