PNNL

Abstract

Water flux and solute concentrations must be known to assess contaminant fluxes in the vadose zone but are seldom measured simultaneously at the same location. A water fluxmeter with divergence control was modified to measure solute concentrations by adding a funnel and collection vial to the bottom of the meter. Laboratory experiments using a coarse sand and a fine sand show that measured solute concentrations and known water fluxes combine to give an accurate assessment of solute flux. Using a nitrate tracer applied under steady influx rates of 621 mm yr-1, the breakthrough curves and the water fluxes were measured, and the solute fluxes were calculated. The flow divergence was examined by measuring the soil-water content and pressure head at different positions and by measuring the water flux passing through and around the water fluxmeter. Results show that the modified water fluxmeter provides a convenient way for long-term monitoring of contaminant flux.