1. Introduction

Concern has been raised upon observations of high concentration of litter and microplastics (MPs) along the Greenlandic coastline (Rist et al. 2020; Mallory et al. 2021; Strietman et al. 2021). The undesirable omnipresent MPs and the scatter of plastic litter in the environment, gives rise to emerging worldwide environmental concerns, including in the Arctic (PAME, 2019). Plastic litter can physically affect marine organisms by, e.g., ingestion or entanglement, chemically by acting as an introducer, or a vector of adsorbed chemicals in the environment (AMAP, 2016; Collard and Ask, 2021), and by causing biodiversity and ecosystem disturbances (Villarrubia-Gómez et al. 2017). To combat the effects and presence of plastics in the Arctic environment, PAME (Protection of the Arctic marine Environment), a working group of the Arctic Council, has produced a regional action plan on marine litter (PAME, 2021), which includes improving onshore waste and wastewater management.

The presence of plastic in the Arctic marine waters is connected to human activities occurring both outside and within the Arctic region (Bergmann, 2022). Marine plastic litter pollution was recently documented to be significant in Greenland (Mallory et al. 2021). They investigated the marine waters and coastlines of the Arctic Canada and West Greenland and found that litter densities do not decrease with increasing latitude, that litter densities were largest within 5 km of communities, and that much of the litter near remote communities was clearly from local sources (Mallory et al. 2021). This is in accordance with an in-depth beach litter analysis in West Greenland (Sisimiut, Maniitsoq, and Qaqortoq), where marine litter was found to be mostly of local origin and consisted primarily of everyday use products and products related to fishing and hunting (Strietman et al. 2021).

It is recognized that the number of items in sea water increases with decreasing size (e.g., Herzke et al. 2021). It is, therefore, inherently difficult to compare results on numbers of particles of investigations with different cut-off sizes in the lower end (Table 1). Some general trends, however, appear to be consistent: One is the concentration of MPs from long distance sources in the Arctic Ocean (sites mentioned as potentially impacted by concentrating sea-currents in Table 1), where studies showed very high MP concentrations (Cózar et al. 2017; Barrows et al. 2018; Jiang et al. 2020; Tekman et al. 2020). The other is the increased concentration of MPs in seawater close to local sources compared to local reference sites away from sources (Table 1), as documented by Rist et al. (2020), who identified Nuuk, the capital of Greenland with 19,000 inhabitants as the primary important point source of MPs in the adjacent fjord Nuup Kangerlua, and by Herzke et al. (2021), who showed that untreated sewage from Longyearbyen, Svalbard, with only 2,000 inhabitants, emits microplastic fibers at a scale similar to a modern wastewater treatment plant serving 1.3 million persons. Several studies (Desforges et al., 2014; Barrows, 2018; Von Friesen et al., 2020) show that Arctic coastal recipients contain several size-orders higher concentrations of MPs in comparison to recipients in the Nordic region (Magnusson, 2016; Tamminga et al., 2018; Liu et al. 2023) (Table 1), while other studies show lower concentrations similar to the Nordic recipients (Rist et al. 2020; Granberg et al. 2019).

Table 1 Results reported in the literature on plastic microfibers in Arctic seawater, only synthetic MPs included.

Area	Size [mm]	MP concentration (average) [MPs m^-3]	Dominant polymer	Dominant morphology	Reference
Northwestern Pacific
Northwest Pacific, the Bering Sea, and the Chukchi Sea	>0.33	0.018-0,31 (0.13)	PET	Fibers	Mu et al. 2019
Sites potentially impacted by concentrating sea-currents
East Greenlandic Current (EGC), GL	0.1-0.5	1.2·10³ ± 0.3·10³	PES and PE	76% fibers	Jiang et al. 2020
Greenlandic Sea Gyre (GSG), GL	0.1-0.5	2.4·10³± 0.8·10³	PES and PE	87% fibers	Jiang et al. 2020
Northeast Greenland	0.08-0.5	2.4±0.8*	PE, PP, PVC	Fragments*	Morgana et al. 2018*
Arctic open ocean	>0,1	1.5·10⁴****	PES, PET	91% fibers	Barrows et al. 2018
Fram Strait, SV	0.32-	0-1.3·10³ (9.5·10¹)	PA	Excluding fibers	Tekman et al. 2020

Sites potentially impacted by local sources
Nuuk Kangerlua, GL	0.01-0.5	ca. 200-278	PES	Non-fibrous particles	Rist et al. 2020
Kongsfjorden, Ny Ålesund, SV	>0.05	3.0·10³-2.1·10⁴**	Paint	Fibers	Von Friesen et al. 2020
Ny-Ålesund, SV	0.05-5	≈ 19***	Paint, PET, PP	≈50/50 fragments, fibers	Granberg et al. 2019
Göta älv, Ryaverket recipient. SE	>0.333	0.9-10.5	-	-	Magnusson et al. 2016
Kalteva recipient, SE	>0.3	0.7-12.7	PES, PE, PVA	-	Magnusson et al. 2016
Klettagarðar recipient, IS	>0.1	2.4-5.2	-	-	Magnusson et al. 2016
Baltic Sea, South Funen, DK	>0.3	0.07		71% fibers	Tamminga et al. 2018
Kattegat, DK/SE	>0.01	17–286 (103 ± 86)	PA, PE, and PP	Fragments	Liu et al. 2023
West-coastal Vancouver Island, CA	0.0625-5	1.7·10³ ± 1.1·10³	-	Fibers	Desforges et al. 2014
Queen Charlotte Sound, CA	0.0625-5	7.6·10³ ± 1.4·10³	-	Fibers	Desforges et al. 2014
Strait of Georgia, CA	0.0625-5	3.2·10³ ± 0.6·10³	-	Fibers	Desforges et al. 2014
Arctic coastline	>0,1	3.7·10⁴****	PES, PET	91% Fibers	Barrows et al. 2018

Reference sites/Open sea
Nuuk Kangerlua, GL	0.01-0.5	67-ca. 100	PES	Non-fibrous particles	Rist et al 2020
Barentsburg, SV	0.05-5	≈25***	PCP, PP	Fragments	Granberg et al 2019
Signehamna, SV	0.05-5	≈0***	Only wool and cotton detected	-	Granberg et al 2019
Northeastern Pacific Ocean, CA	0.0625-5	279 ± 178	-	Fibers and angular fragments	Desforges et al. 2014
Water below sea-ice	>0.25	0-18	PES	Polyester	Kanhai et al. 2020
Barents Sea south and southwest of Svalbard - surface	0.25- 7.71	0.34±0.31	PES, PA, PE, acrylic, PVC, cellulose/rayon	95% fibers	Lusher et al. 2015
Barents Sea south and southwest of Svalbard - subsurface	0.25- 7.71	2.68 ±2.9	PES, PA, PE, acrylic, PVC, cellulose/rayon	95% fibers	Lusher et al. 2015
Adventfjorden, Kongsfjorden and Isfjorden. SV	0.25-5	1-2	-	-	Sundet et al. 2020
Artic Central Basin, NP	0.25-2.5	0-375 (0.7)	PES, blends, PAN, PA, PVC	96% fibers	Kanhai et al. 2018
Chukchi Sea	>0.33	0.086-0.31	PET, PA	96% fibers	Mu et al. 2019
Bering Sea	>0.33	0.035-0.26	PET, PA	96% fibers	Mu et al. 2019
West Pacific,	>0.33	0.018- 0.035	PET, PA	96% fibers	Mu et al. 2019
East Greenland – ice present	>0.5	1.0 ± 0.6	PES	97% fibres	Amélineau et al. 2016
East Greenland- ice abcent	>0.5	2.4±1.1	PES	97% fibers	Amélineau et al. 2016
Rijpfjorden, SV	>0.05	Up to 3.2·10³**	Paint	Fibers	Von Friesen et al. 2020

*High numbers of fibers in the thousand to tens of thousands items/m³ were observed but fibers were excluded due to suspected risk of contamination. **Calculated as 43% synthetic (plastic) particles, ***number estimated from bar chart, ****Calculated as 68% synthetic (plastic) particles. All results rounded to two significant figures. GL: Greenland; SV: Svalbard; SE; Sweden; DK: Denmark; IS: Iceland; CA: Canada

A national action plan to reduce plastic consumption was enacted by the Greenlandic government (Naalakkersuisut, 2021). Because wastewater in Greenland is discharged to the sea untreated, it is hypothesized that raw wastewater contributes as a local source to the marine litter (macro- and microplastics) in Greenland, as was shown for Svalbard (Granberg et al. 2019). An implementation of wastewater treatment is considered as a future point of action (Naalakkersuisut, 2021).

The aim of this project was twofold: First, to estimate the burden of plastic litter and MPs to the marine environment originating from untreated piped sewage in Greenland by sampling and investigating sewage from the two biggest towns of Greenland, Nuuk and Sisimiut. Second, based on the results, to recommend interventions to reduce plastic contamination to the sea from wastewater in Greenland.