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Article

Influence on the Result by Abrasion on Filter Casings, Tested in the Environment in Finnmark, Norway

by
Fabio Manna
,
Michel Mues
,
Clara Wiebensohn
,
Maja Dukat
and
Andreas Fath
*
Institute of Applied Biology, Faculty of Medical and Life Sciences, Hochschule Furtwangen, 78054 Villingen-Schwenningen, Germany
*
Author to whom correspondence should be addressed.
Microplastics 2025, 4(1), 14; https://doi.org/10.3390/microplastics4010014
Submission received: 1 August 2024 / Revised: 3 January 2025 / Accepted: 3 February 2025 / Published: 11 March 2025
(This article belongs to the Collection Current Opinion in Microplastics)
Browse Figures
Versions Notes

Abstract

:
The purpose of this study is to determine the plastic wear of the cartridge filter casing 01WTKF (Wolftechnik Filtersysteme GmbH & Co. KG, Weil der Stadt, Germany) when exposed to sand, sediment, and ice at temperatures below 0 °C, both in laboratory and field conditions. Furthermore, this study aims to discuss whether previous studies conducted with the model 01WTKF may suffer significant errors due to abrasion. The freshwater samples were collected in Finnmark, Norway. These samples were filtered using a cartridge filtration method and the 01WTKF filter casing, which features lids made of polypropylene (PP) and bottom parts made of styrene–acrylonitrile copolymer (SAN) or PP. The samples were analyzed for microplastic (MP) cross-contamination by comparing the results of the model 01WTKF to those of the stainless-steel-based model 01WTGD. Laboratory and environmental samples were examined using FT-IR spectroscopy. The results indicate that wear occurs for ice, sand, and sediment. Abrasion significantly increased the overall PP concentration in the environmental samples, introducing an error of 858 ± 516 N m−3 MPs to 2453 ± 92 N m−3 MPs. By contrast, no wear was detected for the SAN-based bottom part. For the PP-based lids, only 92 ± 83 N m−3 MPs were identified. Therefore, the use of PP-based bottom parts and lids is not recommended at temperatures below 0 °C. Additionally, studies utilizing the model 01WTKF should be reviewed and re-evaluated to ensure the accuracy of the obtained data.

1. Introduction

Microplastics (MPs) are divided into three categories: those with a size less than 5 mm in diameter, even smaller MPs with less than 1 mm, and particles under 0.1 μm, known as nanoplastics [1]. Due to sunlight, changes in temperature, wind, and physical forces, plastics break down into progressively smaller particles when exposed to natural elements [2]. The transportation of MPs occurs over vast distances through the atmosphere, and it is primarily washed out by snowfall, accumulating in the sub-Arctic and Arctic regions. [3,4]. Figure 1 illustrates this process further.
Finnmark is the northernmost region of Norway. Different types of terrain can be found there, from rugged coastlines and deep fjords to vast tundra and high mountains [5]. The Tanaelva River stretches over 283 km, including the source river Kárášjohka, reaching 369 km [6]. It empties into the Barents Sea with an annual discharge of approximately 5944 × 106 m−3 in 2016 [7]. The flow rate varies significantly throughout the year, with 46 m3 s−1 increasing in February, by a factor of more than 28 to 1327 m3 s−1 in May of 2016 [7]. The Tanaelva is a central part of life and the economy in Finnmark, known for its salmon fishing and spawning grounds [8,9]. Not only fish but also bird species, especially wetland birds, use the area as a breeding ground [9]. Among others, the Arctic fox, the white-tailed eagle, various seal species, and the endangered wolverine inhabit this region [9]. Reindeer herding is a distinctive trade reserved for the Sami, the indigenous people of Finnmark. They have lived in this region for centuries and have a deep understanding of nature [9].
The potential dangers caused by MPs are numerous [10,11,12,13,14]. MP particles pose hazards to human health as well as to terrestrial and aquatic organisms [15,16,17,18,19,20,21]. MPs have been detected in human stool [22], blood samples [23], and lung tissue [24]; furthermore, they are suspected of being able to penetrate the placenta [25]. In fish, ingested MPs have been found accumulating in the gastrointestinal tract and obstructing digestive processes [26]. Several disorders associated with MPs have been documented, including nutritional deficiencies, inhibited growth [27], compromised immune function, altered swimming behavior, reproductive impairment, and diminished survival rates [28].
A further risk posed by MPs is their role as vectors for persistent organic pollutants (POPs) such as halogenated contaminants, hormones, heavy metals, and other hydrophobic substances [29]. A feeding trial investigated the effects of MPs as vectors for POPs on Atlantic salmon (Salmo salar). Enhanced bioaccumulation of POPs within lipid-rich tissues was ascertained more so than conditions lacking MP vectors [30]. Through such vectors, POPs bioaccumulate within the food chain [31]. Common sources of MP vectors in the environment include fibers from clothing during washing, industrial processes, construction sites, agriculture, fishing, military activities, road erosion, and tire wear [32].
A unique type of wear is hydroabrasion; suspensions of liquids and solids cause abrasion on surfaces through microcracking, especially in fluid flow systems such as pumps and water turbines [33]. The direction and shape of the impacting particles significantly influence the degree of wear [33]. This also depends on the material being strained, which can vary from stone to ceramics, metal, glass, or plastic [33]. The latter is heavily influenced by temperature [34]. Each plastic reacts differently to temperature changes; for example, thermoplastics, consisting of semi-crystalline plastics like polypropylene (PP) and amorphous plastics like styrene–acrylonitrile copolymer (SAN) [34]. The impact strengths of SAN and PP differ immensely; this becomes even more evident at sub-zero temperatures [35,36]. The low impact strength of polypropylene (PP) at subzero temperatures suggests the possibility of hydroabrasion on PP-based surfaces when impacted by sediment or ice. This could lead to cross-contamination through abrasion in the filtration system and, consequently, result in inaccurate measurements.
Environmental sampling equipment must withstand properties such as potential wear through abrasive materials or temperatures below 0 °C, especially in the case of contamination [37]. But, exactly such conditions can be met in environments like that of the Norwegian region of Finnmark [5]. For surface water collection, the cartridge filtration systems from Wolftechnik Filtersysteme GmbH & Co. KG are frequently used. A total of 16 publications were found using cartridge filtration systems by Wolftechnik Filtersysteme GmbH & Co. KG for sampling [38,39,40,41,42,43,44,45,46,47,48,49,50,51,52]. Two of these publications mentioned the usage of the model 01WTKF (Wolftechnik) [38,39], ten did not state which model was specifically used [40,41,42,43,44,45,46,47,48], and four studies stated the utilization of stainless-steel filter casings [49,50,51,52]. No publications were found addressing whether wear occurs on the model 01WTKF made from PP and SAN. For this reason, the potential wear on the filter casings must be determined to confirm the accuracy of the previous results obtained using the model 01WTKF. This study aims to investigate if wear on the filter casing model 01WTKF could occur during sampling in the northern polar region and provide a characterization of the MPs collected from terrestrial surface water in Finnmark. No publications have mentioned surface water analysis in relation to MPs in Finnmark yet.

2. Materials and Methods

2.1. Database Samples

To ensure the accurate identification of the plastics of interest through FT-IR spectroscopy, specific samples of the lid made from polypropylene (PP) and two different bottom parts, one made from PP and one from styrene–acrylonitrile copolymer (SAN), were added to the database. Only specific hits for these plastics were considered as abrasion through the process; the same criterion applied to samples evaluated for contamination.

2.2. Cartridge Filtration System

For cartridge filtration in both laboratory and environmental settings, a hose was extended into the water to a depth of approximately 10 cm, connected to a diaphragm pump (12.5 LPM, 2.5 bar, bypass, 12 V, Flojet, Flojet Corporation, Milton Keynes, England), which fed into the filtration unit. To prevent large debris from entering the pump, a mesh basket with a pore size of 5 mm was attached to the end of the hose. After passing through the filtration system, the water was discharged back into the original water source. The cartridge filter systems used were provided by Wolftechnik Filtersysteme GmbH & Co. KG and were equipped with a 10 μm stainless-steel filter element. Three different kinds of casings were compared: the model 01WTKF with a lid made from PP and a bottom part made from SAN or PP, while the model 01WTGD had both parts made from stainless steel. The latter served as a negative control.

2.3. Sealing and Transportation of Environmental Samples

To store the samples, each cartridge remained in the filter casing and was sealed with plugs wrapped in Teflon tape to ensure a secure seal. The entire filter casing was enclosed in bubble wrap to ensure safety during transportation. The samples were placed in a hard-shell case, which was then filled with additional bubble wrap and paper to minimize movement during the flight. To detect potential contamination during airport luggage checks, the bottom parts and lids were connected by breakable seals to indicate contamination.

2.4. Environmental Sampling

Due to the maximum transportation weight and the difficult situation of transporting samples by flight, there was only space for two SAN, two PP, and three stainless-steel casings. For the sampling procedure through each setup, 200 L of water was filtered; the duration remained constant at 20 min per cartridge. In total, seven cartridge samples were taken.
The sampling locations in Finnmark, Norway were accessed by dog sledding on a guided expedition (by Nordgehen GbR, Kürten, Germany). The locations at Dunkrattelva and Sommervannet were not testable. At Dunkrattelva, weather conditions prevented sampling due to overvann, a term referring to precipitation and meltwater that flows off dense surfaces. At Sommervannet, there were technical issues with the setup; therefore, the samples Tanaelva 2 and Bergebyelva were collected instead.
Samples were taken from three different rivers and four distinct locations (Table 1), the GPS coordinates are available (Table S1). The table shows which casings were used at each location. Consequently, this sample was not analyzed. Ice drilling prior to sampling was only performed at Dunkrattelva. However, due to the aforementioned issues, this sample was not taken. Therefore, no sampling procedure at any location was influenced by artificially created ice crystals.

2.5. Laboratory Setup and Contamination Mitigation

The goal of the laboratory setup was to simulate water movement and particle dynamics particles in it. Therefore, a stainless-steel barrel was used, and the mortar mixer PRO-RG 1400 Toolson (Bauhaus, Belp, Schweiz), equipped with the Turbo-Mixer LX (Collomix, Gaimersheim, Germany), was added on top of the barrel. The speed was adjusted to achieve a flow rate of 46 m3 s−1 in the sampling area where the hose was extended. This was conducted to match the average flow rate of the Tanaelva in February [7]. Due to the requirement of maintaining a temperature below or around 0 °C, the setup was placed in a garage during winter and the temperature was measured with a mercury thermometer to account for potential discrepancies between laboratory and environmental conditions, ensuring that any significant differences in the results could be properly evaluated and explained. To ensure air purity, a CA-510Pro Smart (Clean Air Optima, Nordhorn, Germany) was operated one hour before sampling. To pre-test for airborne contamination, the barrel was filled with water to a height of 30 cm, and five samples were collected over the course of one hour: one at the start and one every 15 min thereafter. Before each cartridge sample was taken, the barrel was cleaned. After preparing the suspension for each sampling process, the used water was prefiltered using the stainless-steel filter casing model 01WTGD and a 10 μm stainless-steel filter to ensure that impurities larger than 10 μm were not traceable in the analytics.

2.6. Laboratory Sampling

For the sampling procedure, each cartridge filtration setup was tested with each water suspension. Through each setup, 200 L of suspension was filtered. The duration lasted for 20–30 min per cartridge. In total, 18 cartridge samples were taken, three for each sampling setup and suspension.
For the suspensions, the barrel was filled with water to a height of 30 cm, submerging the mixer 10 cm into the water, which amounted to approximately 70 L of water. Due to possible temperatures below −30 °C in Finnmark [7] and a sampling duration of 20 to 30 min, it was necessary to perform multiple drillings to prevent the hose from freezing to the surface. Thus, the surface was continuously covered with ice crystals resulting from the drilling process. This was simulated during sampling with 10 kg of crushed ice on the surface. For sampling, the mixer was started at a quarter of maximum power until a somewhat slushy mixture was created on top. Then the cartridge sample was taken while the mixer was kept running. For each sample, a new suspension was created. To simulate conditions similar to those during environmental sampling in Finnmark in February [7], a flow rate of 46 m3 s−1 and a distance of 10 to 20 cm between the hose and the riverbed were chosen. Based on experience, the sediment remaining in the filter casing after sampling was considered to accumulate to 20 to 30 g. To achieve this 10 kg of quartz sand (BEHA), grain size 0.63 to 1.0 mm, was added to the barrel along with 70 L of water.

2.7. Sample Preparation

Alkaline digestion was used to reduce biofilms on polymer particles and other organic materials. Density separation was employed to isolate non-digestible components. Although laboratory samples did not need alkaline digestion, they were treated the same way as environmental samples to ensure higher comparability.
To remove organic components, the samples were treated with a 5 molar sodium hydroxide solution for 7 days. The samples were then filtered through a stainless-steel mesh with 10 μm pores. The stainless-steel mesh was placed into an ultrasonic bath (Palssonic, Heraeus, Hanau, Germany) with 100 mL sodium tungstate solution (Na2WO4, ROTH) for three minutes to dissolve the filter cake. The sodium tungstate solution had a density of 1.6 g mL−1 and was used as the medium for density separation. The solutions were allowed to stand for 7 days in a separating funnel. The separated fraction with a density >1.6 g mL−1, approximately 80%, was drained and discarded. The supernatant was placed onto a 10 μm stainless-steel mesh and washed with 1 molar HCl solution to remove excess Na2WO4 including its precipitates. The filter cake was then dissolved in 100 mL of Milli-Q water and transferred to a 0.2 μm aluminum oxide filter (Whatman Anodisc, Cytiva, Marlborough, MA, USA).
A solution with 60 μm polymethylmethacrylate beads (PMMA, Microbeads AS, Skedsmokorset, Norway) at a concentration of 2500 beads L−1 was prepared using a dilution series with Milli-Q water and provided by the laboratory staff. To partially simulate an environmental sample, the solution was mixed with 5% quartz sand (BEHA). This solution was used as a positive control and was sampled three times. The original concentration was unknown to the experimenter until after analysis.

2.8. Analytic Methods

The water samples were analyzed using FT-IR spectrometry (Spotlight 200i FT-IR Microscopy System and Spectrum V10.6.2 software by PerkinElmer). Five squares were chosen on each aluminum oxide filter, and all particles within each square were analyzed. The same spots were always selected for the squares to avoid operator bias. The area of each square was set to 750 μm by 750 μm. The total area of the filter measured 278,182,060.4 µm2. Using the software and the polymer spectrum database, the MPs were identified. Only hits with a correlation of >70% were counted as positive correlations. In the final step, the results were extrapolated to the entire filter.
The laboratory (sand and ice) samples and environmental samples were compared to each other in terms of their mean concentration of MP cross-contamination caused by abrasion from the PP-based lids, as well as the PP-based and SAN-based bottom parts. Additionally, the particle size distribution of the cross-contamination particles was analyzed. Furthermore, the environmental samples obtained using the model 01WTGD were examined for their characteristics, including particle composition, particle size distribution, concentration, and particle shape. Subsequently, the information on actual environmental pollution and the measured cross-contamination were combined. The cross-contamination was added to the actual pollution data and compared with the actual pollution alone to assess whether cross-contamination introduces a significant error to the results in terms of accuracy.
The results were adjusted for airborne contamination and the negative control. For means with a sample size of three or more, the error bars are presented as confidence intervals achieved with bootstrapping. For means with a sample size of less than three, the standard deviation is portrayed. The significant difference was calculated using the Kruskal- Wallis Test and the Dunn Test for post hoc comparisons with a significance level of α = 0.05.

3. Results

3.1. Abrasion on the Cartridge Filtration Casing 01WTKF

3.1.1. Airborne Contamination During Laboratory Sampling

The results show no airborne contamination during sampling. The FT-IR spectrometry detected no microplastics (MPs) specific to the lid or to any of the bottom parts. Therefore, in terms of the results, airborne contamination is negligible. Samples were taken in triplicate.

3.1.2. Negative Control

The negative controls were carried out with the cartridge filtration casing 01WTGD and in triplicate. All samples taken show no specific contaminations. Therefore, contamination through the suspensions and environment is ruled out.

3.1.3. Positive Control

Positive controls were performed in triplicate during sample preparation. Table 2 shows the traceability of PMMA beads for the ice and sand suspensions, as well as for the environmental samples. The absolute and relative errors show low values, indicating precise measurements. The low standard deviations suggest high accuracy. The coefficient of variation (CV) is an indicator of the relative dispersion. The results for the CV reflect the reliability of the measurements. All of this indicates high accuracy in the results. No significant differences were confirmed for the positive controls.

3.1.4. Abrasion on Lids and Bottom Parts

Figure 2 presents the results for the laboratory samples. All results are within the same order of magnitude. However, a significant difference (p < 0.05) is observed between the ice and sand laboratory samples. Ice caused a significantly greater straining effect on the PP-based bottom part compared to sand. The results for the environmental samples are closer to the sand samples than to the ice samples, suggesting greater exposure to sand than to ice. The styrene–acrylonitrile copolymer (SAN) samples are not included in the graphic because no specific wear was detected. Abrasion on the lids ranged from one to two particles per filter, accumulating to 92 ± 83 N m−3.

3.1.5. Contamination in Environmental Samples Introduced by Abrasion on Filter Casings

By subtracting the PP cross-contamination from the total measured PP particles, the actual PP contamination was determined. The levels of PP-based MPs detected were three times higher due to cross-contamination caused by abrasion shown by Figure 3. Comparing the total PP contamination with the actual PP contamination revealed a significant difference (p < 0.05) in PP levels. This result highlights a substantial error in measurement accuracy caused by cross-contamination. The temperature measured at Tanaelva was −3 °C, while at Bergebyelva, it was −5 °C.

3.1.6. Particle Size Distribution for Particles Introduced by Abrasion on Filter Casings

Figure 4 shows the particle size distribution for the PP-based bottom parts. Nine percent of the particles in environmental samples were found to be <1 mm and >50 µm, corresponding to 152 particles. This results in 1538 particles being <50 µm and >10 µm, suggesting greater abrasion for particles <10 µm. Consequently, cross-contamination of particles <10 µm during sampling would be discharged into the environment due to the mesh having a pore size of 10 µm. Depending on how many additional particles <10 µm are released, the total number could range between 2000 particles for linear growth and 15,000 particles for exponential growth over a duration of 20 to 30 min.

3.2. Microplastic Contamination in Finnmark, Norway

Figure 5 and Figure 6 present the results collected using the stainless-steel-based cartridge model 01WTGD, summarizing the microplastic (MP) characteristics: polymer composition, particle size distribution, particle shape, and overall particle concentration. The highest pollution was found for Tanaelva 1 with 2873 ± 265 N m−3, and the mean MP concentration across all locations is found to be 1900 ± 779 N m−3 (Figure 5C). This is important for determining whether abrasion on the filter casings significantly influences the results Figure 3 and Figure 6 describe the shapes of the environmental samples. With 81%, the vast majority are fragmented.

4. Discussion

4.1. Hydroabrasion on the Cartridge Filtration Casing 01WTKF

This study aims to determine whether the cartridge filtration casing model 01WTKF is suitable at temperatures below 0 °C. Therefore, it must be clarified whether hydroabrasion occurs on the casing during sampling. The abrasion levels for polypropylene (PP) range from 2255 ± 142 N m−3 for ice to 1425 ± 107 N m−3 for sand in laboratory tests. For the locations of Tanaelva 1 and Bergebyelva, a mean of 1690 ± 290 N m−3 was detected. No abrasion was found for styrene–acrylonitrile copolymer (SAN). Abrasion levels of 92 ± 83 N m−3 were detected for the PP-based lids. The results clearly show that wear occurs on the filter casing and raise the question posed in this article: does this represent a significant measurement error? As shown in Figure 3, cross-contamination influenced the results, revealing a significant difference (p < 0.05) compared to actual environmental contamination. Consequently, the measurements are significantly wrong.
Jander et al. [39] suspected potential wear on the cartridge model 01WTKF based on grinding sounds noticed during sampling. They found multiple samples with elevated PP levels compared to their other samples and identified the PP as the same material used for the cartridge casing. One of these samples, taken at Chur, Switzerland, came from shallow water with turbulence, which could contribute to an increased concentration of straining particles. The data on cross-contamination at temperatures below 0 °C support this suspicion by providing evidence of abrasion on the PP-based cartridge. However, Jander et al. [39] did not provide any temperature data. Moreover, numerous factors influence abrasion levels, such as the type, shape, hardness, grain size, and concentration of the strained material, as well as physical parameters, duration, and velocity [33]. With Jander et al. [39], whose sampling took place in August and September, one can note that temperatures below 0 °C are possible, though not very common. This raises the possibility that the model 01WTKF may be unsuitable not only at subzero temperatures but also at higher temperatures, which warrants further investigation. In order to make conclusions on other studies, more data should be gathered regarding specific temperatures during sampling, time and date, and which cartridge system was used. If the FT-IR samples are still available, an analysis comparing the specific PP used could be performed.
A significant difference (p < 0.05) is found between ice samples and sand samples Figure 2. This difference may stem from the varying properties of ice and sand particles: sand is generally harder than ice [53,54]. In this context, it is important to note that abrasiveness is defined more by sharpness than by particle hardness [55]. Under certain conditions, ice can form very sharp edges [56], whereas sand edges become increasingly blunt due to sedimentation and erosion processes [57]. Considering this and the results (Figure 2), the environmental samples were more exposed to sand than to ice crystals, but do not show a significant difference compared to either type.
The high potential for cross-contamination by particles <10 µm during sampling, as shown in Figure 4, poses an unnecessary risk for pollution discharging into the environment during sampling and should be minimized whenever possible.

4.2. Microplastics in Surface Waters in Finnmark, Norway

Although not directly related to the topic of hydroabrasion, the environmental sampling conducted in Finnmark, Norway, was the first in the region to analyze microplastics (MPs) in surface water and will be discussed as additional interesting information.
Even though the Tanaelva and its source river Kárášjohka are much less populated and industrialized [58] than other European rivers like the Danube [59] or the Rhine [60], the MP concentration in Finnmark, Norway, exceeds those of other surface water MP analyses in European rivers, surpassing most sampled areas by three orders of magnitude [61]. Therefore, other sources must be considered, such as rain and snowfall, as reflected in Figure 1. Clouds on Mount Fuji in Japan were tested for MP pollution in 2023 and found to have concentrations ranging from 6.7 × 103 N m−3 to 1.4 × 104 N m−3 [62], showing concentrations more similar to the findings in the Finnmark region. Snow samples in the Arctic polar region of Fram Strait and Svalbard even show concentrations up to 1.4 × 107 N m−3 [4]. The snow in Finnmark hasn’t been tested yet, but one may assume similar amounts of MPs introduced by snowfall, given that Finnmark is part of the polar region. Additionally, the other MP characteristics identified show a great resemblance to MP characteristics analyzed in these studies [4,62].
What do the measured MP concentrations of up to 2873 ± 265 N m−3 imply for the local Sami population and wildlife? Although the specific consequences of the identified pollution on various species in different environments cannot yet be determined, numerous studies have documented a multitude of impairments caused by MPs [16,17,18,19,20,21]. These effects range from minimal disturbances of biological systems to severe consequences, including mortality [11]. In fish, ingested MPs have been shown to accumulate in the gastrointestinal tract, causing obstructions to digestive processes [26]. This leads to anatomical and functional changes, often accompanied by developmental issues [63,64]. Other common effects include oxidative stress, reduced mobility, disruption of gene expression, and damage to reproductive organs [65,66,67]. Given that fishing, alongside reindeer herding, is one of the most significant economic activities for the Sami [9], the threat posed by MP pollution to the ecosystem consequently jeopardizes their livelihood.
The samples analyzed represent a preliminary count from three locations: two in Finnmark and one in Nesseby. It must be noted that MP contamination varies with time and season, particularly in water bodies where levels and discharge fluctuate, such as the Tanaelva [6,7]. Despite these variations, the results highlight the abundance of MPs in Finnmark. Other studies have demonstrated that MPs enter the environment through snowfall, where they accumulate in ice and contain significant concentrations of particles [4,62]. Further investigation and local education are essential to raise awareness of this issue and to facilitate comparable research on MP pollution and its potential consequences for local wildlife in Finnmark, Norway. Future research could focus on identifying MPs introduced through snow and rain, as well as examining aquatic wildlife to determine the extent of MP exposure and whether it has measurable consequences for fish.

5. Conclusions

  • The cartridge filtration casing model 01WTKF was tested for its resistance to hydroabrasion during the sampling procedure. The results show that hydroabrasion occurs during sampling on the polypropylene (PP)-based bottom part and lid at subzero temperatures.
  • To further emphasize this point, the cross-contamination leads to a significant difference (p < 0.05) when comparing results obtained with the model 01WTKF to the actual microplastic pollution in the environment measured with the model 01WTGD (Wolftechnik…).
  • The obtained data support Jander et al. [39] in their suspicion of abrasion above 0 °C, by showing that abrasion is possible at least below 0 °C.
  • Additionally, the use of PP-based components is suspected to cause microplastic pollution of particles <10 µm.
  • For these reasons, the model 01WTGD with PP-based bottom parts and lids should not be used for sampling microplastics. Data obtained from PP-based components should be reviewed and evaluated to control the accuracy of the obtained data.
  • The styrene–acrylonitrile copolymer (SAN)-based bottom parts withstood hydroabrasion and showed no abrasion <10 µm.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/microplastics4010014/s1. Table S1. GPS coordinates for the sampled locations. Table S2. Abrasion levels for lids and bottom parts in the laboratory. Table S3. Size distribution for the laboratory samples. Table S4. Abrasion levels for lids and bottom parts in the environment. Table S5. From top to bottom, particle counts, sample composition, particle form, and size distribution for the environmental contamination.

Author Contributions

Conceptualization, F.M. and M.M.; Data curation, F.M.; Formal analysis, F.M.; methodology, F.M.; investigation, F.M. and M.M.; analysis and writing—original draft preparation, F.M.; writing—review and editing, F.M., M.M., C.W. and M.D.; visualization, F.M.; supervision F.M. and A.F.; project administration, A.F. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

This study did not require ethical approval.

Informed Consent Statement

This study did not involve humans.

Data Availability Statement

Data are available in Supplementary Materials.

Acknowledgments

Without the guides from Nordgehen GbR this project would not have been possible. The planning on site and expedition with sledding dogs in Finnmark were executed precisely and well-coordinated.

Conflicts of Interest

The authors of this paper declare that they have no personal relationships or competing financial interests that could have influenced the work reported in this paper.

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Microplastics 04 00014 g001
Figure 1. There are different ways for microplastics to enter the environment, especially the sub-Arctic and Arctic, by atmospheric input. Therefore, different kinds of measured pollution are depicted in the illustration. The figure is adapted from AWI-Infographic, CC BY 4.0, without any changes to the graphic (https://creativecommons.org/licenses/by/4.0/) accessed on 12 February 2025.
Figure 1. There are different ways for microplastics to enter the environment, especially the sub-Arctic and Arctic, by atmospheric input. Therefore, different kinds of measured pollution are depicted in the illustration. The figure is adapted from AWI-Infographic, CC BY 4.0, without any changes to the graphic (https://creativecommons.org/licenses/by/4.0/) accessed on 12 February 2025.
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Figure 2. ▲: mean. Comparison of sampling in the presence of ice and sand with the model 01WTKF and in the environment with the bottom part made of PP. The means amount to 2255 ± 142 N m−3 for ice, 1425 ± 107 N m−3 for sand, and 1690 ± 290 N m−3 for environment. A significant difference (p < 0.05) was found by the Kruskal–Wallis Test, and the Dunn Test confirmed a significant difference (p < 0.05) for the mean of the sand samples compared to the mean of the ice samples. For the mean of the environment samples, no significant difference was confirmed.
Figure 2. ▲: mean. Comparison of sampling in the presence of ice and sand with the model 01WTKF and in the environment with the bottom part made of PP. The means amount to 2255 ± 142 N m−3 for ice, 1425 ± 107 N m−3 for sand, and 1690 ± 290 N m−3 for environment. A significant difference (p < 0.05) was found by the Kruskal–Wallis Test, and the Dunn Test confirmed a significant difference (p < 0.05) for the mean of the sand samples compared to the mean of the ice samples. For the mean of the environment samples, no significant difference was confirmed.
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Figure 3. ▲: mean. For the locations Tanaelva 1 and Bergebyelva, where the PP casings were used. The difference in PP levels without and with added cross-contamination through abrasion on the PP casings and lids is displayed. The means amount to 858 ± 516 N m−3 (Figure 5A,C) for the environmental samples and 2453 ± 92 N m−3 for the environmental samples with abrasion. The added cross-contaminations led to a significant difference (p < 0.05) in the measurement of PP particles.
Figure 3. ▲: mean. For the locations Tanaelva 1 and Bergebyelva, where the PP casings were used. The difference in PP levels without and with added cross-contamination through abrasion on the PP casings and lids is displayed. The means amount to 858 ± 516 N m−3 (Figure 5A,C) for the environmental samples and 2453 ± 92 N m−3 for the environmental samples with abrasion. The added cross-contaminations led to a significant difference (p < 0.05) in the measurement of PP particles.
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Figure 4. Size comparison for MP abrasion in percentage for the categories: <5 mm–1 mm, <1 mm–50 µm, and <50 µm–10 µm. The results show abrasion levels for the means as high as 91% for particles with a size of <50 µm to 10 µm, 9% for particles with a size of <1 mm–50 µm, and 0% for particles with a size of <5 mm to 1 mm. There are no significant differences within the distribution groups.
Figure 4. Size comparison for MP abrasion in percentage for the categories: <5 mm–1 mm, <1 mm–50 µm, and <50 µm–10 µm. The results show abrasion levels for the means as high as 91% for particles with a size of <50 µm to 10 µm, 9% for particles with a size of <1 mm–50 µm, and 0% for particles with a size of <5 mm to 1 mm. There are no significant differences within the distribution groups.
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Figure 5. (A) The polymer composition for the samples taken at the locations: Báíšjohka, Tanaelva 1, and Bergebyelva. All samples rank PE as the most abundant polymer, followed by PP, PA, and PS. PET was detected only for Báíšjohka and Tanaelva 1, the latter being the only one containing EVOH. (B) Particle size comparison for MP abrasion in percentage. The results display the means for all locations with 91% for <25 µm, 5% for <1 mm–25 µm, and 4% for <5 mm–1 mm. There are no significant differences within the distribution groups. (C) ▲: mean. The overall particle amount for Tanaelva 1 was the highest with 2873 ± 265 N m−3, followed by Báíšjohka with 1622 ± 329 N m−3 and Bergebyelva with 1297 ± 523 N m−3. The total mean for all three locations amounts to 1900 ± 779 N m−3. There are no significant differences among the three locations.
Figure 5. (A) The polymer composition for the samples taken at the locations: Báíšjohka, Tanaelva 1, and Bergebyelva. All samples rank PE as the most abundant polymer, followed by PP, PA, and PS. PET was detected only for Báíšjohka and Tanaelva 1, the latter being the only one containing EVOH. (B) Particle size comparison for MP abrasion in percentage. The results display the means for all locations with 91% for <25 µm, 5% for <1 mm–25 µm, and 4% for <5 mm–1 mm. There are no significant differences within the distribution groups. (C) ▲: mean. The overall particle amount for Tanaelva 1 was the highest with 2873 ± 265 N m−3, followed by Báíšjohka with 1622 ± 329 N m−3 and Bergebyelva with 1297 ± 523 N m−3. The total mean for all three locations amounts to 1900 ± 779 N m−3. There are no significant differences among the three locations.
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Figure 6. Traced particle shapes for all three locations. The total mean for each group amounts to 81% fragments, 11% fibers, 5% foam, and 3% films. No significant differences within the groups are confirmed.
Figure 6. Traced particle shapes for all three locations. The total mean for each group amounts to 81% fragments, 11% fibers, 5% foam, and 3% films. No significant differences within the groups are confirmed.
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Table 1. Locations of sampling, the used setups, and dates and times of sampling.
Table 1. Locations of sampling, the used setups, and dates and times of sampling.
LocationsUsed SetupDate and Time
BáišjohkaStainless steel and SAN1 March 2024; 09:42 a.m.
Tanaelva 1Stainless steel and PP3 March 2024; 10:12 a.m.
Tanaelva 2Only SAN *3 March 2024; 10:42 a.m.
BergebyelvaStainless steel and PP3 March 2024; 12:02 p.m.
* The casing was contaminated during a safety check by the security staff, as evidenced by a broken seal on the lid.
Table 2. Results of the positive controls for the ice and sand suspensions, as for the environmental samples.
Table 2. Results of the positive controls for the ice and sand suspensions, as for the environmental samples.
SuspensionMeanStandard
Deviation		Coefficient of VariationAbsolute ErrorRelative Error
NL−1NL−1%NL−1%
Ice2434±65 2.67 66 2.64
Sand2416±70 2.90 84 3.38
Environment2428±49 2.02 72 2.89
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Manna, F.; Mues, M.; Wiebensohn, C.; Dukat, M.; Fath, A. Influence on the Result by Abrasion on Filter Casings, Tested in the Environment in Finnmark, Norway. Microplastics 2025, 4, 14. https://doi.org/10.3390/microplastics4010014

AMA Style

Manna F, Mues M, Wiebensohn C, Dukat M, Fath A. Influence on the Result by Abrasion on Filter Casings, Tested in the Environment in Finnmark, Norway. Microplastics. 2025; 4(1):14. https://doi.org/10.3390/microplastics4010014

Chicago/Turabian Style

Manna, Fabio, Michel Mues, Clara Wiebensohn, Maja Dukat, and Andreas Fath. 2025. "Influence on the Result by Abrasion on Filter Casings, Tested in the Environment in Finnmark, Norway" Microplastics 4, no. 1: 14. https://doi.org/10.3390/microplastics4010014

APA Style

Manna, F., Mues, M., Wiebensohn, C., Dukat, M., & Fath, A. (2025). Influence on the Result by Abrasion on Filter Casings, Tested in the Environment in Finnmark, Norway. Microplastics, 4(1), 14. https://doi.org/10.3390/microplastics4010014

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