Table 4 (cont'd). Results from sampling location 4, Hawthorne
error and sampling error gave analysis
AAP site.
standard deviations of 217 and 265 for
the field and lab methods, respectively
b. Statistical analysis of TNT concentrations (g/g) for dis-
(Table 4b), and estimates for the sam-
crete and composite samples.
pling standard deviation of 1971 and
2154 from the field and lab data. Thus,
Discrete samples
even for this sampling location, where
On-site analysis
Laboratory total
the analyte distribution was the least
Sample
Mean
Mean of logs
Mean
Mean of logs
heterogeneous of the four locations dis-
5880a†
1
3.769a
6270a
3.797a
cussed thus far, sampling error was eight
2
3110b
3.492b
3770b
3.575b
to nine times greater than analytical er-
ror, regardless of whether analysis was
3
1170d
3.065c
1240d
3.092c
conducted on-site or in the lab.
4
563e
2.727d
587de
2.768d
The results from on-site and lab analy-
5
85.1e
1.915e
108e
2.009e
sis were linearly correlated, and a slope
of the best fit regression line of 0.912
6
1830c
3.262c
2010c
3.304c
was obtained with an r of 0.997 (Table
7
1180d
3.071c
1150d
3.060c
4b). The relationship with zero inter-
†
Numbers designated with the same letter are not significantly different at
cept was slope = 0.911 and r = 0.997,
the 95% confidence level.
indicating that the accuracy of the field
test vs. the lab test was 91.1%. A paired
ANOVA for on-site and lab analyses
t-test of the on-site and lab results said
Untransformed
that they were not significantly differ-
On-site
Lab
ent (Table 4b). ANOVA comparing on-
F ratios
166***
133***
site and lab methods for the composite
Error MS
47,163
70,287
analyses produced an F ratio of 3.44,
Least sign. diff.
514
627
Analysis s
217
265
which is not significant at the 95% level.
Sampling s
1,971
2,154
Overall, the on-site TNT method pro-
(s = standard deviation)
vided very reliable results for sampling
Linear correlation analysis for on-site analysis vs. lab analysis
location 4.
(r = correlation coefficient)
Analysis of composite samples pro-
Slope
Intercept
r
vided mean and standard deviation con-
untransformed, non-zero intercept
0.912
1.846
0.997
centrations of 1760178 and 2000298
untransformed, zero intercept
0.911
0
0.997
g/g for on-site and lab methods re-
log-transformed data
1.020
0.110
0.999
spectively. Mean values from the seven
Results of paired t-tests for on-site vs. lab results
discrete samples were 1970 and 2160
g/g respectively. Here, again, analysis
Means of seven discrete samples, t = 2.07 (NS)
of composites provides acceptably reli-
Composite samples
able results with both methods. Over-
On-site analysis
Laboratory total
all, the results for sampling location 4
n
7
7
confirm the value of the on-site test in
mean value
1760
2000
providing rapid, reliable results for ar-
standard deviation
178
298
eas with concentrations varying over
RSD
10.1%
14.9%
orders of magnitude.
ANOVA comparing on-site and lab analyses
F ratio = 3.44 (NS)
Sampling location 5
* Significant at the 95% level
*** Significant at the 99.9% level
Analytical results for sampling loca-
** Significant at the 99% level
NS Not significant at the 95% level
tion 5 are presented in Table 5a. Reac-
tion of acetone extracts with the EnSys
results were sufficiently homogeneous to make
reagent produced pink to reddish solutions, again
transformation unnecessary. LSD tests for both
pointing to TNT as the likely major contaminant.
on-site and lab results showed that six of the seven
Laboratory analysis confirmed that TNT was the
samples were significantly different from one an-
contaminant present at the highest concentration
other. Partitioning the variances into analytical
for all except sample 5. In sample 5, the TNT con-
18
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