4.3 Experimental Design


 4.3.1 Batch Sorption Studies.


 Unless otherwise specified, all experiments in the

 sorption studies were performed using 40 ml glass vials with

 screw caps and teflon lined septa as the reactors.


 Batch adsorption. The objectives of this study were:

 (1) to determine the adsorption partition coefficients of

 phenol, 2,4-dichlorophenol and pentachlorophenol in an

 aquifer with very low organic matter, (2) to show the

 effects of mixing of phenol, 2,4-DCP and PCP on sorption,

 and (3) to determine the effects of adding sodium azide

 (NaN3). The chemicals were tested both individually and as

 a mixture. In each vial, 40 grams of sandy soil and 20 ml

 of solution were mixed and tumbled continuously by a rotator

 at room temperature (approximately 23 C) for 24 hours to

 ensure complete mixing. Sodium azide (NaN3) was added in

 two different concentrations to selected vials to eliminate

 biological degradation. Four chemical concentrations were

 used in this study: 10, 7.5, 5 and 1 mg/l. The experimental

 matrix consisted of three treatments, four concentration

 levels, and four sample categories as listed in Table 4-1.

 Replicates were prepared for six of the randomly chosen

 treatments for the purpose of quality assurance. The

 average number of those treatments was used for the

calculations.