respectively, were irreversibly held onto the soil matrix

after desorbing with distilled water for 40 hours. These

are percentages of initially adsorbed masses that were

irreversibly adsorbed (not desorbed). Isaacson and Frink

(1984) reported similar irreversibilities among other

substituted phenolic compounds. The small Freundlich

exponent values of PCP desorption indicating that the

desorption intensities were low.


 5.3 Column Sorption


 Column sorption experiments were performed on column #1

and column #2. Breakthrough curves for phenol, 2,4-DCP and

PCP from column #1 are shown in Figure 5-7. These curves

were plotted using the data presented in Appendix B. The

breakthrough curve of the conservative tracer, ammonium

chloride, was reconstructed from the data obtained in the

desorption experiment as described in Chapter 4.

 Because these column experiments were designed to

simulate a treatment of groundwater contaminated by a point

source such as a spill, only a limited amount of analytes

were spiked onto each column. This method differs from the

traditional way of performing breakthrough curve

experiments, and make the calculation of retardation factors

very difficult. The first task was to determine the initial

concentration, C This value should range from 3.0 mg/l if
 o
a complete mixing mode was assumed, to 6.0 mg/l if a plug

flow mode was assumed. However, the highest concentration