HS2.3.5 | Large-scale plastic transport and accumulation processes in freshwater systems
Large-scale plastic transport and accumulation processes in freshwater systems
Convener: Louise SchreyersECSECS | Co-conveners: Daniel González-Fernández, Marcel Liedermann, Freija MendrikECSECS, Paul VriendECSECS
| Wed, 17 Apr, 14:00–15:45 (CEST)
Room 2.15
Posters on site
| Attendance Thu, 18 Apr, 10:45–12:30 (CEST) | Display Thu, 18 Apr, 08:30–12:30
Hall A
Posters virtual
| Attendance Thu, 18 Apr, 14:00–15:45 (CEST) | Display Thu, 18 Apr, 08:30–18:00
vHall A
Orals |
Wed, 14:00
Thu, 10:45
Thu, 14:00
Plastic pollution in freshwater systems is a widely recognized global problem with potential environmental risks to water quality, biota and livelihoods. Furthermore, freshwater plastic pollution is also considered the dominant source of plastic input to the oceans. Despite this, research on plastic pollution has only recently expanded from the marine environment to freshwater systems. Therefore data and knowledge from field studies are still limited in regard to freshwater environments. Sources, quantities, distribution across environmental matrices and ecosystem compartments, and transport mechanisms remain mostly unknown at catchment scale. These knowledge gaps must be addressed to understand the dispersal and eventual fate of plastics in the environment, enabling a better assessment of potential risks as well as development of effective mitigation measures.

This session welcomes contributions from field, laboratory and modelling studies that aim to advance our understanding of river network and catchment-scale plastic transport and accumulation processes. We are soliciting studies dedicated to all plastic sizes (macro, micro, nano) and across all geographic settings. We are especially encouraging studies that can link plastic accumulation and transport to catchment-wide hydrological, ecological or geomorphological processes that we can better understand where, when and why plastics accumulation takes place in aquatic-terrestrial environments.

In this session, we explore the current state of knowledge and activities on macro-, micro- and nanoplastics in freshwater systems, focusing on aspects such as:

• Transport processes of plastics at catchment scale;
• Source to sink investigations, considering quantities and distribution across environmental matrices (water and sediment) and compartments (water surface layer, water column, ice, riverbed, and riverbanks);
• Plastic in rivers, lakes, urban water systems, floodplains, estuaries, freshwater biota;
• Effects of hydrological extremes, e.g. accumulation of plastics during droughts, and short-term export during floods in the catchment;
• Modelling approaches for global river output estimations;
• Legislative/regulatory efforts, such as monitoring programs and measures against plastic pollution in freshwater systems.

Session assets

Orals: Wed, 17 Apr | Room 2.15

Plastic pollution below the river surface
On-site presentation
Stephanie B. Oswald, Ad M. J Ragas, Margriet M Schoor, and Frank P. L. Collas

Rivers act as the main transportation pathways for land-based plastic litter to the ocean. Recently, rivers have also been identified as potential sinks and reservoirs for plastics. A significant part of plastic remains in and around rivers for extended periods, and only travels short distances in river systems. However, knowledge of plastic transport over different depth profiles in rivers remains limited. In this study, we measured the vertical distribution of macro- and mesoplastic concentration and composition. An extensive monitoring campaign was performed in the river Rhine and its two major branches, i.e. Waal and IJssel using a larvae net and a trawl net, methodologies that allow for differentiating between sampling depths. Subsequently, in order to estimate the relationship between the surface transport of plastic items compared to the transport in deeper layers in the water column, an extrapolation factor was derived per day for the middle and bottom nets divided by those found in the surface net. The predominant recorded items among the investigated rivers and monitoring techniques were fragments of soft mesoplastic falling under the category “Plastic film plastics 0-2.5 cm (soft)". The distinction among the observed macro- and mesoplastic OSPAR categories collected in different layers in the water column was limited between techniques. At the sampling sites in the river Waal, river Rhine, and river IJssel, during larvae net monitoring, for both macroplastic and mesoplastics, hard plastics were more frequently found on the river surface, while soft plastics were more frequently detected near the river bottom. The average of the calculated extrapolation factor ranged between 0.45 - 3.51 and 0.70 – 1.72 for macroplastic and mesoplastic, respectively during larvae net monitoring. During trawl net monitoring, the average of the calculated extrapolation factor of macroplastic ranged from 0.82 – 1.30, and for mesoplastic transport ranged from 0.52 – 1.40. Additionally, during larvae net monitoring, extrapolation factor values indicated that mesoplastics showed varying abundances, with the greatest concentration at the bottom of the water column. Followed by high concentrations on the water surface, and with the lowest concentration located in the middle of the river. The trawl net method exhibited subtler differences in macro- and mesoplastic distribution across depths. Vertical mixing was intensified during higher discharge events as a result of turbulent flow. Overall, the findings of this study show that estimates of plastic concentrations solely based on surface transport could result in an underestimation of riverine plastic transport.

How to cite: Oswald, S. B., Ragas, A. M. J., Schoor, M. M., and Collas, F. P. L.: Beyond the Surface: Vertical distribution of plastic pollution in Dutch rivers , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-14024, https://doi.org/10.5194/egusphere-egu24-14024, 2024.

On-site presentation
Stefan Krause, Thainne van Dijk, Lee Haverson, Uwe Schneidewind, Liam Kelleher, Sophie Comer-Warner, and Jim Best

Microplastics in rivers and streambed sediments represent a significant risk to ecosystem health and functioning locally, but also contribute to the total load of plastic waste transported towards the oceans. Despite increasing recognition of the importance of rivers as major conduits that are connecting terrestrial sources of mismanaged plastic waste across river basins to the oceans and that can also form important long-term sinks, actual estimates of riverine plastic waste contributions to the oceans have focused exclusively on floating, and sometimes suspended, plastic debris. However, the role of plastic waste, and in particular of microplastic particles when transported as streambed sediments, and their contribution to the total riverine plastic particle load has not yet been established. Indeed, the mechanisms of microplastic deposition and accumulation, and the resulting spatial patterns within riverine sediments, remain poorly understood.

Here, we present a first attempt of combining observations of microplastic concentrations in riverbed sediments with geophysically aided quantifications of bedload sediment transport to estimate contributions of bedload-transported microplastics to the total plastic waste load of a major European river, the River Waal, a Dutch tributary of the River Rhine. We therefore analysed microplastic concentrations in the top 20 cm of streambed sediments at 18 locations across a sequence of transects covering characteristic dune bedforms in the River Waal to establish characteristic ranges and spatial distributions of microplastic concentrations at the riverbed. Analysis of a 420cm deep sediment core was used to quantify the vertical microplastic distribution in the active zone and beyond. Following organic matter digestion and density separation, identified microplastics were counted and characterised for their particle size and shape using fluorescence microscopy aided by Nile Red staining. Additionally, polymer identification was performed on identified microplastic particles using micro-Raman spectroscopy.

Time series of multibeam (MBES) bathymetric information, together with sub-bottom profiler data (parametric echo sounder, PES) of subsurface sedimentary structures, were used to characterize the transport dynamics of recent alluvial dune sediments of the active river channel, where migrating dunes represent the main bedform that control microplastic transport and burial. This information of alluvial dune movement was used to derive bedload transport budgets for the River Waal. When combining these sediment transport estimates with the ranges of microplastic concentrations observed at the surface of streambed sediments, our analysis yields first insights into the potential ranges of microplastics transported as bedload, revealing that these can be substantial and represent an under-recognized fraction of the total plastic waste load transported towards the oceans. While creating budgets at these scales remains highly uncertain given that sample locations and times are restricted by the challenges inherent to microplastic analyses in natural media, our results highlight the need for further exploring the mechanistic drivers of riverine microplastic transport and highlight the importance of streambed sediments as long-term storage zones and legacy pollutants of microplastics that can have profound impact on downstream ecosystem health and functioning.

How to cite: Krause, S., van Dijk, T., Haverson, L., Schneidewind, U., Kelleher, L., Comer-Warner, S., and Best, J.: Bedload transport contributions to the microplastic load of the River Waal, Netherlands, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8874, https://doi.org/10.5194/egusphere-egu24-8874, 2024.

The role of floods and hydrology in riverine plastic propagation
On-site presentation
Caspar Roebroek, Adriaan Teuling, Martine Van der Ploeg, and Tim Van Emmerik

Global plastic pollution in the environment is of widespread concern. Rivers have been recognised as an important transport pathway, leading to the spatial redistribution of land-based plastic, and as a key source of plastic in the world’s oceans. Several global models have been developed to estimate the transport, accumulation and export of plastics into the ocean. Many, if not all, of these attempts formulate the river plastic transport dynamics based on estimates of land-based plastic pollution and river discharge. However, the direct relationship between discharge and the river plastic flux is put into question by river plastic pollution observations, which have largely failed to obtain any significant correlation between discharge and the plastic flux at non-extreme discharge levels. Here, we seek to explain these counterintuitive findings and provide a new perspective on how the riverine plastic research and models could improve. We address this by separating the driving forces of plastic transport into the transport capacity (transport), and the potential plastic load (supply). This perspective provides an explanation of the absence of generalizable correlations between discharge and the riverine plastic flux observations. We also highlight the need to broaden the focus of plastic research to include not only the flux in the river, but also the current plastic stocks and fluxes of the whole river systems and their relationship to human behaviour. 

How to cite: Roebroek, C., Teuling, A., Van der Ploeg, M., and Van Emmerik, T.: Limited role of discharge in global river plastic transport , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11235, https://doi.org/10.5194/egusphere-egu24-11235, 2024.

Virtual presentation
Reza Dehbandi, Zainab Rasouli, Mohammad Ali Zazouli, Nafiseh Khodabakhshloo, Nouraddin Mousavinasab, Habib Nejati, Yahya Esfandiari, Jaswant Singh, and Stefan Krause

Microplastics (MPs), as global emerging pollutants, have received significant attention worldwide due to their wide spread presence in aquatic and terrestrial ecosystems. However, the mechanisms controlling their fate and transport through river networks remains poorly understood. This study investigates the spatio-temporal distribution of MPs in two contrasting rivers (Tajan and Talar) discharging to southern coasts of the Caspian Sea, Iran and identifies pollution sources and their activation. In both rivers, MPs were dominated by black-gray larger-sized (1000-5000 μm) Polystyrene (PS)particles. Spatially, MPs concentrations in both rivers differ from upstream to downstream and showed uneven distribution. The March 2019 flood event affected on the concentration and patterns of MPs in river sediments. The total MPs concentration in both river sediments in all stations significantly decreased from pre to post-flood time (p-value<0.05). It is hypothesized that during the flooding that occurred between spring and summer sampling campaigns, the active surface sediment layer of the streambed is likely to have been mobilized by the increased flow, leading to large scale resuspension of sediments and MPs, releasing MPs into the overlaying water column and consequently, causing a reduction of MPs abundance in streambed sediments. The result indicated that in such stormwater and flood events, both river can act a role of active source for MPs flux for Caspian Sea in downstreams. Our results highlight the importance of different local sources and particle release mechanisms for microplastic transport towards the Caspian Sea, the largest inland lake in the world.

Keywords: Microplastics, River, Sediment, Transport mechanisms, Flooding

How to cite: Dehbandi, R., Rasouli, Z., Zazouli, M. A., Khodabakhshloo, N., Mousavinasab, N., Nejati, H., Esfandiari, Y., Singh, J., and Krause, S.: The impact of flood events on the spatio-temporal variability of microplastics in the river sediments of two contrasting streams discharging towards the southern Caspian Sea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12031, https://doi.org/10.5194/egusphere-egu24-12031, 2024.

On-site presentation
Tim van Emmerik

Reducing plastic pollution requires a thorough understanding of its sources, sinks, abundance, and impact. The transport and retention dynamics of plastics are however complex, and assumed to be driven by natural factors, anthropogenic factors, and plastic item characteristics. Current literature shows diverging correlations between river discharge, wind speed, rainfall, and plastic transport. However, floods have been consistently demonstrated to impact plastic transport and dispersal. Here, we present a synthesis of the impact of floods on plastic pollution in the environment. For each specific flood type (fluvial, pluvial, coastal and flash floods), we identified the driving transport mechanisms from the available literature. We introduce the plastic-flood nexus concept, which is the negative feedback loop between floods (mobilizing plastics), and plastic pollution (increasing flood risk through blockages). Moreover, we assessed the impact of flood-driven plastic transport, and argue that increasing flood resilience also reduces the impact of floods on plastic pollution. In this paper we provide a perspective on the importance of floods on global plastic pollution. We argue that increasing flood resilience, and breaking the plastic-flood nexus, are crucial steps towards reducing environmental plastic pollution.

How to cite: van Emmerik, T.: The impact of floods on plastic pollution, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8521, https://doi.org/10.5194/egusphere-egu24-8521, 2024.

Modelling approaches for understanding plastic transport and retention along the river course
On-site presentation
Nerea Portillo De Arbeloa and Alessandra Marzadri

The surge in plastic production and its widespread usage in modern society have escalated the generation of plastic waste, resulting in the prevalent presence of microplastics (MP) in various ecosystems. Their stability and resistance to degradation promotes their persistence and accumulation in the environment, posing significant threats to ecological and human health. River systems acting as connection pathways between lands and oceans, play an important role in controlling the movement of MP. Therefore, understanding which are the main transport mechanisms that control the fate of MP in fluvial settings remains an important challenge.

To this end, we developed a process-based model that solves the advection-dispersion-reaction equation (ADRE)  to predict how the amount of MP changes along the river network. The model considers MP inputs from anthropogenic sources and characterizes the transport and removal mechanisms (i.e. sedimentation, burial, resuspension, and bank removal) according to the different hydro-geomorphological conditions of the reaches that compose the fluvial network. The capability of the model to capture observed concentrations of MP was tested by using available literature data. Comparison between observed and modeled concentration of MP confirm the robustness of the proposed tool  and its versatility to dynamically represent the MP transport-removal processes. Model results  can be helpful to understand and address the challenges posed by MP pollution in riverine systems. 

How to cite: Portillo De Arbeloa, N. and Marzadri, A.: Rivers as Conduits: A Comprehensive Model of Microplastic Fate and Transport, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-16341, https://doi.org/10.5194/egusphere-egu24-16341, 2024.

On-site presentation
John Armitage and Sébastien Rohais

Rivers are the primary pathway of microplastic pollution from source to the eventual sink in the marine environment. However, like sediments, microplastic will become trapped within the fluvial system as it makes its way from source-to-sink. There is therefore the potential that rivers are an important reservoir of microplastic pollution globally. To explore the transport of microplastic through the fluvial system we develop a reduced complexity model of microplastic erosion, transport, and deposition that builds on methods developed for the transport of sediment. We apply this model to the river Têt, France, where there has been punctual monitoring of the flux of microplastic at the outlet. We find that the reduced complexity model captures the observed quantity of microplastic under reasonable assumptions of the relationship between microplastic sources and population density. The model that best matches observed fluxes of microplastic at the outlet of the Têt river requires between 1 and 10 ppm volume concentration of microplasitc per 200 × 200 m in the top half a meter of soil. This concentration of microplastic then travels within the river network with a settling velocity of between 10-4 and 10-6 m/sec. The model results imply that a large proportion of microplastic will become entrained within the sediments along the fluvial system. This model is a first step in assessing where to sample for microplastic pollution within river networks and points to regions susceptible to microplastic pollution.

How to cite: Armitage, J. and Rohais, S.: A numerical model of microplastic transport for fluvial systems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1963, https://doi.org/10.5194/egusphere-egu24-1963, 2024.

Plastic exports at the river-sea interface
On-site presentation
Kristina Enders, Robin Lenz, Franziska Fischer, Klaus Schwarzer, Guntram Seiß, Dieter Fischer, and Matthias Labrenz

The persistence of microplastics (MP) in aquatic environments presents a pressing concern, with sediments serving as substantial repositories for these anthropogenic particles. Estuarine depositional systems are sensitive indicator environments for MP monitoring as they: (1) represent aquatic-terrestrial interfaces acting as a bottleneck for MP accumulation coming from land (capable of capturing riverine run-off as well as the often highly populated coastal areas), (2) comprise a confined area, favourable for sampling initiatives as compared to other systems such as long river courses or disperse inland waters. Hence, understanding MP distribution in intricate estuarine systems is essential, yet current models often falter in capturing complexities to sufficiently describe the present pollution patterns for an entire geomorphological region.

We address this gap by employing machine learning techniques to predict spatial MP inventories deposited in the Schlei, Northern Germany. Notably, the complex hydrodynamic regime, influenced by narrowings and braided embayments, freshwater tributaries, wind-driven mixing, and brackish inflows, creates an interplay of fluvial and marine sedimentary processes, which poses non-trivial challenges for reliable modelling of sedimentary MP transportation. Our approach, termed NIXVEGS (Nested Iterative X-Validation-to-Ensemble-modelling through Grid Searches), leverages machine learning, integrating model selection, rigorous validation, and ensemble techniques tailored for small datasets.

We estimated ~20 trillion MP particles or ~14.5 tonnes (50-5000 µm) residing in upper sediments of the Schlei proper, emphasizing the pivotal role of sediments as primary MP reservoirs. Our modelling concept is founded on the idea of applying granulometric proxies to account for the hydrodynamic regime bias in observed MP concentrations. We found that the high complexity of the geomorphology and extreme input events – both are predominant conditions in our study system – produce major spatio-temporal discontinuities in MP data which are not alleviated by a granulometric normalisation. Here we use hydrodynamic tracer simulations to derive variables which incorporate these discontinuities in empirical predictive modelling, but discuss simpler possibilities to enable modelling studies in systems for which such simulation data might not be feasible to acquire.

This study provides a novel framework for geospatial prediction of MP inventories in complex aquatic systems. The integration of granulometric proxies and hydrodynamic discontinuities elucidates MP distribution patterns, offering a pathway for robust predictions and informed mitigation strategies. Our findings underscore the critical role of sediments in storing and reflecting the contemporary plastic legacy, crucial for comprehensive environmental management.

How to cite: Enders, K., Lenz, R., Fischer, F., Schwarzer, K., Seiß, G., Fischer, D., and Labrenz, M.: Mapping the Plastic Legacy: Geospatial Predictions of a Microplastic Inventory in a Complex Estuarine System Using Machine Learning, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20087, https://doi.org/10.5194/egusphere-egu24-20087, 2024.

On-site presentation
Musadiq Usman, ilaria Micella, and Maryna Strokal

The level of concern regarding plastic pollution within aquatic ecosystems has surged in recent years. The African continent is urbanizing more rapidly than other regions of the world with many countries experiencing a shift from predominantly rural populations to having more than half of their populations living in urban areas. Despite the stunning rate of urbanization and the undeniable impact on waste generation, there is a striking knowledge gap yet to address how pollution levels are changing under the twin pressures of urbanization and climate change for Africa. The need for studies that could predict pollution levels, while also addressing the role of waste management in the export of plastics into African rivers, becomes pressing.

Our study aims to identify effective domestic waste management strategies to reduce future river export of macro- and microplastics to the coastal waters of Africa. To this end, we apply the existing MARINA-Plastics model (Model to Assess River Inputs of pollutaNts to the seAs for plastics) to all sub-basins in Africa to better understand the trends and sources of macro- and microplastics for the past (2010 and 2020) and future (2050) based on the Shared Socio-Economic Pathway (SSPs) and Representative Concentration Pathway (RCPs).

Our model results show that in the past, the total river export of plastics to all coastal waters of Africa increased by 21% between 2010 and 2020. Such increases are a result of urbanization activities contributing more sewage connections and poorly treated wastewater from households. Most of the river export of plastics was macroplastics (over 80% in the past years). However, the share of microplastics in this total plastics increased from 3% in 2010 to 17% in 2020, indicating the increasing impact of urbanization over time in the recent past. In the future, the river export of plastics to all coastal waters of Africa is projected to further increase by more than double, between 2020 and 2050. This is a result of an increase in both river export of macro- (134%) and microplastics (59%) during this period. These trends are predominantly associated with factors such as increasing production and consumption patterns, ongoing urbanization and other relevant contributors (e.g. climate change).

We further develop alternative scenarios oriented towards four directions for Africa. These alternative scenarios incorporate the implementation of different reduction options such as improvements in wastewater treatment, reductions in the consumption of plastics, better waste collection, and an optimistic scenario where all three strategies are combined. We quantify the impacts of these reduction options on the future river export of plastics for Africa under global change. Our study is useful for understanding the sources and spatial variability of plastic pollution in rivers and coastal waters of Africa under global change trends. It is relevant to support decision-makers and waste managers in the implementation of policies to achieve sustainable targets for responsible consumption & production (SDG 12), and clean water (SDG 6).

How to cite: Usman, M., Micella, I., and Strokal, M.: Domestic waste management strategies to reduce future river export of macro- and microplastics to the coastal waters of Africa, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2033, https://doi.org/10.5194/egusphere-egu24-2033, 2024.

On-site presentation
Friederike Stock, Katsia Pabortsava, Richard Lampitt, Maria Luiza Pedrotti, Rocio Rodriguez, Aaron Beck, Eric Achterberg, Kathrin Voges, Christopher Feltham, Lindsay Scheidemann, Anja Engel, Sandra Golde, and Alice Horton

Microplastics have been investigated for over 45 years especially in the marine environment, but only in the past years research has started to focus on freshwater environments. In the frame of the H2020 LABPLAS project, different compartments in the Elbe and Thames river basins and the North Sea were studied in order to better understand the sources, transport, distribution and impacts of plastic pollution and to detect the amount of plastics transport via the rivers into the sea.

In the frame of the project, a winter and a summer campaign were conducted 2022 and samples taken from 6 sites within each river basin and from 4 sites from the North Sea between the Elbe and Thames estuaries. Samples collected were floating macroplastics, surface microlayer samples (Garrett screen), water samples (10-1000 µm with a pump and stainless-steel filters; >335 µm using a manta net) and sediments (with a Van-Veen-grabber). Density separation and organic digestion took place and analysis was done with a hyperspectral camera, FTIR and LDIR.

The preliminary show that microplastics are present in all samples. The number of particles varies significantly between the compartments, sampling sites and the seasons showing the complexity of plastic sampling and analysis. In the sediments (>10 µm), considerably more microplastics were counted than in the water. Higher values were observed close to cities and the Elbe estuary, in the North Sea close to the Thames estuary. In general, more microplastics are present in manta nets (>335 µm) of the tidal part of the rivers than in the freshwater part. The contrary occurs for small microplastics (10-1000 µm). Only few macroplastics were found. Most common polymers were PP, Acrylates/PU/Varnish, PS and PE as well as PTFE and rubber.

How to cite: Stock, F., Pabortsava, K., Lampitt, R., Pedrotti, M. L., Rodriguez, R., Beck, A., Achterberg, E., Voges, K., Feltham, C., Scheidemann, L., Engel, A., Golde, S., and Horton, A.: From the river to the sea: Microplastics in water and sediments of the Elbe and Thames rivers and the North Sea, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18967, https://doi.org/10.5194/egusphere-egu24-18967, 2024.

Posters on site: Thu, 18 Apr, 10:45–12:30 | Hall A

Display time: Thu, 18 Apr 08:30–Thu, 18 Apr 12:30
Lisa Jagau, Benjamin Gilfedder, Jan Fleckenstein, and Vadym Aizinger

Numerical modeling is an efficient tool for quantifying transport and sedimentation patterns of microplastic (MP) particles in lentic systems. To evaluate these patterns based on a specific research area we set up a three-dimensional hydrodynamic and transport model for a reservoir in Germany.

We partition the computational domain with an unstructured mesh to optimally capture the geometry of the reservoir and to adapt the mesh resolution. Thereby, shallow areas and those with steep bathymetry gradients are represented at a particularly high resolution. In vertical direction, we use a combination of z- and sigma-layers. To quantify the effects of the grid on the model results, we perform a sensitivity analysis for different horizontal and vertical mesh resolutions.

For the hydrodynamic simulations we use the Delft3D Flexible Mesh Suite (Delft3D FM). We calibrate and validate the hydrodynamic model utilizing monthly measured vertical temperature profiles for two different years. For simulating the MP transport, we rely on the sediments and morphology module of Delft3D FM. This module is based on a Eulerian approach which allows us to efficiently simulate large concentrations of MP particles.

How to cite: Jagau, L., Gilfedder, B., Fleckenstein, J., and Aizinger, V.: Three-Dimensional Hydrodynamic and Microplastic Transport Model for Lentic Systems, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15995, https://doi.org/10.5194/egusphere-egu24-15995, 2024.

Suhas Puranik, Ilaria Micella, and Maryna Strokal

Plastic pollution in aquatic ecosystems has become a major concern due to the adverse consequences it poses to marine and human health. Rivers are a major source of inputs of plastic waste into seas. Modelling studies in the past have estimated plastic fluxes into seas for microplastics or macroplastics. However, sources of both macro- and microplastic exports by rivers to coastal waters and their past and future trends have hardly been addressed simultaneously in a spatially explicit way (e.g., sub-basins). This includes both point sources (sewage) for microplastics from car tyre wears, personal care products, household dust and laundry as well as diffuse sources (mismanaged solid waste) for macroplastics and their fragmentation to microplastics. This study aimed to analyse the past (2010-2020) and future (2020-2100) river export of macro- and microplastics using the MARINA-Plastics model using a scenario with the rapid urbanization and high economic development under high global warming in the existing MARINA-Plastics (Model to Assess River Inputs of pollutaNts to seAs for Plastics). The model results show that estimated that globally, the annual river export of macroplastics is modelled to decrease by only 7% whereas the river export of microplastics is modelled to increase by 144% between 2010 and 2020. The large increase for microplastics is associated with increasing trends in urbanization over the period of 2010-2020. In the future, globally, the annual river exports of macroplastics are projected to increase by 118% and microplastics are projected to decrease by 8% in 2100. The sub-basins of the Atlantic, Indian and Pacific Oceans will account for more than 85% of the total river export of plastics in the future. The large increase for macroplastics is related due to poor management of waste and poor collection rates. The hotspots for macroplastic pollution in coastal waters are modelled to shift from Europe and North America to Africa and Asia in the future. Our insights could inform the design of plastic reduction policies at the international level and support the achievement of Sustainable Development Goal 14 (clean marine waters).

All authors acknowledge the support of the Water Systems and Global Change Group of Wageningen University. I. Micella is supported by the European Union's Horizon 2020 research and innovation program under the Marie Sklodowska-Curie Grant Agreement No. 956623 (InventWater).

How to cite: Puranik, S., Micella, I., and Strokal, M.: Global plastic export by rivers: large differences in trends between microplastics and macroplastics , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-2649, https://doi.org/10.5194/egusphere-egu24-2649, 2024.

Miranda Stibora, Tim van Emmerik, Kryss Waldschlager, Daniel González Fernández, and Albrecht Weerts

Plastic waste is globally of great concern. Rivers have the potential to transport and accumulate large amounts of plastic waste which can have harmful effects on human and animal welfare. Given the durability of plastic waste, the presence of plastic in river environments is forecasted to continue rising. As part of the project INSPIRE (Innovative Solutions for Plastic Free European Rivers), the main goal of our research is to establish a baseline for the current state of plastic litter in European rivers, with the overarching aim of facilitating the reduction of plastic waste. The initial step in achieving this reduction is the accurate modelling of plastic waste in rivers.

There is currently a lack of cohesion between plastic transport models, with models independently predicting the export of various plastic sizes (micro- and macroplastics) and in different riverine compartments (river water, riverbed sediment, riverbank). We aim to develop a single model accounting for the interaction between plastic sizes, due to degradation, and mediums, due to resuspension. Existing plastic models also generally use an annual time scale for predicting plastic concentrations in rivers. To estimate the impact of short-term climatic events, like storms and floods, on plastic concentrations in rivers, a higher temporal resolution would add value to plastic modelling.

Challenges in plastic modelling have arisen from a lack of data-availability. However, with the rise in focus on plastic research, river plastic data availability has steeply expanded, supporting a revision of current plastic modelling approaches. Our research aims to provide a more holistic approach to plastic modelling by exploring current modelling approaches to ensure an up-to-date understanding of factors affecting plastic concentrations in rivers.

Here, we revise and extend previously developed global river plastic models to also account for transport and retention. Modelling the plastic transport in rivers for all plastic sizes and in all mediums will be vital for identifying the types of plastic accumulating in the river, and in which locations. This will be imperative for the effective implementation of mitigation measures to ensure clean and safe waters for the future.

How to cite: Stibora, M., van Emmerik, T., Waldschlager, K., González Fernández, D., and Weerts, A.: Revising global river plastic transport, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7542, https://doi.org/10.5194/egusphere-egu24-7542, 2024.

Inga Retike, Inta Dimante-Deimantovica, Alise Bebrite, Māris Skudra, Maija Viška, Jānis Bikše, Marta Barone, Anda Prokopovica, Sanda Svipsta, and Juris Aigars

We present a comprehensive assessment of micro- and mesoplastic pollution along 24 beaches of the Latvian coastline (Northern Europe, Baltic states) establishing a baseline for pollution distribution in the Baltic Sea Region. A detailed analysis of sand granulometry, hydrodynamic variables (waves and currents) and tourism intensity allowed us to understand better factors that drive plastic pollution distribution along beaches. Over 250 volunteers participated in the sample collection highlighting the importance of citizen science as a tool to support data collection.

Our findings reveal a lower concentration of micro- and mesoplastic particles in the semi-closed Gulf of Riga (0.10 particles/kg dry sand) compared to the open Baltic Sea (0.16 particles/kg dry sand). The microplastic size fraction (1-5 mm) showed a distinct cluster with higher concentrations and fiber abundance in coarser beach sands of the open Baltic Sea and eastern Gulf of Riga. We emphasize hydrodynamics as a key factor in the distribution and accumulation of microplastics, while impacts are predominantly of local scale and vary considerably across existing studies. No clear pattern of recreational activities on plastic distribution was identified. Studies elaborating on aspects like sampling season, wave energy, wind, currents, sand granulometric properties, and pollution sources are encouraged to enhance result interpretation and move towards more comparable micro-litter case studies.


Dimante-Deimantovica I, Bebrite A, Skudra M, Retike I, Viška M, Bikše J, Barone M, Prokopovica A, Svipsta S and Aigars J (2023) The baseline for micro- and mesoplastic pollution in open Baltic Sea and Gulf of Riga beach. Front. Mar. Sci. https://www.frontiersin.org/articles/10.3389/fmars.2023.1251068/full

This work was supported by voluntary donations from the student sorority Selga, the European Regional Development Fund post-doctoral projects No. and No., ESF Project No. “Strengthening of Professional Competence of Daugavpils University Academic Personnel of Strategic Specialization Branches 3rd Call”, and the European Economic Area (EEA) Financial Mechanism 2014–2021 Baltic Research Programme (grant EMP480).

How to cite: Retike, I., Dimante-Deimantovica, I., Bebrite, A., Skudra, M., Viška, M., Bikše, J., Barone, M., Prokopovica, A., Svipsta, S., and Aigars, J.: Micro- and mesoplastic pollution along the beaches in the open Baltic Sea and Gulf of Riga, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7586, https://doi.org/10.5194/egusphere-egu24-7586, 2024.

Olaf Büttner, Alexander Schwab, Christiane Katterfeld, Christian Schmidt, and Dietrich Borchardt

Microplastics (MP) enter the aquatic environment through both diffuse and point sources, and are transported through the river networks into the seas and oceans. MP threatens the aquatic ecosystems and are present in water, sediment and biota. One of the main entry paths of MP pollution are wastewater treatment plant (WWTP) effluents as well as untreated surface runoff and combined sewer overflows (CSO).

In this study, we aimed to estimate the average annual load of MP to the Seas and Oceans for 125 European catchments of different sizes.

We coupled a mass balance model modified adapted from (Bollmann et al. 2019) and a transport model representing the river network as graph theory network (GTN). The GTN is based on the HydroShed network (Lehner et al. 2008) with WWTPs inserted as additional nodes. The partitioning of MP was calculated for three sinks (sewage sludge, river sediments, load to the sea) relying on literature-derived MP concentrations from untreated surface runoff, combined sewer overflow, and WWTPs effluents. Concentrations for average discharge conditions were calculated for all stream segments using steady-state discharge data from the HydroShed database.

Based on 125 European catchments containing approximately 75% of the European WWTPs with population equivalents > 2000, we found that 77% of MP entering the river network originates from WWTP effluents, the remaining 23% is sourced from untreated surface runoff and combined sewer overflow. Of the MP that has entered the river systems, 24% are transported to seas and ocean while 76% accumulate in the river sediment. The most sensitive parameters in the model related to the loads to seas and oceans are sedimentation rates.

In a next step, the model will be updated with improved hydrological parameters. Furthermore we will apply it to future scenarios of hydro-climatic and socioeconomic conditions. As the HydroShed database is globally available, the model can be applied to other regions of the world.


Bollmann, U.E., Simon, M., Vollertsen, J. and Bester, K. (2019) 'Assessment of input of organic micropollutants and microplastics into the Baltic Sea by urban waters', Marine Pollution Bulletin, 148, 149-155, available: http://dx.doi.org/https://doi.org/10.1016/j.marpolbul.2019.07.014.

Lehner, B., Verdin, K. and Jarvis, A. (2008) 'New global hydrography derived from spaceborne elevation data', Eos, Transactions American Geophysical Union, 89(10), 93-94.

How to cite: Büttner, O., Schwab, A., Katterfeld, C., Schmidt, C., and Borchardt, D.: Microplastic transport in European river networks, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-7796, https://doi.org/10.5194/egusphere-egu24-7796, 2024.

Javier Rodrigo-Ilarri, Natalya S. Salikova, María-Elena Rodrigo-Clavero, Saltanat E. Urazbayeva, Aniza Zh. Askarova, and Kuandyk M. Magzhanov

This work presents the outcomes derived from an environmental assessment of microplastic pollution resulting from solid waste landfills in the Akmola Region, situated in North Kazakhstan. This research represents a pioneering investigation conducted on microplastics within this specific region. This study encompasses a comprehensive examination of plastic waste disposal sites across the Akmola region, with a particular emphasis on evaluating the status of the municipal solid waste management system.

To characterize the plastic content within the waste present at the landfill sites, quantitative techniques were employed. Through experimental means, the composition and fractionation of plastics within the municipal solid waste (MSW) at the landfills were determined. These data were subjected to a comparative analysis, aligning them with official statistics and previously published scientific data from both Kazakhstan and other regions globally. The methodologies employed focused on the “soft” removal of organic substances through the use of oxidants which do not damage plastics, and were tested using a water-bath therapeutic treatment. Furthermore, an analysis of soil samples taken from the landfills unveiled the ultimate retention of microplastic particles, attributed to leachate and rainwater runoff. Extracts were obtained from the subsoil samples using a density-based separation process, involving a three-step extraction followed by subsequent filtration of the resulting supernatants. In addition, the soil samples underwent examination through dry-phase particle fractional separation. The particles were meticulously enumerated and classified, and their dimensions were measured employing microscopic techniques coupled with photographic documentation. The outcomes stemming from these diverse tests will serve as fundamental input for the forthcoming numerical modeling endeavor, which aims to simulate the behavior of microplastics within both soil and water. 

How to cite: Rodrigo-Ilarri, J., Salikova, N. S., Rodrigo-Clavero, M.-E., Urazbayeva, S. E., Askarova, A. Zh., and Magzhanov, K. M.: Environmental Assessment of Microplastic Pollution Induced by Solid Waste Landfills in the Akmola Region (North Kazakhstan), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8587, https://doi.org/10.5194/egusphere-egu24-8587, 2024.

Uwe Schneidewind, Anna Kukkola, Robert Runkel, Sheila F. Murphy, Liam Kelleher, Lee Haverson, Gregory H. Sambrook Smith, Iseult Lynch, and Stefan Krause

Microplastic particles (MPs) are emerging contaminants of concern that have been isolated and described in various environmental compartments. River networks can not only act as major transport pathways of MPs to the world’s oceans, but also as intermediate and long-term sinks, as well as redistributors of MPs. MP in-stream concentration and load (concentration multiplied by discharge) are key parameters when quantifying MP downstream transport and provide an indication towards potential impacts on downstream ecosystem health. MP concentrations and loads within a catchment or river network presumably vary in space and time, yet extensive studies addressing the impact of anthropogenic factors (e.g., water management practices, point source release, landuse) in conjunction with such variability on downstream MP evolution are still scarce.

Here we present key findings from two recent studies. The first study compares downstream MP concentrations and loads for the two neighboring catchments of Boulder Creek (BC) and South Boulder Creek (SBC), Colorado, USA, which vary in their population density and degree of urbanization. We collected 21 water samples (50 L, filtered through >63 µm mesh) from locations along both river channels. For each river segment we also obtained discharge information that helped us quantify MP in-stream loads and determine segment-wise load differences. Samples underwent digestion with Fenton’s reagent before potential MPs were characterized using fluorescent microscopy and Raman spectroscopy. We found that the degree of catchment urbanization influenced downstream MP patterns for both rivers, with BC (higher degree of urbanization and population density) expressing higher MP concentrations and loads than SBC. We also observed extensive downstream MP removal at certain locations where river flow was diverted for anthropogenic use in both streams. This caused a stepwise reduction of downstream MP loads and redistribution of MPs within the wider catchment.

The second study looked at the temporal evolution of in-stream MP concentrations and loads about 1000 m downstream of a wastewater treatment plant (WWTP) at a sidearm of the River Blythe, UK. The WWTP represented a point-source and was the only major MP source to the stream at our sampling location. Water samples (3x 100 L, filtered through >63 µm mesh) were collected at different intervals (monthly over an entire year, weekly over two months, hourly over four days) to better relate possible variations in MP concentrations and loads to changes in WWTP effluent discharge and to study the representativeness of snap-shot sampling. Samples were digested with Fenton’s reagent before fluorescent microscopy and Raman spectroscopy. Results indicate that temporal variability in in-stream MP load could be based on both changes in stream discharge and changes in WWTP effluent concentration, individually or simultaneously. MP loads varied by up to an order of magnitude over the course of one hour, highlighting the importance of obtaining enough representative MP data when characterizing a river system.

Our results show that spatial and temporal variability of MP concentrations and loads in rivers and river networks can be highly variable. This variability should be considered in large scale modeling exercises quantifying plastic fate and transport to the oceans.

How to cite: Schneidewind, U., Kukkola, A., Runkel, R., Murphy, S. F., Kelleher, L., Haverson, L., Sambrook Smith, G. H., Lynch, I., and Krause, S.: Spatial and temporal variability in in-stream microplastic loads can impact downstream plastic export, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9279, https://doi.org/10.5194/egusphere-egu24-9279, 2024.

Daniel González-Fernández, Caspar T.J. Roebroek, Charlotte Laufkötter, Tim H.M. van Emmerik, and Andrés Cózar

The plastic pollution crisis demands establishing a global science-policy framework to achieve a circular economy for plastics. Such a framework should be based on scientific evidence to evaluate the success of mitigating plastic pollution in terrestrial, freshwater, and marine environments. This work focuses on the role of rivers as main pathways connecting land-based plastic to the marine environment. Existing large-scale estimates of river plastic input to the ocean used different and contrasting choices in their modelling approaches, e.g., including highly variable number of rivers in the global outputs, differing item-to-mass conversion factors, and extrapolations from microplastic to macroplastic loads. We observed that estimates can diverge up to five orders of magnitude when global models are applied to individual rivers, denoting large uncertainties in the data and approaches used to extrapolate results for the most polluting rivers at World and European scales. These uncertainties would not allow for a quantitative assessment of the effectiveness of plastic mitigation measures, as the expected reduction of plastics in the environment would vary within a much lower range than the modelled estimates. The way forward to provide meaningful assessments involves collecting comparable data using harmonized sampling methods, increasing fundamental understanding of plastic transport and retention dynamics, and a better understanding of spatio-temporal variability of plastic transport in rivers.

How to cite: González-Fernández, D., Roebroek, C. T. J., Laufkötter, C., van Emmerik, T. H. M., and Cózar, A.: A comparative analysis of global models for riverine plastic input to the ocean, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18573, https://doi.org/10.5194/egusphere-egu24-18573, 2024.

Richard Warren, Richard Cooper, Andrew Mayes, Stefanie Nolte, Kevin Hiscock, and Jonah Tosney

High loads of microplastics and anthropogenic fibres can be discharged from wastewater treatment plants (WWTPs) into surface water bodies. Integrated Constructed Wetlands (ICWs) are potentially well suited to provide a cost-effective mitigation solution at small WWTPs where conventional treatment is prohibitively expensive. ICWs consist of a series of connected ponds (receiving all of their inflow from WWTP effluent) that are planted with diverse native vegetation, and are thus designed to improve downstream water quality. This study aimed to assess the microplastic and anthropogenic fibre retention efficiency of two ICWs (Northrepps and Ingoldisthorpe) in Norfolk (UK) over a 12-month period. Water samples were collected at approximately monthly intervals from the inlet and outlet of each wetland (n = 54) between June 2022 and May 2023, and fine bed sediment samples were collected from the Northrepps ICW (n = 23). Northrepps ICW received on average 351,588 (± 223,986) anthropogenic fibres day-1, with a retention rate of 99.3 %. No seasonal variation was observed in retention efficiency. Ingoldisthorpe ICW intermittently received anthropogenic fibres in low concentrations, with an average of 11,448 (± 518) day-1 and a retention rate of 100 %. Microplastics and anthropogenic fibres were prevalent in sediment samples of the first cell of Northrepps ICW, averaging 10,090 items kg-1 dry sediment, while none were found at concentrations above the limit of detection in the second or third cell. Of the 369 fibres analysed by ATR-FTIR, 55 % were plastic (dominated by polyester). Of the 140 suspected microplastic fragments analysed by ATR-FTIR, 73 % were confidently identified as plastic (mostly polystyrene, polyethylene, or polypropylene). This study demonstrates how ICWs can effectively retain sewage effluent derived microplastics and anthropogenic fibres. However, the accumulation of plastic waste in ICWs may complicate long term management and their cost-effectiveness. Research into the minimum size of the first cell to ensure that microplastics are retained within a small area of the overall wetland is recommended to improve long term management prospects.

How to cite: Warren, R., Cooper, R., Mayes, A., Nolte, S., Hiscock, K., and Tosney, J.: Sewage Derived Microplastic and Anthropogenic Fibre Retention by Integrated Constructed Wetlands , EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-215, https://doi.org/10.5194/egusphere-egu24-215, 2024.

Carlos René Green Ruiz, Jacqueline Hernández-Angeles, and Jose Roberto Rivera-Hernández

Given the concerning alert about the potential high toxicity of microplastics in the environment, in recent years, significant efforts have been made to understand more about the occurrence and behavior of microplastics on Earth. Focuses of these efforts include where they are found, mainly in higher concentrations; their transport pathways; their occurrence in a diversity of organisms; their toxicity; their relationship with other pollutants; and many other questions that still need to be answered. The present work is the first one to focus on the study of microplastics in a lotic exoreic environment in the tropical Mexican Pacific region. In this study, the occurrence, temporal variation, and chemical composition of microplastics found in the surface water and bed sediment of rivers of different orders from the Baluarte River Basin were investigated. In surface waters, an average of 0.23 microplastic-like particles per liter were found during both seasons, showing no significant differences between them. During the rainy season, there was an average concentration of 0.11 particles per liter. On the other hand, in sediment, the results showed average concentrations of 139.2 and 66.7 microplastic-like particles per kilogram for the dry and rainy seasons, respectively, with significantly higher concentrations during the dry season. Most of the analyzed microparticles were fibers and had light blue and transparent colours. Polyethylene terephthalate (PET) was the most found polymer in both environmental compartments, followed by cellophane and rayon. It is concluded that, in general, the microplastics found in the fluvial system of the Baluarte River Basin may come from the discharge of domestic wastewater, agriculture, fishing, garbage dumped on land, as well as the construction of a hydrological infrastructure in the area. For future more detailed studies, it is recommended to increase the number of sampling sites at varying distances from human settlements and to explore better methods for microplastic separation. If possible, it would be interesting to implement control measures in first-order rivers of the Baluarte River Basin.

How to cite: Green Ruiz, C. R., Hernández-Angeles, J., and Rivera-Hernández, J. R.: Microplastics in water and bed sediments from the Baluarte River Basin: Occurrence, behavior and composition, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11798, https://doi.org/10.5194/egusphere-egu24-11798, 2024.

Nathalie Grassineau, Louise Eldridge, and Simone Rossouw

Plastic has become an invasive material in modern human lifestyle and is heavily relied upon as an essential resource. It is identified as one of the chief environmental problems. Although identified primarily into marine environments, the main source of the plastics is from land and is discharged into our shores via rivers. To be able to lessen their impacts into the ocean, it is important to understand how to reduce their production upstream. This research is focussing on the fate of the secondary microplastics (MP) from when they leave the household with the greywaters to when they are released via the WWTP (wastewater treatment plant) discharges into our urban rivers.

The household laundry of synthetic textiles has been recognised as one of the largest sources of MP production. This counts for most of the MPs leaving our home via greywaters to reach urban WWTPs. Consequently, the study has focussed on MPs released from 24 washing machine loads, consisting of well-catalogued and weighed various combinations of synthetic garments, under “normal wash conditions”. It was determined that an average load can produce up to 93,000 MP fibres per kg, but it was found that heavier loads released fewer MP fibres. Using a full washing load can reduce the number of fibres produced by up to 70%.

To estimate the release of MPs into freshwater rivers from WWTPs, six discharges from urban plants from middle size towns around Greater London have been sampled and analysed. It was found that although MP quantities are very high the numbers vary greatly due to the age and the size of those sites, but also the technique that is used. It results in a range between 0.5 and 18 million MP per hour being released. This highlights that WWTPs are not advanced enough to remove MP pollution, making these discharges the main source into the freshwater environment.

Furthermore, the MP release from plant discharges into rivers is not the main secondary source as up to 98% of the MPs passing through WWTPs might end up as sludge that can later be applied to improve agricultural land for higher crop yields. This creates a major source of MP fibres into our rural rivers upstream of the urban hubs. Not only does this introduce microplastics to terrestrial habitats but it also creates a direct secondary pathway for microplastics to enter surface waters. This study highlights the urgency to update wastewater treatment and disposal practices to tackle the various issues of fibres getting into surface and groundwaters.

How to cite: Grassineau, N., Eldridge, L., and Rossouw, S.: The course of microplastics before and after UK WWTPs and their release into the environment., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19529, https://doi.org/10.5194/egusphere-egu24-19529, 2024.

Vadym Aizinger, Lisa Jagau, Benjamin Gilfedder, and Jan Fleckenstein

Microplastic (MP) particles are assumed to be potentially harmful to organisms in the hydrosphere. To better assess the exposure and the associated risk it is essential to quantify the transport and sedimentation behavior of MP particles in aquatic environments.

Using the Delft3D Flexible Mesh Suite we set up a three-dimensional hydrodynamic and MP transport model for lakes and reservoirs. Our focus is on modeling polymers with different densities and particle sizes to identify patterns of particle residence time and sedimentation. The reservoir Großer Brombachsee in Germany serves as the research site with realistic forcings and boundary conditions.

We present first results for horizontal and vertical distribution patterns for different polymer types. We found that the distribution of MP in the computational domain is strongly affected by both particle density and particle size. Smaller, lighter particles are spread over the entire horizontal extent of the reservoir, but particles of higher density or of larger size settle within a limited area around the inflow location, indicating a much higher settling velocity.

How to cite: Aizinger, V., Jagau, L., Gilfedder, B., and Fleckenstein, J.: Modeling the transport and residence time of microplastic particles in lakes and reservoirs, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18531, https://doi.org/10.5194/egusphere-egu24-18531, 2024.

Rahel Hauk, Martine van der Ploeg, Adriaan J Teuling, Winnie de Winter, and Tim HM van Emmerik

Rivers play a substantial role in plastic pollution transport and storage but the transport processes that determine macroplastic fate in the riverine environment are not fully understood yet. Usually it is unknown when and where specific plastic litter items entered the environment, therefore macroplastic transport is often studied via e.g. GPS trackers. However, the July 2021 flood provided an unique opportunity of spilled macroplastic items, with clearly known time and space of emission.
In July 2021 severe floods affected multiple European river catchments, including the Meuse catchment in Belgium. A dairy company located at the Meuse tributary Vesdre was flooded, with parts of their facilities and a lot of material washed away. Among the washed away material was also ~8 million empty dairy packages ("buttertubs"), which have a printed ID code that can be traced to their emission point. During macroplastic sampling immediately after the flood event, and in the following two years, we found 617 of these buttertubs along the Dutch section of the Meuse river (~66 - 328 km downstream of the dairy company). We used the buttertubs as tracers for macroplastic transport in the period that includes the flood event, and the following two years. Within 20 days of the flood event, some of the buttertubs were transported ~328 km and were found close to the Rhine-Meuse-Delta. However, the majority of buttertubs was transported less than 100 km within these 20 days, with an average transport distance between 9.75 - 18.25 km/day. Over the following two years the average transport distance decreased to 0.23 km/day. Which could imply that the buttertubs either were only transported across smaller distances in the following two years, or even not remobilized at all after being deposited during the flood event. Some of the buttertubs we also collected, and we investigated their mass and fragmentation development over time. 
In this unique opportunistic study, we found that the buttertubs mean transport distance moved downstream over the course of two years. The majority of them however, was deposited rather close to their emission point, even given the extreme flood situation. 

How to cite: Hauk, R., van der Ploeg, M., Teuling, A. J., de Winter, W., and van Emmerik, T. H.: Buttertubs spilled during the July 2021 flood as plastic transport tracers in the Dutch Meuse river, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-1759, https://doi.org/10.5194/egusphere-egu24-1759, 2024.

Ronja Ebner, Thomas Mani, and Laurent Lebreton

To tackle the accumulation of plastic in the open oceans and along the shorelines, it is necessary to identify and understand its input paths. With more than 4smaller coastal systems draining into the global oceans, this is a complex task. A global model representing a plethora of different systems is one way to approach this problem.

For this purpose we improved the global river model presented in Meijer et al., 2021 which is using multiple datasets such as topography, land cover, runoff, precipitation, wind, population density, landfills, dams and mismanaged plastic waste per country to estimate the magnitude of the input of plastic into the oceans. This is achieved by a mouth-2-source algorithm that originates from each river mouth. How far the influence of a given network reaches inland is dependent on the discharge within it and is parametrized with an abstract, global parameter, γ. The value of the latter can be calibrated using an analysis of both Eulerian and Lagrangian in-situ river plastic transport data from different river systems worldwide.

Our analysis highlights the importance of plastic transport experiments with high data-density. The model results put the global plastic input into the ocean close to 500 kt/yr and indicate that the influence of the numerous smaller coastal catchments needs to be taken into account  With this model we are further able to identify river systems that interesting for targeted action.

How to cite: Ebner, R., Mani, T., and Lebreton, L.: The Best of Both Worlds – Combining a Revised Global River Model to In-Situ River Plastic Transport Data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17345, https://doi.org/10.5194/egusphere-egu24-17345, 2024.

Posters virtual: Thu, 18 Apr, 14:00–15:45 | vHall A

Display time: Thu, 18 Apr 08:30–Thu, 18 Apr 18:00
Tadanobu Nakayama

Plastic pollution has been receiving considerable attention from scientists, policy makers and the public during the last few decades. Though some models succeeded to simulate transport and fate of plastic debris in freshwater systems (Meijer et al., 2021), a complete model is under development to elucidate the whole picture of plastic dynamics in continental scale. Previously, process-based eco-hydrology models, NICE (National Integrated Catchment-based Eco-hydrology)-BGC (BioGeochemical Cycle) (Nakayama, 2017), was applied to evaluate biogeochemical cycling in river basins ranging from local/regional to continental/global scales. Recently, the author linked NICE-BGC to plastic debris model that accounts for transport and fate of plastic debris (advection, dispersion, diffusion, settling, dissolution and biochemical degradation by light and temperature), and applied this new model to regional scale (Nakayama and Osako, 2023a) and global major rivers (Nakayama and Osako, 2023b). NICE-BGC was also improved to include the mass budget in water and bed sediment in order to show the seasonal variations of plastic fluxes. In this study, NICE-BGC was further extended to incorporate biofouling (with algae and phytoplankton) and heteroaggregation (with suspended particulate matter) to improve the accuracy of global plastic dynamics in global river basins and the amount of plastic flows from land into rivers and finally into the ocean. Model simulated size distribution of plastics in water and riverbed sediment of global major rivers and showed the difference of effect of biofouling and heteroaggregation in each river. In addition, the simulated result showed that flood events have a great impact on plastic mobilization and its high intra-annual variability mainly caused by settling, resuspension, and bedload transport (Hurley et al., 2018; van Emmerik et al., 2019). These results aid development of solutions and measures to reduce plastic input to the ocean, and help to quantify magnitude of plastic transport under climate change.



Hurley, E., et al. 2018. Nature Geoscience, 11, 251-257, doi:10.1038/s41561-018-0080-1.

Nakayama, T. 2017. Journal of Geophysical Research: Biogeosciences, 122, 966-988, doi:10.1002/2016JG003743.

Nakayama, T., Osako, M. 2023a. Ecological Modelling, 476, 110243, doi:10.1016/j.ecolmodel.2022.110243.

Nakayama, T., Osako, M. 2023b. Global and Planetary Change, 221, 104037, doi:10.1016/j.gloplacha.2023.104037.

van Emmerik, T., et al. 2019. Scientific Reports, 9, 13549, doi:10.1038/s41598-019-50096-1.

How to cite: Nakayama, T.: Towards improvement to understand plastic dynamics in global rivers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3263, https://doi.org/10.5194/egusphere-egu24-3263, 2024.