## 3 Results
### Marine Plastic Litter Identification  
Eighteen plastic fragments consisting of different colors and sizes were isolated from beach and coastal water during a beach cleaning (Figure 2a, Table 7). Through visual assessment, it was not possible to define what original product was or what type of polymer the fragments consisted of except for one fragment of a PET bottle and several fishing lines. Using the MicroNIR, we were able to quickly establish seven different polymer types on site. We were able to correctly identify the polymer type of 17 of the 18 fragments with exception of one black fragment of PVC (Table 7), which was confirmed by ATR-FTIR. Although some of the fragments were dirty and/or old (weathered), this did not affect the ability of the instrument to identify them.  
The developed method was further applied on 14 plastic fragments found in sediment in the Eurasian Arctic Ocean. These samples were measured on board the R/V \"Akademik Mstislav Keldysh\" during the 2019 Arctic expedition cruise. The size of fragments varied from 0.4 to 7 cm. All fragments polymer composition was correctly identified using the MicroNIR and consisted of eight PE fragments, four PP, one PET, and one PVC confirmed by FTIR in the laboratory following the cruise.  
In addition, 41 plastic fragments in sand samples from Norwegian beached around the Oslo jord were analyzed using MicroNIR. Average size of found items was 3.5 mm, with a size range of 1-5 mm; all fragments were relatively clean. MicroNIR analysis correctly identified the composition of 40 fragments, where PE had 25 items, PP 13, and PS two. Comparison with ATR-FTIR showed that MicroNIR analysis gave correct results for all fragments with the exception of one undefined black sample of PE.  
In Table 8, the results of analysis using both MicroNIR and ATR_FTIR of 47 plastic floating items collected by surface trawling in the Eurasian Arctic are given. Three meso plastic fragments with size 10-30 mm and another 44 items in the microplastics range with sizes from 0.2-5 mm and average 2.5 mm were examined. Although many particles were covered with organic matter, 28 particles were  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & **PET** & **PE** & **PVC** & **PP** & **PS** & **PUR** & **PA** & **PC** & **Silicone** \\ \hline
**PET** & 1.00 & & & & & & & & \\
**PE** & \(-\)0.01 & 1.00 & & & & & & & \\
**PVC** & 0.30 & 0.10 & 1.00 & & & & & & \\
**PP** & \(-\)0.07 & 0.49 & 0.40 & 1.00 & & & & & \\
**PS** & \(-\)0.29 & 0.11 & 0.07 & 0.20 & 1.00 & & & & \\
**PUR** & \(-\)0.17 & 0.01 & 0.27 & 0.35 & 0.23 & 1.00 & & & \\
**PA** & 0.05 & 0.37 & 0.53 & 0.45 & 0.14 & 0.06 & 1.00 & & \\
**PC** & 0.54 & \(-\)0.25 & 0.36 & 0.10 & 0.13 & 0.31 & \(-\)0.10 & 1.00 & \\
**Silicone** & 0.04 & \(-\)0.18 & 0.12 & 0.41 & 0.06 & 0.49 & \(-\)0.03 & 0.45 & 1.00 \\ \hline \hline \end{tabular}
\end{table}
Table 6: Cross-correlation table for method HP_1, household plastic library, RIC 1–7.  
defined correct on board the R/V \"Akademik Mstislav Keldysh\" using the MicroNIR, 17 items were not classified including to black fragments, nine thin fibers, and eight fragments with either length \(<1\) mm or extremely dirty fragments.  
Finally, 66 floating meso and micro plastic particles (average size 4.6 mm, range 1.2-12 mm) were collected by trawling in the Atlantic Ocean. Identification was only done with MicroNIR on board, and no confirmation analysis was performed. Here, 47 particles were identified of which 34 were PE, 11 PP, and two PVC. In total, 19 particles were undefined including eight black fragments, six fibers, and five small items with lengths less than 1.5 mm and a width \(<1\) mm.