Identification of polystyrene nanoplastics from natural organic matter in complex environmental matrices by pyrolysis-gas chromatography-mass spectrometry.

Due to the flux of plastic debris entering the environment, it becomes urgent to document and monitor their degradation pathways at different scales. At the colloidal scale, the systematic hetero-association of nanoplastics with the natural organic matter complexifies the ability to detect plastic signatures in the particle collected in the various environments. The current techniques used for microplastics could not discriminate the polymers at the nanoscale from the natural macromolecules, as the plastic mass in the aggregate is within the same order. Only a few methods are available concerning nanoplastics identification in complex matrices, with the coupling of pyrolysis with gas chromatography and mass spectrometry (Py-GC-MS) as one of the most promising due to its mass-based detection. However, natural organic matter in environmental samples interferes with similar pyrolysis products. These interferences are even more critical for polystyrene polymers as this plastic presents no dominant pyrolysis markers, such as polypropylene, that could be identified at trace concentrations. Here, we investigate the ability to detect and quantify polystyrene nanoplastics in a rich phase of natural organic matter proposed based on the relative ratio of pyrolyzates. The use of specific degradation products (styrene dimer and styrene trimer) and the toluene/styrene ratio (RT/S) are explored for these two axes. While the size of the polystyrene nanoplastics biased the pyrolyzates of styrene dimer and trimer, the RT/S was correlated with the nanoplastics mass fraction in the presence of natural organic matter. An empirical model is proposed to evaluate the relative quantity of polystyrene nanoplastics in relevant environmental matrices. The model was applied to real contaminated soil by plastic debris and literature data to demonstrate its potential.

Volatile organic compounds identification and specific stable isotopic analysis (δ13C) in microplastics by purge and trap gas chromatography coupled to mass spectrometry and combustion isotope ratio mass spectrometry (PT-GC-MS-C-IRMS).

Microplastics (MPs) have become one of the major global environmental issues in recent decades due to their ubiquity in the environment. Understanding MPs source origin and reactivity is urgently needed to better constrain their fate and budget. Despite improvements in analytical methods to characterize MPs, new tools are needed to help understand their sources and reactivity in a complex environment. In this work, we developed and applied an original Purge-&-Trap system coupled to a GC-MS-C-IRMS to explore the δ13C compound-specific stable isotope analysis (CSIA) of volatile organic compounds (VOC) embedded in MPs. The method consists of heating and purging MP samples, with VOCs being cryo-trapped on a Tenax sorbent, followed by GC-MS-C-IRMS analysis. The method was developed using a polystyrene plastic material showing that sample mass and heating temperature increased the sensitivity while not influencing VOC δ13C values. This robust, precise, and accurate methodology allows VOC identification and δ13C CSIA in plastic materials in the low nanogram concentration range. Results show that the monomer styrene displays a different δ13C value (- 22.2 ± 0.2‰), compared to the δ13C value of the bulk polymer sample (- 27.8 ± 0.2‰). This difference could be related to the synthesis procedure and/or diffusion processes. The analysis of complementary plastic materials such as polyethylene terephthalate, and polylactic acid displayed unique VOC δ13C patterns, with toluene showing specific δ13C values for polystyrene (- 25.9 ± 0.1‰), polyethylene terephthalate (- 28.4 ± 0.5‰), and polylactic acid (- 38.7 ± 0.5‰). These results illustrate the potential of VOC δ13C CSIA in MP research to fingerprint plastic materials, and to improve our understanding of their source cycle. Further studies in the laboratory are needed to determine the main mechanisms responsible for MPs VOC stable isotopic fractionation.

NMR investigation on the thermogelation of partially hydrolysed polyacrylamide/polyethylenimine mixtures.

Since the introduction of polyethylenimine (PEI)/acrylamide-based polymer gel systems in the late 90's, the literature knowledge on the crosslinking mechanisms between the various polymers (PAM, PHPA, and PatBA) and the crosslinker (PEI) was only limited to observations on gelation times and gel strength variations compared to other gel systems. In this paper, classic proton and carbon nuclear magnetic resonance "NMR" experiments and advanced 2D DOSY and NOESY techniques were employed for studying the interactions between the amine groups of PEI and amide or carboxylate groups of partially hydrolysed polyacrylamide (PHPA). Among the many possibilities, we showed that the interaction occurring during thermogelation is mainly due to covalent bonding. The latter results from a transamidification reaction between the polymer amide groups and the primary amines of the crosslinker. The reaction, at high temperatures, was accompanied by some hydrolysis of the polymer amide groups. Consequently, the kinetics of the reaction and hydrolysis were evaluated and fitted using pseudo first-order equations where the hydrolysis kinetics was found to be three times lower than that of the reaction.

Nanoplastics Identification in Complex Environmental Matrices: Strategies for Polystyrene and Polypropylene.

Identification of nanoplastics in complex environmental matrices remains a challenge. Despite the increase in nanoplastics studies, there is a lack of studies dedicated to nanoplastics detection, partially explained by their carbon-based structure, their wide variety of composition, and their low environmental concentrations compared to the natural organic matter. Here, pyrolysis coupled to a GCMS instrumental setup provided a relevant analytical response for polypropylene and polystyrene nanoplastic suspensions. Specific pyrolysis markers and their indicative fragment ions were selected and validated. Possible interferences with environmental matrices were explored by spiking nanoplastics in various organic matter suspensions (i.e., algae, soil natural organic matter, and soil humic acid) and analyzing an environmental suspension of nanoplastics. While a rapid polypropylene nanoplastics identification was validated, polystyrene nanoplastics require preliminary treatment. The strategies presented herein open new possibilities for the detection/identification of nanoplastics in environmental matrices such as soil, dust, and biota.

Environmental Fate Modeling of Nanoplastics in a Salinity Gradient Using a Lab-on-a-Chip: Where Does the Nanoscale Fraction of Plastic Debris Accumulate?

The aim of this study is to demonstrate how the flow and diffusion of nanoplastics through a salinity gradient (SG), as observed in mangrove swamps (MSPs), influence their aggregation pathways. These two parameters have never yet been used to evaluate the fate and behavior of colloids in the environment, since they cannot be incorporated into classical experimental setups. Land-sea continuums, such as estuaries and MSP systems, are known to be environmentally reactive interfaces that influence the colloidal distribution of pollutants. Using a microfluidic approach to reproduce the SG and its dynamics, the results show that nanoplastics arriving in a MSP are fractionated. First, a substantial fraction rapidly aggregates to reach the microscale, principally governed by an orthokinetic aggregation process and diffusiophoresis drift. These large nanoplastic aggregates eventually float near the water's surface or settle into the sediment at the bottom of the MSP, depending on their density. The second, smaller fraction remains stable and is transported toward the saline environment. This distribution results from the combined action of the spatial salt concentration gradient and orthokinetic aggregation, which is largely underestimated in the literature. Due to nanoplastics' reactive behavior, the present work demonstrates that mangrove and estuarine systems need to be better examined regarding plastic pollution.

Chemicals sorbed to environmental microplastics are toxic to early life stages of aquatic organisms.

Microplastics are ubiquitous in aquatic ecosystems, but little information is currently available on the dangers and risks to living organisms. In order to assess the ecotoxicity of environmental microplastics (MPs), samples were collected from the beaches of two islands in the Guadeloupe archipelago, Petit-Bourg (PB) located on the main island of Guadeloupe and Marie-Galante (MG) on the second island of the archipelago. These samples have a similar polymer composition with mainly polyethylene (PE) and polypropylene (PP). However, these two samples are very dissimilar with regard to their contamination profile and their toxicity. MPs from MG contain more lead, cadmium and organochlorine compounds while those from PB have higher levels of copper, zinc and hydrocarbons. The leachates of these two samples of MPs induced sublethal effects on the growth of sea urchins and on the pulsation frequency of jellyfish ephyrae but not on the development of zebrafish embryos. The toxic effects are much more marked for samples from the PB site than those from the MG site. This work demonstrates that MPs can contain high levels of potentially bioavailable toxic substances that may represent a significant ecotoxicological risk, particularly for the early life stages of aquatic animals.

Nanoplastic Labelling with Metal Probes: Analytical Strategies for Their Sensitive Detection and Quantification by ICP Mass Spectrometry.

The detection and quantification of nanoplastics in aquatic environments is one of the major challenges in environmental and analytical research nowadays. The use of common analytical techniques for this purpose is not only hampered by the size of nanoplastics, but also because they are mainly made of carbon. In addition, the expected concentrations in environmental samples are below the detection limit of the majority of analytical techniques. In this context, the great detection capabilities of Inductively Coupled Plasma Mass Spectrometry (ICP-MS) in its Single Particle mode (SP-ICP-MS) have made of this technique a good candidate for the analysis of nanoplastics. Since the monitoring of carbon by ICP-MS faces several difficulties, the use of metal tags, taking advantage of the great potential of nanoplastics to adsorb chemical compounds, has been proposed as an alternative. In this perspectives paper, three different strategies for the analysis of polystyrene (PS) nanoplastics by SP-ICP-MS based on the use of metals species (ions, hydrophobic organometallic compound, and nanoparticles) as tags are presented and discussed. Advantages and disadvantages of each strategy, which rely on the labelling process, are highlighted. The metal nanoparticles labelling strategy is shown as a promising tool for the detection and quantification of nanoplastics in aqueous matrices by SP-ICP-MS.

A Novel Strategy for the Detection and Quantification of Nanoplastics by Single Particle Inductively Coupled Plasma Mass Spectrometry (ICP-MS).

A method for the detection and quantification of nanoplastics (NPTs) at environmentally relevant concentrations was developed. It is based on conjugating nanoplastics with functionalized metal (Au)-containing nanoparticles (NPs), thus making them detectable by highly sensitive inductively coupled plasma mass spectrometry (ICP-MS) operated in single particle (SP) mode. The selectivity of the method was achieved by the coupling of negatively charged carboxylate groups present at the surface of nanoplastics with a positively charged gelatin attached to the custom-synthesized AuNPs. The adsorbed Au produced a SP-ICP-MS signal allowing the counting of individual nanoplastic particles, and hence their accurate quantification (<5% error). Polystyrene (PS) particle models with controlled surface functionalization mimicking the nanoplastics formed during natural degradation of plastic debris were used for the method development. The nanoplastic number concentration quantification limit was calculated at 8.4 × 105 NPTs L-1 and the calibration graph was linear up to 3.5 × 108 NPTs L-1. The method was applied to the analysis of nanoplastics of up to 1 µm in drinking, tap, and river water. The minimum detectable and quantifiable size depended on the degree of functionalization and the surface available for labeling. For a fully functionalized nanoplastic, the lower size detectable by this strategy is reported as 135 nm. In this study, authors use the recommendation for the definition of nanoplastics as plastic particles with sizes ranging between 1 nm and 1 µm, although it has not been accepted by a dedicated organization.

Rheological behaviour and adsorption phenomenon of a polymer-particle composite based on hydrolysed polyacrylamide/functionalized poly(styrene-acrylic acid) microspheres.

The properties in aqueous solution of polymer-particle composites (PPC) depend on the size and the concentration of both the particles and the polymers as well as the interactions between them. In this work, rheological behaviour was studied in a semi-diluted regime of partially hydrolysed polyacrylamide (HPAM) with 2Rg/d a particle diameter/polymer gyration radius (Rg) ratio and a confinement parameter (pc) that were both greater than 1. Rg is the polymer gyration radius and d the particle diameter. pc characterizes the inter-particle distance (ID) with respect to the polymer size (pc = ID/2Rg) and depends on the concentration and size of the particles. We highlighted the PPC thickening effects as a function of the number of carboxylic functions on the surface of the polystyrene particles (PSL) obtained by free soap free emulsion polymerization (0.16-1.2 mmol g-1 of COOH). Thickening increases linearly with surface functionality for a pc of less than 10. This behaviour has been correlated to the polymer-particle interactions, which was demonstrated by adsorption measurements in dilute solution (12-22 mg g-1 of HPAM on PSL). Adsorption was quantified by zero-shear capillary viscosity measurements in a microfluidic device. In contrast, a thinning effect was observed for a pc greater than 10, which is also related to the salt effect studies (6-12 g L-1 in NaCl).

Asymmetrical flow field flow fractionation methods to characterize submicron particles: application to carbon-based aggregates and nanoplastics.

In the last 10 years, asymmetrical flow field flow fractionation (AF4) has been one of the most promising approaches to characterize colloidal particles. Nevertheless, despite its potentialities, it is still considered a complex technique to set up, and the theory is difficult to apply for the characterization of complex samples containing submicron particles and nanoparticles. In the present work, we developed and propose a simple analytical strategy to rapidly determine the presence of several submicron populations in an unknown sample with one programmed AF4 method. To illustrate this method, we analyzed polystyrene particles and fullerene aggregates of size covering the whole colloidal size distribution. A global and fast AF4 method (method O) allowed us to screen the presence of particles with size ranging from 1 to 800 nm. By examination of the fractionating power F d, as proposed in the literature, convenient fractionation resolution was obtained for size ranging from 10 to 400 nm. The global F d values, as well as the steric inversion diameter, for the whole colloidal size distribution correspond to the predicted values obtained by model studies. On the basis of this method and without the channel components or mobile phase composition being changed, four isocratic subfraction methods were performed to achieve further high-resolution separation as a function of different size classes: 10-100 nm, 100-200 nm, 200-450 nm, and 450-800 nm in diameter. Finally, all the methods developed were applied in characterization of nanoplastics, which has received great attention in recent years. Graphical Absract Characterization of the nanoplastics by asymmetrical flow field flow fractionation within the colloidal size range.

UV-mediated thiol-ene click reactions for the synthesis of drug-loadable and degradable gels based on copoly(2-oxazoline)s.

An 80-membered library of gels composed of monofunctional 2-ethyl-2-oxazoline and 2-nonyl-2-oxazoline and one of four selected difunctional 2-oxazolines (containing either ether or ester bonds) were synthesized by microwave-assisted ring-opening polymerizations. The difunctional 2-oxazolines were prepared from the thiol-ene reaction of glycol dimercaptoacetate or 2,2'-(ethylenedioxy)diethanethiol and 2-but-3'-enyl-2-oxazoline or 2-dec-9'-enyl-2-oxazoline. 53 of the gels exhibited glass-transition temperatures, which ranged from -5.9 to 45.3 °C. 13 Derivatives exhibited glass-transition temperatures in the range from 20 to 30 °C, which renders them stiff at room temperature and flexible at body temperature. The gels that did not contain any 2-ethyl-2-oxazoline acted as lipogels, whereas the gels that did not contain any 2-nonyl-2-oxazoline acted as hydrogels; all other gels may be classified as amphigels. The swelling degrees were measured by gravimetry and maximum swelling degrees of 6 (in water) were observed for the gels with the lowest degrees of crosslinking. In a second approach, the synthesis of crosslinked networks had been achieved by performing the polymeranalogous thiol-ene reaction of copoly(2-oxazoline)s containing olefinic side-chains and glycol dimercaptoacetate. This soft strategy enabled the straightforward loading of such gels with active pharmaceutical ingredients without altering them. This method delivered gels with selected composition exhibiting a targeted disc-shape and loaded with active pharmaceutical ingredients from one-step syntheses. The maximum swelling degrees of these specimens were found to be in accordance with the ones from the first route investigated. Preliminary degradation studies were performed at 25 °C; these types of gels were found to be degraded in alkaline media as well as by esterases.

Contaminants, biochemical methane Potential, and biodegradability of different Bio-Waste Categories: Guidance for anaerobic digestion.

This study evaluated the anaerobic digestion suitability of bio-waste from different sources by comparing their biochemical methane potential (BMP), biodegradability (BI), and content of contaminants (heavy metals and physical impurities) - an often-overlooked factor but one of particular concern in bio-waste. Predominant heavy metals included Cu and Zn, while recurring physical impurities comprised plastics and organic non-biodegradable matter. Food waste from food processing plants were most suitable, exhibiting low contamination and high biogas conversion (BMP>549 NmLCH4/gVS and BI>86 %). Conversely, organic fractions from mechanical biological treatment were highly contaminated, while green waste displayed low biogas conversion (BMP<368 NmLCH4/gVS and BI<72 %). Food waste from households and medium/large-sized producers also demonstrated high biogas conversion, but variable contamination levels could compromise their suitability. Assessing contaminants alongside BMP and BI provides a comprehensive approach for selecting suitable bio-waste feedstocks that can be introduced in biogas plants.

Trace metal sorption on nanoplastics: An innovative analytical approach combining surface analysis and mass spectrometry techniques.

The mass and volume concentration of nanoplastics is extremely low, but incredibly high in terms of surface area; this is expected to increase their toxicity through the ab/adsorption and transport of chemical co-pollutants such as trace metals. In this context, we studied the interactions between nanoplastics model materials functionalized with carboxylated groups, with either smooth or raspberry-like surface morphologies, and copper as representative of trace metals. For this purpose, a new methodology, using two complementary surface analysis techniques: Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS) and X-ray Photoelectron Spectroscopy (XPS) was developed. In addition, inductively coupled plasma mass spectrometry (ICP-MS) was used to quantify the total mass of sorbed metal on the nanoplastics. This innovative analytical approach from the top surface to the core of nanoplastics demonstrated not only the interactions with copper at the surface level, but also the ability of nanoplastics to absorb metal at their core. Indeed, after 24 h of exposition, the copper concentration at the nanoplastic surface remained constant due to saturation whereas the copper concentration inside the nanoplastic keeps increasing with the time. The sorption kinetic was evaluated to increase with the density of charge of the nanoplastic and the pH. This study confirmed the ability of nanoplastics to act as metal pollutant carriers by both adsorption and absorption phenomena.

A new analytical approach based on asymmetrical flow field-flow fractionation coupled to ultraviolet spectrometry and light scattering detection for SWCNT aqueous dispersion studies.

This work demonstrates the potential of asymmetrical flow field-flow fractionation (A4F) coupled to Ultraviolet spectrometry (UV) and multi-angle light scattering (MALS) for the study of single-walled carbon nanotube (SWCNT) dispersion in aqueous solutions containing a surfactant. The results indicate that this technique is a powerful analytical tool that is able to evaluate SWCNT dispersion states in aqueous media and, more importantly, determine the presence or absence of aggregates, the numbers and sizes of different SWCNT populations and the SWCNT size distribution. Dynamic light scattering was employed to complete and demonstrate the relevance of the data that were obtained via A4F-UV-MALS. Two different anionic surfactants that are used to disperse SWCNTs were then studied. The dispersing powers of the surfactants were experimentally evaluated based on their structural organizations. This study demonstrates that surfactant concentration and sonication energy are key parameters that control the SWCNT dispersion state and SWCNT structural integrity therein.

Multi-wall carbon nanotube aqueous dispersion monitoring by using A4F-UV-MALS.

In this work, the potentiality of asymmetrical flow field-flow fractionation (A4F) hyphenated to UV detector and multi-angle light scattering (MALS) was investigated for accurately determining multi-walled carbon nanotube (MWCNT) length and its corresponding dispersion state in aqueous medium. Fractionation key parameters were studied to obtain a method robust enough for heterogeneous sample characterization. The main A4F conditions were 10(-5) mL min(-1) NH(4)NO(3), elution flow of 1 mL min(-1), and cross flow of 2 mL min(-1). The recovery was found to be (94 ± 2)%. Online MALS analysis of eluted MWCNT suspension was performed to obtain length distribution. The length measurements were performed with a 4% relative standard deviation, and the length values were shown to be in accordance with expected ones. The capabilities of A4F-UV-MALS to size characterize various MWCNT samples and differentiate them according to their manufacturing process were evaluated by monitoring ball-milled MWCNT and MWCNT dispersions. The corresponding length distributions were found to be over 150-650 and 150-1,156 nm, respectively. A4F-UV-MALS was also used to evaluate MWCNT dispersion state in aqueous medium according to the surfactant concentration and sonication energy involved in the preparation of the dispersions. More especially, the presence or absence of aggregates, number and size of different populations, as well as size distributions were determined. A sodium dodecyl sulfate concentration of 15 to 30 mmol L(-1) and a sonication energy ranged over 20-30 kJ allow obtaining an optimal MWCNT dispersion. It is especially valuable for studying nanomaterials and checking their manufacturing processes, size characterization being always of high importance.

Fate of nanoplastics in the environment: Implication of the cigarette butts.

Fate, transport and accumulation of nanoplastics have attracted considerable attention in the past few years. While actual researches have been focused on nanoplastics dispersed or aggregated in different environmental system, no study have been focused on the possibility that nanoplastics are co-transported with other natural or anthropogenic materials. Therefore, the large quantity of debris released in the environment, such as cigarette butts (CGB), could be part of the nanoplastics fate and behavior. Here we show the considerable sorption capacities of cigarette filters for nanoplastics. To address this topic, we chose polystyrene-based nanoplastics with similar state of charge (according to the physico-chemical characteristic of the zeta potential -45 to -40 mV) but with different sizes (50-800 nm) and morphologies. A kinetic approach to sorption in fresh water (pH = 8.05; 179.5 µS cm-1) at room temperature was carried out by means of the flow field flow analysis method (AF4) to determine the partition coefficients and water sampling rates between nanoplastics and cigarette butts. Using different models of, more or less environmentally relevant, nanoplastics (NPTs) and adequate analytical strategies, we found partition coefficients between the NPTs and CGBs ranged from 102 to 104 in freshwater conditions. We demonstrated that the physical features of the NPTs (size and morphology) have an influence on the sorption behaviour. Asymmetrical shaped NPTs with broader size distribution seems to be mostly retained in the CGBs after longer equilibration time. This result shows the importance of the NPTs features on the mechanisms governing their transfer and fate in the environment through environmental matrices, especially when other materials are involved. We anticipate our work to be a starting point for investigating the co-transport of NPTs with other materials present in the environment (natural and anthropogenic).

Nanoplastics are neither microplastics nor engineered nanoparticles.

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.

Nanoplastic occurrence in a soil amended with plastic debris.

While several studies have investigated the potential impact of nanoplastics, proof of their occurrence in our global environment has not yet been demonstrated. In the present work, by developing an innovative analytical strategy, the presence of nanoplastics in soil was identified for the first time. Our results demonstrate the presence of nanoplastics with a size ranging from 20 to 150 nm and covering three of the most common plastic families: polyethylene, polystyrene and polyvinyl chloride. Given the amount of organic matter in the soil matrix, the discrimination and identification of large nanoplastic aggregates are challenging. However, we provided an innovative methodology to circumvent the organic matter impact on nanoplastic detection by coupling size fractionation to molecular analysis of plastics. While photodegradation has been considered the principal formation pathway of nanoplastics in the environment, this study provides evidence, for the first time, that plastic degradation and nanoplastic production can, however, occur in the soil matrix. Moreover, by providing an innovative and simple extraction/analysis method, this study paves the way to further studies, notably regarding nanoplastic environmental fate and impacts.

Trace element distribution in marine microplastics using laser ablation-ICP-MS.

Due to the dramatic quantity of plastic debris released into our environment, one of the biggest challenges of the next decades is to trace and quantify microplastics (MPs) in our environments, especially to better evaluate their capacity to transport other contaminants such as trace metals. In this study, trace elements (Fe, Cu, Zn, As, Cd, Sn, Sb, Pb, and U) were analyzed in the microplastic subsurface (200 µm) using laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). Microplastics subjected to the marine environment were collected on beaches (Guadeloupe) exposed to the north Atlantic gyre. We established a strategy to discriminate sorbed contaminants from additives based on the metal concentration profiles in MP subsurface using qualitative and quantitative approaches. A spatiotemporal correlation of the sorption pattern was proposed to compare MPs in terms of relative exposure time and time-weighted average concentrations in the exposure media.

Deposition of environmentally relevant nanoplastic models in sand during transport experiments.

Nanoplastics (NPTs) are defined as colloids that originated from the unintentional degradation of plastic debris. To understand the possible risks caused by NPTs, it is crucial to determine how they are transported and where they may finally accumulate. Unfortunately, although most sources of plastic are land-based, risk assessments concerning NPTs in the terrestrial environmental system (soils, aquifers, freshwater sediments, etc.) have been largely lacking compared to studies concerning NPTs in the marine system. Furthermore, an important limitation of environmental fate studies is that the NPT models used are questionable in terms of their environmental representativeness. This study describes the fate of different NPT models in a porous media under unfavorable (repulsive) conditions, according to their physical and chemical properties: average hydrodynamic diameters (200-460 nm), composition (polystyrene with additives or primary polystyrene) and shape (spherical or polymorphic). NPTs that more closely mimic environmental NPTs present an inhomogeneous shape (i.e., deviating from a sphere) and are more deposited in a sand column by an order of magnitude. This deposition was attributed in part to physical retention, as confirmed by the straining that occurred for the larger size fractions. Additionally, different Derjaguin-Landau-Verwey-Overbeek (DLVO) models -the extended DLVO (XDLVO) and a DLVO modified by surface element integration (SEI) method-suggest that the environmentally relevant NPT models may alter its orientation to diminish repulsion from the sand surface and may find enough kinetic energy to deposit in the primary energetic minimum. These results point to the importance of choosing environmentally relevant NPT models.