Table 2 (cont'd).
b. Statistical analysis of DNT concentrations (g/g)
for discrete and composite samples.
Discrete samples
On-site analysis
Laboratory total
Sample
Mean
Mean of logs
Mean
Mean of logs
4.563a†
1
36,950
125,000
5.094a
2
7,210
3.853c
8,860
3.944d
3
23,500
4.358ab
44,000
4.636b
4
20,450
4.302ab
35,200
4.546b
5
8,125
3.903c
10,900
4.038d
6
13,150
4.117bc
16,700
4.223c
7
3,490
3.540d
3,740
3.572e
†
Numbers designated with the same letter are not significantly different at
the 95% confidence level.
ANOVA for log on-site analyses
ANOVA for log lab analyses
F ratio = 22.3***
F ratio = 153***
Error MS = 0.01098
Error MS = 0.00333
Least sign. diff. = 0.248
Least sign. diff. = 0.136
Linear correlation analysis for on-site analysis vs. lab analysis
(r = correlation coefficient)
Slope
Intercept
r
untransformed, non-zero intercept
0.262
6983
0.949
untransformed, zero intercept
0.350
0
0.817
log-transformed data
0.684
1.155
0.988
Results of paired t-tests for on-site vs. lab results
Means of seven discrete samples, t = 1.58 (NS)
Means of log values for seven discrete samples, t = 3.12*
Composite samples
On-site analysis
Laboratory total
n
7
7
mean value
23,800
33,600
standard deviation
3,140
2,390
RSD
13.2%
7.1%
ANOVA comparing on-site and lab analyses
F ratio = 43.0***
* Significant at the 95% level
*** Significant at the 99.9% level
** Significant at the 99% level
NS Not significant at the 95% level
tracts for location 2 were yellowish and, unlike
On-site analysis results showed that DNT con-
location 1, the intensity of the color did not corre-
centrations in the soil varied by over an order of
late with the results of colorimetric on-site analy-
magnitude, ranging from about 3000 to 30,000
g/g. Laboratory analyses showed the presence
sis. Addition of the EnSys reagent to extracts of
soils from this sampling location caused the de-
of TNT at concentrations ranging from approxi-
mately 3005000 g/g. These amounts were in-
velopment of an intense blue-purple color, also
indicative of the presence of DNT as the major
cluded in the totals for lab results.
contaminant. Concentrations of DNT were esti-
Agreement of duplicates for field analyses at
mated using absorbance measurements at 570 nm
location 2 was poorer than at location 1, with a
as recommended by Jenkins and Walsh (1991).
mean RSD of 23.0%. A mean RSD of 10.0% was
13
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