Assessment of riverine plastic flux in Pulot River and its tributary in Sofronio Española, Palawan, Philippines

The Philippines is the world’s third major contributor to global marine plastic pollution and the biggest polluter of riverine plastics into the sea. Several rivers in Philippines including those in Palawan, the country’s Last Frontier, are assumed to be the main pathways of land-based plastic waste into the ocean. However, variations, model estimations and plastic litter’s composition among rivers remains uncertain due to lack of field data. In this regard, the quantity, temporal variations and composition of plastic flux were studied in Pulot River and its tributary in Sofronio Española, Palawan. This aims to collect field data on floating macroplastics and its composition, as well as to determine the effect of flow velocity to plastic flux. Plastic flux was measured at three different locations along Pulot River, two hourly measurements during two different time of the day was made. The results showed significant difference on the amount of plastic flux during the morning and afternoon measurements. On the other hand, plastic flux during the weekends and weekdays measurements showed no significant difference. Instantaneous plastic flux and flow velocity showed significant positive correlation at all locations for all periods of measurements except the Pulot River Bridge during morning. Predominant plastic types are food packaging, plastic bottles, and toiletries. Multilayers and mixed plastics under the “Other” category were the most abundant plastic polymer classified. These results provide new insights on variations and prevalence of plastic flux in Pulot River which may benefit future long-term monitoring efforts and plastics pollution mitigation strategies.