The presentations will revolve around understanding and characterising plastic movement and distribution, considering governing factors like particle size, shape, density, and environmental conditions such as flow, turbulence, temperature, salinity and suspended sediment. Relevant biological and chemical processes will be taken into account such as biofouling, aggregation and fragmentation, as well as plastic's role as transport vectors for other emerging contaminants in subsurface environments, adding to their transport complexity and substantially impacts the health of subsurface environments.
Beyond the presentation of research findings, this session will also focus on advancements in laboratory and numerical techniques, highlighting improvements in accuracy, complexity, and spatial-temporal resolution. Cutting-edge modelling approaches tailored to simulate the intricate transport dynamics of plastics in the environment will be showcased.
Through engaging discussions, the session aims to enhance our comprehension and predictive capabilities, while also identifying unresolved questions and paving the way for future research endeavors in this vital area of study.
Rivers act as major pathways for microplastic pollution, yet the mechanisms governing the transfer of suspended microplastics from the water column to riverbeds remain poorly understood. We conducted controlled flume experiments under steady, unidirectional flow to quantify the deposition of microplastic fibres within a sandy ripple bed. Polyamide and polyester fibres, introduced at environmentally relevant concentrations, were tracked under clear-water conditions and in flows containing suspended kaolin to simulate enhanced fine-sediment loads. In clear water, fibres remained widely mixed throughout the water column and were only rarely incorporated into sand, indicating efficient downstream transport and limited short-term sequestration. In contrast, the presence of suspended kaolin induced pronounced and elevated near-bed fibre concentrations and substantially increased the incorporation of fibres into the sand bed. Fibre properties influenced this process: higher-density fibres exhibited greater settling tendencies, while curled fibres experienced increased drag and more frequent interactions with both saltating sand grains and suspended particles, promoting their entrapment within the bed. These results demonstrate that suspended fine sediments can markedly enhance microplastic deposition in riverbeds by altering near-bed transport dynamics and promoting physical entrapment within bedforms. Such conditions create accumulation zones that may influence the short-term accumulation and long-term distribution of microplastics in river systems.
How to cite: Uguagliati, F., Khozaya, M., Waldschläger, K., Zattin, M., and Ghinassi, M.: Suspended load effects on microplastic transfer from the water column to the riverbed, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-634, https://doi.org/10.5194/egusphere-egu26-634, 2026.
Globally, plastic pollution in aquatic environments has been considered one of the major contemporary environmental concerns. In recent years, an increasing number of studies reported environmental consequences and concentrations of plastic particles in freshwater systems. The observed abundance of plastic particles in ecosystems may be influenced by factors such as the properties of plastic, including size and shape. Plastic items can be differentiated according to their size range and therefore identified by adopting the prefixes macro (> 25 mm), meso (> 5 mm < 25 mm), and micro (< 5 mm). Once large plastics accumulate in the natural environment, they are subject to multiple weathering processes that drive fragmentation and degradation. Plastic items suspended in the water column may be exposed to the strong hydrodynamic forces generated by vessel motion, for instance, turbulent water flow created by the propellers as the vessel moves through the water. Facing that, this study experimentally quantifies the forces needed to fragment plastic items collected in the Rhine River, subsequently, it assesses the likelihood of drag forces exerted by the propeller jet of moving vessels as causes of plastic fragmentation. By examining the forces applied to different categories of plastic items, valuable insights will be gained on the mechanical fragmentation of plastics in a highly navigated river, contributing to better predictions of the spread and transport of plastic items and their risks to wildlife and humans. Among the observed categories, “Plastic film 2.5–50 cm (soft)” exhibited the lowest median force to break compared to all other categories (3.8N), being more susceptible to fragmentation under high jet-induced velocities generated by vessels, showing consistently higher breakage probabilities, exceeding 50% at velocities ≥ 5 m.s⁻¹ and reaching values up to ~80% at 10 m.s⁻¹. On the contrary, the top three categories that exhibited the highest resistance to breaking, with high median values, corresponded to “Plastic cups” (14.09N), “ Sanitary/ wet wipes” (11.24N), and “ Plastic cotton swabs” (11.08N).
How to cite: Oswald, S., van Lierop, N., and P. L. Collas, F.: Navigation-Induced Turbulence as a Driver of Plastic Fragmentation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20560, https://doi.org/10.5194/egusphere-egu26-20560, 2026.
Pore-scale microplastics (< 10 μm) are emerging contaminants whose behavior and fate in aquatic environments remain poorly understood. While the properties of spherical microplastics (SMPs) in fluvial systems have been studied, those of irregularly shaped microplastics (IMPs) and microplastic fibers (MPFs) remain poorly understood. We investigated how the transport and retention of IMPs and MPFs differ from those of SMPs. We compared the transport dynamics of 8 µm diameter IMPs and MPFs, with diameters ranging from 5 to 10 μm and lengths of 60–250 μm, with reference SMPs of diameters 1, 3, and 10 μm, by continuously monitoring microplastic concentrations in surface water and streambed sediments. Our results demonstrate how particle shape and sediment-particle ratio affect the transport and retention of microplastics in fluvial systems. These differences will have significant implications for the ecological impact and long-term fate of different MPs, including the duration of exposure to benthic organisms and the burial of MPs in deeper sediment layers due to river sedimentation cycles.
How to cite: La Capra, M., Wagner, D., Agarwal, S., Fleckenstein, J. H., and Frei, S.: An experimental flume study on the retention of Microplastic Fibers and Irregular Microplastics, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-11261, https://doi.org/10.5194/egusphere-egu26-11261, 2026.
The “missing plastic” paradox highlights a critical gap in our understanding of plastic transport in the ocean. A leading hypothesis suggests a significant fraction is vertically distributed within the water column, modulated, among other effects, by biofouling—the colonization of plastic by algae. To investigate this process, we used a biofouling model by Kooi et al. (2017). Our study systematically investigated a wide range of polymer densities representative of the most prevalent plastics found in the marine environment while combining a parametric analysis of the biofouling process to clarify how plastic properties govern biofilm development and subsequent particle dynamics.
The model reveals that biofouling induces complex, oscillatory vertical migrations. Particles experience rapid biofilm growth, increasing their density and sinking. As they descend into colder waters, growth is suppressed, and metabolic losses reduce the biofilm, causing the particles to regain buoyancy and return to the surface to restart the cycle. Our analysis further demonstrates that particle size and density are critical drivers: smaller particles support a larger biofilm relative to their size, while density significantly influences the timescale of sinking onset for larger particles. Long riverine plastic emissions in the eastern Atlantic Ocean were tracked to study the accumulation areas in the ocean as a function of seasonal biofouling patterns and local currents patterns.
These results underscore that accurately modeling biofouling is essential for predicting the fate and distribution of marine plastic pollution in the ocean, moving beyond the simplistic assumption of particles as passive Lagrangian tracers.
How to cite: Rial-Osorio, M., Pérez-Muñuzuri, V., and Cloux, S.: From Surface to Sink: How Plastic Characteristics Dictate Biofilm Formation and Fate. , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5166, https://doi.org/10.5194/egusphere-egu26-5166, 2026.
The prediction of plastic particles’ spatial distribution and their fate in water environments depends on a range of particle properties and environmental factors. Salinity-stratified water columns, commonly found in estuaries, have a major influence on the transport behaviour and the settling velocity of these particles. Water density gradients with depth modify the buoyancy force acting on plastic particles, leading to non-uniform vertical velocity and heterogeneous distribution throughout the water column. On the other hand, intrinsic particle properties, such as polymer density, size and shape, also play an important role, affecting their behaviour within the same environment. In this study, the effects of salinity gradients in settling velocity of plastic particles of different shapes, sizes and polymers are investigated through several experiments carried out in the Laboratory of Hydraulics at the University of Coimbra. To perform the experiments, granular particles of four different types of polymers (PMMA, PS, PVC and PET) were used, with particle densities ranging from 1.047 g/cm3 to 1.372 g/cm3. The experiments were conducted in a transparent acrylic tank with dimensions of 32 cm (width) x 32 cm (length) x 100 cm (height). The tank was filled with water at different salt concentrations, which were previously measured using a conductivity sensor. By means of an auxiliary valve located at mid-height of the tank, it was possible to introduce water with different salinities, producing different stratification profiles. The particles were then carefully released 5 cm below the water surface. Following the particles’ release, images were recorded using high resolution cameras, placed in front of the tank. The acquired images were treated and post-processed using a Particle Tracking Velocimetry (PTV) method to determine the settling velocity of the plastic particles. Based on the experiments carried out, this study highlights the importance of accounting for salinity effects when determining the settling velocity of plastic particles, as higher salinity concentrations lead to reduced settling velocities. As expected, the study demonstrates that higher salinity gradients promote a decrease in the settling velocity of the particles along the water column. This effect is particularly clear in the experiments where the halocline is more evident. In addition, the particles’ density and shape also prove to be important factors, directly influencing the settling velocity.
How to cite: Romero, A. and F. Carvalho, R.: Settling Velocity of plastic particles in Salinity-Stratified Water Columns: An Experimental Investigation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3826, https://doi.org/10.5194/egusphere-egu26-3826, 2026.
Floodplains are recognized as significant sinks for sediments and pollutants transported by rivers, particularly during flood events which mobilize and redistribute contaminants like microplastics (MPs). This study investigates the role of floodplain vegetation and rough surfaces in the retention of microplastics and fine sediments during overbank flow, and the subsequent fate of these particles within the soil profile.
The research combined column experiments and field observations to quantify particle deposition. We found that vegetation characteristics are a primary driver for the retention of suspended particles. Specifically, plant biomass and structural diversity were positively correlated with the amount of sediment deposited on the vegetation surface. This suggests that denser and more structurally complex vegetation enhances the capture of both sediments and microplastics from the water column. To differentiate the effects of biological surfaces from purely physical ones, deposition on vegetation was compared with deposition on metal sheets of varying surface areas. The deposition results potentially reveal the impact of surface areas and roughness on microplastic retention.
Following the initial retention process, microplastics can infiltrate into the floodplain soil. The analysis of flood simulated soil column experiments confirm a heterogenous and rapid microplastic breakthrough. Additionally, under field conditions soil profiles confirms that floodplains act as major sinks, with the highest concentrations of MPs found in the upper 38-45 cm of soil depth. However, MPs are not permanently sequestered at the surface. The vertical distribution of microplastics is influenced by particle characteristics such as size and shape and soil properties. Smaller, spherical particles tend to infiltrate deeper into the soil compared to larger fragments and fibers. This downward translocation can be facilitated by processes such as preferential flow through soil structure and biopores.
In conclusion, floodplain vegetation plays a critical role in intercepting microplastics during floods, initiating their transfer from the aquatic to the terrestrial environment. The retention efficiency is closely linked to vegetation biomass and structure. Our findings highlight that vegetation structure is one factor for MP sedimentation from flooding, while soil structure and biopores control infiltration and vertical transport of MP into the soil matrix. Subsequent infiltration and distribution in the soil profile are governed by a complex interplay between MP particle traits, soil texture, and biological activity. These findings highlight the importance of floodings, vegetation cover, soil structure in the transport of microplastics at the interface of aquatic and terrestrial ecosystems.
How to cite: Rolf, M., Laermanns, H., Echstenkämper, L., Seidel, P., Gröbner, M., Riedesel, S., Khaleel, R., Dowe, M. W., Holler, L., Pohl, F., Feldhaar, H., Laforsch, C., Löder, M. G. J., and Bogner, C.: Microplastic retention during a flood event by floodplain vegetation and their infiltration into the Rhine floodplain soil , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20390, https://doi.org/10.5194/egusphere-egu26-20390, 2026.
The widespread use of plastics since the mid-twentieth century has led to their pervasive accumulation in the environment. As plastics progressively weather and fragment, they generate secondary nanoplastics, which constitute the dominant form of nanoplastics in the environment. Despite their relevance, secondary nanoplastics remain largely understudied due to analytical challenges associated with low concentrations, complex matrices, and the diversity of polymers. Consequently, much of the current literature relies on microplastics or model primary nanoplastics that do not adequately represent environmentally formed secondary nanoplastics.
In this work, we introduce a novel analytical method for quantifying secondary nanoplastics in aqueous solutions and leverage these capabilities to study the transport of four distinct, environmentally relevant plastics (PET, PP, LDPE, and HDPE) and landfill-derived nanoplastics that were weathered naturally for more than 20 years (and thus represent real environmental secondary nanoplastics). We then focus on analysis of the mobility of these secondary nanoplastics through sand and soil columns, examining breakthrough curves and size distributions to elucidate the leading transport mechanism(s) of these particles. Our results show a plastic-specific transport that is influenced by plastic chemistry and the type of porous medium. Aliphatic plastics tend to be retained more than aromatic ones, due to higher hydrophobicity. Size distribution analysis indicates that eluted secondary nanoplastics are generally larger, suggesting that smaller particles aggregate or are retained within the media. Despite chemical similarity, secondary HDPE and secondary LDPE differ in their elution patterns, while secondary PET exhibits increased aggregation due to its extended π-orbital system. Landfill-derived nanoplastics showed greater retention owing to inorganic impurities, which promote smaller aggregation. Additional experiments examining secondary HDPE transport across multiple porous media, including three sand grain sizes and a sandy loam soil, showed generally consistent retention behavior, with the notable exception of fine sand. In fine sand, enhanced retention is likely driven by smaller pore throats that promote particle trapping. Size-resolved elution patterns revealed two distinct particle populations in fine sand, whereas medium and coarse sands, as well as soil, exhibited a shift toward larger eluted particles. In soil, a modest delay in secondary HDPE breakthrough further suggests interactions between secondary HDPE and the soil matrix.
Overall, our findings provide new mechanistic insights into secondary nanoplastic transport and represent a significant step toward a realistic assessment of nanoplastic fate in subsurface environments.
How to cite: Vershinin, P., Dror, I., and Berkowitz, B.: Secondary nanoplastic transport in sand and in soil, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2405, https://doi.org/10.5194/egusphere-egu26-2405, 2026.
Microplastics (MPs) have emerged as widespread and persistent contaminants in fluvial environments. Their transport pathways and retention mechanisms within riverbeds have recently attracted increasing attention. Although stochastic models and experimental studies have shown that streambed sediments can act as important sinks of MPs particles, the hydrodynamic drivers and particle-sediment interactions governing particle exchange across water-sediment interfaces remain insufficiently understood, particularly under complex streambed geometries and variable flows.
In this study, a novel three-dimensional Eulerian-Lagrangian model (MultiFlow3D) is used to investigate MPs transport at surface water-sediment interfaces, resolving turbulence and particle motion in both the free-flow region and the permeable streambed sediments. MPs are simulated as Lagrangian particles, while the streambed sediment is represented through a smooth transition volume penalization numerical treatment that represents the porous bed as spheres. In addition, particle-particle and particle-porous media collision is incorporated to enhance the physical realism of particle interactions.
The model is validated through the reproduction of published laboratory experiments, in which the hydrodynamic flow field and particle transport processes are validated separately. The hydrodynamic component is validated by comparing simulated velocity fields and pressure distributions with experimental measurements, while the particles interactions are validated by reproducing observed particle trajectories, infiltration locations, and retention.
Based on the validation, the influence of different riverbed geometries on the migration of MPs is investigated by testing both sinusoidal and uniform beds. The results indicate that, in most cases, high-pressure regions only develop on the upstream face of bedforms, causing MPs particles to predominantly infiltrate the sediment from the stoss side. However, a secondary high-pressure region may also form under certain conditions on the downstream side, allowing particles to enter the sediment from the lee side. Once infiltrated, most MPs particles remain confined to shallow subsurface layers, with limited penetration depth into the sediment bed.
This study provides mechanistic insight into the combined effects of hydrodynamic pressure distributions and bedform geometry on MPs transport across the water-sediment interface. The proposed modelling approach offers an efficient and physically consistent tool for investigating the environmental fate of MPs in permeable riverbeds and supports improved interpretation of experimental observations.
How to cite: Chen, Z., Alqrinawi, F., Fraga, B., and Krause, S.: A novel Eulerian-Lagrangian numerical framework to investigate microplastic transport at surface water-sediment interfaces., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8104, https://doi.org/10.5194/egusphere-egu26-8104, 2026.
Metallic additives are extensively incorporated into plastics materials to improve their functional properties. Although the use of hazardous substances is now largely restricted in the EU, numerous metal(oid)s, such as lead, cobalt and hexavalent chromium (Cr(VI)), were historically used in plastic formulation1,2. Yet, as these legacy plastics undergo environmental degradation, the fate of the metal(oid)s they contain remains poorly understood.
Chromium speciation in plastics debris collected from beaches in Guadeloupe (France) was first investigated using micro- X-ray absorption spectroscopy (micro-XAS) combined with micro-X-ray fluorescence (micro-XRF). Chromium was found predominantly as Cr(III) within cobalt chromite (CoCr2O4), but also as toxic Cr(VI) in crocoite (PbCrO4) or potassium chromate (K2CrO4)3. Mineral phases occur as micro- and nanoscale particulate additives embedded within the polymer matrix.
To assess the behavior of such chromium additives during plastic degradation, representative PP fragments, containing high chromium concentrations, were altered in environmentally relevant conditions, following Blancho et al.4. Micro-XAS analyses combined with micro- and nano-XRF imaging reveal that crocoite micro- and nanoparticles dominate chromium speciation in both macro- and microplastics. However, chromium contents and speciation are drastically modified in nanoplastics. A ~95% reduction in total chromium concentration is observed. Remaining chromium occurs as Cr(III) diffused within the polymer matrix.
Micro and nano-tomography imaging, in addition to SEM observations, were conducted to track the processes leading to the fragmentation and the release of toxic additives such as crocoite. In the plastic, before UV-C exposure, particulate additives are embedded in the polymer matrix, with air pockets around them. These additives are separated by more than 100 nanometers. UV-C irradiation induces the development of fracture networks from the plastics surface to subsurface, which connect the additive pockets to each other.
Altogether, this study combining laboratory and field experiments demonstrates a new model for the release of metallic additives during plastic alteration. UV-C exposure creates a network of fractures that compromises the polymer integrity by interconnecting the pockets of additives particles. Subsequent mechanical erosion promotes polymer fragmentation. This two-step process results in the liberation of nanoplastics that are free from metallic particulate additives, which are released on their own. This model is crucial to understand the mechanisms governing the environmental release of toxic metal(oid)s during plastic alteration.
References
1 Bridson et al., (2021), Journal of Hazardous Materials, 414, 125571.
2 Turner and Filella, (2021), Environment International, 156, 106622.
3 Catrouillet et al., (2021), Environ. Sci.: Processes Impacts, 23, 553–558.
4 Blancho et al., (2021) Environ. Sci.: Nano, 8, 3211–3219.
How to cite: Pécheul, G., Bollaert, Q., Vantelon, D., Laville, M., Catrouillet, C., Funes Hernando, D., Pattier, M., Rivard, C., Medjoubi, K., Perrin, J., Bihannic, I., and Davranche, M.: Legacy Plastics Release Toxic Metal(oid)s During Environmental Degradation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14887, https://doi.org/10.5194/egusphere-egu26-14887, 2026.
Plastic litter in aquatic systems is widely acknowledged as a major environmental concern, yet quantitative information on the physical characteristics of individual litter items - such as their mass, size, and shape - is still scarce. Riverine litter monitoring commonly relies on the River-OSPAR (Oslo–Paris Convention) classification scheme, which defines 109 standardized categories to support harmonized observations and policy development. While this framework offers clear advantages for categorization, it generally reports only item types (e.g. plastic bags) and lacks statistical descriptions of their physical properties. Such quantitative information is essential for multiple applications, including the design of laboratory experiments, the parameterization of numerical models describing litter transport and fate, the optimization of field sampling strategies, and the development of effective clean-up technologies such as racks or retention devices.
Here, we present a meta-analysis of 13 published studies covering 11 rivers on four continents, comprising a total of 240,571 litter items classified using the River-OSPAR index. We use detailed measurements of the longest and intermediate axes (L₁ and L₂) and mass (M) reported for 14,052 items by De Lange (2023), to derive joint probability distributions for these variables for each River-OSPAR category using copula-based statistical methods. These category-specific distributions are combined with observed category frequencies to construct a large synthetic dataset representing global riverine litter characteristics. By introducing assumptions on litter volume and density distributions, we further estimate the smallest axis (L₃), enabling a complete geometric description of individual litter items.
We identify the 25 most persistent litter categories (out of 109) in riverine environments, and we discuss full statistical distributions of L₁, L₂, and L₃, along with derived parameters commonly used in sediment and particle transport modelling, including volume, elongation (L₂/L₁), and flatness (L₃/L₂). All derived distributions are made openly available to support future experimental studies, numerical simulations, and improved monitoring and mitigation strategies for plastic pollution in rivers. This database is the basis for experimental investigation over these 25 most persistent litter categories which we developed at the moment and will be further presented and discussed.
We found that the marginal distribution of flatness peaks at 0.05, whereas the marginal distribution of elongation appears approximately uniform. When considering the joint probability distribution, nearly half of the macrolitter found in riverine environments has longest and intermediate dimensions between 1 and 10 cm and is very flat. Moreover, the ratio of the intermediate to the longest axis can take any value between 0 and 1.
How to cite: Rebai, D., Lofty, J., Franca, M. J., and Valero, D.: Geometric and physical properties of the most persistent litter items in rivers, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17862, https://doi.org/10.5194/egusphere-egu26-17862, 2026.
Understanding the dynamics of unintentional microplastic (MP) ingestion by benthos in aquatic environments is crucial for assessing the ecological impacts of MPs. Yet, this process remains poorly understood. To address this, we developed a high-fidelity, two-way coupled numerical model that integrates large-eddy simulation and Lagrangian point-particle tracking techniques. Three key parameters are examined: benthos predation types (filter-feeders, grazers, and burrowers), MP density, and benthos density, with benthos density emerging as the dominant factor. Specifically, an eightfold increase in benthos density results in a 5- to 22-fold rise in ingested MPs. Benthos types influence the final ingestion proportion (defined as the ratio of ingested to released MPs), with grazers showing the highest ingestion efficiency, followed closely by filter feeders—both approximately doubling the ingestion rate observed in burrowers at equivalent benthos density. MP density has minimal inf luence on ingestion across all benthic groups and densities, except under high-density filter-feeder conditions. Two distinct MP transport models during ingestion are identified: (i) a suspension mode observed in filter-feeders and (ii) a sliding mode prevalent in grazers and burrowers. The Rouse number (P) effectively differentiates these models, with the suspension mode dominating when P < 2.5 and the sliding mode dominating when P > 2.5. The Rouse number and spanwise turbulence intensity govern the number of MPs ingested by each benthic individual, while the cumulative predation width of all benthos accounts for the impact of benthos density and types. Consequently, the product of these two parameters serves as a robust predictor for the final MP ingestion proportion, where a strong linear relationship is observed across all simulations.
How to cite: Jiao, M.: Modeling microplastic transport in open channel flows and ingestion dynamics by benthos, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5168, https://doi.org/10.5194/egusphere-egu26-5168, 2026.
The extensive use of plastics has led to a widespread presence of microplastics (MPs) across various environmental compartments. Rivers and their floodplains not only play a crucial role in transporting these particles from terrestrial sources to lakes and oceans, but can also act as temporary sinks. Despite the significance of rivers as transport pathways for MPs to the ocean, our understanding of the dominant transport and retention process in river corridors is still limited. This study investigates the transport, deposition and remobilization processes of MP along a 3.5km reach of the river Rhine between Cologne and Düsseldorf, Germany.
A three-dimensional hydrodynamic model with the morphological module (D-Morphology) was developed using the Delft3D FM software. Two types of microplastic particles with diameter of 0.1mm and different densities, 1030 kg/m3 Polystyrene and 1195 kg/m3 Polyvinyl Chloride (PVC) were used to assess their transport behavior under different flow scenarios. The model was calibrated against observed water levels on Manning’s roughness coefficient and subsequently validated against an independent data set. A continuous flux of microplastics at a concentration of 1μg/m³ was introduced into the hydrodynamic model at the upstream boundary.
First, results indicate that advection and flow turbulence are the dominant processes governing microplastic transport. Higher discharge rates enhance microplastic transport by increasing suspended concentrations, while reducing the mass of the sedimented particles. The percentage of sedimented Polystyrene was found to be about 2.5% of total input at the end of a simulated flood event in 2021. Resuspension was found to be about 40% of the sedimented mass along the river banks and floodplain during peak flood. During the recession limb of the flood event, sedimented microplastic load increased gradually whereas suspended load decreased. Additionally, the density and size of the microplastic particles along with hydrodynamic conditions significantly influence their spatial distribution and storage within the river corridor.
How to cite: Rimi, S. S., Schmidt, C., and Fleckenstein, J. H.: Simulating the fate and transport of microplastics in a river corridor (Rhine River), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9992, https://doi.org/10.5194/egusphere-egu26-9992, 2026.
Cyclonic eddies are ubiquitous in the upper ocean, linking large-scale balanced dynamics and smaller-scale unbalanced turbulence. While their role in enhancing primary productivity through nutrient upwelling is well-documented, their impact on the transport and accumulation of anthropogenic pollutants remains poorly understood. Using high-resolution data collected across a submesoscale cyclone in the Western Mediterranean Sea, we reveal that such eddies are fundamentally important in shaping the distribution of man-made contaminants. Our results show a substantial subsurface accumulation of textile microfibers within the cyclone (0.34 MF l⁻¹) compared to surrounding waters (0.09 MF l⁻¹), with this accumulation persisting even after eddysplitting. Concurrently, nutrient upwelling within the cyclone drives a marked increase in chlorophyll-a concentrations in the upper 40 m (0.44 and 0.15 mg m-3 inside and outside, respectively), indicating a coupling between physical and biogeochemical processes. We discuss potential mechanisms, including vertical circulation and mixing dynamics, that may explain the observed patterns. This study highlights the importance of submesoscale processes in shaping the distribution of anthropogenic pollutants, with significant implications for marine ecosystem healthand survey designs.
How to cite: Suaria, G., Testa, G., Paluselli, A., La Ragione, S., Gambale, M., Berta, M., A Rivera, L., Mahadevan, A., Middleton, L., Falcieri, F. M., Aliani, S., and Griffa, A.: Submesoscale cyclone in the Mediterranean Sea concentrates anthropogenic microfibers, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21911, https://doi.org/10.5194/egusphere-egu26-21911, 2026.
Plastics have emerged as a pervasive pollutant in terrestrial ecosystems, posing significant ecological risks and potential threats to human health. The pervasive nature of these plastics and their longevity leave a legacy of micro/nano-plastics (MnPs), which contaminate soil systems and drinking water resources. In recent years, a growing number of experimental studies have investigated the transport behavior of MnPs; however, comprehensive review articles focusing specifically on MnPs transport in soil- and groundwater-based column systems remain limited. The present article aims to systematically compile the existing literature on the migration and mass distribution of MnPs of varying sizes in soil, under the influence of key physicochemical parameters such as pH, ionic strength, surfactants, and solution chemistry. In addition, this review examines the effects of co-contaminants, flow direction, hydraulic forcing, and experimental setup variations on the transport and retention of MnPs within soil columns. The outcomes of the reviewed studies are evaluated through their impacts on breakthrough curves and retention profiles, providing insights into MnPs mobility and accumulation mechanisms. Both labelled and non-labelled MnPs transport studies conducted in column experiments are considered, with particular emphasis on the detection and quantification techniques employed. These include fluorescence-based methods, particle counting approaches (manual and automated), electron microscopy (SEM/TEM), and light scattering techniques such as dynamic light scattering. Finally, the performance of these detection methods is critically compared in terms of sensitivity, accuracy, and applicability, and key methodological limitations and future research challenges in MnPs transport studies are discussed.
How to cite: Anjali, A., Chauhan, N., Singh, J., Schneidewind, U., Dehbandi, R., and Krause, S.: Investigating the Migration and Transport of Micro/Nano-plastics in Soil Columns: A Systematic Review, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5723, https://doi.org/10.5194/egusphere-egu26-5723, 2026.
Microplastic particles (MPs) are ubiquitous contaminants in fluvial systems, yet the processes governing their transport and retention in surface water–groundwater systems remain insufficiently understood. This study emphasizes the combined role of removal along subsurface flow paths from rivers to groundwater, and of lateral river hydrodynamics, in shaping the distribution of MPs in riverbeds.
The spatial distribution of MPs in surface waters, sediment cores, and adjacent groundwater was investigated at two bank filtration sites in north-eastern Germany. The investigations, which took place between October 2022 and March 2024, demonstrate that the accumulation or mobilization of different polymers in riverbed sediments is controlled by a combination of hydrological exchange processes and in-channel hydrodynamics. For instance, ship-induced currents can resuspend particles, thereby preventing their deposition in navigation canals and enhancing their accumulation in riverbanks. While PP and PE dominated surface waters, negatively buoyant polymers such as PET and PVC were enriched in riverbeds and groundwater. PA, although present in surface and groundwater samples, was absent from riverbed sediments, suggesting high subsurface mobility.
This work identifies critical mechanisms controlling the fate of MPs in fluvial systems. It demonstrates that the interface between surface water and groundwater can act as a sink or a conduit, depending on the polymer type. The implications of this phenomenon are significant for the protection of drinking water and the health of freshwater ecosystems, as retention hotspots and transport pathways influence the exposure risk to biota and water resources.
How to cite: Munz, M., Loui, C., Pittroff, M., and Oswald, S. E.: Polymer-specific transfer and retention of microplastics at the river–sediment–groundwater interface, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18241, https://doi.org/10.5194/egusphere-egu26-18241, 2026.
This study examines the transport and retention of carboxylated and amine-modified polystyrene nanoparticles (NP) in quartz-, kaolinite-, and goethite-coated sands under saturated flow. Column experiments at varying flow velocities (1- 50 m d⁻¹), supported by adsorption kinetics, (X)-DLVO modeling, hydrodynamic torque analysis, and advection-dispersion modeling (ADE), were used to identify controlling factors of NP mobility.
Increasing flow velocity enhanced NP breakthrough and shifted deposition zones further along the column length, indicating a transition from diffusion- to reaction-limited attachment. Deposition followed the order goethite > kaolinite > quartz. Despite similar surface charge, carboxylated polystyrene NP showed unexpectedly strong retention on kaolinite, attributed to hydrogen bonding between carboxyl and kaolinite hydroxyl groups, as indicated by IR spectroscopy, an interaction not captured by DLVO theory. Force tensiometry showed variations in contact angles between various mineral coatings, yet no evidence for earlier proposed “long range” hydrophobic forces between NP and macroscopic surfaces could be found from Peak Force QNM measurements. ADE simulations incorporating reversible attachment-detachment and site blocking best reproduced observations, highlighting the combined roles of hydrodynamics and mineral surface chemistry. The modelling exercise further suggests that the low density of polymeric nanoparticles limits gravitational settling, challenging the transferability of trends established for denser mineral engineered nanoparticles (ENPs) such as silica.
Overall, the results demonstrate greater NP mobility and more dynamic retention in natural, heterogeneous flow systems than inferred from DLVO interactions, as supported by experiments and kinetic ADE modeling.
How to cite: Müller, S., Haberschek, T., Kasztelan, M., and Hammer, E.: Enhanced mobility and dynamic retention of nanoplastics in mineral coated porous media., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17227, https://doi.org/10.5194/egusphere-egu26-17227, 2026.
Tyre wear particles (TWP), a substantial fraction of microplastics (MPs), have drawn a lot of attention recently because of their pervasiveness in aquatic environments; nevertheless, little is known about the transport behaviour through porous media. Therefore, in this study, column experiments were carried out to investigate the transport behaviour of TWP through porous media with varied sediment grain sizes and particle density. Soda lime glass beads of 10mm and 2mm diameters were used as a porous media material to represent natural sediments, such as fine gravel and coarse sand. Transport of TWPs (1.15 g/cm³) is compared with polypropylene (PP, 0.98 g/cm3) to ascertain the impact of density on MPs transport in porous media. The results show that PP, which is of lower density, was more mobile within the fine gravel media. Despite the buoyant nature of PP and expected less gravitational settling, their movement through porous media was faster and more complete than TWP. In contrast, for the denser TWP, retention in the porous media was higher, perhaps also due to greater surface interaction with the media. However, within the coarse sand, both PP and TWP breakthrough was reduced, with lower peaks and enhanced particle retention in sediments. In this case, mechanical straining and greater surface contact likely dominated over density effects, causing increased retention for both particle types.
This suggests that both particle density and sediment grain size as well as slight differences in surface properties and shapes of TWP and PP have a considerable impact on MP transport in porous media. This research is essential for comprehending the transport dynamics of TWPs in sub-surface environments, hence emphasising the environmental repercussions linked to their extensive distribution.
Keywords: Tyre wear particle, density, glass beads, transport, PP
How to cite: Yadav, S., Yadav, B. K., Krause, S., and Schneidewind, U.: Transport of Tyre Wear Particles through Porous Media: Effect of Particle Density and Sediment Grain Size, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8308, https://doi.org/10.5194/egusphere-egu26-8308, 2026.
The ubiquitous presence of microplastics (MPs) in aquatic environments has become a major threat to ecosystems. In marine and freshwater environments, MPs interact with microorganisms, leading to the formation of biofilms on their surface and creating a complex community called the Plastisphere. This process can alter the particles’ physical and chemical properties and, in turn, affect their ecological risks, environmental transport, and fate. Our understanding of the influence of microbial colonisation on the transport of MPs in aquatic environments remains limited, warranting further research on microbe-MP interactions. The BIOPHYLM project aims to address these knowledge gaps by focusing on a less-investigated, yet significant, plastisphere aspect, which is the lower end of the MP size range, between 1-100 μm. For this purpose, MP particles will be exposed to river water (Donaukanal, Vienna) in a lab-based mesocosm setup and biophysical, colloidal, and high-throughput sequencing approaches will be applied for studying microbe-plastic interactions over time. Notably, the project aims to demonstrate real-time measurements of biofilm growth and MP particle mobility by monitoring the mesocosms with in-line digital holographic microscopy, a novel technology recently developed by BOKU researchers. By linking data from each technique, BIOPHYLM aspires to obtain a holistic view of MP-microbe interactions and fill important knowledge gaps that will improve our understanding of the role of biofilm on MP transport, and thus, reinforce a science-based risk assessment of plastic particles in the aquatic environment.
In this presentation, key elements of the project will be introduced and preliminary findings and results from its first year will be demonstrated.
How to cite: Koutsoumpeli, E., van Oostrum, P., Subbiahdoss, G., and Reimhult, E.: BIOPHYLM: Biofilm on microplastics - a biophysical perspective, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2966, https://doi.org/10.5194/egusphere-egu26-2966, 2026.
The evidence of microplastics (MPs) in groundwater is still restricted to a few sites worldwide, mostly concentrated in China, South Korea, India, a few European countries, and the USA. Even when field data are presented, they are rarely combined with auxiliary data such as hydrogeological characterisation of the area, description of the well profiles and construction materials, screen location, water geochemistry, isotopic data, and other contaminants of emerging concern. Because MP pollution is virtually ubiquitous, analysing MPs data by itself can reveal scant information on its possible sources and pathways in the subsurface. This study focuses on the Massaciuccoli Lake Basin (Central Italy), a Ramsar-designated marshy coastal wetland characterised by long-term anthropogenic influence. Over the past century, extensive land reclamation, agricultural intensification, and canalization have altered the natural hydrological regime. Documented land subsidence of approximately 2–3 m over the last 70 years has further modified groundwater gradients and surface–subsurface interactions. The initial step includes building a robust hydrogeological conceptual model of the area, combining landuse, geological background information, stratigraphic profiles, groundwater analysis of major ions and trace elements, water stable isotopes, and contaminants of emerging concern. Secondly, we combine the conceptual model with MP data from five sampling points over two sampling campaigns to help identify MPs sources and pathways in the subsurface environment. Geologically, the area is characterised as a heterogeneous sequence of marine, transitional, and continental sediments. Stratigraphic logs available for four of the five piezometers indicate an alternation of sand, silt, clay, and peat layers. This stratification promotes both vertical segregation, where low-permeability clay and peat layers restrict downward transport, and lateral compartmentalization, where permeable sandy units act as preferential flow paths. Hydrogeologically, the system is characterized as a shallow unconfined alluvial aquifer with a strong meteoric contribution and direct hydraulic connection to surface waters. Electrical conductivity, major ion chemistry, and the contaminants of emerging concern occurrence patterns indicate that groundwater composition is distinct for each piezometer, suggesting limited lateral mixing and emphasizing localized flow systems. Despite this spatial variability, hydrochemical parameters show only minor temporal variation between sampling campaigns, indicating hydrological stability at the seasonal scale. The combination of stratigraphic heterogeneity and stable flow conditions suggests that MPs detected at individual piezometers are more likely to reflect local sources and short-range transport, rather than basin-scale homogenization. Consequently, MPs are expected to exhibit site-specific distributions, with transport dominated by near-surface flow paths and attenuation occurring through physical retention at lithological boundaries.
How to cite: Zambelli Azevedo, B., Krause, S., and Re, V.: Can groundwater geochemistry and contaminants of emerging concern help elucidating microplastic sources and possible transport pathways? , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20053, https://doi.org/10.5194/egusphere-egu26-20053, 2026.
The widespread presence of microplastics (MP) is posing a potential threat to soils and groundwater. However, the mechanisms governing MP transport and retention within porous media and groundwater remain largely unknown. In this study, we provide new evidence for the complex mechanisms governing the transport of different types of MPs within porous media.
Using saturated quartz sand column models, we investigated the transport of five different MP polymer types, including Polyethylene (PE), Polyamide (PA), Polypropylene (PP), Polymethyl methacrylate (PMMA), and Polyethylene terephthalate (PET) at particle concentrations of 5,000; 50,000; and 500,000. MP Breakthrough curves and retention profiles were obtained to determine the polymer type and concentration specific transport and retention rates. Results indicate that MP transport capacity in porous media does not always exhibit linear correlation with MP particle concentrations. Specifically, as the particle injection concentration increased, the transport capacity of PE and PP initially increased and then decreased, reaching a maximum at 50,000. In contrast, the transport capacity of PET and PMMA increased markedly as the injection concentration rose from 5,000 to 50,000, but showed no further significant change when the concentration was increased from 50,000 to 500,000. In addition, biofilm growth on MP particles was found to alter the physicochemical properties of the MP particle surface, thereby modifying particle-matrix interactions and particle retention, and changing the overall MP transport behavior through porous media.
These findings indicate that concentration impacts on particle transport behavior must be fully accounted for when applying column experiments to investigate particle transport, highlighting the importance of determining and applying environmentally realistic MP concentration ranges and particle conditions for testing. Furthermore, biofilm attachment to MP surfaces can alter critical surface properties and particle-matrix interactions, thereby modifying transport rates within subsurface environments.
How to cite: Li, K., Comer-warner, S., Alqrinawi, F., Lynch, I., and Krause, S.: The Effect of Polymer Type and Particle Concentration on Microplastic Transport Mechanisms in Saturated Porous Media, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7634, https://doi.org/10.5194/egusphere-egu26-7634, 2026.
