Monitoring Litter Inputs from the Adour River (Southwest France) to the Marine Environment

The largest estuary on the planet is not spared from plastic pollution: Case of the St. Lawrence River Estuary

The St. Lawrence River, one of the world's largest estuaries, drains >25 % of the world's freshwater reserves and is affected by various anthropogenic effluents. Although previous studies reported micro- and nanoplastics contamination in the Estuary and Gulf of St. Lawrence (EGSL), this study provides a first evaluation of macroplastic pollution along the north and south shores of the EGSL. Plastic debris categorization was performed according to the OSPAR protocol completed by polymer identification using Fourier-transform infrared spectroscopy. The EGSL appeared ubiquitously contaminated by plastic debris, dominated by single-use plastics primarily made of polypropylene (28 %), polyethylene (25 %) and polystyrene (17 %). The EGSL shores exhibited a mean contamination level of 0.17 ± 0.11 items/m2 and distance to Montreal significantly influenced the distribution of plastic debris. This study provides an essential baseline for implementing local waste reduction and management actions in the St. Lawrence watershed to reduce plastic pollution.

From riverbank to the sea: An initial assessment of plastic pollution along the Ciliwung River, Indonesia

This study presents the first comprehensive analysis of anthropogenic debris on the riverbanks of the Ciliwung River, covering upstream to downstream areas. The mean of debris found in each measurement was 32.79 ± 15.38 items/m2 with a weight of 106.00 ± 50.23 g/m2. Plastic debris accounted for over 50 % of all litter items identified and represents 55 % by weight, signifying a significantly high prevalence compared to global studies examining litter along riverbanks. The majority of the plastics found originated from Single-use applications and were predominantly made from Styrofoam. This investigation demonstrated the importance of actions to reduce single use applications and to improve waste management strategies. This can be achieved through proactive initiatives coupled with adaptable approaches, such as implementing effective urban planning and enhancing waste collection capacity.

Division and retention of floating plastic at river bifurcations

The transport of floating macroplastics (>2.5 cm) can be impacted by variations in hydrometeorological forcing. Several studies have demonstrated that river discharge, wind, and tides can either accelerate or impede the downstream travel path of plastic. However, there remains a substantial gap in our understanding of the impact of river geomorphological complexity on this process. In this context, the role that river bifurcations play in driving plastic dynamics under different hydrometeorological conditions is largely unexplored. Here, we show that specific plastic item categories react differently to the transport drivers, and bifurcation areas can function both as a retention and release site of plastic litter. We found that hard polyolefin appears to be the most responsive plastic to changes in flow discharge (ρ≈0.40, p≈0.01). Absolute wind velocity magnitude does not correlate to plastic transport. We explored correlations of the various plastic items types with wind vector components in all directions. Multilayer plastics correlated highest to the wind vector component that is most effective in driving plastics from an urban area to the river (ρ≈0.57, p≈0.0001). On a monthly scale, the bifurcation area retained up to 50% of the incoming upstream plastic flux. At other times, an additional 30% was released in the same area. Our results demonstrate how bifurcations distribute different plastic items types downstream under varied hydrometeorological conditions. These yields underscore the importance of assessing floating plastic transport in specific plastic item categories and taking river geomorphological complexity into account.

Spatial accumulation of flood-driven riverside litter in two Northern Atlantic Rivers

The escalation of litter accumulation in aquatic environments is recognized as an emerging global concern. Although rivers represent the main conduits for land-based waste into the oceans, the spatial dynamics of litter accumulation in these systems remain poorly investigated, especially after hydro-climatic extreme events. Floods have been identified as major drivers of litter mobilization, including macroplastics, within rivers. However, predicting flood-induced litter accumulation along riverbanks is complex due to the cumulative interplay of multiple environmental (geomorphological and riparian) and anthropogenic factors. Using empirical data collected from 14 stream reaches in two Northern Atlantic rivers in Portugal, our study evaluates which factors, among geomorphological, riparian, and anthropogenic descriptors, best drive riverside litter accumulation after floods. Taking into account the longitudinal gradient and the spatial heterogeneity of the studied reaches, our study enhances how the accumulation and characteristics (type, size) of riverside litter vary across a rural-urban continuum. Our model reveals that the combination of the human population density and the stream slope at river reach showed the highest explanatory power for the accumulation of riverside litter. Our findings indicate that litter tends to be retained close to the source, even under flood conditions. We also found that the structure of riparian vegetation showed low explanatory power for litter accumulation. However, riparian trapping could be influenced by litter input (density and type) which varies with anthropogenic activities. This work highlights the importance of gathering field data to identify critical areas of riverside litter accumulation within river basins. Our findings can further support environmental managers in designing and implementing effective cleanup campaigns and implementing plastic recovery strategies at specific areas. Nevertheless, it is crucial to enhance coordinated efforts across the entire value chain to reduce plastic pollution, promote innovative approaches for plastic litter valorization, and establish effective prevention pathways.

Investigation of microplastics and microplastic communities in selected river and lake basin soils of Thiruvananthapuram District, Kerala, India

Riparian areas are highly dynamic bio-geophysical settings with a surge of waste deposition predominantly including land-based plastic discards. These polymer discards are destined to be the prime constitution of marine "plastisphere." The polymer fate is determined by waterbodies, where the chances of plastic retention are higher, eventually mediating the formation of microplastics (MPs) in years or decades. Such formed MPs are a potential threat to the aqua bio-regime. A systematic investigation of three waterbody basin soils (Karamana River, Killiyar, and Akkulam-Veli Lake) showed the presence of MPs in all the samples analyzed with varying sizes, shapes, colors, and compositions. MPs of the shapes flakes, fragments, filaments, sheets, foams, and fibers were observed with dimensions 0.3-4.7 mm. Most of the particles were white in hue (WT), followed by colorless (CL), light yellow (L.Y), light brown (L.B), orange (OR), red (RD), and blue (BL), respectively. The polymer communities were identified as high-density polyethylene (HDPE), low-density polyethylene (LDPE), polypropylene (PP), polyethylene terephthalate (PET), polystyrene (PS), and nylon. The highest average MP density was identified in the basin of Killiyar (799 ± 0.09 pieces/kg) followed by Karamana River (671 ± 3.45 pieces/kg), indicating the closeness of the sampling station to the city center compared to Akkulam-Veli Lake (486 ± 58.55 pieces/kg). The majority of the sampling sites belonged to the slopy areas and came under the highly urbanized land category. A close association was observed between particle abundance and urban activity. The study foresees possible threats inflicted by MP abundance upon the area-wide hydro-biological system.

Quantification and characterization of macro- and mesoplastic items in the water column of the river Waal

Although studies on plastic concentrations mainly focus on the marine environment, recently, an increasing number of studies point out environmental consequences in freshwater environments around the world. However, there still is a paucity of field data on the abundance of riverine plastic items, in particular in the water column. In this study, we provide an overview of macro- and mesoplastic concentrations, categories, ages, and origin over several years in the water column of the river Waal, in the Netherlands. The river water column was passively sampled at two selected locations using a stow net at very low and low discharges (range 537 - 1345 m³.s^-1). The most dominant macro- and mesoplastic categories were 'Miscellaneous plastic waste', including "Plastic film 2.5 - 50 cm (soft)" and "Plastic film 0 - 2.5 cm (soft)" as main categories. Macro- and mesoplastic categories were found to show limited variability during several years of monitoring. The mean macroplastic concentration (± SD) ranged between 2.2 × 10^-3 ± 0.001 and 7.4 × 10^-3 ± 0.003 particles.m^-3 for October 2020 and November 2018, respectively. In 2020, the plastic concentrations showed a sharp decrease compared to the previous years, most likely as a consequence of the COVID-19 crisis. The origin of the plastics (e.g., countries) also showed little variability during monitoring. The consistency of several characteristics of the collected plastic suggests that the same sources were responsible for the macro- and mesoplastic input into the river Waal during low discharges and over multiple years. We present the first temporal assessment of macro- and mesoplastic concentrations and composition in the water column of the river Waal. The outcome of the current study can be used to support the development of management measures by decision makers.

The challenge of reducing macroplastic pollution: Testing the effectiveness of a river boom under real environmental conditions

Improving collection technologies is crucial to develop effective and economically feasible solutions for catching plastic from riverine environments. However, floating booms are being constructed and deployed in river around the world without rigorously testing its effectiveness. In this study, we tested the effectiveness of a boom under realistic conditions for several configurations and treatments (including "C-shape" and "Slash-shape" configurations). For this, we used the same macroplastics that leak out of waste management channels in order to be as realistic as possible. In total we used 52 plastic articles of 13 different polymers. The global effectiveness of the tested C-shape boom was lower than expected under such conditions (around 37 % of retention). The effectiveness of the Slash-shape boom was considerably worst (<10 %). However, the effectiveness varies greatly according to the particular characteristics of the plastic articles (i.e., shape and polymer composition), ranged from 0 to 100 %. For example, the boom could be 100 % effective retaining plastics such as Stylofoam trays and cups, 40-20 % for food-wrappers but 0 % for disposable plates and spoons, straws, monofilament fishing lines, packaging straps, hoses, pipes, elastic bands, etc. It seems that to have a reasonable catch-effectiveness and be cost-efficient, boom designs need to be improved and tested under different environmental conditions before to reach the market. In addition, it is unrealistic to select only high buoyancy plastics for testing them.

From source to sink: A comparative study of streamside and beach litter in the Black Sea

The increasing amount of marine litter pollution and its impact on the marine environment raises global concern. This study aims to reveal the effect of streams on marine litter density and composition. A total of ten stations on the southeastern Black Sea and six stations on the Manahoz stream were seasonally surveyed. The litter density ranged between 0.838 ± 0.33 and 4.01 ± 0.55 items/m² in the beach stations, and 0.93 ± 0.27 2.40 ± 2.18 items/m² in the streamside stations. No significant difference was determined among the seasons for both beach and streamside (Kruskal-Wallis test, p > 0.05). On the other hand, the litter density was also similar in beach and streamside stations in the same season. The litter composition consisted of > 75% plastic. Principal component analysis and PERMANOVA determined no significant difference in litter composition among beach and streamside stations. The litter items mostly consisted of single-use items. Among them, plastic beverage containers were the most abundant litter subcategory during the study (ranging between 18.79% and 34.50%). The subcategory composition exhibited a significant difference among beach and streamside stations (ANOSIM, p < 0.05), which was mainly explained by plastic pieces, beverage containers, and foams according to SIMPER analysis. Personal protection equipment that was not reported before the COVID-19 pandemic emerged. The results of our study can be used for marine litter modeling studies and legislation for restriction or ban of most abundant single-use litter items.

Anthropogenic litter in terrestrial flora and fauna: Is the situation as bad as in the ocean? A field study in Southern Germany on five meadows and 150 ruminants in comparison with marine debris

In contrast to the abundance of research on marine debris, terrestrial anthropogenic litter and its impacts are largely lacking scientific attention. Therefore, the main objective of the present study is to find out whether ingested litter produces pathological consequences to the health of domestic ruminants, as it does in their relatives in the ocean, the cetaceans. For this purpose, five meadows (49°18'N, 10°24'E) with a total survey area of 139,050 m² as well as the gastric content of 100 slaughtered cattle and 50 slaughtered sheep have been examined for persistent man-made debris in Northern Bavaria, Germany. All the five meadows contained garbage, and plastics were always part of it. Including glass and metal, 521 persistent anthropogenic objects were detected altogether, equalling a litter density of 3747 items per km². Of the examined animals, 30.0% of the cattle and 6.0% of the sheep harboured anthropogenic foreign bodies in their gastric tract. As in the case of cetaceans, plastics were the most dominant litter material. Bezoars had formed around plastic fibres of agricultural origin in two young bulls, whereas pointed metal objects were associated in cattle with traumatic lesions in the reticulum and the tongue. Of all the ingested anthropogenic debris, 24 items (26.4%) had direct equivalents in the studied meadows. Comparing with marine litter, 28 items (30.8%) were also present in marine environments and 27 items (29.7%) were previously reported as foreign bodies in marine animals. At least in this study region, waste pollution affected terrestrial environments and domestic animals, with clear equivalents in the marine world. Ingested foreign bodies produced lesions that may have reduced the animals' welfare and, regarding commercial purposes, their productivity.

The Travel Time of Floatable Litter of Different Densities Influenced by River Flow Velocity

Rivers are a source of life. However, these past years, the sustainability of rivers around the world has been threatened by urbanization, industrialization, and rapid development. These activities put pressure on waterway systems and rivers, leading to the emergence of riverine litter. The lack of understanding of the migration of litter in rivers can affect the decision-making efficiency of policymakers when it comes to riverine litter management. Therefore, the primary objective of this study is to evaluate the travel time for different densities of Floatable Litter (FL) in rivers influenced by river flow velocity. The density of the selected FL was manually determined by assessing litter characteristics of mass, volume, and size. The Sg. Berkelah river in Pahang, Malaysia was used as the simulation medium for the sampling of FL travel time utilizing the extrapolation of the Time of Travel (ToT) approach. The ToT technique utilizes a 30 m distance. The sampling was done under three different river flow velocity conditions. In this study, a correlation analysis between these two variables was carried out and evaluated. The results revealed that magazine papers possess the fastest FL travel time, with T = 43.93 s when v = 0.230 m/s, while cloth possesses the slowest FL travel time, with T = 204.90 s when v = 0.167 m/s. The travel time of FL is not influenced by low-class density, p < 1000 kg/m3, but by other factors that have a stronger influence on the travel time of horizontally migrated litter. This study provides a basic understanding and overview of FL migrating characteristics in rivers for further reference by local authorities for litter monitoring and also future riverine litter studies.

From city to sea: Spatiotemporal dynamics of floating macrolitter in the Tiber River

Rivers are undoubtedly the main pathway of waste dispersed in the environment that from land reaches oceans and seas increasing the amount of marine litter. Major cities are a great source of riverine litter as large urbanization can originate pressure on the integrated waste management resulting in litter entering the rivers. Within this study, we aim to investigate the dynamic of floating riverine macrolitter (items >2.5 cm) in the city of Rome before it reaches the sea by assessing the composition, amount, and seasonal trends of litter transported from the urban centre to the main river mouth of Tiber River. Visual surveys for a whole year (March 2021-February 2022) were conducted from two bridges, Scienza Bridge (in the city) and Scafa Bridge (at the main river mouth) and followed JRC/RIMMEL protocol for riverine litter monitoring. Overall, similar litter composition was observed from the city centre to the mouth with a prevalence of plastic material, mainly related to fragmentation process (i.e. plastic pieces) and single use items, mainly in food and beverage sectors. An extrapolated annual loading of 4 × 10⁵ items/year was estimated at the main mouth of Tiber River. The litter flux seems to be influenced by the seasonal variability and hydrometeorological parameters. The frequency of size classes decreases with increasing size in both sites, and more than half of the recorded items were below 10 cm. Specific categories belonging to "other plastics" have been reported related to anti-Covid-19 behaviour such as face masks and beverage sector, e.g. bottle lids and rings. The main colour of plastics was white, suggesting weathering process of floating riverine litter. This study contributes to increasing knowledge of the origin, composition and spatiotemporal dynamics of riverine floating litter from the city and entering the sea.

Sources, sinks and transformations of plastics in our oceans: Review, management strategies and modelling

Currently, 60-80 % of litter is plastic, and almost 10 % ends up in the ocean directly or indirectly. Plastics often suffer from photooxidation producing microplastics and these microplastics derived from the breakdown of larger plastics are called secondary microplastics. These compounds simply cannot be extracted from the oceans, and once mixed, they enter the food chain and may have toxic effects. This work reviews the current existing information on the topic in the scientific literature. Then, the current plastic management strategies in the marine environment are analysed, with the objective of identifying possible needs and improvements from a sustainable point of view, and to define new approaches. Simultaneously, a material flows analysis in different media of the marine environment is carried out using system dynamics. A preliminary model of plastics mobilization into the ocean to other media of the marine environment (like sediments and biota) is developed and validated with the existing data from the previous steps of the work. This work expands the current knowledge on the plastics management, their transformations and accumulation in the marine environment and the harmful effects on it. Likewise, preliminary dynamic model of mobilization of plastics in the ocean is implemented, run, and validated. The developed model can be used to predict trends in the distribution of the plastics in the ocean with time. In addition, the most important reservoirs of plastics in the ocean can be observed. Although plastics undergo transformations in the marine environment, it is not a means of disposal since most of them are non-biodegradable. Most plastics accumulate on the seabed. The proportion of microplastics found in sediments is higher than that of macroplastics.

Macroplastic transfer dynamics in the Loire estuary: Similarities and specificities with macrotidal estuaries

The quantification of macroplastic fluxes transferred by rivers toward the pelagic environment requires a better understanding of macrodebris transfer processes in estuarine environments. Following the strategy adopted in the Seine estuary, this study aims to characterize macroplastic trajectories in the Loire estuary. Between January 2020 and July 2021, 35 trajectories were monitored using plastic bottles equipped with GPS-trackers. With total travelled distances between 100 m and 103.6 km, trajectories show great spatiotemporal variability. The various forcing factors (macroplastic buoyancy, estuaries tidal and hydrometeorological conditions, geomorphology and vegetation) lead to chaotic trajectories, preventing accurate predictions in macroplastic transfer and storage/remobilization dynamics. In the Loire estuary like in the Seine one, no tracked bottle reached the Atlantic Ocean. It confirms that macrotidal estuaries under temperate climates constitute accumulation zones and slow pathways for macroplastics, but raises question on the real fluxes transferred from continental areas to oceans.

Temporal changes of plastic litter and associated encrusting biota: Evidence from Central Italy (Mediterranean Sea)

We investigated the temporal changes from spring to summer of the stranded litter and the composition of plastic encrusting biota along an Italian beach. Our findings highlight a higher quantity of litter (average value 1510.67 ± 581.27 items) in spring, particularly plastic material with a composition driven by currents, winds and waves transported from rivers to sea. During summer the source was caused by anti-social behaviours (e.g. cigarettes). Regarding the plastic size, the most is macroplastic (85.96 %), followed by mesoplastic (13.74 %) and megaplastic (0.30 %) overall, and no seasonal trend was observed. Concerning the encrusting biota, Mollusca was the most frequent phylum found on plastic beach litter, whereas Porifera the most abundant overall. During spring a greater abundance of individuals was recorded compared to summer. The trend of taxa richness was decreasing from spring to summer. Arthropoda, Porifera and Mollusca phyla were significantly more abundant in spring, while Algae in summer.

Rivers of waste: Anthropogenic litter in intermittent Sardinian rivers, Italy (Central Mediterranean)

While the increasing accumulation of anthropogenic litter in the marine environment has received considerable attention over the last decade, litter occurrence and distribution in rivers, the main source of marine litter, have been comparatively less investigated. Moreover, little information is available about the amount and typology of Riverine Anthropogenic Macro-litter (RAM) entering marine environments from intermittent rivers in low populated areas of the Mediterranean basin. To provide insights on this issue, we investigated density and composition of RAM accumulated over a total of 133 riverbanks, belonging to 37 river basins in the Sardinia Island (Mediterranean Sea). We report here that plastics, especially single-use items, represent the most frequent and abundant RAM category in all investigated basins. Statistical modelling revealed that occurrence of lightweight RAM (especially plastic) is mostly explained by levels of urban (12.3% of the relative contribution) and agricultural (12%) land use of the territory, whereas the proximity of bridges to the sampling point (21%) and the local population density (19.8%) are best predictors of heavy weighted RAM items (i.e., large metal items, appliances) occurrence. Our results confirm that plastics represent an important component of RAM and pinpoint that, beside plastic reduction policies and better waste management, actions aimed at abating and monitoring litter contamination should be localized on the proximity of bridges, whatever the local population density. Finally, to fill existing knowledge gaps in understanding the severity of litter discharge and accumulation in the Mediterranean Sea, land-to-sea systematic monitoring campaigns at appropriate spatial and temporal scales should be put in place.

Microplastic abundance in the Thames River during the New Year period

Microplastic pollution is widely studied; however, research into the effects of large-scale firework displays and the impact on surrounding waterways appears to be lacking. This study is potentially the first to look at microplastic abundance in rivers after a major firework event. To assess the impact of the 2020 New Year's firework display in London, a 3 litre water sample was collected over nine consecutive days at Westminster on the River Thames. A total of 2760 pieces of microplastics (99% fibres) were counted using light microscopy, and further analysis was performed on representative plastic samples (354) using Fourier Transform Infrared Spectroscopy (FTIR). Whilst anthropogenic microfibres made up 11%, most microplastic identified (13.3%) were polychloroprene. This study demonstrates the occurrence of a short-term influx of microplastics in the River Thames following the New Year fireworks, which will have an additional detrimental impact on the ecology and aquaculture of the river and neighbouring waterways.

Riparian vegetation as a trap for plastic litter

Plastic pollution represents the most widespread threaten throughout the world and, amongst aquatic habitats, freshwaters and in particular riparian zones seems to be highly disturbed. Since the plastic storage and accumulation on the riparian vegetation have not yet been deeply investigated, here, we focussed on the riparian zone's function in trapping plastic litter. To do so, we assessed the occurrence and density of plastics in different vegetated (arboreal, shrubby, herbaceous, reed, bush) and unvegetated types in 8 central Italian rivers, running in different land use contexts. Our results showed that plastic pieces, bags, bottles and food containers were the most abundant specific categories on the vegetated types, demonstrating the riparian vegetation role in trapping plastic litter. Specifically, the highest plastic density was found on the shrubby type suggesting that a tree shape retains plastics more easily than all other vegetated and unvegetated types. Shape and size classification of plastics are not significantly different between vegetated and unvegetated types. These findings allow to collect important information on how the riparian vegetation can be exploited in management activities for removing plastic litters from both freshwater and sea, being the former considered the main plastic source for the latter. This study highlights a further ecosystem service as mechanical filter provided by the riparian zone, even if further studies ought to be performed to understand the role of vegetation as plastic trap and the possible detrimental effects of plastics on the plant health status.

The role of hydrodynamic fluctuations and wind intensity on the distribution of plastic debris on the sandy beaches of Paraná River, Argentina

Plastic in the environment is considered an emerging pollutant of global concern. In spite of intensive research, many questions remain open, such as the processes that drive the deposition and remobilization of plastic debris on river beaches. The objectives of this study were: i) to analyze the influence of the natural hydrological fluctuations and wind intensity on the distribution of mesoplastic (0.5-2.5 cm) and macroplastic (>2.5 cm) debris in beach sediments of a large river, ii) to describe the type of plastic debris found and iii) to explore potential relations between the number of items and weight of macro- and mesoplastics. Our results suggest that, during lowering water levels, flow removes the plastic debris and transports it further downstream. Conversely, when the beach sediments remain exposed during long periods, the plastic debris accumulates considerably. Nevertheless, the influence of wind intensity on plastic debris transport was comparatively negligible. In other words, in our study the water flow had a greater capacity to remobilize and transport plastic debris than the wind. The most abundant mesoplastic items were foam, hard plastic, film and small fragments of fishing line. The dominant macroplastic items recorded were pieces of fishing line (nylon) and cigarette filters (cellulose acetate), typically discarded by beach users. Other items found in large quantities were soft packaging elements (expanded polystyrene), hard plastic containers (polystyrene, polyethylene terephthalate) and beverage bottles (polyethylene terephthalate), typical items of domestic use in the Paraná River region. Finally, we found that the density of macroplastic items is highly correlated to the density of mesoplastic items, serving as surrogate for further estimations. Our results could help to develop better mitigation strategies in seasonal riverscapes, based on the influence of the hydrological cycle and the characteristics of the most abundant meso- and macroplastics.

Plastic ‘Highways’ to the Sea: The Problem of Litter in English Inland Waterways

There is a conspicuous lacuna in the Environmental Protection Act (EPA) 1990 because it imposes no legal duty on statutory bodies to clear litter from aquatic environments (rivers, canals and lakes) in England and Wales. This paper identifies a significant gap in the law on aquatic environmental protection by undertaking doctrinal research, including contextual analysis of references to rivers in ‘soft’ law (e.g., policy documents such as the Conservative Government’s Litter Strategy) and ‘hard law’ (e.g., legislation including the EPA 1990); an examination of the problems with existing legal frameworks in this sphere and an exploration of legislative and practical measures which could protect our rivers and other inland waterways from litter. A legislative amendment to the EPA is proposed with discussion of whether imposing a duty on an existing body or a new, specialised body to clear litter from rivers will ameliorate these problems. The intention behind this paper is to initiate an informed debate on how to protect aquatic environments from the harmful effects of litter.

Transfer dynamics of macroplastics in estuaries - New insights from the Seine estuary: Part 3. What fate for macroplastics?

Macroplastic emissions from the Seine estuary to the English Channel were estimated using institutional cleaning of riverbanks, combined with a tagged litter experiment. Cleaning were performed between March 2018 and April 2019 by the non-profit company Naturaul'un over 19 sites covering 20 km of riverbanks. A total of 365 tagged litter (90% macroplastics) was released in the estuary in March (n = 200), at the end of the winter/spring flood 2018, in July (n = 58), August (n = 56) and September 2018 (n = 51) during low river flow periods. Over the total tagged litter, 102 (28%) were recovered by Naturaul'un. Relative to the total amount of macroplastics (>5 cm) collected and the estimated amount of smaller/hidden macroplastics (>5 mm) not collected, the maximum macroplastic emission to the English Channel was estimated to be ~100-200 metric tons per year.

Plastic pollution: A focus on freshwater biodiversity

Plastics are dominant pollutants in freshwater ecosystems worldwide. Scientific studies that investigated the interaction between plastics and freshwater biodiversity are incipient, especially if compared to the marine realm. In this review, we provide a brief overview of plastic pollution in freshwater ecosystems around the world. We found evidence of plastic ingestion by 206 freshwater species, from invertebrates to mammals, in natural or semi-natural ecosystems. In addition, we reported other consequences of synthetic polymers in freshwater ecosystems-including, for instance, the entanglement of animals of different groups (e.g., birds). The problem of plastic pollution is complex and will need coordinated actions, such as recycling programs, correct disposal, stringent legislation, regular inspection, replacement of synthetic polymers with other materials, and ecological restoration. Current information indicates that the situation in freshwater ecosystems may be as detrimental as the pollution found in the ocean, although highly underappreciated.

Quantification and composition analysis of plastic pollution in riverine beaches of the lower Paraná River, Argentina

Plastic pollution and the numerous consequences it has on aquatic life have become a huge concern in recent years. While many studies have been conducted in marine environments, studies in freshwater ecosystems are scarce and insufficient. The Paraná River is the most important water course in the La Plata River basin and the fifth in the world with a mean annual discharge of 18,000 m³ per second. Currently available studies show the presence of plastic in river shores and fish gut, but more research should be carried out in order to know the extension and origin of plastic contamination. Therefore, the aim of this study was to quantify and characterize macro-, meso-, and microplastics found in the riverine beaches next to Rosario city, the most populated city standing by the lower Paraná River coast in Argentina. The results show that plastic pollution is ubiquitous, but the city shores are significantly more polluted than the wetland shore with a mean of 30,780 and 6375 microplastics per square meter respectively (p = 0.024). The food and beverage industry packaging combined were the most frequent macroplastics found. Also, 3 out of 4 meso- and microplastics were white/transparent, the color that is most likely to be ingested by fish and invertebrates. Finally, all micro- and mesoplastics found were secondary and, in the case of microplastics, they were mainly fibers (93.4%) which highlight its ecological relevance. As a whole, plastic contamination is a serious issue in the Rosario area, specially single-use plastics and short-lived products. The anthropic effect of the cities and how it contributes to plastic pollution are evident.

Macroplastics in rivers: present knowledge, issues and challenges

Macroplastics are the primary contributor to riverine plastic pollution by mass, posing a wide range of serious threats for riverine systems, from adversely affecting various life forms within the riverine system, to potentially increasing flood risk, and generally resulting in adverse effects on any livelihoods. Compared to other river-related research disciplines, research into riverine macroplastics and their effects has not yet featured prominently. Various quantification methods are presently used to assess the presence of macroplastics at different locations within river systems; however, overcoming limitations and unifying methods remain an essential need. Macroplastic dynamics in rivers are subject to various factors, including both material and river characteristics. We review the diverse factors that potentially influence macroplastic dynamics in rivers, and highlight our knowledge limits. We advocate for future research that enables synergies between improved field quantification techniques, use of global protocols and data sharing, and laboratory experiments. This is needed to obtain a riverine macroplastic budget model, required for the implementation of targeted management practices. Finally, a multilayer potential management strategy is presented: (i) reducing the macroplastic supply into rivers; (ii) removing effectively and safely macroplastics from within rivers; and (iii) treating macroplastics once removed from the riverine system.

Are the tidal flooded forests sinks for litter in the Amazonian estuary?

Pollution in aquatic ecosystems is rapidly becoming one of the world's greatest ecological challenges. Given their intermediate position between terrestrial and marine environments, estuarine systems are especially vulnerable to human pollution. Amazonian estuaries have unique characteristics, such as heterogeneous landscape intercalating tracts of vegetation with sandbanks and beaches. In the present study, we provide the first qualitative and quantitative data on litter retention in an Amazonian estuary, comparing vegetated and bare substrate areas. Overall, 12,003 items were recovered, with a mean ± SD density and weight of 1.69 ± 2.16 items/m² and 78.08 ± 93.11 g/m², respectively. Plastic was the principal material (80.97%) found. The highest number of items was found in the vegetated habitats (73.11%), indicating these areas as the most affected by plastic pollution. Our findings provide important insights for future research planning and implementation of effective public policies for conservation and management of these important ecosystems.

Fate of river-borne floating litter during the flooding event in the northeastern part of the Black Sea in October 2018

This study is focused on delivery and fate of floating marine litter (FML) carried by rivers to coastal sea. We examine a large flooding event which happened in the northeastern part of the Black Sea in October 2018. A high resolution circulation model coupled with a Lagrangian particle model is applied to simulate transport of riverine FML in the coastal sea. During this flood multiple river plumes in the study area coalesced into one stripe of freshened water which occupied large segment of coastal sea along the shoreline. Riverine FML was transported within this stripe far off its sources in river mouths and remained arrested near the shore. As a result, approximately half of the discharged FML was washed ashore by the Stokes drift. FML, which remained in the sea, accumulated at convergence lines associated with large salinity gradients at the fronts between the river plumes and the ambient sea.

Concentration and adsorption of Pb and Cu in microplastics: Case study in aquatic environment

Microplastics are proven as heavy metals vector, but the adsorption mechanism still unclear. This study investigated the adsorption of Pb and Cu in microplastics in the Musi River and the environment effect. This study was conducted in 10 stations along the Musi River to the estuary. The polymers of microplastics were dominated by PP and followed by PE, PES, PVC, and nylon. The average concentration of Pb (0.0347 mg L^-1 for water and 0.470 mg kg^-1 for microplastics) was higher than Cu (0.0138 mg L^-1 for water and 0.091 mg kg^-1 for microplastics). The highest concentration of both metals in water and microplastics were found in the estuary. Environment parameters have different effects on the adsorption. The present study found that the adsorption processes were following the Freundlich model. The interaction metal-microplastic was physisorption. Pb and Cu will attach through weak bonds and easy to release into the aquatic ecosystem.

Wasting the North Sea? - A field-based assessment of anthropogenic macrolitter loads and emission rates of three German tributaries

Research into the scope of litter pollution in freshwater systems has shown similar levels to the marine and coastal environment. Global model estimates of riverine emission rates of anthropogenic litter are largely based on microplastic studies as long-term and holistic observations of riverine macroplastics are still scarce. This study therefore aims to contribute a detailed assessment of macrolitter in the transitional waters of three major North Sea tributaries: Ems, Weser, and Elbe. 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. The 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 harbors. Stony embankments were least polluted. Benthic litter levels appeared substantial despite rapid burial of objects being likely due to high suspended sediment loads. Two extrapolation approaches were tested to scale daily and annual litter emission quantities of surface- and subsurface-floating litter. Using the mean (median) litter item mass from water column samples, total annual mass discharges were calculated: ∼0.9 (0.2) t y^-1 to ∼2.8 (0.5) t y^-1 emitted via the Ems, ∼1.3 (0.2) t y^-1 to ∼12.0 (1.9) t y^-1 through the Weser, and ∼14.7 (2.4) t y^-1 to ∼801 (128) t y^-1 carried into the North Sea by the Elbe. These rates deviate considerably from previous model estimates of plastic loads discharged by these three rivers. Future studies should therefore ground-truth model estimates with more river-specific and long-term field observations. Overall, the estimated plastic debris discharge quantities account for <1% of the total mass of mismanaged plastic waste per catchment.

Macroplastic Storage and Remobilization in Rivers

The paper presents a conceptual model of the route of macroplastic debris (>5 mm) through a fluvial system, which can support future works on the overlooked processes of macroplastic storage and remobilization in rivers. We divided the macroplastic route into (1) input, (2) transport, (3) storage, (4) remobilization and (5) output phases. Phase 1 is mainly controlled by humans, phases 2–4 by fluvial processes, and phase 5 by both types of controls. We hypothesize that the natural characteristics of fluvial systems and their modification by dam reservoirs and flood embankments construction are key controls on macroplastic storage and remobilization in rivers. The zone of macroplastic storage can be defined as a river floodplain inundated since the beginning of widespread disposal of plastic waste to the environment in the 1960s and the remobilization zone as a part of the storage zone influenced by floodwaters and bank erosion. The amount of macroplastic in both zones can be estimated using data on the abundance of surface- and subsurface-stored macroplastic and the lateral and vertical extent of the zones. Our model creates the framework for estimation of how much plastic has accumulated in rivers and will be present in future riverscapes.

Macroplastic pollution in freshwater environments: Focusing public and policy action

Understanding and managing plastic pollution is an increasingly important environmental priority for policy makers, businesses and scientists. Awareness of the potential damage to the world's oceans has grown but there is less attention given to freshwater ecosystems. Yet, rivers are the dominant source of plastic pollution to the marine environment, as well as a potential sink, accumulating plastic from multiple sources. Actions to reduce the presence of macroplastics in rivers is fundamental to conserving both freshwater and marine environments, but there is limited understanding of potential pollution sources, vectors and storage. Importantly, there are only a handful of studies examining the typologies of freshwater macroplastic pollution, often using different categories and collection methods. This impedes setting priorities for scientific investigation and mitigation measures. The present study identifies the most prevalent macroplastic items in freshwater environments in Europe, with a focus on consumer plastic items, i.e. those that could potentially be reduced by targeted actions by the public, as well as industrial and government intervention. Our analysis addresses the differences between reported macroplastics in freshwater and marine environments as well as those estimated from litter rates. Our results identify a macroplastic "top ten", i.e. those dominant plastic typologies that require a more focused effort to reformulate their use and management, as well as setting a common baseline for a more consistent data gathering and reporting approach.

Plastic debris dataset on the Seine river banks: Plastic pellets, unidentified plastic fragments and plastic sticks are the Top 3 items in a historical accumulation of plastics

Plastic pollution in oceans and rivers is of high concern because of its persistence in the environment and its potential impact on ecosystems. However, there is a specific lack of data in rivers. Here we present data from the Seine river banks in a historical polluted shore. Data were classified using international MSFD and OSPAR classifications. The sampled site is a quadrat of 1 m² located downstream in the estuary in a visual maximum along a 1 km shore covered by plastics. A total of 20,259 plastic debris were individually counted, classified and weighted by category for a total mass higher than 4 kg. Half of the plastic debris in number are represented by preproduction pellets.