VOLUME 19 (Supplement)

Distribution, abundance, and characteristics of microplastics in surficial beach sediments of Miagao, Iloilo

The Philippines is a major contributor to global oceanic plastic pollution, yet localized studies on microplastic (MP) contamination in coastal sediments remain scarce. This study aimed to provide the first quantification and characterization of MP distribution in the coastal sediments of Miagao, Iloilo. Surface beach sediment samples were collected following harmonized protocols. The samples were dried and sieved to exclude particles >5 mm, then subjected to density separation using 5.5 M zinc chloride (ZnCl2; density = 1.5 g mL-1). Wet peroxide oxidation was performed to remove organic matter. Extracted microplastics (MPs) were filtered, dried, and characterized using a stereomicroscope and fluorescence staining with Nile red under ultraviolet (UV) light (365 nm) to aid visualization and identification. Quality control measures, including procedural blanks and spiked samples, were implemented. Although fibers were detected in the blanks, high recovery rates were observed for spiked polymers using ZnCl2. A total of 401 MPs were identified across the sampled transects. The average MP abundance ranged from 34 ± 18.4 to 57 ± 12.0 particles per 100 g of sediment. Fibers were the most abundant shape type, comprising 67% of the total, followed by films (17%) and fragments (16%). Fluorescence analysis under UV light (365 nm) suggested the potential presence of various polymers, including polyester (PET), polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polyamide (PA), and cotton-polyester blends (CPB). The predominance of fibers may indicate significant contributions from domestic wastewater, fishing gear, or textiles. The findings suggest that while beach cleaning may address larger debris, it appears less effective against smaller MPs, particularly embedded fibers.