Abstract
Microplastics’ (particles size ≤5 mm) sources and fate in marine bottom and beach sediments of the brackish are strongly polluted Baltic Sea have been investigated. Microplastics were extracted using sodium chloride (1.2 g cm−3). Their qualitative identification was conducted using micro-Fourier-transform infrared spectroscopy (μFT-IR). Concentration of microplastics varied from 25 particles kg−1 d.w. at the open sea beach to 53 particles kg−1 d.w. at beaches of strongly urbanized bay. In bottom sediments, microplastics concentration was visibly lower compared to beach sediments (0–27 particles kg−1 d.w.) and decreased from the shore to the open, deep-sea regions. The most frequent microplastics dimensions ranged from 0.1 to 2.0 mm, and transparent fibers were predominant. Polyester, which is a popular fabrics component, was the most common type of microplastic in both marine bottom (50%) and beach sediments (27%). Additionally, poly(vinyl acetate) used in shipbuilding as well as poly(ethylene-propylene) used for packaging were numerous in marine bottom (25% of all polymers) and beach sediments (18% of all polymers). Polymer density seems to be an important factor influencing microplastics circulation. Low density plastic debris probably recirculates between beach sediments and seawater in a greater extent than higher density debris. Therefore, their deposition is potentially limited and physical degradation is favored. Consequently, low density microplastics concentration may be underestimated using current methods due to too small size of the debris. This influences also the findings of qualitative research of microplastics which provide the basis for conclusions about the sources of microplastics in the marine environment.
Highlights
Since 1950, global plastic production has increased from 1.5 to 311 million tonnes in 2014 (Plastics Europe 2015)
Fibers were the predominant type of microplastics in marine bottom sediments
Comparison of observed regional differences in microplastics pollution is difficult due to the lack of unitary microplastics size definition, different sampling methods, filter/mesh size used in the analysis, Fig. 2 Microplastics extracted from marine bottom sediments and beach sediments of the Southern Baltic Sea. a Red fiber (GA station at calm sea state). b Blue fiber (ZN2 station). c Blue irregular fragment (KO station).d Red fiber (GA station at calm sea state)
Summary
Since 1950, global plastic production has increased from 1.5 to 311 million tonnes in 2014 (Plastics Europe 2015). Because of increasing production of synthetic polymers and their low biodegradability, plastic pollution has become a serious environmental problem. It has been estimated that every year 4.8–12.7 million tonnes of plastic debris enter the marine environment (Jambeck et al 2015), and this amount will probably increase by an order. It is widely accepted that plastic items smaller than 5 mm are considered as microplastics (MSFD Technical Subgroup on Marine Litter 2013). Microplastics can enter the marine environment as primary or secondary pollution. Primary microplastics are polymers manufactured in micro-scale, e.g., cosmetics (Zitko and Hanlon 1991) and medicine (Patel et al 2009) components or raw materials used for plastic production (Turner and Holmes 2011). Secondary microplastics are products of physical (mechanical) and photochemical degradation of bigger plastic fragments (Zbyszewski et al 2014; Galgani et al 2015; Koelmans et al 2015)
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