# Microplastic Pollution on the Beaches of the Black Sea in Romania and Bulgaria
## 3 Results
### FT-IR Spectroscopic Identification of Microplastics  
Polymer quantification was conducted by applying FT-IR spectroscopy to 20 randomly selected particles identified as plastic through microscopic observation and density separation. The FT-IR spectra were matched against reference databases to identify the polymer types. The resulting percentages--twelve were polyethylene (55%), three were identified as polyamide (15%), three were identified as polypropylene (15%), and two were identified as polyethylene terephthalate (10%), while one was identified as polyurethane (5%)--reflect the relative frequency of each polymer within the analyzed subset. To support and confirm these identifications, DSC was employed to determine their melting points, and density-based flotation methods were used to pre-classify particles according to their buoyancy properties prior to FT-IR analysis. In Figures 7-11, the obtained FT-IR spectra for the identified microplastics are presented. Figure 5: Microscopic (stereomicroscope) analysis of microplastics. Figure 6: Microscopic analysis of microplastics. Figure 8: FTIR spectrum of PA6 (Nylon 6) microplastic. Figure 7: FTIR spectrum of PET microplastic. Figure 9: FTIR spectrum of PP microplastic. In the case of PET (Figure 7), the results showed bands in the regions of 1713 cm\({}^{-1}\) (C=O stretching), 1241 cm\({}^{-1}\) (C-O stretching), and 1094 cm\({}^{-1}\) (C-O stretching). The band at 720 cm\({}^{-1}\) occurred due to the presence of aromatic CH out-of-plane bending [23]. In Figure 8, the band that appears between 3298 cm\({}^{-1}\) and 3300 cm\({}^{-1}\) represents N-H stretching vibration. The bands in the range between 2932 cm\({}^{-1}\) and 2858 cm\({}^{-1}\) confirm the occurrence of CH stretching, while the stretching of C=O occurred at 1634 cm\({}^{-1}\). The bands situated in the regions of 1237 cm\({}^{-1}\), 1160 cm\({}^{-1}\), and 1097 cm\({}^{-1}\) represent the stretching vibration of the C=O ester group. The bands at 1538 cm\({}^{-1}\) and 1274 cm\({}^{-1}\) occur because of the presence of NH bending and CN stretching vibration. The bands that appear at 1464 cm\({}^{-1}\), 1372 cm\({}^{-1}\), and 1199 cm\({}^{-1}\) represent CH\({}_{2}\) bending. The absorption bands for NH and C=O bending appear at 664-687 cm\({}^{-1}\)[24]. PP (Figure 9) was indicated by the prominent presence of C-H stretching at 2950 cm\({}^{-1}\), 2915 cm\({}^{-1}\), and 2838 cm\({}^{-1}\). The spectral assignment considering the bands at 1455 cm\({}^{-1}\) and 1377 cm\({}^{-1}\) indicated types of asymmetrical vibration (\(\
u_{\rm a}\)-CH\({}_{2}\)) and asymmetrical deformation vibrations (\(\delta_{\rm a}\)-CH\({}_{3}\)). PP was identified based on the presence of absorption bands at 1167 cm\({}^{-1}\) (CH bending, CH\({}_{3}\) rocking), 997 cm\({}^{-1}\) (C-C stretching), 973 cm\({}^{-1}\) (CH\({}_{3}\) rocking, CH\({}_{3}\) bending), 841 cm\({}^{-1}\) (CH bending), and 808 cm\({}^{-1}\) (CH\({}_{3}\) rocking, C-C stretching, CH\({}_{2}\) rocking, C-CH\({}_{3}\) stretching, CH\({}_{2}\) rocking, C-C stretching, C-CH stretching) [25]. PE (Figure 10) was characterized by vibration bands at 2911-2915 cm\({}^{-1}\) and 2845-2848 cm\({}^{-1}\) (C-H stretching). The spectral assignment for PE considered bands at 1467 cm\({}^{-1}\) (\(\delta\)-CH\({}_{2}\)) and 717 cm\({-1}\) (\(\
u_{\rm r}\)-CH\({}_{2}\)) [25]. Figure 11: FTIR spectrum of PU microplastic. Figure 10: FTIR spectrum of PE microplastic. In Figure 11, the absorption bands between 3223 and 3330 cm\({}^{-1}\) correspond to the stretching vibration of the -NH group [26], while the asymmetric stretching vibration of -CH\({}_{2}\)- groups generated absorption bands at 1294 cm\({}^{-1}\), 1364 cm\({}^{-1}\), 1415-1418 cm\({}^{-1}\), 1464 cm\({}^{-1}\), 2859-2862 cm\({}^{-1}\), and 2938 cm\({}^{-1}\)[27]. The sharp peaks observed at 1726-1734 cm\({}^{-1}\) and 1701 cm\({}^{-1}\) can be attributed to the stretching vibration of the carbonyl group (C=O) in the amide.