tinuous mixing and heating to above 20C. Oxy-
compost and digester systems favor the break-
down and humification of plant material, it seems
gen initially present in the system was soon con-
likely that a mixture of reactive carbonyl moieties
sumed and reducing conditions of less than 100
with metabolically reduced TNT should produce
mV were maintained for 90 days (Tuomi 1995).
large, heterogeneous polymers that are resistant
to further degradation.
Analytical methods
The transformation of RDX in biotreatment sys-
Solvents used for extractions and analysis were
tems is thought to proceed through reduction of
HPLC grade from Alltech Associates, Inc.
nitro groups to yield nitroso-RDX compounds.
(Deerfield, Illinois). Concentrated H 2SO 4,
This is followed by ring cleavage and the forma-
Na2HPO4, and NaOH were reagent grade from
tion of methanol, formaldehyde, hydrazines, and
J.T. Baker, Inc. (Phillipsburg, New Jersey). Solid-
CO2 (McCormick et al. 1981). Degradation of RDX
phase extraction cartridges (Sep-Pak PoropakRDX)
and HMX in microbial cultures has also been stud-
were from Waters Corp. (Millford, Massachusetts).
ied (Binks et al. 1995, Roberts et al. 1996). The for-
HPLC analysis was performed using either a
mation of hydroxylated metabolites from cleaved
Spectra-Physics system (8875 autosampler, 8800
rings suggests that there are pathways that could
pump, 8490 detector, Hewlett-Packard 3396 inte-
lead to conjugated transformation products. This
grator) (San Jose, California) or a Waters system
is in contrast to living plant systems, where RDX
(717 autosampler, 616 pump, 600S controller, 996
is accumulated in tissues without transformation
photodiode array detector, Millenium worksta-
or apparent conjugation (Harvey et al. 1991,
tion) (Medford, Massachusetts). A Phenomenex
Checkai and Simini 1996).
(Torrance, California) Ultracarb 5 ODS(20) (4.6-
mm 250-mm, 5-m) reverse-phase column with
The objectives of this work were to evaluate
how various analysis methods differentiate be-
an Alltech Associates, Inc. (Deerfield, Illinois) C-
tween free and conjugated explosives and their
18 guard cartridge was used for the analytical
transformation products in composted soil and
separations. The aqueous/methanol (volume %/
digester sludge and to investigate the time course
volume %) gradient elution time steps were as fol-
of transformation and conjugation.
lows: start at 85/15, ramp to 65/35 at 8 minutes,
ramp to 42/58 at 10 minutes and hold for 13 min-
utes, ramp to 0/100 at 28 minutes and hold for 7
minutes, ramp down to 85/15 at 40 minutes and
MATERIALS AND METHODS
hold for 10 minutes before the next injection. The
flow rate was 0.8 mL/minute. Quantification was
Composts and digester sludges
by peak height performed at 254 nm, while peak
Compost samples from aerated windrow
identities and purities were assessed by compar-
composting pilot studies and full-scale treatments
ing sample and standard UV spectra (200400 nm)
at Umatilla Army Depot Activity, Hermiston, Or-
from a diode array detector, and retention times.
egon, were obtained from Black and Veatch Waste
Further confirmation of analyte identities was per-
Sciences, Tacoma, Washington. The compost-
formed using a Supelco (Bellefonte, Pennsylvania)
amendment mixture was composed of (% by vol-
cyanopropyl (CN) (4.6-mm 250-mm, 5-m) col-
ume) 30% cow manure, 25.4% sawdust, 25.4% al-
falfa, 14.3% chopped potato waste, and 4.9%
umn that separates the analytes in a different or-
chicken manure. The final compost mixture con-
der than the ODS column. The detection limits for
sisted of 70% amendments and 30% explosives-
the analytes were approximately 0.1 mg/kg of dry
contaminated sediment excavated from a dried-
compost.
out explosives waste lagoon. Samples of
Standards for HPLC analysis were made from
composted amendments that contained 10% un-
Standard Analytical Reference Materials obtained
contaminated sediments were also available as
from the U.S. Army Environmental Center (Aber-
controls. Digester sludge was from pilot-scale
deen, Maryland), except for 2,4DANT and
studies performed by Remediation Technologies
2,6DANT, which were supplied by Dr. Ronald
(Seattle, Washington) at U.S. Naval Submarine
Spanggord, SRI International (Menlo Park, Cali-
Base, Bangor, Washington. Anaerobic, slurry di-
fornia).
gestion was performed in lined pits. Contaminated
soil, water, an organic carbon source (potato
Solvent extraction
Compost samples were air-dried overnight,
starch), and an inoculum of microbes were mixed
in proportions to create a slurry that allowed con-
then ground to pass a 2-mm screen. Digester slud-
2
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