Estimating a regional budget of marine plastic litter in order to advise on marine management measures

Seasonal change in fate and transport of plastics from Red River to the coast of Vietnam

A Lagrangian-particle tracking model, Delft3D-PART, combined with hydrodynamics models are used to investigate the fate and transport of buoyant plastics from Ba Lat river mouth in Red River Delta, northern Vietnam. It was found that during the dry season (Dec-Feb), 23 % (26.43 ton) of the plastics reached the shoreline while 76.1 % (68.3 ton) moved towards the coast further south of Red River Delta. During the wet season (Jun-Aug), 42 % (56.3 ton) were transported offshore away from the coast and 20 % (26.43 ton) distributed along the shore. The two bays adjacent to the river mouth are major hotspots with the intensity skewed towards the upwind side relative to the seasonal monsoon. This phenomenon is exacerbated by storm events which reverse the typical transport and lead to formation of hotspots at the upwind side of the plastic source. Guidance of model results for targeted cleanup operations is discussed.

Investigating local trawl fishing as a source of plastic beach litter

This paper uses a particle tracking model to simulate the distribution of fishing-related marine-sourced plastic litter from demersal trawling activities along the Atlantic coast of Scotland. The modelled fishing litter dispersed widely across the region, with ∼50% of the particles beaching along the northwestern Scottish coast after a year-long simulation. The model was tuned using observations of beached litter loadings along the same coastline to estimate the annual input, by mass, of small (<1 kg) plastic litter. Model results suggest that between 107 g and 280 g of small fishing-related litter enters the ocean per hour of fishing, resulting in an estimated 234 t to 614 t of small fishing-related litter entering the ocean annually on the Scottish west coast. These results suggest that fishing on the Atlantic coast of Scotland may be a significant source of marine plastic. However, more modelled and observational data are required to reduce uncertainty.

Coastal groynes reduce beach litter accumulation along the East coast of England

Anthropogenic marine litter (AML) is a global environmental concern. One of the most conspicuous effects of AML is beach litter accumulation, the distribution of which is typically heterogenous. Little information is available on the potential effects of coastal topographic features on litter dispersal. We analysed the abundance, composition, and sources of beach litter on the East coast of England in relation to the presence of coastal groyne structures. Six beaches were surveyed in autumn and winter 2021 using the OSPAR methodology for monitoring beach litter. Litter abundance was lower on beaches with groynes present, which could infer that groynes deflect or bury AML. The presence of groynes had no significant effect on the composition/sources of beach litter. Single-use plastic packaging, fishing waste, and sewage-related debris were the largest contributors of beach litter in this region. Our findings indicate that man-made topographic features may affect marine litter dispersal and coastal accumulation.

Model-based estimation of seasonal transport of macro-plastics in a marine protected area

Management of plastic litter in Marine Protected Areas (MPAs) is expensive but crucial to avoid harms to critical environments. In the present work, an open-source numerical modelling chain is proposed to estimate the seasonal pathways and fates of macro-plastics, and hence support the effective planning and implementation of sea and beach cleaning operations. The proposed approach is applied to the nearshore region that includes the MPA of Capo Milazzo (Italy). A sensitivity analysis on the influence of tides, wind, waves and river floods over the year indicates that seasonality only slightly affects the location and extension of the macro-plastic accumulation zones, and that beach cleaning operations should be performed in autumn. Instead, the influence of rivers on plastic litter distribution is crucial for the optimal planning of cleaning interventions in the coastal area.

Assessment of beach macrolitter using unmanned aerial systems: A study along the Bulgarian Black Sea Coast

Over the years, the Black Sea has been impacted by the issue of marine litter, which poses ecological and health threats. A mid-term monitoring program initiated in 2018 assessed the abundance, density, and composition of beach litter (BL) on 40 frequently visited beaches. From 2018 to 2022, there was a significant increase in average abundance, rising by 261 %. Artificial polymer materials accounted for the majority (84 %) of the litter. Land-based sources dominated 77 % of the litter. The Clean Coast Index (CCI) categorized the beaches as "moderate" with an average value of 8.9 for the period between 2018 and 2022. However, the years 2021 and 2022, during the COVID-19 epidemic, were identified as the "dirtiest period" with 11 beaches classified as "extremely dirty" due to high domestic tourist pressure. The study demonstrates a successful combination of standard in situ visual assessment supported by unmanned aerial systems for beach litter surveys.

Modelled and observed plastic pollution on remote Scottish beaches: The importance of local marine sources

Beach-cleans conducted on the west coast of Scotland investigated the distribution of land- and marine-sourced litter and compared these with a particle tracking model representing the presumed principal land-based source. Modelled particles dispersed widely, even reaching the remote northwest coast, with 'hotspots' and 'coldspots' on windward and leeward coasts respectively. In beach sampling, however, land-sourced litter represented only 19% of items by count and 8% by weight, while marine-sourced litter represented 46% by count and 62% by weight. The source of the remainder could not be identified. Windward coasts had an average count of 1859 litter items per 100 m, and weight of 14,862 g per 100 m. Leeward coasts had an average count of 32 litter items per 100 m and weight of 738 g per 100 m. Field observations and model predictions were consistent in many respects for land-sourced litter, however marine-sourced litter is dominant on many coastlines.

River export of macro- and microplastics to seas by sources worldwide

Seas are polluted with macro- (>5 mm) and microplastics (<5 mm). However, few studies account for both types when modeling water quality, thus limiting our understanding of the origin (e.g., basins) and sources of plastics. In this work, we model riverine macro- and microplastic exports to seas to identify their main sources in over ten thousand basins. We estimate that rivers export approximately 0.5 million tons of plastics per year worldwide. Microplastics are dominant in almost 40% of the basins in Europe, North America and Oceania, because of sewage effluents. Approximately 80% of the global population live in river basins where macroplastics are dominant because of mismanaged solid waste. These basins include many African and Asian rivers. In 10% of the basins, macro- and microplastics in seas (as mass) are equally important because of high sewage effluents and mismanaged solid waste production. Our results could be useful to prioritize reduction policies for plastics.

Sources of marine debris for Seychelles and other remote islands in the western Indian Ocean

Vast quantities of debris are beaching at remote islands in the western Indian Ocean. We carry out marine dispersal simulations incorporating currents, waves, winds, beaching, and sinking, for both terrestrial and marine sources of debris, to predict where this debris comes from. Our results show that most terrestrial debris beaching at these remote western Indian Ocean islands drifts from Indonesia, India, and Sri Lanka. Debris associated with fisheries and shipping also poses a major risk. Debris accumulation at Seychelles is likely seasonal, peaking during February-April. This pattern is driven by monsoonal winds and may be amplified during positive Indian Ocean Dipole and El-Niño events. Our results underline the vulnerability of small island states to marine plastic pollution, and are a crucial step towards improved management of the issue. The trajectories used in this study are available for download, and our analyses can be rerun under different parameter choices.

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.

Microplastics contamination in commercial fish from Alexandria City, the Mediterranean Coast of Egypt

Plastic waste is a major threat to various marine ecosystems. Due to being semi-enclosed basin with dense population, the Mediterranean Sea has been considered as a hot spot for plastic pollution. Alexandria was listed as one of the major cities contributing to plastic waste in the eastern Mediterranean basin. Accordingly, microplastics (MPs) abundance and composition were investigated in the digestive tracts of commercial fish species from two major fishing areas in Alexandria; Abu-Qir Bay and Eastern Harbor, which are affected by plastic pollution. The incidence and average densities of MPs were 91.8 ± 8.4% and 11.7 ± 9.5 items fish^-1, similar to highly polluted regions in the southeastern Mediterranean Sea. The average MPs concentration was significantly higher in Sparus aurata (38.3 ± 28.4 items fish^-1) than all species, except for Siganus rivulatus and Boops boops. Polyethylene and poly ethylene-vinyl acetate were the dominant polymers in the fish digestive tracts. Four types of plastic polymers were recorded in Siganus rivulatus and five in Parupeneus macronemus. The dominance of glossy fragments (sizes <500 μm) in Abu-Qir Bay indicated land-based source of pollution from domestic, agricultural, and industrial wastes. The dominance of larger plastic filaments and colored fragments in the Eastern Harbor suggested secondary MPs, originating from the fragmentation of larger plastic items of sea-based sources, such as fishing and recreational activities.

Impacts of the COVID-19 pandemic restrictions on solid waste pollution in the worldwide iconic Copacabana Beach (Rio de Janeiro, Brazil)

Total and partial restrictions to beach access during COVID-19 pandemic created an opportunity to evaluate its effect on coastal pollution. We aimed to determine the impact of access restrictions on solid waste pollution at Copacabana beach, Brazil. Solid waste amount was analyzed considering beach access restrictions: unrestricted, total closure, partial restriction, new normal. Relationships of atmospheric temperature and precipitation with access restrictions were assessed and confounding effects controlled for further analyses. Beach access restrictions significantly reduced solid waste pollution at Copacabana beach, beach closure reduced waste amount in 72 %. Partial restrictions and new normal periods have significantly reduced solid wastes amount on the beach in 60 % and 36.88 %, respectively. Qualitative data revealed that most of solid wastes were single-use plastics recently disposed at Copacabana beach, reflecting beachgoer's effects on waste left on the beach. A positive impact of COVID-19 pandemic restrictions was detected on solid waste pollution at Copacabana beach.

Order Management and Completion Date Prediction of Manufacturing Job-Shop Based on Deep Learning

To cope with the volatility of customer order demand, enterprises need to formulate a reasonable production plan based on customer demand for the completion period and their current manufacturing capacity. The existing studies have not fully considered the complex processing procedures, the features of manufacturing attributes, and the repetitive orders of stable consumers. To solve these problems, this paper explores the order management and completion date prediction of manufacturing job-shop based on deep learning. Specifically, the features of manufacturing attributes were extracted and used to predict the activities and completion time of different manufacturing tasks in order management. In addition, a deep learning prediction model was constructed based on a bidirectional long short-term memory network (BiLSTM) and self-attention mechanism, which completes the order management and completion date prediction.

Sources of marine litter along the Bulgarian Black Sea coast: Identification, scoring and contribution

The sources of marine litter (ML) pollution along the Bulgarian Black Sea coast in 2019 were identified and categorized to: Public litter, Fishing, Shipping, Sanitary and sewage, Fly tipped, Medical and Non-sourced, following Veiga et al., 2016 approach. Largest was the contribution of Public litter - 48.3% and Non-sourced - 38.5% of the total. Most Public litter items were attributed to recreational activities - 82.9% Public litter Recreation and less to Public litter Smoking-related - 17.1%. Regarding to Non-sourced, the following sub-categories seemed to contribute clearly more: Land (run off) - 8.79% and Tourism beach users - 8.58%. Considerably lower was the contribution of Fishing, Offshore and Shipping. None of the items were attributed to Sewage related. The ML pollution on the individual beaches (10 sites) exhibited largest contribution of Public litter with most significant input of Public litter Recreation, varying from 65.9 to 86.7% between beaches.

Standing stock and mass balance of marine litter in the Seto Inland Sea, Japan

The basin of Seto Inland Sea has a population of 31 million people. The standing stock and mass balance of marine litter in this area was estimated using rapid assessment for beach litter, questionnaire surveys on removed amounts of marine litter, and existing data. The mass balance of marine litter was explained by using a single box model, assuming complete mixing and uniform density. If the standing stock of drifting and beach litter combined was 3400 tons, the inflow of litter from rivers was 3000 tons/year, generation of litter at sea was 1200 tons/year, and inflow from the open sea was 300 tons/year. The amount of marine litter removed from the beach and sea surface was 1400 tons/year, outflow to the open sea was 2400 tons/year, and deposition on the sea bottom was 700 tons/year.

Microplastics in sea surface waters around Scotland

This is the first regional, multi-annual assessment of floating microplastics in Scotland's seas. Sea surface samples were collected from 2014 to 2020, using a catamaran swimmer body/neuston net trawl and evaluated for the presence of microplastics. Microplastics were present in the surface waters of all Scottish Marine Regions (SMR) and Offshore Marine Regions (OMR) though almost 35% of sample sites contained no microplastics. Concentrations ranged from 0 to 91,128 microplastics km^-2 sea surface. Potential hotspots were identified in the Clyde (0-77,168 microplastics km^-2), Forth & Tay (0-83,729 microplastics km^-2) and the Solway (607-91,128 microplastics km^-2). Fragmented plastics accounted for almost 50% of the microplastics recovered and this may suggest that the microplastics in Scotland's seas are predominantly from the breakdown of larger items. Due to the variable geographic and temporal extents of the data it was not possible to carry out a trend assessment.

Fouling organisms in marine litter (rafting on abiogenic substrates): A global review of literature

One of the underestimated consequences of marine litter presence on marine environment is the transportation of fouling species on detritus - a process known as rafting. We undertook a review of articles concerning rafting published between 1970 and 2020 to identify patterns and potential areas of study that could contribute to directing future research. We observed in 53 publications an increase in rafting studies from the 1990s but fewer studies have been undertaken in the Southern Atlantic. The main fouling organisms were algae, barnacles, bryozoans, mollusks and polychaetes. The transport of those organisms over time and distances, and the volumes of material transported, have been very irregular, reflecting oceanic movements and detritus generating events acting at local, regional, or trans-oceanic scales. No standardized methodologies for collecting marine litter and identifying and quantifying their fouling were observed, but are suggested in this review, to allow more accurate future comparisons among different studies.

First marine litter survey on beaches in Solomon Islands and Vanuatu, South Pacific: Using OSPAR protocol to inform the development of national action plans to tackle land-based solid waste pollution

The increasing abundance of marine litter is impacting the environment, human health and economies in the South Pacific. Small Islands Developing States are particularly affected by marine litter, primarily due to insufficient waste management systems. For the first time, marine litter was quantified and characterised on 13 beaches in Solomon Islands and Vanuatu in the South Pacific region using the OSPAR beach litter monitoring guidelines. A total of 1053 (±1017) and 974 (±745) items of litter per 100 m beach were recorded in Solomon Islands and Vanuatu respectively. Litter composition and distribution show that the majority of the litter comes from local land-based sources and large quantities of fragments and single use plastics were found by cities and river mouths. Actions to reduce single use plastic, improve collection, reuse and recycling, together with outreach campaigns would reduce marine litter significantly in these countries. Furthermore, there is great potential to develop a more circular economy to manage the substantial quantities of recyclable items that were found stranded on the beaches.

How litter moves along a macro tidal mid-latitude coast exposed to a coastal current

A simplified particle-tracking model with an idealised coastline was used to investigate how the interaction between variable winds and water level (VaWWL) operates spatially along a coast. The model included a constant along-coast current, horizontal diffusion, onshore/offshore wind drift, beach/cliff combinations and point/distributed litter sources. The default model reproduced basic properties of observed beach litter loadings (zero net accumulation, negatively skewed loading distributions) and the observed spatial pattern along the Scottish east coast, with average loadings increasing in the coastal current direction. The VaWWL effect moved the along-coast flux of floating litter offshore as debeaching events occur during offshore winds. Varying diffusion, coastal current speed, windage, beach/cliff combinations and different foreshore boundary conditions were investigated. Reconciling model predictions with previous estimates of plastic inflow suggested sinking rates of up to 90% soon after first entry into the sea. The VaWWL effect offers a realistic boundary condition for particle-tracking models.

The Way of Macroplastic through the Environment

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.