K. Broholm et al., Solvent release into a sandy aquifer. 1. Overview of source distribution and dissolution behavior, ENV SCI TEC, 33(5), 1999, pp. 681-690
Citations number
24
Categorie Soggetti
Environment/Ecology,"Environmental Engineering & Energy
This paper describes some of the results from a field experiment at the Can
adian Forces Base Borden, Ontario, Canada. Five liters of a chlorinated sol
vent mixture (2.0 L of trichloroethylene, 0.5 L of chloroform, and 2.5 L of
tetrachloroethylene) was released into a sandy aquifer to create a heterog
eneously distributed source. The dissolution and dissolved-phase plume deve
lopment from this source were studied in detail along a cross-section downg
radient of the source for a period of approximately 1 yr. At the conclusion
of the experiment, the site was excavated to map the actual distribution o
f solvent residuals in the subsurface. Dissolved-phase concentrations excee
ded 10% of the effective solubility of the individual components in the por
tion of the plume directly downgradient of the source, providing a strong i
ndication of the presence of dense nonaqueous-phase liquids (DNAPLs). Disso
lved-phase concentrations in several sampling points exceeded 50% of the ef
fective solubility. However, even with detailed groundwater monitoring, it
was not possible to determine the small-scale distribution of the DNAPL sou
rce. Lower dissolved concentrations occurred deeper than the DNAPL source z
one, likely as a result of vertical groundwater Row caused by fluctuations
in the water table elevation. Spatial delineation of the dissolved-phase pl
ume downgradient of the source correlated generally to the lateral and vert
ical location of the DNAPL source. The distance between the DNAPL source an
d the downgradient sampling cross section could be determined from breakthr
ough curves for some of the sampling points but not for others because slow
expansion of the DNAPL zone continued for some time during the dissolution
experiment.