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. 2022 May 20;12(1):8581.
doi: 10.1038/s41598-022-12296-0.

Spatial distribution and risk assessments due to the microplastics pollution in sediments of Karnaphuli River Estuary, Bangladesh

Md Refat Jahan Rakib #  1 , M Belal Hossain #  2   3 , Rakesh Kumar  4 , Md Akram Ullah  1   5 , Sultan Al Nahian  6 , Nazmun Naher Rima  1 , Tasrina Rabia Choudhury  7 , Samia Islam Liba  8 , Jimmy Yu  9 , Mayeen Uddin Khandaker  10 , Abdelmoneim Sulieman  11 , Mohamed Mahmoud Sayed  12
Affiliations

Spatial distribution and risk assessments due to the microplastics pollution in sediments of Karnaphuli River Estuary, Bangladesh

Md Refat Jahan Rakib et al. Sci Rep. .

Abstract

Microplastics (MPs) have become an emerging global pollutant due to their widespread dispersion and potential threats to marine ecosystems. However, studies on MPs in estuarine and coastal ecosystems of Bangladesh are very limited. Here, we conducted the first study on abundance, distribution, characteristics, and risk assessment of microplastics in the sediment of Karnaphuli River estuary, Bangladesh. Microplastic particles were extracted from sediments of 30 stations along the estuary by density separation and then enumerated and characterized using a stereomicroscope and Fourier Transform Infrared (FT-IR) spectroscopy. In the collected sediment of the Karnaphuli River estuary, the number of MPs varied from 22.29 to 59.5 items kg-1 of dry weight. The mean abundance was higher in the downstream and left banks of the estuary, whereas the predominant shape, colour, and size of MPs were films (35%), and white (19%), and 1-5 mm (30.38%), respectively. Major polymer types were polyethylene terephthalate, polystyrene, polyethylene, cellulose, and nylon. MPs were found to pose risks (low to high) in the sediment of the estuary, with the highest risk occurring at one station near a sewage outlet, according to the results of risk analyses using the pollution risk index, polymer risk index (H), contamination factors, and pollution load index (PLI). The single value index, PLI, clearly demonstrated that all sampling sites were considerably polluted with microplastics (PLI > 1). H values showed toxic polymers, even in lower proportions, possess higher polymeric hazard scores and vice versa. This investigation uncovered new insights on the status of MPs in the sediments of the Karnaphuli River estuary, laying the groundwork for future research and control of microplastic pollution and management.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Figure 1
Figure 1
The study area and sampling design in the Karnaphuli River estuary. This map was constructed using ArcGIS 10.7.
Figure 2
Figure 2
MPs abundance (a) at an individual bank and (b) overall average in sediments of Karnaphuli river estuary.
Figure 3
Figure 3
Spatial distribution of MPs among the sampling sites of Karnaphuli River estuary. This map was constructed using ArcGIS 10.7.
Figure 4
Figure 4
Proportions of MPs shape among sampling sites of right and left bank of Karnaphuli River estuary.
Figure 5
Figure 5
The overall percentage of MPs shapes found in the Karnaphuli River Estuary.
Figure 6
Figure 6
Representative images of different shapes and colors of MPs particles in sediment samples, films: (a, d and e), fragment: (i, j, l), fiber: (b, f–h), flakes: (c), line: (n, p), pellet: (k, m), foam: (o).
Figure 7
Figure 7
Proportions of MPs size range observed in sampling sites of Karnaphuli River Estuary.
Figure 8
Figure 8
μ-Fourier transform infrared (FTIR) spectra of MPs observed in the river estuary.
Figure 9
Figure 9
Percentage composition of MPs by polymer.
Figure 10
Figure 10
Proportions of MPs by colors in sampling sites of the river estuary.
Figure 11
Figure 11
(a) Principal component analysis (PCA) based on shapes of MPs, and (b) clustering of various shapes with respect to sampling sites via heat map in the Karnaphuli River estuary. This heat map was constructed using Origin Pro.
Figure 12
Figure 12
Microplastics risk (a) pollution risk index (PRI), (b) polymeric risk assessment (H), and (c) contamination factor (CF).
See this image and copyright information in PMC

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