Abstract:
River Kelani is the most polluted river in Sri Lanka and the primary source of drinking water for millions of people in western province but very few studies have been conducted to assess its plastic pollution, which were limited to microplastic studies in the river estuary. As the global attention is increased into tackling the sources of plastic litter released into the ocean, this study was developed with the aim of identifying the microplastic (MP) pollution in Kelani River, one of the main careers of plastic waste into the Indian Ocean. The study specifically aimed to identify the MP contamination in the meandering zone of Kelani River, characterize MPs found in the surface water and identifying possible factors influencing their occurrence.
A rapid sampling process was utilized using both bulk and net sampling methods to collect 21 surface water samples. MP were extracted and categorized accordingly based on their sizes. Most recorded MP size category in bulk samples was 5mm- 2mm (55%) and 2 mm- 1mm (58%) in net samples.Plastic fragments (50.14%, 41.88%) recorded significantly high numbers and white colour (47.48%, 40.16%) was the dominant colour in both bulk and net samples respectively. The polymer types were identified using the FT-IR spectrometer (BRUKER, ALPHA II). In both samples Polypropylene and the Polyethylene were the most detected polymer types with some Polystyrene at few sites. The presence of nurdles in 5 of the 7 net samples is one of the key findings as these nurdles are similar to the nurdles from the M/V X-Press Pearl cargo ship which was destroyed completely in May 2021. The nurdles found in the samples were made from mainly polyethylene (81.9%) and polypropylene (18.1%).
While identifying that majority of the MP were with secondary origins derived from macro plastic, a situation analysis was carried out, reviewing literature, and conducting a stakeholder consultation to identify the plastic waste management situation in the country. Based on that possible sources of macro and microplastic pollution in the river were identified as littering, fly tipping and illegal dumping, poor waste management practices, industrial activities leading to improper disposal and loss, sewage debris and canal discharge, abandoned fishnets. Finally, the management recommendations were provided accordingly.
