Geoscience Reference
In-Depth Information
Fig. 18.18 a Plot of the model predicted versus experimentally observed isotherms of 1,2-
dichlorobenzene, 1,2,4-trichlorobenzene, 1,2,3,4-tetrachlorobenzene, and hexachlorobenzene in
Dickinson sediment. Solid lines are predicted isotherms using the irreversible adsorption model.
Dotted lines are the linear isotherms plotted using the K
oc
values obtained in adsorption
experiments. The symbols are experimental observations. b Plot of the model predicted versus
experimentally observed isotherms of 1,4-dichlorobenzene in Dickinson, Lake Charles, Lula, and
Utica sediments. Solid lines are predicted isotherms using the irreversible adsorption model.
Dotted lines are the linear isotherms plotted using the K
oc
values obtained in adsorption
experiments. The symbols are experimental observations. Reprinted with permission from Chen
et al. (
2000
). Copyright 2000 American Chemical Society
sorbent-dependent and is due to matrix deformation. On peat, the TII of DCB
hysteresis displayed a downward trend, from 0.6 to 0.3, while on lignite TII
increased from 0 to 0.5 with increasing concentration.
Theoretically, self-diffusion in PP and BZL should be slower at lower con-
centrations, in both the uptake and release directions. In contrast, the experimental
results show that uptake and release of bulk DCB are nearly the same as the tracer
at the two concentrations (Fig.
18.19
). In some cases, however, bulk DCB shows a
biphasic rate while the tracer does not, which may be explained by sorbate-induced
deformation of the matrix. Comparison between bulk sorption versus forward
isotope exchange kinetics and bulk desorption versus reverse isotope exchange
kinetics, at the sorption point (Fig.
18.20
) provides further evidence of the matrix
