Environmental Fate and Transport of Solvent-Stabilizer Compounds - Environmental Investigation and Remediation - page 169

GLOUCESTER LANDFILL SOIL-COLUMN STUDY
(PRIDDLE AND JACKSON, 1991)

Retardation factors measured from soil core data, presented in Table 3.22, were generated
by injecting 1,4-dioxane, THF, diethyl ether, 1.2-dichloroethane, trichloromethane, benzene,
and 1,1-dichloroethylene into soil cores at i xed and varying l ow rates and using iodide as a
conservative tracer to index relative breakthrough. The soil cores were from an aquifer at a
well-studied landi ll site in Gloucester, near Ottawa, Canada. The contaminants studied were
selected because they are found in the aquifer at the site.
Iodide is considered an ideal tracer because it experiences little or no sorption. It has symmetrical
breakthrough curves in soil-column tests, indicating equilibrium sorption behavior during transport
because any sorption is temporary and reversible and little or no sorption occurs. 1,4-Dioxane
breakthrough curves display a similarly symmetrical pattern, whereas the other contaminants dis-
play long tailing, that is, the plot of relative concentration to pore volume rises sharply, then slowly
decreases as an increasing number of pore volumes passes through the soil core.
For 1,4-dioxane, a retardation factor of 1.1 was obtained from soil core tests at pore-water
velocities of 45 and 90 cm/day.

TABLE 3.22
Comparison of Retardation Factors ( R f ) Based on Field Data, Equations, and Column Data

Retardation Factor Value Based on Type of Data

Field Data Laboratory Data

Plume
Length
Estimate b

Purge
Well Test
Result c

Solubility a
(g/L)

Correlation
Equation d

S and W
Equation b,e

Center
of Mass f

Maximum
Concentration g Compound log K ow

1,4-Dioxane M 1.6 1.4 1.6 1.0 1.1 1.2

−0.27

Tetrahydrofuran M 0.46 2.2 2.2 2.5 1.0 NT NT

1,2-Dichloroethane 8.7 1.48 7.6 n.p. 5.7 1.2 7.2 4-5

Benzene 1.78 2.04 8.8 n.p. 10.0 1.4 14.3 6-8

1,1-Dichloroethylene 0.40 2.13 n.m. n.p. 11.0 1.5 10.7 6-7

Source: From Jackson, R.E. and Dwarakanath, V., 1999, Ground Water Monitoring Review 19(4): 102-110. With permission.

a

M = Miscible.

b

R f = L Cl / L org , the ratio of the length of the chloride plume ( L Cl ) to that of the organic plume ( L org ) (Patterson et al., 1985);
n.m. = not measured. The chloride originated from the same waste-disposal trench as the organic compounds.

c

Tracer-labeled contaminants were injected at 140 L/min and extracted 5 m down gradient at the same rate for 6 days;
samples were collected at multilevel sampling wells between injection and extraction wells. The retardation factor was
determined from the ratio of the times at which C / C 0 = 0.5 for the organic compound and the tracer compounds (iodide and
l uorinated benzoic acid) (Whifi n and Bahr, 1984); n.p. = contaminant not present.

d

Correlation equation from i eld data at the Gloucester landi ll site: log( R f − 1) = 0.5 log( K ow ) − 0.065 (Patterson et al.,
1985).

e

R f = 1 + ρ b K d / n , where K d = 3.2 f oc × 0.72( K ow ) (S and W = Schwarzenbach and Westall, 1981); NT = not tested.

f

In column test data, the center of mass of organic compound versus the center of mass of iodide (Priddle and Jackson,
1991); NT = not tested.

g

In column test data, the ratio of the time at which C / C max = 0.5 for organic plume versus the time at which C / C max = 0.5 for
iodide plume (Priddle and Jackson, 1991).