Occurrence and Risk Assessment of Microplastics Pollution in the World’s Longest Natural Beach, Cox’s Bazar, Bangladesh

Abstract

Microplastics (MPs) are omnipresent in all ecosystems, and sediments are considered as their ultimate sink in marine environment. This study focused on the occurrence, characteristics, and risk of MPs in the beach sediments of Cox’s Bazar, Bangladesh. Sediment samples were collected from a total of 17 sites from four study areas hosting various types of aquacultural, agricultural, animal agricultural, and tourism activities during the peak tourist season. Stereomicroscopy, micro-Fourier transform infrared spectroscopy (μ-FTIR), and scanning electron microscopy (SEM) were used for qualitative and quantitative characterization of MPs. MPs were detected in all beach sediment samples, with abundance ranging from 280 to 1060 items/kg. Overall, small sizes (< 250 μm), fibrous and granular shapes, white and transparent color were the major characteristics for MPs in the beach sediments. The dominant polymer types for the MPs were PP (24.89%), LDPE (21.85%), and HDPE (18.06%). The risk of MPs in the beach sediments was quantitatively assessed with the pollution load index (PLI, 1.0–3.78), polymeric hazard index (PHI, 49.5–70.0), and ecological risk index (ERI, 54.3–232). MPs in the sediments of Kolatoli sea beach had the highest average PLI (2.32), which is indicative of significant pollution, while those in the sediments of Darianagar beach point had the lowest average PLI (1.07). The average PHI values of MPs in the four study areas (57.2 to 63.4) were within the medium range, while the average ERI values (61.1 to 135) were indicative of low to medium ecological risk. While the ecological risk of MPs in the beach sediments of Cox’s Bazar is relatively low due to the dominance of polymers with low risk scores, efforts devoted to the management of plastic waste should be made to prevent further accumulation of MPs.