Displays

Research into the scope of litter pollution, particularly of plastic debris, in freshwater systems has shown similar levels to the marine and coastal environment. Global model estimates of riverine emission rates of plastic litter are however largely based on microplastic studies as long-term and holistic observations of riverine macroplastics are still scarce. Our study therefore aimed to contribute a detailed assessment of macrolitter in the transitional waters of three major North Sea tributaries: Ems, Weser, and Elbe. It was hypothesised that the larger and more intensely used, the more polluted the river would be. Litter surveys were carried out in four river compartments: along the embankment, on the river surface, in the water column, and on the river bed. Plastic generally comprised 88-100 % of all recorded debris items. Our data revealed spatio-temporal variability and distinct pollution levels for each compartment. Beaches had the highest debris diversity and were significantly more littered than vegetated sites and harbours. Stony embankments were least polluted. Benthic litter levels appeared substantial despite rapid burial of objects being likely due to high suspended sediment loads. Extrapolated to daily mean emission rates, more plastic litter is discharged into each estuary via the river surface than through the water column. Combining both, the Ems emits over 700 macroplastic items daily, the Weser more than 2,700, and the Elbe ~196,000 objects. Using the mean (median) plastic item mass recorded from water column samples, i.e. 6.3 g (1.7 g), this equates to ~4.5 (1.2) kg d^-1 and ~1.6 (0.4) t y^-1 of plastic waste discharged by the Ems, ~17.2 (4.6) kg d^-1 and ~6.3 (1.7) t y^-1 for the Weser, and ~1.2 (0.3) t d^-1 respectively ~451 (122) t y^-1 carried into the North Sea via the Elbe. These rates deviate considerably from previous model estimates of plastic loads discharged by said rivers. Future studies should therefore ground-truth model estimates with more river-specific and long-term field observations, which will ultimately help assess the effectiveness of waste management and reduction strategies inland and on water.

How to cite: Schöneich-Argent, R., Dau, K., and Freund, H.: Assessing litter loads and estimating macroplastic emission rates of three major North Sea tributaries – Ems, Weser, and Elbe – through holistic, field-based observations, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5891, https://doi.org/10.5194/egusphere-egu2020-5891, 2020.

Around 8 million tons of plastic waste are leaked from land into the ocean annually. One of the main pathways of plastic input into the ocean is rivers, but there is no comprehensive information about the amount and nature of litter transported. This study presents results of a monthly monitoring over a two years period in the estuary of Guadalquivir River, southern Spain. The samples, which consisted of passive hauls, were taken from a traditional glass eel fishing boat anchored with three nets working in parallel. The nets, with a mesh of 1 mm and an opening of 2.5 (width) × 3 (depth) metres, filtered around 60,000 m³ per sample. Our methodological approach allowed characterization of virtually all plastic sizes in river waters, comprising micro-, meso- and macroplastics. Plastic items were dominated by pieces of film (70% in number). Microplastics in the size interval from 2.5 to 4.0 mm represented half of the total identified items. Small fragments in Guadalquivir River comprised most of the plastic mass input to the sea. Our results support the relevance of fragmentation processes inland, and the role of rivers and estuaries as sources of microplastics to the ocean.

How to cite: Quintana Sepúlveda, R., González Fernández, D., Cózar Cabañas, A., Vilas Fernández, C., González Ortegón, E., Baldo Martínez, F., and Morales Caselles, C.: Plastic waste input from Guadalquivir River to the ocean , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19268, https://doi.org/10.5194/egusphere-egu2020-19268, 2020.

This study reports on the amount of plastic wastes in five river mouths discharging to Manila Bay, a natural harbor which drains approximately 17,000 km³ of watershed area. Of the 17 rivers discharging to the Bay, five rivers which run through the densely populated and highly urbanized Metropolitan Manila are included in the study namely, Pasig, Cañas, Tullahan, Meycauyan and Parañaque. A Waste Analysis and Characterization Study (WACS) was conducted to investigate the composition of the wastes that were on the river banks. Samples were taken from the wastes that were found lying on the banks. The wastes collected in each study site varied from each other, although plastic wastes and yard wastes were gathered from all areas. Based on their % wet weight, plastics alone comprised 28% of wastes in Cañas, 46% of wastes in Meycauayan, 42% of wastes in Parañaque, 37% of wastes in Pasig and 27% of wastes in Tullahan. The disposed plastics collected were also characterized and categorized into different types: hard plastic (PP, HDPE), film plastic (PP, PE), foam (PS, PUR) and other type (PVC, PET). In Cañas River, film plastics (79%) were the most ubiquitous type of plastic waste which primarily consist of different sachets of household products and single-use plastic bags. Few hard plastics and other types of plastic such as PVC and PET were collected. Meycauayan River and Parañaque River had almost the same plastic type distribution wherein the most dominant plastic type were hard plastics. These hard plastics collected were mostly composed of bottles of detergents and toiletries. Meycauayan River has relatively fewer establishments near its river mouth, indicating that the sources of the accumulated plastic wastes came from the mid and upstream of the river where the urbanized and industrialized areas were located. Furthermore, even though hard plastics represented 38% of wastes in Paranaque, numerous plastic straw ropes were collected as fishermen use these straws to tie up their boats to the docking area. Significant amount of foams  and PET bottles were also amassed in these rivers. Plastic wastes from the Pasig River were mostly comprised of both film plastics (39%) and hard plastics (30%). The plastic wastes taken were all household products directly dumped by the those residing by the Pasig River mouth. Notable quantity of foams and other types of plastic were fetched from the sampling area. Tullahan River has abundant amount of film plastics (35%) and foams (33%) in its river mouth. Some of these plastic wastes are stuck to the rafts tied up along the bank of the river. Sachets of household products were dominantly present. Few hard plastics and other type of plastic were extracted from the site. Substantial amount of plastic wastes in each of the river mouths signifies poor waste management infrastructure, lack of materials recovery facilities, and lack of discipline of people as these plastics are found to be directly dumped into the water bodies.  

How to cite: Tanchuling, M. A. and Osorio, E.: Plastic Wastes Survey in River Mouths Discharging to Manila Bay, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11731, https://doi.org/10.5194/egusphere-egu2020-11731, 2020.

Although freshwater systems are known to be the transport paths of plastic debris to the ocean, studies in rivers are rare. In recent years, measurements are advancing, but they hardly address the spatial distribution of plastic debris in the whole water column. Waste collecting activities in the Nationalpark Donau-Auen – a part of the Austrian Danube River to the East of Vienna – indicate that increasing quantities of plastic waste can also be found near the banks and within the inundation areas of our rivers. The EU financed project "PlasticFreeDanube" tries to find the sources, environmental impacts, transported amounts and paths, compositions and possible plastic accumulation zones.

A robust, net-based device was developed which can be applied at high flow velocities and discharges even at large rivers. The device consists of a strong and stable equipment carrier allowing a steady positioning. Three frames can be equipped with 1-2 nets each, having different mesh sizes exposed over the whole water column. The methodology was tested in the Austrian Danube River, showing a high heterogeneity of microplastic concentrations over the cross-section but also vertically over the depth. It was found that even higher amounts of plastic can be transported in a subsurface layer or even bottom-near.

Three-dimensional numerical modelling has proven to be a great support in describing and analyzing plastic particle transport in flowing waters. Flow fields near river engineering structures such as groynes and guiding walls were characterized by the models as they are known to be plastic accumulation zones. The models can be used for predicting potential accumulation zones in Danubian inundation areas and can provide recommendations for creating “artificial” accumulation zones where plastic can be more easily extracted from the river.

How to cite: Liedermann, M., Pessenlehner, S., Tritthart, M., Gmeiner, P., and Habersack, H.: Methods for measuring and modelling plastic transport and accumulation in large rivers, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10339, https://doi.org/10.5194/egusphere-egu2020-10339, 2020.

Rivers act as pathways to the ocean of significant but unquantified amounts of plastic pollution. Measuring with precision the quantities of riverine plastic inputs is crucial to support and ensure the effectiveness of prevention and mitigation waste management actions. However, there is a lack of technological tools capable of monitoring and, consequently, assessing accurately plastic abundances and its temporal variability through river water surfaces. Within the LIFE LEMA project, two videometry systems were installed at the river mouths of two European rivers  (Oria in Spain and Adour in France)  and a detection algorithm was developed  to monitor litter inputs in near real time . The objective of these developments was to detect riverine pollution at water surface, with the goal of quantifying the number and providing data on the travel speed and size of the floating items. Between 2018 and 2020, the system was tested under different environmental conditions. These tests have led to develop a second version of the algorithm that improves the results reducing false positives. After these improvements, a new validation has been carried out consisting in detailed analysis of more than 300 short videos of 5 minutes duration recorded in Orio’s station under different river flows, weather conditions and plastic loads. The validation results highlighted the operational reliability of the system. In a scale of 1 to 5 scoring (being 1 very bad and 5 very good) over 70% of the recordings scored 4 to 5. This also demonstrated the great potential of the videometry system in harmonizing visual observations of floating riverine litter. The data provided by the systems is currently being used in the LEMA TOOL, a tool designed to guide local authorities on managing, monitoring and forecasting marine litter presence and abundances in coastal waters of the SE Bay of Biscay. Furthermore, the data provided is key to evaluate the sources of the pollution and the efficiency of waste management measures within the river basins, towards a successful reduction of plastic inputs into the ocean.

How to cite: Ruiz, I., Barurko, O., Epelde, I., Liria, P., Rubio, A., Mader, J., and Delpey, M.: Monitoring floating riverine pollution by advanced technology, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22613, https://doi.org/10.5194/egusphere-egu2020-22613, 2020.

Plastic contamination in rivers quickly changes over time and space, driven by factors such as land use, urbanization and population density, climatic conditions and river hydrology. Understanding the patterns and mechanisms behind these fluctuations is of major importance to estimate and evaluate plastic loads and to forward management strategies and policies. During a 18-month sampling campaign (May 2018 to October 2019) in the Hillsborough River Tampa (USA), we studied how seasonality and urban pollution affected plastic loads transported through the river. We sampled monthly at three sampling sites, strategically located to assess the release of plastic through urban runoff from Tampa, covering two wet seasons and one dry season. At each site, we conducted stationary sampling with a 500-µm mesh neuston net at five different positions through the width and depth of the river. Using an Acoustic Doppler Current Profiler, we also collected comprehensive data on flow characteristics and accurately estimated river discharge during sampling events. All samples were processed in the laboratory with state-of-the-art methods to separate plastic particles from water samples. Plastic particles were classified by size categories and a subset was identified using Raman spectroscopy. Results of this study shows a strong correlation between plastic loads and rainfall seasonality. For instance, mean concentrations close to the mouth of the river varied from less than 1 count/m³ during the dry season (March-May) to up to 9 counts/m³ during wet months (September). Furthermore, there was a substantial increase in loads as the river passed through the city, mostly peaking at the farthest downstream site close to the river mouth; while median concentrations at the site upstream from the city were 0.21 counts/m³ (range of 0-1.68), median concentrations at the station close to the river mouth (in Downtown Tampa) were 1.16 counts/m³ (range of 0.14-21.61 counts/m³). During some months, however, loads were higher at the second site, located in the middle of a residential and commercial district. Differences in plastic loads along the river were explained by river flow accumulation and land use/land cover intensity, though small differences in concentrations between the middle site and the furthest downstream can be explained by differences in stormwater management practices between these two contrasting socioeconomic areas. This study generated a unique and comprehensive dataset on plastic loads and river hydrology on a watershed scale to evaluate drivers of plastic pollution and rivers as their pathway, providing a base for the development of management plans in urban rivers and solution strategies for plastic pollution in similar subtropical watersheds.

How to cite: Haberstroh, C. and Arias, M.: Seasonal and longitudinal patterns of plastic pollution in a subtropical urban river, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20888, https://doi.org/10.5194/egusphere-egu2020-20888, 2020.

Plastic pollution in the marine environment is an urgent global environmental challenge. Land-based plastics, emitted into the ocean through rivers, are believed to be the main source of marine plastic litter. According to the latest model-based estimates, most riverine plastics are emitted in Asia. However, the exact amount of global riverine plastic emission remains uncertain due to a severe lack of observation. Field-based studies are rare in numbers, focused on rivers in Europe and North America and used strongly varying data collection methods. We present a harmonized assessment of floating macroplastic transport from observations at 24 locations in rivers in seven countries in Europe and Asia. Visual counting and debris sampling were used to assess (1) magnitude of plastic transport, (2) the spatial distribution across the river width, and (3) the plastic polymer composition. Several waterways in Indonesia and Vietnam contain up to four orders of magnitude more plastic than waterways in Italy, France, and The Netherlands in terms of plastic items per hour. We present a first transcontinental overview of plastic transport, providing observational evidence that, for the sampled rivers, Asian rivers transport considerably more plastics towards the ocean. New insights are presented in the magnitude, composition, and spatiotemporal variation of riverine plastic debris. We emphasize the urgent need for more long-term monitoring efforts. Accurate data on riverine plastic debris are extremely important to improve global and local modeling approaches and to optimize prevention and collection strategies.

How to cite: van Calcar, C. and van Emmerik, T.: Abundance of plastic debris across European and Asian rivers, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-707, https://doi.org/10.5194/egusphere-egu2020-707, 2020.

Inadequate management of plastic waste has resulted in its ubiquity within the environment, and presents a risk to living organisms. Harm caused by large plastics is well documented, but progressive understanding of microplastics (< 5mm) reveals an ever more unsettling issue. Microplastics contamination is considered an emerging global multidisciplinary issue that would be aided by further research on sources, distribution, abundance, and transport mechanisms. Landfills are a suspected source of such, but research at these sites is insufficient. Although the risks surrounding microplastics are still inconclusive, there is concern over their accumulation in organisms, leaching constituents, and hydrophobic nature. Studying microplastics in the environment, let alone landfill, is challenging as standard and accepted methodologies are presently non-existent.

Here, microplastics (1mm to 25µm) were evaluated at one particular and long-running UK landfill after first developing a simple, replicable, efficient, and cost effective sampling and analysis approach. Concentrations and types of microplastics were quantified in raw leachate, treated leachate, waste water, groundwater, and surface water, to characterise abundance, distribution, and released loads to the environment. Samples were filtered in-situ, with subsequent purification at the laboratory by Fenton’s reagent. Analysis relied heavily on microscopic sorting and counting, but use of Scanning Electron Microscopy – Energy Dispersive X-Ray Spectroscopy enabled instrumental interrogation of particles suspected to be plastic. Many factors investigated here appear novel to the literature, and comprehensively explore: temporal variation of microplastics in raw leachate across different landfill phases and waste ages; their abundance in local groundwater, and surface water discharge; microplastics distribution within a leachate treatment plant; and their subsequent release to the environment from a waste water treatment facility. The results build upon the small collection of existing work, but also offer new insights into microplastics’ occurrence in, around, and released from a landfill site.

In total, 62 samples were taken, and particles considered microplastics (MP) were most abundant in groundwater, followed by raw leachate > waste water > treated leachate > surface water. Average concentration in groundwater was 105.1±104.3 MP L^-1, raw leachate 3.3±1.7 MP L^-1, and waste water was 1.8±0.73 MP L^-1. Consistent with other research, fibres were most dominant, but blank samples highlight the great potential for secondary contamination. Imaging of suspect particles revealed the extreme nature and conditions of landfill sites in their generation of microplastics. Analogous to waste water treatment, leachate treatment is shown to be reducing microplastics in the discharge by 58.1%, and it is expected that microplastics are retained in the treatment plant sludge. Daily loads from leachate treatment were 142,558±67,744 MP day^-1, but from waste water this was approximately 45.2±18.3 million MP day^-1. Ultimately, the landfill is not a final sink of microplastics but a source, for those >25 µm, to the environment: yet, it is unlikely to be a significant one. Results highlighted the need for reduction strategies at waste water treatment plants and in the site’s groundwater boreholes, as well as further investigation to determine the source of abundant fibres in the surface water.

How to cite: Waddell, M., Grassineau, N., Brakeley, J., and Clemitshaw, K.: Microplastics in a UK Landfill: Developing Methods and Assessing Concentrations in Leachate, Hydrogeology, and Release to the Environment, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-21579, https://doi.org/10.5194/egusphere-egu2020-21579, 2020.

River systems are major pathways for the transport of microplastic (MP). The Rhine is among the biggest river systems in regard to catchment size and discharge in northwestern Europe. Studies have documented the presence of MP in the Rhine and its tributaries along its course through Germany. The region of Cologne is densely populated, with a variety of land use forms occurring. Thus, an understanding of the presence and entry pathways of MP into alluvial meadows of the Rhine is important for risk assessments. 

This study aims to quantitively analyse transport pathways and sedimentation of MP into the alluvial meadows of the Rhine. We expect that the main entrance pathway of MP into these alluvial meadow soils is via fluvial transport. Two study sites were chosen in Cologne, one in the southern part of the central city (Poller Wiesen) and one in northern rural areas of the city (Merkenich-Langel). These sites were chosen as there are no agricultural fields in the direct vicinity, which could account for major MP input through surface runoff. The sites were flooded intermittently in the past with records of the water level during flooding and extent of flooded areas. For each site, sampling transects were chosen increasing in elevation and distance relative to the river water level. Samples were investigated for their MP concentrations via FTIR-spectroscopy. A digital elevation model supports the understanding of the water flow during flood events. Differences in MP concentrations with increasing elevation and distance to the river are thought to be caused by differences in intensity and frequency of flooding.

How to cite: Müller, K. L., Laermanns, H., Rolf, M., Steininger, F., Löder, M., Möller, J., and Bogner, C.: Microplastic input in to alluvial meadows of the Rhine river in Cologne, Germany, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8460, https://doi.org/10.5194/egusphere-egu2020-8460, 2020.

The large production of plastic material (PlasticsEurope, 2019), together with the mishandling of plastic waste, has resulted in ubiquitous plastic pollution, which now reaches even the most remote areas of the Earth (Allen et al., 2019; Bergmann et al., 2019). Plastics undergo a slow process of erosion in the environment that decreases their size: microplastics (MPs) and nanoplastics (NPs) have diameters between 1 µm and 5 mm and lower than 1 µm, respectively (Frias and Nash, 2019).

The occurrence, transformation and fate of MPs and NPs in the environment are still unclear. Therefore, the objective of this work is to better understand the reactivity of NPs using an aqueous suspension of polystyrene NPs (PS-NPs) as a proxy, in the presence of sunlight and chemicals oxidants. The results obtained are relevant to both the atmospheric aqueous phase, such as cloud and fog droplets, and surface waters. We investigated the reactivity of PS-NPs with light and with two important oxidants in the environment: ozone (O₃) and hydroxyl radicals (^•OH). The adsorption of ozone (O₃) on PS-NPs is investigated, showing a significant O₃ uptake. Moreover, for the first time, a reactivity constant with ^•OH is determined. We found a linear correlation between the kinetic constants measured for three different sizes of PS-NPs and the surface exposed by the particles. Degradation products (short chain carboxylic acids and aromatic compounds), obtained by direct and ^•OH-mediated photolysis of PS-NPs suspensions, are identified by high-resolution mass spectrometry. Irradiation of a PS-NPs suspension under natural sunlight for 1 year has shown the formation of formic acid and organic compounds similar to those found in riverine and cloud dissolved organic matter.

This work is crucial to assess the impact of NPs abiotic degradation in atmospheric and surface waters; indeed, the reactivity constant and the degradation products can be implemented in environmental models to estimate the contribution of NPs degradation to the natural dissolved organic matter in the aqueous phase. A preliminary simulation using APEX (Aqueous Photochemistry of Environmentally occurring Xenobiotics) (Bodrato and Vione, 2014) model shows that in NPs-polluted environments (10⁹ particles mL^-1) there is potential for NPs to significantly scavenge ^•OH, if the content of natural organic matter is not too high, as observed for surface and cloud water.

Allen, S., et al., 2019.  Nat. Geosci. 12, 339–344. https://doi.org/10.1038/s41561-019-0335-5
Bergmann, et al., 2019.  Sci. Adv. 5, eaax1157. https://doi.org/10.1126/sciadv.aax1157
Bodrato, M., Vione, D., 2014. Environ. Sci.: Processes Impacts 16, 732–740. https://doi.org/10.1039/C3EM00541K
Frias, J., Nash, R., 2019. Mar. Pollut. Bull. 138, 145–147. https://doi.org/10.1016/j.marpolbul.2018.11.022

How to cite: Bianco, A., Sordello, F., Ehn, M., Vione, D., and Passananti, M.: Degradation of nanoplastics in aquatic environments: reactivity and impact on dissolved organic carbon, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-5308, https://doi.org/10.5194/egusphere-egu2020-5308, 2020.

Since their first detection in the 1970s, microplastics have been a growing concern in public opinion. Although a large number of studies are interested in this contamination, the fate of microplastics in freshwater remains poorly understood. In particular, the identification of sources, the degradation processes of these compounds and their impacts on aquatic ecosystems constitute fields of research to be investigated. PLASTILAC is the first project focusing on the presence and fate of microplastics in 4 remote alpine lakes (Muzelle Lake, Vert Lake, Pormenaz Lake and Anterne Lake) that have been investigated during summer 2019. The aims of this study were to better understand the microplastic dynamics in small remote lake catchment and to quantify the impacts of various anthropic activities on the microplastic contamination.

The lakes were chosen to allow the comparison of the different transfer processes occurring at the catchment scale. Thus, the lakes of Muzelle and Anterne have similar sizes (about 10 000m²) and altitudes (about 2100 m a.s.l). These two lakes are isolated and have no direct access apart from several hour hikes. They are however separated by a distance of about 120 km. A comparison of their contamination levels therefore makes it possible to assess the background contamination at the scale of the Northern Alps. On the contrary, the Anterne, Pormenaz and Vert Lakes are very close but cover a wide gradient of altitude (from 1260 to 2100 m a.s.l.) and of exposure to anthropogenic activities. Their comparison allows us to study the influence of distance from potential sources on the microplastic contamination.

To investigate the dynamics of microplastics at the lake basin scale, a multi-compartment approach was implemented. The water column was sampled using a specially designed boat that allowed the filtration of the large volumes (approximately 200 cubic meters) of water required in lightly contaminated environments. The boat was equipped with a 50 µm mesh. A similar system was used to sample the lake outlets and determine the outflows of microplastics. In order to quantify the incoming flows, an atmospheric fallout collector was also installed. Finally, lake sediments were collected to quantify the fraction of microplastics eliminated from the water column through sedimentation. All of these data made it possible to establish a mass balance of microplastics at the scale of the watershed of lakes and to determine the characteristic times of contamination.

Although analyzes are still in progress, the first results show that even the most distant lakes from anthropogenic sources have significant microplastic contamination of the order of 1 particle per cubic meter. Due to the distance to the sources, the microplastic pollution was constituted fibers while fragments and micro-beads could not be observed. 

How to cite: Gateuille, D., Dusaucy, J., Gillet, F., Gaspéri, J., Dris, R., Tourreau, G., and Naffrechoux, E.: Microplastic contamination in remote alpine lakes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12924, https://doi.org/10.5194/egusphere-egu2020-12924, 2020.

Microplastics (<5 mm) are persistent environmental pollutants characterised by heterogeneous physico-chemical properties and a broad range of shapes, sizes, colours and composition. Microplastics may be directly released into the environment at this size (i.e. pellets and cosmetic microbeads) when they are known as primary microplastics. However, the majority of microplastics are secondary, i.e. they originate from the degradation of larger plastic items. An important source of secondary microplastics is represented by fibres released during washing of synthetic garments. Although microplastic contamination is thought to be ubiquitous in aquatic ecosystems, very little is known about the scale, the extent of inputs as well as rates of change in rivers and lakes. In particular lake sediments, may represent an important sink for microplastics as well as providing a means to assess historical trends.  

To assess microplastic abundance, distribution, historical records and composition in the sediments of UK urban and rural lakes, sediment cores have been collected at representative locations in two ponds on Hampstead Heath, in the Borough of Camden, London, and in three lakes in the Norfolk Broads National Park, in eastern England. Microplastics extracted from sediment cores have been identified, and variation in polymer-type analysed through sediment chronostratigraphy. Sediment chronologies can help quantify the historical flux of microplastics from terrestrial environments to freshwaters, reflecting changes in microplastic production over time.

To highlight seasonal fluxes and variations in microplastic distribution and abundance in the lakes examined, new-design sediment traps were built at UCL Geography Laboratories and anchored to the bottom of the study sites to collect material sinking from the water column. The traps are being monitored, emptied, cleaned and redeployed every three months over about a 2-year period.

This study presents the results about temporal distribution and seasonal fluxes of microplastics in sediments from Hampstead Heath ponds in London (urban sites) and from the Norfolk Broads National Park (rural sites). The identification of plastic polymers, together with the assessment of microplastic temporal distribution and seasonal patterns of accumulation in lakes will help identify factors influencing microplastic distribution and pollution sources for lakes. The results from this project will deliver a better understanding of the number and scale of sources of microplastics in urban and rural lakes, improving future risk assessments and prevention strategies.

How to cite: Bancone, C., Rose, P. N., and Francis, D. R.: Temporal distribution and seasonal fluxes of microplastics in the sediments of UK rural and urban lakes, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-19776, https://doi.org/10.5194/egusphere-egu2020-19776, 2020.

We used the systematic review procedure to assess the evidence available on the analysis, prevalence and impact of microplastics in freshwater and estuarine environments. As the study of microplastics in freshwaters is relatively new, measurement methods are yet to be standardized, and a wide variety of methods of variable robustness have been used. Critically, the sampling methodology used in the literature had a systematic influence on the concentration of microplastic particles returned. The volume of water sampled varied over many orders of magnitude, and there was a direct relationship between the size of the smallest particles studied and the volume of water sampled in both freshwater and estuaries: large volumes of water can only be sampled using nets of relatively coarse mesh, which in turn do not capture smaller particles. Consequently, the mean abundance of microplastic particles reported was inversely correlated with both the volume of water sampled and the size of particles studied.

The size of microplastic particles had a substantial and overriding effect on threshold concentrations above which microplastics affect freshwater and estuarine biota. For the ecotoxicological endpoints of feeding, behaviour, growth and survival there was a clear relationship between the size of the particles used in the test and the threshold concentration at which an effect was seen. Although the taxonomic coverage of test organisms was limited, there were sufficient data to test the influence of taxonomic group used on size-specific thresholds for Crustacea, fish and algae. There was no significant effect of either the endpoint measured or the taxonomic group used, suggesting that there might not be any difference in sensitivity among different taxa.

In order to establish a threshold concentration where microplastics present a hazard to a limited number of taxa, quantile regression was used to determine the size-specific concentration of microplastics that was lower than 90% of the thresholds identified for survival and, as a more conservative limit, across all endpoints tested including sublethal effects. By comparing these thresholds with the data on concentrations of microplastics reported by field studies, it was apparent that the calculated size specific threshold concentration for lethal effects was considerably higher than 99% of reported environmental concentrations. Lethal effects of microplastics on freshwater and estuarine biota are likely to be limited to exceptional circumstances. Over certain size ranges the calculated size specific threshold concentration for sublethal effects was exceeded by the highest 10% of concentrations reported from environmental samples, suggesting that there is a risk of sublethal effects in a small proportion of sites.

How to cite: Jones, J. I., Murphy, J. F., Arnold, A., Pretty, J. L., Spencer, K., Markus, A. A., and Vethaak, A. D.: Analysis, prevalence and impact of microplastics in freshwater and estuarine environments: an evidence review, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22468, https://doi.org/10.5194/egusphere-egu2020-22468, 2020.

The total production of plastics is estimated to be~ 10 billion metric tons, half of which is thought to have ended up as waste in the environment. However, the total mass of plastic found in the world’s ocean garbage patches has been calculated as less than 1 million metric tons, a paradox that leaves the whereabouts of the majority (>99.9%) of plastic waste produced so far unexplained.

Recent research suggests that the accumulation of plastic (in particular microplastic < 5mm in size) in river corridors may be even greater than that  in the world’s oceans. Our model-based quantifications reveal that rivers do not solely function as pure conduits for plastics travelling to the oceans, but also represent long-term sinks, with in particular microplastics being buried in streambeds and floodplain sediments. This includes the development of pronounced hotspots of long-term plastic accumulation, evidencing that these emerging pollutants have already developed a pollution legacy that will affect generations to come.

The principles that govern the spatially and temporally dynamic inputs of plastics into river corridors as well as the fate and transport mechanisms that explain how plastics are transported and where they accumulate are still poorly understood. Experimental evidence of microplastic pollution in river corridors is hampered by the absence of unified sampling, extraction and analysis approaches, inhibiting a comprehensive investigation of global source distributions and fate pathways. We have therefore initiated the 100 Plastic Rivers programme to provide a global baseline of microplastic pollution in rivers, their drivers and controls in order to develop mechanistic understanding of their fate and transport dynamics and create predictive capacity by informing the parameterisation of global plastic transport models. Preliminary results evidence the suitability of the 100 Plastic Rivers approach and help validate our predictions of global plastic storage in river corridors.

How to cite: Krause, S., Drummond, J., Nel, H., Gomez-Velez, J., Lynch, I., and Sambrook Smith, G.: River corridors as global hotspots of microplastic pollution, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3968, https://doi.org/10.5194/egusphere-egu2020-3968, 2020.

Plastic waste increasingly accumulates in the marine environment, but data on the distribution and quantification of riverine sources, required for development of effective mitigation, are limited. Our new model approach includes geographical distributed data on plastic waste, landuse, wind, precipitation and rivers and calculates the probability for plastic waste to reach a river and subsequently the ocean. This probabilistic approach highlights regions which are likely to emit plastic into the ocean. We calibrated our model using recent field observations and show that emissions are distributed over up to two orders of magnitude more rivers than previously thought. We estimate that over 1,000 rivers are accountable for 80% of global annual emissions which range between 0.8 – 2.7 million metric tons per year, with small urban rivers amongst the most polluting. This high-resolution data allows for focused development of mitigation strategies and technologies to reduce riverine plastic emissions.

How to cite: Meijer, L., van Emmerik, T., van der Ent, R., Lebreton, L., and Schmidt, C.: Over 1000 rivers accountable for 80% of global riverine plastic emissions into the ocean, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22000, https://doi.org/10.5194/egusphere-egu2020-22000, 2020.

Microplastics (MPs) have been found ubiquitously in oceanic and terrestrial environments.  As the production and consumption of plastic polymers increases the amount of plastic evading accepted disposal pathways and entering natural systems is also expected to increase. To date the focus of plastic and MP research in particular has been on the ocean, there has recently been a rapid increase in interest in MP levels and distribution in terrestrial systems. However, the focus of existing studies has mostly been on the quantification and distribution of MP contamination in the sediment or on the water column of rivers and lakes. The aim of this project is to investigate the fundamental physical and biological influences on the transport of microplastics (MPs) in lake systems. In particular, we will focus on an understanding of the migration and distribution of MPs, and a systematic investigation on transport and sedimentation of MP in the lake water column. Lab and field experiments are planned to investigate the behavior of different MPs polymers, shapes and sizes under different conditions and determine how this influence the MP transport.

The settling velocity of MPs in stationary water was measured in the laboratory using particle image velocimetry (PIV) which was then compared to manual timing of the sinking velocity. The trajectories of the settling MPs have also been tracked during weak turbulences. In addition, the results were compared with theoretical calculations.

To investigate microbial colonization and biofilm formation on the surface of MPs, samples were exposed on a natural lake environment for varying time periods. The colonization of MP surfaces by microorganisms and their excretion of extracellular polymeric substances (EPS) were examined by laser microscopic techniques and subsequently the effect of the microbiological colonization of settling velocity was determined. In this work we show that the transport of MP is complex, as it is influenced by plastic type, shape, and biological colonization as well as the hydrodynamic conditions in the lake water column.

How to cite: Elagami, H., Frei, S., Boos, J.-P., and Gilfedder, B.: Understanding the physical and biological controls on microplastic transport in lakes., EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2390, https://doi.org/10.5194/egusphere-egu2020-2390, 2020.

Although a major part of marine microplastic (MP) pollution originates from rivers and streams, the mechanistic behavior of MP in fluvial systems is only poorly understood. MP enter fluvial systems from e.g. waste water treatment plant (WWTP) effluents, sewer overflows during heavy rain events, agricultural runoff, aerial input/atmospheric fallout, road runoff or via fragmentation of plastic litter. As part of this project we want to investigate the hydrodynamic transport mechanisms that control the behavior and re-distribution of MP in open channel flow and the streambed sediments. Hydrodynamic conditions in open channel flow are represented in an experimental flume environment.  Different porous media materials (e.g. aqua beads, glass beads and sand) are used in the flume experiments to shape typical bed form structures such as riffle-pool sequences, ripples and dunes. The aim of this experimental setup is to create hydrodynamic flow conditions such as hydraulic jumps, low and high flow velocity environments for which the transport and sedimentation behavior of MP can be investigated under realistic conditions. Hydrodynamic flow conditions in the flume are characterized using a Laser-Doppler-Anemometry (LDA) and Particle Image Velocimetry (PIV). Detection and tracking of fluorescent MP-particles in open channel flow and in porous media will be achieved with a fluorescence-camera-system.

How to cite: Boos, J.-P., Gilfedder, B.-S., Elagami, H., and Frei, S.: An experimental investigation of microplastic transport in fluvial systems , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-3331, https://doi.org/10.5194/egusphere-egu2020-3331, 2020.

Plastic pollution proves a complex challenge, given the large variety in the properties of the items and particles. Usually, models and experiments focus on a small, sometimes arbitrary, subset of the total plastic continuum. This inherently implies a limitation, and will never be fully satisfactory if we are to understand the true behavior of plastic of all sizes, shapes and densities in the environment. Here, we present a novel approach, in which plastics are fully characterized by continuous distribution functions. For microplastics, we report and discuss distributions obtained for the marine and freshwater environment, from water and sediment samples. For macroplastics, we report spatial and temporal trends based on distributions that were derived from monitoring data from the OSPAR beach litter program. We discuss how these micro- and macroplastic distributions can feed directly into transport and fate models. Additionally, they can be used to design effect and fate experiments, where mixtures of (environmental) plastic should be used to better represent the real, complex mixture that plastic really is. By using this approach, the often acclaimed problem of complexity as a limiting factor is circumvented, which brings a true understanding of plastic fate and effects within reach.  

How to cite: Kooi, M. and Koelmans, A. A.: Understanding the plastic cocktail using distributions, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-6786, https://doi.org/10.5194/egusphere-egu2020-6786, 2020.

In recent years, there has been an increasing number of studies about freshwater micro-litter  and how it ends up in the ocean. Nevertheless, macro-litter studies are not common in freshwater landscapes and yet less frequent among rivers. Almost always, research is focused on estuaries rather than rivers.

The Asociación Paisaje Limpio has been developed, for some years, several studies as an affordable methodology to measure macro-litter in rivers throughout its.

This way, our methodology is a combination between research and action. We don’t just tackle the macro-litter data field, but also identify specific litter problems along the river. We act through campaigns, agreement for companies and public administrations, etc.

A need have been observed to combined different types of methodology to monitoring different types of rivers in order to be able to draw a conclusion:

• Visual counting: counting floating macro-litter on surface using RIMMEL app.
• By the riverbank,through a Citizen Science tool create by Asociación Paisaje Limpio and Asociación Vertidos Cero, called eLitter. Elitter is harmonized with other marine-litter methodologies (Marine litter watch, MARNOBA in Spain) and its litter classification is based on OSPAR protocol.
• If the riverbed is accessible eLitter is also used, but when is not accessible a dredge "Van Veen" have been used instead. This method has been applied in other marine-litter projects on seabed.
• Floating booms: it lets us know plastics rate in captured floating litter, and the water flow extrapolation.
• Nets from a kayak: to study the plastic concentration  in the water column and the water flow extrapolation.
• Water quality general analysis:this analysis is useful to support the hypothesis about litter’s source in a river, mainly where the source is the sewage as happens with wet wipes, ear sticks...

-Case study: river Lagares, a spanish river in Pontevedra, Galicia. The river Lagares flows into the Atlantic, in a Special Protection Area (SPA), a designation under the European Union Directive on the Conservation of Wild Birds.

The Asociación Paisaje Limpio is working on this river since 2018. We have applied the different methodologies explained before, in the river Lagares.

How to cite: Cabrera Fernández, M.: Freshwater pathways and litter , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7698, https://doi.org/10.5194/egusphere-egu2020-7698, 2020.

Plastic pollution in the aquatic environment has gained worldwide attention in the last years. Microplastics have been investigated for over 45 years especially in the marine environment, but only in the past years research has also started to focus on freshwater environments. In the frame of the project about macro- and microplastics in German rivers, samples from 11 sites from the German part of the river Elbe were taken in order to study the plastic pollution in water and sediment, detect sinks of microplastics and better understand transport mechanisms.

The sediment samples were taken with a Van-Veen-grabber, the water samples from the Elbe with an Apstein plankton net (mesh size 150 µm) from the same location. The sediment samples were presorted with wet sieving, organic digestion and density separation and filtered on aluminium oxide filters. For the water samples, the organic matter was digested using a reagent composed of equal volumes of 10 M KOH and 30 % H2O2, then, the microplastic particles were isolated from remaining matrix by density floatation using 1.6 g/mL potassium formate solution and pressure filtration. Analysis was done by visual inspection, selected particles measured with Fourier-transform infrared spectroscopy and masses calculated with a pyrolysis GC-MS.

The results of the sediments of the Elbe reveal that tentative microplastic concentrations differed intensively between the different river compartments. Microplastics in the sediments were in average 600,000-fold higher than in the water samples (when referring to the same volume). The amount of particles also varies significantly between the sampling sites. In sediment samples, microplastic concentrations decreased downstream, in water samples, concentrations varied stronger. The form of the particles is also site specific. In two samples, more than 80% spheres were counted whereas the 6 locations downstream reveal an increase in fragments. Polymer distribution differed between the water and sediment phase with mostly PE and PP in the water samples and a more diverse distribution in the sediments.

How to cite: Stock, F., Weber, A., Scherer, C., Kochleus, C., Dierkes, G., Wagner, M., Brennholt, N., and Reifferscheid, G.: Abundance and distribution of microplastics in water and sediments of the river Elbe, Germany, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8051, https://doi.org/10.5194/egusphere-egu2020-8051, 2020.

The majority of marine plastic pollution originates from land-based sources with the dominant transport agent being riverine. Despite many of the potential ecotoxicological consequences of plastics being well known, research has only just recently begun to explore the source to sink dynamics of plastics in the environment. Despite the widespread recognition that rivers dominate the global flux of plastics to the ocean, there is a key knowledge gap regarding the nature of the flux, the behaviour of microplastics (<5mm) in transport and its pathways from rivers into the ocean. Additionally, little is presently known about the role of biota in the transport of microplastics through processes such as biofilm formation and how this influences microplastic fate. This prevents progress in understanding microplastic fate and hotspot formation, as well as curtailing the evolution of effective mitigation and policy measures.

As part of the National Geographic Rivers of Plastic project, a combined-laboratory and field investigation was conducted. Fieldwork was undertaken in the Mekong River, one of the top global contributors to marine plastic pollution with an estimated 37,000 tonnes of plastic being discharged from the Mekong Delta each year. This flux is set to grow significantly in accordance with the projected population increase in the basin. The results presented herein outline a suite of laboratory experiments that explore the role of biofilms on the generation of microplastic flocs and the impact on buoyancy and settling velocities. Aligned fieldwork details the particulate flux and transport of microplastic, throughout the vertical velocity profile, across the river-delta-coast system, including the Tonle Sap Lake. The results also highlight potential areas of highest ecological risk related to the dispersal and distribution of microplastics. Finally, pilot data on the levels of microplastics within fish from the Mekong system are also quantified to explore the potential impact of biological uptake on the fate and sinks of plastics within the system.

How to cite: Mendrik, F., Parsons, D., Hackney, C., Waller, C., Cumming, V., Dorrell, R., and Vasilopoulos, G.: Controls on microplastic flux mechanisms in a large river , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8116, https://doi.org/10.5194/egusphere-egu2020-8116, 2020.

Riverine plastics cause severe global problems, regarding the risk for human health and environmental damage. The major part of the plastic waste that ends up in the oceans is transported via rivers. However, estimations of global quantities of plastics entering the oceans are associated with great uncertainties due to methodological difficulties to accurately quantify land-based plastic fluxes into the ocean. Yet, there are no standard methods to determine quantities of plastics in rivers. For the sake of reducing the amount of plastic waste in the natural environment, information on plastic fluxes from rivers to seas is needed. Focussing on monitoring of the plastic litter that is transported by rivers is useful because measures can easier be implemented in rivers than in seas. Moreover, consistent measuring techniques are crucial to optimise prevention-and mitigation strategies, especially in countries with high expected river plastic emissions.

Additionally, based on plastic characteristics and turbulent river flow conditions, a considerable portion of the riverine litter can also be transported underneath the surface in the water column. Current monitoring methods regarding macro plastics are labour intensive and do not provide continuous measurements for submerged riverine plastics. Besides, most research done focussed on floating macro litter, instead of submerged plastics. The aim of this research was to find a standard method, applicable in different river systems, for detecting submerged macro plastics.

With the use of the Deeper Chirp+ fishfinder, several tests were conducted both in the Guadalete river basin in southern Spain and in the lab at the TU Delft. Spanish, and in general European rivers are estimated to transport two to three orders of magnitude below rivers in Asia (Malesia and Vietnam), and should not be neglected. The Guadalete river basin formed a suitable location to test this new method. First, monitoring in the Guadalquivir river was executed, with the use of a net to validate the readings of the sonar. Furthermore, the detecting abilities of the echosounder, in the Guadalete river basin, were tested with the use of plastic targets. The targets were released in the river and passed the sensor at a certain time. Moreover, tests in the lab at the TU Delft were conducted to investigate relations between sonar signal and flow velocity, object depth, and object size.

The tests show that submerged macro plastics can be detected with the use of echo sounding. Moreover, a relation between the sonar signal and litter size is found. Finally, signal intensities can be related to object properties. In conclusion, the use of echo sounding has a high potential for obtaining more accurate plastic flux estimations.

How to cite: Broere, S., van Emmerik, T., González-Fernández, D., Luxemburg, W., Cózar, A., van de Giesen, N., and de Schipper, M.: Monitoring submerged riverine macroplastics using echo sounding , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-8321, https://doi.org/10.5194/egusphere-egu2020-8321, 2020.

Microplastic burden in aquatic environments is now recognised as a potential threat to human and environmental health.  Although microplastic transfers to the ocean from the terrestrial river network contributes up to 90% of the plastics in the oceans the factors controlling that transfer remain largely unconstrained. In rivers microplastics are stored within sediment beds and whilst they are there both the microplastic particles and the sediment grains can become colonised by biofilms.  Biofilm growth on river sediments has been shown to increase a particles resistance to entrainment but the effects of such biostabilisation on microplastic flux has not yet been considered.  This is despite the fact that biofilm growth can change the buoyancy, surface characteristics and aggregation properties of the plastic particles  such as to cause them to be deposited rather than transported and hence increase their residence time.

In order to quantify biostabilisation processes on microplastic flux a two stage experimental programme was run.  During the first stage, bricks were submerged in a gravel-bed stream and biofilms allowed to colonise the bricks for 4 weeks.  The biofilm covered bricks were then extracted and placed within a re-circulating ‘incubator’ flume which had been divided into 9 smaller channels.  Within each of the 9 channels either a uniform sand, uniform gravel or a bimodal gravel mix were placed in Perspex boxes in the flume channels.  Each sediment type was seeded with either high density PVC microplastic nurdles (D₅₀ of 3mm, density of 1.33g/cm³) or polyester fibres (5 mm long, 0.5-1 mm wide, density of 1.38 g cm³), both at a concentration of 1%.  Blanks were also run where the sediment mixtures did not contain any micropalstics.  The flume was left to run with representative day/night cycles of lighting in order to let the biofilms colonise the test sediments for either 0 (control), 2, 4 or 6 weeks.  At the end of the chosen colonisation periods the persepx boxes containing the sediment were removed from the incubator flume and placed within a glass-sided, flow-recirculating flume (8.2m x 0.6m x 0.5m); this constituted the second stage of the experiment. During this stage the samples were exposed to a series of flow steps of increasing discharge designed to establish the entrainment threshold of the D₅₀ sediment grains. Entrainment thresholds were calculated for each of the growth stages such as to establish the effect of biostabilisation on sediment and microplastic flux.  Bedload and microplastic transport rates were also measured at every flow step to establish biostabilisation effects on overall fluxes. Finally, photographs of the sediment surface were taken at each flow step in order to estimate the percentage loss of biofilm from the surface. 

Discussion concentrates on linking the changes in the degree of biofilm colonisation with the entrainment threshold of the sediment and the links between biofilm colonisation and the character of the bedload and microplastic flux.   The outcome of this research is pertinent to developing understanding surrounding the role biostabilisation has to play in the residence times of microplastics within fluvial systems.

How to cite: Fourie, P., Ockelford, A., and Ebdon, J.: The role of biostabilisation in controlling microplastic flux in rivers, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10816, https://doi.org/10.5194/egusphere-egu2020-10816, 2020.

The rising concern over plastic pollution has spiked the number of studies being undertaken globally in a large variety of environments. Microplastic studies have only recently started and there is still so much unknown. One important question to answer is how do different microplastics behave during degradation and how fast does it happen.

In this study, a range of plastic waste was tested in both tap water (fresh water conditions) and salt water (marine conditions) to observe if the water chemistry and timescale plays a significant role in degradation. The samples were exposed to natural weathering and UV light for up to 3 months and then checked for variation including their change of weight. The aim of the study was to determine if different types of plastic waste degrade differently combined with the impact of varying lengths of exposure and water medium. Following this, to reconstitute the natural aquatic environment, the samples were placed in water on a shaking table for 24 hours, and observations were made to assess their propensity for degradation.

Although the time scale was short, different degrees of degradation occurred between each type of plastic studied, with some samples losing significant mass, some none and some gaining mass. As expected, the low density plastics showed very quickly visible signs of decay, and some fragmentations, and therefore this indicates that they are quickly becoming available for small organisms at the bottom of the food chain.  In opposition, hard plastics are more resistant with little degradation or none. However this study highlights specific issues with the media in which the plastics are found, particularly in the marine environment, where some harder materials become “encrusted” with sea salt, increasing their density. This means that by slowly sinking within the marine water column, they become available to all marine fauna, not just at the surface.

Although all microplastic particles require attention, the most common and abundant type found in fresh waters are synthetic fibres, with their source likely to be from washing machine effluent and sewage treatment.  Following the findings above, the focus of the study turned to non-natural fibres by exploring the comparisons between water pollution from general household laundry and industrial manufacture of synthetic textiles. Methods involving collecting effluent from washing machines and industrial manufacturing machines have been tested and the resulting samples digested with hydrogen peroxide. This study shows evidence of great losses of synthetic fibres from garments, at industrial scale as well as household level. This highlights the pressing issues that urban areas need to face with current waste water management to increase recycling and the capture of microplastics.

How to cite: Rossouw, S., Grassineau, N., and Brakeley, J.: Behaviour of different micro-plastics during degradation in fresh and sea waters, with focus on synthetic microfibers, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-12942, https://doi.org/10.5194/egusphere-egu2020-12942, 2020.

Plastic pollution in the marine and terrestrial environments is ubiquitous and a widespread problem. While the occurrence of plastics and microplastics, as well as their effects on marine and freshwater organisms, have already been investigated in numerous studies, so far only little attention has been paid to the fate, transport, and transformation processes of microplastics in the environment. In this work, the aggregation behavior of polystyrene (PS) microplastics in the presence of ferrihydrite, a natural inorganic colloid, was studied using zeta potential and hydrodynamic diameter measurements, as well as scanning electron microscope (SEM) techniques, considering the influence of pH and ionic strength. An increase of pH led to a more negative surface charge of PS. Furthermore, increasing concentrations of NaCl and CaCl₂ showed that mono- and divalent cations influence the zeta potential in a different way. Divalent ions compress the electric double layer more efficiently compared to monovalent ions, which resulted in a decrease of repulsive forces. Studies on the heteroaggregation between PS and ferrihydrite showed that the highest aggregation took place at neutral pH values. Aggregate sizes in samples with neutral pH increased significantly compared to more acidic and alkaline pH values. Furthermore, the results indicated that at neutral pH values, ferrihydrite completely covers the PS surface. SEM images and hydrodynamic diameter measurements revealed that the heteroaggregation between PS and ferrihydrite increased with ionic strength. Our results demonstrate that the fate of microplastic particles in aquatic systems can be strongly influenced by natural colloidal water constituents, such as iron hydroxides.

How to cite: Schmidtmann, J., Papastavrou, G., Helfricht, N., and Peiffer, S.: Heteroaggregation of micro-polystyrene in the presence of amorphous iron hydroxide (ferrihydrite), EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-14509, https://doi.org/10.5194/egusphere-egu2020-14509, 2020.

Microplastics (MPs) are being detected in aquatic environments worldwide, including seawaters and freshwaters. Moreover, some scarce studies have also reported the presence of MPs in potable water, both in water from public water supply and in bottled water. Despite any potential adverse effects on human health are not known yet, the occurrence of MPs in drinking water raises considerable attention. Drinking water treatment plants (DWTPs) pose a barrier for MPs to pass from raw water to treated water intended for human consumption; thus, the fate of MPs entering DWTPs is of a great interest. In order to encapsulate current knowledge in this regard, and so as to identify research needs in this filed, more than 100 studies were reviewed to provide concise conclusions. Focus was laid on: (i) summarizing available information on MP abundance and character in water resources and in drinking water; (ii) combining research results on MP contents at the inflow and outflow of DWTPs and on MP removal by distinct treatment technologies; (iii) comparing MPs to other common pollutants, the removal of which is commonly addressed at DWTPs; and (iv) providing an insight into the fate of MPs at waste water treatment plants (WWTPs), that act as a barrier for transition of MPs from waste to the nature, thus, have an “opposite” position than DWTPs. Additionally, the topic of (v) fate of MPs in DWTP and WWTP sludge was also put forward. This review brings together valuable information regarding the MP occurrence, character, and fate in freshwater aquatic environments in relation to the MP appearance at water treatment facilities, i.e. DWTPs and WWTPs, that may act as both sink and source of this emerging pollutant. Thus, the “cycle” of MPs between natural water bodies and “water in use by humans” is proposed.

How to cite: Novotna, K., Cermakova, L., Pivokonska, L., and Pivokonsky, M.: Properties and fate of microplastics entering drinking water treatment plants, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-14666, https://doi.org/10.5194/egusphere-egu2020-14666, 2020.

Excess of plastic debris in the environment is a worldwide problem. The origin of the plastic sources is partly land-based, the function of rivers as transportation pathways for plastics is an emerging research field. However, the transportation dynamics of macroplastic in river systems are still poorly understood(Blettler et al., 2018; Schmidt et al., 2017). By studying the interaction of riverine plastic transport and water plants, the transport dynamics can be better understood, which might help with the mitigation of the environmental plastic debris problem. 

A field study based in the Saigon river, Vietnam, found a correlation between macroplastic(>5 cm) abundance and organic material, where no other correlations were found(van Emmerik et al., 2019). We hypothesize that water hyacinths have an important role in the spatiotemporal dynamics of riverine macroplastic transport. The organic material in this river was predominantly identified as water hyacinths, an invasive plant common in Southeast Asia. In this study, we developed a method using image analysis, to detect macro plastics and floating vegetation(lab-grown water hyacinths). Image analysis in combination with drone technology creates opportunities to collect field data, with already promising results(Geraeds et al., 2019). We analyzed the images, to obtain an approximation of the amount of plastic and vegetation, visible from the surface. We subsequently use this data to evaluate the relationship between plastic abundance and vegetation in rivers. The method developed in this study can be used to collect data in the field. Targeted observations of plastic entrapment in water hyacinths may shed additional light on the potential of using water hyacinths as a proxy for riverine macroplastic transport dynamics. 

References

M. C. Blettler, E. Abrial, F. R. Khan, N. Sivri, and L. A. Espinola. Freshwater plastic pollution:Recognizing research biases and identifying knowledge gaps. Water research, 143:416-424, 2018.

M. Geraeds, T. van Emmerik, R. de Vries, and M. S. bin Ab Razak. Riverine plastic litter monitoring using unmanned aerial vehicles (uavs). Remote Sensing, 11(17):2045, 2019.

C. Schmidt, T. Krauth, and S.Wagner. Export of plastic debris by rivers into the sea. Environmental science & technology, 51(21):12246-12253, 2017.

T. van Emmerik, E. Strady, T.-C. Kieu-Le, L. Nguyen, and N. Gratoit. Seasonality of riverine macroplastic transport. Nature Scientific Reports, 2019.

How to cite: Castrop, E., van Emmerik, T., van den Berg, S., Kosten, S., Strady, E., and Kieu-Le, T.-C.: Plants, plastic and rivers: Do water hyacinths play a role in riverine macroplastic transport?, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-15198, https://doi.org/10.5194/egusphere-egu2020-15198, 2020.

The frequent urban floods in Jakarta and Bandung, Indonesia affect the lives and livelihoods of millions of people. Floods cause damage and casualties, while climate change, unchecked development and land subsidence are worsening the problem. One factor contributing to these floods is floating debris clogging the city's drainage structures. A major proportion of floating debris consists of macro plastics which are extremely persistent in the environment. Trash racks that are clogged due to continuous accumulation of plastics in front of them can block the water flow in the river, leading to an increase in upstream water level and causing floods. 

The understanding of transport and accumulation of the macro plastics in the river systems is limited as the field surveys are difficult to perform and the variety of properties of plastic debris is enormous. However, understanding of the origin, fate and pathway of plastic waste is required in order to come up with an optimal solution for plastic collection and prevention of harmful accumulation in front of the hydraulic structures. With this urge in mind field observations will be conducted on the selected river sections in Bandung and Jakarta during the monsoon season in 2020. Field observations will include the measurements of bathymetry, velocity profiles, concentrations and the characterization of floating debris, as well as identifying the accumulation hot spots of floating debris. Furthermore, experimental and numerical modelling will be performed based on the data collected during the field campaign in order to couple different debris classes to a range of riverine situations and understand the differences in their driving mechanisms.

Using a combination of field measurements, experimental modelling and empirical relations we aim to investigate the driving mechanisms of riverine plastic transport and changes in hydraulic properties due to local disturbances of the current. We will therefore link the type of hydraulic structures and the extend of obstructions due to accumulation of plastic debris to the changes in the upstream water level. This will lead to a better understanding of plastic transport in the river systems in Bandung and Jakarta, to formulate design criteria for structures in trash-laden streams and devise ways to pass trash during floods.

How to cite: Bertoncelj, V., Uijttewaal, W., Farid, M., and Bricker, J.: Fluid mechanics of plastic debris clogging the hydraulic structures in Indonesia, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17389, https://doi.org/10.5194/egusphere-egu2020-17389, 2020.

Microplastics are reported from wide range of aquatic environments with concentrations up to thousands of particles per kilogram of sediment. Due to a lack of temporal control, evaluation of the influx rate of microplastic pollution is not enabled. However, understanding the annual flux rate of microplastics to the aquatic environments is a crucial aspect for environmental monitoring and for risk assessment. A sediment trap method is widely applied in aquatic sedimentary studies in order to measure sedimentation rates and understand sedimentation processes. We have tested near-bottom sediment trap method in lacustrine and estuary environments, at central and coastal Finland, for measuring and quantifying the microplastic influx rate during one year. Near-bottom sediment traps with two collector tubes and known surface area, fixed one meter from the bottom, collect all particles that are about to accumulate on the basin floor of the water body. Controlled temporal interval of trap maintenance enables calculation and determination of local microplastic influx rate i.e. number of accumulating particles per time per surface area. The test results are very promising.  Near-bottom sediment traps can be used for long term monitoring in order to gain a deeper understanding of the microplastic transport and sedimentation processes, confirm and compare the feasibility and efficiency of different environmental conservation methods, setting threshold values for microplastic influx, and supervising that the defined target conditions are met.

How to cite: Saarni, S., Hartikainen, S., Uurasjärvi, E., Meronen, S., Hänninen, J., Kalliokoski, M., and Koistinen, A.: Sediment trapping as a method for monitoring microplastic flux rates and deposition at aquatic environments , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-18444, https://doi.org/10.5194/egusphere-egu2020-18444, 2020.

Plastic pollution has now been found across the Earth’s active zone, with recent studies finding plastics in remote parts of the Pacific Ocean, in deep ocean trenches, and in the high Arctic. Of particular concern are microplastics (<5mm diameter), these can be ingested by organisms where they have been shown to cause both chronic and acute health problems. In order to address plastic pollution there is a need to understand how plastic in the oceans is linked to terrestrial sources. Recent conceptual models have illustrated that plastic pollution is a complex interlinked problem with myriad sources and pathways introducing and redistributing plastic around the environment. Terrestrial and freshwater sources are likely to be significant contributors to overall plastic pollution; however, to date they remain poorly understood or quantified. There is a need to both identify and quantify sources of microplastic pollution in terrestrial and freshwater environments, as well as vectors which lead to the redistribution and storage of microplastics in hotspots of accumulation.

In this study we present pilot data attempting to characterise the influence of Waste Water Treatment (WWT) processes on environmental plastic pollution. Using the concept of the “Plastic Cycle” we identify various pathways for plastics present in domestic waste water to enter the environment after treatment. Using two study areas in the UK, we quantify the microplastic loading to the environment from WWT effluent, which is discharged to freshwaters, and from WWT sludge, which is spread on agricultural land as fertiliser. Our results show that both effluent and sludge are important sources of microplastics to the environment. However, these can be of the same order of magnitude as other sources indicating that addressing environmental microplastic pollution is likely to need an integrated approach. Our results also show these sources have lower loadings at some of our sites than reported in other studies, this indicates both treatment processes in WWT and management practices in sludge spreading are likely to be important in determining environmental loading of microplastics at specific sites. The influence of waste water treatment as a source of microplastic pollution needs to be further constrained, but our pilot data indicates a complex picture which needs to be better understood in order to inform environmental governance.

How to cite: Dixon, S., Trusler, M., and Kiernan, C.: Waste water treatment as a source of microplastic pollution, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20263, https://doi.org/10.5194/egusphere-egu2020-20263, 2020.

Rapid increasing production and utilization of microplastics (MPs) raise concerns about environmental risks globally. Literature indicates that wastewater and wastewater treatment plants (WWTPs) play critical sources in releasing MPs to the environment. Among different MPs, microbeads added into the facial cleanser, and toothpaste can be directly discharged into wastewater through human activities. Synthetic clothing, i.e., polyester (PES) and nylon, might shed thousands of fibers into wastewater during the washing process. WWTPs are not designed to capture MPs, and therefore, a huge amount of MPs load can be discharged without or poor treatment, and can accumulate in aquatic environments. This work shows a comprehensive overview of available information on the presence of MPs in different freshwater environments, particularly rivers, along with MPs types, sizes, shapes, and properties. Moreover, the study also indicates significant technical advancement in MPs detection, characterization, and quantification from the complex sample matrix.

How to cite: Adyel, T. M.: Wastewater as a potential source of microplastics in aquatic environments , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-20643, https://doi.org/10.5194/egusphere-egu2020-20643, 2020.

Macroplastic (>0.5 cm) pollution in aquatic environments is an emerging environmental risk, as it negatively impacts ecosystems, endangers aquatic species, and causes economic damage. Rivers are known to play a crucial role in transporting land-based plastic waste into the world’s oceans. However, rivers and their ecosystems are also directly affected by plastic pollution. To better quantify global plastic pollution pathways and to effectively reduce sources and risks, a thorough understanding of riverine macroplastic sources, transport, fate and effects is crucial. In our presentation, we discuss the current scientific state on macroplastic in rivers and evaluate existing knowledge gaps. We discuss the origin and fate of riverine plastics, including processes and factors influencing macroplastic transport and its spatiotemporal variation. Moreover, we present an overview of monitoring and modeling efforts to characterize riverine plastic transport and give examples of typical values from around the world (van Emmerik & Schwarz, 2020). With our presentation, we aim to present a comprehensive overview of riverine macroplastic research to date and suggest multiple ways forward for future research.

References

van Emmerik, T, Schwarz, A. Plastic debris in rivers. WIREs Water. 2020; 7:e1398. https://doi.org/10.1002/wat2.1398

How to cite: van Emmerik, T. and Schwarz, A.: Riverine Macroplastics and How to Find Them, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11840, https://doi.org/10.5194/egusphere-egu2020-11840, 2020.

Most marine litter pollution is assumed to originate from land-based sources, entering the marine environment through rivers. To better understand and quantify the risk that plastic pollution poses on aquatic ecosystems, and to develop effective prevention and mitigation methods, a better understanding of riverine plastic transport is needed. To achieve this, quantification of riverine plastic transport is crucial. Here, we demonstrate how established methods can be combined to provide a rapid and cost-effective characterization and quantification of floating macroplastic transport in the River Rhine We combine visual observations with passive sampling to arrive at a first-order estimate of macroplastic transport, both in number (10 - 75 items per hour) and mass per unit of time (1.3 – 9.7 kg per day). Additionally, our assessment gives insight in the most abundant macroplastic polymer types the downstream reach of the River Rhine. Furthermore, we explore the spatial and temporal variation of plastic transport within the river, and discuss the benefits and drawbacks of current sampling methods. Finally, we present an outlook for future monitoring of major rivers, including several suggestions on how to expand the rapid assessment presented in this paper.

How to cite: Vriend, P., van Emmerik, T., van Calcar, C., Kooi, M., Landman, H., and Pikaar, R.: Rapid assessment of floating macroplastic transport in the Rhine, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-698, https://doi.org/10.5194/egusphere-egu2020-698, 2020.

Plastic pollution of aquatic ecosystems is an emerging environmental risk. Land-based plastics are considered the main source of plastic litter in the world’s oceans. Quantifying the emission from rivers into the oceans is crucial to optimize prevention, mitigation and cleanup strategies. Although several studies have focused on estimating annual plastic emission based on average hydrology, the role of extreme events remains underexplored. Recent work has demonstrated that floods can mobilize additional plastics. For example, the 2015/2016 UK floods resulted in a 70% decrease of microplastic sediments in several catchments. In this project, the use of the Global Flood Awareness System (GloFAS) flood forecasting system to assess additional mobilization of plastic pollution will be explored.

How to cite: Roebroek, J., Harrigan, S., and van Emmerik, T.: Forecasting plastic mobilization during extreme hydrological events, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22384, https://doi.org/10.5194/egusphere-egu2020-22384, 2020.

Plastic debris in aquatic environments is an emerging environmental hazard. Macroplastic pollution (>5 cm) negatively impacts aquatic life and threatens human livelihood, on land, in oceans and within river systems. Reliable information of the origin, fate and pathways of plastic through river systems are required to optimize prevention, mitigation and reduction strategies. Yet, accurate and long-term data on plastic transport are still lacking. Current macroplastic monitoring strategies involve labor intensive sampling methods, require investment in infrastructure. As a result, these measurements have a low temporal resolution and are available for only a few locations. Crowd-based observations of riverine macroplastic pollution may offer a way for more frequent cost-effective data collection over an extensive geographical range. In this presentation we demonstrate the potential of crowd-based observations of  floating plastic and plastic on riverbanks. We extended the existing CrowdWater smartphone app for hydrological observations with a module for plastic observations in rivers. We analyzed data from two cases: (1) floating plastic in the River Klang, Malaysia, and (2) plastic the banks of the River Rhine in The Netherlands. Crowd-based observations of floating plastic yield similar estimates of plastic transport, distribution of plastic across the river width, and polymer composition as reference observations. The riverbank observations provided the first data of plastic pollution on the most downstream stretches of the Rhine, revealing peaks close to urban areas and an increasing plastic density towards the river mouth. With this presentation we aim to highlight the important role that crowd-based observations of macroplastic pollution in river systems can play in future monitoring strategies to provide complementing data of plastic transport composition at a higher spatial and temporal resolution than is possible with standard methods.

How to cite: Strobl, B., van Emmerik, T., Seibert, J., Etter, S., den Oudendammer, T., Rutten, M., and van Meerveld, I.: Crowd-based observations of riverine macroplastic pollution, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22406, https://doi.org/10.5194/egusphere-egu2020-22406, 2020.

Microplastics are an ever-increasing problem. Every river that was tested in a recent study found the presence of microplastics, with 80% of all plastic in the ocean coming from upstream. Despite this, there is little understanding into the abundance of plastic, its characteristics and the full impact that is it having on marine, freshwater ecosystems and wider ecological systems.

Current fresh water monitoring does not consider the fluid dynamics of rivers, is difficult to use and is inaccessible to the wider public. My project will focus on creating a product that allows for the large-scale data collection of microplastic through citizen science. Allowing groups of people to analyse their local natural environment for the presence and abundance of microplastics within the water. This method of data collection could provide information on a scale that is not possible with traditional methods and would allow for the comparison between freshwater systems. This comparison is fundamental to begin to fill the knowledge gaps around the understanding of microplastics.

Inaccessibility of monitoring to the public is not just through tools but also through the current communication of data with research rarely breaking into the public domain. Citizen science offers not just an improvement in understanding but also offers an opportunity for engagement with the public body. Increasing awareness of the impact of habits round plastic through the sharing of monitoring data can generate the much-needed change on both an individual and policy level to address the problem from the source. This method of change through public opinion can be seen to have an effect on freshwater systems through microbeads ban, plastic bags, plastic straws and industrial pollution regulation.

Through the creation of this product a multidisciplinary approach that blends engineering and design practices is implemented. The wholistic approach to creation is something that is fundamental in the success of tools and therefore the success of the research that is implemented through them. A tool such as this whose function is within the public engagement of its use - increased awareness, as well as the outcome of its use - microplastics data, is required to have an engaging user experience as well as data integrity implemented through engineering design.

This project offers an opportunity to show the importance of the design process within research tools to aid the research process and the positive impact that can come from it.

How to cite: Hughson-Gill, R.: Design of Microplastics Citizen Science Kit, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-9176, https://doi.org/10.5194/egusphere-egu2020-9176, 2020.

Several studies have documented high concentration of microplastics on fresh water sources, oceans and even on treated tap and bottled water. Understanding the physics behind these particles in the water environment has become one of the key research needs identified in the World Health Organization Report (2019). In order to develop novel and efficient methodologies for sampling, treating and removing microplastics from water bodies, a thorough understanding of the sources and transportation and storage mechanisms of these particles is required.

In this article, the settlement velocity affecting the transport [1, 2] of low-density particles (1<r<1.4 g.cm^-3) and drag coefficients is assessed through numerical modelling. The effects of fluid and particle relative densities and media temperatures are analysed, as well as the impact of the particle size and shapes [3].

Computational Fluid Dynamics (CFD) techniques are applied to solve the fluid dynamics while the Discrete Element Method (DEM) approach is used to model the particle trajectories [4]. These two modules are coupled under the CFDEM module, which transmits the forces from the fluid into the particle and from the particle into the surrounding water through the Fictitious Boundary Method approach.

Several tests are run under the same particle conditions in order to estimate the influence of turbulent flows on these experiments. The influence from different particle densities and diameters on settling velocities and drag coefficients is assessed. The numerical results are validated against a wide range of experimental data [2, 3] and compared against empirical predictions.

There is an urge for gaining a better understanding of the sources and transport of microplastics through fresh water bodies. In this sense, sampling and quantification of microplastics in a drinking water source is key to evaluate the environment status and to design the most appropriate techniques to reduce or remove the microplastics from the aquatic environments. The implementation of coupled CFD-DEM models provides a very powerful tool for the understanding and prediction of the transport processes and the accumulation of microplastics along the fluvial vectors.

References

[1] Valyrakis M., Diplas P. and Dancey C.L. 2013. Entrainment of coarse particles in turbulent flows: An energy approach. J. Geophys. Res. Earth Surf., Vol. 118, No. 1., pp 42- 53, doi:340210.1029/2012JF002354.

[2] Valyrakis, M., Farhadi, H. 2017. Investigating coarse sediment particles transport using PTV and “smart-pebbles” instrumented with inertial sensors, EGU General Assembly 2017, Vienna, Austria, 23-28 April 2017, id. 9980.

[3] Valyrakis, M., J. Kh. Al-Hinai, D. Liu (2018), Transport of floating plastics along a channel with a vegetated riverbank, 12th International Symposium on Ecohydraulics, Tokyo, Japan, August 19-24, 2018, a11_2705647.

[4] Valyrakis M., P. Diplas, C.L. Dancey, and A.O. Celik. 2008. Investigation of evolution of gravel river bed microforms using a simplified Discrete Particle Model, International Conference on Fluvial Hydraulics River Flow 2008, Ismir, Turkey, 03-05 September 2008, 10p.

How to cite: Jérémy, R., Pablo Gaston, L., and Valyrakis, M.: Coupled CFD-DEM modelling to assess settlement velocity and drag coefficient of microplastics , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-10049, https://doi.org/10.5194/egusphere-egu2020-10049, 2020.

Philippines is considered as one of the top contributors of plastic wastes in the oceans globally. Lack of strict implementation of solid waste management regulations has led to mismanaged wastes, especially plastics, that eventually end up in water bodies. This study focuses on characterizing plastic waste pollution in Sapang Baho River in the province of Rizal. The river is located in an urban area and is a significant tributary of Laguna Lake, the largest lake in the country. Through this study, macrowastes and microplastics in Sapang Baho River, Rizal were characterized and analyzed to provide baseline information and to raise awareness to address plastic pollution, in macro- and micro-scale. This study also determined possible sources of microplastics by relating the particles to the plastic wastes present as well as activities in the sites. Waste analysis and characterization studies (WACS) were conducted for four sampling stations along the river. Microplastic samples were also collected from surface water and were characterized based on form such as filament, fragment, film, foam, and pellet through microscope examination. Representative samples were subjected to Raman spectroscopy testing to identify the polymer types. Results show that macrowaste samples were mostly plastic wastes (27.33%) in terms of mass. Plastic wastes were composed of film plastic (47%). Most of the microplastic particles were in the form of filaments (92.24%) which were fragmented from textile wastes and cloth washing. In terms of color, transparent particles were dominant and particles in the lower size range (0.3 mm - 0.8 mm) were predominant. Samples subjected to Raman spectroscopy were mainly polyethylene (PE), a material used in containers and packaging. Lastly, it was calculated that the surface water of Sapang Baho River contributes approximately 24 - 362 microplastic particles to Laguna Lake.

How to cite: Diola, Ma. B. L. D., Tanchuling, M. A. N., Bonifacio, D. R. G., and Delos Santos, M. J. N.: Characterization of Plastic Pollution in Rivers: Case of Sapang Baho River, Rizal, Philippines, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-22467, https://doi.org/10.5194/egusphere-egu2020-22467, 2020.

Microplastics may affect marine and freshwater ecosystems and human health negatively. Important point sources of microplastics in rivers are locations where microplastics are released into the river, such as waste water treatment plants. Diffuse sources include the fragmentation of macroplastic items and tire and road wear particles that are flushed into the river (Unice et al., 2019). Once in the river, the different types and sizes of microplastics are transported with the flow. How this transport depends on environmental conditions is largely unknown. Due to the effort needed to monitor the microplastic concentration and composition, usually observations are carried out at one location in the water column only and are only repeated a few times. With a model, the spatial and temporal variation of the microplastics concentration can be predicted.

We modeled the transport and fate of microplastics (here defined as particles within 0.05 and 5 mm) in Dutch rivers and streams. We used a depth and width averaged flow model for the Netherlands. At the main upstream boundaries of the model (Lobith in the Rhine and Eijsden in the Meuse) microplastics were released. The concentration of different types of microplastics was based on observations by Urgert (2015). The model included the processes advection, deposition and hetero-aggregation of microplastics with sediment to determine the transport and fate. Overall, the model results suggest that the deposition is small: about 66-90 percent of the released microplastics are transported out of the model towards the sea, meaning that 10-34 percent are either deposited to the river bed or are stored in the water column. Resuspension of deposited microplastics was not included in the model. A sensitivity study for which resuspension was included suggests that it is not an important process in the current 1D simulation, since the flow velocities at accumulation areas rarely exceed the critical flow velocity for resuspension.  The simulated annual transport of microplastics is higher than estimates based on observations (van der Wal et al., 2015; Mani et al., 2015), although sources within the Netherlands are not yet included in the model. This needs to be re-evaluated in the future, after sources of microplastics from within The Netherlands have been introduced in the model.

• Mani T., A. Hauk, U. Walter and P. Burkhardt-Holm (2015) Microplastics profile along the Rhine River. Nature Scientific Reports.
• Unice, K.M., M.P. Weeber, M.M. Abramson, R.C.D. Reid, J.A.G. van Gils, A.A. Markus, A.D. Vethaak and J.M. Panko (2019) Characterizing export of land-based microplastics to the estuary – Part I: Application of integrated geospatial microplastic transport models to assess tire and road wear particles in the Seine watershed. Science of the Total Environment. https://doi.org/10.1016/j.scitotenv.2018.07.368
• Urgert, W. (2015) Microplastics in the rivers Meuse and Rhine-Developing guidance for a possible future monitoring program (MSc Thesis)
• Van der Wal, M., M. van der Meulen, G. Tweehuijsen, M. Peterlin, A. Palatinus, K. Virsek, L. Coscia and A. Krzan (2015) Identification and Assessment of Riverine Input of (Marine) Litter. Final Report for the European Commission DG Environment under Framework Contract No ENV.D.2/FRA/2012/0025.

How to cite: Buschman, F., van der Linden, A., and Markus, A.: Riverine transport of microplastics from the Dutch border to the North sea, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11223, https://doi.org/10.5194/egusphere-egu2020-11223, 2020.