Uptake and Release Kinetics of Organic Contaminants Associated with Micro- and Nanoplastic Particles

Unveiling the fast adsorption and desorption of heavy metals on/off nanoplastics by real-time in-situ potentiometric sensing

Nanoplastics (<1 μm) can serve as a transport vector of environmental pollutants (e.g., heavy metals) and change their toxicities and bioavailabilities. Up to date the behaviors of adsorption and desorption heavy metals on/off nanoplastics are largely unknown. Herein, polymeric membrane potentiometric ion sensors are proposed for in-situ assessment of the real-time kinetics of heavy metal adsorption and desorption on/off nanoplastics. Results show that nanoplastics can adsorb and release heavy metals in a fast manner, indicating their superior ability in transferring heavy metals. The adsorption behaviors are closely related to the characteristics of nanoplastics and background electrolytes. Particle aggregation and increases in salinity and acidity suppress the adsorption of heavy metals on nanoplastics. The desorption efficiencies of different heavy metals are Pb2+ (31 %) < Cu2+ (40 %) < Cd2+ (97 %). Our proposed method is applicable for the detection of the plastic pollutants with size <100 nm and of the samples with high salinities (e.g., seawater). This work would provide new insights into the assessment of environmental risks posed by nanoplastics and heavy metals.

Weathering increases the acute toxicity of plastic pellets leachates to sea-urchin larvae-a case study with environmental samples

Microplastics, particles under 5 mm, pervade aquatic environments, notably in Tarragona's coastal region (NE Iberian Peninsula), hosting a major plastic production complex. To investigate weathering and yellowness impact on plastic pellets toxicity, sea-urchin embryo tests were conducted with pellets from three locations-near the source and at increasing distances. Strikingly, distant samples showed toxicity to invertebrate early stages, contrasting with innocuous results near the production site. Follow-up experiments highlighted the significance of weathering and yellowing in elevated pellet toxicity, with more weathered and colored pellets exhibiting toxicity. This research underscores the overlooked realm of plastic leachate impact on marine organisms while proposes that prolonged exposure of plastic pellets in the environment may lead to toxicity. Despite shedding light on potential chemical sorption as a toxicity source, further investigations are imperative to comprehend weathering, yellowing, and chemical accumulation in plastic particles.

Effect of Mass Fraction on Leaching Kinetics of Hydrophobic Ultraviolet Stabilizers in Low-Density Polyethylene

The leaching kinetics of five hydrophobic ultraviolet (UV) stabilizers from low-density polyethylene (LDPE) (micro)fibers into water was evaluated in this study, with variation of the mass fraction (ω = 0.1-2.0 wt %) of the stabilizers. A one-dimensional convection-diffusion model for a cylindrical geometry, requiring partitioning between the LDPE fibers and water (KLDPEw) and the internal diffusion coefficients (DLDPE), was used to evaluate the leaching process and the leaching half-life of the target UV stabilizers at ω < 0.5 wt % (Case I). Diffusion through the aqueous boundary layer is the rate-determining step, and the leaching half-life is predicted to be very long (a few months to years) under unaffected conditions. When the UV stabilizers are supersaturated within LDPE fibers (i.e., ω > 0.5 wt %, Case II), the possible formation of a surficial crystal layer of the additives on the LDPE fiber extends the time scale for leaching compared to that in Case I due to the requirement of overcoming the crystallization energy. This study provides a fundamental understanding of the leaching profiles of plastic additives for assessing their potential chemical risks in aquatic environments; further studies under the relevant environmental conditions are required.

Interactions between phenanthrene and polystyrene micro/nano plastics: Implications for rice (Oryza sativa L.) toxicity

Micro/nano plastics (MPs/NPs) are widely distributed and are one of the global pollutants of current concern. Micro/nano plastics can adsorb a variety of persistent organic pollutants, and different particle sizes and surface charges affect the biological effects of MPs/NPs. Therefore, how the compound pollution of MPs/NPs with different particle sizes and organic pollutants produces toxic effects on plants needs to be further studied. We investigated the toxic effects of phenanthrene (Phe) and amino-modified PS (PS-NH2) with two particle sizes (50 nm, 5 μm) on rice. The stress mechanism of PS-NH2 was different between the two particle sizes. Moreover, 50 nm PS-NH2 inhibited stomatal conductance and transpiration rate, reduced photosynthetic rate, significantly enriched GO functions such as "DNA repair" and "DNA double-strand break," and caused severe DNA damage in rice. Notably, 5 μm PS-NH2 affected the gene expression of "photosynthetic lighting" and "photosynthetic antenna protein" in rice, decreased chlorophyll content, and inhibited rice growth. The toxicity of 50 nm PS-NH2 was stronger. In addition, we found that Phe reduced the toxicity of PS-NH2 with different particle sizes, and the relief effect of 50 nm PS-NH2+Phe was more evident. Further, 50 nm PS-NH2+Phe alleviated the toxicity by stimulating the activities of antioxidant enzymes, reducing oxidative damage to chloroplasts, and inhibiting photosynthesis. However, 5 μm PS-NH2+Phe can reduce the stress by reducing the degree of membrane lipid peroxidation, activating metabolic pathways related to the cell wall and cell membrane formation, and plant antitoxin biosynthesis. The results contribute to the understanding of the mechanism of toxicity of MPs/NPs and polycyclic aromatic hydrocarbons (PAHs) to crops.

Teratogenic effects of environmental concentration of plastic particles on freshwater organisms

Given the widespread presence of plastics, especially in micro- and nanoscale sizes, in freshwater systems, it is crucial to identify a suitable model organism for assessing the potential toxic and teratogenic effects of exposure to plastic particles. Until now, the early life stage of freshwater organisms and the regeneration capacity in relation to plastic particles exposure is a still poorly investigated topic. In this study, we examine the teratogenic effect on diatom Cocconeis placentula and cnidarian Hydra vulgaris under controlled exposure conditions of poly(styrene-co-methyl methacrylate) (P(S-co-MMA)) particles. Significant effects were observed at the lowest concentrations (0.1 μg/L). A significant increase in the teratological frequency in C. placentula and a significant decrease in the regeneration rate in H. vulgaris were found at the lowest concentration. The delay in hydra regeneration impaired the feeding capacity and tentacles reactivity at 96 h of exposure. No effects on diatom growth were observed upon exposure to P(S-co-MMA) particles (0.1, 1, 100, 10,000 μg/L) for 28 days and these findings agree with other studies investigating algal growth. The application of the Teratogenic Risk Index, modified for diatoms, highlighted a moderate risk for the lowest concentration evaluating C. placentula and low risk at the lowest and the highest concentrations considering H. vulgaris. This study suggests the importance of testing organisms belonging to different trophic levels as diverse teratogenic effects can be found and the need to evaluate environmentally relevant concentrations of plastic particles.

Effect of Polymer Aging on Uptake/Release Kinetics of Metal Ions and Organic Molecules by Micro- and Nanoplastics: Implications for the Bioavailability of the Associated Compounds

The main driver of the potential toxicity of micro- and nanoplastics toward biota is often the release of compounds initially present in the plastic, i.e., polymer additives, as well as environmentally acquired metals and/or organic contaminants. Plastic particles degrade in the environment via various mechanisms and at different rates depending on the particle size/geometry, polymer type, and the prevailing physical and chemical conditions. The rate and extent of polymer degradation have obvious consequences for the uptake/release kinetics and, thus, the bioavailability of compounds associated with plastic particles. Herein, we develop a theoretical framework to describe the uptake and release kinetics of metal ions and organic compounds by plastic particles and apply it to the analysis of experimental data for pristine and aged micro- and nanoplastics. In particular, we elucidate the contribution of transient processes to the overall kinetics of plastic reactivity toward aquatic contaminants and demonstrate the paramount importance of intraparticulate contaminant diffusion.

Compound effect and mechanism of oxidative damage induced by nanoplastics and benzo [a] pyrene

Nanoplastics and polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in soil environments. In order to objectively evaluate the toxic interaction between polystyrene nanoplastics (PS NPs) and benzo [a] pyrene (BaP), oxidative damage at the level of earthworm cells and biomacromolecules was investigated by experiments combined with molecular dynamics simulation. Studies on cells reveal that PS NPs and BaP had synergistic toxicity when it came to causing oxidative stress. Cellular reactive oxygen species (ROS) levels under combined pollutant exposure were 24% and 19% higher, respectively than when PS NPs and BaP were exposed alone (compared to the blank group). In addition, BaP and PS NPs inhibited the ability of CAT to decompose H2O2 by affecting the structure of the proximal amino acid Tyr 357 in the active center of CAT, which exacerbated oxidative stress to a certain extent. Therefore, the synergistic toxic effect of BaP and PS NPs is due to the mutual complement of the two to the induction of protein structural looseness, and the strengthening of the stability of the conjugate (CAT-BaP-PS) under the weak interaction. This work provides a new perspective and approach on how to talk about the toxicity of combined pollutants.

UV Dosage Unveils Toxic Properties of Weathered Commercial Bioplastic Bags

Previous studies indicated that weathered conventional plastics and bioplastics pose ecotoxicological risks. Here, the effects of artificial and natural weathering on the ecotoxicity of three compostable bags and a conventional polyethylene (PE) bag are investigated. With that aim, a 21-day artificial indoor weathering experiment featuring UV light, UV-filtered light, and darkness was run simultaneously to a 120-day outdoor littoral mesocosm exposure featuring natural light, UV-filtered light, and shaded conditions. Acute toxicity of so-weathered plastic specimens was tested in vivo using the sensitive Paracentrotus lividus sea-urchin embryo test. PE was nontoxic from the beginning and did not gain toxicity due to UV weathering. In contrast, for bioplastics, dry artificial UV weathering increased toxicity in comparison to the dark control. Weathering in outdoor mesocosm led to a rapid loss of toxic properties due to leaching in rainwater. With a higher UV dosage, a plastic-type-dependent regain of toxicity was observed, most likely driven by enhanced availability or transformation of functional additives or due to bioplastic degradation products. PE showed moderate UV absorbance, while bioplastics showed high UV absorbance. This study highlights the potential of biodegradable plastics to pose enhanced ecotoxicological risk due to weathering under environmentally relevant conditions.

Urban runoff mortality syndrome in zooplankton caused by tire wear particles

Stormwater runoff from roadways is a global threat to water quality, aquatic organisms, and ecosystems. Tire tread wear particles (TWP) from roadway runoff may lead to urban runoff mortality syndrome (URMS) in some aquatic organisms. We tested the hypothesis that urban runoff from roadways can kill zooplankton. Both roadway runoff and TWP leachate were acutely lethal to a model species, the water flea Daphnia pulex. Life table experiments further revealed the lowered survival rates, intrinsic rate of increase, average life span, and net productive rate of D. pulex when exposed to roadway runoff and TWP leachate. The tire rubber antioxidant N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) mainly contributed to the TWP toxicity. The toxicity of TWP and 6PPD extracted varied with time in nature. Cladocerans and rotifers were more sensitive to TWP and 6PPD than copepods. These results demonstrate the presence of URMS in zooplankton, which may cascade through food webs and affect aquatic ecosystems.

A protocol for lixiviation of micronized plastics for aquatic toxicity testing

Plastics contain various types and amounts of additives that can leach into the water column when entering aquatic ecosystems. Some leached plastic additives are hazardous to marine biota at environmentally relevant concentrations. Disparate methodological approaches have been adopted for toxicity testing of plastic leachates, making comparison difficult. Here we propose a protocol to standardize the methodology to obtain leachates from microplastics (MPs) for aquatic toxicity testing. Literature reviewing and toxicity tests using marine model organisms and different types of MPs were conducted to define the main methodological aspects of the protocol. Acute exposure to leachates from the studied plastics caused negative effects on the early life stages of sea urchins and marine bacteria. We provide recommendations of key factors influencing MPs lixiviation, such as MP size (<250 μm), solid-to-liquid ratio (1-10 g/L), mixing conditions (1-60 rpm), and lixiviation time (72 h). The proposed methodology was successful to determine the toxicity of leachates from different micronized plastics on marine biota. Our recommendations balance feasibility and environmental relevance, and their use would help ensure comparability amongst studies for a better assessment of the toxicity of plastic leachates on aquatic biota.

Counterintuitive Oxidation of Alcohols at Air-Water Interfaces

This study shows that the oxidation of alcohols can rapidly occur at air-water interfaces. It was found that methanediols (HOCH₂OH) orient at air-water interfaces with a H atom of the -CH₂- group pointing toward the gaseous phase. Counterintuitively, gaseous hydroxyl radicals do not prefer to attack the exposed -CH₂- group but the -OH group that forms hydrogen bonds with water molecules at the surface via a water-promoted mechanism, leading to the formation of formic acids. Compared with gaseous oxidation, the water-promoted mechanism at the air-water interface significantly lowers free-energy barriers from ∼10.7 to ∼4.3 kcal·mol^-1 and therefore accelerates the formation of formic acids. The study unveils a previously overlooked source of environmental organic acids that are bound up with aerosol formation and water acidity.

Organosilicon and inorganic silica inhibit polystyrene nanoparticles uptake in rice

Nanoplastics (NPs) have become an emerging global environmental problem, and the toxicity of polystyrene nanoplastics (PS-NPs) in rice plants has received widespread attention. However, few studies have focused on silicon (Si)-mediated interactions between PS-NPs and rice. Thus, two forms of Si (organosilicon/inorganic silica) treated rice cells were exposure of positively or negatively charged NPs, PS-NH₂ and PS-COOH, to evaluate the effects of Si for defense against PS-NPs toxicity in rice. The result showed PS-NH₂ nanoparticles were accumulated at relatively low levels in cells compared with that of PS-COOH, but induced a higher accumulation of hydrogen peroxide (H₂O₂) and superoxide radicals (O₂^•-). However, both organosilicon and inorganic silica can generate more negative potential on the surfaces of cell wall to absorb large numbers of positively charged PS-NH₂. In addition, they can prevent the uptake of both PS-NH₂ and PS-COOH through reducing the porosity on the surface of the cell walls. These finally alleviated the toxicity of oxidative stress caused by PS-NPs and improved the viability of rice cells. Our findings demonstrated the significant contribution of Si in combating PS-NPs in rice.

Shape dependence of the release rate of chemicals from plastic microparticles

The release of chemical additives from plastic microparticles in the aqueous phase represents a potential indirect threat for environment and biota. The estimate of the release timescale is demanded for drawing sensible conclusions on quantitative grounds. While the microparticles are generally taken to be spherical for ease of modelling, in reality the variety of shapes is large. Here, we face the problem of working out an empirical simple expression for estimating the release times for arbitrary shapes, assuming that the plastic material is in the rubbery state, that the dynamics inside the particle is a diffusion process, and that the release is irreversible. Our inspection is based on numerical simulations of the release process for randomly generated instances of regular and irregular geometries. The expression that we obtain allows one to estimate the release time in terms of the corresponding time (easy to compute) for the equal-volume spherical particle taken as reference, and of the ratio between the surface areas of particle and equivalent sphere.

Short-Term Exposure to Nanoplastics Does Not Affect Bisphenol A Embryotoxicity to Marine Ascidian Ciona robusta

Plastic pollution is recognized as a global environmental threat and concern is increasing regarding the potential interactions of the smallest fragments, nanoplastics (1 µm), with either physical and chemical entities encountered in the natural environment, including toxic pollutants. The smallest size of nanoplastics (<100nm) rebounds to their safety associated with remarkable biological, chemical and physical reactivity that allow them to interact with cellular machinery by crossing biological barriers and causing damage to living beings. Recent findings on nanoplastic occurrence in marine coastal waters, including the Mediterranean Sea, leave open the question on their ability to act as a vector of other contaminants of emerging concerns (CECs) concomitantly released by wastewater treatment plants and reaching marine coastal waters. Here, we assess for the first time the role of non-functionalized polystyrene nanoparticles (PS NPs, 20 nm) as a proxy for nanoplastics (1 and 10 µg/mL) alone and in combination with bisphenol A (BPA) (4.5 and 10 µM) on Ciona robusta embryos (22 h post fertilization, hpf) by looking at embryotoxicity through phenotypic alterations. We confirmed the ability of BPA to impact ascidian C. robusta embryo development, by affecting sensory organs pigmentation, either alone and in combination with PS NPs. Our findings suggest that no interactions are taking place between PS NPs and BPA in filtered sea water (FSW) probably due to the high ionic strength of seawater able to trigger the sorption surface properties of PS NPs. Further studies are needed to elucidate such peculiarities and define the risk posed by combined exposure to BPA and PS NPs in marine coastal waters.

Toxicity of tyre wear particle leachates to marine phytoplankton

Tyre wear particles (TWP) are some of the dominant sources of microplastics in the aquatic environment. Once TWP enter aquatic systems, they can leach certain plastic additives that can be potentially toxic to biota. However, little is known about the impact of TWP lixiviates on marine phytoplankton, the base of marine food webs. This study aims to determine the acute toxic effect of leachates derived from TWP on three phytoplankton species: the cryptophyte Rhodomonas salina, the diatom Thalassiosira weissflogii and the dinoflagellate Heterocapsa steinii, using the median effect concentration (EC₅₀) for specific growth rate as endpoint. Leachates were obtained by incubating 1 g L^-1 of < 250 µm TWP in artificial seawater for 3 days. Each phytoplankton species was exposed to leachates at five different concentrations, and cell concentrations were measured every 24 h over 3 days. Leachates from TWP were toxic to marine phytoplankton. The dinoflagellate H. steinii was the most sensitive species, with 72-h EC₅₀ of 23% leachate concentration, whereas R. salina and T. weissflogii exhibited EC₅₀ values of 64% and 73%, respectively. Our results suggest that TWP leachates have a negative effect on phytoplankton growth, although more field data on the concentration of TWPs and their leachates is needed to fully evaluate the environmental impact of TWP.

Adsorption of fluoranthene and phenanthrene by virgin and weathered polyethylene microplastics in freshwaters

Concern exists regarding potential health impacts associated with contaminants of emerging concern (CECs) that adsorb to microplastics (MPs). Previous studies have examined MPs as potential contaminant vectors in marine environments as opposed to freshwaters that represent drinking water sources. This study examined adsorption of two polycyclic aromatic hydrocarbons (PAHs), phenanthrene and fluoranthene, by virgin and weathered polyethylene (PE) in both artificial and natural freshwater matrices. Adsorption kinetics and isotherms conducted in artificial freshwater (AFW) consistently showed higher adsorption onto smaller (200 μm) PE when compared to 1090 μm PE. Adsorption mechanisms were primarily associated with hydrophobic interactions and monolayer chemisorption. As well, environmental factors including dissolved organic matter (DOC), pH, and polymer weathering also impacted adsorption. This work provides new insights regarding the adsorption of organic pollutants to better understand the risk of MPs in drinking water sources.

Polystyrene nanoparticles aggravate the adverse effects of di-(2-ethylhexyl) phthalate on different segments of intestine in mice

Emerging evidence indicates that nanoplastics (NPs) can transport organic pollutants such as di-(2-ethylhexyl) phthalate (DEHP) into organisms and induce adverse health effects. Nevertheless, the toxic effects of NPs combined with DEHP on mammalian intestine are still unclear. In this study, the C57BL6J mice were exposed to polystyrene nanoparticles (PSNPs), DEHP or them both for 30 days to determine their effects on different segments of intestine and the gut microbiota. As a result, DEHP alone or co-exposure to DEHP and PSNPs induced histological damages in all intestinal parts, mainly manifested as the decreased villus lengths, increased crypt depths in the duodenum, jejunum and ileum and decreased villus counts accompanied with decreased epithelial area in the colon. Moreover, decreased mucus coverage, down-regulated Muc2 expression levels as well as the broken tight junctions were observed in intestinal epithelium of mice, particularly obvious in the co-treatment groups. In general, as manifested by greater alterations in most of the parameters mentioned above, simultaneously exposed to PSNPs and DEHP seemed to induce enhanced toxic effects on intestine of mouse when compared with DEHP alone. Furthermore, the altered community composition of gut microbiota might at least partially contribute to these abnormalities. Overall, our results highlight the aggravated toxicity on different segments of intestine in mammalians due to co-exposure of PSNPs and DEHP, and these findings will provide valuable insights into the health risk of NPs and plastic additives.

Roadmap of environmental health research on emerging contaminants: Inspiration from the studies on engineered nanomaterials

Research on the environmental health of emerging contaminants is critical to understand their risks before causing severe harm. However, the low environmental concentrations, complex behaviors, and toxicology of emerging contaminants present enormous challenges for researchers. Here, we reviewed the research on the environmental health of engineered nanomaterials (ENMs), one of the typical emerging contaminants, to enlighten pathways for future research on emerging contaminants at their initial exploratory stage. To date, some developed pretreatment methods and detection technologies have been established for the determination of ENMs in natural environments. The mechanisms underlying the transfer and transformation of ENMs have been systematically explored in laboratory studies. The mechanisms of ENMs-induced toxicity have also been preliminarily clarified at genetic, cellular, individual, and short food chain levels, providing not only a theoretical basis for revealing the risk change and environmental health effects of ENMs in natural environments but also a methodological guidance for studying environmental health of other emerging contaminants. Nonetheless, due to the interaction of multiple environmental factors and the high diversity of organisms in natural environments, health effects observed in laboratory studies likely differ from those in natural environments. We propose a holistic approach and mesocosmic model ecosystems to systematically carry out environmental health research on emerging contaminants, obtaining data that determine the objectivity and accuracy of risk assessment.

The distinct toxicity effects between commercial and realistic polystyrene microplastics on microbiome and histopathology of gut in zebrafish

As a ubiquitous emerging pollutant, microplastics (MPs) have attracted widespread attention. At this stage, researchers mainly employed commercial MPs (CMPs) as the model particles to explore the toxic effects of MPs. But whether CMPs can reflect the effects of realistic MPs (RMPs) still remains unknown. Herein, the effects of commercial and realistic polystyrene MPs on gut microbiota of zebrafish were compared. Considering MPs co-exist with antibiotics in real environment, we further distinguished the effects of CMPs and RMPs when they co-existed with enrofloxacin (ENR). The results revealed that while both CMPs and RMPs significantly shifted the gut microbiota, CMPs exhibited stronger toxic effects and more severe damage to gut. Furthermore, ENR exhibited a distinct effect with both CMPs and RMPs on gut microbiota, while the addition of CMPs and RMPs significantly alleviated the toxicity of ENR. In addition, analysis via Kyoto Encyclopedia of Genes and Genomes pathway database revealed that seven major level 1 pathways associated with metabolism, information processing and diseases in the microbial community were affected. Taken together, this work is the first to report that CMPs could not represent RMPs in terms of toxicity and other behaviors, reminding people the limits of using CMPs in ecotoxicology studies.

Mesocosm trials reveal the potential toxic risk of degrading bioplastics to marine life

If biodegradable plastics tackle the marine plastic pollution problem sufficiently remains questionable. To gain more insight in degradability, performance, and the impact of degradation on the toxicity, commercial bags made from two biodegradable plastics and one conventional plastic (PE) were exposed for 120 days in a mesocosm featuring benthic, pelagic, and littoral habitat simulations. Degradability was assessed as weight loss, and specimens were tested for toxicity using Paracentrotus lividus sea-urchin larvae after different exposure times. Both biodegradable bags showed degradation within 120 days, with the littoral simulation showing the highest and the pelagic simulation the lowest decay. Disregarding habitat, the home-compostable plastic showed higher marine degradation than the industrial-compostable material. The relevant initial toxicity of both biopolymers was lost within 7 days of exposure, pointing towards easily leachable chemical additives as its cause. Interestingly, littoral exposed specimens gained toxicity after 120 days, suggesting UV- induced modifications that increase biopolymer toxicity.

In-situ quantitative monitoring the organic contaminants uptake onto suspended microplastics in aquatic environments

Microplastics act as a source of organic contaminants in aquatic environments and thus affect their environmental fate and toxicity. Because of the weak and reversible interactions between microplastics and organic species, the organic coronas vary with their surrounding environments. Thus, in order to evaluate the possible environmental risks of microplastics, methods for evaluating the dynamic uptake of organic contaminants onto suspended microplastics in aquatic environments are greatly desired. In this work, a UV-vis spectroscopy-based approach was developed for in-situ monitoring organic contaminants uptake onto suspended microplastics after correcting the light scattering interference from microplastics suspensions and establishing the nonlinear relationship between concentration and light absorbance of organic species. The inverse adding-doubling method based on radiative transfer theory was adopted to correct the light scattering effect of suspensions. Then, the resulting mixed absorption spectra were decomposed to calculate the concentrations of the aqueous and adsorbed organic species simultaneously with a nonlinear calibration method. The uptake processes of bisphenol A and p-nitrophenol onto nylon 66 microparticles were monitored with this approach and confirmed by high-performance liquid chromatography analysis. The approach was validated by applying it to natural water samples, and the equilibrium adsorption capacity was found to be interfered mainly by the protein-like substances. This approach has high accuracy, good reproducibility, remarkable universality, and ease of handling, and also provides a potential tool for characterizing the corona formation process on suspended particles both in natural and artificial environments, such as eco-corona formation and engineering surface modification on nano/micro-particles.

Nanoplastic State and Fate in Aquatic Environments: Multiscale Modeling

We now know that nanoplastics can harm aquatic organisms, but understanding ecological risk starts with understanding fate. We coupled population balance and fugacity models to predict the conditions under which nanoplastics remain as single particles, aggregate, or sediment and to predict their capacity to concentrate organic pollutants. We carried out simulations across a broad range of nanoplastic concentrations, particle sizes, and particle-particle interactions under a range of salinity and organic matter conditions. The model predicts that across plastic materials and environmental conditions, nanoplastics will either remain mostly dispersed or settle as aggregates with natural colloids. Nanoplastics of different size classes respond dissimilarly to concentration, ionic strength, and organic matter content, indicating that the sizes of nanoplastics to which organisms are exposed likely shift across ecological zones. We implemented a fugacity model of the Great Lakes to assess the organic pollution payload carried by nanoplastics, generating the expectation that nanoplastics would carry nine times more pollutants than microsized plastics and a threshold concentration of 10 μg/L at which they impact pollutant distribution. Our simulations across a broad range of factors inform future experimentation by highlighting the relative importance of size, concentration, material properties, and interactions in driving nanoplastic fate in aquatic environments.

Diffusive model to assess the release of chemicals from a material under intermittent release conditions

We consider the archetype situation of a chemical species that diffuses in a material and irreversibly escapes through the interface. In our setup, the interface switches between two states corresponding to ‘release phase’ (absorbing boundary) during which the species is released to the exterior, and ‘pause phase’ (reflecting boundary) during which the species is not released and its concentration profile inside the material partially relaxes back to uniformity. By combining numerical solution of the diffusion equation and statistical analysis of the outcomes, we derive upper and lower bounds and an empirical approximation for the amount of species released up to a certain time, in which the only information about the release-pause alternation schedule is the number of release phases and the average duration of a release phase. The methodology is developed thinking especially to dermal exposure assessment in the case of a slab-like homogeneous material irreversibly releasing chemicals during a number of contacts. However, upon proper extensions, this approach might be useful for inspecting other situations that are encountered, for instance, when dealing with leakage of chemicals in environmental contexts and regulatory toxicology.

Ecological implications beyond the ecotoxicity of plastic debris on marine phytoplankton assemblage structure and functioning

Plastic pollution is a global issue posing a threat to marine biota with ecological implications on ecosystem functioning. Micro and nanoplastic impact on phytoplankton autotrophic species (e.g., cell growth inhibition, decrease in chlorophyll a and photosynthetic efficiency and hetero-aggregates formation) have been largely documented. However, the heterogeneity of data makes rather difficult a comparison based on size (i.e. micro vs nano). In addition, knowledge gaps on the ecological impact on phytoplankton assemblage structure and functioning are evident. A new virtual meta-analysis on cause-effect relationships of micro and nanoplastics on phytoplankton species revealed the significant effect posed by polymer type on reducing cell density for tested PVC, PS and PE plastics. Linked with autotrophic phytoplankton role in atmospheric CO₂ fixation, a potential impact of plastics on marine carbon pump is discussed. The understanding of the effects of microplastics and nanoplastics on the phytoplankton functioning is fundamental to raise awareness on the overall impact on the first level of marine food web. Interactions between micro and nanoplastics and phytoplankton assemblages have been quite documented by in vitro examinations; but, further studies considering natural plankton assemblages and/or large mesocosm experiments should be performed to evaluate and try predicting ecological impacts on primary producers.

Simultaneous sorption behaviors of UV filters on the virgin and aged micro-high-density polyethylene under environmental conditions

The simultaneous sorption behaviors of four analytes from the UV filters group, benzophenone (BPh), 4-methylbenzylidene camphor (4MBC), benzophenone 3 (BPh3), and benzophenone 2 (BPh2) on virgin and aged high-density polyethylene (HDPE) with a particle size of 125 μm in milliQ and river water were examined in this study. The aging processes of HDPE particles were carried out with the use of simulated sunlight. Conducted research revealed that the sorption of UV filters on HDPE particles follows pseudo-second-order kinetics. A Temkin isothermal model best described the adsorption process for 4BMC, BPh, BPh3, BPh2 on aged HDPE in river water, and 4MBC, BPh, BPh3 on virgin HDPE in milliQ water. The adsorption of BPh2 onto virgin MPs in milliQ water was consistent with the Langmuir isothermal model. Environmental conditions and physicochemical properties of analytes influenced the sorption mechanism between UV filters and MPs particles. It was observed that the main mechanisms responsible for the sorption of BPh, 4MBC, BPh3, and BPh2 on the surface of HDPE are hydrophobic interactions, that may change through the involvement of electrostatic interactions.