1. Transport (tracer) test at the experimental field of the Borden site
How will the contaminant behave?
Transport retardation due to sorption

2. Note: this presentation requires additional material
Because it was not possible to get permission to make available on the internet figures from the two referenced papers, (1) Μackay et al. (1986) and (2) Roberts et al. (1986), please check out these papers ( to find the figures mentioned in this presentation.

5. Initial contaminant source: unlined landfill operating during 1940-1976

6. area of test measurements
area of landfill

7. Test area, plan view A’
test area a’
dense grid of sampling points in an area with dimensions 120 m x 80 m (within a former sand borrow pit) a
landfill
Μackay et al. (1986), Fig. 1
100 m A

8. Equipotential lines at the test site
a) April 1979
b) July 1979
Equipotential lines at the test site
The direction of groundwater flow (blue arrows) has seasonal variations at the test site
c) October 1979
d) December 1979
Μackay et al. (1986), Fig. 3

9. Sampling points (every 1 – 4 m): plan view
9 injection wells (over a depth of 2 – 3.6 m) a
0 m
0 m
Μackay et al. (1986), Fig. 5
80 m

10. Test site, cross section ΑΑ´A
Landfill A’ a a'
Site of tracer test
Landfill plume
Μackay et al. (1986), Fig. 2

11. Sampling points – cross section aa´ (every 0.2 – 0.3 m)
9 injection wells (over a depth of 2 – 3.6 m)
Μackay et al. (1986), Fig. 5

12. Injected substances: quantities, properties
Tracer: a solute that does not sorb and does not degrade

13. Injected substances: tracer spreading
chloride
boundary of area with chloride detections
60 m
647 days
462 days
85 days
1 day
-10 m
-10 m
30 m
Μackay et al. (1986), Fig. 8

14. Injected substances: comparison of spreading
chloride
carbon tetrachloride
60 m
647 days
462 days
633 days
85 days
380 days
1 day
16 days
-10 m
-10 m
30 m
-10 m
20 m
Μackay et al. (1986), Fig. 8

15. Injected substances: retardation due to sorption
chloride
Injected substances: retardation due to sorption
60 m
647 days
carbon tetrachloride,
Kow = 500
633 days
633 days
tetrachloroethene,
Kow = 400
-10 m
Roberts et al. (1986), Fig. 5
-10 m
30 m

16. Question for understanding
Q: How can you explain that sorption (Kp) is not analogous to contaminant hydrophobicity (Kow, Koc)?
Α: The main sorption mechanism is not absorption to organic matter
Comment: This is what happens at the Borden site: the organic carbon fraction is low, foc=0.02%, that’s why the relationship Kp = foc Koc cannot describe measured values

17. Sources of figures References
Note: the non-original material used in this presentation either it has been uploaded on the internet with a Creative Commons license, or it is publicly available on the internet (e.g. US policy for reports etc. by public agencies) and can be used with suitable attribution, or is used with license from the publisher.
Slides 3-6. Data on Maps: Google ©
References
Mackay, D.M., D.L. Freyberg and P.V. Roberts, 1986, A natural gradient experiment on solute transport in a sand aquifer 1. Approach and overview of plume movement, Water Resources Research, 22:13:
Roberts, P.V., M.N. Goltz and D.M. Mackay, 1986, A natural gradient experiment on solute transport in a sand aquifer 3. Retardation estimates and mass balances of organic solutes, Water Resources Research, 22:13: