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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.

Nowadays, plastics represent growing concern in aquatic habitats, harming more and more both ecosystem and human health. Since rivers are the main carriers of plastics to the sea, some studies were conducted on the transport of overall small plastics, but observations on big plastics (i.e., macroplastics) in rivers are poorly reported in the literature. Although most studies focused on plastic transport in the lower part of the rivers, research on the upper and middle zones are completely lacking. In this regard, this could influence the transport of plastics to the sea, with insights into the source and origin of macroplastics. Here, we aimed at overviewing macroplastic distribution along rivers, emphasizing on the global riverine plastic hotspot areas. First, 1) we analyzed and discussed the bibliometric analysis on macroplastics in rivers providing a framework for plastic pollution management. second, 2) we provided geographical insights into macroplastics by mapping global riverine plastic hotspot areas. Then, 3) we analyzed the main factors affecting macroplastic distribution and accumulation in rivers. Furthermore, 4) we assessed crucial gaps in riverine macroplastic accumulation, highlighting the importance of a plastic gradient in the horizontal transport along the entire river course (i.e., three river zones). Then, 5) we highlighted the lack of standardization regarding macroplastic size, concentration, and polymers that does not allow valuable comparisons among studies. At the end, 6) we concluded by providing future perspectives and conclusions on macroplastic distribution and accumulation in rivers worldwide. Our results might provide new insights into a comprehensive framework of macroplastic distribution along global rivers, suggesting the river rod approach as a way for future monitoring as all the complete course of a river plays a pivotal role in accumulating macroplastics.

Identifying macroplastic deposition hotspots in rivers is essential for planning cleanup efforts and assessing the risks to aquatic life and the aesthetic value of river landscapes. Recent fieldwork in mountain rivers has shown that wood jams retain significantly more macroplastic than other emergent surfaces within river channels. Here, we experimentally verify these findings by tracking the deposition of 64 PET bottles after 52–65 days of transport in the mid-mountain Skawa River (Polish Carpathians) under low to medium flow conditions. Despite variations in river channel management and the resulting morphological patterns along the study reach, the majority (71.9%, n  = 46) of tracked bottles were trapped by wood jams near the low-flow channel. The trapping efficiency was three times higher in the straight, regulated reach (14.8% per km) than in the highly sinuous, unregulated reach (4.5% per km). In the regulated reach, water inundations and wood jams are confined to a narrow zone near the low-flow channel, which may explain the high macroplastic trapping efficiency under low to medium flow conditions. In contrast, in the unmanaged, seminatural reach, where wood jams and water inundation occur over broader areas formed by extensive gravel bars, the trapping potential is lower under similar flow conditions. Previous observations showed that macroplastic deposition hotspots associated with wood jams predominantly form in wide, unmanaged river sections, where numerous jams are inundated during high flows. Our results detail this understanding, suggesting that under low to medium flows, macroplastic hotspots can also form on wood jams in regulated, narrow reaches. These findings suggest that the occurrence of wood jams, channel morphology and past flow conditions are key predictors of macroplastic hotspots formation in mountain rivers.

Greiner, B.E.; Marrone, A.; Mifsud, J.; Camilleri, K.; Camilleri, L.; Gauci, A.; Zammit, A.; Kossari-Tarnik, E., and Deidun, A., 2024. Exploring the spatial distribution, composition, and depth-related patterns of marine litter in Maltese waters: Insights from the MEDITS survey data. In: Phillips, M.R.; Al-Naemi, S., and Duarte, C.M. (eds.), Coastlines under Global Change: Proceedings from the International Coastal Symposium (ICS) 2024 (Doha, Qatar). Journal of Coastal Research, Special Issue No. 113, pp. 396-401. Charlotte (North Carolina), ISSN 0749-0208. Marine litter is one of the most serious anthropogenic challenges to the integrity of global marine ecosystems. Public awareness is often limited to the visible litter that washes up on beaches or floats on the ocean surface. Less attention is paid to marine litter that is deposited and accumulates on the seafloor, due to operational constraints. The Mediterranean Bottom Trawl Survey (MEDITS) can provide insights into the state of seabed litter distribution and composition collaterally with the primary fish shock assessment. This study analyses the MEDITS 2020/2021 marine litter dataset in terms of a spatial, temporal and depth distribution in the Geographical Subarea (GSA) 15, i.e. off the coast of Malta. The composition of the litter and its potential major sources were determined. For these analyses, a two-sided independent t-test was applied using SPSS. Visualization was done by creating maps and bar charts using QGIS and MATLAB. Results revealed tourism and household items as primary contributors to marine litter, with plastics comprising the majority. Surprisingly, the onset of the COVID-19 pandemic appears correlated with a significant reduction in seafloor litter accumulation. Spatial distribution dynamics suggest that subsurface currents influence the transport of light litter items like plastic, while heavy litter, such as metals, tends to remain localised. Compared to other Mediterranean regions, the seabed off Malta shows a relatively clean status. This study not only provides valuable insights into the local marine environment but also underscores the need for novel global strategies to address the marine litter issue. These findings prompt considerations for future environmental management practices and highlight potential areas for further research in the broader context of marine environmental monitoring.

Researchers are focused on the global issue of plastic contamination in agricultural soils because of the known effects of plastics on the soil ecosystem. Previous reviews did not pay attention to plastic sources, standardized extraction methods, soil characterization, and the abundance of plastics in agricultural soils. This study aims to review up-to-the-minute knowledge about plastic contamination studies, suggest the best method for microplastic studies, and propose future research areas. The research about plastic contamination in agricultural soils published from January 2018 to March 2022 was reviewed for this review article. Studies focusing on microplastics in soils other than agricultural soils were not considered in the present review. The data were acquired from several databases, namely Web of Science and Google Scholar. The keywords used to search these databases were \"microplastics AND agricultural soils\" and \"macroplastics AND agricultural soils\". Other literature sources were obtained from the reference lists of downloaded articles, and other pieces of literature that directly dealt with macroplastic and microplastic contamination in agricultural soils were obtained from relevant journals and books. Overall, 120 sources of literature, including 102 original research articles, 13 review articles, and five books, were selected, reviewed, and synthesized. As expected, agricultural soils, including arable lands, paddy lands, uplands, irrigation, and greenhouse soils, receive plastic contaminants. The contaminants of different sizes and forms are distributed spatially and temporally in the surface, subsurface, and profiles of the agricultural soils. Unlike previous studies that reported many studies on sewage sludge, the significant sources of plastic contamination in the agricultural soils included mulching, sludge and compost placement, and greenhouses abandonment. The distribution of plastic contamination studies in the agricultural lands is Asia: 60%; Europe: 29%; Africa: 4%; North America: 4%; Latin America: 3%; and Australia: 0%. After careful analysis of the methods used for the plastics contamination studies, the study concluded that floatations with low-density solutions such as distilled water and NaCl are efficient in separating light-density microplastics. In contrast, ZnCl and NaI are incredibly efficient in separating the heavy-density microplastics. Moreover, this review provides insight for future research in the field.

Plastic pollution in aquatic environments is an increasing global risk. In recent years, marine plastic pollution has been studied to a great extent, and it has been hypothesized that land-based plastics are its main source. Global modeling efforts have suggested that rivers in South East Asia are in fact the main contributors to plastic transport from land to the oceans. However, due to a lack of plastic transport observations, the origin and fate of riverine plastic waste is yet unclear. Here, we present results from a first assessment of riverine macroplastic emission from rivers and canals that run through a densely populated coastal urban city. Using a combination of field measurements, empirical relations and hydraulic modeling, we provide an estimate of total riverine plastic export originating from Jakarta, Indonesia, into the ocean. Furthermore, we provide insights in its composition, and variation in time and space. We found that most macroplastics in Jakarta consists of films and foils. We estimate that 2.1 × 103 tonnes of plastic waste, is transported from land to sea annually, equaling 3% of the total annual unsoundly disposed plastic waste in the Jakarta area.

The growing and pervasive presence of plastic pollution has attracted considerable interest in recent years, especially small (< 5 mm) plastic particles known as ‘microplastics’ (MPs). Their widespread presence may pose a threat to marine organisms globally. Most of the nano and microplastic (N&MP) pollution in marine environments is assumed to originate from land-based sources, but their sources, transport routes, and transformations are uncertain. Information on freshwater and terrestrial systems is lacking, and data on nanoplastic pollution are particularly sparse. The shortage of systematic studies of freshwater and terrestrial systems is a critical research gap because estimates of plastic release into these systems are much higher than those for oceans. As most plastic pollution originates in urban environments, studies of urban watersheds, particularly those with high population densities and industrial activities, are especially relevant with respect to source apportionment. Released plastic debris is transported in water, soil, and air. It can be exchanged between environmental compartments, adsorb toxic compounds, and ultimately be carried long distances, with potential to cause both physical and chemical harm to a multitude of species. Measurement challenges and a lack of standardized methods has slowed progress in determining the environmental prevalence and impacts of N&MPs. An overall aim of this review is to report the sources and abundances of N&MPs in urban watersheds. We focus on urban watersheds, and summarize monitoring methods and their limitations, knowing that identifying N&MPs and their urban/industrial sources is necessary to reduce their presence in all environments.

Anthropogenic litter in aquatic ecosystems negatively impacts ecosystems, species and economic activities. Rivers play a key role in transporting land-based waste towards the ocean. A large portion however is retained within river basins, for example in the estuary, in sediments and on the riverbanks. To effectively identify litter sources, sinks and transport mechanisms, reliable data are crucial. Furthermore, such data can support optimizing litter prevention mitigation and clean-up efforts. This paper presents the results of a 2-year monitoring campaign focused on riverbank macrolitter (>0.5 cm) in the Dutch Rhine-Meuse delta. Between 2017 and 2019, volunteers sampled 152 415 litter items at 212 unique locations. All items were categorized based on the River-OSPAR method (based on the OSPAR beach litter guidelines), which includes 110 specific item categories across ten parent categories. The median litter density was 2060 items/km, and the most observed items were foam, hard, and soft plastic fragments (55.8%). Plastic bottles, food wrappings and packaging, caps, lids and cotton swabs were the most abundant specific items. The litter density and most abundant items vary considerably between rivers, along the river, and over time. For both rivers however, the highest litter density values were found at the Belgian (Meuse) and German (Rhine) borders, and at the Biesbosch National Park, the most downstream location. With this paper, we aim to provide a first scientific overview of the abundance, top item categories, and spatiotemporal variation of anthropogenic litter on riverbanks in the Dutch Rhine-Meuse delta. In addition, we evaluate the used River-OSPAR method and provide suggestions for future implementation in (inter)national long-term monitoring strategies. The results can be used by scientists and policy-makers for future litter monitoring, prevention and clean-up strategies.

Plastic pollution is one of the most acute environmental topics of our time. While there is a great scientific effort to tackle this problem, it has not always been well-coordinated or properly targeted. In this short review, we call for scientists to get involved in three crucial topics (threats) underestimated—or ignored—in freshwater systems: (i) plastic-species entanglement, (ii) plastic as nesting material, and (iii) macroplastic debris coming from mismanaged household solid waste. Reducing the knowledge gaps between marine and freshwater environments will be crucial to solute the plastic pollution problem effectively and globally. Therefore, we make a plea here to reinforce research activities on these three issues in freshwater environments worldwide.

With the focus on microplastic in current research, macroplastic is often not further considered. Thus, this review paper is the first to analyse the entry paths, accumulation zones, and sinks of macroplastic in the aquatic, terrestrial, and atmospheric environment by presenting transport paths and concentrations in the environment as well as related risks. This is done by applying the Source–Pathway–Receptor model on macroplastic in the environment. Based on this model, the life cycle of macroplastic is structurally described, and knowledge gaps are identified. Hence, current research aspects on macroplastic as well as a sound delimitation between macro- and microplastic that can be applied to future research are indicated. The results can be used as basic information for further research and show a qualitative assessment of the impact of macroplastic that ends up in the environment and accumulates there. Furthermore, the applied model allows for the first time a quantitative and structured approach to macroplastic in the environment.