28
ERDC/CRREL TR-02-12
Table 7. Summary for results from the high-level VOC study (concentrations in mg/L).
BENZ
M-XYL
PCE
Control
Sampler
Control
Sampler
Control
Sampler
Discrete Interval Sampler
Mean
133
131
145
140
145
140
Standard deviation
1.1
2.3
3.3
3.4
4.1
3.1
% RSD
0.8
1.7
2.3
2.5
2.8
2.3
HydraSleeve
Mean
137
136
148
144
144
142
Standard deviation
2.7
1.4
5.4
3.2
11.3
4.3
% RSD
2.0
1.0
3.6
2.2
7.8
3.0
Kabis Sampler
Mean
137
138
151
149
153
147
Standard deviation
3.2
2.5
5.1
4.9
7.1
5.5
% RSD
2.3
1.8
3.4
3.3
4.6
3.8
PneumoBailer
Mean
130
132
142
140
142
138
Standard deviation
2.7
1.9
3.5
3.8
4.5
2.7
% RSD
2.1
1.4
2.5
2.7
3.2
1.9
Diffusion bag sampler
Mean
108
114
99.7
108
94.7
105
Standard deviation
3.1
1.0
3.0
1.7
3.5
1.7
% RSD
2.8
0.9
3.0
1.6
3.7
1.6
With the PDB samplers, the differences tended to be larger. The contact
times for the samplers were seven days in the high-level study and 23 days for
the low-level study. In the low-level study, TDCE concentrations were signifi-
cantly lower in the PDB samplers (10%) while concentrations of MXYL were
significantly higher (18%). For the high-level study, concentrations of all three
analytes were significantly higher in the bag samplers, but these differences were
small (mean differences of 11% or less). Although it is possible that a longer
equilibration time was needed at the higher concentrations, the time we allowed
(seven days) was greater than the 2448 hours equilibration times observed by
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