USE OF BARITE-MODIFIED HYDROGEL BEADS TO SIMULATE FREE-PHASE ORGANIC POLLUTANT TRANSPORT IN AQUATIC SYSTEMS

The fates of organic pollutants entering surface waters and karst aquifers are difficult to track and model because the mobility of specific compounds is dependent on physicochemical properties such as density. Alginate hydrogel beads have been used as tracers to mimic the free-phase transport of organic compounds less dense than water (LNAPLs) by adding flotation agents (glass beads, gas inclusions) to the alginate matrix. In this study, we added relatively dense barite (BaSO₄) powder to produce alginate hydrogel beads that could be designed to mimic the density of NAPLs between 1.01 and 1.83 g cm^-3. Beads mimicking the density of free-phase organic contaminants relevant to Superfund sites were produced in the laboratory. Increased alginate concentrations produced stronger gel beads with greater resistance to sediment abrasion. Fluorescent pigment powders were added to differentiate beads representing specific organic compounds. Experimentally measured minimum stream flow velocities needed to transport barite-modified hydrogel beads were consistent with anticipated and measured bead densities.