Adsorption mechanism of two pesticides on polyethylene and polypropylene microplastics: DFT calculations and particle size effects

Interaction characteristics and mechanism of Cr(VI)/Cr(III) with microplastics: Influence factor experiment and DFT calculation

The coexistence of highly toxic heavy metal chromium and new pollutants microplastics has been widely present, and the interaction behavior and mechanism of the two are crucial for their environmental effects in coexisting environments, which urgently need to be further explored. Firstly, the interaction characteristics of polyamide (PA) and polyethylene (PE) with Cr(VI)/Cr(III) were investigated, where PA exhibited higher adsorption capacity of both Cr(VI) and Cr(III) than PE among various environmental conditions. The higher adsorption energy of PA on Cr(VI)/Cr(III) was also achieved by DFT calculation, and the bending configuration of PA during the adsorption process may be beneficial for its interaction with Cr. Then, the combination of characterization analysis and DFT calculation showed that significant chemical bonding occurred in the interaction between CO bond of PA and Cr(III), weak chemical interactions occurred in the adsorption of PE with Cr(III) and PA with Cr(VI), while the adsorption of PE with Cr(VI) was mainly physical effects. This study provides theoretical support for pollution control of microplastics and chromium in co-existing environment.

Environmental risks of mask wastes binding pollutants: Phytotoxicity, microbial community, nitrogen and carbon cycles

The increasing contamination of mask wastes presents a significant global challenge to ecological health. However, there is a lack of comprehensive understanding regarding the environmental risks that mask wastes pose to soil. In this study, a total of 12 mask wastes were collected from landfills. Mask wastes exhibited negligible morphological changes, and bound eight metals and four types of organic pollutants. Masks combined with pollutants inhibited the growth of alfalfa and Elymus nutans, reducing underground biomass by 84.6 %. Mask wastes decreased the Chao1 index and the relative abundances (RAs) of functional bacteria (Micrococcales, Gemmatimonadales, and Sphingomonadales). Metagenomic analysis showed that mask wastes diminished the RAs of functional genes associated with nitrification (amoABC and HAO), denitrification (nirKS and nosZ), glycolysis (gap2), and TCA cycle (aclAB and mdh), thereby inhibiting the nitrogen transformation and ATP production. Furthermore, some pathogenic viruses (Herpesviridae and Tunggulvirus) were also found on the mask wastes. Structural equation models demonstrated that mask wastes restrained soil enzyme activities, ultimately affecting nitrogen and carbon cycles. Collectively, these evidences indicate that mask wastes contribute to soil health and metabolic function disturbances. This study offers a new perspective on the potential environmental risks associated with the improper disposal of masks.

Enhancing aggregation of microalgae on polystyrene microplastics by high light: Processes, drivers, and environmental risk assessment

Microplastics (MPs) are emerging pollutants, causing potential threats to aquatic ecosystems and serious concern in aggregating with microalgae (critical primary producers). When entering water bodies, MPs are expected to sink below the water surface and disperse into varying water compartments with different light intensities. However, how light influences the aggregation processes of algal cells onto MPs and the associated molecular coupling mechanisms and derivative risks remain poorly understood. Herein, we investigated the aggregation behavior between polystyrene microplastics (mPS, 10 µm) and Chlorella pyrenoidosa under low (LL, 15 μmol·m-2·s-1), normal (NL, 55 μmol·m-2·s-1), and high light (HL, 150 μmol·m-2·s-1) conditions from integrated in vivo and in silico assays. The results indicated that under LL, the mPS particles primarily existed independently, whereas under NL and HL, C. pyrenoidosa tightly bounded to mPS by secreting more protein-rich extracellular polymeric substances. Infrared spectroscopy analysis and density functional theory calculation revealed that the aggregation formation was driven by non-covalent interaction involving van der Waals force and hydrogen bond. These processes subsequently enhanced the deposition and adherence capacity of mPS and relieved its phytotoxicity. Overall, our findings advance the practical and theoretical understanding of the ecological impacts of MPs in complex aquatic environments.

The native submerged plant, Hydrilla verticillata outperforms its exotic confamilial with exposure to polyamide microplastic pollution: Implication for wetland revegetation and potential driving mechanism

Microplastic pollution and biological invasion, as two by-products of human civilization, interfere the ecological function of aquatic ecosystem. The restoration of aquatic vegetation has been considered a practical approach to offset the deterioration of aquatic ecosystem. However, a lack of knowledge still lies in the species selection in the revegetation when confronting the interference from microplastic pollution and exotic counterpart. The present study subjected the native submerged species, Hydrilla verticillata and its exotic confamilial, Elodea nuttallii to the current and future scenarios of polyamide microplastic pollution. The plant performance proxies including biomass and ramet number were measured. We found that the native H. verticillata maintained its performance while the exotic E. nuttallii showed decreases in biomass and ramet number under severest pollution conditions. The restoration of native submerged plant such as H. verticillata appeared to be more effective in stabilizing aquatic vegetation in the scenario of accelerating microplastic pollution. In order to explore the underlying driving mechanism of performance differentiation, stress tolerance indicators for plants, sediment enzymatic activity and sediment fungal microbiome were investigated. We found that polyamide microplastic had weak effects on stress tolerance indicators for plants, sediment enzymatic activity and sediment fungal diversity, reflecting the decoupling between these indicators and plant performance. However, the relative abundance of sediment arbuscular mycorrhizal fungi for H. verticillata significantly increased while E. nuttallii gathered "useless" ectomycorrhizal fungi at the presence of severest polyamide microplastic pollution. We speculate that the arbuscular mycorrhizal fungi assisted the stabilization of plant performance for H. verticillata with exposure to the severest polyamide microplastic pollution.

Detrimental consequences of micropolymers associated plasticizers on endocrinal disruption

The prevalence of polymer usage in everyday activities has emerged as a detriment to both human life and the environment. A large number of studies describe severe impacts of micropolymers (MP) and nanopolymers (NP) on various organ systems, including the endocrine system. Additionally, plasticizers utilized as additives have been identified as endocrine-disrupting chemicals (EDCs). MP/NP, along with associated plasticizers, affect principal signalling pathways of endocrine glands such as the pituitary, thyroid, adrenal, and gonads, thereby disrupting hormone function and metabolic processes crucial for maintaining homeostasis, fertility, neural development, and fetal growth. This review delves into the sources, distribution, and effects of micropolymers, nanopolymers, and associated plasticizers acting as EDCs. Furthermore, it provides a detailed review of the mechanisms underlying endocrine disruption in relation to different types of MP/NP.

Understanding the carbendazim adsorption from water using biochar derived from apple pomace and industrial wastewater sludge: experimental and DFT approaches

Biochars derived from apple pomace (AP-BC) and industrial wastewater sludge (IS-BC) were used to investigate adsorption performance and mechanism for removing carbendazim from water and compare its performance with commercial biochar (commercial BC). The results showed that the adsorption capacity of AP-BC and IS-BC were 76 mg g-1 and 82 mg g-1 respectively that was comparable with the commercial BC (80 mg g-1). The adsorption kinetics and isotherms were best described by the Pseudo-second-order and Langmuir models. Thermodynamic analysis suggested that higher temperatures can enhance the mobility of molecules, increased mobility facilitates more frequent and stronger interactions between the adsorbate molecules and the surface of the adsorbent material, leading to greater adsorption capacity. Density functional theory (DFT) calculations confirmed carbendazim's weak electrophilic nature, supporting the primary physisorption mechanism. Even after five cycles of recycling, both biochars maintained a consistent carbendazim removal efficiency of around 82%, highlighting their high reusability. In this study, the examination of waste-derived biochar's economic feasibility revealed that using biochars derived from waste biomass for large-scale wastewater treatment applications is an economically viable choice.

Adsorption behavior of triazine pesticides on polystyrene microplastics aging with different processes in natural environment

The presence of microplastics in the ecological environment, serving as carriers for other organic pollutants, has garnered widespread attention. These microplastics exposed in the environment may undergo various aging processes. However, there is still a lack of information regarding how these aged microplastics impact the environmental behavior and ecological toxicity of pollutants. In this study, we modified polystyrene microplastics by simulating the aging behavior that may occur under environmental exposure, and then explored the adsorption behavior and adsorption mechanism of microplastics before and after aging for typical triazine herbicides. It was shown that all aging treatments of polystyrene increased the adsorption of herbicides, the composite aged microplastics had the strongest adsorption capacity and the fastest adsorption rate, and of the three herbicides, metribuzin was adsorbed the most by microplastics. The interactions between microplastics and herbicides involved mechanisms such as hydrophobic interactions, surface adsorption, the effect of π-π interactions, and the formation of hydrogen bonds. Further studies confirmed that microplastics adsorbed with herbicides cause greater biotoxicity to E. coli. These findings elucidate the interactions between microplastics before and after aging and triazine herbicides. Acting as carriers, they alter the environmental behavior and ecological toxicity of organic pollutants, providing theoretical support for assessing the ecological risk of microplastics in water environments.

Microplastics derived from plastic mulch films and their carrier function effect on the environmental risk of pesticides

Plastic film mulching can maintain soil water and heat conditions, promote plant growth and thus generate considerable economic benefits in agriculture. However, as they age, these plastics degrade and form microplastics (MPs). Additionally, pesticides are widely utilized to control organisms that harm plants, and they can ultimately enter and remain in the environment after use. Pesticides can also be sorbed by MPs, and the sorption kinetics and isotherms explain the three stages of pesticide sorption: rapid sorption, slow sorption and sorption equilibrium. In this process, hydrophobic and partition interactions, electrostatic interactions and valence bond interactions are the main sorption mechanisms. Additionally, small MPs, biodegradable MPs and aged conventional MPs often exhibit stronger pesticide sorption capacity. As environmental conditions change, especially in simulated biological media, pesticides can desorb from MPs. The utilization of pesticides by environmental microorganisms is the main factor controlling the degradation rate of pesticides in the presence of MPs. Pesticide sorption by MPs and size effects of MPs on pesticides are related to the internal exposure level of biological pesticides and changes in pesticide toxicity in the presence of MPs. Most studies have suggested that MPs exacerbate the toxicological effects of pesticides on sentinel species. Hence, the environmental risks of pesticides are altered by MPs and the carrier function of MPs. Based on this, research on the affinity between MPs and various pesticides should be systematically conducted. During agricultural production, pesticides should be cautiously selected and used plastic film to ensure human health and ecological security.

Microplastics and Endocrine Disruptors in Typical Wastewater Treatment Plants in Megacity Shanghai

The fast development of China's urbanization has led to a notable release of emerging pollutants, including microplastics (MPs) and endocrine disruptors (EDCs). Generally, these pollutants enter the coastal environment through the discharge of wastewater treatment plants (WWTPs) and finally threaten the organisms in the receiving waterbody. The study investigated the environmental behavior of MPs and EDCs in two typical WWTPs in one of the megacities in China, Shanghai. The abundance of MPs in the influent ranged from 321 to 976 items/L. Four shapes (films, fragments, fibers, and microbead) were found, while fibers and films dominated. Transparent (31-63%) and white (20-47%) MPs were more frequently observed, while polyethylene terephthalate, cellulose, and cellophane were the main polymetric materials. The size of the MPs fell between 15.8 μm and 2220 μm, and the smaller one (<500 μm) dominated. The removal efficiencies of the two WWTPs for MPs ranged from 64% to 92%, and both WWTPs performed better for large pieces of MPs (>500 μm). For EDCs, total concentrations in the influent were detected, ranging from 113 to 2780 ng/L. Two groups, including phenolic estrogens (PEs) and steroid estrogens (SEs), were detected, and PEs, especially bisphenol A (BPA), were the predominant individuals among the studied EDCs. Specifically, PEs ranged from 82.8 to 2637 ng/L, while SEs ranged from 27.3 to 143 ng/L. The removal efficiencies of the WWTPs for EDCs varied (82.8-100%) as well, possibly due to the different treatment compartments and contamination load in the influent. Seasonal variations for both MPs and EDCs were observed. Specifically, concentrations of MPs and EDCs in WWTPs influent were higher in the wet season, as well as the removal efficiency. Furthermore, there was a correlation observed between the concentrations of MPs and EDCs, suggesting that MPs and EDCs may originate from the same source and that EDCs released by MPs cannot be ignored during treatment. Finally, the study evaluated the environmental risk of the effluents. MPs led to a minor risk (Level I), while EDCs might lead to an adverse impact on algae (RQs = 0.0014-0.024) and fish (RQs = 3.4-30.2). In summary, WWTPs received considerable amounts of MPs and EDCs. Although the WWTPs removed the contaminants efficiently, the environmental risk of the effluent needs to be noted.

Combined toxic effects of polyethylene microplastics and lambda-cyhalothrin on gut of zebrafish (Danio rerio)

Microplastics (MPs), which are prevalent and increasingly accumulating in aquatic environments. Other pollutants coexist with MPs in the water, such as pesticides, and may be carried or transferred to aquatic organisms, posing unpredictable ecological risks. This study sought to assess the adsorption of lambda-cyhalothrin (LCT) by virgin and aged polyethylene MPs (VPE and APE, respectively), and to examine their influence on LCT's toxicity in zebrafish, specifically regarding acute toxicity, oxidative stress, gut microbiota and immunity. The adsorption results showed that VPE and APE could adsorb LCT, with adsorption capacities of 34.4 mg∙g-1 and 39.0 mg∙g-1, respectively. Compared with LCT exposure alone, VPE and APE increased the acute toxicity of LCT to zebrafish. Additionally, exposure to LCT and PE-MPs alone can induce oxidative stress in the zebrafish gut, while combined exposure can exacerbate the oxidative stress response and intensify intestinal lipid peroxidation. Moreover, exposure to LCT or PE-MPs alone promotes inflammation, and combined exposure leads to downregulation of the myd88-nf-κb related gene expression, thus impacting intestinal immunity. Furthermore, exposure to APE increased LCT toxicity to zebrafish more than VPE. Meanwhile, exposure to PE-MPs and LCT alone or in combination has the potential to affect gut microbiota function and alter the abundance and diversity of the zebrafish gut flora. Collectively, the presence of PE-MPs may affect the toxicity of pesticides in zebrafish. The findings emphasize the importance of studying the interaction between MPs and pesticides in the aquatic environment.

Combined effects of polyethylene microplastics and carbendazim on Eisenia fetida: A comprehensive ecotoxicological study

Microplastic (MP) pollution is becoming an emerging environmental concern across aquatic and terrestrial ecosystems. Plastic mulching and the use of pesticides in agriculture can lead to microplastics and agrochemicals in soil, which can result in unintended exposure to non-target organisms. The combined toxicity of multiple stressors represents a significant paradigm shift within the field of ecotoxicology, and its exploration within terrestrial ecosystems involving microplastics is still relatively limited. The present study investigated the combined effects of polyethylene MP (PE-MP) and the agrochemical carbendazim (CBZ) on the earthworm Eisenia fetida at different biological levels of organization. While E. fetida survival and reproduction did not exhibit significant effects following PE-MP treatment, there was a reduction in cocoon and hatchling numbers. Notably, prolonged exposure revealed delayed toxicity, leading to substantial growth impairment. Exposure to CBZ led to significant alterations in the endpoints mentioned above. While there was a decrease in cocoon and hatchling numbers, the combined treatment did not yield significant effects on earthworm reproduction except at higher concentrations. However, lower concentrations of PE-MP alongside CBZ induced a noteworthy decline in biomass content, signifying a form of potentiation interaction. In addition, concurrent exposure led to synergistic effects, from oxidative stress to modifications in vital organs such as the body wall, intestines, and reproductive structures (spermathecae, seminal vesicles, and ovarian follicles). The comparison of multiple endpoints revealed that seminal vesicles and ovarian follicles were the primary targets during the combined exposure. The research findings suggest that there are variable and complex responses to microplastic toxicity in terrestrial ecosystems, especially when combined with other chemical stressors like agrochemicals. Despite these difficulties, the study implies that microplastics can alter earthworms' responses to agrochemical exposure, posing potential ecotoxicological risks to soil fauna.

Elucidating adsorption mechanisms of benzalkonium chlorides (BACs) on polypropylene and polyethylene terephthalate microplastics (MPs): Effects of BACs alkyl chain length and MPs characteristics

Since the onset of the COVID-19 pandemic, there has been an increase in the use of disposable plastics and disinfectants. This study systematically investigated the adsorption behavior and mechanisms of benzalkonium chlorides (BACs), commonly used disinfectants, on polypropylene (PP) and polyethylene terephthalate (PET) microplastics (MPs), considering various factors, such as characteristics of MPs, alkyl chain length of BACs, and environmental conditions. Our results demonstrated a higher adsorption capacity for PP-MPs with relatively hydrophobic properties compared to PET-MPs, where longer alkyl chains in BACs (i.e., higher octanol-water partition coefficients, Kow) significantly enhanced adsorption through hydrophobic interactions. The inverse relationship between particle size of MPs and adsorption was evident. While changes in pH minimally affected adsorption on PP-MPs, adsorption on PET-MPs increased with rising pH, highlighting the influence of pH on electrostatic interactions. Moreover, MP aging with UV/H2O2 amplified BAC adsorption on PP-MPs due to surface oxidation and fragmentation, whereas the properties of PET-MPs remained unaltered, resulting in unchanged adsorption capacities. Spectroscopy studies and density functional theory (DFT) calculations confirmed hydrophobic and electrostatic interactions as the primary adsorption mechanisms. These findings improve our understanding of MPs and BACs behavior in the environment, providing insights for environmental risk assessments related to combined pollution.

Photoaged microplastics enhanced the antibiotic resistance dissemination in WWTPs by altering the adsorption behavior of antibiotic resistance plasmids

Growing concerns have raised about the microplastic eco-coronas in the ultraviolet (UV) disinfection wastewater, which accelerated the pollution of antibiotic resistance genes (ARGs) in the aquatic environment. As the hotspot of gene exchange, microplastics (MPs), especially for the UV-aged MPs, could alter the spread of ARGs in the eco-coronas and affect the resistance of the environment through adsorbing antibiotic resistant plasmids (ARPs). However, the relationship between the MP adsorption for ARPs and ARG spreading characteristics in MP eco-corona remain unclear. Herein, this study explored the distribution of ARGs in the MP eco-corona through in situ investigations of the discharged wastewater, and the adsorption behaviors of MPs for ARPs by in vitro adsorption experiments and in silico calculations. Results showed that the adsorption capacity of MPs for ARPs was enhanced by 42.7-48.0 % and the adsorption behavior changed from monolayer to multilayer adsorption after UV-aging. It was related to the increased surface roughness and oxygen-containing functional groups of MPs under UV treatment. Moreover, the abundance of ARGs in MP eco-corona of UV-treated wastewater was 1.33-1.55 folds higher than that without UV treatment, promoting the proliferation of drug resistance. DFT and DLVO theoretical calculations indicated that the MP-ARP interactions were dominated by electrostatic physical adsorption, endowing the aged MPs with low potential oxygen-containing groups to increase the electrostatic interaction with ARPs. Besides, due to the desorption of ARPs on MPs driven by the electrostatic repulsion, the bioavailability of ARGs in the MP eco-coronas was increased with pH and decreased with salinity after the wastewater discharge. Overall, this study advanced the understanding of the adsorption behavior of MPs for ARPs and provided inspirations for the evaluation of the resistance spread in the aquatic environment mediated by MP eco-coronas.

Microplastics affect mosquito from aquatic to terrestrial lifestyles and are transferred to mammals through mosquito bites

Microplastics (MPs) transfer from the environment to living organisms is a nonignorable global problem. As a complete metamorphosis insect, the larvae and adult Culex quinquefasciatus mosquito live in aquatic and terrestrial environments, respectively, where they easily access MPs. However, little is known about mosquitoes' potential role in MPs accumulation throughout ecosystems. Therefore, we conducted a study with different MPs particle sizes (0.1/1/10 μm) and concentrations (0.5/5/50 μg/mL) on Cx. quinquefasciatus to address this issue. Once exposed at the young larval stage, MPs could accompany the mosquitoes their entire life. The fluorescence signals of MPs in the larvae were mainly located in the intestines. Its intensity increased (from 3.72 × 106 AU to 5.45 × 107 AU) as the concentrations of MPs increases. The fluorescence signals of MPs were also detected in the blood and skin tissues of mice bitten by adult mosquitoes with MPs containing in their bodies. Mosquitos exposed to MPs showed longer larval pupation and eclosion time as well as lower adult body weight. In addition, MPs significantly reduced the lethal effect of pyrethroid insecticides (97.77 % vs. 48.88 %, p < 0.05) with 15.1 % removal of the deltamethrin concentration. After MPs exposure, the relative abundance of the Cx. quinquefasciatus gut microbiome, such as Wolbachia spp., Elizabethkingia spp., and Asaia spp., changed as the MPs size and concentration changes. Mosquitoes provide a new pathway for MPs accumulation and transfer to higher-level living organisms. Moreover, MPs significantly reduce the control effect of deltamethrin, providing new guidelines for mosquito insecticide application in MPs contamination circumstances.

Combined effects of mulch film-derived microplastics and pesticides on soil microbial communities and element cycling

Pesticides and microplastics (MPs) derived from mulch film in agricultural soil can independently impact soil ecology, yet the consequences of their combined exposure remain unclear. Therefore, the effects of simultaneous exposure to commonly used pesticides (imidacloprid and flumioxazin) and aged mulch film-derived MPs on soil microorganisms and element cycles in cotton fields were investigated. The combined exposure influenced soil microorganisms, alongside processes related to carbon, nitrogen, and phosphorus cycles, exhibiting effects that were either neutralized or enhanced compared to individual exposures. The impact of pesticides in combined exposure was notably more significant and played a dominant role than that of MPs. Specifically, combined exposure intensified changes in soil bacterial community and symbiotic networks. The combined exposure neutralized NH4+, NO3-, DOC, and A-P contents, shifting from 0.33 % and 40.23 % increase in MPs and pesticides individually to a 40.24 % increase. Moreover, combined exposure resulted in the neutralization or amplification of the nitrogen-fixing gene nifH, nitrifying genes (amoA and amoB), and denitrifying genes (nirS and nirK), the carbon cycle gene cbbLG and the phosphorus cycle gene phoD from 0.48 and 2.57-fold increase to a 2.99-fold increase. The combined exposure also led to the neutralization or enhancement of carbon and nitrogen cycle functional microorganisms, shifting from a 1.53-fold inhibition and 10.52-fold increase to a 6.39-fold increase. These findings provide additional insights into the potential risks associated with combined pesticide exposure and MPs, particularly concerning soil microbial communities and elemental cycling processes.

Multifunctional Eu3+-MOF for simultaneous quantification of malachite green and leuco-malachite green and efficient adsorption of malachite green

Multi-target detection combined with in-situ removal of contaminants is a challenging issue difficult to overcome. Herein, a dual-emissive Eu3+-metal organic framework (Eu3+-MOF) was constructed by pre-functionalization with a blue-emissive ligand and post-functionalization with red-emissive Eu3+ ions using a UiO-66 precursor. The fluorescence of the synthesized Eu3+-MOF is highly selective and sensitive toward malachite green (MG) and its metabolite leuco-malachite green (LMG), which are environmentally persistent and highly toxic to humans. The limit of detection of MG and LMG are 34.20 and 1.98 nM, respectively. Interestingly, the fluorescence of this Eu3+-MOF showed ratiometric but different responsive modes toward MG and LMG, which enabled the simultaneous quantification of MG and LMG. Furthermore, a paper-based sensor combined with the smartphone was fabricated, which facilitated not only the dual-channel detection of MG, but also its portable, visual, rapid, and intelligent determination. Furthermore, the high surface area of MOFs, together with the coordinate bonding interaction, π-π stacking, and electrostatic interaction sites, endows Eu3+-MOF with the efficient ability toward MG removal. This multifunctional Eu3+-MOF can be successfully used for trace detection, simultaneous determination of MG and LMG, as well as efficient removal of MG. Thus, it exhibits bright prospects for widespread applications in the field of food and environmental analysis.

An Atomic-Level Perspective on the interactions between Organic Pollutants and PET particles: A Comprehensive Computational Investigation

Microplastics (MPs) have recently attracted a lot of attention worldwide due to their abundance and potentially harmful effects on the environment and on human health. One of the factors of concern is their ability to adsorb and disperse other harmful organic pollutants in the environment. To properly assess the adsorption capacity of MP for organic pollutants in different environments, it is pivotal to understand the mechanisms of their interactions in detail at the atomic level. In this work, we studied interactions between polyethylene terephthalate (PET) MP and small organic pollutants containing different functional groups within the framework of density functional theory (DFT). Our computational outcomes show that organic pollutants mainly bind to the surface of a PET model via weak non-bonding interactions, mostly hydrogen bonds. The binding strength between pollutant molecules and PET particles strongly depends on the adsorption site while we have found that the particle size is of lesser importance. Specifically, carboxylic sites are able to form strong hydrogen bonds with pollutants containing hydrogen bond donor or acceptor groups. On the other hand, it is found that in such kind of systems π-π interactions play a minor role in adsorption on PET particles.

Evaluation of the sorption/desorption processes of pesticides in biodegradable mulch films used in agriculture

Microplastics from mulch films can be a source of chemical contamination to agricultural soils. In this context, biodegradable films have been widely positioned as a greener choice. However, their sorption/desorption capabilities, in contrast to the conventional plastic types remain understudied. It is for this reason that objective evaluation of their interactions with residual agricultural contaminants becomes important. Our findings reveal that polyethylene (PE) mulch films retained lower amounts of pesticide residues and demonstrated a higher desorption/release [median desorption = 71.86 μg/L or about 50%], while polybutylene adipate terephthalate (PBAT) mulch films retained higher amounts of pesticide residues onto their surface and demonstrated a much lower desorption [median desorption = 24.27 μg/L or about 17%] after a spraying event. A higher ambient temperature had no significant effect on final desorption amounts in both PE [median = 65.27 μg/L at 20 °C and 74.23 μg/L at 40 °C] and PBAT [median = 24.26 μg/L at 20 °C and 24.78 μg/L at 40 °C] mulch films. However, it did favour a faster desorption pace in PE films. Desorption in PBAT and PE plastic types was correlated with the log Kow value [Spearman's correlation: 0.857 and 0.837 respectively, p < 0.05]. However, only a moderate correlation with pKa was observed in PBAT [Spearman's correlation: 0.478, p < 0.05], while none for PE plastic type. Sorption of pesticides onto biodegradable PBAT microplastics were best explained by Elovich [R2: 0.937-0.959] and pseudo-second order kinetics [R2: 0.942-0.987], suggesting the presence of chemisorption. Furthermore, Weber Morris plots suggested the presence of a multi-step process and Boyd plots indicated that film diffusion or chemical bond formation was the rate-limiting step governing this phenomenon.

The adsorption effects of biochar on carbofuran in water and the mixture toxicity of biochar-carbofuran in rats

Carbofuran, a widely used carbamate insecticide, is frequently detected in water. In this study, a high-performance adsorbent (WAB4) for carbofuran was obtained from laboratory-synthesized biochars. The maximum adsorption of carbofuran by WAB4 reaches 113.7 mg/g approximately. The adsorption of carbofuran by biochar was a multi-molecular layer and the adsorption process conforms to the pseudo-second-order kinetic model (R2 = 0.9984) and Freundlich isotherm model (R2 = 0.99). Importantly, an in vivo rat model was used to assess the combined toxicological effects of biochar-carbofuran complexes. The toxicity of the complexes (LD50 > 12 mg/kg) is lower than that of carbofuran (LD50 = 7.9 mg/kg) alone. The damage of biochar-carbofuran complex on rat liver and lung is significantly less than that of carbofuran. The Cmax and bioavailability of carbofuran were found to be reduced by 64% and 68%, respectively, when biochar was present, by UPLC-MS/MS analysis of carbofuran in rat plasma. Furthermore, it was confirmed that the biochar-carbofuran complex is relatively stable in the gastrointestinal tract, by performing a carbofuran release assay in artificial gastrointestinal fluids in vitro. Collectively, biochar is a bio-friendly material for the removal of carbofuran from water.

A review of recent progress in the application of Raman spectroscopy and SERS detection of microplastics and derivatives

The global environmental concern surrounding microplastic (MP) pollution has raised alarms due to its potential health risks to animals, plants, and humans. Because of the complex structure and composition of microplastics (MPs), the detection methods are limited, resulting in restricted detection accuracy. Surface enhancement of Raman spectroscopy (SERS), a spectral technique, offers several advantages, such as high resolution and low detection limit. It has the potential to be extensively employed for sensitive detection and high-resolution imaging of microplastics. We have summarized the research conducted in recent years on the detection of microplastics using Raman and SERS. Here, we have reviewed qualitative and quantitative analyses of microplastics and their derivatives, as well as the latest progress, challenges, and potential applications.

Comparing the adsorption of methyl orange and malachite green on similar yet distinct polyamide microplastics: Uncovering hydrogen bond interactions

Microplastics (MPs) and dye pollutants are widespread in aquatic environments. Here, the adsorption characteristics of anionic dye methyl orange (MO) and cationic dye malachite green (MG) on polyamide 6 (PA6) and polyamide 66 (PA66) MPs were investigated, including kinetics, isotherm equilibrium and thermodynamics. The co-adsorption of MO and MG under different pH was also evaluated. The results reveal that the adsorption process of MO and MG is suitably expounded by a pseudo-second-order kinetic model. The process can be characterized by two stages: internal diffusion and external diffusion. The isothermal adsorption equilibrium of MO and MG can be effectively described using the Langmuir model, signifying monolayer adsorption. Furthermore, the thermodynamic results indicated that the adsorption was spontaneous with exothermic and endothermic properties, respectively. The results of binary systems reveal that MO dominates the adsorption at low pH (2-5), while MG dominates at high pH (8-10). Strong competitive adsorption was observed between MO and MG in neutral conditions (pH 6-8). The desorption experiments confirm that PA6 and PA66 could serve as potential carriers of MO and MG. The interaction between dyes and polyamide MPs is primarily mediated through hydrogen bonds and electrostatic attraction. The results reveal that PA6 formed more hydrogen bonds with the dyes, resulting in higher adsorption capacity than that of PA66. This difference can be attributed to the disparities in the synthesis process and polymerization method. Our study uncovered the adsorption mechanism of dye pollutants on PA6 and PA66, and provided a more comprehensive theoretical basis for the risk assessment concerning different types of polyamide MPs in aquatic environments.

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 IMPLICATION: Nanoplastics 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.

Adsorption behaviors and bioavailability of tetrabromobisphenol A in the presence of polystyrene microplastic in soil: Effect of microplastics aging

Microplastics, a kind of emerging pollutant, have become a global environmental research hotspot in recent years due to its wide distribution in soil and its impact on soil ecosystems. However, little information is available on the interactions between microplastics and organic contaminants in soil, especially after microplastic aging. The impact of polystyrene (PS) microplastic aging on the sorption of tetrabromobisphenol A (TBBPA) in soil and the desorption characteristics of TBBPA-loaded microplastics in different environments were studied. The results showed a significant increase of 76.3% in adsorption capacity of TBBPA onto PS microplastics after aging for 96 h. Based on the results of characterization analysis and density functional theory (DFT) calculation, the mechanisms of TBBPA adsorption changed mainly from hydrophobic and π-π interactions on pristine PS microplastics to hydrogen bond and π-π interactions on aged PS microplastics. The presence of PS microplastics increased the TBBPA sorption capacity onto soil-PS microplastics system and significantly altered the distribution of TBBPA on soil particles and PS microplastics. The high TBBPA desorption over 50% from aged PS microplastics in simulated earthworm gut environment suggested that TBBPA contamination combined with PS microplastics might pose a higher risk to macroinvertebrates in soil. Overall, these findings contribute to the understanding of impact of PS microplastic aging in soil on the environmental behaviors of TBBPA, and provide valuable reference for evaluating the potential risk posed by the co-existence of microplastics with organic contaminants in soil ecosystems.

Synergetic effects of polyethylene microplastic and abamectin pesticides on the eyes of zebrafish larvae and adults through activation of apoptosis signaling pathways

Although the toxicity of microplastics (MPs) and pesticides has recently been described, the possible effects of combining these pollutants are poorly understood. Thus, we evaluated the potential impact of exposure to polyethylene MP (PE-MP) and abamectin (ABM) (alone and combined) in zebrafish. After five days, the combined exposure to MP and ABM decreased the survival rate compared to exposures to individual pollutants. A significant increase in reactive oxygen species (ROS), lipid peroxidation, apoptosis, and impairment in antioxidant response was observed in zebrafish larvae. Morphological changes in the eyes of zebrafish significantly increased in the combined exposure group than in the individual exposure. Furthermore, the bax and p53 expression (specific apoptotic genes) was significantly upregulated after the combined exposure to PE-MP and ABM. So, the synergetic effect of MP and ABM cannot be ignored, and further research on other higher models is required to confirm its consequences.

A review of microplastic removal from water and wastewater by membrane technologies

Microplastics (MPs) cannot be completely removed from water/wastewater in conventional wastewater treatment plants (WWTPs) and drinking water treatment plants (DWTPs). According to the literature analysis, membrane technologies, one of the advanced treatment technologies, are the most effective and promising technologies for MP removal from water and wastewater. In this paper, firstly, the properties of MPs commonly present in WWTPs/DWTPs and the MP removal efficiency of WWTPs/DWTPs are briefly reviewed. In addition, research studies on MP removal from water/wastewater by microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), reverse osmosis (RO), and membrane bioreactors (MBRs) are reviewed. In the next section, membrane filtration is compared with other methods used for MP removal from water/wastewater, and the advantages/disadvantages of the removal methods are discussed. Moreover, the problem of membrane fouling with MPs during filtration and the potential for MP release from polymeric membrane structure to water/wastewater are discussed. Finally, based on the studies in the literature, the current status and research deficiencies of MP removal by membrane technologies are identified, and recommendations are made for further studies.

Effects of microplastics on the toxicity of co-existing pollutants to fish: A meta-analysis

Aquatic ecosystems are among the main destination for microplastics (MPs) in the environment. MPs that enter aquatic ecosystems can contribute to pollution together with other co-existing pollutants. However, whether such pollution results in higher or lower toxicity to fish than that caused by co-existing pollutants alone remains controversial. This study aimed at closing this research gap based on 1380 biological endpoints under the background of environmental MP concentrations collected from 55 laboratory studies. Overall, MPs in co-existing pollutant solutions significantly increased the toxicity to fish. Specifically, MPs elevated negative effects on the immune system, metabolism, and oxidative damage. Subgroup analysis indicated that changes in toxicity were related to fish life stage and MP size, but not to co-existing pollutant or MP type. Meta-regression analysis indicated that changes in toxicity were not related to the logarithm of the octanol-water partition coefficient (logKow) or exposure time. Finally, the differences between laboratory research and the actual aquatic environment were discussed from four aspects: MPs, co-existing pollutants, environmental factors, and experimental objects. Our study provides a basis for further understanding the potential impact of MPs on aquatic organisms from a combined pollution perspective. Moreover, our results can provide a reference for the conservation and management of aquatic ecosystems.

Exploring sorption of pesticides and PAHs in microplastics derived from plastic mulch films used in modern agriculture

The sorption and vector effect of microplastics on the transfer of pesticides and polycyclic aromatic hydrocarbons (PAHs), as well as its impact on agriculture remain largely unexplored. This comparative study is first to investigate the sorption behavior of different pesticides and PAHs at environmentally realistic concentrations by model microplastics and microplastics derived from polyethylene mulch films. Sorption was found to be up to 90% higher in the case of microplastics derived from mulch films as opposed to pure polyethylene microspheres. For microplastics from mulch films, the sorption percentages for pesticides in media containing CaCl₂ were reported to be: pyridate (75.68% and 52.44%), fenazaquin (48.54% and 32.02%), pyridaben (45.04% and 56.70%), bifenthrin (74.27% and 25.88%), etofenprox (82.16% and 54.16%) and pyridalyl (97.00% and 29.74%) at 5 μg/L and 200 μg/L pesticide concentration levels respectively. For PAHs, the sorption amounts were: naphthalene (22.03% and 48.00%), fluorene (38.99% and 39.00%), anthracene (64.62% and 68.02%) and pyrene (75.65% and 86.38%) at 5 μg/L and 200 μg/L PAH concentration levels respectively. Sorption was influenced by the octanol-water partition coefficient (log K_ow) and ionic strength. Kinetics of the process in the case of sorption of pesticides were best explained by pseudo-first order kinetic model (R² between 0.90 and 0.98) while the best fitting isotherm model was Dubinin-Radushkevich (R² between 0.92 and 0.99). Results suggest the presence of surface level physi-sorption through a micropore volume filling mechanism and the role of hydrophobic and electrostatic forces. Pesticide desorption data in polyethylene mulch films indicate that pesticides with high log K_ow were almost completely retained in mulch films, while those with lower log K_ow were desorbed rapidly into the surrounding media. Our study highlights the role of microplastics from plastic mulch films as vectors for pesticide and PAH transport at environmentally realistic concentrations and the factors that influence it.

Abundance and characteristics of microplastics in drinking water treatment plants, distribution systems, water from refill kiosks, tap waters and bottled waters

Limited research studies have revealed the presence of microplastics (MPs) of different polymer types, shapes, and sizes in drinking water sources, influents of drinking water treatment plants (DWTPs), effluents of DWTPs, tap water, and bottled water. Reviewing the available information on MP pollution in waters, which is becoming more worrying in correlation with the increasing plastic production in the world every year, is noteworthy for understanding the current situation, identifying the deficiencies in the studies, and taking the necessary measures for public health as soon as possible. Therefore, this paper, in which the abundance, characteristics, and removal efficiencies of MPs in the processes from raw water to tap water and/or bottled water are reviewed is a guide for dealing with MP pollution in drinking water. In this paper, firstly, the sources of MPs in raw waters are briefly reviewed. In addition, the abundance, and characteristics (polymer type, shape, and size) of MPs in influents and effluents of DWTPs in different countries are reviewed and the effects of treatment stages (coagulation, flocculation, sedimentation, sand filtration, disinfection, and membrane filtration) of DWTPs on MP removal efficiency and the factors that are effective in removal are discussed. Moreover, studies on the factors affecting MP release from drinking water distribution systems (DWDSs) to treated water and the abundance and characteristics of MPs in tap water, bottled water and water from refill kiosks are reviewed. Finally, the deficiencies in the studies dealing with MPs in drinking water were identified and recommendations for future studies are presented.

Adsorption behaviors and influencing factors of antibiotic norfloxacin on natural kaolinite-humic composite colloids in aquatic environment

Particles are ubiquitous and abundant in natural waters and play a crucial role in the fate and bioavailability of organic pollution. In the present study, natural mineral (kaolinites, KL), organic (humic/fulvic acid, HA/FA) and their composite particles were further separated into particles fractions (PFs, >1 μm) and colloidal fractions (CFs, 1 kDa-1 μm) by cross-flow ultrafiltration (CFUF). This research demonstrated the role of kaolinite-humic composite colloids on the adsorption of fluoroquinolone norfloxacin (NOR). The Freundlich model satisfactory described adsorption curves, showing strong affinity of NOR to CFs, with sorption capacity (K_F) between 8975.50 and 16638.13 for NOR. The adsorption capacities of NOR decreased with the particle size increasing from CFs to PFs. In addition, composite CFs showed excellent adsorption capacity, which was mainly attributed to the larger specific surface area of composite CFs and electronegativity and numerous oxygen-containing functional groups on the surfaces of the complexes, and electrostatic attraction, hydrogen bond and cation exchange could dominate the NOR adsorption onto the composite CFs. The best pH value under adsorption condition of composite CFs varied from weakly acidic to neutral with the increase of load amount of humic and fulvic acids on the surface of inorganic particles. The adsorption decreased with higher cation strength, larger cation radius and higher cation valence, which depended on the surface charge of colloids and the molecular shape of NOR. These results provided insight into the interfacial behaviors of NOR on the surfaces of natural colloids and promoted the understanding of the migration and transport of antibiotics in environmental systems.

In vitro wheat protoplast cytotoxicity of polystyrene nanoplastics

Nanoplastics are an emerging environmental pollutant, having a potential risk to the terrestrial ecosystem. In the natural environment, almost all the micro-or nano-plastics will be aged by many factors and their characterizations of the surface will be modified. However, the toxicity and mechanism of the modified polystyrene nanoparticles (PS-NPs) to plant cells are not clear. In the study, the amino- and carboxyl-modified PS-NPs with different sizes (20 and 200 nm) were selected as the typical representatives to investigate their effects on protoplast cell viability, reactive oxygen species (ROS) production in the cell and the leakage of cell-inclusion and apoptosis. The results indicated that the 20 nm amino-modified PS-NPs (PS-20A) could significantly damage the structure of the cell, especially the cell membrane, chloroplast and mitochondrion. After being modified by amino group, smaller size nanoplastics had the potential to cause more severe damage. In addition, compared with carboxyl-modified PS-NPs, the amino-modified PS-NPs induced more ROS production and caused higher membrane permeability/lactate dehydrogenase (LDH) leakage. Apoptosis assay indicated that the proportion of viable cells in the PS-20A treatment decreased significantly, and the proportion of necrotic cells increased by four times. This study provides new insights into the toxicity and damage mechanism of PS-NPs to terrestrial vascular plants at the cellular level, and guides people to pay attention to the quality and safety of agricultural products caused by nanoplastics.

Microcystin bound on microplastics in eutrophic waters: A potential threat to zooplankton revealed by adsorption-desorption processes

The presence of microplastics (MPs) in eutrophic waters (both freshwaters and coastal waters) is increasingly reported globally, as has the occurrence of cyanotoxins, including microcystins (MCs). MPs have the potential to act as vectors for MCs in freshwater environments, but the transportation mechanisms and associated risks remain poorly understood. In this study, we investigated how aging process and water conditions influenced the adsorption behavior of the microcystin-leucine-arginine (MC-LR) onto polyethylene (PE) and polypropylene (PP). Adsorption kinetics and isotherms showed that the MC-LR sorption capacity in descending order was aged PP > pristine PP > aged PE > pristine PE. The aging process increased the MC-LR sorption amount by 25.1% and 6.5% for PP and PE, respectively. The increase in sorption affinity of aged MPs may be attributed to the significant surface oxidation and the formation of the hydrogen bonding between MPs and MC-LR. Furthermore, MC-LR sorption can be largely influenced by the aqueous conditions. MC-LR preferred to be much adsorbed onto different MPs in brackish water than in freshwater owing to the cation bridging effect and complexation of high levels of cations. The usual alkalescent pH in eutrophic waters did not favor MC-LR sorption to MPs. Finally, based on the desorption results, assuming a worst-case scenario, MC-LR bound on MPs may have a high risk to daphnids. The findings obtained in this study have improved our knowledge in the interaction of MPs with hydrophilic cyanotoxins in aqueous ecosystems, as well as the risks associated with their coexistence.

Rapid and efficient removal of multiple aqueous pesticides by one-step construction boric acid modified biochar

Tricyclazole, propiconazole, imidacloprid, and thiamethoxam are commonly used pesticides in paddy fields. It is necessary and practical to remove pesticides from the water environment because the low utilization rate of pesticides will produce residues in the water environment. It is known that there are few studies on the preparation of biochar adsorption pesticides by the walnut shell and few studies on the removal of tricyclazole and propiconazole. Based on this, this paper used the walnut shell as raw material and boric acid as an activator to prepare biochar by the one-step method. The boric acid modified walnut shell biochar (WAB4) with a specific surface area of 640.6 m² g^-1, exhibited the high adsorption capacity of all four pesticides (>70%) at pH 3-9. The adsorption capacities of tricyclazole, propiconazole, imidacloprid, and thiamethoxam were 171.67, 112.27, 156.40, and 137.46 mg g^-1, respectively. The adsorption kinetics fitted the pseudo-second-order kinetic model and the adsorption isotherm curves conformed to the Freundlich isotherm model. The adsorption of pesticides by WAB4 was associated with hydrogen bonding, pore filling, hydrophobic effects, and π-π interactions. More significantly, WAB4 has excellent adsorption capacity compared to other adsorbents for real water samples. Finally, walnut shell biochar has no significant acute toxicity to Daphnia magna. This work shows that walnut shell-based biochar has a good effect on the removal of pesticides at a wide range of pH and is economical and safe, providing a new idea for the removal of pesticides in water.

Molecular level insight into the different interaction intensity between microplastics and aromatic hydrocarbon in pure water and seawater

The interaction of MPs and aromatic hydrocarbons in seawater and pure water was examined using experimental measurements, molecular dynamics (MD) simulations, and density functional theory (DFT) calculations in light of the potential health risks posed by microplastic (MPs)-associated aromatic hydrocarbon pollutants. Isothermal studies and MD simulations suggested that MPs have a stronger affinity for aromatic hydrocarbons in seawater. To uncover the mechanism, MPs' surface characteristics and their intermolecular interactions with aromatic hydrocarbons were examined. According to the research, MPs in seawater have less compact structure, bigger pores, and a higher specific surface area, all of which contribute to more sorption sites. Analysis of the intermolecular interaction indicated that MPs have a greater ability for molecular interactions in seawater and the interaction energy between MPs and aromatic hydrocarbons in seawater is higher. Additionally, seawater cations may act as bridges, which also accelerate sorption in seawater. In summary, this study provides a molecular-level understanding of MPs-aromatic hydrocarbons interaction and demonstrates that the interaction is stronger in seawater.

Sorption of representative organic contaminants on microplastics: Effects of chemical physicochemical properties, particle size, and biofilm presence

Microplastic pollution has attracted mounting concerns worldwide. Microplastics may concentrate organic and metallic contaminants; thus, affecting their transport, fate and organismal exposure. To better understand organic contaminant-microplastic interactions, our study explored the sorption of selected polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), α-hexabromocyclododecane (α-HBCDD), and organophosphate flame retardants (OPFRs) on high-density polyethylene (HDPE) and polyvinylchloride (PVC) microplastics under saline conditions. Sorption isotherms determined varied between chemicals and between HDPE and PVC microplastics. Log Freundlich sorption coefficients (Log K_F) for the targeted chemicals ranged from 2.01 to 5.27 L kg^-1 for HDPE, but were significantly lower for PVC, i.e., ranging from Log K_F data (2.84 - 8.58 L kg^-1). Significant correlations between chemicals' Log K_F and Log K_ow (octanol-water partition coefficient) indicate that chemical-dependent sorption was largely influenced by their hydrophobicity. Sorption was evaluated using three size classes (< 53, 53 - 300, and 300 - 1000 µm) of lab-fragmented microplastics. Particle size did not significantly affect sorption isotherms, but influenced the time to reach equilibrium and the predicted maximum sorption, likely related to microplastic surface areas. The presence of biofilms on HDPE particles significantly enhanced contaminant sorption capacity, indicating more complex sorption dynamics in the chemical-biofilm-microplastic system. Our findings offer new insights into the chemical-microplastic interactions in marine environment.

Sorption kinetics, isotherms and molecular dynamics simulation of 17β-estradiol onto microplastics

Microplastic is a new type of pollutant, which can act as a carrier for organic contaminants. It affects the migration and bioavailability of chemicals and potentially threatens the ecology. This work investigated the adsorption kinetics, isotherm and influencing factors of 17β-estradiol (E2) on three dominate microplastics. Then, used molecular dynamics (MD) simulation to analyze the adsorption mechanism. The results showed that E2 adsorption onto microplastics conformed well to the Pseudo-second-order kinetics and Redlich-Petersen isotherm model. The adsorption capacity of E2 on microplastics was polyethylene (PE) > polypropylene (PP) > polystyrene (PS). The small particle size of microplastics was conducive to the adsorption due to its large specific surface area. The thermodynamic parameters demonstrated the adsorption of E2 was a spontaneous and exothermic process, so low temperature was benefit for the adsorption. The MD simulation results indicated the adsorption of E2 on MPs belonged to surface adsorption. The order of E2 adsorption energy by three microplastics obtained by molecular dynamics simulation is consistent with the experimental results. This work may help to understand the molecular adsorption process and provide a theoretical basis for the combined ecotoxicity of microplastics.

Microplastics in wastewater treatment plants: Sources, properties, removal efficiency, removal mechanisms, and interactions with pollutants

Since wastewater treatment plants (WWTPs) cannot completely remove microplastics (MPs) from wastewater, WWTPs are responsible for the release of millions of MPs into the environment even in 1 day. Therefore, knowing the sources, properties, removal efficiencies and removal mechanisms of MPs in WWTPs is of great importance for the management of MPs. In this paper, firstly the sources of MPs in WWTPs and the quantities and properties (polymer type, shape, size, and color) of MPs in influents, effluents, and sludges of WWTPs are presented. Following this, the MP removal efficiency of different treatment units (primary settling, flotation, biological treatment, secondary settling, filtration-based treatment technologies, and coagulation) in WWTPs is discussed. In the next section, details about MP removal mechanisms in critical treatment units (settling and flotation tanks, bioreactors, sand filters, membrane filters, and coagulation units) in WWTPs are given. In the last section, the mechanisms and factors that are effective in adsorbing organic-inorganic pollutants in wastewater to MPs are presented. Finally, the current situation and research gap in these areas are identified and suggestions are provided for topics that need further research in the future.

Effect of tank-mixed adjuvant on the behavior of chlorantraniliprole and difenoconazole in soil

In this study, both laboratory and field studies were performed to analyze the effect of the presence of tank-mixed methylated plant oil adjuvant on the adsorption and degradation of chlorantraniliprole (CAP) and difenoconazole (DIF) in soil. Adsorption kinetics and isotherms experiments were conducted according to the equilibrium oscillation method. Fourier transform infrared spectroscopy (FT-IR) analysis, soil contact angle, and zeta potential were used to research the interaction mechanism of adsorption. Fluorescence excitation emission matrix (FEEM) measurements were conducted to characterize soil dissolved organic matter. Field experiment was conducted to investigate the degradation of CAP and DIF combined with adjuvant. DIF exhibited a significantly higher Freundlich maximum adsorption capacity than CAP, which is consistent with the higher octanol-water partition coefficient of DIF. The sorption of CAP and DIF under laboratory conditions was significantly increased with the presence of adjuvant. Soils with high humic acids have strong adsorption capacity and contribute to significant adsorption of CAP and DIF. The half-lives of CAP and DIF tested in fluvo-aquic soil under field conditions were slightly reduced by the adjuvant. Adjuvant reduced the Groundwater Ubiquity Score (GUS) indices of CAP from 1.51 to 1.31, whereas that of DIF from 0.39 to 0.25. Combination between the pesticides and soil molecules can be enhanced, thereby promoting the adsorption and degradation of CAP and DIF in soil, and further reducing their potential to leach into groundwater when 0.1% methylated plant oil adjuvant was mixed and applied.

Dissolved organic matters-enhanced Pb releases from nano- or submicron Pb sulfides and oxides

Diverse lead (Pb) particles possess different ecological risks not only due to their own toxicity differences but also because of different abilities to release toxic dissolved Pb. Dissolved organic matter (DOM) was a key factor influencing dissolution processes of metal particles. However, impacts of DOM on dissolution of different Pb nano- or submicron particles were not known yet. Herein, impacts of DOM on dissolution kinetics of lead sulfide (PbS), lead sulfate (PbSO₄), lead monoxide (PbO), lead tetroxide (Pb₃O₄) and lead dioxide (PbO₂) nano- or submicron particles were firstly investigated taking Pahokee Peat humic acid (PPHA) as an example. Results indicated PPHA improved the suspending stability of Pb particles through electrostatic repulsion, and enhanced releases of dissolved Pb. Final concentration of dissolved Pb was raised by 1.22-8.82 times with PPHA. This was attributed to ligand exchange interactions between PPHA and Pb particles. Theoretical computations indicated that not only sorption or ligand exchange energy, but also numbers of ligands on the surface of particles were key factors governing impacts of PPHA on dissolved Pb. This study provided a new mechanism insight into dissolution behavior of various Pb particles and will be beneficial to their ecological risk assessment.

Adsorption behavior of azole fungicides on polystyrene and polyethylene microplastics

Agricultural plastic films and triazole fungicides are widely used in agricultural production process. Exposure to natural environment, agricultural plastic films will degrade into micron plastic particles, which will adsorb pesticide molecules and may affect their toxicity, biological activity and persistence. The long-term coexistence of microplastics (MPs) and triazole fungicides will bring potential harms to the agricultural ecological environment. Therefore, two kinds of triazole fungicides flusilazole (FLU) and epoxiconazole (EPO) were selected as cases and the adsorption behaviors of them on polystyrene and polyethylene were investigated. A series of factors which could affect the adsorption behavior were evaluated. Specifically, the particle size of MPs could affect its adsorption capacity, and the smaller the particle size, the stronger the adsorption capacity. Moreover, with the increase of pH value from 6.0 to 9.0, the adsorption capacity of MPs to target compounds gradually increased. The effect of ionic strength was evaluated by NaCl, and 0.05% of NaCl was beneficial to the adsorption process, while the continuous increase of NaCl concentration inhibited the adsorption. Oxalic acid and humic acid decreased the adsorption capacity of flusilazole on PE by 15.99-32.00% and PS by 35.02-48.67%, respectively. In addition, compared with the single pesticide system, the adsorption capacity of MPs for flusilazole and epoxiconazole in the binary pesticides system decreased by 36.13-37.93% and 44.36-51.35%, respectively, indicating that competitive adsorption occurred between the two pesticides. Meanwhile, the adsorption process was evaluated by adsorption kinetics and adsorption isotherms and were consistent with pseudo-second-order kinetic model and Freundlich isotherm model, respectively. Finally, several characterization analyses were conducted to investigated the adsorption mechanism, and hydrogen, halogen bonding and hydrophobic interaction proved to play an important role. The study on the adsorption behavior and mechanism of pesticide on MPs was the basis of assessing the risk of joint exposure.

Comparative assessment of individual and mixture chronic toxicity of glyphosate and glufosinate ammonium on amphibian tadpoles: A multibiomarker approach

The aim of the present study was to assess the ecotoxicity of glyphosate and glufosinate ammonium mixtures on amphibian tadpoles and the potential impact of mixture in aquatic ecosystems health. The bonding properties of the mixture based on computational chemistry and an experimental bioassay on morphology, DNA damage and biochemical biomarkers on tadpoles of the common toad Rhinella arenarum were studied. The results of the density functional theory analysis showed trends of the pesticides clustering to form exothermic mixtures, suggesting the likelihood of hot-spots of pesticides in real aquatic systems. In addition, biological effects of individual pesticides and the mixture were studied on tadpoles over 45 days-chronic bioassay. The bioassay consisted of four treatments: a negative control (CO), 2.5 mg L^-1 of a glyphosate-based herbicide (GBH), 2.5 mg L^-1 of a glufosinate ammonium-based herbicide (GABH) and their 50:50 (% v/v) mixture (GBH-GABH). Morphological abnormality rates were significantly higher in all herbicide treatments with respect to CO at 48 h of exposure. Abdominal edema was the most frequent type of abnormality recorded at 48 h, 10 and 45 days of exposure. DNA damage was recorded in all herbicides treatments. Thyroxin increased only in GABH treatment. Acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) significantly increased in GBH treatment, indicating a GBH-neurotoxic effect. Glutathione S-transferase decreased in GABH and GBH-GABH treatments, while catalase decreased in individual GBH and GABH treatments. Overall, teratogenicity, DNA damage, hormonal disruption (T4), and oxidative stress were greater in GABH-treated tadpoles than GBH-treated tadpoles. This study also highlights the robust chemical interaction between the active ingredients of both herbicides, which is reflected on antagonisms in most of analyzed biomarkers, as well as potentiation and additivity in others. Based on our results, the GABH had a higher toxicity than GBH for amphibian tadpoles.

A critical review on interaction of microplastics with organic contaminants in soil and their ecological risks on soil organisms

The pollution of microplastics (MPs) in soil has become a global environmental problem. Due to high sorption capacity and persistence in environment, the MPs exhibit combined effects with organic pollutants in soil, thereby posing a potential risk to soil ecology and human health. However, limited reviews are available on this subject. Therefore, in response to this issue, this review provides an in-depth account of interaction of MPs with organic contaminants in soil and the combined risks to soil environment. The sorption of organic contaminants onto MPs is mainly through hydrophobic and π-π interactions, hydrogen bonding, pore filling and electrostatic and van der Waals forces. The intrinsic characteristics of MPs, organic contaminants and soil are the key factors influencing the sorption of organic pollutants onto MPs. Importantly, the presence of MPs changes the sorption, degradation and transport behaviors of organic contaminants in soil, and affects the toxic effects of organic contaminants on soil organisms including animals, plants and soil microorganisms through synergistic or antagonistic effects. Source control, policy implementation and plastic removal are the main preventive and control measures to reduce soil MPs pollution. Finally, priorities for future research are proposed, such as field investigations of co-pollution, contribution of plastisphere to organic contaminant degradation, and mechanisms of MPs effects on organic contaminant toxicity.

The impacts of nanoplastic toxicity on the accumulation, hormonal regulation and tolerance mechanisms in a potential hyperaccumulator - Lemna minor L

Plastic pollution, which is currently one of the most striking problems of our time, raises concerns about the dispersal of micro and nano-sized plastic particles in ecosystems and their toxic effects on living organisms. This study was designed to reveal the toxic effects of polystyrene nanoplastic (PS NP) exposure on the freshwater macrophyte Lemna minor. In addition, elucidating the interaction of this aquatic plant, which is used extensively in the phytoremediation of water contaminants and wastewater treatment facilities, with nanoplastics will guide the development of remediation techniques. For this purpose, we examined nanoplastic accumulation, oxidative stress markers, photosynthetic efficiency, antioxidant system activity and phytohormonal changes in L. minor leaves subjected to PS NP stress (P-1, 100 mg L^-1; P-2, 200 mg L^-1 PS NP). Our results showed no evidence of PS NP-induced oxidative damage in P-1 group plants, although PS NP accumulation reached 56 µg g^-1 in the leaves. Also, no significant changes in chlorophyll a fluorescence parameters were observed in this group, indicating unaffected photosynthetic efficiency. PS NP exposure triggered the antioxidant system in L. minor plants and resulted in a 3- and 4.6-fold increase in superoxide dismutase (SOD) activity in the P-1 and P-2 groups. On the other hand, high-dose PS NP treatment resulted in insufficient antioxidant activity in the P-2 group and increased hydrogen peroxide (H₂O₂) and lipid peroxidation (TBARS contents) by 25 % and 17 % compared to the control plants. Furthermore, PS NP exposure triggered abscisic acid biosynthesis (two-fold in the P-1 and three-fold in the P-2 group), which is also involved in regulating the stress response. In conclusion, L. minor plants tolerated NP accumulation without growth suppression, oxidative stress damage and limitations in photosynthetic capacity and have the potential to be used in remediation studies of NP-contaminated waters.

Trojan horse in the intestine: A review on the biotoxicity of microplastics combined environmental contaminants

With the reported ability of microplastics (MPs) to act as "Trojan horses" carrying other environmental contaminants, the focus of researches has shifted from their ubiquitous occurrence to interactive toxicity. In this review, we provided the latest knowledge on the processes and mechanisms of interaction between MPs and co-contaminants (heavy metals, persistent organic pollutants, pathogens, nanomaterials and other contaminants) and discussed the influencing factors (environmental conditions and characteristics of polymer and contaminants) that affect the adsorption/desorption process. In addition, the bio-toxicological outcomes of mixtures are elaborated based on the damaging effects on the intestinal barrier. Our review showed that the interaction processes and toxicological outcomes of mixture are complex and variable, and the intestinal barrier should receive more attention as the first line of defensing against MPs and environmental contaminants invasion. Moreover, we pointed out several knowledge gaps in this new research area and suggested directions for future studies in order to understand the multiple factors involved, such as epidemiological assessment, nanoplastics, mechanisms for toxic alteration and the fate of mixtures after desorption.

Interactions of microplastics with organic, inorganic and bio-pollutants and the ecotoxicological effects on terrestrial and aquatic organisms

As emerging contaminants, microplastics (MPs) have attracted global attention. They are a potential risk to organisms, ecosystems and human health. MPs are characterized by small particle sizes, weak photodegradability, and are good environmental carriers. They can physically adsorb or chemically react with organic, inorganic and bio-pollutants to generate complex binary pollutants or change the environmental behaviors of these pollutants. We systematically reviewed the following aspects of MPs: (i) Adsorption of heavy metals and organic pollutants by MPs and the key environmental factors affecting adsorption behaviors; (ii) Enrichment and release of antibiotic resistance genes (ARGs) on MPs and the effects of MPs on ARG migration in the environment; (iii) Formation of "plastisphere" and interactions between MPs and microorganisms; (iv) Ecotoxicological effects of MPs and their co-exposures with other pollutants. Finally, scientific knowledge gaps and future research areas on MPs are summarized, including standardization of study methodologies, ecological effects and human health risks of MPs and their combination with other pollutants.

Competition adsorption of malachite green and rhodamine B on polyethylene and polyvinyl chloride microplastics in aqueous environment

Microplastics (MPs) will cause compound pollution by combining with organic pollutants in the aqueous environment. It is important for environmental protection to study the adsorption mechanism of different MPs for pollutants. In this study, the adsorption behaviors of malachite green (MG) and rhodamine B (RhB) on polyethylene (PE) and polyvinyl chloride (PVC) were studied in single systems and binary systems, separately. The results show that in single system, the adsorptions of between MPs for pollutants (MG and RhB) are more consistent with the pseudo-second-order kinetics and Freundlich isotherm model, the adsorption capacity of both MPs for MG is greater than that of RhB. The adsorption capacities of MG and RhB were 7.68 mg/g and 2.83 mg/g for PVC, 4.52 mg/g and 1.27 mg/g for PE. In the binary system, there exist competitive adsorption between MG and RhB on MPs. And the adsorption capacities of PVC for the two dyes are stronger than those of PE. This is attributed to the strong halogen-hydrogen bond between the two dyes and PVC, and the larger specific surface area of PVC. This study revealed the interaction and competitive adsorption mechanism between binary dyes and MPs, which is of great significance for understanding the interactions between dyes and MPs in the multi-component systems.

The Inhibition of Microcystin Adsorption by Microplastics in the Presence of Algal Organic Matters

Microplastics (MPs) could act as vectors of synthetic chemicals; however, their influence on the adsorption of chemicals of natural origin (for example, MC-LR and intracellular organic matter (IOM), which could be concomitantly released by toxic Microcystis in water) is less understood. Here, we explored the adsorption of MC-LR by polyethylene (PE), polystyrene (PS), and polymethyl methacrylate (PMMA). The results showed that the MPs could adsorb both MC-LR and IOM, with the adsorption capability uniformly following the order of PS, PE, and PMMA. However, in the presence of IOM, the adsorption of MC-LR by PE, PS, and PMMA was reduced by 22.3%, 22.7% and 5.4%, respectively. This is because the benzene structure and the specific surface area of PS facilitate the adsorption of MC-LR and IOM, while the formation of Π-Π bonds favor its interaction with IOM. Consequently, the competition for binding sites between MC-LR and IOM hindered MC-LR adsorption. The C=O in PMMA benefits its conjunction with hydroxyl and carboxyl in the IOM through hydrogen bonding; thus, the adsorption of MC-LR is also inhibited. These findings highlight that the adsorption of chemicals of natural origin by MPs is likely overestimated in the presence of metabolites from the same biota.

DFT insights into the degradation mechanism of carbendazim by hydroxyl radicals in aqueous solution

Advanced oxidation of carbendazim by OH radicals is a central step in its wastewater remediation. However, the understanding of the degradation mechanism of carbendazim has always been a challenge. In this paper, the degradation mechanism of carbendazim by •OH in aqueous solution has been explored using density functional theory (DFT) calculations. On account of the structural and electronic characteristics analysis, the nucleophilic aromatic substitution, dehydrogenation oxidation, and decarboxylation degradation pathways were mainly investigated. These degradation reactions may produce hydroxyl substitution products, oxidized aldehyde and carboxyl products, and decarboxylated carbamic acid products. Computational studies demonstrated that these possible degradation reactions are facile to take place kinetically and have large thermodynamic driving forces, indicating the feasibility of the relevant degradation pathways. Additionally, the ecological risk of carbendazim and its possible degradation products was evaluated, showing that the acute toxicity of degradation products decreases in varying degrees compared with that of carbendazim. The comprehensive mechanistic studies open an avenue for the understanding on the degradation of organic pollutants such as benzimidazole pollutants on molecular level.

Portable metal-organic framework alginate beads for high-sensitivity fluorescence detection and effective removal of residual pesticides in fruits and vegetables

Pesticides have been emerged as major organic pollutants in environment, owing to widely spread and intrinsic high toxicity in agricultural productivity. Herein, we designed and synthesized a practicability and portable metal-organic framework (MOF) based composite beads MOF-alginate-Ca²⁺-polyacrylic acid (kgd-M1@ACPs) consist of biocompatible host material (sodium alginate) and fluorescent center with blue emission (where kgd-M1 stands for {[Cd(tbia)·H₂O]·2H₂O}_n), which was further developed for high-efficiency and naked-eye 2,6-dichloro-4-nitroaniline (DCN) monitoring in fruits and vegetables. Significantly, the kgd-M1@ACPs shows obvious fluorescent quench towards toxic pesticide DCN with a low limit of detection (LOD) of 0.09 μM and high recovery from 98.08 to 104.37%. Moreover, the kgd-M1@ACPs also presents an excellent DCN adsorption ability. This work demonstrates that smart material kgd-M1@ACPs is expected to be a good candidate for detection and removal of DCN in real fruits and vegetables, which will present a broad prospect for monitoring and treating pesticides.

Smart MOF-on-MOF Hydrogel as a Simple Rod-shaped Core for Visual Detection and Effective Removal of Pesticides

The immoderate use of pesticides in the modern agricultural industry has led to the pollution of water resources and ultimately threatens the human body. Herein, two metal-organic frameworks (MOFs), namely {[Zn(tpt)₂ ·2H₂ O]}_n (Zn1) and {[Zn₂ (tpt)₂ (bdc)]}_n (Zn2), (Htpt = 5-[4(1H-1,2,4-triazol-1-yl)]phenyl-2H-tetrazole), respectively, are constructed as smart materials for visual and on-site detection of pesticides and their removal from water. The exposed nitrogen-rich sites and high chemical stability make Zn2 a self-assembly core to further fabricate MOF-on-MOF-sodium alginate (ZIF-8-on-Zn2@SA) composite by wrapping ZIF-8 on the outside surface. Inheriting the excellent fluorescent emission of Zn2, the rod-like ZIF-8-on-Zn2@SA module exhibits naked-eye detection of thiophanate-methyl (TM) in real fruits and vegetables with a broad linear range (10-100 × 10^-6  m), a low limit of detection (LOD = 0.14 × 10^-6  m), and satisfactory recoveries (98.30-102.70%). In addition, carbendazim (CBZ), the metabolite of TM after usage in crops, can be efficiently removed from water by the ZIF-8-on-Zn2@SA (q_max  = 161.8 mg g^-1 ) with a high correlation coefficient (R²  > 0.99). Therefore, the portable ZIF-8-on-Zn2@SA sensing platform presents a promising candidate for monitoring and removal of pesticides, especially suitable for regions with serious pesticide environmental pollution.