Critical analysis, characterization, and treatment of microplastics in the peripheral rivers of Dhaka city: Buriganga and Turag

Abstract

Microplastic pollution is an emerging global concern due to its persistent nature, toxic effects, and complex detection techniques. This study analyzed microplastic (MP) abundance in water and sediments of Buriganga and Turag Rivers in Dhaka city, revealing severe contamination in Buriganga (dry season: 26.98–374.84 MPs per L water, 11 360–134,330 MPs per kg sediment; wet season: 5.17–9.07 MPs per L, 2060–10,225 MPs per kg). Turag exhibited lower pollution (dry: 3.02–24.76 MPs per L, 1430–6720 MPs per kg; wet: 1.93–14.57 MPs per L, 1255–6590 MPs per kg). Dominant MPs comprised fragments/films/fibers, with sizes <300 μm (33–75% prevalence) and white particles (26–35%), supplemented by red/black (Buriganga) and brown/black (Turag). Polymers were dominated by polyethylene (75–83% occurrence) and polypropylene (83%), with polystyrene in 4–8% of samples. Moreover, the presence of toxic heavy metals, e.g., Cr, Mn, Pd, Cd, Pb, was observed on the surface of MP samples. Hierarchical Cluster Analysis revealed distinct groupings of sampling stations based on the concentration and weight of MPs, highlighting spatial variations in MP distribution across rivers and seasons, while the Pollution Load Index confirmed moderate risk across both rivers, peaking at 4.11 (water) and 4.02 (sediment) in the dry season of Buriganga. Electrocoagulation (Al–Al electrodes, 15 V) achieved >99% MP removal within 150 minutes, following second-order kinetics with voltage-dependent efficiency. These findings underscore MPs as complex hazards to the environment, urging prioritized source control, scaling of remediation techniques, and standardized monitoring for urban river systems.