Atmospheric transport and deposition of microplastics in a remote mountain catchment
Abstract and Figures
Plastic litter is an ever-increasing global issue and one of this generation’s key environmental challenges. Microplastics have
reached oceans via river transport on a global scale. With the exception of two megacities, Paris (France) and Dongguan
(China), there is a lack of information on atmospheric microplastic deposition or transport. Here we present the observations
of atmospheric microplastic deposition in a remote, pristine mountain catchment (French Pyrenees). We analysed samples,
taken over five months, that represent atmospheric wet and dry deposition and identified fibres up to ~750 µm long and frag-
ments ≤300 µm as microplastics. We document relative daily counts of 249 fragments, 73 films and 44 fibres per square
metre that deposited on the catchment. An air mass trajectory analysis shows microplastic transport through the atmosphere
over a distance of up to 95 km. We suggest that microplastics can reach and affect remote, sparsely inhabited areas through
atmospheric transport.
Figures - available from: Nature Geoscience
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... The accumulation of macro-plastics and MPs waste in soils is the result of various human activities and environmental origins, such as discarded plastic litter (Rillig, 2012), plasticulture practices (e.g. plastic mulch films, greenhouse films, irrigation pipes, and associated infrastructure) (Bläsing & Amelung, 2018, Gündoğdu et al., 2022Huang et al., 2020;Wang et al., 2022), sewage sludge application (Long et al., 2019), coated fertilizers (Katsumi et al., 2021), organic fertilizer and agricultural compost (Weithmann et al., 2018), atmospheric deposition (Allen et al., 2019), digested food waste (Porterfield et al., 2023), and rubber tire wear (Evangeliou et al., 2020). Of these, plastic films represents an important source of macro-plastics and MPs in agricultural soils and has attracted extensive research and discussion (Qi et al., 2020). ...
... Atmospheric transport and deposition of MPs is one of the major pathways for plastic fragments entering the soil environment (Allen et al., 2019;Brahney et al., 2020). It is estimated that atmospheric deposition rates of MPs range from 1.1 × 10 4 to 4.1 × 10 5 items m −2 yr −1 globally (Allen et al., 2019;Bergmann et al., 2019;Brahney et al., 2020). ...
... Atmospheric transport and deposition of MPs is one of the major pathways for plastic fragments entering the soil environment (Allen et al., 2019;Brahney et al., 2020). It is estimated that atmospheric deposition rates of MPs range from 1.1 × 10 4 to 4.1 × 10 5 items m −2 yr −1 globally (Allen et al., 2019;Bergmann et al., 2019;Brahney et al., 2020). These particles typically enter the atmosphere through mechanical processes, such as dust entrainment during strong wind events or wave breaking of sea surface spray (Seinfeld et al., 1998). ...
... In addition, plastic 188 products contain a large amounts of plastic additives [83]. The possibility of atmospheric migration of MPs has been demonstrated [7,85,86], 212 as indicated by the discovery of MPs (fibers up to 750 µm and fragments ≤ 300 µm) in 213 remote atmospheres that are at least 6 km away from the original sources [87]. Owing 214 to their low densities, plastic particles can persist in the air for extended periods, 215 facilitating their effortless dissemination to distant destinations [88]. ...
... The ubiquitous presence of microplastics, often defined as plastics smaller than 5 mm in size, imposes multiple threats to the sustainability of aquatic and terrestrial environments and ecosystems 1 . The accumulation and transport of microplastics in water bodies have been well documented in previous studies 2 , but increasing evidence from recent studies has highlighted the importance of the atmosphere as an equally important medium and transport pathway in the plastic cycle [3][4][5][6][7] . Their hazardous impacts could be further exacerbated as they progressively penetrate through the global environments and ecosystems via environmental transport 4,8 . ...
Recent studies have highlighted the importance of the atmosphere in the long-range transport of microplastic fibres. However, their dry deposition in the atmosphere is not fully understood, with the common spherical-shape assumption leading to significant uncertainties in predicting their travel distance and atmospheric residence time. Shapes of microplastic fibres vary greatly, which can be as long as 100 μm and as thin as 2 μm. Shapes of microplastic fibres may greatly affect their dry deposition in the atmosphere. Here we develop a theory-based settling velocity model for simulating atmospheric transport of microplastic fibres in different sizes and shapes. The model predicts a smaller aerodynamic size of microplastic fibres than that estimated by using volumetrically equivalent spherical counterparts. We find that the treatment of flat fibres as cylindrical ones, due to uncertainty in dimensions of sampled microplastic fibres, would cause overestimation of their dry deposition rate. Accounting for fibre thickness in sampled microplastic fibres leads to a mean enhancement of residence time by more than 450% compared to cylindrical ones. The results suggest a much more efficient long-range transport of flat fibres than previously thought.
... Due to the limited number of studies and restricted extent of global observation, there is still a limited representation of MP concentrations worldwide. Microplastics have been found in the sediment, sea surface, and sea ice of the Arctic Ocean [6,7,[11][12][13][14] and are likely to come from ocean currents of Pacific and Atlantic origin as well as from atmospheric deposition [15,16]. Long-distance transport to remote regions could occur through a combination of atmospheric and marine conveyance [17,18], facilitating the global spread of MPs. ...
Microplastic pollution has emerged as a global environmental concern, exhibiting wide distribution within marine ecosystems, including the Arctic Ocean. Limited Arctic microplastic data exist from beached plastics, seabed sediments, floating plastics, and sea ice. However, no studies have examined microplastics in the sea ice of the Canadian Arctic Archipelago and Tallurutiup Imanga National Marine Conservation Area, and few have explored Arctic marginal seas’ water column. The majority of the microplastic data originates from the Eurasian Arctic, with limited data available from other regions of the Arctic Ocean. This study presents data from two distinct campaigns in the Canadian Arctic Archipelago and Western Arctic marginal seas in 2019 and 2020. These campaigns involved sampling from different regions and matrices, making direct comparisons inappropriate. The study’s primary objective is to provide insights into the spatial and vertical distribution of microplastics. The results reveal elevated microplastic concentrations within the upper 50 m of the water column and significant accumulation in the sea ice, providing evidence to support the designation of sea ice as a microplastic sink. Surface seawater exhibits a gradient of microplastic counts, decreasing from the Chukchi Sea towards the Beaufort Sea. Polyvinyl chloride polymer (~60%) dominated microplastic composition in both sea ice and seawater. This study highlights the need for further investigations in this region to enhance our understanding of microplastic sources, distribution, and transport.
... Glaciers are particularly efficient at concentrating small particles from the air [85] . They provide interesting natural freezing and thawing events that involve the uptake and release of MPs. ...
Microplastics (MPs) have been detected in many parts of the world in snow, hail, sea ice, glaciers, and permafrost. The ubiquity of microplastic around the globe means that there is a need to focus on its circulation dynamics in the Earth's diverse ecosystems; the prominence of MP fibers, which has been indicated as of human clothing and activities, in high altitude frozen water is explained by their enhanced suspension in the air, allowing them to be transported over long distances from urban centers. The MP particles can act as nucleation centers for ice crystals and, once incorporated, reduce the albedo (reflective capacity) of the frozen mass, causing temperature increases. However, cores have indicated that ice in glaciers may remain frozen for thousands of years. This article reviews the quantities and types of MPs that have been detected in snow, hail, sea ice, and glaciers. The potential for release of these, as well as MPs in the permafrost, following global warming, is discussed. As the global warming process evolves, these sites will act as additional sources of MPs accumulated over the course of recent human history. It is important to be aware of the future entry of microplastic into the global environment from these sources, especially into the already fragile extreme ecosystems of the cryosphere.
The global scale of concern regarding indoor microplastic (MP) pollution is increasing and considering the amount of time people spend indoors. Indoor MP contamination can directly affect the human population through indoor dust and air exposure. This review summarized recent research progress on pretreatments, quality control, filter membranes, identification, keywords used, publication record, and authors' contribution. Comparatively, dust and deposition samples exhibit higher MPs concentrations than indoor air samples. Fiber-shaped MPs are commonly detected indoors, although fragments and films are also present. The color and types of MPs display variability, with polypropylene, polyethylene, polyethylene terephthalate, and polystyrene identified as the dominant MPs. Indoor environments generally demonstrate higher concentrations of MPs than outdoor environments, and MPs in the lower size range (1–100 µm) are typically more abundant. Among the reviewed articles, 45.24% conducted pretreatment on their samples, while 16.67% did not undergo any pretreatment. The predominant filter utilized in most studies was the Whatman Glass microfiber filter (41.67%), and MPs were predominantly characterized using µ-FTIR (19.23%). Within the examined literature, 17 articles incorporated blank samples into their research, while 8 articles did not include blank samples. Notably, most studies (23) did not integrate blank results into their samples. A significant increase in published articles has been observed since 2020, with an annual growth rate exceeding 10%. Bibliometric analysis of the literature review identified 35 authors who have contributed relevant material on indoor MPs. The keyword microplastics had the highest frequency, followed by fibers.
A single-step hydrodeoxygenation (HDO) over a Ru/TiO 2 catalyst in the water/dodecane biphasic system allows for the quantitative conversion of polyethylene terephthalate (PET) to gasoline- and jet fuel-range C 6 –C 8 cyclic hydrocarbons.
Giant mineral dust particles (>75 μm in diameter) found far from their source have long puzzled scientists. These wind-blown particles affect the atmosphere’s radiation balance, clouds, and the ocean carbon cycle but are generally ignored in models. Here, we report new observations of individual giant Saharan dust particles of up to 450 μm in diameter sampled in air over the Atlantic Ocean at 2400 and 3500 km from the west African coast. Past research points to fast horizontal transport, turbulence, uplift in convective systems, and electrical levitation of particles as possible explanations for this fascinating phenomenon. We present a critical assessment of these mechanisms and propose several lines of research we deem promising to further advance our understanding and modeling.
Microplastics (MP) are recognized as a growing environmental hazard and have been identified as far as the remote Polar Regions, with particularly high concentrations of microplastics in sea ice. Little is known regarding the horizontal variability of MP within sea ice and how the underlying water body affects MP composition during sea ice growth. Here we show that sea ice MP has no uniform polymer composition and that, depending on the growth region and drift paths of the sea ice, unique MP patterns can be observed in different sea ice horizons. Thus even in remote regions such as the Arctic Ocean, certain MP indicate the presence of localized sources. Increasing exploitation of Arctic resources will likely lead to a higher MP load in the Arctic sea ice and will enhance the release of MP in the areas of strong seasonal sea ice melt and the outflow gateways.
Microplastic contamination of the oceans is one of the world’s most pressing environmental concerns. The terrestrial component of the global microplastic budget is not well understood because sources, stores and fluxes are poorly quantified. We report catchment-wide patterns of microplastic contamination, classified by type, size and density, in channel bed sediments at 40 sites across urban, suburban and rural river catchments in northwest England. Microplastic contamination was pervasive on all river channel beds. We found multiple urban contamination hotspots with a maximum microplastic concentration of approximately 517,000 particles m−2. After a period of severe flooding in winter 2015/16, all sites were resampled. Microplastic concentrations had fallen at 28 sites and 18 saw a decrease of one order of magnitude. The flooding exported approximately 70% of the microplastic load stored on these river beds (equivalent to 0.85 ± 0.27 tonnes or 43 ± 14 billion particles) and eradicated microbead contamination at 7 sites. We conclude that microplastic contamination is efficiently flushed from river catchments during flooding.
Aerosolization of soil-dust and organic aggregates in sea spray facilitates the long-range transport of bacteria, and likely
viruses across the free atmosphere. Although long-distance transport occurs, there are many uncertainties associated with
their deposition rates. Here, we demonstrate that even in pristine environments, above the atmospheric boundary layer, the
downward flux of viruses ranged from 0.26 × 109 to >7 × 109 m−2 per day. These deposition rates were 9–461 times greater
than the rates for bacteria, which ranged from 0.3 × 107 to >8 × 107 m−2 per day. The highest relative deposition rates for
viruses were associated with atmospheric transport from marine rather than terrestrial sources. Deposition rates of bacteria
were significantly higher during rain events and Saharan dust intrusions, whereas, rainfall did not significantly influence
virus deposition. Virus deposition rates were positively correlated with organic aerosols <0.7 μm, whereas, bacteria were
primarily associated with organic aerosols >0.7 μm, implying that viruses could have longer residence times in the
atmosphere and, consequently, will be dispersed further. These results provide an explanation for enigmatic observations
that viruses with very high genetic identity can be found in very distant and different environments.
Widespread microplastic pollution is raising growing concerns as to its detrimental effects upon living organisms. A realistic risk assessment must stand on representative data on the abundance, size distribution and chemical composition of microplastics. Raman microscopy is an indispensable tool for the analysis of very small microplastics (<20 μm). Still, its use is far from widespread, in part due to drawbacks such as long measurement time and proneness to spectral distortion induced by fluorescence. This review discusses each drawback followed by a showcase of interesting and easily available solutions that contribute to faster and better identification of microplastics using Raman spectroscopy. Among discussed topics are: enhanced signal quality with better detectors and spectrum processing; automated particle selection for faster Raman mapping; comprehensive reference libraries for successful spectral matching. A last section introduces non-conventional Raman techniques (non-linear Raman, hyperspectral imaging, standoff Raman) which permit more advanced applications such as real-time Raman detection and imaging of microplastics.
Microplastics (MPs) are small (<5 mm diameter) but have clear implications for the environment. These artificial particles are found in and pose threats to aquatic systems worldwide. MPs have terrestrial sources, but their concentrations and fates in the terrestrial environment are poorly understood. Whilst global plastic production continues to increase, so do the environmental concentrations and impacts of MPs. In this first study of MPs in floodplain soils, we developed a method for identifying, quantifying, and measuring the sizes of most commonly produced MPs in soil by FT-IR microscopy. For small MP (<1mm) analysis, MP were separated by density separation and oxidation of organic matter. In this study we analyzed 29 floodplains in Swiss nature reserves associated with catchments covering 53% of Switzerland. We found evidence that 90% of Swiss floodplain soils contain MPs. The highest MP concentrations were associated with the concentration of mesoplastics (5 mm – 2.5 cm diameter), indicating plastic waste as source. Furthermore, MP concentration was correlated with the population of the catchment. The wide distribution of MPs, their presence in remote unsettled high mountain areas, decoupling of MEP and MP compositions, and the dominance of MPs by small (<500 µm diameter) particles, indicate that MPs enter soils via diffuse aeolian transport.
Initial reports on the presence of microplastics in the Ocean date from the 1970's. In spite of the noted potential risks these debris posed to both the environment and humans, the scientific community paid little attention to then raised alarms. Recently, however, there has been an increasing interest by both the general public and the scientific community in the contamination and pollution of the marine environment by micro- and nanoplastic particles.
Due to their physical and chemical characteristics, these pervasive contaminants can be found across the Globe and are distributed across the water column and have been shown to be ingested by numerous organisms. Although generally considered biochemically inert, such materials can adsorb other chemical substances, such as persistent organic pollutants (POPs), hence potentially leading to bioaccumulation and bioamplification phenomena.
However, despite this recognized harmfulness, and although microplastics are a recognized threat to the “Blue Economy”, there are still multiple research gaps that should be adequately addressed, in order to obtain a realistic assessment of their prevalence in the environment. Additionally, despite the numerous national, regional and international regulatory instruments aiming at reducing the contamination by plastic litter, these appear to have been, so far, insufficient for reaching their proposed goal. Herein, the current gaps in micro- and neoplastic research and regulation are evaluated and some suggestions for overcoming such limitations are proposed.