Microplastics in surface snow from SE-Dome, southeastern Greenland Ice Sheet

Microplastics in surface snow from SE-Dome, southeastern Greenland Ice Sheet | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Microplastics in surface snow from SE-Dome, southeastern Greenland Ice Sheet Hiroshi Ohno, Yoshinori Iizuka, Shuji Fujita This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7450097/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract The polar ice sheets can be regarded as samplers and archives of deposited aerosols, including microplastics (MPs). Nevertheless, there are very few examples to date of studies of MPs in snow from ice sheets. We have conducted preliminary investigations of MPs (> 10 µm) in surface snow from the southeastern dome (SE-Dome) of the Greenland Ice Sheet. Analyses combining fluorescence microscopy and micro-Fourier Transform Infrared (micro-FTIR) spectroscopy detected nine microplastic (MP) types, mostly with fragmentary shapes. Almost all fragmentary MPs were smaller than 50 µm, but most fiber MPs were in the larger size classes (> 50 µm). The number of MPs observed generally increased concomitantly with decreasing size. The MP concentrations were 45–64 particles/L, with an average of 54 particles/L. These findings suggest important implications for better understanding of the nature and mechanism of the long-distance atmospheric transport of MPs. Microplastic Surface snow Greenland Ice Sheet Figures Figure 1 Figure 2 Figure 3 Figure 4 1. Introduction The widespread use of plastic products provides indispensable convenience in modern life, but it has led simultaneously to escalation of global plastic waste problems (e.g., Kibria et al., 2023 ). Small plastic particles measuring 5 mm or less in diameter, referred to as microplastics (MPs), are particularly problematic because of their difficulty of retrieval once released. Their resistance to degradation allows them to remain in the environment for long periods, and they also exhibit a high affinity for adsorbing persistent organic pollutants (e.g., Tang, 2021 ). In recent years, numerous reports have described the bioaccumulation of MPs, raising increasing concerns related to their potential effects on ecosystems (e.g., Gao et al., 2024 ) and on human health (e.g., Marfella et al., 2024 ). Initially, microplastic (MP) pollution was regarded primarily as a marine issue (e.g., Thompson et al., 2004 ), but growing evidence confirms that MPs are also ubiquitous in the atmosphere (e.g., Dris et al., 2016 ). Although their detailed mechanisms and pathways remain poorly understood, atmospheric MPs are thought to undergo long-range transport via atmospheric circulation, facilitating their global dispersal (e.g., Allen et al., 2019 and 2021 ; Xiao et al., 2023 ). Snow and ice of the polar ice sheets, in which deposited aerosols are preserved, can serve as natural aerosol samplers and archives, providing great opportunities to obtain insights into the atmospheric transport of aerosols to polar areas (e.g., Nagatsuka et al., 2021 ; Schüpbach et al., 2018 ; Thomas et al., 2017 ). However, only four studies to date have reported investigations of snow and ice from the polar ice sheets for the analysis of microplastics: an emerging class of aerosols. Pioneering research using micro-Fourier Transform Infrared (micro-FTIR) spectroscopy conducted by Aves and others (2022) provided the first evidence of microplastics (mostly polyethylene terephthalate: PET) in Antarctic snow from the Ross Island region. They reported the average concentrations of MPs (> 50 µm) as 29 particles/L. Subsequently, Robini and others (2024) used electron microscopy and micro-Raman spectroscopy to characterize small microparticles and nanoparticles in coastal Antarctic snow. Although they detected polyethylene (PE) and poly(ethylene-co-vinyl-acetate) particles, statistically useful data such as the number concentration and size distribution were not reported. Very recently, observations of MPs in snow samples from Antarctic camps (Union Glacier, Schanz Glacier, and the South Pole) were reported by Jones-Williams and others (2025). Using FTIR imaging, they investigated smaller particles (> 11 µm) than those examined for the pioneering research, and detected higher concentrations (817 particles/L on average) of MPs dominated by polyamide, PET, PE and synthetic rubber. For the Greenland Ice Sheet, Materić et al. ( 2022 ) conducted an analysis of plastics in a shallow firn core collected near the EastGRIP deep drilling site using Thermal Desorption-Proton Transfer Reaction-Mass Spectrometry. However, the analytical method which was applied was designed to estimate the types and overall quantities of plastics, providing no information at the individual particle level. Because of scant field data, as introduced above, little is known even about the features of microplastics in snow and ice from the ice sheets. This report describes the first direct finding of microplastics in Greenland snow. Using an integrated approach combining fluorescence microscopy and micro-FTIR spectroscopy, we investigated the abundance, polymer type, size, and shape of MPs (> 10 µm) in surface snow from the southeastern dome (SE-Dome) of the Greenland Ice Sheet. 2. Experimental 2.1. Snow sampling On May 31, 2021, surface snow, upper 55 cm, was collected at the SE-Dome of the Greenland ice sheet (67˚19ʹ N, 36˚ 47ʹ W, 3161 m a.s.l.), during the ice-core drilling expedition (Iizuka et al., 2021 ). After a 40×39×55 cm 3 snow block was extracted from a side wall of a snow pit with a snow saw, the snow block was put into and closed up within a large polyethylene bag. Sampling was conducted downwind at all times. The bagged snow block, which was packed in an insulated polystyrene box, was shipped to Japan at − 25 ºC. After arrival at our institute, the snow block was stored in a freezer set at − 50 ºC until sample preparation preceding measurement. 2.2. Sample preparation Half of the snow block (40×20×55 cm 3 ) was used for this study. In a clean bench installed in a cold room set at − 20 ºC, using a ceramic knife, the outer sides (more than 5 cm thickness) of the half snow block were removed for decontamination. Then the remaining inner part of snow was transferred into a glass bottle with a stainless-steel grain scoop. In all, three bottles of samples were prepared. Snow samples were thawed at room temperature in the closed glass bottles. Approximately 250 mL of each thawed sample (all water in a bottle) was filtered onto an aluminum oxide filter (25 mm diameter, 0.2 µm pore size, Anodisc; Whatman plc.) using a vacuum filtration apparatus made of glass. With the filter still attached to the apparatus, approximately 30 mL of 30% H 2 O 2 was poured in a glass funnel of the apparatus. The funnel opening was covered with aluminum foil. After the solution was left for 1 day at room temperature to remove natural organic matter adhered to MPs (Liebezeit and Dubaish, 2012 ), the solution was filtered with the apparatus. After finishing the filtration of approximately 50 mL of ultra-pure water (18 MΩཥcm), the filter was removed from the apparatus. It was then dried in a glass petri dish. All processes described above were performed in a clean booth with a HEPA filtration unit. For this study, Anodiscs were washed before use for decontamination. After the Anodiscs were sonicated in acetone for five minutes and rinsed with the ultra-pure water, these filters were dried in glass petri dishes. Although earlier works by the authors (Ohno and Iizuka, 2023 , 2024 ) have shown that noticeable numbers of microparticles including MPs are always present on brand-new Anodiscs, irrespective of the production lot, the pre-cleaning described above can remove inherent particles from a filter thoroughly. Another important procedure newly adopted for this study is fluorescent staining of residual particles on a filter for rapid screening of suspected plastic particles (Erni-Cassola et al., 2017 ; Maes et al., 2017 ; Shim et al., 2016 ). As a final step of sample preparation, using a syringe filter, three drops of an acetone solution of Nile red (10 µg/mL) were dripped on each filter in the clean booth. It was then dried in a glass petri dish. Nile red is a fluorescent lipophilic dye originally applied for detection and quantification of intracellular lipids in the field of biology (Greenspan et al., 1985 ). Because of the hydrophobic nature of common plastics, Nile red is adsorbed selectively onto the surfaces of MPs. By contrast, hydrophilic mineral particles, which dominate residues on a filter, are not dyed to any marked degree by Nile red. 2.3. Fluorescence microscopic observation After a prepared filter was placed in an optical petri dish made of quartz, it was inspected through a quartz optical window using a fluorescence microscope (CX41FL; Olympus Corp.) under blue light excitation (475 nm center wavelength). Our earlier work with conventional optical microscopy (Ohno and Iizuka, 2023 , 2024 ) examined only particles larger than 30 µm, but even smaller particles can be analyzed reasonably using fluorescence microscopy by virtue of enhanced visibility. By observing the entire filter surface, we found all fluorescent particles larger than 10 µm to be targets of micro-FTIR analysis. Then we recorded their coordinate positions on a filter. The shapes of these particles were classified as fragments (e.g., Fig. 1 a) or fibers (e.g., Fig. 1 b). Targeted particles were photographed under both white light and fluorescence using a digital camera (EOS Kiss X9; Canon Inc.) attached to the microscope. Then their maximum diameters or lengths were measured by analyzing micrographs using image-processing software (ImageJ; NIH). Micrographs of typical particles are presented in Figs. 1 a and 1 b. 2.4. Micro-FTIR analysis Chemical identifications of microparticles were accomplished using micro-FTIR. All targeted particles on filters were analyzed using an FTIR microscope (Nicolet iN10; Thermo Fisher Scientific K.K.) in transmission mode with the following parameters: 10 µm × 10 µm (or 20 µm × 20 µm) square field aperture, 4 cm − 1 spectral resolution, 128 (or 256) scans, and 1250–3600 cm − 1 spectral range. The obtained FTIR spectra were subsequently compared with the commercial spectral databases of standard polymers (Hummel Polymer sample Library and HR Polymer and additives) and also with open-access libraries designed for MP research, which includes spectra of aged plastics (Chabuka and Kalivas, 2020 ; Cowger et al., 2021 ; De Frond et al., 2021 ; Primpke et al., 2018 ), using spectroscopy software (OMNIC Picta; Thermo Fisher Scientific K.K.). Spectra with a match of 60%, an additional visual examination of spectra was performed manually, leading to final acceptance or rejection (Kanhai et al., 2018 ; Obbard et al., 2014 ; Yang et al., 2015 ). FTIR spectra of typical particles are presented in Figs. 1 c and 1 d. 2.5. Blank test Blank tests were conducted to assess the validity of methods. During inner-snow extraction in the clean bench, an uncovered empty glass bottle was put beside the snow block until the work was finished. It was then closed with a lid. After the blank bottle was filled with ultra-pure water, it was processed using the same procedures as those used for the snow samples. In all, two blanks were tested. Observations of blank-filter surfaces with the fluorescence microscope revealed several fluorescent particles on blank samples. Subsequent micro-FTIR analyses of these fluorescent particles detected one polystyrene from the first blank, and no MPs from the second one. The averaged MP abundance on a blank filter (0.5 particle/filter) was two orders of magnitude lower than that on a snow-filtered filter (14 particles/filter). Therefore, almost all MPs detected in measurements of snow-filtered filters are regarded as originating from the snow samples. Because the sampled inner sections of the snow block were never exposed directly to contamination during fieldwork, transport, or storage, field blanks were not taken (Materić et al., 2022 ). 3. Results 3.1. Particle composition Compositions of fluorescent particles from snow samples are depicted in Fig. 2 a. For Sample-1 and Sample-3, the dominant composition was other organic matter except MP, cellulose, and protein, accounting for 67% of all fluorescent particles on average. In contrast, for Sample-2, fluorescent particles were dominated by cellulose (66%) instead of other organic matter. Actually, MPs were detected from all snow samples as the second highest composition, with MP composition ratios of 17–29%, averaging 23%. Compositions of MPs in each snow sample are depicted in Fig. 2 b. Overall, plastic polymers of nine types were detected from microparticles: alkyd, polyethylene terephthalate (PET), rubber, polystyrene (PS), acrylic, polyurethane (PU), polyethylene (PE), polyvinyl chloride (PVC), and polycarbonate (PC). Also, MP types were found to depend on the snow samples (Fig. 2 b): MPs in Sample-1 were mostly alkyd, whereas other plastic species such as PET, rubber, and PS were also often observable for other samples. 3.2. Microplastic abundance Abundances of microplastics in snow samples were estimated from the numbers of MPs on filters and the volumes of water samples (Table 1 ). The observed concentrations of MPs were 45–64 particles/L (Table 1 ). The average value and the coefficient of variation of the MP abundances were, respectively, 54 particles/L and 17%. In fact, these MP concentrations were two orders of magnitude lower than those estimated using exactly the same methods for fresh snow from a protected area (Lake Chimikeppu) in Hokkaido, the northern island of Japan (not shown). Table 1 Filtered volumes of melted snow samples, numbers of fluorescent particles (> 10 µm) on filters, numbers of MPs (> 10 µm) on filters, and abundances of MPs (> 10 µm) Sample code Filtered volume (mL) Number of fluorescent particles (particles/filter) Number of MPs (particles/filter) MP abundance (particles/L) Sample-1 250.0 56 16 64 Sample-2 260.9 56 14 54 Sample-3 243.9 65 11 45 3.3. Microplastic composition, size, and shape Observed frequencies of MPs from snow samples are portrayed in Fig. 3 for various MP types in different size classes. The averaged values of polymer compositions of MPs are presented in Fig. 4 a. Alkyd, PET, rubber, and PS were the dominant compositions of MPs in the snow samples, accounting for 83%. Among these components, alkyd, PET, and rubber particles were observed in all samples, whereas PS particles were detected in specific samples (Figs. 2 b and 3 ). For all samples, MPs were mainly in the 10–50 µm size range in maximum diameter or length (Fig. 3 ). As a general trend, most alkyd, rubber, and PS particles were of the size class of less than 40–50 µm, whereas PET particles were distributed in wide size ranges. Size distributions of fragment and fiber microplastics are presented in Fig. 4 b. The shapes of MPs from snow samples were mostly fragments, accounting for 83%. More than 97% of fragment MPs had smaller maximum diameter than 50 µm, whereas most fiber MPs had greater than 50 µm length. Fragment MPs consisted of all types of plastic polymers except for acrylic, whereas fiber MPs comprised PET and acrylic. 4. Discussion As presented in the preceding section, the features (especially compositions) of MPs depend on snow samples, possibly because of differences in snow depth (not measured), specifically differences in timing of MP deposition. However, this variation might be attributed partly to the small sample sizes ( n in Fig. 2 b). The described properties and abundances of MPs in Greenland and Antarctic snows reported to date differ considerably (Aves et al., 2022 ; Jones-Williams et al., 2025 ; Riboni et al., 2024 ). Although Zhang and others (2022) pointed out in their review article that this diversity might be attributable more to differences in sampling and analytical methods used than to actual regional differences, we strove to extract meaningful information by comparing our results with those reported from earlier studies. According to detailed estimations of MP abundance for Antarctic snow samples obtained near the Union Glacier and the South Pole (Jones-Williams et al., 2025 ), for particles larger than 11 µm, the MP concentrations were estimated on average as 817 particles/L. Despite having a similar detection limit (10 µm in our case), this averaged value is one order of magnitude larger than that of ours (54 particles/L). This discrepancy may be attributable to the difference in remoteness from human activities. The Union Glacier and the South Pole not only host research stations and camps: these are also popular spots for Antarctic land tours. In contrast, the SE-Dome is truly deserted (see the subsection of this section before the last). Another possible cause is the different analytical methods used for MP detection. Jones-Williams and others (2025) analyzed all residues on a filter using a FPA-based micro-FTIR imaging, whereas only fluorescent (i.e., hydrophobic) particles were targeted for micro-FTIR analysis in the present work, which might lead to some degree of underestimation of MP abundance. In some cases, the hydrophobic nature of plastic is altered to be hydrophilic during the manufacturing process by surface treatments or additives (Song et al., 2023; Zhang et al., 2025 ). Moreover, the degree of MP hydrophobicity can be decreased as a result of UV-weathering (Alimi et al., 2023 ; Yu et al., 2024 ). The most frequent polymer type we detected was alkyd (Fig. 4 a), which is widely used mainly in paint and coating applications. The presence of alkyd particles was confirmed earlier not only in Antarctic snow samples from the Ross Island region (Aves et al., 2022 ), but also in both Arctic sediment and seawater (Kim et al., 2023 ). Other dominant polymer types examined for this work were PET, rubber, and PS (Fig. 4 a). These compositions were often observable in Greenland (Materić et al., 2022 ) and Antarctic (Jones-Williams et al., 2025 ) snow samples. Although the three polymer types were also detected in Arctic marine environments (Kim et al., 2023 ), a very recent analysis of MPs in subsurface water from the fjords of Tunu (East Greenland) with laser direct infrared (LDIR) imaging showed that PET was predominant over all other polymer species (Vetter et al., 2025 ). The size distribution of microplastics observed in this study (Fig. 4 b) is consistent with general trends reported from the earlier work in Antarctica (Jones-Williams et al., 2025 ): MPs in snows from the Union Glacier and the South Pole regions were generally smaller than 50 µm; the number of MPs observed generally increased concomitantly with decreasing size. In terms of morphology, as observed from this work (Fig. 4 b), non-fibers (particulates) were the dominant shape in microplastics from the Antarctic snows (Jones-Williams et al., 2025 ), accounting for 79% (in our case 83%). Similar results for MP size and shape have been reported for snow/precipitation samples worldwide (Allen et al., 2019 ; Bergmann et al., 2019 ; Klein and Fischer, 2019 ; Ohno and Iizuka, 2023 ; Zhang et al., 2021 ). No major source of plastics exists near the SE-Dome. Moreover, this remote site is located at a higher altitude (3161 m a.s.l.) than the atmospheric boundary layer. From these reasons, the observed MPs are regarded as deriving from long-distance atmospheric transportation. Aerosols of various types such as mineral dust, sulfate, nitrate, and black carbon are well known to be brought to Greenland and then deposited on the ice sheet by atmospheric circulation in the troposphere (e.g., Nagatsuka et al., 2021 ; Schüpbach et al., 2018 ; Thomas et al., 2017 ). Similar long-range atmospheric transport is expected to have occurred with microplastics. Allen et al. ( 2021 ) reported observational evidence for the presence of microplastics in the free troposphere at the Pic du Midi Observatory (2877 m a.s.l), in southeastern France, and suggested that these MPs can be transported at an intercontinental (or trans-oceanic) scale based on the air mass and particle history calculated with atmospheric transport and particle dispersion models. Compared to microplastics with some other shape, fiber MPs are regarded as remaining in the atmosphere for a longer period of time because of their shape. Reportedly, they are more likely to be transported a longer distance: recently Xiao et al. ( 2023 ) developed a theory-based settling velocity model for fiber MPs in the atmosphere, predicting their mean residence-time enhancement as greater than 450% compared to spherical particles. For the case of the SE-Dome, backward trajectory analyses suggest that the primary origin of air mass is North America, followed in importance by Europe and Russia (Iizuka et al., 2018 ). In addition to remote terrestrial environments, seas and oceans might be other important sources for microplastics. Allen et al. ( 2020 ) conducted a pilot investigation of marine boundary layer air samples on the French Atlantic coast. They detected a considerable number of microplastics especially in oceanic air dominated by sea spray, suggesting that MPs are released actively from the marine environment into the atmosphere by sea spray. Increasing evidence has pointed to the importance of this phenomenon as a major secondary source of microplastics. For instance, using in situ observations of MP deposition combined with an atmospheric transport model and optimal estimation techniques, Brahney et al. ( 2021 ) tested hypotheses of the most likely sources of atmospheric plastic. They concluded that oceans dominated plastic sources on a global scale, accounting for 99% of the deposition to oceans and 7% of the deposition to land surfaces away from coastal regions. In relation to this finding, sea-salt particles emitted from seas and oceans are commonly observable in Greenland snow and ice, even in the interior of the ice sheet (e.g., Oyabu et al., 2020 ). Contamination by research activities is regarded as minimal at the SE-Dome because this location is a temporal observation site. Furthermore, the Summit Camp, the nearest year-round staffed research station on the ice sheet operated by the United States, is approximately 600 km distant from the SE-Dome. Of course, no tourists are present there. To elucidate the state of airborne-MP deposition on the ice sheet, i.e., for better understanding of the nature and mechanism of the long-distance atmospheric transport of MPs, systematic field work for wide area observations across various geographical settings and further experimentation must be conducted. Declarations Acknowledgements H.O. gratefully appreciates technical assistance with the experiment setup provided by Tadahisa Yamada and Shinya Ishizawa, and thanks all participants in the fieldwork for their support in snow sampling. This study was supported by MEXT/JSPS KAKENHI Grants: Nos. 23H00511 and 24H00760. References Alimi OS, Claveau Mallet D, Lapointe M, Biu T, Liu L, Hernandez LM et al (2023) Effects of weathering on the properties and fate of secondary microplastics from a polystyrene single-use cup. 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Appl Sci 14:1597. https://doi.org/10.3390/app14041597 Schüpbach S, Fischer H, Bigler M, Erhardt T, Gfeller G, Leuenberger D, Mini O, Mulvaney R, Abram NJ, Fleet L, Frey MM, Thomas E, Svensson A, Dahl- Jensen D, Kettner E, Kjaer H, Seierstad I, Steffensen JP, Rasmussen SO, Vallelonga P, Winstrup M, Wegner A, Twarloh B, Wolff K, Schmidt K, Goto- Azuma, Kuramoto K, Hirabayashi T, Uetake M, Zheng J, Bourgeois J, Fisher J, Zhiheng D, Xiao D, Legrand C, Spolaor M, Gabrieli A, Barbante J, Kang C, Hur J-H, Hong SD, Hwang SB, Hong HJ, Hansson S, Iizuka M, Oyabu Y, Muscheler I, Adolphi R, Maselli F, McConnell O, Wolff J (2018) E.W., Greenland records of aerosol source and atmospheric lifetime changes from the Eemian to the Holocene. Nat. Commun. 9, 1476. https://doi.org/10.1038/s41467-018-03924-3 Shim WJ, Song YK, Hong SH, Jang M (2016) Identification and quantification of microplastics using Nile red staining. Mar Pollut Bull 113:469–476. https://doi.org/10.1016/j.marpolbul.2016.10.049 Song Y, Dunleavy M, Li L (2023a) How to make plastic surfaces simultaneously hydrophilic/oleophobic? ACS Appl Mater Interfaces 15:31092–31099. https://doi.org/10.1021/acsami.3c06787 Tang KHD (2021) Interactions of microplastics with persistent organic pollutants and the ecotoxicological effects: a review. Trop Aqua Soil Pollut 1:24–34. https://doi.org/10.53623/tasp.v1i1.11 Thomas JL, Polashenski CM, Soja AJ, Marelle L, Casey KA, Choi HD, Raut JC, Wiedinmyer C, Emmons LK, Fast JD, Pelon J, Law KS, Flanner MG, Dib JB (2017) Quantifying black carbon deposition over the Greenland ice sheet from forest fires in Canada. Geophys Res Lett 15:7965–7974. https://doi.org/10.1002/2017GL073701 Thompson RC, Olsen Y, Mitchell RP, Davis A, Rowland SJ, John AW, McGonigle D, Russell AE (2004) Lost at sea: where is all the plastic? Science 304:838. https://doi.org/10.1126/science.1094559 Vetter CB, Hildebrandt L, Zimmermann T, Schmidt CE, El Gareb F, Mitrano DM, Pröfrock D, Thomas H (2025) Analysis of microplastics in the fjords of Tunu (East Greenland). Mar Pollut Bull 218:118192. https://doi.org/10.1016/j.marpolbul.2025.118192 Xiao S, Cui Y, Brahney J, Mahowald NM, Li Q (2023) Long-distance atmospheric transport of microplastic fibres influenced by their shapes. Nat Geosci 16:863–870. https://doi.org/10.1038/s41561-023-01264-6 Yang D, Shi H, Li L, Li J, Jabeen K, Kolandhasamy P (2015) Microplastic pollution in table salts from China. Environ Sci Technol 49(22):13622–13627. https://doi.org/10.1021/acs.est.5b03163 Yu F, Qin QY, Zhang XC, Ma J (2024) Characteristics and adsorption behavior of typical microplastics in long-term accelerated weathering simulation. Environ Sci Process Impacts 26:882–890. https://doi.org/10.1039/d4em00062e Zhang Y, Gao T, Kang S, Shi H, Mai L, Allen D, Allen S (2022) Current status and future perspectives of microplastic pollution in typical cryospheric regions. Earth Sci Rev 226:103924. https://doi.org/10.1016/j.earscirev.2022.103924 Zhang Y, Gao T, Kang S, Allen S, Luo X, Allen D (2021) Microplastics in glaciers of the Tibetan Plateau: evidence for the long-range transport of microplastics. Sci Total Environ 758:143634. https://doi.org/10.1016/j.scitotenv.2020.143634 Zhang Y, Zhao Y, Qian Z, Wang Q, Yalikun N, Jiang H, Wang C, Wang H (2025) A hydrophilic/hydrophobic switch on polymer surface triggered by calcite towards separation of hazardous PVC from plastic mixtures. J Hazard Mater 483:136667. https://doi.org/10.1016/j.jhazmat.2024.136667 Additional Declarations The authors declare no competing interests. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7450097","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":505043072,"identity":"02054dca-4416-432f-862c-72863fbd973c","order_by":0,"name":"Hiroshi Ohno","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABCElEQVRIiWNgGAWjYBACAwYGNiBlw8DAzNzA2ADkMjAzMByASB7ApyUNqJIRpMUAouUAYS2HgRikBcTHrRgCzBmYjz0uqDgfzd8O1DKj4I+8bjsD4+EPDHbyDIxnseq0bGBLN55x5nbujMNALRsMDAy3HQY7LNmwgeFcAlaHHeAxk+Ztu53bANLywMCAcdth/g9ALcxA5WcM8Gg5lzsfqsUeaks9IS0HcjdAHZYI1XIYjxa2NGmeM8m5G4FaDs4wME4GazljcNywDadfmI9J81TY5c47f/jgw54/crbbzh9g/lBRUS3PL4E9xBjkHyDYSCpA8SVxBqsOfIC/h2Qto2AUjIJRMCwBAAP+ZFWlEcrLAAAAAElFTkSuQmCC","orcid":"","institution":"Kitami Institute of Technology","correspondingAuthor":true,"prefix":"","firstName":"Hiroshi","middleName":"","lastName":"Ohno","suffix":""},{"id":505043073,"identity":"9ec1cb40-d8c2-43ec-a156-7bec1fdf7ce9","order_by":1,"name":"Yoshinori Iizuka","email":"","orcid":"","institution":"Institute of Low Temperature Science, Hokkaido University","correspondingAuthor":false,"prefix":"","firstName":"Yoshinori","middleName":"","lastName":"Iizuka","suffix":""},{"id":505043074,"identity":"f49108b0-54ae-4604-ad70-fb3dfe1393bf","order_by":2,"name":"Shuji Fujita","email":"","orcid":"","institution":"National Institute of Polar Research","correspondingAuthor":false,"prefix":"","firstName":"Shuji","middleName":"","lastName":"Fujita","suffix":""}],"badges":[],"createdAt":"2025-08-25 06:00:24","currentVersionCode":1,"declarations":{"humanSubjects":false,"vertebrateSubjects":false,"conflictsOfInterestStatement":false,"humanSubjectEthicalGuidelines":false,"humanSubjectConsent":false,"humanSubjectClinicalTrial":false,"humanSubjectCaseReport":false,"vertebrateSubjectEthicalGuidelines":false},"doi":"10.21203/rs.3.rs-7450097/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7450097/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":89914599,"identity":"2fa3702a-a72a-4060-8784-bf1420d3e5ed","added_by":"auto","created_at":"2025-08-26 11:33:49","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":6731623,"visible":true,"origin":"","legend":"\u003cp\u003eMicrographs and FTIR spectra of particles from snow samples identified as (a, c) polyvinyl chloride and (b, d) polyethylene terephthalate. Spectra from the particles are shown with blue lines, whereas those for references (Cowger et al., 2021; De Frond et al., 2021) are presented as red lines.\u003c/p\u003e","description":"","filename":"Fig.1.png","url":"https://assets-eu.researchsquare.com/files/rs-7450097/v1/ab2a6b8687af2feb8d116aaa.png"},{"id":89914336,"identity":"ae20e7e4-e413-41c2-a343-7a2bbf6a7253","added_by":"auto","created_at":"2025-08-26 11:25:49","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":147670,"visible":true,"origin":"","legend":"\u003cp\u003eRelative compositions of particles in surface snow identified using micro-FTIR: (a) fluorescent particle compositions and (b) MP compositions in snow samples.\u003c/p\u003e","description":"","filename":"Fig.2.png","url":"https://assets-eu.researchsquare.com/files/rs-7450097/v1/a7a4a36f14c65ababfd808c0.png"},{"id":89915603,"identity":"61445a8a-a127-4c6e-9494-2cf4b453fcdc","added_by":"auto","created_at":"2025-08-26 11:41:49","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":207378,"visible":true,"origin":"","legend":"\u003cp\u003eStacked bar chart of observed numbers of MPs of various types from snow samples in different size classes.\u003c/p\u003e","description":"","filename":"Fig.3.png","url":"https://assets-eu.researchsquare.com/files/rs-7450097/v1/fdd050fb81837a7b8dfc8654.png"},{"id":89913385,"identity":"b54e8f00-22c6-4a2c-a589-ec0f22d024fd","added_by":"auto","created_at":"2025-08-26 11:17:49","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":325710,"visible":true,"origin":"","legend":"\u003cp\u003eData of microplastics from all snow samples (\u003cem\u003en\u003c/em\u003e= 41): (a) polymer compositions of MP and (b) size distributions of MP fragments and fibers.\u003c/p\u003e","description":"","filename":"Fig.4.png","url":"https://assets-eu.researchsquare.com/files/rs-7450097/v1/fe0e4662094c01cea84beb58.png"},{"id":89915605,"identity":"3191819e-f86a-4991-a94d-abd35a6fc94e","added_by":"auto","created_at":"2025-08-26 11:41:58","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":6426446,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7450097/v1/58d93077-5665-47e4-b9b3-ab1970811555.pdf"}],"financialInterests":"The authors declare no competing interests.","formattedTitle":"\u003cp\u003e\u003cstrong\u003eMicroplastics in surface snow from SE-Dome, southeastern Greenland Ice Sheet\u003c/strong\u003e\u003c/p\u003e","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eThe widespread use of plastic products provides indispensable convenience in modern life, but it has led simultaneously to escalation of global plastic waste problems (e.g., Kibria et al., \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Small plastic particles measuring 5 mm or less in diameter, referred to as microplastics (MPs), are particularly problematic because of their difficulty of retrieval once released. Their resistance to degradation allows them to remain in the environment for long periods, and they also exhibit a high affinity for adsorbing persistent organic pollutants (e.g., Tang, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). In recent years, numerous reports have described the bioaccumulation of MPs, raising increasing concerns related to their potential effects on ecosystems (e.g., Gao et al., \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2024\u003c/span\u003e) and on human health (e.g., Marfella et al., \u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Initially, microplastic (MP) pollution was regarded primarily as a marine issue (e.g., Thompson et al., \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e2004\u003c/span\u003e), but growing evidence confirms that MPs are also ubiquitous in the atmosphere (e.g., Dris et al., \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). Although their detailed mechanisms and pathways remain poorly understood, atmospheric MPs are thought to undergo long-range transport via atmospheric circulation, facilitating their global dispersal (e.g., Allen et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2019\u003c/span\u003e and \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Xiao et al., \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2023\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eSnow and ice of the polar ice sheets, in which deposited aerosols are preserved, can serve as natural aerosol samplers and archives, providing great opportunities to obtain insights into the atmospheric transport of aerosols to polar areas (e.g., Nagatsuka et al., \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Sch\u0026uuml;pbach et al., \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Thomas et al., \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). However, only four studies to date have reported investigations of snow and ice from the polar ice sheets for the analysis of microplastics: an emerging class of aerosols. Pioneering research using micro-Fourier Transform Infrared (micro-FTIR) spectroscopy conducted by Aves and others (2022) provided the first evidence of microplastics (mostly polyethylene terephthalate: PET) in Antarctic snow from the Ross Island region. They reported the average concentrations of MPs (\u0026gt;\u0026thinsp;50 \u0026micro;m) as 29 particles/L. Subsequently, Robini and others (2024) used electron microscopy and micro-Raman spectroscopy to characterize small microparticles and nanoparticles in coastal Antarctic snow. Although they detected polyethylene (PE) and poly(ethylene-co-vinyl-acetate) particles, statistically useful data such as the number concentration and size distribution were not reported. Very recently, observations of MPs in snow samples from Antarctic camps (Union Glacier, Schanz Glacier, and the South Pole) were reported by Jones-Williams and others (2025). Using FTIR imaging, they investigated smaller particles (\u0026gt;\u0026thinsp;11 \u0026micro;m) than those examined for the pioneering research, and detected higher concentrations (817 particles/L on average) of MPs dominated by polyamide, PET, PE and synthetic rubber. For the Greenland Ice Sheet, Materić et al. (\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2022\u003c/span\u003e) conducted an analysis of plastics in a shallow firn core collected near the EastGRIP deep drilling site using Thermal Desorption-Proton Transfer Reaction-Mass Spectrometry. However, the analytical method which was applied was designed to estimate the types and overall quantities of plastics, providing no information at the individual particle level.\u003c/p\u003e\u003cp\u003eBecause of scant field data, as introduced above, little is known even about the features of microplastics in snow and ice from the ice sheets. This report describes the first direct finding of microplastics in Greenland snow. Using an integrated approach combining fluorescence microscopy and micro-FTIR spectroscopy, we investigated the abundance, polymer type, size, and shape of MPs (\u0026gt;\u0026thinsp;10 \u0026micro;m) in surface snow from the southeastern dome (SE-Dome) of the Greenland Ice Sheet.\u003c/p\u003e"},{"header":"2. Experimental","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e\u003ch2\u003e2.1. Snow sampling\u003c/h2\u003e\u003cp\u003eOn May 31, 2021, surface snow, upper 55 cm, was collected at the SE-Dome of the Greenland ice sheet (67˚19ʹ N, 36˚ 47ʹ W, 3161 m a.s.l.), during the ice-core drilling expedition (Iizuka et al., \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). After a 40\u0026times;39\u0026times;55 cm\u003csup\u003e3\u003c/sup\u003e snow block was extracted from a side wall of a snow pit with a snow saw, the snow block was put into and closed up within a large polyethylene bag. Sampling was conducted downwind at all times. The bagged snow block, which was packed in an insulated polystyrene box, was shipped to Japan at \u0026minus;\u0026thinsp;25 \u0026ordm;C. After arrival at our institute, the snow block was stored in a freezer set at \u0026minus;\u0026thinsp;50 \u0026ordm;C until sample preparation preceding measurement.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec4\" class=\"Section2\"\u003e\u003ch2\u003e2.2. Sample preparation\u003c/h2\u003e\u003cp\u003eHalf of the snow block (40\u0026times;20\u0026times;55 cm\u003csup\u003e3\u003c/sup\u003e) was used for this study. In a clean bench installed in a cold room set at \u0026minus;\u0026thinsp;20 \u0026ordm;C, using a ceramic knife, the outer sides (more than 5 cm thickness) of the half snow block were removed for decontamination. Then the remaining inner part of snow was transferred into a glass bottle with a stainless-steel grain scoop. In all, three bottles of samples were prepared.\u003c/p\u003e\u003cp\u003eSnow samples were thawed at room temperature in the closed glass bottles. Approximately 250 mL of each thawed sample (all water in a bottle) was filtered onto an aluminum oxide filter (25 mm diameter, 0.2 \u0026micro;m pore size, Anodisc; Whatman plc.) using a vacuum filtration apparatus made of glass. With the filter still attached to the apparatus, approximately 30 mL of 30% H\u003csub\u003e2\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e was poured in a glass funnel of the apparatus. The funnel opening was covered with aluminum foil. After the solution was left for 1 day at room temperature to remove natural organic matter adhered to MPs (Liebezeit and Dubaish, \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2012\u003c/span\u003e), the solution was filtered with the apparatus. After finishing the filtration of approximately 50 mL of ultra-pure water (18 MΩཥcm), the filter was removed from the apparatus. It was then dried in a glass petri dish. All processes described above were performed in a clean booth with a HEPA filtration unit.\u003c/p\u003e\u003cp\u003eFor this study, Anodiscs were washed before use for decontamination. After the Anodiscs were sonicated in acetone for five minutes and rinsed with the ultra-pure water, these filters were dried in glass petri dishes. Although earlier works by the authors (Ohno and Iizuka, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2023\u003c/span\u003e, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2024\u003c/span\u003e) have shown that noticeable numbers of microparticles including MPs are always present on brand-new Anodiscs, irrespective of the production lot, the pre-cleaning described above can remove inherent particles from a filter thoroughly.\u003c/p\u003e\u003cp\u003eAnother important procedure newly adopted for this study is fluorescent staining of residual particles on a filter for rapid screening of suspected plastic particles (Erni-Cassola et al., \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Maes et al., \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e2017\u003c/span\u003e; Shim et al., \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2016\u003c/span\u003e). As a final step of sample preparation, using a syringe filter, three drops of an acetone solution of Nile red (10 \u0026micro;g/mL) were dripped on each filter in the clean booth. It was then dried in a glass petri dish. Nile red is a fluorescent lipophilic dye originally applied for detection and quantification of intracellular lipids in the field of biology (Greenspan et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e1985\u003c/span\u003e). Because of the hydrophobic nature of common plastics, Nile red is adsorbed selectively onto the surfaces of MPs. By contrast, hydrophilic mineral particles, which dominate residues on a filter, are not dyed to any marked degree by Nile red.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e\u003ch2\u003e2.3. Fluorescence microscopic observation\u003c/h2\u003e\u003cp\u003eAfter a prepared filter was placed in an optical petri dish made of quartz, it was inspected through a quartz optical window using a fluorescence microscope (CX41FL; Olympus Corp.) under blue light excitation (475 nm center wavelength). Our earlier work with conventional optical microscopy (Ohno and Iizuka, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2023\u003c/span\u003e, \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2024\u003c/span\u003e) examined only particles larger than 30 \u0026micro;m, but even smaller particles can be analyzed reasonably using fluorescence microscopy by virtue of enhanced visibility. By observing the entire filter surface, we found all fluorescent particles larger than 10 \u0026micro;m to be targets of micro-FTIR analysis. Then we recorded their coordinate positions on a filter. The shapes of these particles were classified as fragments (e.g., Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea) or fibers (e.g., Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb). Targeted particles were photographed under both white light and fluorescence using a digital camera (EOS Kiss X9; Canon Inc.) attached to the microscope. Then their maximum diameters or lengths were measured by analyzing micrographs using image-processing software (ImageJ; NIH). Micrographs of typical particles are presented in Figs.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ea and \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003eb.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec6\" class=\"Section2\"\u003e\u003ch2\u003e2.4. Micro-FTIR analysis\u003c/h2\u003e\u003cp\u003eChemical identifications of microparticles were accomplished using micro-FTIR. All targeted particles on filters were analyzed using an FTIR microscope (Nicolet iN10; Thermo Fisher Scientific K.K.) in transmission mode with the following parameters: 10 \u0026micro;m \u0026times; 10 \u0026micro;m (or 20 \u0026micro;m \u0026times; 20 \u0026micro;m) square field aperture, 4 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e spectral resolution, 128 (or 256) scans, and 1250\u0026ndash;3600 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e spectral range. The obtained FTIR spectra were subsequently compared with the commercial spectral databases of standard polymers (Hummel Polymer sample Library and HR Polymer and additives) and also with open-access libraries designed for MP research, which includes spectra of aged plastics (Chabuka and Kalivas, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Cowger et al., \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; De Frond et al., \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Primpke et al., \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2018\u003c/span\u003e), using spectroscopy software (OMNIC Picta; Thermo Fisher Scientific K.K.). Spectra with a match of \u0026lt;\u0026thinsp;60% were rejected, whereas when returning a spectral match of \u0026gt;\u0026thinsp;60%, an additional visual examination of spectra was performed manually, leading to final acceptance or rejection (Kanhai et al., \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Obbard et al., \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e2014\u003c/span\u003e; Yang et al., \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). FTIR spectra of typical particles are presented in Figs.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ec and \u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003ed.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e\u003ch2\u003e2.5. Blank test\u003c/h2\u003e\u003cp\u003eBlank tests were conducted to assess the validity of methods. During inner-snow extraction in the clean bench, an uncovered empty glass bottle was put beside the snow block until the work was finished. It was then closed with a lid. After the blank bottle was filled with ultra-pure water, it was processed using the same procedures as those used for the snow samples. In all, two blanks were tested. Observations of blank-filter surfaces with the fluorescence microscope revealed several fluorescent particles on blank samples. Subsequent micro-FTIR analyses of these fluorescent particles detected one polystyrene from the first blank, and no MPs from the second one. The averaged MP abundance on a blank filter (0.5 particle/filter) was two orders of magnitude lower than that on a snow-filtered filter (14 particles/filter). Therefore, almost all MPs detected in measurements of snow-filtered filters are regarded as originating from the snow samples. Because the sampled inner sections of the snow block were never exposed directly to contamination during fieldwork, transport, or storage, field blanks were not taken (Materić et al., \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2022\u003c/span\u003e).\u003c/p\u003e\u003c/div\u003e"},{"header":"3. Results","content":"\u003cdiv id=\"Sec9\" class=\"Section2\"\u003e\u003ch2\u003e3.1. Particle composition\u003c/h2\u003e\u003cp\u003eCompositions of fluorescent particles from snow samples are depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003ea. For Sample-1 and Sample-3, the dominant composition was other organic matter except MP, cellulose, and protein, accounting for 67% of all fluorescent particles on average. In contrast, for Sample-2, fluorescent particles were dominated by cellulose (66%) instead of other organic matter. Actually, MPs were detected from all snow samples as the second highest composition, with MP composition ratios of 17\u0026ndash;29%, averaging 23%.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eCompositions of MPs in each snow sample are depicted in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb. Overall, plastic polymers of nine types were detected from microparticles: alkyd, polyethylene terephthalate (PET), rubber, polystyrene (PS), acrylic, polyurethane (PU), polyethylene (PE), polyvinyl chloride (PVC), and polycarbonate (PC). Also, MP types were found to depend on the snow samples (Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb): MPs in Sample-1 were mostly alkyd, whereas other plastic species such as PET, rubber, and PS were also often observable for other samples.\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec10\" class=\"Section2\"\u003e\u003ch2\u003e3.2. Microplastic abundance\u003c/h2\u003e\u003cp\u003eAbundances of microplastics in snow samples were estimated from the numbers of MPs on filters and the volumes of water samples (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The observed concentrations of MPs were 45\u0026ndash;64 particles/L (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The average value and the coefficient of variation of the MP abundances were, respectively, 54 particles/L and 17%. In fact, these MP concentrations were two orders of magnitude lower than those estimated using exactly the same methods for fresh snow from a protected area (Lake Chimikeppu) in Hokkaido, the northern island of Japan (not shown).\u003c/p\u003e\u003cp\u003e\u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eFiltered volumes of melted snow samples, numbers of fluorescent particles (\u0026gt;\u0026thinsp;10 \u0026micro;m) on filters, numbers of MPs (\u0026gt;\u0026thinsp;10 \u0026micro;m) on filters, and abundances of MPs (\u0026gt;\u0026thinsp;10 \u0026micro;m)\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSample code\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eFiltered volume\u003c/p\u003e\u003cp\u003e(mL)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNumber of fluorescent particles\u003c/p\u003e\u003cp\u003e(particles/filter)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eNumber of MPs\u003c/p\u003e\u003cp\u003e(particles/filter)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eMP abundance\u003c/p\u003e\u003cp\u003e(particles/L)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSample-1\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e250.0\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e56\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e16\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e64\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSample-2\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e260.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e56\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e14\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e54\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSample-3\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e\u003cp\u003e243.9\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e\u003cp\u003e65\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e\u003cp\u003e11\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e\u003cp\u003e45\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/colgroup\u003e\u003c/table\u003e\u003c/div\u003e\u003c/p\u003e\u003c/div\u003e\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\u003ch2\u003e3.3. Microplastic composition, size, and shape\u003c/h2\u003e\u003cp\u003eObserved frequencies of MPs from snow samples are portrayed in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e for various MP types in different size classes. The averaged values of polymer compositions of MPs are presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea. Alkyd, PET, rubber, and PS were the dominant compositions of MPs in the snow samples, accounting for 83%. Among these components, alkyd, PET, and rubber particles were observed in all samples, whereas PS particles were detected in specific samples (Figs.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb and \u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eFor all samples, MPs were mainly in the 10\u0026ndash;50 \u0026micro;m size range in maximum diameter or length (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e). As a general trend, most alkyd, rubber, and PS particles were of the size class of less than 40\u0026ndash;50 \u0026micro;m, whereas PET particles were distributed in wide size ranges. Size distributions of fragment and fiber microplastics are presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb. The shapes of MPs from snow samples were mostly fragments, accounting for 83%. More than 97% of fragment MPs had smaller maximum diameter than 50 \u0026micro;m, whereas most fiber MPs had greater than 50 \u0026micro;m length. Fragment MPs consisted of all types of plastic polymers except for acrylic, whereas fiber MPs comprised PET and acrylic.\u003c/p\u003e\u003c/div\u003e"},{"header":"4. Discussion","content":"\u003cp\u003eAs presented in the preceding section, the features (especially compositions) of MPs depend on snow samples, possibly because of differences in snow depth (not measured), specifically differences in timing of MP deposition. However, this variation might be attributed partly to the small sample sizes (\u003cem\u003en\u003c/em\u003e in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e2\u003c/span\u003eb).\u003c/p\u003e\u003cp\u003eThe described properties and abundances of MPs in Greenland and Antarctic snows reported to date differ considerably (Aves et al., \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2022\u003c/span\u003e; Jones-Williams et al., \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2025\u003c/span\u003e; Riboni et al., \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). Although Zhang and others (2022) pointed out in their review article that this diversity might be attributable more to differences in sampling and analytical methods used than to actual regional differences, we strove to extract meaningful information by comparing our results with those reported from earlier studies.\u003c/p\u003e\u003cp\u003eAccording to detailed estimations of MP abundance for Antarctic snow samples obtained near the Union Glacier and the South Pole (Jones-Williams et al., \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2025\u003c/span\u003e), for particles larger than 11 \u0026micro;m, the MP concentrations were estimated on average as 817 particles/L. Despite having a similar detection limit (10 \u0026micro;m in our case), this averaged value is one order of magnitude larger than that of ours (54 particles/L). This discrepancy may be attributable to the difference in remoteness from human activities. The Union Glacier and the South Pole not only host research stations and camps: these are also popular spots for Antarctic land tours. In contrast, the SE-Dome is truly deserted (see the subsection of this section before the last). Another possible cause is the different analytical methods used for MP detection. Jones-Williams and others (2025) analyzed all residues on a filter using a FPA-based micro-FTIR imaging, whereas only fluorescent (i.e., hydrophobic) particles were targeted for micro-FTIR analysis in the present work, which might lead to some degree of underestimation of MP abundance. In some cases, the hydrophobic nature of plastic is altered to be hydrophilic during the manufacturing process by surface treatments or additives (Song et al., 2023; Zhang et al., \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2025\u003c/span\u003e). Moreover, the degree of MP hydrophobicity can be decreased as a result of UV-weathering (Alimi et al., \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Yu et al., \u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e2024\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThe most frequent polymer type we detected was alkyd (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea), which is widely used mainly in paint and coating applications. The presence of alkyd particles was confirmed earlier not only in Antarctic snow samples from the Ross Island region (Aves et al., \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2022\u003c/span\u003e), but also in both Arctic sediment and seawater (Kim et al., \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2023\u003c/span\u003e). Other dominant polymer types examined for this work were PET, rubber, and PS (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003ea). These compositions were often observable in Greenland (Materić et al., \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2022\u003c/span\u003e) and Antarctic (Jones-Williams et al., \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2025\u003c/span\u003e) snow samples. Although the three polymer types were also detected in Arctic marine environments (Kim et al., \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2023\u003c/span\u003e), a very recent analysis of MPs in subsurface water from the fjords of Tunu (East Greenland) with laser direct infrared (LDIR) imaging showed that PET was predominant over all other polymer species (Vetter et al., \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e2025\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eThe size distribution of microplastics observed in this study (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb) is consistent with general trends reported from the earlier work in Antarctica (Jones-Williams et al., \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2025\u003c/span\u003e): MPs in snows from the Union Glacier and the South Pole regions were generally smaller than 50 \u0026micro;m; the number of MPs observed generally increased concomitantly with decreasing size. In terms of morphology, as observed from this work (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e4\u003c/span\u003eb), non-fibers (particulates) were the dominant shape in microplastics from the Antarctic snows (Jones-Williams et al., \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2025\u003c/span\u003e), accounting for 79% (in our case 83%). Similar results for MP size and shape have been reported for snow/precipitation samples worldwide (Allen et al., \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Bergmann et al., \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Klein and Fischer, \u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e2019\u003c/span\u003e; Ohno and Iizuka, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Zhang et al., \u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e2021\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eNo major source of plastics exists near the SE-Dome. Moreover, this remote site is located at a higher altitude (3161 m a.s.l.) than the atmospheric boundary layer. From these reasons, the observed MPs are regarded as deriving from long-distance atmospheric transportation. Aerosols of various types such as mineral dust, sulfate, nitrate, and black carbon are well known to be brought to Greenland and then deposited on the ice sheet by atmospheric circulation in the troposphere (e.g., Nagatsuka et al., \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2021\u003c/span\u003e; Sch\u0026uuml;pbach et al., \u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e2018\u003c/span\u003e; Thomas et al., \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2017\u003c/span\u003e). Similar long-range atmospheric transport is expected to have occurred with microplastics. Allen et al. (\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2021\u003c/span\u003e) reported observational evidence for the presence of microplastics in the free troposphere at the Pic du Midi Observatory (2877 m a.s.l), in southeastern France, and suggested that these MPs can be transported at an intercontinental (or trans-oceanic) scale based on the air mass and particle history calculated with atmospheric transport and particle dispersion models. Compared to microplastics with some other shape, fiber MPs are regarded as remaining in the atmosphere for a longer period of time because of their shape. Reportedly, they are more likely to be transported a longer distance: recently Xiao et al. (\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2023\u003c/span\u003e) developed a theory-based settling velocity model for fiber MPs in the atmosphere, predicting their mean residence-time enhancement as greater than 450% compared to spherical particles. For the case of the SE-Dome, backward trajectory analyses suggest that the primary origin of air mass is North America, followed in importance by Europe and Russia (Iizuka et al., \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2018\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eIn addition to remote terrestrial environments, seas and oceans might be other important sources for microplastics. Allen et al. (\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2020\u003c/span\u003e) conducted a pilot investigation of marine boundary layer air samples on the French Atlantic coast. They detected a considerable number of microplastics especially in oceanic air dominated by sea spray, suggesting that MPs are released actively from the marine environment into the atmosphere by sea spray. Increasing evidence has pointed to the importance of this phenomenon as a major secondary source of microplastics. For instance, using in situ observations of MP deposition combined with an atmospheric transport model and optimal estimation techniques, Brahney et al. (\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2021\u003c/span\u003e) tested hypotheses of the most likely sources of atmospheric plastic. They concluded that oceans dominated plastic sources on a global scale, accounting for 99% of the deposition to oceans and 7% of the deposition to land surfaces away from coastal regions. In relation to this finding, sea-salt particles emitted from seas and oceans are commonly observable in Greenland snow and ice, even in the interior of the ice sheet (e.g., Oyabu et al., \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eContamination by research activities is regarded as minimal at the SE-Dome because this location is a temporal observation site. Furthermore, the Summit Camp, the nearest year-round staffed research station on the ice sheet operated by the United States, is approximately 600 km distant from the SE-Dome. Of course, no tourists are present there.\u003c/p\u003e\u003cp\u003eTo elucidate the state of airborne-MP deposition on the ice sheet, i.e., for better understanding of the nature and mechanism of the long-distance atmospheric transport of MPs, systematic field work for wide area observations across various geographical settings and further experimentation must be conducted.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eAcknowledgements\u003c/h2\u003e\u003cp\u003eH.O. gratefully appreciates technical assistance with the experiment setup provided by Tadahisa Yamada and Shinya Ishizawa, and thanks all participants in the fieldwork for their support in snow sampling. This study was supported by MEXT/JSPS KAKENHI Grants: Nos. 23H00511 and 24H00760.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAlimi OS, Claveau Mallet D, Lapointe M, Biu T, Liu L, Hernandez LM et al (2023) Effects of weathering on the properties and fate of secondary microplastics from a polystyrene single-use cup. J Hazard Mater 459:131855. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.jhazmat.2023.131855\u003c/span\u003e\u003cspan address=\"10.1016/j.jhazmat.2023.131855\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAllen S, Allen D, Phoenix VR, Le Roux G, Dur\u0026acute;antez Jim\u0026acute; enez P, Simonneau A, Binet S, Galop D (2019) Atmospheric transport and deposition of microplastics in a remote mountain catchment. 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J Hazard Mater 483:136667. \u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttps://doi.org/10.1016/j.jhazmat.2024.136667\u003c/span\u003e\u003cspan address=\"10.1016/j.jhazmat.2024.136667\" targettype=\"DOI\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"Kitami Institute of Technology","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"Microplastic, Surface snow, Greenland Ice Sheet","lastPublishedDoi":"10.21203/rs.3.rs-7450097/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7450097/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe polar ice sheets can be regarded as samplers and archives of deposited aerosols, including microplastics (MPs). Nevertheless, there are very few examples to date of studies of MPs in snow from ice sheets. We have conducted preliminary investigations of MPs (\u0026gt;\u0026thinsp;10 \u0026micro;m) in surface snow from the southeastern dome (SE-Dome) of the Greenland Ice Sheet. Analyses combining fluorescence microscopy and micro-Fourier Transform Infrared (micro-FTIR) spectroscopy detected nine microplastic (MP) types, mostly with fragmentary shapes. Almost all fragmentary MPs were smaller than 50 \u0026micro;m, but most fiber MPs were in the larger size classes (\u0026gt;\u0026thinsp;50 \u0026micro;m). The number of MPs observed generally increased concomitantly with decreasing size. The MP concentrations were 45\u0026ndash;64 particles/L, with an average of 54 particles/L. These findings suggest important implications for better understanding of the nature and mechanism of the long-distance atmospheric transport of MPs.\u003c/p\u003e","manuscriptTitle":"Microplastics in surface snow from SE-Dome, southeastern Greenland Ice Sheet","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-26 11:17:44","doi":"10.21203/rs.3.rs-7450097/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"8fa31979-cb01-4f51-95a0-bc80799d8e00","owner":[],"postedDate":"August 26th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2025-08-26T11:17:44+00:00","versionOfRecord":[],"versionCreatedAt":"2025-08-26 11:17:44","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7450097","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7450097","identity":"rs-7450097","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}