products by the base/acid hydrolysis may be due
end of full-scale operations indicate that fully de-
to the disruption of the humic polymers and in-
veloped compost has a residual capacity to reduce
creased accessibility of bonds.
TNT and conjugate the resulting transformation
The transformation of TNT to solvent-non-
products. This does not explain the loss of trans-
formation products in the presence of sand with
extractable reduction products appears to go
negligible organic carbon (<0.2%), but is consis-
through two stages of covalent conjugation in com-
tent with losses of these compounds reported for
post and digester sludge. In the first stage, a sig-
acidified water (Jenkins et al. 1995). None of the
nificant percentage of the bonds are hydrolyzable
azoxy transformation products of TNT were de-
by acid or base alone or a combination of base and
tected.
acid. As processing continues, a second stage
occurs in which the bonds are either altered to
form different functional groups that are non-
Analysis for triaminotoluene
hydrolyzable, or additional bonds form as the
in anaerobic cultures
Anaerobic cultures from an experiment at the
bound transformation products are further
U.S. Army Construction Engineering Research
reduced. The termination of treatment as soon as
Laboratories were received in anaerobic serum
solvent-extractable TNT concentrations drop
bottles. The TNT amended cultures had been in-
below a specified action level may stop the conju-
cubated until all of the TNT, aminoDNTs, and
gation processes at the first, hydrolyzable stage.
diaminoNTs had been depleted. A sample with-
This may result in the potential for long-term
drawn by syringe, mixed with acetonitrile, and
releases of TNT metabolites that might not occur
analyzed immediately contained TAT, but no other
if composting or digesting is continued into the
reduction products. An unamended control bottle
second stage of nonhydrolyzable conjugation. The
was blank. The vessel was opened and 1.5 g of the
most current study of the multispecies toxicity of
solid material was solvent-extracted and base/
the fully developed composts from the Umatilla
acid hydrolyzed as above. No TNT or any of its
pilots (Gunderson et al. 1997) shows that long-term
reduction products were recovered by any of the
ecological effects are minimal. Some nonlethal
treatments.
effects on plants were observed.
Spike-recovery studies indicated that current
methods do not adequately quantify TNT trans-
formation products, particularly at the low con-
CONCLUSIONS
centrations that characterize remediation goals.
Previous researchers using radiolabels found
Current methods are sufficient to remove all of the
that the majority of TNT reduction products were
analytes that are extractable. These may comprise
bound in non-solvent-extractable forms. Fraction-
the explosives remaining undissolved in the soil,
ation of composts (Caton et al. 1994, Pennington
plus the pool of transformation products that are
et al. 1995) and soils (Comfort et al. 1995) into func-
in the aqueous phase or sorbed and not yet conju-
tional categories indicated that 2560% of the
gated to the solid phase of the organic matter.
unextractable residues were associated with fulvic
However, the transformation products that are
and humic acids. Our results agree with these find-
released by hydrolysis represent a dynamic pool
ings while providing the necessary identifications
of weakly conjugated amines that are subject to
of hydrolyzed analytes. In concurrent research,
further reduction and/or bond transformations
Thorn (1997) is using NMR spectroscopy to iden-
that eventually become unhydrolyzable as humi-
tify the bonds that are formed when 15N-labeled
fication continues. Therefore, analyses of
aminoDNTs and diaminoNTs are reacted with
bioremediation matrices should be considered as
humic substances, soils, and peat. Identification
a qualitative descriptor of the progress of humifi-
of which bonds are hydrolyzable will be accom-
cation and the capacity to covalently conjugate
plished by comparing the NMR spectra of the con-
transformation products rather than as a quanti-
jugation products before and after hydrolysis. Pre-
tative measure of the absolute amounts of various
liminary experiments with aniline/humic
analytes present.
conjugates indicate that the imine and anilide
The purpose of the base/acid hydrolysis is to
bonds are hydrolyzable by base or acid, while the
break the bonds between TNT transformation
anilinoquinone, anilinohydroquinone, and hetero-
products and organic carbon biopolymers such as
cyclic N-bonds are not. Thus, it appears that the
humic acid. Detection limit studies showed that a
increased recovery of conjugated transformation
minimum of 0.1 mg of transformation product
10
Previous Page
