SEILA CHEA, VOUCHCHHENG TEA, PHALY HAM, RATHBOREY CHAN AND SARET BUN
Abstract
Microplastics are emerging contaminants of increasing concern in urban aquatic environments, yet information on their occurrence in Cambodia remains extremely limited. This study provides a first baseline assessment of microplastic contamination in six major urban drainage canals in Phnom Penh, Cambodia. Wastewater samples were analyzed using wet peroxide oxidation, density separation, filtration, gravimetric analysis, and stereomicroscopic identification. Microplastic abundance was quantified based on mass and particle concentrations, while particle shape, color, and size were characterized. Physicochemical water quality parameters were also measured, and their relationships with microplastic abundance were evaluated using hierarchical cluster analysis (HCA), and Pearson correlation analysis. Microplastics were detected at all sampling locations, with an average concentration of 1.75 ± 0.31 mg/m3 and 2,118 ± 420 particles/ L. The highest abundance occurred at Prek Pnov (PPN), whereas Cherng Ek (CHE) exhibited the lowest concentration. The lower abundance at CHE may be associated with differences in local anthropogenic inputs and potential retention or settling along the drainage pathway, including wetland and wastewater treatment systems. Fragments (61.6%) and fibers (35.0%) were the dominant particle types, while transparent/white particles accounted for 57% of recovered microplastics. Most particles were relatively small, indicating their potential for continued transport through urban drainage systems. HCA grouped microplastic abundance with turbidity, total suspended solids, chemical oxygen demand, and biochemical oxygen demand. Among the measured water-quality parameters, turbidity showed the only significant positive correlation with particle concentration (r = 0.842, p = 0.036). These findings demonstrate that Phnom Penhâs urban drainage canals are important pathways for microplastic transport and provide a scientific baseline for urban wastewater management, wetland and treatment-system assessment, plastic waste management, and long-term microplastic monitoring in Cambodia.