formed data from both the screening and HPLC
laboratory analysis. Concentrations of TNT ranged
from about 55,000 to 112,000 g/g for location 7
determinations for the discrete samples, indicated
and from about 40,000 to 119,000 g/g for loca-
that samples were significantly different at greater
than the 99.9% confidence level. LSD tests showed
tion 7R.
that the discrete samples were nearly all signifi-
Samples from both locations 7 and 7R contained
cantly different from one another (Table 6b).
a high percentage of stones compared with
Means and standard deviations from com-
samples from any other location. In the field, 15
posite analyses were 970 32 and 1010 91 g/g
59% of the soil weight was removed during ho-
for the screening and HPLC methods, respec-
mogenization for location 7 and 2040% was ex-
tively, which were not significantly different at
cluded for location 7R. RSDs for field analyses
the 95% level. The mean values from the seven
were 13.3 and 4.9% for 7 and 7R, respectively,
discrete analyses were 869 and 901 g/g for the
indicating that the resulting material was fairly
screening and HPLC methods respectively.
homogeneous.
Correlation of screening results with those from
When these samples were further processed in
HPLC resulted in an r of 0.999 and a slope of
the laboratory, a large percentage of the remain-
0.968 using a model with an intercept and the
ing material proved to be smaller stones, which
untransformed data (Table 6b). The model with
we removed before laboratory analysis. The ma-
zero intercept likewise gave a slope of 0.967 and
terial excluded in the laboratory ranged from 51
an r value of 0.999, indicating that the intercept in
64% for location 7 and 4767% for location 7R.
This was in addition to the material already ex-
the above model is not significantly different from
zero. Nevertheless, at very low levels (<10 g/g),
cluded during field homogenization. Samples of
the segregated stones were extracted and ana-
there does appear to be a small positive bias for
lyzed in the same manner as the soil and the re-
the screening method and this is reflected by the
sults for the stones segregated from sample 4 for
lower slope and correlation coefficient for the log-
both locations 7 and 7R are presented in Table 7e.
transformed model. At present we have not been
TNT concentrations obtained for the stones ranged
able to identify the source of this bias. This bias
from 6025 to 8150 g/g, while the corresponding
was not detected using a paired t-test for the re-
sults from the seven discrete samples, which
soil for these samples had TNT concentrations
over 100,000 g/g. Because the small stones had
meant that results from the two methods were
not significantly different at the 95% confidence
much lower concentrations of TNT than the soil,
level. Similarly, there was no significant bias in
their exclusion from the material originally ana-
the means of the two methods applied to the
lyzed in the field using the colorimetric method,
composite samples where the concentrations were
prior to laboratory analysis, is the major factor
about 1000 g/g.
accounting for the higher concentrations observed
Clearly, composite sampling and screening
in the laboratory analyses.
analysis provides an inexpensive, precise ap-
A problem was encountered in the field that
proach for estimating site contamination levels
affects the screening results presented for sample
for ammonium picrate at this sampling location.
location 7 (but not 7R). The automatic pipette used
to dispense the proper volume of extracting sol-
vent malfunctioned at location 7 and the problem
Volunteer AAP
was not discovered until the on-site analyses had
Sampling locations 7 and 7R
been completed. This problem resulted in vary-
Analytical results for sampling location 7, and
ing amounts of acetone being used for extraction
a duplicate set of samples from location 7, labeled
from sample to sample rather than the 100 mL
specified. Probably the differences were not large,
7R, are presented in Tables 7a and 7c respectively.
but there is additional uncertainty in the results
Location 7R was offset from location 7 by 15 cm,
because of this problem. The mean RSD for the
so like-numbered samples from location 7 and 7R
field analyses for location 7R was 4.9%, compared
are all located 15 cm apart. Acetone extracts for
to 13.3% for location 7. Laboratory results were
these soils were dark brick-red, implying that
analyte concentrations were probably quite high.
unaffected by this problem and nearly identical
When extracts were diluted (4.0 L to 20 mL) and
mean RSDs were found for locations 7 and 7R (6.0
and 5.1% respectively).
reacted with EnSys reagent, a reddish color re-
ANOVA was conducted on the mean concen-
sulted, indicating that TNT was probably the ma-
trations from the seven samples for both loca-
jor analyte present; this was later confirmed by
23
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