Microplastics (MPs) with the size of 1 μm-5 mm are pollutants of great concern ubiquitously found in the environment. Existing efforts have found that most of the MPs present in the seas mainly originated from land via riverine inputs. Asian rivers are known to be among the top in microplastic emissions. However, field data are scarce, especially in Malaysia. This study presents the distribution and characteristics of MPs in the surface water of two major river basins of Malaysia, namely Langat River (West Coast/Straits of Malacca) and Kelantan River (East Coast/South China Sea). Water samples were collected at 21-22 locations in Kelantan and Langat rivers, covering the river, estuary and sea. MPs were physically classified based on sizes, shapes, colours and surface morphology (SEM-EDS). The average of 179.6 items/L and 1464.8 items/L of MPs had been quantified from Kelantan and Langat rivers, respectively. Fibre (91.90%) was highly recorded at Kelantan, compared to Langat whereby both fibre (59.21%) and fragment (38.87%) were prevalence. Anthropogenic activities and urbanised areas contribute to high microplastic abundance, especially in the Langat River. Micro-FTIR analysis identified 14 polymers in Kelantan River, whereas 20 polymers were found in Langat River. Polypropylene, polyethylene, polyethylene terephthalate, nylon, phenoxy resins, poly(methyl acrylate), poly(methyl methacrylate), polystyrene, polytetrafluoroethylene, polyurethane and rayon were discovered in both rivers, although only polyethylene was significant (>1 ppm) when further analysed using pyrolysis-GC/MS. Correlation analysis and multiple linear regression were used to explain the relationship between water quality and MP abundance, suggesting only turbidity was positively significant to the microplastic occurrence. This comprehensive study is first to suggest a full-scale monitoring protocol for MPs in Malaysian riverine system and is significant in understanding MPs abundance in correlation to in-situ environmental factors. Consequently, this will allow the right authorities to develop mitigation strategies to address riverine plastic pollution in major river basins in Malaysia and the South East Asia.
Plastic pollution in aquatic ecosystems has become a critical global environmental challenge, threatening biodiversity, water quality, and human health. This study investigates macroplastics distribution and characterization in the highly polluted Klang River, Malaysia, and proposes a protocol to compute total macroplastic yield in the river basin. A total of 240 macroplastic items were collected over a 20-km stretch from the river mouth inland, with an average of 0.91 ± 0.80 g/item (dry weight). Scanning Electron Microscopy revealed that the macroplastics had weathered slowly in the environment, potentially breaking down into smaller microplastic particles. Biofilms and dead phytoplankton were observed on the plastic surfaces, suggesting that plastic debris may act as vectors for other pollutants. The study used SWAT modelling to simulate physical processes in the Klang River Basin and compute pollutant loads through a loading computation procedure. A macroplastic rating curve was created using river discharge, macroplastic loadings, and associate parameters to estimate plastic loading in the river. The fitted equation models macroplastic loading as a function of river discharge and width, expressed as: log(y) = 1.88216-7.36528log(x) - 4.00491log(x2). Here, log(x) represents the ratio of river discharge to river width, while log(y) denotes macroplastic loading adjusted for sampler width and river width. Results indicated that macroplastic transport in the river system is linked to flow rates and sediment yield, which vary due to topographical factors, with an estimated macroplastics yield in the Klang River Basin of 11,600 kg/day. The findings suggest that a river-specific monitoring programs should be conducted to generate comprehensive datasets, integrating both macroplastics and microplastics abundance, which can be utilized for projecting plastic emissions from Malaysian rivers and comparing data with other river basins in the Southeast Asia.