Analysis of microplastics in the fjords of Tunu (East Greenland)

Microplastics (MPs) were surveyed in the fjords of Tunu (East Greenland), contributing important information to the scarce database on plastics in the Arctic. A total of 18 subsurface water samples were collected at eight stations along the northeast coast of Kalaallit Nunaat (Greenland) in August 2022. Sampling of the MPs was optimized and validated using traceable metal-doped model MPs. Recovery rates of the metal-doped MPs for validation of the sampling process using the Geesthacht Inert MP Fractionator were 78.7 ± 0.7 % (1 SD, n = 3) for a mixture of biofilm-coated Polyethylene terephthalate (PET) and Polylactic acid (PLA) particles. Samples were analyzed using laser direct infrared (LDIR) imaging. The reported MP number concentrations ranged from 1.0 ± 0.8 L^-1 (1 SD, n = 3) to 12 ± 4 L^-1 (n = 4) in the size range of 20-500 μm. The highest concentrations were observed at the mouth of the Kangertittivaq (Scoresby Sound), in the vicinity of the settlement Ittoqqortoormiit. PET was identified as the predominant polymer type, representing an average share of 96 %. PLA featured the second highest abundance, accounting for an average 1.6 % share. The analysis of conductivity-temperature-depth profiles revealed no significant evidence of MP input from glacial runoff. The results demonstrate the critical importance of collecting replicate samples, as short-term fluctuations in MP concentration and composition exceeded potential differences in their spatial distribution.