International audience | The nanoscale size of plastic debris makes them potential efficient vectors of many pollutants and more especially of metals. In order to evaluate this ability, nanoplastics were produced from microplastics collected on a beach exposed to the North Atlantic Gyre. The nanoplastics were characterized using multi-dimensional methods: asymmetrical flow field flow fractionation and dynamic light scattering coupled to several detectors. Lead (II) adsorption kinetics, isotherm and pH-edge were then carried out. The sorption reached a steady state after around 200 min. The maximum sorption capacity varied between 97% and 78.5% for both tested Pb concentrations. Lead (II) adsorption kinetics is controlled by chemical reactions with the nanoplastics surface and to a lesser extent by intraparticle diffusion. Adsorption isotherm modeling using Freundlich model demonstrated that NPG are strong adsorbents equivalent to hydrous ferric oxides such as ferrihydrite (log against 11.76 for NPG and ferrihydrite, respectively). The adsorption is dependent upon pH, in response to the Pb(II) adsorption by the oxygenated binding sites developed on account of the surface UV oxidation under environmental conditions. They could be able to compete with Fe or humic colloids for Pb binding regards to their amount and specific areas. Nanoplastics could therefore be efficient vectors of Pb and probably of many other metals as well in the environment.

International audience | The nanoscale size of plastic debris makes them potential efficient vectors of many pollutants and more especially of metals. In order to evaluate this ability, nanoplastics were produced from microplastics collected on a beach exposed to the North Atlantic Gyre. The nanoplastics were characterized using multi-dimensional methods: asymmetrical flow field flow fractionation and dynamic light scattering coupled to several detectors. Lead (II) adsorption kinetics, isotherm and pH-edge were then carried out. The sorption reached a steady state after around 200 min. The maximum sorption capacity varied between 97% and 78.5% for both tested Pb concentrations. Lead (II) adsorption kinetics is controlled by chemical reactions with the nanoplastics surface and to a lesser extent by intraparticle diffusion. Adsorption isotherm modeling using Freundlich model demonstrated that NPG are strong adsorbents equivalent to hydrous ferric oxides such as ferrihydrite (log against 11.76 for NPG and ferrihydrite, respectively). The adsorption is dependent upon pH, in response to the Pb(II) adsorption by the oxygenated binding sites developed on account of the surface UV oxidation under environmental conditions. They could be able to compete with Fe or humic colloids for Pb binding regards to their amount and specific areas. Nanoplastics could therefore be efficient vectors of Pb and probably of many other metals as well in the environment.

International audience | With the large amount of attention being given to microplastics in the environment, several researchers have begun to consider the fragmentation of plastics down to lower scales (i.e., the sub-micrometer scale). The term “nanoplastics” is still under debate, and different studies have set the upper size limit at either 1000 nm or 100 nm. The aim of the present work is to propose a definition of nanoplastics, based on our recently published and unpublished research definition of nanoplastics. We define nanoplastics as particles unintentionally produced (i.e. from the degradation and the manufacturing of the plastic objects) and presenting a colloidal behavior, within the size range from 1 to 1000 nm.

Evidence shows that the majority of aquatic field microplastics (MPs) could be microfibers (MFs) which can be originated directly from massive sources such as textile production and shedding from garments, agricultural textiles and clothes washing. In addition, wear and tear of tyres (TRWPs) emerges as a stealthy major source of micro and nanoplastics, commonly under-sampled/detected in the field. In order to compile the current knowledge in regards to these two major MPs sources, concentrations of concern in aquatic environments, their distribution, bulk emission rates and water mitigation strategies were systematically reviewed. Most of the aquatic field studies presented MFs values above 50%. MPs concentrations varied from 0.3 to 8925 particles m⁻³ in lakes, from 0.69 to 8.7 × 10⁶ particles m⁻³ in streams and rivers, from 0.16 to 192000 particles m⁻³ estuaries, and from 0 to 4600 particles m⁻³ in the ocean. Textiles at every stage of production, use and disposal are the major source of synthetic MFs to water. Laundry estimates showed an averaged release up to 279972 tons year⁻¹ (high washing frequency) from which 123000 tons would annually flow through untreated effluents to rivers, streams, lakes or directly to the ocean. TRWPs in the aquatic environments showed concentrations up to 179 mg L⁻¹ (SPM) in runoff river sediments and up to 480 mg g⁻¹ in highway runoff sediments. Even though average TRWR emission is of 0.95 kg year⁻¹ per capita (10 nm- 500 μm) there is a general scarcity of information about their aquatic environmental levels probably due to no-availability or inadequate methods of detection. The revision of strategies to mitigate the delivering of MFs and TRWP into water streams illustrated the importance of domestic laundry retention devices, Waste Water Treatment Plants (WWTP) with at least a secondary treatment and stormwater and road-runoff collectors quality improvement devices.

Wastewater treatment plants (WWTPs) are almost the only place where plastic fragments are artificially removed, resulting in mass accumulation of nanoplastics (NPs). In this research, four different concentrations (0 mg/L, 0.1 mg/L, 1 mg/L, 10 mg/L) of polystyrene nanoplastics (PS-NPs) were used to investigate the cell damage and nitrogen inhibition of activated sludge, exposed in a self-assembled SBR reactor for 30 days. Intracellular reactive oxides (ROS) and extracellular lactate dehydrogenase (LDH) increased with the rise of exposure concentration, and morphological analysis disclosed the creases, collapse, and even rupture of cell membranes. However, exposure damage (PS-NPs ≤ 1 mg/L) appeared to be reversible, attributed to that extracellular polymeric substances (EPS) secretion can thicken the three protective layers outside the membrane. PS-NPs did not disrupt the EPS chemical structure, but increased humic acid content. Prolonged exposure time (from 15 to 30 days) was directly related to the nitrogen inhibition. Due to the habitat changes under PS-NPs exposure, abundance and diversity of microorganisms in the original activated sludge decreased significantly, and the dominant phylum was occupied by Patescibacteria (PS-NPs = 10 mg/L). Changes in enzyme activities of AMO, NR, NIR, and NOR with exposure concentration may explain the conversion of nitrogen in SBR. This research broadens our horizons to understand the response mechanism of activated sludge bacteria to PS-NPs exposure individually and collectively.

The immense production of plastic polymers combined with their discordancy with nature has led to vast plastic waste contamination across the geosphere, from the oceans to freshwater reservoirs, wetlands, remote snowpacks, sediments, air and multiple other environments. These environmental pollutants include microplastics (MP), typically defined as small and fragmented plastics less than 5 mm in size, and nanoplastics (NP), particles smaller than a micrometer. The formation of micro and nanoplastics in aqueous media to date has been largely attributed to fragmentation of plastics by natural (i.e., abrasion, photolysis, biotic) or industrial processes. We present a novel method to create small microplastics (≲ 5 μm) and nanoplastics in water from a wide variety of plastic materials using a small volume of a solubilizer liquid, such as n-dodecane, in combination with vigorous mixing. When the suspensions or solutions are subjected to ultrasonic mixing, the particle sizes decrease. Small micro- and nanoparticles were made from commercial, real world and waste (aged) polyethylene, polystyrene, polycarbonate and polyethylene terephthalate, in addition to other plastic materials and were analyzed using dark field microscopy, Raman spectroscopy and particle size measurements. The presented method provides a new and simple way to create specific size distributions of micro- and nanoparticles, which will enable expanded research on these plastic particles in water, especially those made from real world and aged plastics. The ease of NP and small MP formation upon initial mixing simulates real world environments, thereby providing further insight into the behavior of plastics in natural settings.

The interactions of plastics and soil organisms are complex and inconsistent observations on the effects of plastics on soil organisms have been made in published studies. In this study, we assessed the effects of plastic exposure on plants, fauna and microbial communities, with a meta-analysis. Using a total of 2936 observations from 140 publications, we analysed how responses in plants, soil fauna and microorganisms depended on the plastic concentration, size, type, species and exposure media. We found that overall plastics caused substantial detrimental effects to plants and fauna, but less so to microbial diversity and richness. Plastic concentration was one of the most important factors explaining variations in plant and faunal responses. Larger plastics (>1 μm) caused unfavourable changes to plant growth, germination and oxidative stress, while nanoplastics (NPs; ≤ 1 μm) only increased oxidative stress. On the contrary, there was a clear trend showing that small plastics adversely affected fauna reproduction, survival and locomotion than large plastics. Plant responses were indifferent to plastic type, with most studies conducted using polyethylene (PE) and polystyrene (PS) plastics, but soil fauna were frequently more sensitive to PS than to PE exposure. Plant species played a vital role in some parameters, with the effects of plastics being considerably greater on vegetable plants than on cereal plants.

Micro and nanoplastics are new generation contaminants of global concern. It is important to evaluate the effects on edible products due to the presence of micro- and nano-sized plastics in the treated wastewater. A hydroponic experiment was carried out to explore the effect of polsytrene nanoplastics (PS-NPs; 20 nm) at different concentrations (0, 12.5, 25, and 50 mg L⁻¹) on Glycine max L. (soybean) seedlings for 7-days. In the current study, firstly the uptake of PS-NPs by Glycine max L. (soybean) roots were confirmed by laser confocal scanning microscope. Exposure to PS-NPs, negatively affected growth parameters and increased Fe, Zn and Mn contents in roots and leaves of soybean seedlings. PS-NPs treatments caused oxidative stress in soybean seedlings. The hydrogen peroxide and malondialdehyde contents, showed similar increase pattern in seedlings exposed to PS-NPs. Response to PS-NPs, the level of antioxidant enzymes (superoxide dismutase, catalase, ascorbate peroxidase, and guaiacol peroxidase) and proline content were generally enhanced in roots and leaves of soybean. The expression level of stress-related genes examined in the study included CSD5, FSD3, APX1, and POD up-regulated in PS-NPs treated-soybean seedlings in a tissue specific manner. The results of the present study showed the adverse effects of PS-NPs on soybean seedlings, which may have important implications for the risk assessment of NPs on crop production and environmental safety.

The characterisation of nanoplastics is much more difficult than that of microplastics. Herewith we employ Raman imaging to capture and visualise nanoplastics and microplastics, due to the increased signal-noise ratio from Raman spectrum matrix when compared with that from a single spectrum. The images mapping multiple characteristic peaks can be merged into one using logic-based algorithm, in order to cross-check these images and to further increase the signal-noise ratio. We demonstrate how to capture and identify microplastics, and then zoom down gradually to visualise nanoplastics, in order to avoid the shielding effect of the microplastics to shadow and obscure the nanoplastics. We also carefully compare the advantages and disadvantages of Raman imaging, while giving recommendations for improvement. We validate our approach to capture the microplastics and nanoplastics as particles released when we cut and assemble PVC pipes in our garden. We estimate that, during a cutting process of the PVC pipe, thousands of microplastics in the range of 0.1–5 mm can be released, along with millions of small microplastics in the range of 1–100 μm, and billions of nanoplastics in the range of <1 μm. Overall, Raman imaging can effectively capture microplastics and nanoplastics.

Once in the aquatic ecosystems, nanoplastics (NPls) can interact with other contaminants acting as vectors of transport and altering their toxicological effects towards organisms. Thus, the present study aims to investigate how polystyrene NPls (44 nm) interact with the herbicide phenmedipham (PHE) and affect its toxicity to zebrafish embryos. Single exposures to 0, 0.015, 0.15, 1.5, 15 and 150 mg/L NPls and 0.02, 0.2, 2 and 20 mg/L PHE were performed. Embryos were also exposed to the binominal combinations: 0.015 mg/L NPls + 2 mg/L PHE, 0.015 mg/L NPls + 20 mg/L PHE, 1.5 mg/L NPls + 2 mg/L PHE and 1.5 mg/L NPls + 20 mg/L PHE. Due to the low solubility of PHE in water, a solvent control was performed (0.01% acetone). PHE was quantified. Mortality, heartbeat and hatching rate, malformations appearance, locomotor behavior and biomarkers related to oxidative stress, neurotransmission and energy budgets were analyzed. During 96 h, NPls and PHE single and combined exposures did not affect embryos development. After 120 h, NPls induced hyperactivity and PHE induced hypoactivity. After 96 h, NPls increased catalase activity and PHE increased glutathione S-transferases activity. On the combination 0.015 mg/L NPls + 20 mg/L PHE, hyperactivity behavior was found, similar to 0.015 mg/L NPls, and cholinesterase activity was inhibited. Additionally, the combination 1.5 mg/L NPls + 20 mg/L PHE increased both catalase and glutathione S-transferases activities. The combination NPls with PHE affected more biochemical endpoints than the single exposures, showing the higher effect of the binominal combinations. Dissimilar interactions effects – no interaction, synergism and antagonism – between NPls and PHE were found. The current study shows that the effects of NPls on bioavailability and toxicity of other contaminants (e.g. PHE) cannot be ignored during the assessment of NPls environmental behavior and risks.