Comparison of microplastic abundance and characteristics in rural rivers : Hamada River, Japan and Mlese River, Indonesia

Abstract

Microplastics have negative chemical and ecological effects on aquatic biota and humans. However, few studies have explored the abundance of microplastic in rural river. This study aims to compare of the abundance of microplastic, size distribution, color, and polymer types in rural river of Japan and Indonesia. Data were collected at one of river point in the in the Hamada River, Japan during dry season and Mlese River, Indonesia during rainy season. The sampling and analysis methods were in accordance with the Japanese Riverine Microplastic Survey Guidelines, the microplastics in the range of 500-5,000 μm were determined by optical microscopy and FTIR spectroscopy. Film shaped, size 1,000-3,000 μm, and polymer type polyethylene and polypropylene were the majority of the identified microplastics both in Hamada River and Mlese River. Meanwhile, the dominated colors were gray for Hamada River and transparent for Mlese River. The abundance of microplastic were 5.5×10⁻² particles/m³(discharge:0.032 m³/s) for Hamada River and 2.2×10⁻³ particles/m³ (discharge:8.12 m³/s) for Mlese River. A low abundance of microplastic in Mlese River is a result of the high flow velocity and discharge. Moreover, that shows Hamada River’s microplastic is 26 times greater, this indicates that Japan uses more plastic products to support crop production compared to Indonesia and influence the river water pollution by microplastics.