Tracing the Plastic Tide: Assessing Microplastic Abundance and Distribution along the Attanagalu River in Sri Lanka

Microplastics (MPs) are persistent environmental pollutants that pose significant threats to aquatic biota and ecosystems. Understanding the distribution and abundance of MPs in freshwater systems is crucial for developing effective mitigation strategies to address their adverse impacts. Most studies have reported MPs pollution in selected river sections or at source points along rivers. In contrast, the present study investigated the abundance, distribution, and characteristics of MPs from headwaters to the river mouth in the Attanagalu River, a freshwater system of ecological importance in Sri Lanka. Surface water and sediment samples were collected from 15 strategically selected sites along the river. MPs were detected in all sampled surface water and sediment, with abundances ranging from 1.12 to 17.45 items m⁻³ in surface water and 11.38 to 129.47 items kg⁻¹ in sediment. Spatial analysis revealed the highest MPs concentrations near the river mouth and the lowest near the river origin, indicating potential accumulation zones. All detected MPs were secondary in origin, with fibers as the predominant type, and the majority were less than 1 mm in size in surface water and sediment. Raman spectroscopy identified the polymer composition of MPs, revealing the presence of polypropylene, polyethylene, polystyrene, and polyvinyl chloride. These findings underscore the pervasive nature of MPs pollution in the Attanagalu River and highlight the need for further studies to identify pollution sources and quantify the MPs load transported by the river.