New Mexico Geological Society Annual Spring Meeting — Abstracts

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Freshwater systems in arid and semi-arid regions remain understudied in microplastic research despite increasing global concern regarding plastic pollution. To address this gap, we examined the occurrence and spatial distribution of microplastics in freshwater bodies surrounding the Fort Stanton Cave area in New Mexico. Bulk water samples were processed using a combined approach of direct vacuum filtration and density separation, and suspected microplastics were categorized by morphology and color. Microplastics were detected at all sampled sites, with microfibers comprising the dominant morphology, followed by fragments and pellets. Polymer characterization using Raman spectroscopy and attenuated total reflectance–Fourier transform infrared spectroscopy (ATR-FTIR) identified polyethylene terephthalate (PET; polyester) and low-density polyethylene (LDPE) as dominant polymers. PET was primarily recovered from directly filtered samples, whereas LDPE was more abundant in density-separated fractions, indicating density-dependent recovery and potential methodological bias. Sites with higher anthropogenic influence, such as Alto Lake, exhibited greater microplastic abundances relative to less impacted locations, including Eagle Creek. This study provides baseline data and highlights the importance of integrating complementary processing methods for comprehensive microplastic recovery in arid freshwater systems.