To what extent are microplastics from the open ocean weathered?

It is necessary to better characterize plastic marine debris in order to understand its fate in the environment and interaction with organisms, the most common type of debris being made of polyethylene (PE) and polypropylene (PP). In this work, plastic debris was collected in the North Atlantic sub-tropical gyre during the Expedition 7th Continent sea campaign and consisted mainly in PE. While the mechanisms of PE photodegradation and biodegradation in controlled laboratory conditions are well known, plastic weathering in the environment is not well understood. This is a difficult task to examine because debris comes from a variety of manufactured objects, the original compositions and properties of which vary considerably. A statistical approach was therefore used to compare four sample sets: reference PE, manufactured objects, mesoplastics (5–20 mm) and microplastics (0.3–5 mm). Infrared spectroscopy showed that the surface of all debris presented a higher oxidation state than the reference samples. Differential scanning calorimetry analysis revealed that the microplastics were more crystalline contrarily to the mesoplastics which were similar to references samples. Size exclusion chromatography showed that the molar mass decreased from the references to meso- and microplastics, revealing a clear degradation of the polymer chains. It was thus concluded that the morphology of marine microplastic was much altered and that an unambiguous shortening of the polymer chains took place even for this supposedly robust and inert polymer.

Alexandra ter Halle, Lucie Ladirat, Marion Martignac, Anne Françoise Mingotaud, Olivier Boyron, Emile Perez, Environmental Pollution, Volume 227, August 2017, Pages 167–174

The article

The plastic in microplastics: A review

Microplastics [MPs], now a ubiquitous pollutant in the oceans, pose a serious potential threat to marine ecology and has justifiably encouraged focused biological and ecological research attention. But, their generation, fate, fragmentation and their propensity to sorb/release persistent organic pollutants (POPs) are determined by the characteristics of the polymers that constitutes them. Yet, physico-chemical characteristics of the polymers making up the MPs have not received detailed attention in published work. This review assesses the relevance of selected characteristics of plastics that composes the microplastics, to their role as a pollutant with potentially serious ecological impacts. Fragmentation leading to secondary microplastics is also discussed underlining the likelihood of a surface-ablation mechanism that can lead to preferential formation of smaller sized MPs.

Anthony L. Andrady, Marine Pollution Bulletin, Available online 24 April 2017, In Press

The article

Synthetic fibers as microplastics in the marine environment: A review from textile perspective with a focus on domestic washings

The ubiquity of plastic materials in the environment has been, for long, a matter of discussion. Smaller particles, named microplastics (< 5 mm), gained attention more recently and are now the focus of many studies, especially for their particularities regarding sources, characteristics and effects (e.g., surface-area-to-volume ratio which can increase their potential to transport toxic substances). Fibers from textile materials are a subgroup of microplastics and can be originated from domestic washings, as machine filters and wastewater treatment plants (WWTPs) are not specifically designed to retain them. Once in the environment, fibers can reach concentrations up to thousands of particles per cubic meter, being available to be ingested by a broad range of species. In this scenario, this review adds and details the textile perspective to the microplastics exploring nomenclature, characteristics and factors influencing emission, but also evidencing gaps in knowledge needed to overcome this issue. Preliminarily, general information about marine litter and plastics, followed by specific aspects regarding textile fibers as microplastics, were introduced. Then fiber sources to microplastic pollution were discussed, mainly focusing on domestic washings that pass through WWTPs. Studies that reveal domestic washing as microplastic sources are scarce and there is a considerable lack of standardization in methods as well as incorporation of textile aspects in experimental design. Knowledge gaps include laundry parameters (e.g., water temperature, use of chemicals) and textile articles characteristics (e.g., yarn type, fabric structure) orchestrated by consumers’ choice. The lack of information on the coverage and efficiency of sewage treatment systems to remove textile fibers also prevent a global understanding of such sources. The search of alternatives and applicable solutions should come from an integrated, synergic and global perspective, of both environmental and textile area, which still need to be fostered.

Flavia Salvador Cesa, Alexander Turra, Julia Baruque-Ramos, Science of The Total Environment, Volume 598, 15 November 2017, Pages 1116–1129

The article

The Arctic Ocean as a dead end for floating plastics in the North Atlantic branch of the Thermohaline Circulation

The subtropical ocean gyres are recognized as great marine accummulation zones of floating plastic debris; however, the possibility of plastic accumulation at polar latitudes has been overlooked because of the lack of nearby pollution sources. In the present study, the Arctic Ocean was extensively sampled for floating plastic debris from the Tara Oceans circumpolar expedition. Although plastic debris was scarce or absent in most of the Arctic waters, it reached high concentrations (hundreds of thousands of pieces per square kilometer) in the northernmost and easternmost areas of the Greenland and Barents seas. The fragmentation and typology of the plastic suggested an abundant presence of aged debris that originated from distant sources. This hypothesis was corroborated by the relatively high ratios of marine surface plastic to local pollution sources. Surface circulation models and field data showed that the poleward branch of the Thermohaline Circulation transfers floating debris from the North Atlantic to the Greenland and Barents seas, which would be a dead end for this plastic conveyor belt. Given the limited surface transport of the plastic that accumulated here and the mechanisms acting for the downward transport, the seafloor beneath this Arctic sector is hypothesized as an important sink of plastic debris.

The article

Microplastics elutriation system. Part A: Numerical modeling

The elutriation process has shown its efficiency to extract microplastics from sand and began to spread in the scientific community. This extraction technic requires knowing with accuracy the extraction velocities of particles. This study aims to test whether numerical modeling could help to calculate these velocities. From hydrodynamic equations, a numerical model has been developed and the outputs are compared to experimental extraction data. The results show, for the calculated velocities, the experimental plastic extraction yields will be higher than 90% for < 10% of sand contamination. The model also allows determining that, with the actual protocol, the maximum plastic density which can be extracted is about 1450 kg·m− 3 whereas the detrimental resuspension, which may occur during the column filling step, is highlighted. From model calculations, it arises that changes in the column dimensioning and the protocol operations need to be considered.

Mikaël Kedzierski, Véronique Le Tilly, Patrick Bourseau, Hervé Bellegou, Guy César, Olivier Sire, Stéphane Bruzaud, Marine Pollution Bulletin, Available online 3 May 2017, In Press

The article

Cadmium, lead and bromine in beached microplastics

Samples of microplastic (n = 924) from two beaches in south west England have been analysed by field-portable-x-ray fluorescence (FP-XRF) spectrometry, configured in a low-density mode and with a small-spot facility, for the heavy metals, Cd and Pb, and the halogen, Br. Primary plastics in the form of pre-production pellets were the principal type of microplastic (>70%) on both beaches, with secondary, irregularly-shaped fragments representing the remainder of samples. Cadmium and Pb were detected in 6.9% and 7.5% of all microplastics, respectively, with concentrations of either metal that exceeded 103 μg g−1 usually encountered in red and yellow pellets or fragments. Respective correlations of Cd and Pb with Se and Cr were attributed to the presence of the coloured, inorganic pigments, cadmium sulphoselenide and lead chromate. Bromine, detected in 10.4% of microplastics and up to concentrations of about 13,000 μg g−1, was mainly encountered in neutrally-coloured pellets. Its strong correlation with Sb, whose oxides are effective fire suppressant synergists, suggests the presence of a variety of brominated flame retardants arising from the recycling of plastics originally used in casings for heat-generating electrical equipment. The maximum bioaccessible concentrations of Cd and Pb, evaluated using a physiological extraction based on the chemical characteristics of the proventriculus-gizzard of the northern fulmar, were about 50 μg g−1 and 8 μg g−1, respectively. These concentrations exceed those estimated for the diet of local seabirds by factors of about 50 and 4, respectively.

Angelo Massos, Andrew Turner, Environmental Pollution, Volume 227, August 2017, Pages 139–145

The article