Handbook of Solvents - George Wypych - ChemTech - Ventech!

17.2 Fate-based management 1167
grade, and the initial concentrations. Under the conditions described, the relative
steady-state concentrations of the benzene derivatives were: toluene > benzene > chlorobenzene
> p-xylene > nitrobenzene > o-dichlorobenzene > o-cresol > ethyl benzene. Methylene
chloride and 1,1,1-trichlorethane would dominate the chlorinated hydrocarbons.
Among the group of unrelated organic solvents, the concentration of pyridine at the well
was predicted to increase rapidly. Pyridine would eventually dominate this group in the relative
order: pyridine > carbon disulfide > ethyl acetate > diethyl ether. The relative order of
fluorocarbons at the compliance well in terms of concentration was: F-21, F-22 >> F-12 >
F-113 > F-114 > F-112 > R-112a > FC-115 >> F-11.
In brief, the computer simulations predicted that all 28 organic compounds would
eventually migrate from the waste trench, and be detected at the compliance well. The predicted
concentrations varied by four orders of magnitude, and were largely influenced by
the initial concentrations used in calculating the mass loading rate to the aquifer.
17.2.3 MASS LIMITATIONS
The next step in this analysis was to determine whether these predicted concentrations
would pose an environmental hazard by evaluating whether the site was capable of attenuating
the concentrations of the organic compounds to levels that are protective of human
health. In Figure 17.2.4 the predicted steady-state concentrations of the organic compounds
Figure 17.2.4. The predicted steady-state concentrations (Css) of each solvent in groundwater at the compliance
point as a function of its Maximum Permissible (MPC) Concentration (Roy et al. 1 ).