and 10% decreased by about one-fourth when

for the water sample duplicates was used for each

held for 2227 days, and by almost one-half when

analyte. Table 4 shows the Henry's law constants

established for each experiment and the means for

held from 49 to 55 days. Samples that initially had

each of the six analytes, differentiating between

a 20% moisture content decreased by about 10 and

vessels with and without a membrane cover. Also

20% over these two exposure periods, respec-

included in Table 4 are some literature values

tively. Likewise between 5 and 15% of the water

reported by Dewulf et al. (1995) for Henry's law

was also lost from the saturated soil samples. The

constants for VOCs at 10C. Overall there was very

water samples lost ≤5% of their mass over these

periods. In addition to the individual water and

good agreement between the literature values and

soil values, the mean, or in one case the single

mean values determined for the eight chamber

highest value, obtained for the three chamber

experiments. This agreement between experimen-

vapor samples, is reported for each experiment.

tal and reported Henry's law constants supports

Extremely low values for the chamber vapor sam-

the decision to remove the aberrantly low vapor

ples were omitted, because they were suspected to

determinations.

have been caused by a needle blockage, thus pre-

The mean values for the two water reservoirs

venting the proper retrieval or transfer of a gas

(vessels with and without membrane covers) for

sample.

seven of the eight experiments were found to be

The ratio of analyte concentrations between the