Microplastics in the Black Sea sediments

Abstract In this study the occurrence, morphology and identification of microplastics in Black Sea sediments collected at different depths (range 22 - 2131 m) were determined for the first time. The study explored the advantages and limitations of using a non-invasive method consisting of filtration of the supernatant from the mixture of sediment with saturated NaCl solution followed by FTIR 2D imaging for the identification of natural and synthetic polymers. The proposed method confirmed its potential for clear identification of polyethylene, polypropylene, acrylonitrile, polyamides and cellulose-based fibers, but more difficulties when the filter substrate neighboring the fibers exhibits intense absorptions in the 1800-1000 cm-1 range. Microplastics (MPs) were determined in 83% of the investigated sediment samples. The average abundance in all samples was 106.7 items/kg. The highest pollution occurred on the North-Western shelf where the abundance of MPs was 10 times higher than in sediments from the deep sea. The most abundant plastic polymers were polyethylene and polypropylene, followed by acrylate and acrylonitrile copolymers. Polyamide and cellulose-based textile fibers were also found. The most frequent microplastic colors observed were black, blue and clear/transparent, while fibers represented the dominant microplastics in sediments.