Microplastic Pollution in Urban Natural Lakes of Kathmandu Valley, Nepal

ABSTRACT Although microplastic (MP) pollution in various lakes worldwide has been mostly studied, research on natural urban lakes in the Kathmandu Valley is limited. To fill this gap, the study examined the abundance and characteristics of MP in the surface waters of Taudaha and Nagdaha Lakes. Samples were collected from the shoreline of both lakes in the rainy season. It was then subjected to filtration and density separation to isolate suspected MP particles. Morphological categorization was performed using a stereomicroscope. Polymer types were confirmed through Fourier transform infrared (FTIR) spectroscopy by matching spectra with those of previous researchers. FTIR identification is conducted only on larger‐sized particles (1000 µm). Results showed that MP was detected at every site in both lakes, with concentrations from 0.4 to 3.2 particles/L in Taudaha Lake (mean 1.64 ± 0.72 particles/L) and 0.8 to 12.4 particles/L in Nagdaha Lake (mean 4.45 ± 2.90 particles/L). MP concentrations in Nagdaha Lake were significantly higher than in Taudaha Lake. Morphological analysis revealed that MP concentrations were predominantly observed as fibers (Taudaha, 96% and Nagdaha, 91%), followed by fragments and film. MP was mostly blue and pink in color. Polymer detection was limited to only two types: polyethylene and polypropylene. MP pollution in such lakes can be mainly attributed to human activities such as restaurants, cloth washing, proximity to roads, and tourism. This study provides important baseline information for the future monitoring of urban lake ecosystems and points to directions for future environmental management.