Microplastic Content in Non-Point Source And Point Sources of Colombo And Suburbs – Experimental Study on the Impact of Seasonal Variation

Abstract

Microplastics, which can enter aquatic environments through various sources, are small plastic pieces that are less than 5 mm in length. There are two types: primary and secondary microplastics. Sri Lanka has limited studies on microplastics in inland water bodies, so this research aims to quantify the levels of microplastic pollution in Colombo's surface waters in a spatiotemporal manner. Samples were taken from Beira Lake, Dutch canal network, Talangama canal, in wet and dry seasons. Microplastic concentrations were determined using NOAA guidelines and an optical microscope. Statistical analysis was performed using IBM SPSS version 21, including One-way Anova and Pearson correlations to identify significant differences and correlations. The study found that Dutch Canal had the highest average microplastic concentration of 12.7 mg/L during the wet season, and the lowest of 4.2 mg/L during the dry season. Both Dutch Canal and Talangama canal showed significantly higher microplastic concentrations during the wet season than the dry season, while the opposite was found in Beira Lake. The statistical analysis showed significant differences between microplastic concentrations in wet and dry seasons in all three water bodies. The microplastic levels in Beira Lake were higher on the surface water during the dry season (4.32 mg/L) and wet season (13.77 mg/L) compared to point sources (4.05 mg/L and 11.68 mg/L, respectively). Furthermore, Dutch canal's point sources showed higher during the dry season (8.47 mg/L) than the wet season (11.51 mg/L) and concentration of microplastics on the surface water was higher during the wet season (5.73 mg/L) than the dry season (7.16 mg/L). Talangama canal had similar patterns to Beira Lake. The study found microplastic contamination in urban and semi-urban surface waters at levels comparable to some industrialized countries, highlighting a concerning issue.