Increasing concern and research on the subject of plastic pollution has engaged the community of scientists working on the environmental health and safety of nanomaterials. While many of the methods ...developed in nano environment, health and safety work have general applicability to the study of particulate plastics, the nanometric size range has important consequences for both the analytical challenges of studying nanoscale plastics and the environmental implications of these incidental nanomaterials. Related to their size, nanoplastics are distinguished from microplastics with respect to their transport properties, interactions with light and natural colloids, a high fraction of particle molecules on the surface, bioavailability and diffusion times for the release of plastic additives. Moreover, they are distinguished from engineered nanomaterials because of their high particle heterogeneity and their potential for rapid further fragmentation in the environment. These characteristics impact environmental fate, potential effects on biota and human health, sampling and analysis. Like microplastics, incidentally produced nanoplastics exhibit a diversity of compositions and morphologies and a heterogeneity that is typically absent from engineered nanomaterials. Therefore, nanoscale plastics must be considered as distinct from both microplastics and engineered nanomaterials.
Due to their various properties as polymeric materials, plastics have been produced, used and ultimately discharged into the environment. Although some studies have shown their negative impacts on ...the marine environment, the effects of plastics on freshwater organisms are still poorly studied, while they could be widely in contact with this pollution. The current work aimed to better elucidate the impact and the toxicity mechanisms of two kinds of commercial functionalized nanoplastics, i.e., carboxylated polystyrene microspheres of, respectively, 350 and 50 nm (PS350 and PS50), and heteroaggregated PS50 with humic acid with an apparent size of 350 nm (PSHA), all used at environmental concentrations (0.1 to 100 µg L−1). For this purpose, two relevant biological and aquatic models—amphibian larvae, Xenopus laevis, and dipters, Chironomus riparius—were used under normalized exposure conditions. The acute, chronic, and genetic toxicity parameters were examined and discussed with regard to the fundamental characterization in media exposures and, especially, the aggregation state of the nanoplastics. The size of PS350 and PSHA remained similar in the Xenopus and Chironomus exposure media. Inversely, PS50 aggregated in both exposition media and finally appeared to be micrometric during the exposition tests. Interestingly, this work highlighted that PS350 has no significant effect on the tested species, while PS50 is the most prone to alter the growth of Xenopus but not of Chironomus. Finally, PSHA induced a significant genotoxicity in Xenopus.
The environmental fate and behavior of nanoplastics (NPs) and their toxicity against aquatic organisms are under current investigation. In this work, relevant physicochemical characterizations were ...provided to analyze the ecotoxicological risk of NPs in the aquatic compartment. For this purpose, heteroaggregates of 50 nm polystyrene nanospheres and natural organic matter were prepared and characterized. The kinetic of aggregation was assimilated to a reaction-limited colloid aggregation mode and led to the formation of heteroaggregates in the range of 100-500 nm. Toxicities of these heteroaggregates and polystyrene nanospheres (50 and 350 nm) were assessed for a large range of concentrations using four benthic and one planktonic algal species, in regards to particle states in the media. Heteroaggregates and nanospheres were shown to be stable in the exposure media during the ecotoxity tests. The algal species exhibited very low sensitivity (growth and photosynthetic activity), with the noteworthy exception of the planktonic alga, whose growth increased by more than 150% with the heteroaggregates at 1 µg L
. Despite the lack of a strong direct effect of the NPs, they may still impair the functioning of aquatic ecosystems by destabilizing the competitive interactions between species. Moreover, further work should assess the toxicity of NPs associated with other substances (adsorbed pollutants or additives) that could enhance the NP effects.
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 Kadsfreundlich=8.36 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.
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•Pb(II) binding experiments onto nanoplastics extracted from environmental micro-plastics were performed.•Pb(II) was largely bound onto nanoplastics by specific adsorption and intraparticle diffusion.•Nanoplastics could be significant vectors of metals in the environment.
Plastic pollution has become a worldwide concern. It was demonstrated that plastic breaks down to nanoscale particles in the environment, forming so-called nanoplastics. It is important to understand ...their ecological impact, but their structure is not elucidated. In this original work, we characterize the microstructure of oceanic polyethylene debris and compare it to the nonweathered objects. Cross sections are analyzed by several emergent mapping techniques. We highlight deep modifications of the debris within a layer a few hundred micrometers thick. The most intense modifications are macromolecule oxidation and a considerable decrease in the molecular weight. The adsorption of organic pollutants and trace metals is also confined to this outer layer. Fragmentation of the oxidized layer of the plastic debris is the most likely source of nanoplastics. Consequently the nanoplastic chemical nature differs greatly from plastics.
Plastic agricultural mulch films are used to improve the productivity of cultivable fields; however, their weathering and fragmentation could lead to release of microplastics and nanoplastics, both ...of which are considered potential health and environmental hazards. In this study, we examined the changes in physical and chemical properties of various plastic mulch films as they underwent different weathering processes. For this purpose, three commercially available polyethylene mulch films (one clear and two dark films) were evaluated under the following weathering conditions: laboratory treatments to evaluate the impacts of moisture, ultraviolet irradiation, pH, and freeze-thaw, as well as natural weathering conditions of a cold climate region. The morphologies and physicochemical properties of the polyethylene films were systematically studied following exposure to controlled and natural weathering. The three films, one of which was marketed as UV-resistant, underwent significant modifications. All weathered films were found to have increased surface roughness, suggesting that this could be the origin of microplastics or nanoplastics. While the dark pigments in the UV-resistant film protected the film against UV oxidation to some degree, they did not prevent deterioration caused by other types of weathering such as moisture, freeze-thaw, or natural weathering. The results of this study provide insights to understanding the fragmentation of polyethylene films into microplastics in winter and cold climate conditions.
A combination of parameters is involved during the natural weathering of plastic much films, which could lead to the acceleration of their fragmentation into microplastics or the leaching of additives.
The fate of plastic waste is a pressing issue since it forms a visible and long-lived reminder of the environmental impact of consumer habits. In this study, we examine the structural changes in the ...lamellar arrangements of semicrystalline polyethylene (PE) packaging waste with the aim of understanding the physical mechanisms of embrittlement in PE exposed to the marine environment. PE microplastics and macroplastics from identifiable PE packaging were collected in the Atlantic Ocean and compared to new PE boxes. Several experimental techniques interrogate the effects of environmental exposure on their bulk and surface properties. Size exclusion chromatography determines the molecular weight distribution of the PE polymer chains and differential scanning calorimetry gives the crystallinity. Small- and wide-angle X-ray scattering examines the packing of PE chains into semicrystalline lamellae. Longitudinal acoustic mode Raman spectroscopy provides a complementary measurement of the length of PE polymer chains extending through the crystalline lamellar domains. While there is a high degree of uncertainty in the time scale for the changes, the overall picture at the molecular scale is that although PE becomes more crystalline with environmental exposure, the lamellar order present in new packing boxes is disrupted by the weathering process. This process has important implications for embrittlement and subsequent degradation.
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Model emulsions were developed with or without commercial titanium dioxide nanoparticles (NP) carrying various surface treatments in order to get close physicochemical properties ...whatever the NP surface polarity (hydrophilic and hydrophobic). Rheology and texturometry highlighted that the macroscopic properties of the three formulated emulsions were similar. However, characterizations by optical microscopy, static light scattering and zetametry showed that their microstructures reflected the diversity of the incorporated NP surface properties. In order to use these model emulsions as tools for biological evaluations of the NP in use, they had to show the lowest initial microbiological charge and, specifically for the NP-free emulsion, the lowest bactericidal effect. Hence, formulae were developed preservative-free and a thermal sterilization step was conducted. Efficiency of the sterilization and its impact on the emulsion integrity were monitored. Results highlighted the effect of the NP surface properties: only the control emulsion and the emulsion containing hydrophilic NP fulfilled both requirements. To ensure the usability of these model emulsions as tools to evaluate the ‘NP effect’ on representative bacteria of the skin microflora (S. aureus and P. fluorescens), impact on the bacterial growth was measured on voluntary inoculated formulae.
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•Surface properties of coated TiO2-nanoparticles evolved during aging in model emulsions.•Impact on skin bacteria evaluated through two exposure scenarios mimicking use ...conditions.•Hydrophobic nanoparticles modified the physicochemical characteristics of model emulsions.•Hydrophobic nanoparticles favored the development of potential pathogenic bacteria.•Importance of the polarity of nanoparticles was highlighted regarding their impact on bacteria.
The impact of two differently coated TiO2-nanoparticles (NPs) was evaluated on two representative bacteria from the cutaneous microbiota (Staphylococcus aureus and Pseudomonas fluorescens) in conditions of use. Particles were coated in order to exhibit either hydrophilic or hydrophobic behavior. A first exposure scenario within some fresh/aged model emulsions was developed in order to measure both the impact of the NPs presence and their surface nature during the emulsions conservation. Thanks to this protocol, it was demonstrated that, during aging, the hydrophobic NPs modified the physicochemical characteristics of the emulsions, such as the pH or the colloids sizes, and favored the development of potential pathogenic bacteria. A second scenario was then envisaged, aiming to mimic the exposition of the skin, especially of the cutaneous bacteria, to NPs. Tested NPs were extracted from emulsions with different aging, and results highlighted the importance of both the NP coating nature and their history in emulsion. The different NPs impacts on the bacteria growth were discussed and linked to their surface properties modifications during aging, as polarity and charges. Finally, through two exposition scenarios, this work highlights the major impact of the NPs surface properties on bacteria.
•The critical coagulation concentration of bare nanoplastics in CaCl2 does not depend on the size of the plastics.•NOM has pronounced effects on the stability of larger nanoplastics.•Nanoplastics ...behave differently in synthetic seawater compared to a natural seawater matrix.•Interaction of nanoplastic aggregates with model silicon-based surfaces are more favorable in alginate and humic acid.
In this study, the aggregation kinetics of two sizes of polystyrene nanoplastics: 28 nm (NP28) and 220 nm (NP220), were investigated using time-resolved dynamic light scattering. The stability of the plastics was evaluated in: (i) the presence and absence of three natural organic matters (NOM) – the Suwannee River humic acid (HA) and fulvic acid (FA), and alginate (AL), (ii) varying concentrations of divalent salt and in artificial seawater (ASW) and (iii) natural surface waters (NW) with varying salinities. In the absence of NOM, the critical coagulation concentration (CCC) in CaCl2 was independent of particle size. The addition of HA enhanced aggregation via bridging, regardless of the size of the plastics. In contrast, the interaction of the plastics with alginate was size-dependent where alginate appeared to enhance aggregation by encapsulation for NP28 and by gel bridging for NP220, while the FA had little or no effect. In ASW, alginate stabilized the particle suspensions. Generally, the effects of the three NOM were more pronounced for the NP220 compared to the NP28. While the bare NP220 was more stable in natural seawater than in ASW and CaCl2 (at the CCC), there were few significant differences in the attachment efficiencies of the bare NP28 in these water matrices. Finally, in CaCl2, the interaction of nanoplastic aggregates with a model silicon-based surface was less repulsive in the presence of AL or HA than FA. This study highlights the importance of considering the interplay of different particle sizes and complex water chemistries when assessing the fate of nanoplastics in the environment.
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