MEASURING THE ADHERENCE OF CARBOXYLATED AND NON-FUNCTIONALIZED POLYSTYRENE MICROSPHERES ONTO A KARST SEDIMENT

Particle movement and processing in karst aquifers has received comparatively less attention than solute and aqueous transport. Since sediment can act as a sorption site for some contaminants and move them through the aquifer, it is important to understand how particles are transported in karst aquifers. Microspheres (laboratory engineered particles ranging from <1 um – 1,000 um with a variety of surface charges and fluorescent tags) offer an opportunity to study particle movement in karst aquifers via laboratory batch experiments and multitracer field tests. Several researchers have used microspheres in multitracer field experiments to better understand particle movement in karst aquifers with respect to bacterial motility. Many of these experiments resulted in low recovery of microspheres which was attributed to sorption of the spheres onto aquifer sediments or mineral surfaces, yet few researchers carried out sorption trials to quantify the adherence. In these experiments, we measure the adherence of 1-um, yellow-green, fluorescent carboxylated and non-carboxylated microspheres on a karst sediment collected from a limestone cave in Monroe County, WV. Initial concentrations and supernatant concentrations of microspheres were measured using an LSR Fortessa Analyzer. Preliminary results indicated that percent adherence of carboxylated microspheres ranged from 74.3% (in a 1:500 sediment:solution ratio) to 99.9% (in a 1:4 sediment solution ratio). This was consistent with the recovery rate of microspheres reported in field experiments. For carboxylated microspheres, initial batch experiments resulted in a linear isotherm fit (R² = 0.89) with adsorption coefficient, K_D = 0.24.