5 days after its application, but it was only due to lack of monitoring between day
0 and day 5. The mean tracer transit time, which marked the time frame of the tracer
occurrence during its underground movement, was slightly greater in the case of the
B139 well (at 21.4 days), while its value was recorded at 18.3 days for the B152
well. A significantly larger difference was observed in the values of the mean tracer
velocity, which was three times greater for the B139 well (at 0.70 m/day) than in the
case of the B152 well (0.23 m/day). The travel time to well B139, which is about
three times as far as well B152, was only slightly longer than to B152. This effect can
be caused by a preferential zone (trough filled by gravel). The migration does not
take place directly from the source well to B139, and, therefore, the tracer is diluted
(concentration about four times smaller than the B152 well). The dispersion coefficient, calculated on the basis of the travel velocity and dispersivity, is an order of
magnitude greater in the case of the B139 well (0.17 Â 10
À4 vs 0.26 Â 10
À5 m
2 /s)
compared the B152 well, for the same reason. Also the Péclet number value of 6.84
for B139 represents the domination of advection compared with mixed diffusion and
advection for the B152 well, which also indicates preferential advective flow
to B139.
0
50
100
150
200
250
300
0
1 0
2 0
3 0
4 0
5 0
6 0
Trace concentraƟon (mg/L)
Time (days)
B152
B139
Fig. 6.6 Time-dependent
tracer concentration at two
selected wells
Table 6.2 Outputs from the Qtracer2 software for the B139 and B152 wells
Parameter
B152
B139
Recovery of injected tracer
2.46%
1.85%
Distance from input to outflow point
4.23 m
14.42 m
First arrival
1 day
Not defined
Time to peak tracer concentration
9 days
13 days
Peak tracer concentration
245 mg/L
64 mg/L
Mean tracer transit time
18.3 days
21.4 days
Mean tracer velocity
0.23 m/day
0.70 m/day
Péclet number
4.44
6.84
Longitudial dispersion coefficient
0.26 Â 10
À5 m
2
/s
1.7 Â 10
À5 m
2
/s
110
V. Stejskal et al.
0 and day 5. The mean tracer transit time, which marked the time frame of the tracer
occurrence during its underground movement, was slightly greater in the case of the
B139 well (at 21.4 days), while its value was recorded at 18.3 days for the B152
well. A significantly larger difference was observed in the values of the mean tracer
velocity, which was three times greater for the B139 well (at 0.70 m/day) than in the
case of the B152 well (0.23 m/day). The travel time to well B139, which is about
three times as far as well B152, was only slightly longer than to B152. This effect can
be caused by a preferential zone (trough filled by gravel). The migration does not
take place directly from the source well to B139, and, therefore, the tracer is diluted
(concentration about four times smaller than the B152 well). The dispersion coefficient, calculated on the basis of the travel velocity and dispersivity, is an order of
magnitude greater in the case of the B139 well (0.17 Â 10
À4 vs 0.26 Â 10
À5 m
2 /s)
compared the B152 well, for the same reason. Also the Péclet number value of 6.84
for B139 represents the domination of advection compared with mixed diffusion and
advection for the B152 well, which also indicates preferential advective flow
to B139.
0
50
100
150
200
250
300
0
1 0
2 0
3 0
4 0
5 0
6 0
Trace concentraƟon (mg/L)
Time (days)
B152
B139
Fig. 6.6 Time-dependent
tracer concentration at two
selected wells
Table 6.2 Outputs from the Qtracer2 software for the B139 and B152 wells
Parameter
B152
B139
Recovery of injected tracer
2.46%
1.85%
Distance from input to outflow point
4.23 m
14.42 m
First arrival
1 day
Not defined
Time to peak tracer concentration
9 days
13 days
Peak tracer concentration
245 mg/L
64 mg/L
Mean tracer transit time
18.3 days
21.4 days
Mean tracer velocity
0.23 m/day
0.70 m/day
Péclet number
4.44
6.84
Longitudial dispersion coefficient
0.26 Â 10
À5 m
2
/s
1.7 Â 10
À5 m
2
/s
110
V. Stejskal et al.