No abstract

Hydrogel tracer beads as potential proxies for non-aqueous phase liquids in karst: Development of an optical quantification method for fluorescent beads Habib Bravo-Ruiz Sinkholes and sinking streams are examples of karst features that can serve as direct pathways for contaminants, including non-aqueous phase liquids (NAPLs), to quickly enter karst aquifers. Once NAPLs are in karst aquifers, their fate and transport is difficult to predict and is not well understood. In this study, floating hydrogel tracer beads (HTBs) are developed and tested to help gain a better understanding of the fate and transport of NAPLs. The HTBs are formed by cross-linked sodium alginate polymers that can be made with different fluorescent pigments and density-modifying additives. The focus of this research was on the development and testing of an optical method for quantifying HTB transport. This optical quantification method records the transport of fluorescent HTBs as they move under an apparatus holding ultraviolet lights and a camera. HTBs transport is video recorded and then quantified using an image analysis algorithm. The method was validated in tracer tests of short duration at the Experimental Stream Facility in Milford, OH and applied in tracer tests of long duration at Buckeye Creek Cave, WV. The results of these tests agreed well, but suggest that the optical quantification method is better suited for tracer tests of short duration in controlled environments.