Synchrotron Radiation for Detecting Movement of a Volatile Soil Liquid

Abstract

Heat and volatile liquid transport in soils are physically coupled processes. Soil water movement driven by thermal gradients has received considerable attention both experimentally and via models. This is appropriate since the thermal regime of underground electric power cables, pipelines, agricultural soils, and nuclear-waste repositories influences their ability to function effectively. However, available experimental liquid concentration data are of relatively low resolution, generally about one measurement per cm. By using synchrotron x rays we were able to nondestructively obtain high (50 μm) spatial resolution, time-lapsed data for the thermally driven movement of dibromomethane (DBM) in soil. Under repeated temperature cycling during a 22 h period, DBM movement within a sealed, 25-mm-long quartz sand