Characterisation of microplastic debris in beach sediment of the coastal zone in Vietnam: A preliminary study in Da Nang

Microplastic (MP) pollution has become a global concern and a hot issue in Vietnam, especially along the coastal hydrosphere. The investigation was carried out by collecting the sediment samples from three typical urbanised beaches in Da Nang: My Khe, T20, and Son Thuy. The qualitative identification and quantitative analysis of MP samples were conducted using micro-Fourier-transform-infrared spectroscopy (μFTIR). A tailored analysis based on adaptation procedure of well-known ones was applied including 5 steps: (1) Drying and homogenising sediment sample; (2) Digestion and cleaning sediment sample; (3) MPs separation by the flotation; (4) MPs sample filtration; (5) MPs quantification and identification. The obtained data showed that the abundances of MPs at three beaches of Son Thuy, T20, and My Khe were 1,460±758, 1,799±370, and 29,232±2,577 items/kg dry sediment, respectively. MPs were classified by different sizes, in which the one with sizes being smaller than 150 μm was accounted for the highest proportion of 77.83% at Son Thuy, 87.96% at T20, and 65.91% at My Khe beach. The chemical composition of MPs with various polymers was precisely identified, in which three dominant polymers were determined as PTFE [Polytetrafluoroethylene (Teflon)], EVOH (Ethylene vinyl alcohol), and PA [Polyamide (Nylon)]. Preliminary results of MPs analysis in sediment samples of the three selected beaches in Da Nang can be interpreted as a solid basis for further investigation of MP debris in the shoreline, offshore, and other related samples towards conclusions about the sources of MP pollution in the marine environment in Vietnam’s coastal hydrosphere in future.