Batch tests have been performed to investigate the sorption of three organic chemicals (TCE, toluene and methyl ethyl ketone) to clayey soils with low organic carbon contents. The results from the batch tests are compared with estimates of the distribution coefficients from column tests and from correlations with soil organic carbon content. For TCE and toluene the batch tests give distribution coefficients that are two orders of magnitude greater than would be estimated from organic carbon, and one order of magnitude greater than from column tests. Some of the factors that could contribute to these differences are discussed.
The Castlereagh landfill site in Western Sydney has been used for the disposal of liquid wastes for over 20 years. A natural clay layer, known as the Londonderry clay, is used as the primary barrier to control contaminant migration. This layer is typically 11.4 m thick, and is underlain by a more permeable clayey gravel layer known as the Rickabys Creek Gravel. A number of organic groundwater contaminants have been detected in some of the on-site monitoring bores in the gravel layer. These observations have resulted in many studies being performed to investigate the fate of contaminants at the site (e.g. Airey and Carter, 1995). As part of these studies a series of batch tests have been performed to determine the distribution coefficients for selected organic chemicals, methyl ethyl ketone (MEK), trichloroethylene (TCE), and toluene to the Londonderry clay and Rickabys Creek gravel. Tests to investigate the influence of electrical conductivity, soil to solution ratio, single or multi-compound application and equilibrium time have been performed. The results obtained from these tests are reported and compared with data from other studies. The distribution coefficients are compared with widely used predictions based on the soil organic carbon content.
