Microplastics in Weras Ganga, Bolgoda North Lake, Sri Lanka: A Reflection of Urban Waste Mismanagement

• Microplastics in water and sediments were analyzed near an Open Dump in Sri Lanka. • Over 50% of microplastics were fibers in both water and sediment samples. • Microplastics smaller than 0.99 mm dominated in water near the dump site. • Sediments served as a significant sink for microplastics in the river system. • Improved waste management is urgently needed to reduce microplastic pollution. Microplastic (MP) pollution has emerged as a significant environmental issue, especially within urban riverine systems affected by inadequate waste management practices. This research examined the spatial distribution, morphological characteristics, and polymer composition of MPs in the Weras Ganga and Bolgoda North Lake, Sri Lanka, with particular attention to the impact of the nearby Karadiyana Open Dump (KOD). Water and sediment samples were collected from 15 sites and analyzed utilizing Fourier Transform Infrared (FTIR) Spectroscopy for MP identification. The findings indicated a predominance of fibers (>50%) in both water and sediments, with the highest concentrations located near the KOD, suggesting substantial contributions from textile and synthetic waste. Polyethylene, polypropylene, and polystyrene were identified as the most prevalent polymer types, pointing to contributions from consumer packaging and industrial waste. Correlation analysis disclosed a moderate positive association between MP concentrations and physicochemical parameters such as turbidity and temperature, underscoring their role in MP transport and deposition processes. Sediment samples consistently showed higher MP concentrations than water, highlighting their function as a reservoir for MPs. The results underscore the pressing need for integrated waste management strategies, including a reduction in single-use plastics and enhancements in recycling infrastructure, to alleviate MP contamination in freshwater ecosystems. This research provides important insights into MP pollution dynamics in tropical urban rivers and stresses the necessity for specific interventions to safeguard aquatic ecosystems and public health.