CONTAMINANT MIGRATION IN ENGINEERED CLAY BARRIERS DUE TO HEAT AND MOISTURE REDISTRIBUTION UNDER FREEZING CONDITIONS

In this study, the effect of temperature distribution and its influenc e on contaminant migration in a silty clay soil were Three series of f reezing-column tests were performed with three different fluids: disti lled water, municipal waste leachate, and heavy metal - leachate solut ion. It was found that temperature distribution as a function of space and time was similar in all tests, most likely as a result of the lim ited amount of fluid intake. Moisture redistributions were varied as a function of experiment duration and the type of fluid used. The amoun t of fluid intake was directly related to the freezing time and the te mperature gradient in the freezing column. The amount of unfrozen wate r content, ion concentration and temperature gradient were the control ling parameters that contributed to the contaminant transport in the f rozen illitic silty clay soil. Na+-concentration profiles were mostly dependent on water movement in the soil column. The behaviour of Ca2and Mg2+ cations was similar to Na+; their concentrations in the soil solution decreased with freezing time due to ion exchange. The large a ccumulations of Pb2+, Zn2+, Cu2+, and Cd2+ in the lower 10 mm of the s oil column occurred as a result of cation exchange and precipitation m echanisms.