DIFLUOROBENZOATES AS NONREACTIVE TRACERS IN SOIL AND GROUND-WATER

Over the past 10 years, several fluorinated derivatives of benzoic acid have proven their usefulness as nonreactive water tracers. In this study, the suitability of four previously untested isomers of difluorobenzoate (DFBA) as saturated- and unsaturated-zone tracers was examined in a series of laboratory and field experiments. Experimental conditions included batch shaking tests with two different soils, laboratory soil column tests under saturated and unsaturated conditions, a three-month aquifer tracer test, and a month-long tracer test in a field soil. Bromide, which is considered nonreactive in most hydrological environments, was included as an index tracer in each experiment. Under every condition, each DFBA isomer showed the same concentration distribution and mass recovery as Br-. These and other previously tested fluorobenzoates were ranked according to their suitability as nonreactive soil and ground-water tracers.