Handbook of Solvents - George Wypych - ChemTech - Ventech!

1612 Hanadi S. Rifai, Charles J. Newell, Todd H. Wiedemeier
Figure 23.1.14. BTEX and electron acceptors, 1995, Plattsburg Air
Force Base, New York. [From T.H. Wiedemeier, H. S. Rifai, C. J.
Newell and J.T. Wilson, Natural Attenuation of Fuels and Chlorinated
Solvents in the Subsurface, after reference 88. Copyright ©
1999 John Wiley & Sons, Inc. Reprinted by permission of John
Wiley & Sons, Inc.]
Figure 23.1.15. BTEX and metabolic by-products, 1995, Plattsburg
Air Force Base, New York. [From T.H. Wiedemeier, H. S. Rifai, C.
J. Newell and J.T. Wilson, Natural Attenuation of Fuels and Chlorinated
Solvents in the Subsurface, after reference 88. Copyright
© 1999 John Wiley & Sons, Inc. Reprinted by permission of John
Wiley & Sons, Inc.]
The chlorinated solvent
plumes (Figure 23.1.13) in
groundwater extend about 4000 ft
downgradient from FT-002. Concentrations
of TCE, DCE and VC
as high as 25, 51, and 1.5 mg/L, respectively,
have been observed recently.
Since DCE and VC were
not measured in LNAPL samples
from the source area, the presence
of DCE and VC at the site can be
attributed to dechlorination. The
data in Figure 23.1.14 show the
distribution of electron acceptor
concentrations observed at the site
including dissolved oxygen, nitrate
and sulfate. Background concentrations
for these compounds
are 10, 10 and 25 mg/L, respectively
and their absence within the
contaminated zones is an indication
of biodegradation of BTEX
and chlorinated solvents at the
site.
Figure 23.1.15, on the other
hand, shows the distribution of
metabolic by-products of the
biodegradation reactions including
ferrous iron and methane. The
presence of these by-products is
further evidence of biological activity
in the aquifer. Elevated chloride
and ethene concentrations as
shown in Figure 23.1.13 suggest
that TCE, DCE and VC are being
biodegraded. Wiedemeier et al. 1
calculated apparent biodegradation
constants for FT-002 using
trimethylbenzene as a conservative
tracer. Their results are shown
in Table 23.1.13. The data in Table
23.1.13 indicate biodegradation
rates of the chlorinated solvents at
the site ranging between 0 and
1.27 per yr.