7-19 Examination of Microplastics and New Study Methods in Daves Cave, a Pristine Cave in Central Kentucky.

Session: Undergraduate Research, Part I (Posters)

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Abstract:

Microplastics (MPs) are an emerging globally pervasive contaminant, yet their occurrence and transport within subsurface environments remains poorly understood, particularly in caves, where sampling is logistically challenging and prone to researcher-introduced contamination. This study evaluates new field methods to diminish contamination during sampling and characterizes MP concentrations within Daves Cave, a geographically and morphologically isolated cave system in Pulaski County, Kentucky. The cave was selected for its accessibility and sinkhole entrance, which limits surface-subsurface interaction. Water and sediment samples were collected cross-sectionally, from eight sites during two field visits, spanning ~450 m of passage. Sediment sampling locations were divided into an “impacted” zone nearest the entrance and an “unimpacted” zone 15 cm opposite. MPs in water were isolated via vacuum filtration; MPs in sediment were isolated via a bulk density separation device and concentrated NaCl solution, followed by vacuum filtration. Impacted areas of a sampling site exhibited substantially higher MP concentrations (~40 items/kg) than unimpacted sediments (~10 items/kg). Spatial trends in unimpacted sediment and water samples align with established relationships between water velocity and MP retention observed in river systems, where higher velocities correspond to elevated suspended MP loads and reduced retention. Comparison to similar studies suggests that MP contamination in pristine caves is strongly governed by the degree of interaction with surface air currents, streams, and biota which is largely dictated by cave-entrance morphology and site topography. Additionally, these findings illustrate the influence of researcher-introduced contamination and demonstrate the effectiveness of the implemented sampling protocols.

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