87
Three factors were varied to determine their effects on the rate constant
and partition coefficient: initial TCE concentration, dissolved oxygen (DO)
concentration, and presence of chloride. Lineralized and non-linear forms of Eq.
3.7 were used to determine partition coefficients and rate constants.
The rate constants and partition coefficients obtained from the tests are
summarized in Table 5.2. Examples of non-linear fits of Eq. 3.7 to the batch data
are shown in Fig. 5.1 for iron from Sand 12 and in Fig. 5.2 for Peerless iron. In
general, no distinct difference exists for the rate constants and partition
coefficients obtained using the linear and non-linear fits, except for Test J (Table
5.2). For Test J, similar rate constants were obtained, but the partition coefficient
obtained from the linear model fit was four times lower than that obtained from
the non-linear model fit. The difference in the partition coefficients for Test J is
due to scatter in the experimental data.
5.1.1 Initial TCE Concentration
The rate constants and partition coefficients are shown as a function of
initial TCE concentration in Fig. 5.3. Neither the rate constant nor the partition
coefficient appears to depend on the initial TCE concentration. The scatter in the
partition coefficients is largely due to variability in the foundry sand iron. Partition
coefficients for the foundry sand iron ranged between 0.77 L/kg and 2.41 L/kg,
whereas partition coefficients for the Peerless iron ranged between 1.52 L/kg and
2.12 L/kg.