Plastics in the marine environment have become a major concern because of their persistence at sea, and adverse consequences to marine life and potentially human health. Implementing mitigation strategies requires an understanding and quantification of marine plastic sources, taking spatial and temporal variability into account. Here we present a global model of plastic inputs from rivers into oceans based on waste management, population density and hydrological information. Our model is calibrated against measurements available in the literature. We estimate that between 1.15 and 2.41 million tonnes of plastic waste currently enters the ocean every year from rivers, with over 74% of emissions occurring between May and October. The top 20 polluting rivers, mostly located in Asia, account for 67% of the global total. The findings of this study provide baseline data for ocean plastic mass balance exercises, and assist in prioritizing future plastic debris monitoring and mitigation strategies. Rivers provide a major pathway for ocean plastic waste, but effective mitigation is dependent on a quantification of active sources. Here, the authors present a global model of riverine plastic inputs, and estimate annual plastic waste of almost 2.5 million tonnes, with 86% sourced from Asia.

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River plastic emissions to the world's oceans.

There is a rising concern regarding the accumulation of floating plastic debris in the open ocean. However, the magnitude and the fate of this pollution are still open questions. Using data from the Malaspina 2010 circumnavigation, regional surveys, and previously published reports, we show a worldwide distribution of plastic on the surface of the open ocean, mostly accumulating in the convergence zones of each of the five subtropical gyres with comparable density. However, the global load of plastic on the open ocean surface was estimated to be on the order of tens of thousands of tons, far less than expected. Our observations of the size distribution of floating plastic debris point at important size-selective sinks removing millimeter-sized fragments of floating plastic on a large scale. This sink may involve a combination of fast nano-fragmentation of the microplastic into particles of microns or smaller, their transference to the ocean interior by food webs and ballasting processes, and processes yet to be discovered. Resolving the fate of the missing plastic debris is of fundamental importance to determine the nature and significance of the impacts of plastic pollution in the ocean.

/pdf/plastic-debris-in-the-open-ocean-1oqkhqu8cd.pdf

Plastic debris in the open ocean

https://scholarlypublications.universiteitleiden.nl/access/item%3A2978611/view

Microplastics in freshwater and terrestrial environments: Evaluating the current understanding to identify the knowledge gaps and future research priorities.

Microplastics in freshwater systems: A review of the emerging threats, identification of knowledge gaps and prioritisation of research needs

Distribution and importance of microplastics in the marine environment: A review of the sources, fate, effects, and potential solutions

Microplastic pollution in the surface waters of the Laurentian Great Lakes

In low-temperature refrigeration applications, mixtures containing carbon dioxide and refrigerants with low triple points are considered potential substitutes for the refrigerant R23, characterised by a very high global warming potential. This study provides pvTx measurements for the ternary mixture of carbon dioxide (CO2), difluoromethane (R32), and 1,1,1,2-tetrafluoroethane (R134a) carried out in the compressed liquid, superheated vapour, and two-phase regions. A vibrating tube densimeter was used to measure the compressed liquid density along eight isotherms evenly spaced from (283.15 to 353.15) K and for pressures from near saturation up to 35 MPa. An isochoric apparatus was used to measure the two-phase and superheated vapour pvTx properties along three isochores from (223.15 to 303.15) K. The measurement uncertainties were estimated to be lower than 1 kg∙m−3 for the liquid density and 0.02 m3∙kg−1 for the vapour specific volume. All the presented properties were compared with the calculations of the multi-fluid Helmholtz-energy explicit model. Both the default binary interaction parameters available in REFPROP 10.0 and new binary interaction parameters tuned on the presented data and the experimentally-determined thermodynamic properties collected from the literature have been used in the model. The tuned parameters provided lower deviations than the default parameters used in REFPROP 10.0. 

pvTx properties for carbon dioxide (CO2)/difluoromethane (R32)/1,1,1,2-tetrafluoroethane (R134a) ternary mixture measured in the compressed liquid, superheated vapour, and two-phase regions

Stephen Amato

Papers

Microplastic pollution in the surface waters of the Laurentian Great Lakes

pvTx properties for carbon dioxide (CO2)/difluoromethane (R32)/1,1,1,2-tetrafluoroethane (R134a) ternary mixture measured in the compressed liquid, superheated vapour, and two-phase regions