BOUNDARY-CONDITION AND SOIL ATTRIBUTE IMPACTS ON ANIONIC SURFACTANT MOBILITY IN UNSATURATED SOIL

Surfactant mobility in unsaturated soil will impact the effectiveness and efficiency of using these compounds for in situ environmental reme diation above the water table. For this reason, transient unsaturated column tests were used to study the influence of boundary conditions a nd soil attributes on anionic surfactant transport. In these tests, aq ueous surfactant solutions were injected into the inlet of horizontall y mounted soil columns. Two commercial anionic surfactants were used, an alkyl ether sulfate (AES) and a linear alkylbenzene sulfonate (LAS) . The overall study was divided into two parts. First, boundary condit ion effects including injected surfactant solution concentration, init ial moisture content, and surfactant application rate were investigate d. Increasing the injection solution concentration increased anionic s urfactant mobility in the column while changes in the initial soil moi sture content and surfactant application rate had no significant impac t. Second, the impacts of soil attributes such as texture, dominant ex changeable cation, and resident organic matter were measured. With res pect to texture, mobility was found to be greater in a sandy soil as c ompared with two loamy soils. Both surfactants, especially LAS, were f ound to be more mobile in a Na+ dominated soil rather than one dominat ed by Ca+2. The absence of soil organic matter increased LAS mobility.