A STUDY ON THE IMPACT OF MICROPLASTICS ON CAVE SEDIMENTS

Caves are significant geological and geoheritage features that can contain unique ecosystems, important drinking water reserves, evidence of historical and archeological human use, and natural archives in the form of sediments that provide insight into past climate conditions. The interconnectivity of the surface and subsurface environments make caves highly susceptible to all types of contaminants and among those are microplastics (MP). Though it is well documented that karst aquifers easily transport and store sediments, the impact of MPs on these sediments is an understudied topic. This study analyzed cave sediments from show caves, wild caves that have seen moderate visitation, and a pristine wild cave with very little visitation. Samples were collected from 0.5 x 0.5 meter plots with metal implements and stored in sterile glass jars to prevent further plastic contamination. Laboratory analysis was a two-step process that included vacuum extraction/purification onto 1.2-μm pore size gridded microfilters. Filters were then placed under a microscope and photographed. Identification and counting of microplastics was done on the photographs. Microplastics were present in all of the sediment samples with higher amounts along the tourist paths of the show cave. Small (less than 1mm), fragment-shapes dominate the samples. These fragments may have entered the caves via major flooding events. Fibers were the most common type of microplastic in the show cave samples. This suggests that synthetic clothing could be a significant source of microplastic pollution in show caves. The sediments of the relatively pristine cave contained a significantly lower concentration of microplastics and featured mostly small fragments. Microplastic monitoring in subterranean environments is a fundamental step to establish the base level of MP pollution and consequently to determine strategies for the protection and management of show caves.