Macro and Micro-Litter Pollution at Crow Island Beach: Abundance and Composition

Abstract

Marine litter pollution has become an increasing environmental concern worldwide. The coastal regions near major river mouths are highly vulnerable to accumulation of litter. Crow Island Beach is located at the mouth of the Kelani River, Sri Lanka, one of the major rivers in Sri Lanka, which is the source of water for the capital, however, has no comprehensive scientific data on source identification, litter abundance, composition, and pollution status. This study was conducted in January, February, and May 2026 across 10 sampling locations along the beach to assess the pollution level at the beach. 2.5 m2 quadrat was used to collect macro-litter samples, and FTIR spectroscopy was used to perform polymer identification. To evaluate the overall pollution status of the beach, the Clean Coast Index (CCI) and Pollution Load Index (PLI) were calculated. Results indicated that domestic and household waste was the dominant source of macro-litter, and the most abundant identified polymer types were HDPE and PP. The 0.5- 5 cm range plastic debris category represented the largest proportion of collected litter, suggesting extensive fragmentation of macro-litter due to prolonged weathering. Spatial analysis was used to identify persistent litter accumulation hotspots, particularly near major accumulation areas influenced by riverine inflows. The calculated CCI value of 180.8

and PLI value of 2.2 indicated a highly polluted coastal environment. Field observations identified clinically related waste, including syringes and blood collection tubes. Increased litter accumulation during periods of rainfall and high-water levels suggest that riverine transport may contribute to litter accumulation. This

study contributes quantitative baseline data on macro- litter abundance, polymer composition, and pollution

indices for the coastal region of Colombo.