Microplastics in River Sediments Around the Dhaka City: A Case Study for Occurrence and Quantification

Microplastics (MPs) pollution has gained global attention as an emerging environmental issue considering ubiquity, chemical inertness and adverse impact. Studies on MPs are mostly concentrated on the marine environment and there are very limited studies on MPs in freshwater river systems. To understand the distribution of MPs in urban rivers, this study has investigated the riverbed sediments in the peripheral rivers of Dhaka city. For the purposes, riverbed sediment samples were collected from 28 locations considering land use characteristics of the surrounding Buriganga, Turag and Balu Rivers. Riverbed sediments at sampling location were sampled from the top 10 cm sediment layer using an Ekman grab sampler and then placed into aluminum foil bags in order to avoid further contamination. MPs were extracted from the samples following a modified NOAA methodology. MPs were detected using Stereo Zoom Microscope and mass of microplastics were measured by using a digital balance. The mass concentrations of MPs particles were found to vary from 13.56 mg/kg to 430.65 mg/kg with an average value of 98.30 ± 70.72 and median value of 86.37 mg/kg in the river sediment. Comparatively higher MPs concentrations were found in highly urbanized and populated Buriganga river (Mean: 118.04 ± 108.46 mg/kg) than the Turag (Mean: 88.26 ± 31.04 mg/kg) and Balu River (Mean: 72.76 ± 33.35 mg/kg). This study gives an idea of the degree of MPs pollution in the urban rivers surrounding of Dhaka city. This study indicated that microplastics pollution in these urban river systems could be an alarming situation and measures must be undertaken to control the MPs pollution of these rivers.