Identification and Analysis of Microplastic Abundance in Water, Sediment, and Benthic Gastropods in the Upper Reach of the Brugan River, Batu City

Abstract

Escalating plastic waste generation in Indonesia threatens aquatic ecosystems as macroplastics degrade into persistent microplastics that contaminate water, sediment, and aquatic biota, ultimately entering the trophic food web. This study aimed to determine the abundance and characteristics of microplastics in water, sediment, and gastropods in the upper reaches of the Brugan River, Batu City, and to examine their relationship with water quality. Quantitative descriptive assessment was conducted across three sampling stations representing distinct land-use regimes. Surface water, benthic sediment, and gastropod samples were collected in-situ. Microplastic were extracted by density separation and organic matter oxidation and analyzed using optical microscopy to determine the number, size, shape, and color of the particles. Water quality parameters were also assessed such as temperature, total suspended solids (TSS), turbidity, flow rate, and flow velocity. Results indicated that microplastics were present in every compartment, with the highest concentrations in sediment at 221 particles/kg dry weight (dw), then gastropods at 187 particles/kg dw, and finally water at 3 particles/L. Microplastic particles with fragments, particles less than one millimeter in diameter, and transparent colors were the most prevalent characteristics. The Bioaccumulation Factor (BAF) was 62.33 L/kg and the Transfer Factor (TF) was equal 0.85, confirming substantial microplastic accumulation within benthic biota.