Microplastics in freshwater environment: the first evaluation in sediments from seven water streams surrounding the lagoon of Bizerte (Northern Tunisia)

Microplastic (MP) concentrations were determined, for the first time, in surface sediment of seven streams around the lagoon of Bizerte (Northern Tunisia), using a saturated NaCl flotation technique. Microplastics were categorised according to type, colour and size using a stereoscopic microscope. Results showed that all sediment samples contained MPs. The greatest MP abundance was observed at Jedara stream (6920 +/- 395.98 items kg(-1) dry weight), while the lowest mean value was 2340 +/- 227.15 items kg(-1) dry weight at Khima stream. The highest numbers of MPs were from streams near populated areas and municipal and industrial effluent discharges. Samples were made up entirely of secondary MPs mainly fibres, followed by fragments and films. The predominant colours were as follows: black>clear>white>red>blue>green>yellow for fibres, white>blue>black>red for fragments and red>white>clear>green>blue=black for films. Microplastic particles in the samples ranged from 0.2 to 5mm in length. FTIR analysis revealed that the abundant polymers were polypropylene and polyethylene. This work contributes to the growing evidence that MP contamination is widespread even in freshwater ecosystems and provides a baseline for future studies and risk assessments.