Global Riverine Plastic Outflows

Mai, Lei; Sun, Xiangfei; Xia, Linlin; Bao, Lian-Jun; Liu, Liang‐Ying; Zeng, Eddy Y.

doi:10.1021/acs.est.0c02273

Cited by 239 publications

(77 citation statements)

References 43 publications

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“…Inputs from river runoff were based on a global empirical function (Lebreton et al, 2017), taking into account of only one Mediterranean river (River Po). Moreover, this empirical function is strongly influenced by mismanaged plastic production distribution that might result in an underestimation or overestimation in high-income/developed countries and low-income/developing countries respectively (Mai et al, 2020), which is probably the case with particularly low inputs along the French and Spanish coasts. With regard to inputs from coastal cities wastewater, a uniform MPs concentration of (influent) wastewater was considered for the entire Mediterranean, in the absence of available data from different countries.…”

Section: Discussion and Concluding Remarksmentioning

confidence: 99%

“…The main model deviation is the underestimated MPs abundance in the Balearic Islands and North Ionian Sea and the relatively overestimated/underestimated concentration along the Ligurian Sea coast and the Gulf of Lion. The latter underestimation may be attributed to the river inputs calculated with the Lebreton et al (2017) global empirical function that is strongly influenced by the mismanaged plastic production distribution (Mai et al, 2020), being particularly low along the French and Spanish coasts. Thus, the plastics load from rivers in the Gulf of Lion, such as River Rhone is probably underestimated, as suggested by estimates based on observations (Schmidt et al, 2018).…”

Section: Near Surface -Microplasticsmentioning

confidence: 99%

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Modeling the Pathways and Accumulation Patterns of Micro- and Macro-Plastics in the Mediterranean

et al. 2021

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The Mediterranean is considered a hot-spot for plastic pollution, due to its semi-enclosed nature and heavily populated coastal areas. In the present study, a basin-scale coupled hydrodynamic/particle drift model was used to track the pathways and fate of plastics from major land-based sources (coastal cities and rivers), taking into account of the most important processes (advection, stokes drift, vertical and horizontal mixing, sinking, wind drag, and beaching). A hybrid ensemble Kalman filter algorithm was implemented to correct the near- surface circulation, assimilating satellite data (sea surface height, temperature) in the hydrodynamic model. Different size classes and/or types of both micro- and macroplastics were considered in the model. Biofouling induced sinking was explicitly described, as a possible mechanism of microplastics removal from the surface. A simplified parameterization of size-dependent biofilm growth has been adopted, as a function of bacterial biomass (obtained from a biogeochemical model simulation), being considered a proxy for the biofouling community. The simulated distributions for micro- and macroplastics were validated against available observations, showing reasonable agreement, both in terms of magnitude and horizontal variability. An 8-year simulation was used to identify micro- and macroplastics accumulation patterns in the surface layer, water column, seafloor and beaches. The impact of different processes (vertical mixing, biofouling, and wind/wave drift) was identified through a series of sensitivity experiments. For both micro- and macroplastics, distributions at sea surface were closely related to the adopted sources. The microplastics concentration was drastically reduced away from source areas, due to biofouling induced sinking, with their size distribution dominated by larger (>1 mm) size classes in open sea areas, in agreement with observations. High concentration patches of floating plastics were simulated in convergence areas, characterized by anticyclonic circulation. The distribution of macroplastics on beaches followed the predominant southeastward wind/wave direction. In the water column, a sub-surface maximum in microplastics abundance was simulated, with increasing contribution of smaller particles in deeper layers. Accumulation of microplastics on the seafloor was limited in relatively shallow areas (<500 m), with bottom depth below their relaxation depth due to defouling. The simulated total amount of floating plastics (∼3,760 tonnes) is comparable with estimates from observations.

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Section: Discussion and Concluding Remarksmentioning

confidence: 99%

Section: Near Surface -Microplasticsmentioning

confidence: 99%

Modeling the Pathways and Accumulation Patterns of Micro- and Macro-Plastics in the Mediterranean

et al. 2021

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“…In most of the world's oceans, plastic litter constitutes the greatest proportion of marine litter, either floating at the sea surface (e.g., Lebreton et al, 2019), on the seabed (e.g., Maes et al, 2018) or on foreshores (e.g., Browne et al, 2015). Data from monitoring programs globally are being used to try to quantify budgets of marine plastics, and to match the predicted inputs of plastic into the sea since the 1950s (e.g., Jambeck et al, 2015;Mai et al, 2020) with the total amounts of plastic that monitoring suggests exists in our oceans today (e.g., Cózar et al, 2014;Koelmans et al, 2017;Lebreton et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

Monitoring Plastic Beach Litter by Number or by Weight: The Implications of Fragmentation

Smith¹,

Turrell

2021

Front. Mar. Sci.

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Eighty surveys of ten Scottish beaches recorded litter sizes and weights. A simple model of fragmentation explains the distribution of plastic beach litter weights, producing a logarithmic cascade in weight-frequencies having a power law exponent of 1.6. Implications of fragmentation are numerous. Heavy litter is rare, light fragments are common. Monitoring by number is sensitive to minimum observable fragment size, age of the litter, and energy of the foreshore. Mean litter item weights should be used to calculate beach plastic loadings. Presence/absence of mega litter can distort monitoring by weight. Multiple surveys are needed to estimate mega litter statistics. Monitoring by weight can change the perception of the importance of litter sources (e.g., in our surveys, contribution from fishing was 6% by number, 41% by weight). In order to introduce consistency between beach surveys using visual methods by number, a standard minimum plastic fragment size should be introduced.

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“…It is estimated that 57,000e265,000 MT of plastic entered the oceans from riverine systems in 2018, according to a recent model considering the Human Development Index (HDI) (Mai et al, 2020). These estimates are much lower than those reported by Lebreton et al (2017) (1.15e2.41 million MT year À1 ), which are based on annual production and the concept of Mismanaged Plastic Waste (MPW).…”

Section: Plastic Contamination From Rivers To Estuariesmentioning

confidence: 98%

The fate of plastic litter within estuarine compartments: An overview of current knowledge for the transboundary issue to guide future assessments

Pinheiro

Agostini

Lima³

et al. 2021

Environmental Pollution

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Plastics can enter biogeochemical cycles and thus be found in most ecosystems. Most studies emphasize plastic pollution in oceanic ecosystems even though rivers and estuaries are acknowledged as the main sources of plastics to the oceans. This review detected few studies approaching the transboundary issue, as well as patterns of estuarine gradients in predicting plastic distribution and accumulation in water, sediments, and organisms. Quantities of plastics in estuaries reach up to 45,500 items m À3 in water, 567,000 items m À3 in sediment, and 131 items per individual in the biota. The role of rivers and estuaries in the transport of plastics to the ocean is far from fully understood due to small sample sizes, short-term approaches, sampling techniques that underestimate small plastics, and the use of site-specific sampling rather than covering environmental gradients. Microfibres are the most commonly found plastic type in all environmental matrices but efforts to re-calculate pathways using novel sampling techniques and estimates are incipient. Microplastic availability to estuarine organisms and rising/sinking is determined by polymer characteristics and spatio-temporal fluctuations in physicochemical, biological, and mineralogical factors. Key processes governing plastic contamination along estuarine trophic webs remain unclear, as most studies used "species" as an ecological unit rather than trophic/functional guilds and ontogenetic shifts in feeding behaviour to understand communities and intraspecific relationships, respectively. Efforts to understand contamination at the tissue level and the contribution of biofouling organisms as vectors of contaminants onto plastic surfaces are increasing. In conclusion, rivers and estuaries still require attention with regards to accurate sampling and conclusions. Multivariate analysis and robust models are necessary to predict the fate of micro-and macroplastics in estuarine environments; and the inclusion of the socio-economic aspects in modelling techniques seems to be relevant regarding management approaches.

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Global Riverine Plastic Outflows

Cited by 239 publications

References 43 publications

Modeling the Pathways and Accumulation Patterns of Micro- and Macro-Plastics in the Mediterranean

Modeling the Pathways and Accumulation Patterns of Micro- and Macro-Plastics in the Mediterranean

Monitoring Plastic Beach Litter by Number or by Weight: The Implications of Fragmentation

The fate of plastic litter within estuarine compartments: An overview of current knowledge for the transboundary issue to guide future assessments

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