Nanoplastics In Aquatic Environment Research Articles

Photoaging-induced variations in heteroaggregation of nanoplastics and suspended sediments in aquatic environments: a case study on nanopolystyrene

Photoaging of nanoplastics (NPs) and heteroaggregate with suspended sediments (SS) determines transport processes and ecological risks of NPs in aquatic environments. This study investigated the disruption of photoaging on the heteroaggregation behavior of polystyrene NPs (PSNPs) and SS in different valence electrolyte solutions and deduced the interaction mechanisms by integrating aggregation kinetics and molecular dynamics (MD) simulation. Increasing the electrolyte concentration significantly enhanced the heteroaggregation between PSNPs and SS, and the divalent electrolytes induced the heteroaggregation more efficiently. MD simulation at the molecular level revealed that PS and SS could spontaneously form clusters, and photoaged PS has a stronger potential to fold into a dense state with SS. Photoaging for 30 d retarded heteroaggregation due to the steric hindrance produced by the leached organic matter in NaCl solutions, and the critical coagulation concentration (CCC) increased by more than 85.44%. Contrarily, photoaging caused more oxygen-containing functional groups produced on the surface of PSNPs through Ca2+ bridging promoting heteroaggregation and thus destabilizing in CaCl2 solutions, the CCC decreased by 23.53% ∼ 35.29%. These findings provide mechanistic insight into the environmental process of NPs and SS and are crucial for a comprehensive understanding of the environmental fate and transport of NPs in aquatic environments.

One-step detection of nanoplastics in aquatic environments using a portable SERS chessboard substrate

Nanoplastics present a significant hazard to both the environment and human health. However, the development of rapid and sensitive analysis techniques for nanoplastics is limited by their small size, lack of specificity, and low concentrations. In this study, a surface-enhanced Raman scattering (SERS) chessboard substrate was introduced as a multi-channel platform for the pre-concentration and detection of nanoplastics, achieved by polydomain aggregating silver nanoparticles (PASN) on a hydrophilic and a punched hydrophobic PVDF combined filter membrane. Through a straightforward suction filtration process, nanoplastics were captured by the PASN gap in a single step for subsequent SERS detection, while excess moisture was promptly eliminated from the filter membrane. The PASN-based SERS chessboard substrate, benefiting from the enhanced electromagnetic (EM) field, effectively discriminated polystyrene (PS) nanoplastics ranging in size from 30 nm to 1000 nm. Furthermore, this substrate demonstrated favorable repeatability (RSD of 8.6 %), high sensitivity with a detection limit of 0.001 mg/mL for 100 nm of PS nanoplastics, and broad linear detection ranges spanning from 0.001 to 0.5 mg/mL (R2 = 0.9916). Additionally, the SERS chessboard substrate enabled quantitative analysis of nanoplastics spiked in tap and lake water samples. Notably, the entire pre-concentration and detection procedure required only 3 μL of sample and could be completed within 1 min. With the accessibility of portable detection instruments and the ability to prepare substrates on demand, the PASN-based SERS chessboard substrate is anticipated to facilitate the establishment of a comprehensive global nanoplastics map.

Heteroaggregation, disaggregation, and migration of nanoplastics with nanosized activated carbon in aquatic environments: Effects of particle property, water chemistry, and hydrodynamic condition

Nanosized activated carbon (NAC) as emerging engineered nanomaterials may interact with nanoplastics prevalent in aquatic environments to affect their fate and transport. This study investigated the effects of particle property (charge and concentration), water chemistry [electrolytes, pH, humic acid (HA), and sodium alginate (SA)], and hydrodynamic condition [wave (i.e., sonication) and turbulence (i.e., stirring)] on the heteroaggregation, disaggregation, and migration of NAC with positively charged amino-modified polystyrene (APS) or negatively charged bare polystyrene (BPS) nanoplastics. The homoaggregation rate of APS was slower than its heteroaggregation rate with NAC, with critical coagulation concentrations (CCC) decreasing at higher NAC concentrations. However, the homoaggregation rate of BPS was intermediate between its heteroaggregation rates under low (10 mg/L) and high (40 mg/L) NAC concentrations. The heteroaggregation rate of APS+NAC enhanced as pH increasing from 3 to 10, whereas the opposite trend was observed for BPS+NAC. In NaCl solution or at CaCl2 concentration below 2.5 mM, HA stabilized APS+NAC and BPS+NAC via steric hindrance more effectively than SA. Above 2.5 mM CaCl2, SA destabilized APS+NAC and BPS+NAC by calcium bridging more strongly than HA. The migration process of heteroaggregates was simulated in nearshore environments. The simulation suggests that without hydrodynamic disturbance, APS+NAC (971 m) may travel farther than BPS+NAC (901 m). Mild wave (30-s sonication) and intense turbulence (1500-rpm stirring) could induce disaggregation of heteroaggregates, thus potentially extending the migration distances of APS+NAC and BPS+NAC to 1611 and 2160 m, respectively. Conversely, intense wave (20-min sonication) and mild turbulence (150-rpm stirring) may further promote aggregation of heteroaggregates, shortening the migration distances of APS+NAC and BPS+NAC to 262 and 552 m, respectively. Particle interactions mainly involved van der Waals attraction, electrostatic repulsion, steric hindrance, calcium bridging, π-π interactions, hydrogen bonding, and hydrophobic interactions. These findings highlight the important influence of NAC on the fate, transport, and risks of nanoplastics in aquatic environments.

Rapid, sensitive, and non-destructive on-site quantitative detection of nanoplastics in aquatic environments using laser-backscattered fiber-embedded optofluidic chip

A definitive link between the micro- and nano-plastics (NPLs) and human health has been firmly established, emphasizing the higher risks posed by NPLs. The urgent need for a rapid, non-destructive, and reliable method to quantify NPLs remains unmet with current detection techniques. To address this gap, a novel laser-backscattered fiber-embedded optofluidic chip (LFOC) was constructed for the rapid, sensitive, and non-destructive on-site quantitation of NPLs based on 180º laser-backscattered mechanism. Our theoretical and experimental findings reveal that the 180º laser-backscattered intensities of NPLs were directly proportional to their mass and particle number concentration. Using the LFOC, we have successfully detected polystyrene (PS) NPLSs of varying sizes, with a minimum detection limit of 0.23 μg/mL (equivalent to 5.23 ×107 particles/mL). Moreover, PS NPLs of different sizes can be readily differentiated through a simple membrane-filtering method. The LFOC also demonstrates high sensitivity in detecting other NPLs, such as polyethylene, polyethylene terephthalate, polypropylene, and polymethylmethacrylate. To validate its practical application, the LFOC was used to detect PS NPLs in various aquatic environments, exhibiting excellent accuracy, reproducibility, and reliability. The LFOC provides a simple, versatile, and efficient tool for direct, on-site, quantitative detection of NPLs in aquatic environments.

Smart and accurate detection of nanoplastics in aquatic environments by photoelectrochemical-electrochemical dual-mode portable sensor

The harmful effects of nanoplastics (NPs) on both human health and the ecosystem have gained global attention. This study develops a photoelectrochemical-electrochemical (PEC-EC) dual-mode portable sensor based on CdS/CeO2 heterojunction for the rapid detection of polystyrene nanoplastics (PS NPs) in aquatic environments. The interaction and aggregation between protein and PS NPs, facilitated by hydrophobic properties, influence electron transfer, thereby enabling the detection of PS NPs. Integration of the sensor with a portable EC workstation controlled by a smartphone streamlines the detection process, yielding rapid and clear results, and enhancing convenience for detection. The sensor exhibits the advantages of high sensitivity, good repeatability, and exceptional portability. A wide detection linear range of 0.5–800 μg/mL accompanied by the detection limit of 0.38 ng/mL can be achieved. The relative standard deviation of the sensor for the inter-day (intra-day) precision are determined ranging from 0.4 % to 2.97 % (0.94 % to 4.65 %) in real water samples. Furthermore, the sensor features a self-checking function, establishing it as a dual-mode system that introduces a novel approach for smart detection of PS NPs, with substantial potential for assessing PS NPs pollution in aquatic environments.

Influence of macromolecules and electrolytes on heteroaggregation kinetics of polystyrene nanoplastics and goethite nanoparticles in aquatic environments

Fate and transport of nanoplastics in aquatic environments are affected by their heteroaggregation with minerals in the presence of macromolecules. This study investigated the heteroaggregation of polystyrene nanoplastics (PSNPs) with goethite nanoparticles (GNPs) under the influence of macromolecules [humic acid (HA), bovine serum albumin (BSA), and DNA] and electrolytes. Under 1 mg C/L macromolecule, raising electrolyte concentration promoted heteroaggregation via charge screening, except that calcium bridging with HA also enhanced heteroaggregation at CaCl2 concentration above 5 mM. At all NaCl concentrations and CaCl2 concentration below 5 mM, 1 mg C/L macromolecules strongly retarded heteroaggregation, ranking BSA > DNA > HA. Raising macromolecule concentration strengthened such stabilization effect of all macromolecules in NaCl solution and that of DNA and BSA in CaCl2 solution by enhancing steric hindrance. However, 0.1 mg C/L BSA slightly promoted heteroaggregation in CaCl2 solution due to stronger electrostatic attraction than steric hindrance. In CaCl2 solution, raising HA concentration strengthened its destabilization effect via calcium bridging. Macromolecules having more compact globular structure and higher molecular weight may exert greater steric hindrance to inhibit heteroaggregation more effectively. This study provides new insights on the effects of macromolecules and electrolytes on heteroaggregation between nanoplastics and iron minerals in aquatic environments.

Electrolyte-Gated Carbon Nanotube Field-Effect Transistor-Based Sensors for Nanoplastics Detection in Seawater: A Study of the Interaction between Nanoplastics and Carbon Nanotubes.

Plastics accumulating in the environment are nowadays of great concern for aquatic systems and for the living organisms populating them. In this context, nanoplastics (NPs) are considered the major and most dangerous contaminants because of their small size and active surface, which allow them to interact with a variety of other molecules. Current methods used for the detection of NPs rely on bulky and expensive techniques such as spectroscopy. Here we propose, for the first time, a novel, fast, and easy-to-use sensor based on an electrolyte-gated field-effect transistor (EG-FET) with a carbon nanotube (CNT) semiconductor (EG-CNTFET) for the detection of NPs in aquatic environments, using polystyrene NPs (PS-NPs) as a model material. In particular, as a working mechanism for the EG-CNTFETs we exploited the ability of CNTs and PS to form noncovalent interactions. Indeed, in our EG-CNTFET devices, the interaction between NPs and CNTs caused a change in the electric double layers. A linear increase in the corrected on current (*ION) of the EG-CNTFETs, with a sensitivity of 9.68 μA/(1 mg/mL) and a linear range of detection from 0.025 to 0.25 mg/mL were observed. A π-π interaction was hypothesized to take place between the two materials, as indicated by an X-ray photoelectron spectroscopy analysis. Using artificial seawater as an electrolyte, to mimic a real-case scenario, a linear increase in *ION was also observed, with a sensitivity of 6.19 μA/(1 mg/mL), proving the possibility to use the developed sensor in more complex solutions, as well as in low concentrations. This study offers a starting point for future exploitation of electrochemical sensors for NP detection and identification.

Heteroaggregation kinetics of oppositely charged nanoplastics in aquatic environments: Effects of particle ratio, solution chemistry, and interaction sequence

Interactions between positively charged amino-modified (APS) and negatively charged bare (BPS) polystyrene nanoplastics may cause heteroaggregation in aquatic environments. This study investigated the effects of particle concentration ratio, solution chemistry [electrolytes, pH, and natural organic matter (NOM)], and interaction sequence on their heteroaggregation kinetics. In the absence of electrolytes and NOM, the APS/BPS ratio for attaining maximum heteroaggregation rate (khetero) increased from APS/BPS= 3/7 to APS/BPS= 1/1 as pH increased from 4 to 10, indicating that electrostatic interactions dominated heteroaggregation. In the absence of NOM, khetero ranked APS/BPS= 2/3 > APS/BPS= 1/1 > APS/BPS= 3/2. Colloidal stability decreased linearly as pH increased from 4 to 8 at APS/BPS= 1/1, while diffusion-limited heteroaggregation persisted at pH 10. In NaCl solution, humic acid (HA) retarded heteroaggregation more effectively than sodium alginate (SA) via steric hindrance and weakening electrostatic interactions, following the modified Derjaguin-Landau-Verwey-Overbeek (MDLVO) theory. Compared with simultaneous interactions among APS, BPS, NaCl, and NOM, the NOM retardation effects on heteroaggregation weakened if delaying its interaction with others. In CaCl2 solution, the effects of NOM on heteroaggregation depended on counterbalance among charge screening, steric hindrance, and calcium bridging. These findings highlight the important role of heteroaggregation between oppositely charged nanoplastics on their fate and transport in aquatic environments.

The suspension stability of nanoplastics in aquatic environments revealed using meta-analysis and machine learning

Nanoplastics (NPs) aggregation determines their bioavailability and risks in natural aquatic environments, which is driven by multiple environmental and polymer factors. The back propagation artificial neural network (BP-ANN) model in machine learning (R2 = 0.814) can fit the complex NPs aggregation, and the feature importance was in the order of surface charge of NPs > dissolved organic matter (DOM) > functional group of NPs > ionic strength and pH > concentration of NPs. Meta-analysis results specified low surface charge (0 ≤ |ζ| < 10 mV) of NPs, low concentration (< 1 mg/L) and low molecular weight (< 10 kg/mol) of DOM, NPs with amino groups, high ionic strength (IS > 700 mM) and acidic solution, and high concentration (≥ 20 mg/L) of NPs with smaller size (< 100 nm) contribute to NPs aggregation, which is consistent with the prediction in machine learning. Feature interaction synergistically (e.g., DOM and pH) or antagonistically (e.g., DOM and cation potential) changed NPs aggregation. Therefore, NPs were predicted to aggregate in the dry period and estuary of Poyang Lake. Research on aggregation of NPs with different particle size,shapes, and functional groups, heteroaggregation of NPs with coexisting particles and aging effects should be strengthened in the future. This study supports better assessments of the NPs fate and risks in environments.

Both nanoplastic and iron mineral types determine their heteroaggregation: Aggregation kinetics and interface process

Nanoplastics (NPs) inevitably interact with iron minerals (IMs) after being released into aquatic environments, changing their transport and fate. In this study, batch heteroaggregation kinetics of four types of NPs, i.e., polymethyl methacrylate (PMMA), polystyrene (PS-Bare), amino-polystyrene (PS-NH2), and carboxyl-polystyrene (PS-COOH), with two different IMs (hematite and magnetite) were conducted. We found that the heteroaggregation of NPs and IMs and the associated interfacial interaction mechanisms are both NPs-dependent and IMs-dependent. Specifically, the NPs had stronger heteroaggregation with hematite than magnetite; the heteroaggregation order of two IMs with NPs was PMMA > PS-NH2 > PS-Bare > PS-COOH. Moreover, hydrogen bond, complexation, hydrophobic, cation-π, and electrostatic interaction were involved in the interfacial reaction between NPs and hematite, and electrons were transferred from the NPs to the hematite, causing the reduction of Fe3+ into Fe2+. Furthermore, we first revealed that both pre-homoaggregation of NPs and IMs could affect their subsequent heteroaggregation, and the homoaggregates of IMs could be interrupted by PMMA or PS-COOH NPs introduction. Therefore, the emerging NPs pollution is likely to generate an ecological effect in terms of elemental cycles such as iron cycle. This work provides new insights into assessing the environmental transfer and ecological effects of NPs in aquatic environments.

Quantitative detecting low concentration polystyrene nanoplastics in aquatic environments via an Ag/Nb2CTx (MXene) SERS substrate

In this study, the plasmonic Ag nanoparticles (Ag NPs) were uniformly anchored on the high conductivity Nb2CTx (MXene) nanosheets to construct an Ag/Nb2CTx substrate for surface-enhanced Raman spectroscopy (SERS) detection of polystyrene (PS) nanoplastics. The KI addition (0.15 mol/L), the volume ratio between substrate colloid and nanoplastic suspension (2:1), and the mass ratio of Nb2CTx in substrate (14%) on SERS performance were optimized. The EM hot spots of Ag/Nb2CTx are significantly enlarged and enhanced, elucidated by FDFD simulation. Then, the linear relationship between the PS nanoplastics concentration with three different sizes (50, 300, and 500 nm) and the SERS intensity was obtained (R2 > 0.976), wherein, the detection limit was as low as 10−4 mg/mL for PS nanoplastic. Owing to the fingerprint feature, the Ag/Nb2CTx-14% substrate successfully discerns the mixtures from two-component nanoplastics. Meanwhile, it exhibits excellent stability of PS nanoplastics on different detection sites. The recovery rates of PS nanoplastics with different sizes in lake water ranged from 94.74% to 107.29%, with the relative standard deviation (RSD) ranging from 2.88% to 8.30%. Based on this method, the expanded polystyrene (EPS) decomposition behavior was evaluated, and the PS concentrations in four water environments were analyzed. This work will pave the way for the accurate quantitative detection of low concentration of nanoplastics in aquatic environments.

Behavioral Studies of Zebrafish Reveal a New Perspective on the Reproductive Toxicity of Micro- and Nanoplastics.

The escalating prevalence of microplastics and nanoplastics in aquatic environments is a major challenge affecting the behavior and reproductive health of aquatic organisms while posing potential risks to human health and ecosystems. This review focuses on the neurobehavioral changes and reproductive toxicity of MNPs in zebrafish and their relationships. At the same time, the neurobehavioral changes caused by MNPs were studied, and the synergistic effects of the interaction of these pollutants with other environmental contaminants were explored. In addition, zebrafish, as a model organism, provide valuable insights into the subtle but important effects of MNPs on reproductive behavior, which is critical for understanding reproductive success, suggesting that behavioral changes can serve as an early biomarker of reproductive toxicity. In addition, based on classical endocrine disruptor models and behavioral research methods, the current status of the research on the reproductive toxicity of MNPs in zebrafish was reviewed, which further indicated that the behavioral parameters of zebrafish can be used as an effective and rapid tool to evaluate the reproductive toxicity of MNPs. However, behavioral methods for rapidly assessing the toxicity of MNPs are still an area of exploration. To address limitations and challenges in the current scope of research, this review outlines future research directions with the aim of improving our understanding of the environmental and health impacts of MNPs. This work aims to inform targeted environmental policies and advance public health strategies to address the growing challenge of MNPs pollution.

Differential Photoaging Effects on Colored Nanoplastics in Aquatic Environments: Physicochemical Properties and Aggregation Kinetics.

Nanoplastics (NPs) have different colors, which could affect their photoaging processes in aquatic environments. This study investigated the effects of irradiation on physicochemical properties and aggregation kinetics of five colored NPs. Photodegradation rates and photooxidation degrees ranked white ≈ yellow > red > blue ≈ black NPs, indicating that NPs with longer color wavelengths photoaged faster. The discoloration process followed color fading (2-14 days, except for white NPs), yellowing (10-16 days), yellow fading (18 days), and turning transparent (20-22 days). White NPs exhibited a different photoaging sequence (C-H → C-OH → C═O → O-C═O) from others. Photodegradation was mainly controlled by singlet oxygen, producing 13 chemicals that were mostly organic acids. The overall colloidal stability of pristine NPs ranked blue > yellow > red > black > white. Irradiation for 16 days retarded aggregation of white and other NPs in NaCl solution, raising the critical coagulation concentration (CCC) by 82.14 and 0.85-7.90%, respectively. Contrarily, irradiation promoted aggregation in CaCl2 solution by reducing the CCC of white (67.37%) and other (33.33-37.58%) NPs. The findings demonstrate that colored NPs underwent photoaging processes different from white/transparent NPs, which were focused by previous work, highlighting the important role of color in their environmental fate and transport.

Body distribution and ecotoxicological effect of nanoplastics in freshwater fish, Zacco platypus

The increased consumption of plastics worldwide, has led to the emergence of nanoplastics as important environmental pollutants. Despite the presence of nanoplastics in aquatic environments, their effects on ecosystems remain largely unexplored due to the analysis complexity. This study investigated the organ accumulation and toxic effects of 50 nm polystyrene nanoplastics (PS-NPs) in Zacco platypus (Z. platypus; also known as pale chub fish) using pyrolyzer-gas chromatography-mass spectrometry (Pyr-GC/MS). PS-NPs accumulated in Z. platypus’ brain, digestive tract, branchia, and liver, causing changes at cellular level. Over a 14-day exposure, the accumulated PS-NPs led to observable changes in fish behavior (e.g., Total traveled distance and maximum velocity). In addition, the oxidative stress in each organ of Z. platypus increased as the exposure concentration of PS-NPs increased. This study shows that accumulation of nanoplastics in fish, resulting in behavioral changes and biochemical toxicity. As the pattern of change magnifies with exposure time and concentration, from a long-term perspective, the influence of nanoplastics on aquatic ecosystems become evident. This underscores the urgency for continuous research into the potential risks of nanoplastics in aquatic ecosystems.

Deposition behaviors of carboxyl-modified polystyrene nanoplastics with goethite in aquatic environment: Effects of solution chemistry and organic macromolecules

The ubiquitous nanoplastics (NPs) in the environment are emerging contaminants due to their risks to human health and ecosystems. The interaction between NPs and minerals determines the environmental and ecological risks of NPs. In this study, the deposition behaviors of carboxyl modified polystyrene nanoplastics (COOH-PSNPs) with goethite (α-FeOOH) were systematically investigated under various solution chemistry and organic macromolecules (OMs) conditions (i.e., pH, ionic type, humic acid (HA), sodium alginate (SA), and bovine serum albumin (BSA)). The study found that electrostatic interactions dominated the interaction between COOH-PSNPs and goethite. The deposition rates of COOH-PSNPs decreased with an increase in solution pH, due to the enhanced electrostatic repulsion by higher pH. Introducing cations or anions could compress the electrostatic double layers and compete for interaction sites on COOH-PSNPs and goethite, thereby reducing the deposition rates of COOH-PSNPs. The stabilization effects, which were positive with ions valence, followed the orders of NaCl ≈ KCl < CaCl2, NaNO3 ≈ NaCl < Na2SO4 < Na3PO4. Specific adsorption of SO42− or H2PO4− caused a potential reversal of goethite from positive to negative, leading to the electrostatic forces between COOH-PSNPs and goethite changed from attraction to repulsion, and thus significantly decreasing deposition of COOH-PSNPs. Organic macromolecules could markedly inhibit the deposition of COOH-PSNPs with goethite because of enhanced electrostatic repulsion, steric hindrance, and competition of surface binding sites. The ability for inhibiting the deposition of COOH-PSNPs followed the sequence of SA > HA > BSA, which was related to their structure (SA: linear, semi-flexible, HA: globular, semi-rigid, BSA: globular, with protein tertiary structure) and surface charge density (SA > HA > BSA). The results of this study highlight the complexity of the interactions between NPs and minerals under different environments and provide valuable insights in understanding transport mechanisms and environmental fate of nanoplastics in aquatic environments.

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.

Cation-π mechanism promotes the adsorption of humic acid on polystyrene nanoplastics to differently affect their aggregation: Evidence from experimental characterization and DFT calculation

Multiple water-chemistry factors determine nanoplastics aggregation and thus change their bioavailability and ecological risks in natural aquatic environments. However, the dominant factors and their interactive mechanisms remain elusive. In this study, polystyrene nanoplastics (PSNPs) showed greater colloidal stability in Li Lake water compared to ultrapure water. The RDA and PARAFAC results suggested that dissolved organic carbon, humic acid (HA) in particular, Ca2+, and pH are critical factors influencing PSNPs aggregation. Batch experiments showed that the critical coagulation concentration (CCC) of PSNPs was increased with pH increase; HA increased the CCC of PSNPs in NaCl by 2.6-fold but decreased that in CaCl2 by 1.8-fold. Moreover, cations increased the adsorption of HA on PSNPs. The DFT results suggested that HA-cations complexes (EAE = −1.10 eV and −0.51 eV for HA-Ca2+ and HA-Na+, respectively) but not HA alone (EAE = −0.33 eV) are the main scenarios for their adsorption on PSNPs, and a cation-π mechanism between PSNPs and HA-cations complexes dominates PSNPs aggregation in this scenario. The findings are significant for better understanding the environmental process and fate of nanoplastics in aquatic environments. Environmental implicationNanoplastics are kinds of emerging contaminants. Nanoplastic aggregation determines their bioavailability and toxic risks to ecological health. Herein, the hydrodynamic sizes of PSNPs in local Li Lake water was tested and a redundancy analysis was performed to examine the key water-chemistry factors driving PSNPs aggregation. Moreover, the mechanisms in PSNPs aggregation driven by multiple dominant water-chemistry factors including cations, pH, and DOC were firstly unveiled by combining experimental characterization and theoretical computations. This work improves our understanding of the environmental fate of nanoplastics and provides a theoretical basis for the risk assessment and control of nanoplastics in real aquatic environments.

Incomplete recovery of gut microbiota in marine medaka (Oryzias melastigma) during the depuration phase, after exposure to sulfamethazine/nanoplastics

The persistence of antibiotics and nanoplastics in aquatic environment poses a great threat to aquatic organisms. In our previous study, significant decreases of bacterial richness and changes of bacterial communities in the Oryzias melastigma gut after sulfamethazine (SMZ) and polystyrene nanoplastics (PS) exposure were observed. Here, the O. melastigma dietary exposed to SMZ (0.5 mg/g, LSMZ; 5 mg/g, HSMZ), PS (5 mg/g, PS) or PS + HSMZ were depurated for 21 days to assess the extent of which these effects were reversible. Our results revealed that most diversity indexes of bacterial microbiota in the O. melastigma gut from the treatment groups were insignificantly different from the control, suggesting a large recovery of bacterial richness. Although the sequence abundances of a few genera remained significantly changed, the proportion of dominant genus was recovered. Exposure to SMZ affected the complexity of the bacterial networks, and the cooperation and exchange events of positively associated bacteria were enhanced during this period. After depuration, increases in the complexity of networks and intense competitions among bacteria were observed, which was beneficial for the robustness of networks. However, the gut bacterial microbiota was less stable, and several functional pathways were dysregulated, relative to the control. In addition, higher occurrence of pathogenic bacteria was found in the PS + HSMZ group relative to the signal pollutant group after depuration, indicating a greater hazard for the mixture of PS and SMZ. Taken together, this study contributes to a better understanding of the recovery of bacterial microbiota in fish gut after individual and combined exposure to nanoplastics and antibiotics.

Aggregation kinetics and stability of biodegradable nanoplastics in aquatic environments: Effects of UV-weathering and proteins

Plastic pollution caused by conventional plastics has promoted the development and use of biodegradable plastics. However, biodegradable plastics do not degrade readily in water; instead, they can generate micro- and nanoplastics. Compared to microplastics, nanoplastics are more likely to cause negative impacts to the aquatic environment due to their smaller size. The impacts of biodegradable nanoplastics highly depend on their aggregation behavior and colloidal stability, which still remain unknown. Here, we studied the aggregation kinetics of biodegradable nanoplastics made of polybutylene adipate co-terephthalate (PBAT) in NaCl and CaCl2 solutions as well as in natural waters before and after weathering. We further studied the effect of proteins on aggregation kinetics with both negative-charged bovine serum albumin (BSA) and positive-charged lysozyme (LSZ). For pristine PBAT nanoplastics (before weathering), Ca2＋ destabilized nanoplastic suspensions more aggressively than Na+, with the critical coagulation concentration being 20 mM in CaCl2 vs 325 mM in NaCl. Both BSA and LSZ promoted the aggregation of pristine PBAT nanoplastics, and LSZ showed a more pronounced effect. However, no aggregation was observed for weathered PBAT nanoplastics under most experimental conditions. Further stability tests demonstrated that pristine PBAT nanoplastics aggregated substantially in seawater, but not in freshwater, and only slightly in soil pore water; while weathered PBAT nanoplastics remained stable in all natural waters. These results suggest that biodegradable nanoplastics, especially weathered biodegradable nanoplastics, are highly stable in the aquatic environment, even in the marine environment.

Nanoplastika u vodenoj sredini - poreklo, separacija i karakterizacija - pregled

Scientists discovered plastic in the early 1900s, but didn't realize the detrimental effects its fragmentation could have on the environment 100 years later. In particular, nanoplastics (NPs) particles ranging in size from 1 to 100 nm can cause major problems in the living world due to their high specific surface area for the adsorption other polluting substances from water, and their further bioaccumulation through the food chain. There is no distinctive method to identify, characterize, and quantify nanoplastics in aquatic environments. Although many of the methods developed to study microplastics are not directly applicable to nanoplastics, conventional methods of characterizing nanoplastics are usually tedious because they study individual nanoparticles in isolation. Since nanoplastics resulting from the decomposition of microplastics have different properties than engineering plastic nanoparticles, new techniques need to be developed to help us better understand the seriousness of the nanoplastic problem. Nanoplastic can be isolated from the water environment by a combination of filters and ultracentrifugation. A recent publications states that combining microscopy and spectroscopy, supported by chemometric techniques, will alow a better understand he behavior of nanoplastic particles in the environment and organisms. High hopes are placed on microscopies combined with neural networks for the quantification and characterization of nanoplastics in complex systems. This article describes the degradation pathways of plastics and the formation of nanoplastics in aquatic environments, and possible methods for separation and characterization of nanoplastics in relation to recent publications.