Quantifying changes in litter loads in urban stormwater run-off from Cape Town, South Africa, over the last two decades

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.

Wind- and rain-driven macroplastic mobilization and transport on land

Wind and rain are considered main drivers for mobilization and transport of macroplastics on land, yet there is a lack of empirical data that quantifies this. We present lab experiment results on land-based macroplastic mobilization and transport. We placed four types of macroplastics on terrains with varying surface roughness and slope angles, and exposed them to changing wind speeds and rain intensities. In general, we find that the mobilization probability and transport velocity of macroplastics strongly depend on the combination of the terrain characteristics and material properties. At Beaufort 3, 100% of the plastic bags were mobilized, whereas for the other plastic types less than 50% were mobilized. We found 1.4 (grass) to 5 times (paved surface) higher mobilization probabilities on land than assumed by existing plastic transport models. Macroplastic transport velocities were positively correlated with wind speed, but not with rain intensity. This suggests that macroplastics are not transported on land by rain unless surface runoff develops that can bring the macroplastics afloat. Macroplastic transport velocities were, driven by wind, 1.9 and, driven by rain, 4.9 times faster on paved surfaces than on grass. This study enhances our understanding of land-based macroplastic transport and provides an empirical basis for models.

Stormwater outlets: A source of microplastics in coastal zones of Cape Town, South Africa

The runoff from stormwater outlets are potential sources of microplastics (MPs) in coastal zones. The characteristics and concentrations of MPs in coastal water, sediment and biota (mussels, whelks and sea urchins) were measured in summer (2020/2021) (dry season) and winter (2021) (wet season) from three sites (Camps Bay, Mouille Point and Three Anchor Bay) in Cape Town. MPs were characterised visually using a stereo microscope and chemically using spectroscopy. MP concentrations were higher in water and sediment during winter, and higher in biota in summer. Compared to control sites, MPs were higher at all impact sites sampled. MPs extracted were mainly black polyester (PEST) fibres, 1000 to 2000 μm in length averaging 0.15 MPs/L in water, 52.11 MPs/kg dry weight in sediment and 1.35 MPs/g soft tissue wet weight in biota. The results indicate that coastal stormwater systems are potential sources of MPs in the coastal environment of Cape Town.

Environmental concentrations, characteristics and risk assessment of microplastics in water and sediment along the Western Cape coastline, South Africa

Plastic debris is accumulating in all environments globally and South Africa's poor waste management plan has led to an increase in plastic contamination throughout the country. Information about microplastics (MPs) in urban and rural coastal environments in South Africa is poor. The aim of this study was to determine coastal MP concentrations in water (particles/L) and sediment (particles/kg). Sampling took place in summer of 2020 during low tide at 14 sites, along the coast of the Western Cape, South Africa. MPs were extracted and analysed based on shape, color, size and polymer type (using an ATR-FTIR). An ecological risk assessment was done to assess the potential risks posed by MPs in all sample types. Sediment MP concentrations (185.07 ± 15.25 standard error particles/kg) were higher than water (1.33 ± 0.15 particles/L). Gordon's Bay (site 12) had the highest MP concentrations in sediment samples (360 ± 36.74 particles/kg), identifying harbors as the main source for MP contamination. Kalk Bay (site 9) displayed the highest concentration in water samples (4.97 ± 0.18 particles/L), suggesting that the source of MPs are from stormwater outfall pipes and human activities. Filaments were the most dominant MP shape (89%) for all samples, with black/grey (water) and transparent (sediment) being the most dominant colors (31% and 31% respectively). Dominant sizes were 1000-2000 μm in water and 2000-5000 μm in sediment. Polyethylene terephthalate (PET) (29%) was the most dominant polymer type recorded in water samples and natural fibres (mainly cotton) (32%) recorded in sediment. Based on the risk assessment, MPs recorded at Mouille Point (site 6) poses the greatest ecological risk associated with polymers. MP concentrations reported in this study provide a baseline for future studies along the Western Cape coastline of South Africa.

Characteristics and Risk Assessment of Microplastics in Water and Mussels Sampled from Cape Town Harbour and Two Oceans Aquarium, South Africa

The aim of this study was to measure the characteristics and risk assessment of microplastics (MPs) in Cape Town Harbour (CTH) and the Two Oceans Aquarium (TOA) in Cape Town, South Africa from 2018 to 2020. Water and mussel MP samples were analyzed at 3 sites in CTH and TOA, respectively. Microplastics were mainly filamentous, black/grey and 1000-2000 μm in size. A total of 1778 MPs, averaging 7.50 (± 0.6 standard error of the mean, SEM) MPs/unit were recorded. Average MP concentrations were 10.3 ± 1.1 MPs/L in water and 6.27 ± 0.59 MPs/individual or, based on weight, 3.05 ± 1.09 MPs/g soft tissue wet weight in mussels. Average MPs in seawater in CTH (12.08 ± 1.3 SEM MPs/L) was significantly higher (4.61 ± 1.1 MPs/L) than inside the TOA (U = 536, p = 0.04). Various risk assessment calculations indicate that MPs in seawater poses a greater ecological risk than MPs in mussels at the sites sampled.

Land use and COVID-19 lockdowns influence debris composition and abundance in stormwater drains

Stormwater drains act as a pathway for anthropogenic debris from land to sea, particularly in urbanised estuaries where impervious surfaces expedite the process. Debris type and abundance in stormwater drains may vary due to land use and human activity, and knowledge of this variation is necessary to manage the growing threat of debris. Surveys of stormwater debris can inform targeted reduction and remediation efforts by intercepting and identifying pollutants near their source. We surveyed replicate stormwater gross pollutant traps across four land use zones (city centre, shopping centre, transportation hub, industrial precinct) before and during COVID-19 measures to assess the effects of changing human activities. Gross pollutant traps were installed in 120 drains in Greater Melbourne, Australia, and citizen scientists trained by Tangaroa Blue Foundation weighed and classified debris at 6-week intervals between October 2019 and October 2020. Four survey cycles were conducted before lockdowns were implemented, then another four during lockdowns. COVID-19 lockdowns and patterns of debris type and abundance across land use revealed how changes in human activity might impact the flow of debris. Cigarette butts were the most abundant macro debris (>5 mm) item in every survey cycle, regardless of lockdowns. Industrial land use zones had the lowest macro debris counts but contained over 90 % of the micro debris (1-5 mm). The amount of total macro debris decreased during lockdowns, however the most abundant and problematic debris items such as cigarettes and single-use plastics did not decrease as much as might be expected from the concomitant reductions in human activity. Occupational health and safety items, such as masks and gloves, increased (144 %) during COVID-19 lockdowns. Micro debris counts did not change in industrial zones during lockdowns, suggesting that workplace interventions may be necessary to reduce this debris leakage. Tracing the pathway of debris from source to sea can inform reduction and long-term management strategies.

Spatio-temporal distribution of microplastics in water and sediment samples of the Plankenburg river, Western Cape, South Africa

Microplastic (MPs) pollution has become a subject of environmental concern due to its wide ubiquity in the environment. Microplastics are possible sources of other hazardous chemicals to aquatic organisms due to their composition and sorption properties. In this study, MPs occurrence in water and sediment samples of the Plankenburg River, Western Cape, South Africa was investigated. The physicochemical characterization of the river water was done onsite. 30 L water samples were collected and filtered in 10 L triplicates through a 250 μm mesh onsite using a metal bucket. An additional 12 L sample was collected and filtered in 4 L triplicates through 20 μm mesh in the laboratory. The extraction of MPs from water in the laboratory was by density separation. Sediment samples were also collected at the selected sites, oven-dried and microplastics in the laboratory. Sampling was conducted over four seasons - spring, summer, autumn, and winter. Microplastics were classified by visual observation and Fourier Transform Infrared Spectroscopy (FTIR-ATR). The seasonal distribution of MPs in the surface water samples varied across all sites. However, spring samples had the highest MPs occurrence (5.13 ± 6.62 MP/L) and the least, in autumn (1.52 ± 2.54 MP/L). The MPs in sediment samples were observed in spring (1587.50 ± 599.32 MP/kg). Fibres were the most dominant microplastic particle type (shape), with a size range of 500-1000 μm at the different sites. The infrared spectroscopic analysis confirmed the dominant polymer type to be polyethylene. This study provides an understanding of the microplastic occurrence in the Plankenburg River system and gives a baseline for future monitoring and assessment of water and sediment in the South African freshwater systems.

Proximity to coast and major rivers influence the density of floating microplastics and other litter in east African coastal waters

Floating anthropogenic litter occurs in all ocean basins, yet little is known about their distribution and abundance in the coastal waters off east Africa. Neuston net and bulk water sampling shows that meso- and micro-litter (8567 ± 19,684 items∙km^-2, 44 ± 195 g∙km^-2) and microfibres (2.4 ± 2.6 fibres∙L^-1) are pervasive pollutants off the coasts of Tanzania and northern Mozambique, with higher litter loads off Tanzania. Densities of meso- and micro-litter at the start of the rainy season were greater close to the coast and to major river mouths, suggesting that much litter likely originates on land. However, the mass of litter increased with distance from the six major coastal cities. By number, 95% of meso- and micro-litter was plastic, but only 6% of microfibres. Our results highlight the need to reduce plastic use and improve solid waste management in the region.

Insights from the Niger Delta Region, Nigeria on the impacts of urban pollution on the functional organisation of Afrotropical macroinvertebrates

Anthropogenic activities, including urbanisation and industrialisation threaten stream ecological integrity, ecosystem community structure and ecosystem functioning of rivers and streams worldwide. However, developing sustainable monitoring strategies for ecological health remains a critical challenge in Africa. We examined the effects of urban disturbance on macroinvertebrate Functional Feeding Groups in selected streams in the Niger Delta Region of Nigeria. We sampled 11 sites between 2008 and 2012 and grouped into three site groups (Site groups 1 > 2 > 3). The groups represent an increasing gradient of urban pollution. Our result showed that urban-induced disturbances affected physicochemical variables in the study area (PERMANOVA; p < 0.05), with nutrients NO₂-N, PO₄-P, and electrical conductivity being significantly higher in impacted Site group 3 (ANOVA, p < 0.05). Predators and gatherers were the most dominant Functional Feeding Group recorded in the study area, while shredders were the least abundant macroinvertebrate Functional Feeding Groups. The multivariate RLQ analysis revealed that shredders, predators, and scrapers were tolerant of urban pollution, whereas gatherers were sensitive to increasing urban pollution. Overall, macroinvertebrates Functional Feeding Groups responded differentially to urban pollution in the Niger Delta Region. Identifying pollution indicator Functional Feeding Groups is seen as an important step towards developing a reliable, low-cost tool for riverine monitoring of urban pollution effects in Africa.

Macroplastic transfer dynamics in the Loire estuary: Similarities and specificities with macrotidal estuaries

The quantification of macroplastic fluxes transferred by rivers toward the pelagic environment requires a better understanding of macrodebris transfer processes in estuarine environments. Following the strategy adopted in the Seine estuary, this study aims to characterize macroplastic trajectories in the Loire estuary. Between January 2020 and July 2021, 35 trajectories were monitored using plastic bottles equipped with GPS-trackers. With total travelled distances between 100 m and 103.6 km, trajectories show great spatiotemporal variability. The various forcing factors (macroplastic buoyancy, estuaries tidal and hydrometeorological conditions, geomorphology and vegetation) lead to chaotic trajectories, preventing accurate predictions in macroplastic transfer and storage/remobilization dynamics. In the Loire estuary like in the Seine one, no tracked bottle reached the Atlantic Ocean. It confirms that macrotidal estuaries under temperate climates constitute accumulation zones and slow pathways for macroplastics, but raises question on the real fluxes transferred from continental areas to oceans.

Plastic pollution in the surface water in Jakarta, Indonesia

Plastic pollution in the ocean primarily originates from the land-derived mismanaged plastic waste that is transported by rivers. This study aimed to estimate the plastic litter generation in the surface water in Jakarta and Indonesia. A field survey was conducted at six riverine sampling points (upstream to downstream) and three holding facilities of the litter in Jakarta during the rainy season. The Jakarta Open Data database was used to estimate the tonnage of plastic litter. By mass, plastic comprised approximately 74 % of the anthropogenic litter in rivers and 87 % in holding facilities. The riverine plastic proportion slightly increased downstream. Approximately 9.9 g/person/day of plastic litter was discharged into Jakarta's surface water during rainy season and recovered by floating booms. To reduce plastic pollution and its severe impacts on aquatic ecosystems and human health, further field investigation is necessary to design an effective clean-up system and litter-prevention strategy.

First biomonitoring of microplastic pollution in the Vaal river using Carp fish (Cyprinus carpio) "as a bio-indicator"

Fish inhabiting freshwater environments are susceptible to the ingestion of microplastics (MPs). Knowledge regarding MPs in freshwater fish in South Africa is very limited. In this study, the uptake of MPs by common carp (Cyprinus carpio) in the Vaal River in South Africa was assessed. MPs were detected in all of the twenty-six fish examined, 682 particles of MPs were recovered from the gastrointestinal tracts of the fish with an average of 26.23 ± 12.57 particles/fish, and an average abundance of 41.18 ± 52.81 particles/kg. The examination of the physical properties of MPs revealed a predominance on fibers (69%), small-sized particles of less than 0.5 mm (48%), as well as prevelance of coloured MPs (94%), mostly green, blue, and black. Using Raman Spectroscopy, the following plastic polymers were identified: high density polyethylene (HDPE), low density polyethylene (LDPE), polypropylene (PP), polyethylene terephthalate (PET), and polytetrafluoroethylene (PTFE). To the best of our knowledge, this study, is the first to report MPs uptake by freshwater biota in the Vaal River using common carp as a target organism. It provided evidence of MP contamination in the Vaal.

Amount, composition and sources of macrolitter from a highly frequented roadway

Many researches mention the need to identify the land-based sources of riverine macrolitter but few field data on litter amount, composition and sources are available in the scientific literature. Describing macrolitter hotspot dynamics would actually allow a better estimation of fluxes in the receiving environments and a better identification of the more appropriate mitigation strategies. This study provides new insights in roadway macrolitter production rates, typologies and input sources (i.e. deliberate or accidental). The macrolitter from an 800 m portion of a highly frequented roadway (around 90,000 vehicles per day) was collected during almost one year. Typologies were defined using the OSPAR/TGML classification. Results show high annual loads of macrolitter (42.8 kg/yr/ha), suggesting significant contributions of the road runoff to the litter fluxes in urban stormwater. Over the course of a year, 88.5 kg of debris were collected, including 53.2 kg (60%) of plastic debris. In total, 36,439 items were characterized, of which 84% were plastics. The macrodebris collected present a low diversity of components with Top 10 items accounting for 92% by count and a majority of small and lightweight items like plastic fragments (31%) or cigarette butts (18%). Input sources were estimated for 43% of the mass collected in which 37.2% were deliberately littered and 62.8% were accidental leaks, illustrating a major contribution of uncovered trucks and unsecured loads. The accumulation rates show a linear correlation with the road traffic. Such data are of prime interest since they enable to determine the potential contribution of road traffic to plastic fluxes to the environment.

Macrolitter dataset from a highly frequented roadway in Nantes, France

Land-based sources of riverine macrolitter are now recognized as a major concern, but few field data on litter amount, composition and sources are available. This is especially the case for macrolitter hotspots like high frequented roadways that could generate large amount of macrolitter potentially reaching rivers. This dataset provides macrolitter amount and composition over one year from a retention pond collecting stormwater and carried macrolitter from a 800 m portion of a highly frequented roadway (around 90,000 vehicles per day). The typology of macrolitter was defined using the TSG-ML/OSPAR classifications. A total of 36,439 items in which 84% of plastics were individually counted, classified and weighted by category for a total mass of 88.5 kg (60% of plastics). Raw data are available in Mendeley Data (DOI:10.17632/t6ryv6crjd.4). Top 10 items represent 92% by count of the total with plastic fragments (31%), cigarette butts (18%), EPS fragments (17%) or foam packaging (11%) as most common items. Top 10 items represent 72% by mass of the total with plastic fragments (24%) and Cardboard (13%) as most common items, followed by foam packaging (6%), wood fragments (6%), industrial plastic sheets (5%), rubber fragments (4%) and EPS fragments (4%). More than 94% of plastic items are below 1.9 g/item. This dataset is related to the research paper Amount, composition and sources of macrolitter from a highly frequented roadway.

Riverine litter in a small urban river in Marseille, France: Plastic load and management challenges

Small urban rivers are thought to be major sources of riverine litter, especially macroplastics, into the ocean. In well-developed countries, waste management infrastructures and recovery systems are sometimes implemented to prevent their emission into the sea meeting environmental and economic goals. The Huveaune River in Marseille, South of France, is a typical case study showing a non-negligible and uncontrolled leakage of riverine litter remains, despite all recovery systems implemented. Giant bar screens are settled over the river to collect riverine litter from the whole water column before water is released into the Sea. In this paper, screened material was characterized during a dry, wet and heavy rainfall period and annual macroplastic mass flows were estimated. The plastic fraction represented 83% by count of the 3147 items sorted and counted. Mass flow of plastic debris ranged between 1.1 and 5.8 mt/yr (equivalent to 2.1-11.4 g/cap/yr), in which 0.4-2.1 mt/yr (equivalent to 0.8-4.1 g/cap/yr) are bypassed to the sea during heavy rainfall periods. Giant bar screens across the Huveaune River prevent 65% of the mass flow to reach the sea annually, but 35% remain uncontrolled. When compared to the Seine River and other European Rivers, macroplastic leakage into the ocean per capita may range between 1 and 10 g/cap/yr. This suggests that end-of-pipe solutions are not enough and further supports urgent regulations of the plastic production on local to global scales to tackle the plastic pollution at its source.

Buoyancy affects stranding rate and dispersal distance of floating litter entering the sea from river mouths

Rivers are a major source of litter entering the sea but our understanding of the transport and fate of plastics in estuarine environments is poor. Marked blocks of varying buoyancy were released at three river mouths in South Africa. Of the 1400 blocks released, 80% were recovered on nearby beaches, with a higher recovery rate for more buoyant blocks. Dispersal distances increased with decreasing buoyancy at all sites; median dispersal distance of stranded items ranged from 20 to 90 m for expanded polystyrene (EPS) to 70-90 m for wood and 60-1042 m for high density polyethylene (HDPE) blocks. Floating litter in estuaries is subject to bidirectional flow and export is largely controlled by hydrodynamic conditions such as tides, winds, and wave action, as well as coastal structure and vegetation. Cleaning beaches around river mouths will help to reduce leakage of plastic and other litter into the sea.

Transfer dynamics of macroplastics in estuaries - New insights from the Seine estuary: Part 3. What fate for macroplastics?

Macroplastic emissions from the Seine estuary to the English Channel were estimated using institutional cleaning of riverbanks, combined with a tagged litter experiment. Cleaning were performed between March 2018 and April 2019 by the non-profit company Naturaul'un over 19 sites covering 20 km of riverbanks. A total of 365 tagged litter (90% macroplastics) was released in the estuary in March (n = 200), at the end of the winter/spring flood 2018, in July (n = 58), August (n = 56) and September 2018 (n = 51) during low river flow periods. Over the total tagged litter, 102 (28%) were recovered by Naturaul'un. Relative to the total amount of macroplastics (>5 cm) collected and the estimated amount of smaller/hidden macroplastics (>5 mm) not collected, the maximum macroplastic emission to the English Channel was estimated to be ~100-200 metric tons per year.

Environmentalism or greenwashing? Responses of South African value chain actors to plastic straw marine pollution

The increasing global concern surrounding plastic marine pollution has placed a spotlight on the key items identified as major contributors. The subsequent public outcry has forced key value-chain actors – such as brand owners, retailers and restaurateurs – to be seen to be responding to the issue. However, are their responses motivated by a true desire for environmentalism or are actors engaging in greenwashing? In this case study on plastic straws, the brand owners and retailers interviewed are driven by a desire to meet consumer expectations. This desire has led to the substitution of plastic straws with glass, paper and polylactide alternatives. However, the broader environmental implications of the alternatives are rarely considered. This single-minded focus on marine pollution has the potential to result in inadvertent greenwashing as alternative products may result in more harm in other environmental compartments.

Meso- and microplastics monitoring in harbour environments: A case study for the Port of Durban, South Africa

An investigation into the abundance and distribution of meso- and microplastics within the Port of Durban was conducted using a static immersible water pump and particle filtration system to collect meso- and microplastics from the water column, microplastics from sediment samples and corresponding CTD. Microplastics were detected in all samples under investigation. Results suggest that sewage overflow, stormwater drains, port operations, followed by rivers are input areas for mitigation to focus on. Identifying meso- and microplastics inputs, baselines and distribution allow for long term monitoring and management in a harbour environment. This can potentially contribute to the control and regulation of small plastics particles in harbours, and the subsequent transport of these pollutants via dredged material into other ecosystems.

Ingestion of plastic litter by the sandy anemone Bunodactis reynaudi

Ingestion of anthropogenic litter has been well documented in marine vertebrates, but comparatively little is known about marine invertebrates. We report macrolitter ingestion by the sandy anemone Bunodactis reynaudi at Muizenberg beach in False Bay, South Africa. Monthly surveys from May 2015 to August 2019 collected 491 ingested litter items (9.4 ± 14.9 items·month^-1, 39.8 ± 71.5 g·month^-1), of which >99% were plastic. The number of ingested items was correlated with the abundance of stranded items and ingestion peaked in autumn when seasonal rains washed more litter into the bay. Most ingested litter was clear (39%), white (16%) and black/purple (15%). Comparison with environmental litter showed selection for flexible plastics, particularly bags/packets and food packaging. Experimental feeding trials found that B. reynaudi selected for pieces of HDPE bag suspended in seawater for 2-20 days, suggesting that biofilms enhance the palatability of flexible plastics. Studies are needed to assess the possible impacts of plastic ingestion on B. reynaudi. While only a small proportion of the population currently ingest litter, ingestion might become more common if environmental litter loads increase. This might negatively affect the anemone's ability to respond to other environmental changes such as increasing levels of heavy metal pollution.

Quantifying temporal trends in anthropogenic litter in a rocky intertidal habitat

Most monitoring studies of marine anthropogenic debris have focused on sandy beaches, so little is known about litter on rocky shorelines. We surveyed litter trapped on a rocky intertidal shore in False Bay, South Africa, between May 2015 and March 2018. An exceptional upwelling of seabed litter occurred in November 2017 (70 items∙m^-1). Excluding this event, monthly clean-ups at spring low tide collected 2 (1.3-3.1) items∙m^-1∙month^-1 and 31 (19.4-49.4) g∙m^-1∙month^-1 of which 74% was plastic (31% by mass). Litter loads peaked in autumn when seasonal rains washed litter into False Bay, suggesting that most litter comes from local land-based sources. Litter composition differed from that on a nearby sandy beach, with more glass and other dense items on the rocky shore, but 60% of plastic items floated in water. Sand inundation and biotic interactions helped to trap buoyant plastics in the intertidal zone.

The missing sink - quantification, categorisation and sourcing of beached macro-debris in the Scottish Orkney Islands

Around the coastline of the UK, macro-debris has been observed in average densities of over 700 items per metre. Systematic beach-cleans were conducted at 35 sites around the Scottish Orkney Islands, in order to quantify and categorise the level of marine debris found there. Litter was collected from 100 m transects and categorised by its material, broad source (terrestrial or marine) and potential sector source. Variation between sites, and the relative contribution of pre-determined environmental variables in influencing said variation, were analysed using the "capscale" function for a canonical analysis of principle coordinates (CAP). 513 items/m were observed, (77% plastic), with "String/cord (<1cm diameter)" being the most abundant and widely distributed litter type. 47% of macro-debris was attributed to the fishing sector and < 10% to leisure, living and tourism-associated activities. Conversely, the unique regional hydrodynamics must be examined further, before the source of any given item can be categorically assigned.

Limited long-distance transport of plastic pollution by the Orange-Vaal River system, South Africa

Much of the plastic waste entering the sea is thought to be transported from land by rivers, yet little is known about the distances over which rivers transport plastic. To address this knowledge gap, we collected surface water samples from the Orange-Vaal River at the end of the wet and dry seasons. The Vaal River drains South Africa's main urban-industrial centre, whereas the upper Orange River is sparsely populated. Below their confluence, the river flows through increasingly arid regions with very low human populations before entering the Atlantic Ocean. We collected bulk water samples from 33 bridges to test for microplastic and microfibre (0.025-1 mm) pollution and conducted observations for macrodebris (>50 mm). Where possible, we sampled for plastic fragments (>1 mm) using a neuston net. Microfibres and microplastics were found at every site (1.7 ± 5.1 L^-1, >99% fibres) and accounted for 99% of the number of items recorded. Microfibres and microplastics were particularly abundant in the lower reaches during the period of low flow prior to the wet season flush. Macrodebris and larger microplastics were orders of magnitude less abundant (observations: 0.0002 ± 0.0007 items·m^-2; neuston net: 0.34 ± 0.93 items·m^-2). However, at sites where larger items were found, they comprised most of the mass of plastic. Larger plastics were found mostly at sites in the upper reaches of the Vaal River. Our results suggest that, while the Orange-Vaal River system may be a source of microfibres to the Atlantic Ocean, larger plastic items typically only travel short distances. The Orange-Vaal River system therefore does not appear to be a major source of plastics into the Atlantic Ocean, at least under regular flow conditions.

The Impact of the COVID-19 Lockdown on Urban Street Litter in South Africa

Abstract

The lockdowns instigated to slow the spread of the COVID-19 pandemic offered a unique opportunity to assess how restrictions on human activity affect street litter. We recorded daily litter arrival rates for 50 days in two South African cities from the time of strictest lockdown through two successive easings in regulations. The strict lockdown had no marked impact on litter composition, which was dominated by convenience foods and beverages (29% by number, 34% by mass) and tobacco products (33% by number, 3% by mass). The ban on the sale of tobacco products during the lockdown did not greatly reduce the number of cigarette butts and associated packaging. Vehicle parts accounted for <1% of litter items (2% by mass) whereas household waste spilled from bins prior to or during collection accounted for 3% of litter items (14% by mass). Street litter loads decreased roughly by a factor of three during the strict lockdown. The increase in litter was gradual, suggesting a reduction in compliance with regulations as the lockdown continued. Our results show a clear link between human activity levels and littering.

Highlights

• Street litter loads increased three-fold in two cities as Covid lockdowns eased.

• Cigarette butts made up 33% of litter by number despite a ban on tobacco sales.

• There is a clear link between human activity levels and littering.

Electronic supplementary material

The online version of this article (10.1007/s40710-020-00472-1) contains supplementary material, which is available to authorized users.