Arsenic adsorption by carboxylate and amino modified polystyrene micro- and nanoplastics: kinetics and mechanisms

Toxic effects of co-exposure to polystyrene nanoplastics and arsenic in zebrafish (Danio rerio): Oxidative stress, physiological and biochemical responses

The issue of nanoplastics (NPs) in the aquatic environment has recently received considerable attention. Arsenic (As) is a relatively abundant and toxic metalloid element in aquatic environments. However, the potential toxic effects of As on aquatic organisms under the influence of NPs remain uncertain. In this study, zebrafish were divided into five different groups: a control group, a single As(V) (10 μg/L) treatment group and three As (10 μg/L) + polystyrene nanoplastics (PS-NPs) treatment groups (NPs at concentrations of 1, 5 and 10 mg/L, respectively) for a period of seven days using a semi-static method. The findings demonstrated that the presence of PS-NPs facilitated the accumulation of As in zebrafish liver, gill and intestine with the following promoting efficiency: liver > gill > intestine. The presence of PS-NPs enhanced the oxidative stress effects of As on the aforementioned tissues. Furthermore, the activities of glutathione-S-transferase and glutathione peroxidase in the liver and intestine were found to be instrumental in mitigating oxidative stress during co-exposure. Furthermore, the presence of PS-NPs led to a further reduction in As-induced acetylcholinesterase activity in the liver and intestine of zebrafish. The combined exposure of zebrafish to PS-NPs and As resulted in an increase in lactate dehydrogenase activity in the liver, intestine and gills. This subsequently led to a reduction in the activity of acid phosphatase and alkaline phosphatase in the aforementioned tissues, thus affecting immune dysfunction in zebrafish. The integrated biomarker response indexes indicate that combined exposures result in greater toxic effects compared to single As exposures. The findings provide a fundamental basis for the assessment of the toxic effects of combined nanoscale plastic and As pollution on aquatic organisms.

Interface adsorption characteristics of microplastics on multiple morphological arsenic compounds

Polystyrene (PS) and polyethylene terephthalate (PET) are commonly used materials that degrade into microplastics in the environment. These microplastics, possessing unique physical properties, can adsorb pollutants and contribute to composite pollution effects. This study examined the loading characteristics and toxic effects of PS and PET on six arsenic compounds, revealing that PS and PET displayed different adsorption capacities for these compounds, with PS demonstrating high adsorption for monomethylarsonic acid (MMA). The adsorption kinetics and isotherm analyses indicated that arsenic compounds quickly reached equilibrium on PS and PET. The kinetics were effectively described by pseudo-first-order models, and the isotherms aligned with the Langmuir and Freundlich models. Furthermore, simulated gastric fluid (SGF) and simulated intestinal fluid (SIF) were used to desorb arsenic compounds bound to PS and PET. The effects of aging, pH, salinity, anions, and humic acid (HA) on the ability of inorganic arsenic (iAs) to bind to PS and PET were analyzed. The results indicated that aging and HA increased the adsorption capacity of the microplastics, while salinity, anions, and elevated pH negatively affected this capacity. Additionally, the influence of microplastics and iAs on the clearance of free radicals by reduced glutathione (GSH) was explored. Microplastics inhibited the clearance of 1,1-diphenyl-2-picryl-hydrazyl (DPPH) by GSH, whereas iAs, especially arsenate, facilitated this process, likely due to synergistic effects with the oxidized form of GSH generated through GSH reactions. This study offers a theoretical foundation for understanding how microplastics transport various forms of arsenic compounds and their potential environmental risks.

Microplastics in groundwater: Environmental fate and possible interactions with coexisting contaminants

Microplastics (MPs) are emerging environmental pollutants which represent a serious threat to ecosystems and human health and have received significant attention from the global community. Currently, a growing number of studies have found the presence of MPs in groundwater. This study exhaustively reviewed varying degrees of recent publications in Web of Science database and investigated the characteristics of MPs (concentration, types, sizes and shapes) in groundwater ecosystems, their migration characteristics, and interactions with co-occurring contaminants. Results suggested that current global research on MPs in groundwater has primarily focused on countries such as India, South Korea, China, Italy and United States. Pollution levels of MPs in groundwater show significant variability, ranging from 0 to 6832 n/L. The predominant plastic polymer types include PP, PE, PS, PA, PET and PVC. The sources of MPs in groundwater are primarily classified as associated with natural processes and anthropogenic activities. The physical, chemical and biological properties can influence the migration of MPs into groundwater. Furthermore, MPs can act as carriers, interacting with co-occurring contaminants, thereby enhancing their migration and toxicity, potentially posing a threat to groundwater ecosystems and human health. Consequently, the major challenges and associated recommendations for forthcoming research on MPs in groundwater are proposed.

An integrated multimethod approach for size-specific assessment of potentially toxic element adsorption onto micro- and nanoplastics: implications for environmental risk

Micro- and nanoscale plastics (MnPs), arising from the environmental degradation of plastic waste, pose significant environmental and health risks as carriers for potentially toxic element (PTE) metals. This study employs asymmetrical flow field-flow fractionation (AF4) coupled with multi-angle light scattering (MALS) and inductively coupled plasma mass spectrometry (ICP-MS) to provide a size-resolved assessment of chromium (Cr), arsenic (As), and selenium (Se) adsorption onto carboxylated polystyrene nanoparticles (COOH-PSNPs) of 100 nm, 500 nm, and 1000 nm. Cr exhibited the highest adsorption, with adsorption per particle surface area increasing from 9.45 × 10-15 μg nm-2 for 100 nm particles to 6.87 × 10-14 μg nm-2 for 1000 nm particles, driven by chemisorptive interactions with carboxyl groups. In contrast, As and Se exhibited slower adsorption rates and significantly weaker interactions, attributed to outer-sphere complexation and electrostatic repulsion. Smaller particles exhibited enhanced adsorption efficiency per unit mass due to their larger surface area-to-volume ratios and higher carboxyl group density (18.5 μEq g-1 for 100 nm compared to 7.9 μEq g-1 for 1000 nm particles). Se adsorption remained negligible across all sizes, near detection limits, highlighting its low affinity for carboxylated surfaces. Our study demonstrates the superior resolution of AF4-MALS-ICP-MS compared to that of bulk ICP-MS, which lacks the ability to discern particle-specific adsorption trends. Unlike bulk ICP-MS, which provides average adsorption values, AF4-MALS-ICP-MS reveals the size-dependent mechanisms influencing metal binding, offering critical insights into the role of MnPs as PTE vectors. The findings highlight the environmental implications of MnPs in facilitating PTE transport and highlights the need for size-specific mitigation strategies. This work sets a foundation for developing more precise risk assessment frameworks and advanced remediation approaches for MnP-contaminated environments.

The Combined Toxic Effects of Polystyrene Microplastics and Arsenate on Lettuce Under Hydroponic Conditions

The combined pollution of microplastics (MPs) and arsenic (As) has gradually been recognized as a global environmental problem, which calls for detailed investigation of the synergistic toxic effects of MPs and As on plants and their mechanisms. Therefore, the interaction between polystyrene microplastics (PS-MPs) and arsenate (AsO43-) (in the following text, it is abbreviated as As(V)) and its toxic effects on lettuce were investigated in this study. Firstly, chemisorption was identified as the main mechanism between PS-MPs and As(V) by the analysis of adsorption kinetics, adsorption thermodynamics, and Fourier transform infrared spectroscopy (FTIR). At the same time, the addition of As(V) promoted the penetration of PS-MPs through the continuous endodermal region of the Casparis strip. Furthermore, compared with the CK group, it was found that the co-addition of As(V) exacerbated the lowering effect of PS-MPs on the pH value of the rhizosphere environment and the inhibitory effect on root growth. In the P20V10 group, the pH decreased by 33.0%. Compared to the CK group, P20, P20V1, and P20V10 decreased the chlorophyll content by 68.45% (16 SPAD units), 71.37% (17.73 SPAD units), and 61.74% (15.36 SPAD units) and the root length by 19.31% (4.18 cm), 50.72% (10.98 cm), and 47.90% (10.37 cm) in lettuce. P5V10 and P20V10 increased CAT content by 153.54% (33.22 U·(mgprol)-1) and 182.68% ((38.2 U·(mgprol)-1)), Ca by 31.27% and 37.68%, and Zn by 41.85% and 41.85%, but the presence of As(V) reduced Na by 22.85% (P5V1) and 49.95% (P5V10). The co-exposure significantly affected the physiological and biochemical indicators as well as the nutritional quality of the lettuce. Finally, the metabolomic analysis of the lettuce leaves showed that combined pollution with PS-MPs and As(V) affected the metabolic pathways of the tricarboxylic acid cycle (TCA cycle), sulfur metabolism, and pyruvate metabolism. This study provides data for pollution management measures for co-exposure to PS-MPs and As(V).

Conventional and biodegradable microplastics affected arsenic mobility and methylation in paddy soils through distinct chemical-microbial pathways

The presence of microplastics (MPs) in paddy soil has become a growing concern, yet the influence of MPs on arsenic (As) dynamics in paddy soil remains largely unexplored. A 98-day microcosm experiment was conducted to investigate the impact of MPs on As behavior in As-contaminated paddy soil. The results revealed that conventional microplastics (CMPs) reduced As concentration in porewater by 25-38 %, but substantially increased the percentage of methylated As (% MeAs) in soil by 8-23 times under 5 % dosages after 98-day incubation. In contrast, at the end of incubation, biodegradable microplastics (BMPs) at 5 % dosages notably increased As concentration in porewater and % MeAs in soil by 2-9 times and 11-395 times, respectively. The combination of network analysis and Random-Forest analysis implied that CMPs might inhibit As mobility through enhancing microbial As(III) oxidation and promote As methylation by enriching arsM-carrying microbes. However, BMPs promoted As release mainly accompanying with microbial iron reduction, and enhanced As methylation through enriching fermenting bacteria (i.e., Clostridiaceae) and arsM-carrying organic matter degrading bacteria (i.e., Gemmatimonas and Nocardia). These findings might provide broaden insights into As cycling induced by MPs and contribute to the prevention of combined pollution from As and MPs in paddy soil.

Polystyrene microplastics as carriers for nano-hydroxyapatite particles: Impact of surface functionalization and mechanistic insights

The potential of microplastics (MPs) to act as carriers for contaminants or engineered nanomaterials is of rising concern. However, directly determining the vector effect of polystyrene (PS) MPs towards nano-hydroxyapatite (nHAP) particles, a typical nano phosphorus fertilizer and soil remediation material, has been rarely studied. In this study, the interaction of differentially surface functionalized PS MPs with nHAP were investigated through batch experiments under different solution chemistry conditions. The results demonstrated that nHAP had the highest attachment/adsorption affinity onto carboxyl-functionalized PS, followed by bare PS and amino-functionalized PS under near-neutral pH conditions. Adsorption of nHAP exhibited a strong pH-dependent behavior with PS MPs, increasing under acidic-neutral pH (3-7) and decreasing at higher pH values. The presence of humic acid and NaCl hindered the adsorption of nHAP onto MPs. Scanning electron microscopy observations revealed a rod-like morphology for adsorbed nHAP, which was randomly distributed on MPs surface. Surface complexation and cation-π interaction were mainly responsible for the adsorption of nHAP as revealed by multiple spectroscopic analyses. These results provide mechanistic insights into nHAP-PS interactions and expound the effect of surface functionalization of PS on binding mechanisms, and thus bring important clues for better understanding the vector effects of MPs towards nanoparticles.

Adsorption behavior and quantum chemical analysis of surface functionalized polystyrene nano-plastics on gatifloxacin

In this paper, the adsorption of gatifloxacin (GAT) by three types of polystyrene nano-plastics (PSNPs), including 400 nm polystyrene (PS), amino-modified PS (PS-NH2), and carboxyl-modified PS (PS-COOH) was studied and the adsorption mechanism were assessed. Experimental findings revealed that the equilibrium adsorption capacity of PSNPs to GAT followed the order PS-NH2 > PS-COOH > PS. The adsorption was regulated by both physical and chemical mechanisms, with intra-particle and external diffusion jointly controlling the adsorption rate. The adsorption process was heterogeneous, spontaneous, and entropy-driven. Sodium chloride (NaCl), alginic acid, copper ions (Cu2+), and zinc ions (Zn2+) inhibited adsorption, with Cu2+ and Zn2+ having the strongest effect on PS-NH2. Theoretical computations indicated that π-π and electrostatic interactions dominated PS adsorption of GAT, while PS-COOH and PS-NH2 adsorbed GAT through electrostatic interactions, hydrogen bonds, and van der Waals (vdW) forces. The surface electrostatic potential of PS-COOH and PS-NH2 was considerably higher than that of PS, with the maximum vdW penetration distance of GAT-PS-NH2 being 1.20 Å. This study's findings provide a theoretical foundation for the migration and synergistic removal of antibiotics, micro-plastics (MPs), and nano-plastics (NPs).

The effects of polystyrene microparticles on the environmental availability and bioavailability of As, Cd and Hg in soil for the land snail Cantareus aspersus

The combined contamination of terrestrial environments by metal(loid)s (MEs) and microplastics (MPs) is a major environmental issue. Once MPs enter soils, they can interact with MEs and modify their environmental availability, environmental bioavailability, and potential toxic effects on biota. Although research efforts have been made to describe the underlying mechanisms driving MP and ME interactions, the effects of MPs on ME bioavailability in terrestrial Mollusca have not yet been documented. To fill this gap, we exposed the terrestrial snail Cantareus aspersus to different combinations of polystyrene (PS) and arsenic (As), cadmium (Cd), or mercury (Hg) concentrations. Using kinetic approaches, we then assessed the variations in the environmental availability of As, Cd or Hg after three weeks of equilibration and in the environmental bioavailability of As, Cd or Hg to snails after four weeks of exposure. We showed that while environmental availability was influenced by the total ME concentration, the effects of PS were limited. Although an increase in As availability was observed for the highest exposure concentrations at the beginning of the experiment, the soil ageing processes led to rapid adsorption in the soil regardless of the PS particle concentration. Concerning transfers to snail, ME bioaccumulation was ME concentration-dependent but not modified by the PS concentration in the soils. Nevertheless, the kinetic approaches evidenced an increase in As (2- to 2.6-fold) and Cd (1.6-fold), but not Hg, environmental bioavailability or excretion (2.3- to 3.6-fold for As, 1.8-fold for Cd) at low PS concentrations. However, these impacts were no longer observable at the highest PS exposure concentrations because of the increase in the bioaccessibility of MEs in the snail digestive tract. The generalization of such hormetic responses and the identification of the precise mechanisms involved necessitate further research to deepen our understanding of the MP-mediated behaviour of MEs in co-occurring scenarios.

Interaction mechanism of water-soluble inorganic arsenic onto pristine nanoplastics

Nanoplastics (NPLs) persist in aquatic habitats, leading to incremental research on their interaction mechanisms with metalloids in the environment. In this regard, it is known that plastic debris can reduce the number of water-soluble arsenicals in contaminated environments. Here, the arsenic interaction mechanism with pure NPLs, such as polyethylene terephthalate (PET), aliphatic polyamide (PA), polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), and polystyrene (PS) is evaluated using computational chemistry tools. Our results show that arsenic forms stable monolayers on NPLs through surface adsorption, with adsorption energies of 9-24 kcal/mol comparable to those on minerals and composite materials. NPLs exhibit varying affinity towards arsenic based on their composition, with As(V) adsorption showing higher stability than As(III). The adsorption mechanism results from a balance between electrostatics and dispersion forces (physisorption), with an average combined contribution of 87%. PA, PET, PVC, and PS maximize the electrostatic effects over dispersion forces, while PE and PP maximize the dispersion forces over electrostatic effects. The electrostatic contribution is attributed to hydrogen bonding and the activation of terminal O-C, C-H, and C-Cl groups of NPLs, resulting in several pairwise interactions with arsenic. Moreover, NPLs polarity enables high mobility in aqueous environments and fast mass transfer. Upon adsorption, As(III) keeps the NPLs polarity, while As(V) limits subsequent uptake but ensures high mobility in water. The solvation process is destabilizing, and the higher the NPL polarity, the higher the solvation energy penalty. Finally, the mechanistic understanding explains how temperature, pressure, pH, salinity, and aging affect arsenic adsorption. This study provides reliable quantitative data for sorption and kinetic experiments on plastic pollution and enhances our understanding of interactions between water contaminants.

Unveiling the Modification of Esterase-like Activity of Serum Albumin by Nanoplastics and Their Cocontaminants

Nanoplastics and other cocontaminants have raised concerns due to their widespread presence in the environment and their potential to enter the food chain. The harmful effects of these particles depend on various factors, such as nanoparticle size, shape, surface charge, and the nature of the cocontaminants involved. On entering the human body, human serum albumin (HSA) molecules bind and transport these particles in the blood system. The esterase-like activity of HSA, which plays a role in metabolizing drug/toxic compounds, was taken as a representative to portray the effects of these particles on HSA. Polystyrene nanoplastics (PSNPs) with different surface functionalization (plain (PS), amine (PS-NH2), and carboxy (PS-COOH)), different sizes (100 and 500 nm), and PS with cocontaminant metformin hydrochloride (Met-HCl), a widely used antidiabetic drug, were investigated in this study. Fluorescence emission spectra of HSA revealed that PS-NH2 exhibits a greater effect on protein conformation, smaller NPs have a greater influence on protein structure than larger NPs, and Met-HCl lowers PSNPs' affinity for HSA by coating the surface of the NPs, which may result in direct NP distribution to the drug's target organs and toxicity. Circular dichroism spectra also supported these results in terms of secondary structural changes. Esterase activity of HSA was inhibited by all the particles (except Met-HCl) by competitive inhibition as concluded from constant Vmax and increasing Km. Greater reduction in enzyme activity was observed for PS-NH2 among functionalizations and for 100 nm PS among sizes. Furthermore, Met-HCl lowers the inhibitory impact of PSNPs on HSA since the drug binds weakly to HSA, and so they can serve as a vector delivering PSNPs to their target organs, resulting in serious implications.

Journey of micronanoplastics with blood components

The entry of micro- and nanoplastics (MNPs) into the human body is inevitable. They enter blood circulation through ingestion, inhalation, and dermal contact by crossing the gut-lung-skin barrier (the epithelium of the digestive tract, the respiratory tract, and the cutaneous layer). There are many reports on their toxicities to organs and tissues. This paper presents the first thorough assessment of MNP-driven bloodstream toxicity and the mechanism of toxicity from the viewpoint of both MNP and environmental co-pollutant complexes. Toxic impacts include plasma protein denaturation, hemolysis, reduced immunity, thrombosis, blood coagulation, and vascular endothelial damage, among others, which can lead to life-threatening diseases. Protein corona formation, oxidative stress, cytokine alterations, inflammation, and cyto- and genotoxicity are the key mechanisms involved in toxicity. MNPs change the secondary structure of plasma proteins, thereby preventing their transport functions (for nutrients, drugs, oxygen, etc.). MNPs inhibit erythropoiesis by influencing hematopoietic stem cell proliferation and differentiation. They cause red blood cell and platelet aggregation, as well as increased adherence to endothelial cells, which can lead to thrombosis and cardiovascular disease. White blood cells and immune cells phagocytose MNPs, provoking inflammation. However, research gaps still exist, including gaps regarding the combined toxicity of MNPs and co-pollutants, toxicological studies in human models, advanced methodologies for toxicity analysis, bioaccumulation studies, inflammation and immunological responses, dose-response relationships of MNPs, and the effect of different physiochemical characteristics of MNPs. Furthermore, most studies have analyzed toxicity using prepared MNPs; hence, studies must be undertaken using true-to-life MNPs to determine the real-world scenario. Additionally, nanoplastics may further degrade into monomers, whose toxic effects have not yet been explored. The research gaps highlighted in this review will inspire future studies on the toxicity of MNPs in the vascular/circulatory systems utilizing in vivo models to enable more reliable health risk assessment.