The release of pollutants from aged field sediments

The success of groundwater remediation or natural attenuation depends on the availability of pollutants in the aqueous phase. As a rule, in a contaminated aquifer organic pollutants are accumulated more or less at sediment surfaces. In the worst case, the release of pollutants from aged sediments can become the rate-controlling step of groundwater remediation. Release kinetics of chlorinated hydrocarbons from carbon-rich field sediments have been studied using the gas purge technique. Dissolved pollutants are continuously stripped from the aqueous phase so that the partitioning is far from equilibrium. Even under these experimental conditions the pollutants are released from carbon containing sediments very slowly. The process can be described approximately using a two-compartment model following first order kinetics. The experimental data are the basis for improved modelling of contaminant transport in real aquifers.