Fate Of Nanoplastics Research Articles

The selective occurrence of ripening effect makes the cotransport of various sized nanoplastics in seawater-saturated and freshwater-saturated porous media significantly different

We explored the coadsorption and cotransport (single, binary, and ternary systems) of varying sized (50, 200, and 500 nm) Polymethylmethacrylate (PMMA) nanoplastics (NPs) with different concentration ratios in freshwater-saturated and seawater-saturated porous media. It was found that ripening effect occurred selectively, with ripening more likely to occur in seawater relative to freshwater, resulting in significantly different cotransport and coadsorption of varying sized NPs in freshwater-saturated and seawater-saturated porous media. In freshwater, there was no obvious ripening effect happening. In both binary and ternary systems, as the concentration of coexisting PMMA NPs increased, the adsorption and retention of coexisting other sized PMMA NPs were inhibited due to competition for adsorption sites. In seawater, coexisting varying sized NPs promoted adsorption and retention of each other in saturated porous media due to increased roughness and ripening effect. The NP aggregate size and the increase in surface roughness of media grains brought about by the increase in size variety of NPs dominated the cotransport of varying sized NPs in seawater-saturated porous media. The findings of this study provide help for clarifying the fate of NPs presented in real environments in porous media of freshwater and seawater systems.

What if you eat nanoplastics? Simulating nanoplastics fate during gastrointestinal digestion

Despite our growing awareness of micro-and nanoplastics presence in food and beverages, the fate of nanoplastics (NPs) in the human gastrointestinal tract (GIT) remains poorly investigated. Changes of nanoplastics size upon digestive conditions influence the potential of absorption through the intestine. In this study, polymer nanoparticles with different physicochemical properties (size, surface and chemistry) were submitted to gastrointestinal digestion (GID) simulated in vitro. Their agglomeration behaviour was measured with a unique set of analytical approaches, allowing to study NPs’ interactions with the digestive enzymes. Smaller NPs agglomerated more, narrowing the overall particle size distribution of smaller and larger NPs. NPs of different polymers exhibited heteroagglomeration. Digestive enzymes interact with the NPs, forming large but fragile agglomerates. In presence of the enzymes, even acid-functionalized NPs, typically stable in harsh conditions, agglomerated similarly to the non-functionalized PS NPs. These results highlight the role of the GID in increasing the effective size of ingested NPs, potentially reducing their ability to pass through the cell membranes. Our findings address a critical knowledge gap in nanoplastics oral uptake potential, providing a solid technical foundation for their characterization.

Adsorption and uptake of functionalized nanoplastics (NPs) by wetland plant (Sphagnum): A unique pathway for polystyrene-NPs reduction in non-vascular plants

Wetlands are sources and sinks for nanoplastics (NPs), where adsorption and uptake by plants constitute a crucial pathway for NPs accumulation. This study found that Sphagnum exhibited a high potential (~89.75 %) to intercept NPs despite the lack of root systems and stomata. Two pathways for 100nm polystyrene NPs accumulation in Sphagnum were located: (i) Spiral interception and foliar adsorption. Efficient adsorption is credited to the micro/nano-interlocked leaf structure, which is porous, hydrophilic and rough. (ii) Intracellular enrichment through pores. Fluorescence tracking indicates pseudo-leaves (lateral > cephalic branches) as primary organs for internalization. Accumulation of differently functionalized NPs was characterized: PS-Naked-NPs (PS), PS-COOH-NPs (PC) and PS-NH2-NPs (PN) were all largely retained by pathway (i), while pathway (ii) mainly uptake PN and PC. Unlike PS aggregation in transparent cells, PC enrichment in chloroplast cells and PN in intercellular spaces reduced pigment content and fluorescence intensity. Further, the effects of the accumulated NPs on the ecological functions of Sphagnum were evaluated. NPs reduce carbon flux (assimilation rate by 57.78 %, and respiration rate by 33.50%), significantly decreasing biomass (PS = 13.12 %, PC = 26.48 %, PN = 35.23 %). However, toxicity threshold was around 10 μg/mL, environmental levels (≤1 μg/mL) barely affected Sphagnum. This study advances understanding of the behavior and fate of NPs in non-vascular plants, and provides new perspectives for developing Sphagnum substrates for NPs interception.

Generation and Fate of Nanoplastics in the Intestine of Plastic-Degrading Insect (Tenebrio molitor Larvae) during Polystyrene Microplastic Biodegradation.

The insect Tenebrio molitor exhibits ultrafast efficiency in biodegrading polystyrene (PS). However, the generation and fate of nanoplastics (NPs) in the intestine during plastic biodegradation remain unknown. In this study, we investigated the biodegradation of PS microplastics (MPs) mediated by T. molitor larvae over a 4-week period and confirmed biodegradation by analyzing Δδ13C in the PS before and after biotreatment (-28.37‰ versus -24.88‰) as an effective tool. The ·OH radicals, primarily contributed by gut microbiota, and H2O2, primarily produced by the host, both increased after MP digestion. The size distribution of residual MP particles in excrements fluctuated within the micrometer ranges. PS NPs were detected in the intestine but not in the excrements. At the end of Weeks 1, 2, 3, and 4, the concentrations of PS NPs in gut tissues were 3.778, 2.505, 2.087, and 2.853 ng/lava, respectively, while PS NPs in glands were quantified at 0.636, 0.284, and 0.113 ng/lava and eventually fell below the detection limit. The PS NPs in glands remained below the detection limit at the end of Weeks 5 and 6. This indicates that initially, NPs generated in the gut entered glands, then declined gradually and eventually disappeared or possibly biodegraded after Week 4, associated with the elevated plastic-degrading capacities of T. molitor larvae. Our findings unveil rapid synergistic MP biodegradation by the larval host and gut microbiota, as well as the fate of generated NPs, providing new insights into the risks and fate associated with NPs during invertebrate-mediated plastic biodegradation.

Differential cellular uptake and trafficking of nanoplastics in two hemocyte subpopulations of mussels Perna viridis

Nanoplastics (NPs) could be ingested by bivalves and translocated to their hemocytes, which played critical roles in immune-defense. In this study, highly fluorescent aggregation-induced emission nanoplastics (AIE-NPs) of two sizes (50 nm and 200 nm) were utilized to explore the dynamic systems of cellular uptake, intracellular trafficking, and ultimate localization in the granulocyte and agranulocyte subpopulations of hemocytes in the green mussels Perna viridis. We firstly revealed their differential cellular uptake and trafficking of nanoplastics in two hemocyte subpopulation systems. Specifically, agranulocytes performed relatively faster uptake rate for nanoplastics of two sizes, whereas granulocytes had about tenfold higher accumulation capacity. Unexpectedly, there was little removal of nanoplastics in the two subpopulation systems, and such persistence probably could trigger more severe cytotoxicity. Considerable amounts of 200 nm NPs without plasma membrane wrapping were present in the agranulocytes, which may be related to their unique caveolae-mediated uptake pathway. We further demonstrated that the internalized NPs accelerated the differentiation of agranulocytes into granulocytes with higher immunoreactivity, which may be a crucial detoxification mechanism. Our results highlighted the size-driven fate of NPs in different subpopulations of mussel hemocytes, contributing to a more comprehensive understanding of the toxicity of NPs to aquatic organisms.

Effects of nanoplastics on the gut microbiota of Pacific white shrimp Litopenaeus vannamei.

Nanoplastics (NPs) are an abundant, long-lasting, and widespread type of environmental pollution that is of increasing concern because of the serious threats they might pose to ecosystems and species. Identifying the ecological effects of plastic pollution requires understanding the effects of NPs on aquatic organisms. Here, we used the Pacific white shrimp (Litopenaeus vannamei) as a model species to investigate whether ingestion of polystyrene NPs affects gut microbes and leads to metabolic changes in L. vannamei. The abundance of Proteobacteria increased and that of Bacteroidota decreased after NPs treatment. Specifically, Vibrio spp., photobacterium spp., Xanthomarina spp., and Acinetobacter spp. increased in abundance, whereas Sulfitobacter spp. and Pseudoalteromonas spp. decreased. Histological observations showed that L. vannamei exposed to NP displayed a significantly lower intestinal fold height and damaged intestinal structures compared with the control group. Exposure to NPs also stimulated alkaline phosphatase, lysozyme, and acid phosphatase activity, resulting in an immune response in L. vannamei. In addition, the content of triglycerides, total cholesterol, and glucose were significantly altered after NP exposure. These results provided significant ecotoxicological data that can be used to better understand the biological fate and effects of NPs in L. vannamei.

Effects of photochlorination on the physicochemical transformation of polystyrene nanoplastics: Mechanism and environmental fate.

With the increasingly severe plastic pollution, the environmental behavior and effects of nanoplastics (NPs) have attracted much attention. The transformation of NPs in natural and engineered environments (e.g., photooxidation, disinfection) can significantly alter the physicochemical properties and thus affect the fate and toxicity of NPs. However, how solar irradiation with free chlorine, an inevitable process once NPs enter the environment from wastewater treatment plants, affects the physicochemical properties of NPs is still unclear. In this study, the behavior and mechanism of polystyrene (PS) NPs transformation in the solar/chlorine process were evaluated. The results demonstrated that solar irradiation significantly enhanced the physicochemical transformation of PS NPs during chlorination, including chain scission, surface oxidation, and organic release. In addition, two-dimensional correlation spectroscopy analysis using Fourier transform infrared spectroscopy and reactive species quenching experiments showed that chain scission and surface oxidation of PS NPs were primarily caused by direct oxidation of hydroxyl radicals and ozone, while reactive chlorine species played an indirect role. Moreover, photochlorination-induced changes in the properties of PS NPs enhanced the colloidal stability in synthetic wastewater solution and toxicity to Caenorhabditis elegans. These findings reveal an important transformation behavior of nanoplastics in the environment and emphasize the importance of accounting for photochlorination to accurately assess the ecological risk of nanoplastics.

After the sun: a nanoscale comparison of the surface chemical composition of UV and soil weathered plastics

Once emitted into the environment, macro- (MaP), micro- (MP) and nanoplastics (NP) are exposed to environmental weathering. Yet, the effects of biogeochemical weathering factors occurring in the soil environment are unknown. As the transport, fate, and toxicity of MP and NP depend directly on their surface properties, it is crucial to characterize their transformation in soils to better predict their impact and interactions in this environment. Here, we used scanning transmission x-ray micro spectroscopy to characterize depth profiles of the surface alteration of environmental plastic debris retrieved from soil samples. Controlled weathering experiments in soil and with UV radiation were also performed to investigate the individual effect of these weathering factors on polymer surface alteration. The results revealed a weathered surface on a depth varying between 1 µm and 100 nm in PS, PET and PP environmental plastic fragments naturally weathered in soil. Moreover, the initial step of surface fragmentation was observed on a PS fragment, providing an insight on the factors and processes leading to the release of MP and NP in soils. The comparison of environmental, soil incubated (for 1 year) and UV weathered samples showed that the treatments led to different surface chemical modifications. While the environmental samples showed evidence of alteration involving oxidation processes, the UV weathered samples did not reveal oxidation signs at the surface but only decrease in peak intensities (indicating decrease of the number of chemical C bonds). After a one-year incubation of samples in soil no clear aging effects were observed, indicating that the aging of polymers can be slow in soils.

Combined effects of particle size and humic acid corona on the aggregation kinetics of nanoplastics in aquatic environments

Nanoplastics (NPs) contaminant in aquatic environments is one of the pressing environmental concerns globally. However, the combined effects of particle size and humic acid (HA) corona on the aggregation behavior of NPs have not been revealed yet. Therefore, this study explored the influence of HA corona on the aggregation kinetics of NPs with three different particle sizes under various water quality conditions. Results showed that in the absence of HA corona, the aggregation kinetic processes of all the three NPs were affected by the repulsive force originating from the hydration layer. Moreover, the smaller the particle size, the more obvious the effect. HA corona played a steric hindrance role for all the three NPs based on the extended-Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory in monovalent solutions, resulting in the impediment of aggregation. Whereas, in divalent solutions, the HA corona of 100 and 200 nm NPs experienced three stages: deformation, electrostatic-patch and bridging; while that of 40 nm NPs underwent electrostatic-patch and steric hindrance. The larger number of HA molecules distributed on 100 and 200 NPs surfaces led to more interactions with Ca2+ and NPs, which was the key factor for HA corona to play more diverse roles. According to the two dimension correlation spectroscopy analysis (2D-COS), the structural change in the interaction between HA and NPs was that the aromatic ring of NPs took precedence, followed by the carbonyl groups of HA. This study provided new insights into the combined effects of HA corona and particle size on the aggregation kinetics of NPs and established a theoretical foundation for predicting and assessing the transport and fate of NPs.

Influence of natural organic matters on fate of polystyrene nanoplastics in porous media

Natural organic matters (NOMs) are widely present in aqueous environments. The effect of NOMs on the fate of nanoplastics that are gradually receiving widespread attention in porous media needs to be noticed, but relevant research is lacking. To fill this gap, the present study focused on elucidating the influence of NOMs and metal cations with varying concentrations upon the transport, long-term release, and particle fracture of polystyrene nanoplastics (PS-NPs) in saturated porous media. The adsorption, transport, long-term release, and particle fracture tests were conducted. A mathematical model and the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory were used in this research. NOMs could adsorb onto PS-NPs leading to a reduction in the PS-NPs' zeta potential and an increase in the energy barrier and steric hindrance between PS-NPs and quartz sand, ultimately facilitating the transport of PS-NPs through porous media. On the other hand, an increase in concentration and valence of metal ions enhanced the PS-NPs' zeta potential, resulting in PS-NPs' aggregation and increased size when NOMs were present. This reduced the energy barrier between porous media and PS-NPs, resulting in increased blocking and straining, allowing decreased PS-NPs' transport. Long-term release tests demonstrated release ability and mobilities of PS-NPs decreased as the enhanced NOM concentration, addition of metal cations, and decreased valence of metal ions, in agreement with the transport test findings. In the research about particle fracture, NOMs were found to inhibit the fracture of PS-NPs by adsorbing on their surface to protect them from fracture. Metal cations and increased metal cation valence promoted the fracture of released PS-NPs when NOMs were present by promoting NOM aggregation and thus hindering the protection of NOMs for the nanoplastics.

Fragmentation of nano- and microplastics from virgin- and additive-containing polypropylene by accelerated photooxidation

Plastic is ubiquitous in the environment, where it gradually weathers and fragments into nanoplastics (NPs) and microplastics (MPs); however, the weathering process and fragmentation rate are poorly understood. In this study, we quantitatively determined the abundances and size distributions of NPs and MPs produced from virgin polypropylene (PP) and additive-containing PP (PPa) sheets via photooxidation with water in a simulated sunlight chamber followed by vortexing. The fragmentation rate of PP and PPa were approximately 1.1 × 108 particles/cm2 and 1.0 × 108 particles/cm2, respectively, during 176 days of exposure in the chamber (corresponding to 2.7 years of exposure in an outdoor environment in the Republic of Korea). However, quadratic regression analysis of the relationship between total particles produced and exposure duration revealed that the PP fragmentation rate was faster than the PPa fragmentation rate after a sunlight exposure duration equivalent to 2.7 years. Furthermore, the mechanical stress of vortexing after photooxidation played an important role in the production of MPs; it had a smaller role in the production of NPs. The sizes of fragmented particles produced by photooxidation and mechanical stress followed a power law distribution, with a scaling exponent of α = 2.87 ± 0.15, which was similar to a three-dimensional fragmentation pattern. This study provides valuable insights into the weathering and fragmentation processes of plastics. Further studies on the environmental fate and impact of NP and MP production from plastic weathering and fragmentation, as well as the potential influence of plastic additives on these processes.

Interaction of polystyrene nanoplastics with human fibrinogen

Nanoplastics are an emerging environmental contaminant that can penetrate biological barriers to enter the bloodstream and risk human health. In this context, nanoplastics are likely to interact with proteins in the blood to possibly affect protein structure and function and consequently induce biological effects. Here we report that polystyrene (PS), PS-NH2, and PS-COOH nanoplastics disrupt the structure of human fibrinogen (HF) in a dose-dependent manner, as revealed by UV–vis and fluorescence spectroscopy. All three nanoplastics interacted with HF in a similar way, with PS-NH2 having the greatest effect on HF structure. Furthermore, fibrinogen polymerization experiments demonstrated that nanoplastics have the potential to promote blood coagulation, with PS-NH2 again having a stronger effect. Collectively, these results provide insights into the interactions occurring between nanoplastics and HF, the likely transport and fate of nanoplastics in organisms, and their potential pathophysiological consequences.

Toxicity effects of polystyrene nanoplastics and arsenite on Microcystis aeruginosa

Despite the increasing research on the fate of nanoplastics (NPs, <100 nm) in freshwater systems, little is known about the joint toxic effects of metal(loid)s and NPs modified with different functional groups on microalgae. Here, we explored the joint toxic effects of two types of polystyrene NPs [one modified with a sulfonic acid group (PSNPs-SO3H), and one without this functional group (PSNPs)] and arsenic (As) on the microalgae Microcystis aeruginosa. The results highlighted that PSNPs-SO3H showed a smaller hydrodynamic diameter and greater potential to adsorb positively charged ions than PSNPs, contributing to the more severe growth inhibition, while both of them produced oxidative stress. Metabolomics further revealed that the fatty acid metabolism of the microalgae was significantly up-regulated under both NPs exposure, while PSNPs-SO3H down-regulated the tricarboxylic acid cycle (TCA cycle) of the microalgae. As uptake by algae was significantly reduced by 82.58 % and 59.65 % in the presence of 100 mg/L PSNPs and PSNPs-SO3H, respectively. The independent action model showed that the joint toxicity of both NPs with As was assessed as antagonistic. In addition, PSNPs and PSNPs-SO3H had dissimilar effects on the composition of the microalgae extracellular polymeric substances (EPS), resulting in different uptake and adsorption of As, thereby affecting the physiology and biochemistry of algae. Overall, our findings propose that the specific properties of NPs should be considered in future environmental risk assessments.

Limited effects of different real groundwaters from three coastal cities in China on the transport of low-concentration nanoplastics in quartz sand.

Nanoplastics (NPs) have been widely detected in soil-groundwater systems. However, to date, the effect of real groundwater on the fate and transport of NPs has been poorly understood. In this study, the transport and retention behaviors of both polystyrene and poly(lactic-co-glycolic acid) NPs (PS NPs and PLGA NPs) in different real groundwaters from three coastal cities in China were explored using column experiments. PS (0.51 and 1.1 μm) and PLGA (1 μm) NPs with a low concentration of 2 mg L-1 were employed. Close observation showed that the transport of PS NPs was much higher than PLGA NPs in different groundwaters, with an average breakthrough curve plateau (C/Co) of ∼0.81 for PS NPs and ∼0.19 for PLGA NPs, respectively. As observed for PLGA, the plastic shape- and size-induced straining may be the reason for the minimal transport. Interestingly, we found that although the physicochemical characteristics of different real groundwaters varied significantly, the transport of certain NPs in real groundwater was similar with negligible differences. Closer inspection indicated that similar pHs of different groundwaters may be the reason contributing to these findings. Further investigation revealed that the transport behaviors of PS and PLGA NPs in real groundwater did not follow the classical DLVO theory. These findings suggest that the fate and transport of NPs in real soil-groundwater systems are much more comprehensive than the prediction based on DLVO theory and need intensive investigation.

Impact of iron/aluminum (hydr)oxide and clay minerals on heteroaggregation and transport of nanoplastics in aquatic environment

Nanoplastics (NPs) are emerging contaminants in the environment, where the transport and fate of NPs would be greatly affected by interactions between NPs and minerals. In the present study, the interactions of two types of polystyrene nanoplastics (PSNPs), i.e., bare-PSNPs and carboxylated PSNPs–COOH, with iron (hydr)oxides (hematite, goethite, magnetite, and ferrihydrite), aluminum (hydr)oxides (boehmite and gibbsite), and clay minerals (kaolinite, montmorillonite, and illite) were investigated. The positively charged iron/aluminum (hydr)oxide minerals could form heteroaggregates with negatively charged PSNPs. Electrostatic and hydrophobic interaction dominate for the heteroaggregation of bare-PSNPs with iron/aluminum (hydr)oxide minerals, while ligand exchange and electrostatic interaction are involved in the heteroaggregation of PSNPs–COOH with iron/aluminum (hydr)oxides minerals. However, heteroaggregation between PSNPs and negatively charged clay minerals was negligible. Humic acid markedly suppressed such heteroaggregation between PSNPs and minerals due to enhanced electrostatic repulsion, steric hindrance, and competition of surface attachment sites. The heteroaggregation rates of both bare-PSNPs and PSNPs–COOH with hematite decreased with increasing solution pH. Increased ionic strength enhanced the heteroaggregation of PSNPs–COOH but inhibited that of bare-PSNPs. The results of the present study suggested that the heteroaggregation of PSNPs in environments could be strongly affected by minerals, solution pH, humic acid, and ionic strength.

Swelling-Induced Fragmentation and Polymer Leakage of Nanoplastics in Seawater.

Nanoplastics (NPs) have been successively detected in different environmental matrixes and have aroused great concern worldwide. However, the fate of NPs in real environments such as seawater remains unclear, impeding their environmental risk assessment. Herein, multiple techniques were employed to monitor the particle number concentration, size, and morphology evolution of polystyrene NPs in seawater under simulated sunlight over a time course of 29 days. Aggregation was found to be a continuous process that occurred constantly and was markedly promoted by light irradiation. Moreover, the occurrence of NP swelling, fragmentation, and polymer leaching was evidenced by both transmission electron microscopy and scanning electron microscopy techniques. The statistical results of different transformation types suggested that swelling induces fragmentation and polymer leakage and that light irradiation plays a positive but not decisive role in this transformation. The observation of fragmentation and polymer leakage of poly(methyl methacrylate) and poly(vinyl chloride) NPs suggests that these transformation processes are general for NPs of different polymer types. Facilitated by the increase of surface functional groups, the ions in seawater could penetrate into NPs and then stretch the polymer structure, leading to the swelling phenomenon and other transformations.

Combined effects of photoaging and natural organic matter on the colloidal stability of nanoplastics in aquatic environments

The transport and fate of nanoplastics (NPs) in aquatic environments are closely associated with their colloidal stability, which is affected by aging and natural organic matter (NOM) adsorption. This study systematically investigated the combined effects of photoaging and NOM (e.g. humic acids, HA; and a model protein, bovine serum albumin, BSA) on the aggregation kinetics of NPs (polystyrene, PS) in NaCl and CaCl2 solutions. Our results showed that photoaged NPs adsorbed less HA than pristine NPs due to weaker hydrophobic and π-π interactions. In return, HA showed weaker impacts on NPs’ stability after photoaging. Differently, photoaged NPs absorbed more BSA than pristine NPs due to stronger hydrogen bonding and electrostatic attraction. Thus, the inhibitory effects of BSA on the aggregation kinetics of NPs were enhanced after photoaging. Regarding the effects of NOM on the aging of NPs, our results showed that HA competed with NPs for photons and underwent photo-degradation. Subsequently, the destruction/reconstruction of adsorbed HA increased (in NaCl) or decreased (in CaCl2) the stability of NPs. Notably, light radiation-induced flocculation of BSA molecules, which wrapped and integrated NPs and lead to their destabilization. Overall, this study provided new insights into the aggregation behavior of NPs in aquatic systems, which have significant implications for predicting the transport and fate of NPs in complex real-world environments.

Atmospheric micro (nano) plastics: future growing concerns for human health.

Plastics are an integral but largely inconspicuous part of daily human routines. The present review paper uses cross-disciplinary scientific literature to examine and assess the possible effects of nanoplastics (NPs) concerning microplastics (MPs) on human health and summarizes crucial areas for future research. Although research on the nature and consequences of MPs has seen a substantial rise, only limited studies have concentrated on the atmospheric nanosized polymeric particles. However, due to the intrinsic technological complications in separating and computing them, their existence has been difficult to determine correctly. There is a consensus that these are not only existing in the environment but can get directly released or as the outcome of weathering of larger fragments, and it is believed to be that combustion can be the tertiary source of polymeric particles. NPs can have harmful consequences on human health, and their exposure may happen via ingestion, inhalation, or absorption by the skin. The atmospheric fallout of micro (nano) plastics may be responsible for contaminating the environment. Apart from this, different drivers affect the concentration of micro (nano) plastics in every environment compartment like wind, water currents, vectors, soil erosion, run-off, etc. Their high specific surface for the sorption of organic pollutions and toxic heavy metals and possible transfer between organisms at different nutrient levels make the study of NPs an urgent priority. These NPs could potentially cause physical damage by the particles themselves and biological stress by NPs alone or by leaching additives. However, there is minimal understanding of the occurrence, distribution, abundance, and fate of NPs in the environment, partially due to the lack of suitable techniques for separating and identifying NPs from complex environmental matrices.Highlights Micro (nano) plastics generated may reach the soil, water, and atmospheric compartments.Atmospheric currents serve as a way to transport, leading to micro (nano) plastics pollution.Exposure to micro (nano) plastics may happen via ingestion, inhalation, or absorption by the skin.Nanoplastics may be environmentally more harmful than other plastic particles; the focus should be on defining the exact size range.Visual classification of micro (nano) plastics is poor in reliability and may also contribute to microplastics being misidentified.Graphical abstract

Sediment organic carbon dominates the heteroaggregation of suspended sediment and nanoplastics in natural and surfactant-polluted aquatic environments

The aggregation of nanoplastics (NPs) and suspended sediment (SPS) is the key to the transport and environmental fate of NPs. However, the influence of SPS composition and environmental conditions on this process and its mechanisms are still unclear. In this study, the heteroaggregation of NPs and SPS of different compositions is systematically explored under natural and surfactant-polluted aquatic environments (NaCl, humic acid, cetyltrimethylammonium bromide (CTAB)). The results showed that sediment organic carbon (SOC) dominates the aggregation and that different kinds of SOC (comprised of both amorphous organic carbon (AOC) and black carbon (BC)) contribute vary under distinct conditions. In natural freshwater, AOC represents a larger contribution to aggregation because of its weaker electrostatic repulsion compared to that of BC. However, BC represents a larger contribution in natural seawater resulting from decreased electrostatic repulsion and more hydrogen bonding. Conversely, in surfactant-polluted aquatic environments, both AOC and BC have a high contribution owing to the bridge effect plus hydrogen bonding. Notably, minerals’ contribution in aggregates remains low under all conditions. Furthermore, CTAB typically inhibits aggregation except under special conditions. The findings of this study contribute notably to a better understanding of the migration of nanoplastics in complex aquatic environments.

Aqueous aggregation and deposition kinetics of fresh and carboxyl-modified nanoplastics in the presence of divalent heavy metals

The presence of heavy metals alters the colloidal stability and deposition of nanoplastics (NPs) in urban waters. Such processes are important to assess the mobility and fate of NPs and their associated heavy metals. Up to date, few studies have reported the impact of heavy metals on the colloidal behaviors of NPs and the involved mechanisms. In the study, time-resolved dynamic light scattering (DLS) and quartz crystal microbalance with dissipation (QCM-D) methods were used to assess the aggregation and deposition kinetics of polystyrene nanospheres with divalent heavy metals. For comparison, carboxyl-modified polystyrene nanospheres were used. Results reveal that heavy metals destabilized NPs more significantly than calcium ions. Spectroscopy and transmission electron microscopy analysis propose that heavy metals destabilized NPs via inner-sphere coordination with carboxyl groups and cation-π interactions, further leading to the formation of different dimensional aggregates. QCM-D results suggest that the deposition rate, irreversibility, and film compactness of NPs on silica surfaces first increased but further decreased as heavy metal concentration increased. Such deposition behaviors depended on the bridging effects between NPs and silica and aggregation-induced diffusion limitation. In that case, the destabilization and retention ability of heavy metals for NPs were related to their electronegativity and hydration shell thickness. In urban waters, the presence of natural organic matter (NOM) decreased the destabilization and retention ability of heavy metals, whereas heavy metals with environmentally relevant concentrations still enhanced the aggregation and deposition of NPs compared with other environmental cations. This study highlights the impact of heavy metal property on the colloidal behaviors of NPs, thus deepening our understanding of the mobility and fate of NPs associated with heavy metals in urban waters.