Occurrence of Microplastics in Hijo River Sediments, Davao Region, Philippines

Abstract

Microplastic (MP) pollution is an emerging environmental concern in river systems as it can be deposited in sediments. This study assessed the occurrence, characteristics, and polymer composition of MP in the sediments of Hijo River, Davao Region, Philippines during the wet season. Sediment samples were collected from five barangays, Pandapan, Magdum, Magugpo East, Apokon, and Bucana, using random sampling along river transects. MP was extracted through wet peroxide oxidation and density separation, visually identified MP under a stereomicroscope, and characterized using ATR-FTIR spectroscopy. MP were detected in all sampling sites, with transparent particles domination in Magugpo Easr (50%), Apokon (47.27%), and Pandapan (33.33%), indicating extensive degradation of plastic films. Blue microplastics were most abundant in Magdum (32.22%) and Apokon (47.27%) due to its proximity to banana plantation, while black particles were notable in Bucana (17.89%), reflecting downstream accumulation. Film and fragment shapes were dominant across all sampling stations, followed by fibers and foam. ATR-FTIR confirmed the polymers polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), and polystyrene polymers (PS). The results demonstrate the strong influence of rainfall and runoff on microplastic transport and deposition, highlighting the need for localized waste management interventions.