Transport Of Microplastics Research Articles

Microplastic fluxes in a large and a small Mediterranean river catchments: The Têt and the Rhône, Northwestern Mediterranean Sea.

This paper aims at quantifying current riverine fluxes of microplastics (MPs) in two Mediterranean river catchments, a large one and a small one, namely the Rhône and the Têt, which are discharging to the Gulf of Lion in the Northwestern Mediterranean Sea. MP fluxes change markedly through time and space in both river systems. However, no clear relationships between MP concentrations and hydroclimatic conditions have been observed. In the Rhône River a non-linear dilution pattern of MPs in total suspended matter (TSM) during flood conditions could be observed. Although dilution is important, samples during floods exert a strong control on average MP fluxes. Compared to the Rhône River, average MP concentrations in the Têt River were throughout greater and more variable in shape and polymer composition. However, as the study year was exceptionally dry, the average specific MP flux, 76gkm-2y-1, is only slightly larger than the non-flooding value of the Rhône River. We further monitored MP concentrations in shoreline sediments at the mouth of the Têt River to test whether these sediments can represent MP transport in the river. Besides fibers, which probably are easily washed out and transported offshore, MP concentrations and compositions are in agreement with MP loads upstream the river. We also examined the potential role of atmospheric deposition as a source of MP to the Têt River. The average atmospheric MP deposition of 6kgkm-2 y-1 exceeds by far the river average specific MP flux. Moreover, all MPs in atmospheric deposits were fibers, which in terms of mass are of minor importance in the bulk river fluxes. Atmospheric MP deposits may either have been overestimated and/or may be removed from surface waters by efficient removal processes (such as waste water treatment plants).

The flowing of microplastics was accelerated under the influence of artificial flood generated by hydropower station

Rivers are considered the most important channel for microplastics traveling to the ocean from inland. The Yellow River is one of a main microplastics source for the Bohai Sea. As hydropower station operations—especially the artificial flood pulse—could significantly affect the transportation processes of microplastics, it is necessary to investigate the transportation regulation of microplastics from the Yellow River to the estuary. In this study, the distribution of microplastics (across 10 sections of the river from Xiaolangdi to the estuary) was detected at three stages (the pre-, inter-, and post-artificial flooding season). The result showed that the microplastic concentrations in the Yellow River ranged from 0.105 to 1.17 items m−2. The main microplastic shapes found were foam and film, and the main components were expanded polystyrene and polyethylene. The average particle sizes were 1101.54, 484.93, and 509.46 μm at the three stages, respectively. The artificial flood accelerated the transport of microplastics from inland to the estuary and ocean; it also unified the overall particle size of microplastics along the river. The microplastics in the surface water of the study area likely originate mostly upstream of the Xiaolangdi Hydropower Station. The artificial flooding generated from water and sediment regulation transports a large amount of microplastics in the reservoirs and river channels to the estuary and offshore areas in a short time period via artificial flooding.

Greenland Sea Gyre increases microplastic pollution in the surface waters of the Nordic Seas

Microplastics are ubiquitous in various ocean areas and have aroused global concern. This study investigated the abundance and characteristics of microplastic pollution in the Nordic Seas. In the sea area affected by the East Greenland Current, the abundance of microplastics was 1.19 ± 0.28 items/L, with fiber (76.1%), transparent (76.2%), and small microplastics (0.1–0.5 mm, 48.1%) being the most abundant types present. The abundance of microplastics in the cold basin affected by the Greenland Sea Gyre was 2.43 ± 0.84 items/L. Fiber accounted for 87.2% of the total microplastics, and the proportions of transparent and 0.1–0.5 mm particles were 87.6% and 63.9%, respectively. Principal component analysis (PCA) based on size spectrum data revealed that the spatial pattern of microplastics was closely related to ocean currents and the station position in the ocean current. Furthermore, scanning electron microscopy (SEM)/energy dispersive spectroscopy (EDS) analysis illustrated that the microplastics had many weathering and exfoliation sites and adsorbed heavy metals onto their surfaces. The Fourier Transform Infrared Spectrometer (FTIR) analysis showed that the microplastics in the Nordic Seas were mainly polyester and polyethylene. These results not only provide the latest data on microplastic pollution in the Nordic Seas, but also give evidence that ocean currents affect the transport of marine microplastics.

A review of possible pathways of marine microplastics transport in the ocean

Marine microplastics pollution has been a new challenge to marine environmental protection. The research results have shown that microplastics exist everywhere in the ocean. However, understanding of the transport of microplastics in the ocean, including coastal zones, is not clear. This paper provides a holistic overview of the modelling of microplastic transportation. The transport processes are complex, including surface drifting, vertical mixing, beaching, and settling. Besides the dynamic conditions of oceans, the transportation of microplastics is influenced by their physical characteristics, such as size, shape, and density. For buoyant particles, a Lagrange track model is used to simulate the surface drift process, considering current, windage effect, and Stokes drift. It is difficult to observe the vertical mixing process of microplastics because of their small size (<5 mm), therefore the parameters of the vertical mixing process in the model are still less known. Large accumulation of microplastics in sediments may be a result of settlement and entrainment. Also, biofilm formation can increase their density and thus, deposition. Considering sedimentation of microplastics is somewhat different from sediment deposition, some primary parameters (e.g., diffusivity, Stokes-drift, settling rate, biofouling rate) are required in future studies to better understand the transport of marine microplastics.

A Geomorphic Framework for the Analysis of Microplastics in Riverine Sediments

The wide-spread use and persistence of plastics in the environment have placed them on the list of significant emerging pollutants. In contrast to marine environments, the analysis of plastic debris, including microplastics (particles &lt;5 mm in maximum diameter), in freshwater systems is limited, and even fewer studies have examined microplastics in riverine sediments. Nonetheless, it has become clear that microplastics are now a ubiquitous component of riverine ecosystems and their distribution is dependent on anthropogenic inputs and the physical and chemical processes that control their transport, transformation, and deposition along the drainage network. In many ways, the transport and fate of microplastics will parallel that of other particulate matter that has been extensively studied for at least the last 50 years. Here, we briefly explore the application of a geomorphic approach to the assessment of sediment-contaminated rivers to the microplastic problem, and argue that future studies can significantly benefit by incorporating the principles of this approach into their analyses.

Sea Waves Transport of Inertial Micro-Plastics: Mathematical Model and Applications

Plastic pollution in seas and oceans has recently been recognized as one of the most impacting threats for the environment, and the increasing number of scientific studies proves that this is an issue of primary concern. Being able to predict plastic paths and concentrations within the sea is therefore fundamental to properly face this challenge. In the present work, we evaluated the effects of sea waves on inertial micro-plastics dynamics. We hypothesized a stationary input number of particles in a given control volume below the sea surface, solving their trajectories and distributions under a second-order regular wave. We developed an exhaustive group of datasets, spanning the most plausible values for particles densities and diameters and wave characteristics, with a specific focus on the Mediterranean Sea. Results show how the particles inertia significantly affects the total transport of such debris by waves.

Fate and Transport of Microplastics from Water Sources

Fate and Transport of Microplastics from Water Sources

Microplastics increase the marine production of particulate forms of organic matter

Microplastics are a major environmental challenge, being ubiquitous and persistent as to represent a new component in all marine environments. As any biogenic particle, microplastics provide surfaces for microbial growth and biofilm production, which largely consists of carbohydrates and proteins. Biofilms influence microbial activity and modify particle buoyancy, and therefore control the fate of microplastics at sea. In a simulated ‘plastic ocean’, three mesocosms containing oligotrophic seawater were amended with polystyrene microbeads and compared to three control mesocosms. The evolution of organic matter, microbial communities and nutrient concentrations was monitored over 12 days. The results indicated that microplastics increased the production of organic carbon and its aggregation into gel particulates. The observed increase of gel-like organics has implications on the marine biological pump as well as the transport of microplastics in the ocean.

Microplastics in the soil environment: Occurrence, risks, interactions and fate – A review

The issue of microplastic pollution emerged from the marine environment, but the terrestrial environment is estimated to receive annually 4–23 times more plastic wastes. Microplastic pollution in the soil environment has thus begun to elicit great concern. This review summarizes the observed effects of microplastic pollution on soil ecosystems as well as sorption and transport behaviors of microplastics in such environments. Microplastic pollution has been detected in various soils including agricultural/farmland, greenhouse, home garden, coastal, industrial, and floodplain soils. Microplastics affect soil physical and chemical properties, microbial and enzyme activities, and plant growth, and also pose adverse ecotoxicological effects to soil fauna. These effects depend on the concentration, size, and shape of microplastics, as well as soil texture. Microplastics are known to sorb organic and inorganic pollutants, possibly affecting the distribution of these substances in soil. Existing evidence demonstrates the negligible effect of microplastics on bioaccumulation of contaminants in soil fauna. The horizontal and vertical transport of microplastics can be facilitated by soil fauna. Pollutants associated with microplastics may disperse further following the transport of microplastics in soil. This review also highlights perspectives for future research on microplastics in soil.

Modeling transport of microplastics in enclosed coastal waters: A case study in the Fethiye Inner Bay

In this study, transport and possible accumulation of microplastic marine litter in enclosed coastal waters are modeled numerically. The model is applied to the Fethiye Inner Bay, located in Fethiye-Göcek Specially Protected Area. In modeling studies, three dimensional coastal hydrodynamics, transport and water quality numerical model HYDROTAM-3D was used. The current climate was prepared by modeling long-term circulation patterns due to wind, wave and density stratifications. Following the hydrodynamic studies, the advection and diffusion of 3 mm size polystyrene particles by the coastal currents in the surface waters of Fethiye Inner Bay were simulated. The coastal regions where the microplastic pollution will be concentrated and transported were determined by the modeling scenarios. It has been found that microplastic accumulation is expected in the southwest and east coastal waters of the Fethiye Inner Bay. The results of the model will contribute to the databases for sustainable protection of the marine environments.

하수처리장(WWTP)내 미세플라스틱 : A Review

Microplastics (MPs) in the aquatic environment has recently been documented as an environmental threat due to their negative impact on the ecosystem. Wastewater treatment plants (WWTPs) are expected to be main recipients of microplastics entering into freshwater. Everyday, continuously, treated water containing microplastics from WWTP is discharged in large quantities. The aim of this article is providing a comprehensive knowledge to better understand characteristics of MPs in wastewater, the fate and transport of MPs during treatment process in WWTP, abundance of MPs discharged from WWTP and removal efficiency of MPs in lab scale and existing technologies at WWTPs. The concentration of microplastics varying from 0-91 MP/L (final effluent) and approximately > 32 MP/㎥ in fresh water. Microplastics can be removed in the primary, secondary and tertiary treatment with the removal efficiency were 41%-65%, 0.2%-14% ,and 0.2-14%, respectively. Treated water and sewage sludge act as direct and indirect pollutants into freshwater. The presence of microplastics in the environment has potential as a threat to the aquatic organism (ecotoxicological and ecological risk). Some studies have tried to remove microplastics in wastewater using artificial microplastic with performance with a range of 60-99%. On the other hand, it is necessary to introduce new technology and improve existing technologies in the WWTP that can be correctly used to remove microplastic from wastewater.

Accurate quantification and transport estimation of suspended atmospheric microplastics in megacities: Implications for human health

Although atmospheric microplastics have been found to be ubiquitous even on untraversed mountains and have potential impacts on human health, little information concerning their sampling methodology and transport is currently available. Until a realistic quantification of suspended atmospheric microplastics (SAMPs) is obtained, however, any potential health risk assessment for this pollutant will be open to criticism for using an ambiguous dataset. To address this knowledge gap, in May 2019 a trial experiment was performed to explore the potential relationship between sampling volume and SAMP abundance. A significant logarithmic regression between SAMP abundance and the sampling volume of filtrated air was found and the sufficient volume of filtrated air for accurate SAMP quantification was recommended. Investigation results indicated that fibrous and fragment-shaped SAMPs comprised 91% of all of the identified synthetic particles. Interestingly, for the first time, plastic microbeads were also observed in the collected air, constituting 9% of the all of the SAMPs by quantity. Spectral analysis revealed that these SAMPs consisted of polyethylene terephthalate (PET), epoxy resin (EP), polyethylene (PE), alkyd resin (ALK), rayon (RY), polypropylene (PP), polyamide (PA), and polystyrene (PS). PET, EP, PE, and ALK constituted the majority (90%) of all of the polymer types, with quantitative percentages of 51%, 19%, 12%, and 8%, respectively. Based on our numerical modeling simulation, the approximate transport flux of SAMPs during June in Shanghai was estimated, ranging from 9.94 × 104 n/(m·d) to 6.52 × 105 n/(m·d), with a mean of 3.00 ± 1.58 × 105 n/(m·d). The goal of our study was to provide an essential methodological aid for the accurate determination of SAMPs in the environment and a better understanding of terrestrial microplastic transport in megacities.

Influence of titanium dioxide nanoparticles on the transport and deposition of microplastics in quartz sand

The influence of titanium dioxide nanoparticles (nTiO2) on the transport and deposition of polystyrene microplastics (MPs) in saturated quartz sand was investigated in NaCl solutions with ionic strengths from 0.1 to 10 mM at two pH conditions (pH 5 and 7). Three different-sized polystyrene (PS) MPs (diameter of 0.2, 1, and 2 μm) were concerned in present study. We found that for all three different-sized MPs in NaCl solutions (0.1, 1 and 10 mM) at both pH 5 and 7, lower breakthrough curves and higher retained profiles of MPs with nTiO2 copresent in suspensions relative to those without nTiO2 were obtained, demonstrating that the copresence of nTiO2 in MPs suspensions decreased MPs transport and increased their deposition in quartz sand under all examined conditions. The mechanisms contributing to the increased MPs deposition with nTiO2 in suspensions at two pH conditions were different. The formation of MPs-nTiO2 heteroaggregates and additional deposition sites provided by previously deposited nTiO2 were found to drive to the increased MPs deposition with nTiO2 in suspensions at pH 5, while the formation of MPs-nTiO2 aggregates, additional deposition sites and increased surface roughness induced by the pre-deposited nTiO2 on quartz sand surfaces were responsible for the enhanced MPs deposition at pH 7. The results give insights to predict the fate and transport of different-sized MPs in porous media in the copresence of engineered nanoparticles.

Author Correction: Atmospheric transport and deposition of microplastics in a remote mountain catchment

In the version of this Article originally published, the following text was missing from the Acknowlegements: ‘CESBIO OHM Bernadouze weather station is supported by the Observatoire Spatial Regional (CNRS-INSU) and CNES-TOSCA funding was awarded to S. Gascoin. This scientific work was made possible with the logistical support of the ONF (French National Forestry Office) and the support of the inhabitants of the valley.’ In addition, ref. 17 was the wrong reference, it should have been ‘Gascoin, S. & Fanise, P. Bernadouze Meteorological Data https://doi.org/10.6096/DV/UQITZ4 (SEDOO OMP, 2018)’. The Article has now been corrected.

Technical note: On the importance of a three-dimensional approach for modelling the transport of neustic microplastics

Abstract. Understanding and estimating the distribution and transport of microplastics in marine environments has been recognized as a major global research issue. Most of the existing research on transport modelling has focused on low-density particles floating in surface waters, using a 2-D Lagrangian approach and ignoring the vertical displacement of particles. In this work, we evaluate to what extent the vertical movement of particles within surface waters by mixing processes may affect the horizontal transport and fate of microplastics. The aim is to determine whether a 2-D approach is sufficient for the accurate modelling of neustic-microplastics transport or whether a 3-D approach is necessary. For this purpose, we compare visually and statistically the microplastics transport patterns of three simulations in a coastal system: one using a 2-D approach; and two using a 3-D approach with weak and strong vertical turbulence, respectively. The 2-D simulation roughly reproduced the transport and accumulation patterns, but accurate results required a 3-D approach. This was particularly important for strong vertical turbulence and regions characterized by strong vertical current shear. Moreover, a 2-D approach can lead to errors in the results even with negligible turbulence due to simplifications in the velocity field. A 3-D modelling approach is therefore key to an accurate estimation and prediction of microplastics distribution in coastal systems and consequently for planning mitigation and cleaning programmes.

The vertical distribution and biological transport of marine microplastics across the epipelagic and mesopelagic water column

Plastic waste has been documented in nearly all types of marine environments and has been found in species spanning all levels of marine food webs. Within these marine environments, deep pelagic waters encompass the largest ecosystems on Earth. We lack a comprehensive understanding of the concentrations, cycling, and fate of plastic waste in sub-surface waters, constraining our ability to implement effective, large-scale policy and conservation strategies. We used remotely operated vehicles and engineered purpose-built samplers to collect and examine the distribution of microplastics in the Monterey Bay pelagic ecosystem at water column depths ranging from 5 to 1000 m. Laser Raman spectroscopy was used to identify microplastic particles collected from throughout the deep pelagic water column, with the highest concentrations present at depths between 200 and 600 m. Examination of two abundant particle feeders in this ecosystem, pelagic red crabs (Pleuroncodes planipes) and giant larvaceans (Bathochordaeus stygius), showed that microplastic particles readily flow from the environment into coupled water column and seafloor food webs. Our findings suggest that one of the largest and currently underappreciated reservoirs of marine microplastics may be contained within the water column and animal communities of the deep sea.

Spatiotemporal distribution and annual load of microplastics in the Nakdong River, South Korea

Although rivers represent an important pathway for the transport of microplastics to the oceans, research on riverine microplastics is limited compared to the marine environment. Hence, we investigated the spatiotemporal distribution of microplastics in the Nakdong River down to 20 μm in size and characterized them using Fourier transform infrared spectroscopy in surface and mid waters and sediment. The mean (±standard deviation) abundance of microplastic in the Nakdong River was in the range of 293 ± 83 (upstream, February 2017) to 4760 ± 5242 (downstream, August 2017) particles/m3 in water, and 1970 ± 62 particles/kg in sediment. The abundance of microplastics was about three times higher in surface than mid waters in the downstream area. Polypropylene and polyester accounted for 41.8% and 23.1% of microplastics in the water, respectively, whereas about 50% in the sediment was composed of polypropylene and polyethylene. Microplastics smaller than 300 μm in size accounted for 74% in the water and 81% in sediment, and the distribution peaked in the 50–150 μm size range. Based on these results, we estimated the annual load of microplastics carried by the Nakdong River in 2017 to be 5.4–11 trillion by number and 53.3–118 tons by weight. The proportions of the total load transported through surface water and the water column were 8% and 92%, respectively. In addition, the microplastic load was concentrated in the wet season, which makes up 71% in number and 81% in weight. These results indicate that it is necessary to reflect seasonal variation and sample both in the surface water and water column to estimate microplastic transport. Without considering these factors, the annual load of microplastics may be overestimated or underestimated.

Dispersion, Accumulation, and the Ultimate Fate of Microplastics in Deep-Marine Environments: A Review and Future Directions

An estimated 8.3 billion tonnes of non-biodegradable plastic has been produced over the last 65 years. Much of this is not recycled or disposed of ‘properly’, has a long environmental residence time and accumulates in sedimentary systems worldwide, posing a threat to important ecosystems and potentially human health. We synthesise existing knowledge of seafloor microplastic distribution, and integrate this with process-based sedimentological models of particle transport, to provide new insights, and critically, to identify future research challenges. Compilation of published data shows that microplastics pervade the global seafloor, from abyssal plains to submarine canyons and deep-sea trenches. However, few studies relate microplastic accumulation to sediment transport and deposition. Microplastics may enter directly into the sea as marine litter from shipping and fishing, or indirectly via fluvial and aeolian systems from terrestrial environments. The nature of the entry-point is critical to how terrestrially-sourced microplastics are transferred to offshore sedimentary systems. We present models for physiographic shelf connection types related to the tectono-sedimentary regime of the margin. Beyond the shelf, the principal agents for microplastic transport are: i) gravity-driven transport in sediment-laden flows; ii) settling, or conveyance through biological processes, of material that was formerly floating on the surface or suspended in the water column; iii) transport by thermohaline currents, either during settling or by reworking of deposited microplastics. We compare microplastic settling velocities to natural sediments to understand how appropriate existing sediment transport models are for explaining microplastic dispersal. Based on this analysis, and the relatively well-known behaviour or deep-marine flow types, we explore the expected distribution of microplastic particles, both in individual sedimentary event deposits and within deep-marine depositional systems. Residence time within certain deposit types and depositional environments is anticipated to be variable, which has implications for the likelihood of ingestion and incorporation into the food chain, further transport, or deeper burial. We conclude that integration of process-based sedimentological and stratigraphic knowledge with insights from modern sedimentary systems, and biological activity within them, will provide essential constraints on the transfer of microplastics to deep-marine environments, their distribution and ultimate fate, and the implications that these have for benthic ecosystems.

Atmospheric transport and deposition of microplastics in a remote mountain catchment

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 fragments ≤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.

Wind erosion as a driver for transport of light density microplastics

Microplastic pollution in the environment is a growing concern in today's world. Wind-eroded sediment, as an environmental transport pathway of microplastics, can result in environmental and human exposure far beyond its sources. For the first time, this study investigates the presence of microplastics in wind-eroded sediments from different land uses in the Fars Province, Iran. Eleven test plots were selected based on land use and wind erosion risk. On each plot, wind erosion was simulated using a portable wind tunnel and the eroded sediment was collected for further analysis aimed at measuring light density microplastics (LDMP). The LDMPs were extracted in both soil and wind-eroded sediment using a floatation method and then further examined using microscopy. Annual LDMP transport by wind erosion was estimated using wind data from the study areas. LDMPs were detected in six study areas in the Fars Province which are highly prone to wind erosion. Although LDMPs were found mostly in agricultural land, it was also detected in the soils and sediments from two natural areas. The total concentrations of LDMPs in polluted areas were 6.91 and 20.27 mg kg−1 of microplastics in soil and wind-eroded sediments, respectively. The enrichment ratio for LDMP ranged from 2.83 to 7.63 in different areas. The erosion rate of LDMP ranged from 0.08 to 1.48 mg m−2 min−1. The results of this study confirmed the key role of wind erosion in the spread of microplastics in terrestrial environments which could form an exposure risk to humans via direct inhalation of the particles transported with the dust.