Litter Transport Research Articles

A Laboratory Study of the Effects of Size, Density, and Shape on the Wave‐Induced Transport of Floating Marine Litter

AbstractFloating marine litter is transported by several mechanisms, including surface waves. In studies of marine litter transport, the wave‐induced drift is set to be equal to the Stokes drift, corresponding to the Lagrangian‐mean wave‐induced drift of an infinitesimally small tracer. Large‐scale experiments are used to show how the wave‐induced drift of objects of finite size depends on their size, density, and shape. We observe increases in drift of 95% compared to Stokes drift for discs with diameters of 13% of the wavelength, up to 23% for spheres with diameters of 3% of the wavelength, whereas drift is reduced for objects that become submerged such as nets. We investigate what these findings may imply for the transport of plastic pollution in realistic wave conditions and we predict an increase in wave‐induced drift for (very) large plastic pollution objects. The different extrapolation techniques we explore to make this prediction exhibit a large range of uncertainty.

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 105ha). 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 29kg/year, in which 14kg/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 (< 2.5cm). 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.

Transport and accumulation of litter in submarine canyons: a geoscience perspective

Marine litter is one of the most pervasive and fast-growing aspects of contamination in the global ocean, and has been observed in every environmental setting, including the deep seafloor where little is known about the magnitude and consequences of the problem. Submarine canyons, the main conduits for the transport of sediment, organic matter and water masses from shallow to abyssal depths, have been claimed to be preferential pathways for litter transport and accumulation in the deep sea. This is supported by ongoing evidence of large litter piles at great water depths, highlighting efficient transfer via canyons. The aim of this article is to present an overview of the current knowledge about marine litter in submarine canyons, taking a geological, process-based point of view. We evaluate sources, transport mechanisms and deposition of litter within canyons to assess the main factors responsible for its transport and accumulation in the deep sea. Few studies relate litter distribution to transport and depositional processes; nevertheless, results from available literature show that canyons represent accumulation areas for both land-based and maritime-based litter. Particularly, accumulation of fishing-related debris is mainly observed at the canyon heads and walls and is related to fishing activities carried out in and adjacent to canyons, while transport and accumulation of general waste and plastic along canyon axes can be related to different mechanisms, encompassing enhanced bottom currents, dense water cascading and turbidity currents, and is related to the proximity of canyons to shore. Global assessment of canyons exposure to riverine plastic inputs and fishing-related debris indicates varying susceptibility of canyons to litter, also highlighting that most of the canyons prone to receive large amounts of anthropogenic debris have not yet been surveyed. Considering that litter research in canyons is still in its infancy, several knowledge gaps need to be filled before the role of canyons as litter traps and the implication for benthic ecosystems can be fully understood.

Assessment of macro litter in Deli River Medan during pandemic COVID-19

This study identifies and quantifies floating macro litter and macro plastic from Deli River Medan during pandemic Covid-19. Macro litter transport consists of floating items at surface, suspended in water column and transport over on riverbed. Litter was collected from 5 location along 11.6 km using static trawls with a height of 150 cm and width of 300 cm with a square mesh size of 0.5 cm. Sampling was done in July, and during selection, 40 cm of net’s height was constantly submerged for one hour. This study found that macro litter was 19.26 kg/h with 65.2% as anthropogenic waste, 34.3% as macro plastic, 0.3% as metal, and 0.15% as medical waste. The composition of macro plastic has various variants, namely food containers, plastic bags, food packaging, sanitary packaging, and mineral water packaging with percentages of 10.21%, 67.89%, 8.35%, 4.36%, and 9.18%. The macro plastic abundance was obtained at 2,476 x 10-4 kg/m3. This study showed a significant increase in plastic consumption during the pandemic, especially plastic bags because it is dominated in all locations.

Insights into seafloor litter spatiotemporal dynamics in urbanized shallow Mediterranean bays. An optimized monitoring protocol using towed underwater cameras

Monitoring of marine litter at the sea surface, the beaches and the seafloor is essential to understanding their sources, pathways and sinks and design effective clean-up programs or increase public awareness for reducing litter waste. Up until today, seafloor litter is the least exploited component of marine litter. Although the protocols for recording and assessing seafloor litter in the deep-sea environments are currently being actively defined and practiced, shallow seafloor litter survey protocols are still notably under-developed. Moreover, trawling for fishing, which is the main means for collecting seafloor litter data, needs to be phased out in the coming years due to its high environmental footprint and be replaced by less destructive ways based on underwater imagery. In this paper we propose an integrated approach for assessing in detail the spatiotemporal distribution and composition of seafloor litter in shallow coastal environments, using common towed underwater cameras. Effort has been put to correctly estimating spatial litter densities regarding the true coverage of the visualized area, which was efficiently extracted through photogrammetric reconstruction of the seafloor. Interpretation of the spatial distribution of litter was aided by auxiliary bathymetric and swath sonar backscatter datasets, to determine the seabed geomorphological features that control their dispersion and composition. Local geo-morphology, along with any reported coastal anthropogenic activity, are correlated to seafloor litter densities to investigate the temporal and spatial dynamics that control their distribution and temporal trends in Syros Island, Cyclades, Greece. There, in the context of LIFE DEBAG project, monitoring of an urbanized shallow bay for 3 consecutive years has been performed to assess the impact of an intensive local awareness raising campaign to the local environment. A significant reduction of litter densities under the impact of this campaign has been documented, while links between the seafloor litter transport dynamics and the seabed micro- and macro-topography were made evident. Monitoring litter densities on the seafloor of urbanized shallow bays proved to be a prospective way of tracking marine litter pressures on the local marine environment.

Riverine Plastic Monitoring during the Rainy Season in the Citarum Estuary of Muara Gembong

The restoration effort to clean up the river, known as “Citarum Harum” requires monitoring to estimate both the composition and the volumes of plastic pollution. The objective of the monitoring is to obtain a scientific baseline of marine plastics from Citarum River as a function of other influencing aspects. A static net trawl (60 m x 10 m, mesh size 2.5 cm, and about 1 meter submerged) was installed under the New Muara Gembong Bridge for eight consecutive days in March and April 2021 or during the rainy season. The trapped debris was collected manually into boxes using two boats and simple tools. After the drying, weighting, classification processes and by excluding natural organics (leaves/branches), plastics contributed as the most dominant for both abundance (83%) and weight (31%) followed by textiles, hazardous materials, construction materials and rubbers. The hydrological conditions as well as the tides were also observed to be one of dominant parameters. The quantification of macro-plastic litter transport from River Citarum into the Java Sea is also an aim for the ASEANO project (ASEAN – Norway cooperation project on local capacity building for reducing plastic pollution in the ASEAN region).

A Cross Disciplinary Framework for Cost-Benefit Optimization of Marine Litter Cleanup at Regional Scale

Litter cleanup and disposal management in the marine environment are increasingly subject to public scrutiny, government regulation and stakeholder initiatives. In practice, ongoing efforts and new investment decisions, for example in new cleanup technologies, are constrained by financial and economic resources. Given budgetary restrictions, it is important to optimize decision-making using a scientific framework that takes into account the various effects of investments by combining multiple scientific perspectives and integrating these in a consistent and coherent way. Identifying optimal levels of marine litter cleanup is a challenge, because of its cross-disciplinary nature, involving physics, environmental engineering, science, and economics. In this paper, we propose a bridge-building, spatial cost-benefit optimization framework that allows prioritizing where to apply limited cleanup efforts within a regional spatial network of marine litter sources, using input from the maturing field of marine litter transport modeling. The framework also includes ecosystem functioning in relation to variable litter concentrations, as well as the potentially non-linear cost-efficiency of cleanup technologies. From these three components (transport modeling, ecosystem functioning, cleanup-effectiveness), along with litter source mapping, we outline the optimal cleanup solution at any given ecological target or economic constraint, as well as determine the cleanup feasibility. We illustrate our framework in a Baltic and Mediterranean Sea case study, using real data for litter transport and cleanup technology. Our study shows that including pollution Green's functions is essential to assess the feasibility of cleanup and determine optimal deployment of cleanup investments, where the presented framework combines physical, economical, technological and biological data consistently to compare and rank alternatives.

The role of plants in the face of marine litter invasion: A case study in an Italian protected area

Marine litter accumulates in coastal dunes and causes severe damages to these fragile ecosystems. This study analyzed the composition, cover and distribution of marine litter and its relation to vegetation cover in a Mediterranean dune system, located in a protected area facing the Ligurian Sea (Northern Italy). We sampled twenty-two permanent multiscale plots in spring and autumn. Litter was detected in all plots and artificial polymer materials were the dominant type (85%). Litter categories increased from spring to autumn mainly due to seaside tourism. The largest spatial scale (16 m2) explained the variability in waste composition better than the smaller ones (4 m2, 1 m2). Finally, the vegetation cover correlated inversely with the turnover of litter categories, suggesting that plants may act as a barrier to litter transport by trapping it, and that they play a role in the spatio-temporal dynamics of coastal litter.

A mechanism for the increased wave-induced drift of floating marine litter

Abstract

Anthropogenic litter in freshwater environments – Study on lake beaches evaluating marine guidelines and aerial imaging

Studies on macroplastic pollution in freshwater systems are rare compared to the marine environment. Nevertheless, freshwater systems are worthy to be equally investigated as they are pathways of plastic to the ocean and lakes may act as (temporary) sinks. The aim of this study was to identify sources for plastics and influences on its distribution in a limnic environment. Anthropogenic litter (>5 mm) was monitored semi-annually over a three-year period at four sandy bank border segments of Lake Tollense in Mecklenburg-Western Pomerania, Germany. The selected beaches represent different expositions and vary in their level of anthropogenic activity. Considering all six samplings, mean abundance of anthropogenic litter is 0.2 ± 0.1 items/m2 or 130.9 ± 91.0 items/100 m beach length. The averaged mass of anthropogenic litter is 0.5 ± 1.0 g/m2 or rather 218.7 ± 284.6 g/100 m. Plastic consistently is the predominate material (72%) and cigarette butts are the most found items. A higher pollution by anthropogenic litter is found at the end of tourist season unveiling the impact of anthropogenic activity on litter abundance. Additionally, litter transport via tributaries into the lake plays a role.Testing the detection of anthropogenic litter via aerial images taken by unmanned aerial vehicles resulted in good recovery rates when minimizing the flight height. Furthermore, the analysis of anthropogenic litter distribution displayed on the images showed litter accumulation areas at the border of sandy beach areas. The deployment of marine guidelines in a freshwater environment did work well, however, small changes in the protocol are suggested for future lake beach studies dealing with anthropogenic litter pollution.

Variation of floatable litter load and its compositions captured at floating debris boom (FDB) structure

Hydrological runoff impacts on the accumulation of floatable litter in river system have not been extensively studied in Malaysia. Thus, the aim of this paper was to identify the variation on the accumulation of floatable litter load and its composition at floating debris boom (FDB) structure through the process of hydrological runoff. 14 days of passive sampling was performed periodically using the bucket conveyer machine. The rainfall event prior to the sampling date was used in Soil Conservation Service curve number (SCS-CN) method to generate the runoff volume. The results revealed that the highest accumulation of floatable litter load was 4654.60 kg/day during the first sampling. The plastic and organic waste load were recorded as the highest composition load with 881.50 kg/day during first sampling and 501.00 kg/day during second sampling, respectively. The floatable litter transport was demonstrated through the relationship between cumulative floatable litter loads and cumulative hydrological runoff during the first sampling with R2 = 0.9572, r = 0.978 (p < 0.01); and second sampling with R2 = 0.9806, r = 0.990 (p < 0.01). Such data will contribute to knowledge and serve as baseline data information for the relevant agencies in ameliorating this environmental issue in long term planning.

The key role of canyons in funnelling litter to the deep sea: A study of the Gioia Canyon (Southern Tyrrhenian Sea)

Abstract Litter is a significant environmental issue, threatening all ocean environments including the deep sea, where little is known about the extent of the threat. This study collected underwater videos on shelf-indenting canyons (the Gioia and Petrace Canyon) and adjacent sectors to characterize benthic litter and its distribution patterns. A high density of litter was present in the canyon thalwegs (up to 56.3 items/100 m), where ∼95 % of observed debris was concentrated. Litter primarily comprised of plastic (∼90 %). The presence of household objects intermingled with vegetal material indicates a strong influence of land-based sources for litter in these areas. Sedimentary gravity flow processes transported natural and anthropogenic debris downslope and may determine its burial beneath the seafloor. Another litter transport mechanism is the presence of light items, observed while drifting above the seafloor under the action of down-canyon bottom currents. This phenomenon was frequently documented within Gioia Canyon, where up to 74 drifting items were counted in one hour of video. Conversely, a lower litter concentration was found along the continental margin, where items were mostly fishing-related. Findings from this study confirm that canyons act as conduits for land-sourced debris and litter transport from coastal to deep-sea environments. The funnelling of a large amount of plastic to the deep sea through multiple processes indicates that the magnitude of this pollution may be greater than expected. This pollution could concentrate in canyons along continental margins and possibly at the mouths of canyons at the base of the slope. This issue requires urgent attention, as understanding of deep-sea litter distribution is still limited and potential impacts to benthic ecosystems are poorly understood.

Spatial heterogeneity in water velocity drives leaf litter dynamics in streams

Abstract Stream hydro‐morphology refers to the heterogeneous distribution of hydrologic conditions that occur above a complex benthic surface such as a streambed. We hypothesised that hydro‐morphological conditions will influence the retention, re‐distribution, and microbial‐driven decomposition of leaf litter inputs in stream ecosystems because each process varies with overlying water velocity. We tested this hypothesis using: (1) the spatial distribution of water velocity within a stream reach as a surrogate of stream hydro‐morphology; (2) leaf tracer (i.e. Ginkgo biloba L.) additions with serial recovery to examine the relationship between benthic retention and overlying velocity; and (3) measurements of leaf litter decomposition (i.e. Alnus glutinosa [L.] Gaertn.) under different water velocity conditions. Results demonstrate that water velocity exerts a significant influence on the retention and re‐distribution of leaf litter inputs within the reach. The observed range of water velocity (from c. 0 to 0.92 cm/s) also strongly influences the range of leaf litter decomposition rates (0.0076–0.0222/day). Our findings illustrate that water velocity influences leaf litter dynamics in streams by controlling leaf litter transport, retention and re‐distribution as well as how leaves decompose within recipient stream reaches. Ultimately, the results show that the efficiency of leaf litter inputs in supporting stream ecosystem function is dependent on the hydro‐morphological characteristics of the receiving stream ecosystems.

Connectivity Dynamics in Dryland Litter Cycles: Moving Decomposition beyond Spatial Stasis

AbstractDrylands (arid and semiarid ecosystems) cover nearly half of Earth's terrestrial surface, but biogeochemical pools and processes in these systems remain poorly understood. Litter can account for a substantial portion of carbon and nutrient pools in these systems, with litter decomposition exerting important controls over biogeochemical cycling. Dryland decomposition is typically treated as a spatially static process in which litter is retained and decomposed where it is initially deposited. Although this assumption is reasonable for mesic systems with continuous plant canopy cover and a stable subcanopy litter layer, dryland pools generally reflect discontinuous inputs from heterogeneous canopy cover followed by substantial litter transport. In the present article, we review horizontal and vertical transport processes that move litter from the initial deposition point and retention elements that influence litter accumulation patterns. Appreciation of the spatially dynamic litter cycle, including quantitative assessment of transport patterns, will improve estimates of the fate and distribution of organic matter in current and future drylands.

Calibration of a marine floating litter transport model

ABSTRACTPredicting the transport of marine floating litter requires a detailed understanding of the processes involved in the dispersion of floating materials in the ocean. The restraining effect of a near-coastal boundary or shallow bottom topography may affect the drift response to local wind forcing. The aim of this work is to develop a particle-tracking model for the north-west Iberian waters that allows for spatial variations in the effect of winds on the transport of marine floating litter. Observational data from 23 drifters were used, in conjunction with wind and ocean current data from atmospheric and ocean models. The drifter locations were grouped into three separate zones based on the bathymetry and the orientation of the coastline. Response matrices for each of these areas were computed using a 2-D vector regression approach. The maximum drift response to local wind forcing is alongshore in inner shelf waters, whereas an isotropic drift response to winds is observed in outer shelf waters. The wind drag coefficient ranges from 0.5 × 10−2 to 1.2 × 10−2, depending both on the wind direction and the drifter position.

Marine litter on deep Arctic seafloor continues to increase and spreads to the North at the HAUSGARTEN observatory

The increased global production of plastics has been mirrored by greater accumulations of plastic litter in marine environments worldwide. Global plastic litter estimates based on field observations account only for 1% of the total volumes of plastic assumed to enter the marine ecosystem from land, raising again the question ‘Where is all the plastic? ’. Scant information exists on temporal trends on litter transport and litter accumulation on the deep seafloor. Here, we present the results of photographic time-series surveys indicating a strong increase in marine litter over the period of 2002–2014 at two stations of the HAUSGARTEN observatory in the Arctic (2500m depth).Plastic accounted for the highest proportion (47%) of litter recorded at HAUSGARTEN for the whole study period. When the most southern station was considered separately, the proportion of plastic items was even higher (65%). Increasing quantities of small plastics raise concerns about fragmentation and future microplastic contamination. Analysis of litter types and sizes indicate temporal and spatial differences in the transport pathways to the deep sea for different categories of litter. Litter densities were positively correlated with the counts of ship entering harbour at Longyearbyen, the number of active fishing vessels and extent of summer sea ice. Sea ice may act as a transport vehicle for entrained litter, being released during periods of melting. The receding sea ice coverage associated with global change has opened hitherto largely inaccessible environments to humans and the impacts of tourism, industrial activities including shipping and fisheries, all of which are potential sources of marine litter.

Accumulation and partitioning of heavy metals in mangrove rhizosphere sediments

A field study was conducted to clarify the effect of rhizosphere processes on the accumulation and partitioning of heavy metals (Pb, Zn, Cu, Cr, Cd and Ni) in mangrove sediments. Metals were fractionated by a sequential extraction procedure into three chemically distinct fractions: water soluble, exchangeable and carbonate bound (B1), Fe–Mn oxide bound (B2), and organic and sulfide bound (B3). Results indicate that rhizosphere processes tend to increase the metal concentrations in the rhizosphere sediments. However, plant uptake may result in the decrease of the metal concentrations in the rhizosphere sediments when the metal concentrations are relatively low in the bulk sediments. Compared with the bulk sediments, the rhizosphere sediments have low concentrations of heavy metals in the B1 and B2 fractions and high concentrations in the B3 fraction. Either an increase or decrease in the residual fraction of heavy metals in the rhizosphere sediments may appear, depending on whether the formation of the refractory metal-organic compounds or the activation of the residual fractions dominates. Results also indicate that mangrove plants absorb and store non-essential metals in the perennial tissues, thus reducing the export of non-essential metals via leaf litter transport. Mangrove plants are excellent candidates for phytostabilization of heavy metals in intertidal substrates.

Slope length effect on sediment and organic litter transport on a steep forested hillslope: upscaling from plot to hillslope scale

Upscaling and the effect of slope length on the sediment production are important issues in hillslope hydrology. This study investigated the effect of slope length at a steep forested site between 2006 and 2010 using erosion plots and neighboring sediment traps. The hillslope had high litter cover but sparse understory due to overgrazing by wild deer. Sediment transport increased for short distances (5 m to 10 m), then decreased over the hillslope (> 10 m). In plots this effect was due to organic litter accumulation. Organic litter production declined progressively along the hillslope continuum. When accumulated organic litter altered the microtopography, sediment production declined more with increase in slope length. Heavy precipitation events did not change the pattern of these scale effects. These results demonstrate that the slope length effect had inconsistent controls on sediment transport due to variations in soil surface conditions of the landscape. Such variations in the slope length effect cause uncertainty in sediment flux estimations in steep forested landscapes.

Phosphorus and trace metal dynamics in soils amended with poultry litter and granulates

AbstractEnvironmental sustainability of animal agriculture is strongly dependent upon development of approaches to minimize the potential environmental impacts of applying animal manures. The excess manure and its nutrients (primarily phosphorus) in intensive animal production regions may need to be exported to other areas to comply with increased regulations on manure management. In our previous study we generated a variety of granulated products from poultry litter to achieve export of excess litter from the southwestern Ozarks, AR, USA. Our objective in the present study was to determine the effect of the application of poultry litter and granulated litter products on phosphorus (P), arsenic (As), copper (Cu) and zinc (Zn) dynamics in two Arkansas soils (Dewitt silt loam and Hector sandy loam). Poultry litter and granulated products were mixed with the surface horizon (0–15 cm) of soils at two application rates: P‐based (100 kg total P per hectare) and N‐based (160 kg plant‐available N per hectare). Soil–litter mixtures were incubated at 25 °C for 21 days. Sub‐samples were removed at 1, 7 and 21 days to determine the solubility and availability of P, As, Cu and Zn in soils. Results suggest that when litter was applied at 100 kg total P per hectare, contents of P, As, Cu and Zn were significantly greater in the soils amended with litter and granulated products than in the control (soil alone). However, the contents of P, As, Cu and Zn did not significantly differ in the soils amended with either normal litter or granulated litter products at total P or plant‐available N‐based application rates. This suggests that poultry litter granulation is a sound management practice that can be used to reduce concerns with fresh litter transport and potentially improve P and trace element balances in intensive poultry production regions, especially when applied on a plant‐available N basis.

How Far Can Poultry Litter Go? A New Technology for Litter Transport

Exporting northwest Arkansas excess turkey and broiler litter to partially fertilize nutrient-deficient cropland in eastern Arkansas can be more cost effective than to supply all crop nutrients with chemical fertilizer only, given current high fertilizer prices. Cost savings are greater if litter is baled in ultraviolet resistant plastic and transported via truck, since backhaul opportunities reduce truck rates, or alternatively, if raw litter is shipped via a truck-barge combination. Rice is the crop that allows for greater savings according to a mathematical programming model implemented in General Algebraic Modeling System (GAMS).