Impact of heteroaggregation between microplastics and algae on particle vertical transport.

Understanding the impacts of microplastics (MPs) on aqueous environments requires understanding their transport dynamics and how their presence affects other natural processes and cycles. In this context, one aspect to consider is how MPs interact with freshwater snow (FWS), a mixture of algae and natural particles. FWS is one of the primary drivers of the flux of organic matter from the water surface to the bottom sediment, where zooplankton, diurnal migration, fish faecal pellets settling and turbulent mixing can also play prominent roles. Understanding how MPs and FWS heteroaggregation affects their respective settling velocities is important to assess not only MPs fate and transport but also their ecological impacts by altering FWS deposition and thereby nutrient cycling. In this present study, we obtained a mechanistic understanding of the processes controlling MPs settling dynamics and heteroaggregation with FWS and the subsequent impacts on the settling rates of both MPs and ballasted FWS. Here we used a plexiglass column equipped with a stereoscopic camera system to track the settling velocities of (1) MPs of various compositions, densities and morphologies, (2) FWS flocs and (3) MP-FWS agglomerates. For each experimental set, thousands of particles were tracked over a series of image sequences. We found that agglomerates with high-density MPs settled at least twofold faster than FWS alone, implying a much smaller residence time in the water column, except for cases with MP fibres or low-density plastics. These findings will help to refine MP fate models and, while contingent on MPs number, may impact biogeochemical cycles by changing the flux of nutrients contained in FWS to the sediment.

Differentiating Microplastics from Natural Particles in Aqueous Suspensions Using Flow Cytometry with Machine Learning.

Microplastics (MPs) in natural waters are heterogeneously mixed with other natural particles including algal cells and suspended sediments. An easy-to-use and rapid method for directly measuring and distinguishing MPs from other naturally present colloids in the environment would expedite analytical workflows. Here, we established a database of MP scattering and fluorescence properties, either alone or in mixtures with natural particles, by stain-free flow cytometry. The resulting high-dimensional data were analyzed using machine learning approaches, either unsupervised (e.g., viSNE) or supervised (e.g., random forest algorithms). We assessed our approach in identifying and quantifying model MPs of diverse sizes, morphologies, and polymer compositions in various suspensions including phototrophic microorganisms, suspended biofilms, mineral particles, and sediment. We could precisely quantify MPs in microbial phototrophs and natural sediments with high organic carbon by both machine learning models (identification accuracies over 93%), although it was not possible to distinguish between different MP sizes or polymer compositions. By testing the resulting method in environmental samples through spiking MPs into freshwater samples, we further highlight the applicability of the method to be used as a rapid screening tool for MPs. Collectively, this workflow can be easily applied to a diverse set of samples to assess the presence of MPs in a time-efficient manner.

Everything falls apart: How solids degrade and release nanomaterials, composite fragments, and microplastics.

To ensure the safe use of materials, one must assess the identity and quantity of exposure. Solid materials, such as plastics, metals, coatings and cements, degrade to some extent during their life cycle, and releases can occur during manufacturing, use and end-of-life. Releases (e.g., what is released, how does release happen, and how much material is released) depend on the composition and internal (nano)structures of the material as well as the applied stresses during the lifecycle. We consider, in some depth, releases from mechanical, weathering and thermal stresses and specifically address the use cases of fused-filament 3D printing, dermal contact, food contact and textile washing. Solid materials can release embedded nanomaterials, composite fragments, or micro- and nanoplastics, as well as volatile organics, ions and dissolved organics. The identity of the release is often a heterogenous mixture and requires adapted strategies for sampling and analysis, with suitable quality control measures. Control materials enhance robustness by enabling comparative testing, but reference materials are not always available as yet. The quantity of releases is typically described by time-dependent rates that are modulated by the nature and intensity of the applied stress, the chemical identity of the polymer or other solid matrix, and the chemical identity and compatibility of embedded engineered nanomaterials (ENMs) or other additives. Standardization of methods and the documentation of metadata, including all the above descriptors of the tested material, applied stresses, sampling and analytics, are identified as important needs to advance the field and to generate robust, comparable assessments. In this regard, there are strong methodological synergies between the study of all solid materials, including the study of micro- and nanoplastics. From an outlook perspective, we review the hazard of the released entities, and show how this informs risk assessment. We also address the transfer of methods to related issues such as tyre wear, advanced materials and advanced manufacturing, biodegradable polymers, and non-solid matrices. As the consideration of released entities will become more routine in industry via lifecycle assessment in Safe-and-Sustainable-by-Design practices, release assessments will require careful design of the study with quality controls, the use of agreed-on test materials and standardized methods where these exist and the adoption of clearly defined data reporting practices that enable data reuse, meta-analyses, and comparative studies.

eDNA Adsorption onto Microplastics: Impacts of Water Chemistry and Polymer Physiochemical Properties.

Adsorption of biomacromolecules onto polymer surfaces, including microplastics (MPs), occurs in multiple environmental compartments, forming an ecocorona. Environmental DNA (eDNA), genetic material shed from organisms, can adsorb onto MPs which can potentially either (1) promote long-range transport of antibiotic resistant genes or (2) serve to gain insights into the transport pathways and origins of MPs by analyzing DNA sequences on MPs. However, little is known about the capacity of MPs to adsorb eDNA or the factors that influence sorption, such as polymer and water chemistries. Here we investigated the adsorption of extracellular linear DNA onto a variety of model MP fragments composed of three of the most environmentally prevalent polymers (polyethylene, polyethylene terephthalate, and polystyrene) in their pristine and photochemically weathered states. Batch adsorption experiments in a variety of water chemistries were complemented with nonlinear modeling to quantify the rate and extent of eDNA sorption. Ionic strength was shown to strongly impact DNA adsorption by reducing or inhibiting electrostatic repulsion. Polyethylene terephthalate exhibited the highest adsorption capacity when normalizing for MP specific surface area, likely due to the presence of ester groups. Kinetics experiments showed fast adsorption (majority adsorbed under 30 min) before eventually reaching equilibrium after 1-2 h. Overall, we demonstrated that DNA quickly binds to MPs, with pseudo-first- and -second-order models describing adsorption kinetics and the Freundlich model describing adsorption isotherms most accurately. These insights into DNA sorption onto MPs show that there is potential for MPs to act as vectors for genetic material of interest, especially considering that particle-bound DNA typically persists longer in the environment than dissolved DNA.

Development of single-cell ICP-TOFMS to measure nanoplastics association with human cells.

Nanoplastics, solid polymer particles smaller than 1 µm, are suspected to be widely present in the environment, food and air, and may pose a potential threat to human health. Detecting nanoplastics in and associated with individual cells is crucial to understand their mechanisms of toxicity and potential harm. In this context, we developed a single-cell inductively coupled plasma time-of-flight mass spectrometry (sc-ICP-TOFMS) method for the sensitive and rapid quantification of metal-doped model nanoplastics in human cells. By providing multi-elemental fingerprints of both the nanoplastics and the cells, this approach can be advantageous in laboratory toxicological studies as it allows for the simultaneous acquisition of a full mass spectrum with high time resolution. As a proof-of-concept study, we exposed two different human cell lines relevant to inhalation exposures (A549 alveolar epithelial cells and THP-1 monocytes) to Pd-doped nanoplastics. The sc-ICP-TOFMS analysis revealed a similar dose-dependent endocytotic capacity of THP-1 and A549 cells for nanoplastics uptake, and particle internalization was confirmed by transmission electron microscopy. Moreover, single-cell quantification showed that a considerable proportion of the exposed cells (72% of THP-1; 67% of A549) did not associate with any nanoplastics after exposure to 50 µg L-1 for 24 h. This highlights the importance to include single-cell analysis in the future safety assessment of nanoplastics in order to account for heterogeneous uptake within cell populations and to identify the origins and response trajectories of nanoplastics in biological tissues. In this regard, sc-ICP-TOFMS can be a powerful approach to provide quantitative data on nanoplastics-cell associations at single cell level for a large number of individual cells.

Extraction and concentration of nanoplastic particles from aqueous suspensions using functionalized magnetic nanoparticles and a magnetic flow cell.

Although a considerable knowledge base exists for environmental contamination from nanoscale and colloidal particles, significant knowledge gaps exist regarding the sources, transport, distribution, and effects of microplastic pollution (plastic particles < 5 mm) in the environment. Even less is known regarding nanoplastic pollution (generally considered to be plastic particles < 1 µm). Due to their small size, nanoplastics pose unique challenges and potential risks. We herein report a technique focused on the concentration and measurement of nanoplastics in aqueous systems. Hydrophobically functionalized magnetic nanoparticles (HDTMS-FeNPs) were used as part of a method to separate and concentrate nanoplastics from environmentally relevant matrices, here using metal-doped polystyrene nanoplastics (PAN-Pd@NPs) to enable low-level detection and validation of the separation technique. Using a magnetic separation flow cell, PAN-Pd@NPs were removed from suspensions and captured on regenerated cellulose membranes. Depending on the complexity of solution chemistry, variable extraction rates were possible. PAN-Pd@ NPs were recovered from ultrapure water, synthetic freshwater, synthetic freshwater with a model natural organic matter isolate (NOM; Suwannee River Humic Acid), and from synthetic marine water, with recoveries for PAN-Pd@NPs of 84.9%, 78.9%, 70.4%, and 56.1%, respectively. During the initial method testing, it was found that the addition of NaCl was needed in the ultrapure water, synthetic freshwater and synthetic fresh water with NOM to induce particle aggregation and attachment. These results indicate that magnetic nanoparticles in combination with a flow-through system is a promising technique to extract nanoplastics from aqueous suspensions with various compositions.

Training the next generation of plastics pollution researchers: tools, skills and career perspectives in an interdisciplinary and transdisciplinary field.

Plastics pollution research attracts scientists from diverse disciplines. Many Early Career Researchers (ECRs) are drawn to this field to investigate and subsequently mitigate the negative impacts of plastics. Solving the multi-faceted plastic problem will always require breakthroughs across all levels of science disciplinarity, which supports interdisciplinary discoveries and underpins transdisciplinary solutions. In this context, ECRs have the opportunity to work across scientific discipline boundaries and connect with different stakeholders, including industry, policymakers and the public. To fully realize their potential, ECRs need to develop strong communication and project management skills to be able to effectively interface with academic peers and non-academic stakeholders. At the end of their formal education, many ECRs will choose to leave academia and pursue a career in private industry, government, research institutes or non-governmental organizations (NGOs). Here we give perspectives on how ECRs can develop the skills to tackle the challenges and opportunities of this transdisciplinary research field and how these skills can be transferred to different working sectors. We also explore how advisors can support an ECRs' growth through inclusive leadership and coaching. We further consider the roles each party may play in developing ECRs into mature scientists by helping them build a strong foundation, while also critically assessing problems in an interdisciplinary and transdisciplinary context. We hope these concepts can be useful in fostering the development of the next generation of plastics pollution researchers so they can address this global challenge more effectively.

Long-range atmospheric transport of microplastics across the southern hemisphere.

Airborne microplastics (MPs) can undergo long range transport to remote regions. Yet there is a large knowledge gap regarding the occurrence and burden of MPs in the marine boundary layer, which hampers comprehensive modelling of their global atmospheric transport. In particular, the transport efficiency of MPs with different sizes and morphologies remains uncertain. Here we show a hemispheric-scale analysis of airborne MPs along a cruise path from the mid-Northern Hemisphere to Antarctica. We present the inaugural measurements of MPs concentrations over the Southern Ocean and interior Antarctica and find that MPs fibers are transported more efficiently than MPs fragments along the transect, with the transport dynamics of MPs generally similar to those of non-plastic particles. Morphology is found to be the dominant factor influencing the hemispheric transport of MPs to remote Antarctic regions. This study underlines the importance of long-range atmospheric transport in MPs cycling dynamics in the environment.

Eco-Corona Formation on Plastics: Adsorption of Dissolved Organic Matter to Pristine and Photochemically Weathered Polymer Surfaces.

Plastic fate in freshwater systems is dependent on particle size, morphology, and physicochemical surface properties (e.g., charge, surface roughness, and hydrophobicity). Environmental aging processes, such as photochemical weathering and eco-corona formation due to dissolved organic matter (DOM) adsorption on plastic surfaces, can alter their physicochemical properties, affecting fate and transport. While plastic aging has been studied from a materials science perspective, its specific implications in environmental contexts remain less understood. Although photochemical weathering and eco-corona formation occur simultaneously in the environment, in this work, we systematically assessed the effects of photochemical weathering on the physicochemical properties of polymers (polyethylene, polypropylene, polyethylene terephthalate, and polystyrene) and how this influences the adsorption of DOMs (Suwannee River humic acid, fulvic acid, and natural organic matter) relative to pristine polymers. Pristine polymers initially had different and distinct physicochemical surface properties, but upon aging, they became more similar in terms of surface properties. Photochemical weathering resulted in a decrease in polymer film thickness, an increase in surface roughness, and hydrophilicity. DOM adlayers on the polymer surfaces resulted in more comparable wettability, effectively masking the initial polymer properties. Collectively, this study explores the physiochemical changes polymers undergo in laboratory studies mimicking environmental conditions. Understanding these changes is the initial step to rationalizing and predicting processes and interactions such as heteroaggregation that dictate the fate of plastics in the environment.

Tracking nanoplastics in freshwater microcosms and their impacts to aquatic organisms.

In this work, we used palladium-doped polystyrene NPLs (PS-NPLs with a primary size of 286 ± 4 nm) with an irregular surface morphology which allowed for particle tracking and evaluation of their toxicity on two primary producers (cyanobacterium, Anabaena sp. PCC7120 and green algae, Chlamydomonas reinhardtii) and one primary consumer (crustacean, Daphnia magna). the concentration range for Anabaena and C. reinhardtii was from 0.01 to 1000 mg/L and for D. magna, the range was from 7.5 to 120 mg/L.EC50 s ranged from 49 mg NPLs/L for D. magna (48hEC50 s) to 248 mg NPLs/L (72hEC50 s for C. reinhardtii). PS-NPLs induced dose-dependent reactive oxygen species overproduction, membrane damage and metabolic alterations. To shed light on the environmental fate of PS-NPLs, the short-term distribution of PS-NPLs under static (using lake water and sediments) and stirring (using river water and sediments) conditions was studied at laboratory scale. The results showed that most NPLs remained in the water column over the course of 48 h. The maximum percentage of settled particles (∼ 30 %) was found under stirring conditions in comparison with the ∼ 10 % observed under static ones. Natural organic matter increased the stability of the NPLs under colloidal state while organisms favored their settlement. This study expands the current knowledge of the biological effects and fate of NPLs in freshwater environments.

Direct Measurement of Microplastics by Carbon Detection via Single Particle ICP-TOFMS in Complex Aqueous Suspensions.

Multiple analytical techniques to measure microplastics (MPs) in complex environmental matrices are currently under development, and which is most suited often depends on the aim(s) of the research question and the experimental design. Here, we further broaden the suite of possible techniques which can directly detect MPs in suspension while differentiating the carbon contained in MPs from other natural particles and dissolved organic carbon (DOC). Single particle inductively coupled plasma mass spectrometry (sp-ICP-MS) is well suited to measuring particles at trace concentrations, and the use of ICP time-of-flight-MS (ICP-TOFMS) allows one to simultaneously monitor the entire elemental spectrum to assess the full elemental composition of individual particles through developing elemental fingerprints. Because carbon is not detected in a standard operation mode with icp TOF, a dedicated optimization was necessary. Subsequently, to assess the feasibility of monitoring 12C particle pulses for the detection of MPs in more complex natural waters, two proof-of-principle studies were performed to measure MPs in waters with environmentally relevant DOC backgrounds (≤20 mg/L) and in the presence of other carbon containing particles, here, algae. Elevated DOC concentrations did not impact the enumeration of particles in suspension, and individual MPs, single algae, and aggregates of MPs and algae were clearly distinguished. The simultaneous identification of different analytes of interest allows for multiplexed sp-ICP-TOFMS experiments utilizing elemental fingerprinting of particles and is a step forward in quantifying MPs in aqueous environmental samples.

Multi-generation exposure to polystyrene nanoplastics showed no major adverse effects in Daphnia magna.

Long-term impacts of plastics exposure to organisms, especially to the smallest plastics fraction, nanoplastics (NPs; ≤1 µm), are yet to be fully understood. The data concerning multiple generations are especially rare - an exposure scenario that is the most relevant from the standpoint of environmental reality aspect. Using Pd-doped 200 nm polystyrene NPs, which allowed for quantification of NPs in trace concentrations, the aim of the study was to evaluate the multigenerational impact of NPs for the freshwater crustacean Daphnia magna. Four consecutive 21-day exposures involving F0-F3 generations of D. magna were conducted according to OECD211. NPs impact (at 0.1 mg/L and 1 mg/L) was assessed in parallel to a comparative particle mesoporous SiO2 of similar size and shape (at 1 mg/L) to deconvolute impacts of variable particle chemistry. D. magna mortality, reproductive endpoints, body length (adults and offspring) and lipid content (offspring) were assessed upon NPs and SiO2 exposures. NPs association with adults and offspring was quantified by ICP-MS through the NPs Pd-dopant. The results showed no NPs impact on D. magna at 0.1 mg/L. At 1 mg NPs/L, the only statistically significant effect on adult organisms was increased fertility in the F3 generation. Conversely, SiO2 induced 80% mortality in F3 adult D. magna and the survived adults were significantly smaller and less fertile than those of other treatments. Both particles induced decreased size and lipid content in F3 offspring. The average NPs body burdens (ng NPs/mg D. magna dwt) for the adult and offspring D. magna were 105 ± 12 and 823 ± 440, respectively at 0.1 mg/L exposure and 503 ± 176 and 621 ± 235, respectively at 1 mg/L exposure. Finally, the results of this study add to the previous findings showing that multi-generation exposure to synthetic nano-sized particles of different chemistries may disturb the energy balance of D. magna.

Uptake, distribution and elimination of palladium-doped polystyrene nanoplastics in rainbow trout (Oncorhynchus mykiss) following dietary exposure.

The ingestion of nanoplastics (NPs) by fish has led to concerns regarding fish health and food chain transfer, but analytical constraints have hindered quantitative data collection on their uptake and depuration. We used palladium-doped polystyrene nanoplastics (PS-Pd NPs, ~200 nm) to track particle fate in rainbow trout (Oncorhynchus mykiss) during a week-long dietary exposure and subsequent 7-day depuration period on a control diet (no added PS-Pd NPs). At Day 3 and 7 of the exposure, and after depuration, the mid intestine, hind intestine, liver, gallbladder, kidney, gill and carcass were sampled. All organs and the carcass were analysed for total Pd content by inductively couple plasma mass spectrometry. After 3 days of exposure, the mid (32.5 ± 8.3 ng g-1) and hind (42.3 ± 8.2 ng g-1) intestine had significantly higher total Pd concentrations compared to the liver and carcass (1.3 ± 0.4 and 3.4 ± 1.1 ng g-1, respectively). At Day 7, there was no time-related difference in any organ (or the carcass) total Pd concentrations compared to Day 3. When the total Pd content was expressed as a body distribution based on mass of tissue, the carcass contained the highest fraction with 72.5 ± 5.2 % at Day 7, which could raise concerns over transfer to higher trophic levels. The total number of particles that entered the fish over the 7 days was 94.5 ± 13.5 × 106 particles, representing 0.07 ± 0.01 % of the Pd the fish had been fed. Following depuration, there was no detectable Pd in any organ or the carcass, indicating clearance from the fish. These data indicate that these NPs are taken into the internal organs and carcass of fish, yet removal of the exposure results in substantial excretion to below the limit of detection.

Microplastics and nanoplastics in the atmosphere: the potential impacts on cloud formation processes.

The presence of microplastics and nanoplastics (MnPs) in the atmosphere and their transport on a global scale has previously been demonstrated. However, little is known about their environmental impacts. MnPs could act as cloud condensation nuclei (CCN) or ice nucleating particles (INPs), affecting cloud formation processes. In sufficient quantities, they could change the cloud albedo, precipitation, and lifetime, collectively impacting the Earth's radiation balance and climate. In this perspective, we evaluate the potential impact of MnPs on cloud formation by assessing their ability to act as CCN or INPs. Based on an analysis of their physicochemical properties, we propose that MnPs can act as INPs and potentially as CCN, after environmental ageing processes, such as photochemical weathering, sorption of macromolecules or trace soluble species onto the particle surface. The actual climate impact(s) of MnPs depend on their abundance relative to other aerosols. The concentration of MnPs in the atmosphere is currently low, so they are unlikely to make a significant contribution to radiative forcing in regions exposed to other anthropogenic aerosol pollution. Nevertheless, MnPs will potentially cause non-negligible perturbations in unpolluted remote/marine clouds and generate local climate impacts, particularly in view of increased MnPs release to the environment in future. Further measurements coupled with better characterization of the physiochemical properties of MnPs will enable a more accurate assessment of climate impacts of MnPs to act as INP and CCN.

Embrace complexity to understand microplastic pollution.

Environmental cycling of microplastics and nanoplastics is complex; fully understanding these pollutants is hindered by inconsistent methodologies and experimentation within a narrow scope. Consistent methods are needed to advance plastic research and policy within the context of global environmental change.

Short Depuration of Oysters Intended for Human Consumption Is Effective at Reducing Exposure to Nanoplastics.

Nanoplastics (NPs; <1 µm) have greater availability to marine organisms than microplastics (1-5000 µm). Understanding NP uptake and depuration in marine organisms intended for human consumption is imperative for food safety, but until now it has been limited due to analytical constraints. Oysters (Crassostrea gigas) were exposed to polystyrene NPs doped with palladium (Pd), allowing the measurements of their uptake into tissues by inductively coupled plasma mass spectrometry (ICP-MS) combined with electron microscopy. Oysters were exposed for 6 days (d) to "Smooth" or "Raspberry" NPs, followed by 30 d of depuration with the aim of assessing the NP concentration in C. gigas following exposure, inferring the accumulation and elimination rates, and understanding the clearance of Pd NPs during the depuration period. After 6 d, the most significant accumulation was found in the digestive gland (106.6 and 135.3 µg g-1 dw, for Smooth and Raspberry NPs, respectively) and showed the most evident depuration (elimination rate constant KSmooth = 2 d-1 and KRaspberry = 0.2 d-1). Almost complete depuration of the Raspberry NPs occurred after 30 d. While a post-harvesting depuration period of 24-48 h for oysters could potentially reduce the NP content by 75%, more research to validate these findings, including depuration studies of oysters from the field, is required to inform practices to reduce human exposure through consumption.

Systematic development of extraction methods for quantitative microplastics analysis in soils using metal-doped plastics.

The inconsistency of available methods and the lack of harmonization in current microplastics (MPs) analysis in soils demand approaches for extraction and quantification which can be utilized across a wide variety of soil types. To enable robust and accurate assessment of extraction workflows, PET MPs with an inorganic tracer (Indium, 0.2% wt) were spiked into individual soil subgroups and standard soils with varying compositions. Due to the selectivity of the metal tracer, MPs recovery rates could be quickly and quantitatively assessed using ICP-MS. The evaluation of different methods specifically adapted to the soil properties were assessed by isolating MPs from complex soil matrices by systematically investigating specific subgroups (sand, silt, clay, non-lignified and lignified organic matter) before applying the workflow to standard soils. Removal of recalcitrant organic matter is one of the major hurdles in isolating MPs for further size and chemical characterization, requiring novel approaches to remove lignocellulosic structures. Therefore, a new biotechnological method (3-F-Ultra) was developed which mimics natural degradation processes occurring in aerobic (Fenton) and anaerobic fungi (CAZymes). Finally, a Nile Red staining protocol was developed to evaluate the suitability of the workflow for non-metal-doped MPs, which requires a filter with minimal background residues for further chemical identification, e.g. by µFTIR spectroscopy. Image analysis was performed using a Deep Learning tool, allowing for discrimination between the number of residues in bright-field and MPs counted in fluorescence mode to calculate a Filter Clearness Index (FCI). To validate the workflow, three well-characterized standard soils were analyzed applying the final method, with recoveries of 88% for MPs fragments and 74% for MPs fibers with an average FCI of 0.75. Collectively, this workflow improves our current understanding of how to adapt extraction protocols according to the target soil composition, allowing for improved MPs analysis in environmental sampling campaigns.

Nanoplastics removal during drinking water treatment: Laboratory- and pilot-scale experiments and modeling.

Microplastics detected in potable water sources and tap water have led to concerns about the efficacy of current drinking water treatment processes to remove these contaminants. It is hypothesized that drinking water resources contain nanoplastics (NPs), but the detection of NPs is challenging. We, therefore, used palladium (Pd)-labeled NPs to investigate the behavior and removal of NPs during conventional drinking water treatment processes including ozonation, sand and activated carbon filtration. Ozone doses typically applied in drinking water treatment plants (DWTPs) hardly affect the NPs transport in the subsequent filtration systems. Amongst the different filtration media, NPs particles were most efficiently retained when aged (i.e. biofilm coated) sand was used with good agreements between laboratory and pilot scale systems. The removal of NPs through multiple filtration steps in a municipal full-scale DWTP was simulated using the MNMs software code. Removal efficiencies exceeding 3-log units were modeled for a combination of three consecutive filtration steps (rapid sand filtration, activated carbon filtration and slow sand filtration with 0.4-, 0.2- and 3.0-log-removal, respectively). According to the results from the model, the removal of NPs during slow sand filtration dominated the overall NPs removal which is also supported by the laboratory-scale and pilot-scale data. The results from this study can be used to estimate the NPs removal efficiency of typical DWTPs with similar water treatment chains.

Assessing implications of nanoplastics exposure to plants with advanced nanometrology techniques.

Despite the increasing attention given to the impacts of nanoplastics in terrestrial environments, there is limited data about the effects on plants, and the quantitative information on uptake. In the present study, wheat plants grown in hydroponics were exposed to Pd-doped nanoplastics. This allowed us to quantify nanoplastics uptake and translocation to the shoots. Visualization of nanoplastics in roots was performed with synchrotron micro X-ray fluorescence (µXRF). Nanoplastics accumulated on the root epidermis, especially at the root tip and in root maturation zones. A close relationship between plant roots, rhizodeposits and nanoplastics behaviour was shown. Reinforcement of the cell wall in roots was evidenced using Fourier transform infrared spectroscopy (FTIR) and synchrotron-computed microtomography (µCT). Synchrotron-computed nanotomography (nanoCT) evidenced the presence of globular structures but they could not be identified as nanoplastics since they were observed both in the control and treated roots. By utilizing the inorganic tracer in the doped-nanoplastics, this study paves the road for elucidating interactions in more complex systems by using an integrative approach combining classical phytotoxicity markers with advanced nanometrology techniques.