Litter in French urban areas - Part 2: transport dynamic and fluxes in stormwater.

Urban areas constitute a major hotspot of litter, including plastic litter, that stormwater can wash off towards waterways. However, few studies quantified and characterized litter densities in urban areas and fluxes transported by stormwater networks. Moreover, little information is available on litter transport dynamics in stormwater, and on the factors driving this transport. This study aims at characterizing and quantifying litter amounts transported by stormwater of two nested French urban catchments (total surface area of 105 ha). Litter densities relative to land uses and rain events were investigated in the same catchments as in a compagnon paper (Ledieu et al., 2024). The present study explores the impact of rain events on the transport of urban litter in stormwater. Litter collection and characterization combined with a capture/recapture experiment using tagged litter placed in stormwater inlets show total litter fluxes of 29 kg/year, in which 14 kg/year are plastics, exported at the stormwater outlet. These fluxes confirm that stormwater runoff is a considerable pathway from urban surfaces to waterways, especially regarding small plastic litter (< 2.5 cm). Item transport dynamic is however not linear and only 0.3% of the urban litter appear remobilized. Litter transport dynamics depends on several factors (urban litter densities, hydrometeorological parameters, item composition and morphologies, and stormwater management systems) that should be considered in global models.

Macrolitter and microplastics along the East Pacific coasts - A homemade problem needing local solutions.

The East Pacific (EP) region, especially the central and southern EP, has been fairly less studied than other world's regions with respect to marine litter pollution. This comprehensive literature review (257 peer-reviewed publications) showed that both macrolitter (mostly plastics) and microplastics tend to accumulate on EP shorelines. Moreover, they were also reported in all the other compartments investigated: sea surface, water column, seafloor and 'others'. Mostly local, land-based sources (e.g., tourism, poor waste management) were identified across the region, especially at continental sites from low and mid latitudes. Some sea-based sources (e.g., fisheries, long-distance drifting) were also identified at high latitudes and on oceanic islands, likely enhanced by the oceanographic dynamics of the EP that affect transport of floating litter. Our results suggest that effective solutions to the problem require local and preventive strategies to significantly reduce the levels of litter along the EP coasts.

What lies underneath: Comparison among beach litter in the underwater bathing area and exposed beach.

The standard techniques for monitoring beach litter focus on the litter that is accumulated on beaches. Therefore, the underwater bathing area is usually overlooked. Our study aims to start the discussion about the litter in the bathing area, an important connection between the exposed beach and the ocean. We aimed to compare sampling methodologies between the underwater bathing area and the exposed beach. We highlighted litter's similarities and differences regarding the amount, material, possible sources, and interaction with the biota. We also performed a brand audit on the underwater bathing area litter. In the underwater region, 106 items were collected while 1706 items were collected from the exposed beach region. Plastic was the dominant type of material in both sites, exposed beach (89.92 %) and bathing area (83.96 %). The litter's possible source was different. In the underwater bathing area was more related to food packages (couscous, rice). On the other hand, litter on the exposed beach was associated with beach use (single-use plastic such as plastic cups). The brand audit identified 21 companies, whereby most brands were Brazilian and food-related. Regarding interactions with the biota, the litter in the bathing area had more bio-fouling (87.73 %) than the litter collected on the exposed beach (10.00 %). Information about bathing area litter can be useful to draw different management strategies. Due to the differences in litter types and behavior between the two sites, the same mitigation strategies might not be equally efficient.

Oceanographic and anthropogenic variables driving marine litter distribution in Mediterranean protected areas: Extensive field data supported by forecasting modelling.

Marine litter concentration in the Mediterranean Sea is strongly influenced both by anthropogenic pressures and hydrodynamic factors that locally characterise the basin. Within the Plastic Busters MPAs (Marine Protected Areas) Interreg Mediterranean Project, a comprehensive assessment of floating macro- and microlitter in the Pelagos Sanctuary and the Tuscan Archipelago National Park was performed. An innovative multilevel experimental design has been planned ad-hoc according to a litter provisional distribution model, harmonising and implementing the current sampling methodologies. The simultaneous presence of floating macro- and microlitter items and the potential influences of environmental and anthropogenic factors affecting litter distribution have been evaluated to identify hotspot accumulation areas representing a major hazard for marine species. A total of 273 monitoring transects of floating macrolitter and 141 manta trawl samples were collected in the study areas to evaluate the abundance and composition of marine litter. High mean concentrations of floating macrolitter (399 items/km2) and microplastics (259,490 items/km2) have been found in the facing waters of the Gulf of La Spezia and Tuscan Archipelago National Park as well in the Genova canyon and Janua seamount area. Accordingly, strong litter inputs were identified to originate from the mainland and accumulate in coastal waters within 10-15 nautical miles. Harbours and riverine outfalls contribute significantly to plastic pollution representing the main sources of contamination as well as areas with warmer waters and weak oceanographic features that could facilitate its accumulation. The results achieved may indicate a potentially threatening trend of litter accumulation that may pose a serious risk to the Pelagos Sanctuary biodiversity and provide further indications for dealing with plastic pollution in protected areas, facilitating future management recommendations and mitigation actions in these fragile marines and coastal environments.

Beach litter contamination of the Turkish middle Black Sea coasts: Spatial and temporal variation, composition, and possible sources.

Marine litter is one of the biggest environmental problems nowadays. Sinop, is located in the heart of Türkiye's Black Sea coast, has a small population, and is a popular fishing and tourist destination. In this study, marine litter amount, composition, and possible sources were investigated, and seasonal comparisons were made between in Sinop beaches. Marine litter amount was found as 0.29-7.67 items·m-2 and 3.46-49.09 g·m-2 and beaches were classified as moderate to extremely dirty. Plastics were the highest ratio (88.14-98.46 %) and "plastic pieces 2.5> <50 cm" were the major litter type. The major possible litter source was improper waste disposal (33.36 %) and litter items originated from mainly land-based sources (74.13 %). The result of this study shows that there is a significant litter problem on the coasts. The solution of this problem can be possible to take rational measures against marine litter pollution with education and management policies.

Mountain streams flushing litter to the sea - Andean rivers as conduits for plastic pollution.

Rivers polluted by anthropogenic litter are major transport routes of litter from inland to the coastal zone and the ocean. However, litter studies have primarily focused on marine environments, and the litter dynamics in rivers are still poorly understood. Herein, we explored the abundances, composition and sources of litter at the riversides and in surface waters of mountain rivers from continental Chile in two different years. Additionally, we evaluated whether different temporal, geographic, topographic, hydrologic or anthropogenic factors influence the abundances of litter. Anthropogenic litter was prevalent in Chilean rivers, both at the riversides and in surface waters. Average abundances of riverside litter, floating macrolitter, and small floating plastics were 1.8 items m-2, 10.1 items h-1 and 5.8 items h-1, respectively, and abundances were generally higher in northern Chile. Plastics dominated in all compartments, comprising 29% of riverside litter and more than 70% of small floating litter, but other litter categories were also present at riversides. Sources of litter in Chilean rivers were mostly local, such as recreational visitors, residents, and illegal dumping, and there were no clear effects of the different tested factors on the abundances of litter. Litter densities in surface waters were low compared to those in lowland slow-flowing rivers in other countries, suggesting that retention of litter is limited in the highly dynamic and rapidly flushing mountain rivers, and thus most litter (primarily plastics) is transported directly to the sea. The results suggest that to adequately address this problem in Chile, prevention measures should be aimed at the identified local sources, by means of education, public policies, legislation, and enforcement.

Marine plastic litter: public perceptions and opinions in Italy.

Understanding public perceptions, opinions and knowledge about marine plastic litter issue is a critical step in effectively engaging society and changing human behaviour in order to reduce litter inputs. The study performs a segmentation analysis that jointly considers opinions about sources and impacts of a sample of 605 Italians with a twofold objective: i. to identify homogeneous segments of people according to the importance they attach to different sources and impacts of plastic litter; ii. to understand if behavioural aspects and personal characteristics emerged for each cluster of people. Gender, education and living areas significantly affect respondents' opinions, knowledge and behaviour. A high level of awareness and concern emerged. Four clusters- "the silent majority", "the least concerned and involved", "the little conscious of litter sources", and "the most severe and committed"-, reveal the heterogeneity of people's profiles. Policy implications in terms of knowledge, education and behaviour for reducing marine plastic pollution are discussed.

Composition, abundance and sources of anthropogenic marine debris on the beaches from Ecuador - A volunteer-supported study.

This study represents an inter-institutional effort that was supported by more than 400 volunteers. We sampled Anthropogenic Marine Debris (AMD) on 26 beaches, including one beach from Galapagos Islands. AMD was mainly composed of plastics (>60%), followed by cigarette butts, paper and metal. Average AMD density on the continental beaches was 1.31 ± 1.03 items m-2 (mean ± SD). AMD densities and the proportion of plastics were higher on some beaches located on the Gulf of Guayaquil, suggesting that many of the plastic items found on these beaches were, likely, drifted by the swift currents of the Guayas River. Additionally, the overall results indicate that most litter on continental beaches from Ecuador has local sources. Recommendations include marine pollution education and public awareness campaigns to reduce the consumption of plastic bags, as well as a ban on harmful single-use plastics.

Assessment of seabed litter in the Northern and Central Adriatic Sea (Mediterranean) over six years.

Seabed debris is much less investigated in respect to the sea surface and shores due to sampling difficulties and costs. However, detecting marine benthic litter is fundamental for developing policies aimed at achieving the Good Environmental Status in European Seas by 2020, as requested by the Marine Strategy Framework Directive. This study estimates seafloor litter abundance, composition, spatial distribution and main sources in the North-Central Adriatic Sea (FAO GSA 17) over a six-year period (2011-2016) with 67 stations sampled per year, representing the longest data set for the basin. Litter items collected using a "rapido" trawl were classified in six major categories. The average density of the litter collected over six years was 102.66 ±â€¯41.91 kg/km2. The highest concentration of litter was found in stations close to the coast within 30 m depth with a mean weight of 142.90 ±â€¯27.20 kg/km2, while the lowest value was recorded between 30 and 50 m of depth (41.12 ±â€¯9.62 kg/km2). Plastic was dominant followed by metal and other litter materials. Lost fishing nets and mussel culture debris accounted for 50% of the overall plastic litter collected. These data and the systematic monitoring of marine litter provide useful information to implement necessary measures to manage marine litter and minimize this type of anthropogenic pollution in the Adriatic region.

Inter-hemispherical shoreline surveys of anthropogenic marine debris - A binational citizen science project with schoolchildren.

Anthropogenic marine debris (AMD) is a global problem and the identification of its sources is essential for adequate mitigation strategies. Herein we examined whether AMD density and composition differed between two countries with contrasting socio-economic backgrounds and marine litter sources (i.e. Chile and Germany). In nationwide beach litter surveys, we used a citizen science approach with schoolchildren and their teachers. Litter densities were substantially higher in Chile than in Germany. The different geographic zones surveyed in both countries showed strong grouping tendencies according to their main economic activities (tourism, shipping, fisheries/aquaculture), major litter sources, and AMD composition, in terms of dominance and diversity of AMD types. The results suggest that beach litter composition can be used as a simple proxy to identify AMD sources, and also that law enforcement and education can help mitigate the problem; however, for efficient solutions, production and consumption of plastics must be reduced.

Seabed litter composition, distribution and sources in the Northern and Central Adriatic Sea (Mediterranean).

Detecting the origin of marine benthic litter is fundamental for developing policies aimed at achieving the Good Environmental Status in European Seas by 2020, as requested by the Marine Strategy Framework Directive (MSFD). The abundance and composition of benthic litter in the Northern and Central Adriatic Sea were investigated at 67 stations with bottom trawl nets. Average density of benthic litter was 913±80items/km2, ranking the Adriatic as one of the most polluted basins worldwide. Plastic was dominant in terms of numbers (80%) and weight (62%), and mainly consisted in bags, sheets and mussel nets. Higher quantities of litter were found in coastal areas, especially in front river mouths, coastal cities and mussel farms. In deep waters, litter hotspots were associated with most congested shipping lanes, indicating an additional litter input to the basin. Benthic litter composition resulted to be largely driven by the vicinity to local sources, i.e. mussel farming installations and most congested shipping routes. These findings provide useful insights to set measures to manage marine litter in the Adriatic region, and possibly to minimize this anthropogenic pollution.