Preliminary Assessment of Waste Accumulation along Riverbanks in Italy

doi:10.21203/rs.3.rs-4094861/v1

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Preliminary Assessment of Waste Accumulation along Riverbanks in Italy

https://doi.org/10.21203/rs.3.rs-4094861/v1

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This paper presents a preliminary assessment of waste accumulation along riverbanks in Italy, aiming to provide baseline data for future monitoring and management efforts. The study surveyed 18 stations along 16 rivers across different regions of Italy, from north to south, to quantify and characterise the types and abundance of litter present along their banks. Field surveys were conducted by Legambiente citizen scientists applying a standardised protocol to record and categorise litter items systematically. Results indicate widespread litter accumulation, with a median density of 457 items/100 m. A diverse range of items was observed, including artificial polymer materials (56%), glass/ceramics (20%), metal (11%) and paper/cardboard (6%). Half of the items belonged to just four categories: glass bottles (17%), cigarette butts (14%), plastic pieces (11%), and wet wipes (8%). Differences in litter density and composition were observed according to the land use (urban, agricultural, natural, urban park) of the area surrounding the monitoring stations. Riverbanks included in urban parks presented the highest litter densities. They were characterised by the high presence of litter from recreational activities (glass bottles, cigarettes, caps, and pull tabs), suggesting uncivil behaviour by visitors. The findings of this study allow for the identification of litter sources and underscore the importance of citizen science in filling information gaps since no previous data on litter on riverbanks in Italy were available.

riverbanks

pollution

plastic

wet wipes

citizen science

riverine litter

single-use plastic

Waste accumulation in natural environments poses severe threats to ecosystems and human health, with plastic representing the large majority of it (Li et al. 2020). Plastic pollution contributes to climate change (Ford et al. 2022), and it is considered a threat to planetary boundaries (e.g., Villarubia-Gomez et al. 2018). Plastics exhibit durability in natural settings, resulting in prolonged environmental pollution. The detrimental impacts of plastics on the environment can be classified into five categories, with the degree of severity influenced by the size and shape of the items: ingestion, entanglement, the release of toxic additives and subsequent accumulation of toxins, degradation into microplastics, and impacts on human livelihoods (van Emmerik and Schwarz 2020). Due to the high impact of plastics on ecosystems and humans, regulatory actions have been initiated at international and national levels to reduce plastic emissions (Helm et al. 2023). For instance, in March 2022, the Fifth United Nations Environment Assembly adopted a resolution for an internationally legally binding agreement by 2024 to end plastic pollution in both marine and terrestrial environments.

Initially, attention focused on waste in the marine environment, recognising rivers as significant litter pathways to the oceans (Jambeck et al. 2015; Schmidt et al. 2017; Meijer et al. 2021). However, recent studies suggest that a significant portion of macrolitter pollution remains in rivers for extended periods (Van Emmerik et al. 2022a), intensifying its adverse effects on riverine environments. Studies on macrolitter in European rivers, such as the Thames, Seine, Rhône, Tiber, and Rhine, reveal the prevalence of plastic items in both sub-surface garbage and floating macrolitter. Plastic litter also dominates riverbanks, representing a substantial fraction of macrolitter in various rivers across Europe and globally (Ballerini et al. 2022).

The concern over plastic pollution in river ecosystems arises from its harmful consequences. These include heightened fauna mortality rates from ingestion or entanglement, property damage, diminished livelihoods for river-dependent communities, heightened flood risks due to urban drainage system blockages, and the eventual transport of plastic into the oceans (Lebreton et al. 2017; Meijer et al. 2022). Globally, 9 to 23 million metric tons of plastic waste are emitted yearly into rivers, lakes, and oceans, with an additional 13 to 25 million metric tons in terrestrial ecosystems (Borrelle et al. 2020). Litter items have been observed in every segment of river systems. Recognised sources of such pollution include wastewater treatment plant sewage outlets (Mintenig et al. 2020), recreational activities near riversides (Gasperi et al. 2014), and regions with high levels of urban activities (Carson et al. 2013). Macrolitter from land enters river systems through natural transport processes or direct dumping. Riverine plastic transport encompasses floating items on the water’s surface, suspended plastics throughout the water column, and movement over the riverbed. The mobility of litter within the water column or their (temporary) accumulation depends on factors such as the polymer type of the plastic item, its degree of degradation, and the preceding hydrological conditions. Accumulation takes place in various areas, including biota, sediment, riparian vegetation, and along riverbanks. Macroplastics may contribute to microplastic pollution in rivers as they break down after exposure to ultraviolet light or mechanical forces (Dris et al. 2015).

Despite the evident consequences, a comprehensive understanding of the sources, sinks, and transport mechanisms of riverine macroplastics still needs to be improved (Roebroek et al. 2022). To accurately assess the global transportation of plastic pollution and to efficiently mitigate sources and associated risks, it is imperative to possess a comprehensive understanding of the composition, distribution, origins, transport, fate, and impacts of plastic debris in river ecosystems. Monitoring plastic in riverine environments is crucial for comprehending how plastic is transported and where it accumulates (van Emmerik et al. 2023). Efforts to monitor and mitigate riverbank plastic pollution have increased, but method harmonisation is crucial for meaningful comparisons between programs (Vriend et al. 2022). While some initiatives have been documented in scientific literature, a considerable portion of riverbank litter identification protocols remains unreported. The variability in driving questions, methods, observers, and data output complicates efforts to compare results.

Reliable and frequent observations of plastic litter can inform the development of effective policy measures and mitigation strategies. Long-term monitoring efforts have proven valuable in understanding plastic transport characteristics, such as the identification of beaches as sinks for marine plastic. However, inconsistencies in measurement strategies complicate the fundamental understanding of plastic transport and deposition mechanisms in river systems (Vriend et al. 2020). The European RIMMEL project initiated efforts to align the monitoring of floating plastics in rivers (Gonzalez-Fernandez et al. 2021). More recently (2023), the United Nations Environment Programme (UNEP) issued “Guidelines for Monitoring Riverine Inputs of Marine Litter” as provided in the Working Document UNEP/MED WG.550/14 and supported the development of common guidelines by the four Regional Seas (BSC, HELCOM, OSPAR, and UNEP/MAP). The selection of an appropriate method largely hinges on the research question or overarching monitoring objective on the one hand and the resources and characteristics of the system available on the other (van Emmerik et al. 2022b).

This study shares results on macrolitter occurrence on Italian riverbanks obtained through citizen science initiatives run by the Association for Social Promotion (ASP) Legambiente, providing the first data on this kind of pollution in Italy. It aims to contribute to the harmonisation of riverbank waste monitoring efforts, emphasising the need for systematic data collection to develop effective strategies for decreasing riverine pollution. Despite ongoing initiatives and proposed measures to reduce waste, baseline data on litter items still need to be included for most rivers, including Italian rivers. Due to the high costs associated with employing professionals to monitor river litter, numerous initiatives have opted to engage citizen scientists in riverbank litter sampling. This approach multi-site monitoring areas within a short timeframe at relatively low costs. An additional advantage is the heightened public awareness generated by this participatory effort (Rambonnet et al. 2019).

Macrolitter items were collected on 100 m long stretches on riverbanks (called stations hereafter) parallel to the waterline, considering the band from the waterline to the high-water line (Vriend et al. 2020). The surface of the sampling area was estimated for each site and ranged between 400 and 10,000 m² (Table 1 and Fig. 1). During the surveys, all macrolitter items larger than 2.5 cm in the longest dimension were collected, counted, and categorised in accordance with the ‘MSFD TG10 Masterlist of Categories of Litter Items’ (Hanke et al. 2013). It includes 132 categories grouped by ten material types (artificial polymer materials, chemicals, cloth/textile, food waste, glass/ceramics, metal, paper/cardboard, processed/worked wood, rubber, and unidentified). We added to the masterlist four further categories included in the Joint List of Litter Categories for Marine Macrolitter Monitoring (Fleet et al. 2021) (i.e., J236 - Other items for hygiene and personal care; J237 - Plastic wet wipes; J246 - Paper cotton bud; and J252 - Single-use plastic gloves). Thus, we specifically monitored 136 litter categories. The benefits of employing this system include the detailed characterisation of litter, enabling the generation of more precise and fit-for-purpose monitoring data to support decision-making in waste management (Vlachogianni et al. 2019).

The detection of litter items was carried out by visual observations, and in each station, all visible litter items were collected and counted. The surveys were conducted without disturbing the upper layer of the sampling unit, i.e., without digging to release litter buried in the soil/sand, but litter items that were half under the soil/sand were retrieved. The stations were selected by personnel from local branches of Legambiente who had been trained before conducting the survey. One or two people per site were appointed as responsible for data collection, categorisation, and reporting. Two hundred fifty-one volunteers took part in the sampling and categorisation of litter items. At each station, the data were validated by the trained personnel, and in case of litter items challenging to classify, pictures were taken, and a discussion was followed up with scientific personnel from the Italian Institute for Environmental Protection and Research (ISPRA). Surveys were carried out in the spring between April and June 2021–2023 (Table 1).

Eighteen stations were monitored along 16 rivers from the north to the south of Italy (Fig. 1). They were representative of different environmental conditions, including vegetated and non-vegetated grounds. The stations were subdivided into four groups according to the land use of the surrounding area (i.e., agricultural, urban park, natural and urban, Table 1). To analyse if litter total density differed among the land uses, a Kruskal-Wallis test (H) was conducted.

Table 1

List of the stations performed between 2021 and 2023.
Station	Month	Year	Region	River	Length (km)	Land use	Total litter	Area (m²)	Vegetation	Substrate
S1	April	2021	Campania	Picentino	25	Natural	521	800	Shrubs	Pebbles, gravel
S2	May	2021	Emilia Romagna	Panaro	148	Natural	322	3240	Grass	Sand, pebbles, mud
S3	May	2021	Emilia Romagna	Po	652	Agricultural	1309	1800	Shrubs	Sand, silt
S4	April	2021	Friuli Venezia Giulia	Noncello	15	Urban park	455	1900	Shrubs	Pebbles, gravel
S5	June	2021	Friuli Venezia Giulia	Tagliamento	178	Agricultural	202	10000	Shrubs	Pebbles
S6	May	2021	Lazio	Tevere	406	Urban	1474	1000	Shrubs	Compact soil, grass
S7	April	2021	Umbria	Tevere	406	Urban park	915	3000	Shrubs and grass	Pebbles
S8	April	2022	Emilia Romagna	Po	652	Agricultural	868	400	Shrubs	Silt
S9	April	2022	Emilia Romagna	Reno	211	Natural	294	2500	Shrubs	Sand
S10	April	2022	Lombardia	Ticino	248	Urban park	6237	3000	Shrubs and grass	Sand, pebbles
S11	April	2022	Molise	Trigno	85	Natural	63	500	None	Pebbles, gravel
S12	April	2023	Abruzzo	Sangro	122	Agricultural	81	2800	Shrubs	Pebbles
S13	May	2023	Abruzzo	Vomano	76	Urban park	460	6000	Shrubs and grass	Sand, pebbles
S14	April	2023	Lombardia	Lambro	130	Urban	605	1500	None	Pebbles, gravel
S15	June	2023	Marche	Chienti	91	Urban	536	3000	Shrubs and grass	Sand, pebbles
S16	April	2023	Marche	Esino	90	Agricultural	354	2500	Shrubs	Pebbles, gravel
S17	April	2023	Piemonte	Tanaro	276	Agricultural	289	2750	None	Sand
S18	April	2023	Veneto	Adige	410	Urban	27	1000	Shrubs	Sand

The composition of riverbank litter in station S13 (Fig. 1) was qualitatively compared with the composition of litter on a beach close (1.6 km) to the Vomano river mouth, i.e. “Pineto località Scerne di Pineto” (Fig. 2). This beach was monitored in March 2023 as part of the reference beaches monitored every six months in the framework of the Marine Strategy Framework Directive (MSFD) (Fortibuoni et al. 2021). Litter was detected by visual census. A 100 m transect perpendicular to the coast was monitored to the first barrier (e.g., dunes, streets, other) at the back of the shoreline section. All items larger than 2.5 cm in the longest dimension were collected and counted (Galgani et al. 2023). All the items collected were sorted according to the Joint List of Litter Categories for Marine Macrolitter Monitoring (Fleet et al. 2021) and were converted into the ‘MSFD TG10 Masterlist of Categories of Litter Items’ (Hanke et al. 2013) to allow a direct comparison of sub-categories.

A total of 15,012 litter items were sampled for a median litter abundance of 457 items/100 m (range = 27-6237 items/100 m) and 0.2 items/m² (range = 0.02-2 items/m²). Of the 136 litter item categories considered, only 15 were never found during the study. Half of the items belonged to just four categories: glass bottles, incl. pieces (17%), cigarette butts and filters (14%), plastic pieces 2.5 cm > < 50 cm (11%) and wet wipes (8%). The top ten litter typologies represented 75% of the entire sample. As a whole, artificial polymer materials represented the most common material (overall: 56%, range: 28–98%), followed by glass/ceramics (overall: 20%, range: 0–65%), metal (overall: 11%, range: 0–23%) and paper/cardboard (overall: 6%, range: 0–30%) (Fig. 3).

The median density of litter differed among stations characterised by different land uses in the surroundings, with urban parks showing the highest density (687 items/100 m), followed by urban riverbanks (570 items/100 m), agricultural (321 items/100 m) and natural (308 items/100 m). However, the difference was not statistically significant (KW-H(3, 18) = 3.4883, p = 0.322)) (Fig. 4).

However, a high variability emerged in terms of litter composition among riverbanks, with glass/ceramics overcoming artificial polymer materials in 2 stations (S10 and S12). The mix of materials in riverbank litter differed according to the environmental setting (land use) of the monitoring stations (Fig. 5). In particular, in urban parks, there was a high contribution (33%) of glass/ceramics. The top 3 litter items were, respectively, bottles (including pieces) (30%), cigarette butts and filters (24%) and metal bottle caps, lids & pull Tables (13%). In urban riverbanks, the most common litter item was plastic wet wipes (38%), followed by plastic pieces 2.5 cm > < 50 cm (17%) and textiles (including rags) (10%). Natural riverbanks were mainly characterised by plastic pieces 2.5 cm > < 50 cm (22%), plastic drink bottles > 0.5 l (5%) and construction material (brick, cement, pipes) (4%). Finally, litter on riverbanks in agricultural areas was mainly composed of polystyrene pieces 2.5 cm > < 50 cm (18%), plastic pieces 2.5 cm > < 50 cm (13%) and drink bottles < = 0.5 l (9%).

Half of the litter items found were Single-Use Plastic (SUP) products, i.e., “a product that is made wholly or partly from plastic and that is not conceived, designed or placed on the market to accomplish, within its life span, multiple trips or rotations by being returned to a producer for refill or re-used for the same purpose for which it was conceived” (Directive (EU) 2019/904, Article 3, L155/8).

Litter on the riverbank of the Vomano river (S13) and those of a beach close to the river mouth differed in terms of composition (Fig. 6). Beach litter was dominated by polystyrene pieces (typically related to the fragmentation of fish boxes; Feld et al. 2022) and included items typically from the sea (fishing nets and ropes). Litter on the riverbank was more variegated and included items typically from sewage discharges (wet wipes and condoms; McGoran et al. 2023) as well as from land-based activities such as hunting (shotgun cartridges).

Waste in river systems has a direct impact on human livelihoods by causing economic losses and heightening flood risks in urban areas (van Emmerik and Schwarz 2020). Like its impact on the marine environment, plastic pollution in river ecosystems can harm shipping and transportation vessels (McIlgorm et al. 2011). Plastic debris tends to accumulate on riverbanks, potentially affecting tourism or real estate values. In urban settings, plastic waste is known to obstruct drains and other hydraulic infrastructure (Lebreton and Andrady 2019), thereby increasing flood risks in these areas. Debris accumulating in urban drains leads to a faster increase in water level compared to organic debris (Honingh 2018).

In this study, the overall median total abundance of litter items found on Italian riverbanks was 457 items/100 m (0.2 items/m²). Even if they are entirely different ecosystems, it is worth noting that this median value is like the baseline for Italian beach litter (477 items/100 m) as defined in the framework of the Marine Strategy monitoring program (Fortibuoni et al. 2021). Both values are far from the threshold value of 20 items/100 m set by the Technical Group on Marine Litter to define Good Environmental Status (van Loon et al. 2020). Quantitative direct comparison of the abundance of litter data from other riverbanks is complicated by the fact that existing riverbank measurement methods vary greatly (Vriend et al. 2020). As an example, our baseline value is more than 4-times lower than the density on Durance riverbanks (2,081 items/100 m) in France (Ballerini et al. 2022), while double that in the Dutch Rhine-Meuse delta (206 items/100 m) in the Netherlands (van Emmerik et al. 2020).

The most common materials were plastic (56%), glass (21%) and metal (11%), as it was found – even if in different proportions – in Sardinian rivers (Palmas et al. 2022). The prevalent types of litter observed on Italian riverbanks are glass bottles (and fragments) and cigarette butts and filters. However, many different items were found (some examples are shown in Fig. 7). Glass bottles, cigarette butts and filters, and metal bottle caps, lids & pull tabs were found alongside rivers flowing through urban parks, areas devoted to recreative use. These findings are indeed indicative of potential connections to recreational activities, exacerbated by insufficient environmental education and/or lack of waste bins. Deposits found along riverbanks can originate from various sources and processes. The sources of waste in and around freshwater systems can be directly attributed to human activity, as evidenced by the high correlation between river plastic quantities and factors such as population density, urbanisation, wastewater treatment, and waste management (Best, 2019). They may be intentionally left, as in the case of illegal dumping, accidentally left (Ledieu et al. 2022), or result from recreational activities or sewage discharges (Kiessling et al. 2019; Van Emmerik et al. 2020). Additionally, wind transport and dynamic water body processes can contribute to the formation of litter deposits (Tramoy et al. 2021).

In many rivers, specific point sources have been identified where litter enters the river systems. For instance, in Chilean rivers, several illegal dumping sites were discovered along four rivers across the country (Rech et al. 2015). Mihai (2018) proposed that direct dumping of plastic waste into rivers is the primary source of plastics found in rivers and lakes in the Romanian Carpathians. Regarding major German rivers such as the Rhine, Weber, and Elbe, Kiessling et al. (2019) revealed an evident anthropogenic influence on the presence of litter, as individuals tend to dispose of it intentionally or unintentionally there.

Additionally, there was a notable abundance of wet wipes for personal care and domestic use, in particular along urban riverbanks, and it is plausible that their source is linked to sewage outlets from wastewater treatment plants (Perry et al. 2024). Wet wipes, even those marketed as flushable, are produced using PET (polyethene terephthalate) fibres (Pantoja-Munoz et al. 2018). Consequently, they constitute a significant factor in causing blockages in sewage and wastewater treatment plants (Mitchell et al. 2017). This can lead to the release of water into the environment without undergoing proper filtration or purification processes (Morritt et al. 2014). Consequently, areas with wastewater treatment plants may still discharge wet wipes into rivers, contributing to marine pollution (Balcells et al. 2023).

Indeed, wet wipes ranked fifth among the most common waste in the top marine beach litter items in Europe (Addamo et al. 2017). For this reason, they were targeted by the EU Single-Use Plastics Directive (SUP), which focuses on reducing the environmental impact of certain single-use plastic products. Specifically, the SUP Directive established mandatory harmonised marking specifications for wet wipes in EU Member States, indicating that they should not be flushed down the toilet and that they can harm marine life. They are frequently found in rivers (Kiessling et al. 2019), on beaches (Addamo et al. 2017), and at sea (e.g., Balcels et al. 2023), contributing to environmental and health issues (Lee et al. 2021; Metcalf et al. 2022). A notable example is the substantial accumulation of these items in the River Thames in London, altering the riverbed’s morphology as they amalgamate with and strengthen fine sediments (Shumilova et al. 2019; McCoy et al. 2020). Furthermore, wet wipes break down into microplastics (Lee et al. 2021), which get eaten by wildlife (e.g., McCoy et al. 2020), causing them physical harm and potentially starvation (Anastasopoulou and Fortibuoni 2019).

From the comparison of litter on the riverbank of the Vomano river close to the river mouth and litter on a beach close by, it emerged that litter sources are substantially different. Along the river, the most common litter category was construction material (such as bricks, pipes, etc.), probably deriving from illegal dumping and with low mobility being generally heavy items. The second litter typology in terms of density was wet wipes, whose source is mainly related to sewage discharge. Even if they were found also on the beach close to the river mouth, a large part of them do not reach the coastline, being trapped in the riparian vegetation (Cesarini and Scalici 2022). Other abundant litter categories related to sewage discharge found along the river were medical/pharmaceutical containers (abundant also on the beach) and condoms. Shotgun cartridges were plentiful along the river, indicating the presence of hunting activity in the area. Conversely, on the beach, fishery-related items were abundant, such as nets and ropes and polystyrene pieces derived from the fragmentation of fish boxes.

Examining temporal trends in macrolitter abundance is crucial for assessing the effectiveness of current environmental regulations, such as the EU Marine Strategy Framework Directive (MSFD, 2008/56/EC) and the SUP Directive at the national level in Italy. It also serves as a means to advocate for localised initiatives aimed at identifying point sources (e.g., illegal dumping sites and/or litter hot spots) and minimising the dispersal of litter in the environment. Furthermore, it is necessary to establish a baseline to assess the effectiveness of a policy regarding the quantity of specific items detected within a river basin (Vriend et al. 2020). The EU MSFD mandates a reduction in marine litter, with the European Plastic Strategy (COM/2018/028 final) establishing an ambitious target of a 30% reduction. Data on litter abundance should be collected over periods ranging from 3 to 5 years, depending on the required precision, to establish baseline estimates with sufficient accuracy for detecting changes over time (Schulz et al. 2019).

Collecting data on macrolitter is resource-intensive, and citizen science emerges as a cost-effective method for this purpose (Kiessling et al. 2019). Previous studies demonstrated that the overall litter item abundance reported by citizen scientists aligns well with that reported by professional researchers, emphasising the value of citizen science (e.g., Rech et al. 2015; Zorzo et al. 2021). Data obtained through citizen science can inform local decision-making and supplement monitoring programs (e.g., Vlachogianni et al. 2019), especially in areas where such programs are scarce or non-existent, such as Italy for river litter. Continuous advancements are underway in the development of new citizen science data collection tools and technologies. For instance, straightforward smartphone-based applications enable the collection of various data types, such as the RIMMEL app for floating river litter (González-Fernández and Hanke 2017; Crosti et al. 2018) or the Litterati app (www.litterati.org), which facilitates the identification and tagging of waste items from any location worldwide.

Despite the small spatial and temporal scales covered by this study, even limited data can be invaluable when no other data are available (Owens and Kamil, 2020). The data obtained in this study mark the initial available information on the quantity and types of litter items on the riverbanks of Italian rivers. These findings can contribute to the formulation of targeted policies and interventions for litter prevention, mitigation, and reduction of the most prevalent litter items. Furthermore, they can be instrumental in assessing the effectiveness of implemented measures to combat plastic pollution (van Emmerik et al. 2019; González-Fernández et al. 2021). Future studies might enhance spatial and temporal resolution, considering hydrological variations to account for extreme events such as floods (Tramoy et al. 2022; van Emmerik et al. 2022a). This approach would provide valuable data for quantifying the emission of litter items into the Mediterranean Sea.

The baseline data collected for sixteen riverbanks in Italy in this research provides crucial data for managers to develop reduction and mitigation measures to preserve river ecosystems from pollution. We propose that, in addition to adhering to EU and Italian national regulations, municipalities can promptly act to combat plastic pollution. This involves targeting the prevalent litter items along the riverbanks through initiatives such as green public procurement and territorial animation. Cost-effective monitoring of litter items and the evaluation of the efficacy of environmental regulations in reducing plastic pollution could be conducted through future surveys using citizen science. Van Emmerik et al. (2022b) proposed a roadmap for the design of a national riverine macroplastic monitoring strategy that policymakers can use to define and prioritise specific projects that are necessary to answer the locally relevant questions.

The study reveals that Italian riverbanks exhibit a substantial abundance of litter items, with plastic, glass, and metal being the most common materials. The sources of waste in and around freshwater systems are diverse and can be attributed to human activity, including illegal dumping, accidental littering, recreational activities, and sewage discharges. Specific point sources of litter entry into river systems have been identified worldwide, highlighting the need for targeted interventions and policy measures.

Wet wipes emerge as a significant concern, particularly along urban riverbanks, with their source linked to sewage discharge from wastewater treatment plants. Despite being marketed as flushable, wet wipes contribute to blockages in sewage systems, leading to environmental and health issues. Their accumulation in rivers, beaches, and seas underscores the importance of regulatory measures such as the EU Single-Use Plastics Directive.

Temporal trends in macrolitter abundance are essential for assessing the effectiveness of environmental regulations and advocating for localised initiatives to minimise litter dispersal. This study represents a first baseline against which to compare future trends. Citizen science emerges as a cost-effective method for collecting litter data, supplementing monitoring programs, and informing decision-making. However, the number of sites monitored at the moment needs to be increased to obtain a more comprehensive view of the problem.

The baseline data collected for Italian riverbanks provides the first crucial information for developing reduction and mitigation measures to preserve river ecosystems from pollution. Municipalities can take proactive steps to combat plastic pollution, including targeted initiatives and cost-effective monitoring through citizen science. A roadmap for the design of a national riverine macroplastic monitoring strategy can aid policymakers in defining and prioritising projects to address locally relevant challenges.

Acknowledgements

We want to thank all the citizen scientists who took part in the litter sampling on riverbanks. In particular, we thank the following ASP Legambiente groups: Circolo Legambiente Picentini “Arcadia”, Circolo di Legambiente Modena “Angelo Vassallo”, Legambiente Ferrara “Il Raggio Verde”, Circolo Legambiente di Pordenone “Fabiano Grizzo”, Circolo Legambiente Medio Friuli, Legambiente Lazio, Circolo Legambiente “Azzaruolo” Jesi, Circolo Legambiente Perugia e Valli del Tevere, Circolo Legambiente Bologna, Circolo “Alexander Langer” di Monza, Circolo Legambiente Sesto Calende, Legambiente Molise, Legambiente Geo APS di Atessa, Legambiente Costa Teramana, Circolo Legambiente “il Pettirosso” di Tolentino, Circolo di Legambiente Langhe e Roero, and Legambiente Verona.

Ethical Approval

Not applicable

Consent to Participate

Not applicable

Consent to Publish

Not applicable

Author Contributions

TF: Conceptualisation; TF, ES, SD: Data curation; TF: Formal analysis; ES, SD: Funding acquisition; TF, ES, SD: Methodology; TF: Writing—original draft; TF, ES, SD: Writing—review and editing.

Funding

The authors declare that no funds, grants, or other support were received during the preparation of this manuscript.

Competing Interests

The authors have no relevant financial or non-financial interests to disclose.

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Preliminary Assessment of Waste Accumulation along Riverbanks in Italy

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