The abundance of microplastics in Siak tributary sediments in the watershed area, Pekanbaru City, Riau (Case Study Sago River)

The Siak River has branches in the form of tributaries that empty and gather into one in the Siak River. One of the tributaries of Siak is the Sago River. Dense population activities along the catchment area are considered entry points for microplastics into rivers. The decrease in the quality of aquatic ecosystems is caused by the presence of plastic waste, which is further degraded and forms micro-particles called microplastics. Microplastics are plastics with measurements less than 5 mm in size. This study aims to analyze the abundance and distribution of microplastics based on 3 (three) segments (upstream, middle, and downstream) of Sago River. Analysis of sediment is carried out in several stages: drying, filtration, visual sorting, density separation (flotation), and microscopic analysis. The types of microplastics found in the Sago River were fibre, film and fragment; the pellet type was not found in this study. The highest abundance of microplastics was 14,000 particles/kg dry sediment. The types of microplastics were dominated by fragments (65.42%), fibres (18.69%), and films (15.89%). The types of microplastics identified using FTIR are polystyrene (PS), nylon, cellulose acetate (CA), high-density polyethylene (HDPE), and polyvinyl chloride (PVC). Microplastics in the Sago River sediment are supposedly originated from household waste, single-use plastic waste (plastic bags, PET bottles, food, and beverage packaging), and industry waste.