Insights into behavior and mechanism of tetracycline adsorption on virgin and soil-exposed microplastics

Investigating the adsorption of organic compounds onto microplastics via experimental, simulation, and prediction methods

Exploring the adsorption of organic compounds onto microplastics (MPs) is of great significance for understanding their environmental fate and evaluating their ecological risks. To date, various techniques, e.g., experiments, simulations, and prediction models, have been utilized for exploring the adsorption of different organic compounds onto MPs. In this review, we systematically introduce the sources of MPs, the interactions between MPs and organic compounds, the factors influencing the adsorption of organic compounds onto MPs, and research advances in investigating the adsorption of organic compounds by microplastics with different techniques. We also point out that the structures of MPs and environmental factors can have distinct effects on the adsorption mechanisms, and the adsorption mechanisms for numerous organic compounds onto MPs are still unclear. Besides, there is a paucity of multi-dimensional models for predicting the adsorption of organic compounds by MPs under different environmental conditions with a single click. We hope that our review can provide insights into the environmental behavior and fate of organic compounds and microplastics, as well as also guiding future research on the adsorption of organic compounds onto microplastics.

Sorption kinetics of metallic and organic contaminants on micro- and nanoplastics: remarkable dependence of the intraparticulate contaminant diffusion coefficient on the particle size and potential role of polymer crystallinity

We developed a mechanistic diffusion model to describe the sorption kinetics of metallic and organic contaminants on nano- and micro-plastics. The framework implements bulk depletion processes, transient fluxes, and fully adaptable particle/water boundary conditions, i.e. not only the typically assumed simple linear Henry regime, which is not applicable to many contaminant-particle situations. Thus, our model represents a flexible and comprehensive theory for the analysis of contaminant sorption kinetics, which goes well beyond the traditional empirical pseudo first or second order kinetic equations. We applied the model to the analysis of a large body of literature data on the equilibrium and kinetic features of sorption of a wide range of contaminants by diverse types and sizes of plastic particles. Results establish the paramount importance of sorption boundary conditions (Henry, Langmuir, or Langmuir-Freundlich) and reveal interesting and often overlooked sorption features that depend on the plastic particle size and the extent to which the target compound is depleted in the bulk medium. The greater degree of polymer crystallinity reported for smaller particles may underlie our findings that the intraparticulate contaminant diffusion coefficient decreases with a decreasing particle size. We establish a universal law to predict the sorption kinetics and diffusion of any compound within any plastic phase, which has far reaching importance across many domains relevant to the environment and human health.

Microplastic interactions with co-existing pollutants in water environments: Synergistic or antagonistic roles on their removal through current remediation technologies

Composite water pollution, caused by microplastics (MPs) and co-occurring pollutants, is an emerging issue that induces synergistic toxicity. Multidimensional interactions occur between MPs and co-existing pollutants in a composite system, which alter the behavior of each component, resulting in unpredictable effects on the treatment processes. However, significant gaps exist in current review papers regarding MP‒pollutant interaction mechanisms and the corresponding synergistic or antagonistic effects on their removal processes. This review comprehensively describes the latest research in composite water pollution caused by MPs and various other pollutants with different compositions and states, systematically discusses their interaction mechanisms, and critically evaluates the impact of co-existing contaminants on the treatment performance of current remediation technologies. Based on current research progress and gaps, opportunities, challenges, and perspectives for future research directions are proposed. This review highlights state-of-the-art research related to composite water pollution caused by MPs and various pollutants, which is expected to inspire new strategies for the effective removal of multiple contaminants from the aquatic environment.

Combined pollution of tetracyclines and microplastics in the aquatic environment: Insights into the occurrence, interaction mechanisms and effects

Tetracyclines, a widely used class of antibiotics, and synthetic plastic products are both prevalent in the environment. When released into water bodies, these pollutants can pose significant risks due to their daily influx into aquatic ecosystems. Microplastics can adsorb tetracyclines, acting as a transport vector that enhances their impact on aquatic species. Understanding the co-exposure effects of microplastics and tetracyclines is crucial. This review comprehensively examines the occurrence and distribution of microplastics and tetracyclines across various environmental contexts. The interactions between these two contaminants are primarily driven by electrostatic interactions, hydrophobic effects, hydrogen bonding, π-π interactions, and others. Factors such as the presence of heavy metals, ions, and dissolved organic matter can influence the adsorption and desorption of tetracyclines onto microplastics. The stability of microplastic-tetracycline complexes is highly dependent on pH conditions. The combined pollution tetracyclines and microplastics leads to negative impacts on marine species. Future research should focus on understanding the adsorption behavior of tetracyclines on microplastics and developing effective treatment techniques for these contaminants in aquatic environments.

Coupling polyethylene microplastics with other pollutants: Exploring their combined effects on plant health and technologies for mitigating toxicity

The presence of microplastics in agricultural soils has raised concerns regarding their potential impacts on ecosystem health and plant growth. The introduction of microplastics into soil can alter its physicochemical properties, leading to adverse effects on plant development. Furthermore, the adsorption capabilities of microplastics may enhance the toxicity of soil pollutants, potentially resulting in detrimental effects on plant life. Large-sized microplastics may become adhered to root surfaces, impeding stomatal function and restricting nutrient uptake. Conversely, smaller microplastics and nano-plastics may be internalized by plants, causing cellular damage and genotoxicity. In addition, the presence of microplastics in soil can indirectly affect plant growth and development by altering the soil environment. Therefore, it is essential to investigate the potential impacts of microplastics on agricultural ecosystems and develop strategies to mitigate their effects. This review describes the adsorption power between polyethylene microplastics and pollutants (heavy metals, polycyclic aromatic hydrocarbons and antibiotics) commonly found in agricultural fields and the factors affecting the adsorption process. Additionally, the direct and indirect effects of microplastics on plants are summarized. Most of the single or combined microplastic contaminants showed negative effects on plant growth, with a few beneficial effects related to the characteristics of the microplastics and environmental factors. Currently microbial action and the application of soil conditioners or plant growth promoters can alleviate the effects of microplastics on plants to a certain extent. In light of the complex nature of soil environments, future research should concentrate on mitigate and control these interactions and the impact of compound pollution on ecosystems.

Response of sedimentary microbial community and antibiotic resistance genes to aged Micro(Nano)plastics exposure under high hydrostatic pressure

Several studies reported that the presence of microplastics (MPs)/nanoplastics (NPs) in marine environments can alter microbial community and function. Yet, the impact of aged MPs/NPs on deep sea sedimentary ecosystems under high hydrostatic pressure remains insufficiently explored. Herein, the sedimentary microbial community composition, co-occurrence network, assembly, and transfer of antibiotic resistance genes (ARGs) in response to aged MPs/NPs were investigated. Compared with the control, NPs addition significantly reduced bacterial alpha diversity (p < 0.05), whereas MPs showed no significant impact (p > 0.05). Moreover, networks under NPs exhibited decreased complexity than that under MPs and the control, including edges, average degree, and the number of keystone. The assembly of the microbial community was primarily governed by stochastic processes, and aged MPs/NPs increased the importance of stochastic processes. Moreover, exposure to MPs/NPs for one month decreased the abundance of antibiotic resistance genes (ARGs) (from 94.8 to 36.2 TPM), while exposure for four months increased the abundance (from 40.6 to 88.1 TPM), and the shift of ARGs in sediment was driven by both functional modules and microbial community. This study is crucial for understanding the stress imposed by aged MPs/NPs on sedimentary ecosystems under high hydrostatic pressure.

Effects of microplastics on 3,5-dichloroaniline adsorption, degradation, bioaccumulation and phytotoxicity in soil-chive systems

Microplastics (MPs) and pesticides are two pollutants of concern in agricultural soils. 3,5-dichloroaniline (3,5-DCA), a highly toxic metabolite of dicarboximide fungicides, commonly co-exists with MPs and poses a risk to the environment and food safety. Batch adsorption and soil incubation experiments were employed to investigate the effects of polyethylene (PE) and polylactic acid (PLA) MPs on the environmental behavior of 3,5-DCA in soil. Chive (Allium ascalonicum) was used as the experimental plant, a pot experiment was conducted to examine the effects of individual or combined exposure to MPs and 3,5-DCA on plant 3,5-DCA bioaccumulation, growth characteristics, and phytotoxicity. The results showed that PE- and PLA-MPs increased the adsorption capacity of soil to 3,5-DCA and prolonged the degradation half-life of 3,5-DCA by 6.24 and 16.07 d, respectively. Two MPs partially alleviated the negative effects of 3,5-DCA on the root length and fresh weight of chives, while PE-MPs had a positive and dose-dependent impact on the contents of photosynthetic pigment in chive leaves. Co-exposure to 3,5-DCA and MPs increased residues of 3,5-DCA in soil and chive roots but had no significant effect on 3,5-DCA residues in chive stems or leaves. Moreover, 3,5-DCA residues in PLA-MP soil were consistently higher than those in PE-MP soil. Conclusively, MPs altered the 3,5-DCA adsorption and degradation behavior in soil, as well as its bioaccumulation in chives. Co-exposure to MPs and 3,5-DCA had dose-dependent and MP-specific effects on chive plant development and phytotoxicity.

Deciphering the role of nonylphenol adsorption in soil by microplastics with different polarities and ageing processes

In the soil environment, microplastics (MPs) commonly coexist with organic pollutants such as nonylphenol (NP), affecting the migration of NP through adsorption/desorption. However, few studies have focused on the interaction between NP and MPs in soil, especially for MPs of different types and ageing characteristics. In this study, non-polar polypropylene (PP) and polar polyamide (PA) MPs were aged either photochemically (144 h) or within soil (60 days), then used to determine the effect of 5 % MPs on the adsorption behaviour of NP (0.1-4.0 mg/L) in soil. Results showed that both ageing processes significantly promoted the conversion of -CH3 groups to C-O and CO on the surface of PPMPs, while PAMPs exhibited amide groups changes and a reduction in average particle size due to ageing. Additionally, both ageing processes promoted the adsorption of NP by soil containing PPMPs, due to an increase in oxygen-containing functional groups and specific surface area. In contrast, the NP adsorption capacity of soil containing PAMPs decreased by 15.4 % following photochemical ageing due to hydrolysis of amide groups, but increased by 21.15 % after soil ageing due to reorganization of amide groups, respectively. The soil-PAMPs systems exhibited a stronger affinity for NP compared to the soil-PPMPs systems, which was primarily attributed to the dominant role of hydrogen bonding. NP was found to be distributed mainly on soil particles in the soil-PPMPs systems, while it tended to be adsorbed by MPs in the soil-PAMPs systems, especially in the soil aged MPs system. This study provides a comprehensive analysis of the complex effects of MPs on coexisting pollutants in soil environments, highlighting the effect of MP characteristics on the adsorption of organic pollutants, which is essential for understanding the transport behaviour of organic pollutants.

Effects of microplastics on dissipation of oxytetracycline and its relevant resistance genes in soil without and with Serratia marcescens: Comparison between biodegradable and conventional microplastics

The biodegradable (polybutylene adipate terephthalate: PBAT) and conventional (polyethylene: PE) microplastics (MPs) at 0.5 %, 1 %, and 2 % dosages (w/w) were added into soils with and without Serratia marcescens ZY01 (ZY01, a tet-host strain) to understand their different effects on the dissipation of oxytetracycline (OTC) and tet. The results showed that the dosages of PBAT MP exhibited different inhibition degrees of OTC biodegradation in soils regardless of ZY01, while the dosages of PE MP did not change the enhancement degree of OTC biodegradation in soils without ZY01. These differences were due to the higher adsorption capacity of OTC on PBAT MP and the stronger toxicity of PBAT MP to microorganisms. Besides soil organic matter, pH and total phosphorus were important factors regulating specific tet-host bacteria in soils with MPs (e.g., the nitrogen-cycling bacteria Steroidobacter and Nitrospira) and MPs + ZY01 (e.g., the phosphorus-cycling bacteria Saccharimonadales and Haliangium), respectively. Regardless of ZY01, a stronger selective harboring of tet-host bacteria in PE MP treatments than PBAT MP treatments was observed at the MP dosage of 1 % (w/w), while the opposite trend was true at the MP dosages of 0.5 % and 2 % (w/w). Some specific genera belonging to Actinobacteriota strongly associated with the class 1 integron-integrase gene (intI1), playing a critical role in the horizontal gene transfer of tet in soils especially for the co-existence of MPs and ZY01. This study will be helpful for understanding on how biodegradable and conventional MPs as hotspots affect the environmental behavior of antibiotics and ARGs in soil.

A cutting-edge approach to remove arsenic contents from ground water via sulfur doped copper ferrites (S-CuFe2O4) †

Pure water is necessary for healthy life; however natural ground water has many toxic metals. Before drinking, it must be free from toxic metals that commonly causes cancer. For example, arsenic is hazardous element but unfortunately it is naturally present in ground water. Due to its high solubility, removal of arsenic from water is not easy. In recent decades, presence of arsenic in ground water has been reported in many areas of Pakistan. Purpose of current project is to estimate and eliminate arsenic contents from the ground drinking water of Tribal Belt of DG Khan. For the comprehensive survey, 200 water samples were collected from the areas where large proportion of ground water is being consumed for drinking. In this work, relatively cheaper and effective adsorbent namely S‒CuFe2O4 have been synthesized for the quick removal of arsenic. Arsenic contents were converted to the arsenomolybdate complex (AMC) and this complex was then adsorbed on S‒CuFe2O4. Morphology and chemical characteristics have been evaluated via XRD, SEM, FT-IR, Raman, TGA, EDX, AFM and XPS techniques. Additionally, various kinetic models were employed to confirm and validate the adsorption phenomena. Based on the results and assessment, it has been concluded that 1.5 g of aforementioned adsorbent is adequate to deliver 432 gal of arsenic free water.

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).

Characteristics of tetracycline antibiotic resistance gene enrichment and migration in soil-plant system

Tetracycline Resistance Genes (TRGs) have received widespread attention in recent years, as they are a novel environmental pollutant that can rapidly accumulate and migrate in soil plant systems through horizontal gene transfer (HGT), posing a potential threat to food safety and public health. This article systematically reviews the pollution sources, enrichment, and migration characteristics of TRGs in soil. The main sources of TRGs include livestock manure and contaminated wastewater, especially in intensive farming environments where TRGs pollution is more severe. In soil, TRGs diffuse horizontally between bacteria and migrate to plant tissues through mechanisms such as plasmid conjugation, integron mediation, and phage transduction. The migration of TRGs is not limited to the soil interior, and increasing evidence suggests that they can also enter the plant system through plant root absorption and the HGT pathway of endophytic bacteria, ultimately accumulating in plant roots, stems, leaves, fruits, and other parts. This process has a direct impact on human health, especially when TRGs are found in crops such as vegetables, which may be transmitted to the human body through the food chain. In addition, this article also deeply analyzed various factors that affect the migration of TRGs, including the residual level of tetracycline in soil, the type and concentration of microorganisms, heavy metal pollution, and the presence of new pollutants such as microplastics. These factors significantly affect the enrichment rate and migration mode of TRGs in soil. In addition, two technologies that can effectively eliminate TRGs in livestock breeding environments were introduced, providing reference for healthy agricultural production. The article concludes by summarizing the shortcomings of current research on TRGs, particularly the limited understanding of TRG migration pathways and their impact mechanisms. Future research should focus on revealing the migration mechanisms of TRGs in soil plant systems and developing effective control and governance measures to reduce the environmental transmission risks of TRGs and ensure the safety of ecosystems and human health.

Investigating the impact of microplastics on triphenyl phosphate adsorption in soil: Insights into environmental factors and soil properties

Microplastics (MPs) pose significant environmental pollution problems owing to their diverse properties such as various shapes, sizes, compositions, surface features, and levels of degradation. Moreover, their interactions with toxic chemicals and aging processes add complexity to environmental research. This study investigated the adsorption of triphenyl phosphate (TPhP) in soil-only, MP-only, and soil-MP simulated environments under different conditions. The experiment involved three phases: initial exposure to a pH of 5.5 under fluorescent light, subsequent introduction of ultraviolet (UV) radiation, and pH adjustment to 4.0 and 7.0, while maintaining UV exposure, each lasting 7 days. The study found that environmental factors affected TPhP sorption capacity, with higher adsorption observed under UV radiation and acidic conditions. In contrast, the MP-only systems showed no clear trend for TPhP adsorption, suggesting kinetic limitations. When MPs were added to the soil, the adsorption dynamics were altered, with varying adsorption capacities observed for different MP polymers under different aging conditions. ATR-FTIR spectroscopy, micro-Raman spectroscopy, and water contact angle measurements suggested potential photooxidation processes and changes in the surface hydrophobicity of the MPs subjected to simulated environmental conditions. This study provides valuable insights into the interplay between soil properties, MP characteristics, and environmental factors in determining TPhP sorption dynamics in soil-MP environments.

Effect of particle density on microplastics transport in artificial and natural porous media

The occurrence and persistence of microplastics (MPs) in natural environments are of increasing concern. Along with this, the transport of MPs in sediments has been investigated mainly focusing on the effect of plastic size and shape, media size effect, and solution chemistry. Yet, the influence of particle density is only partially understood. Therefore, column experiments on the transport of variably buoyant MPs in saturated natural sediments and glass beads were conducted, and transport parameters were quantified using a two-site kinetic transport model with a depth-dependent blocking function (the amount of retained MPs does not decrease at a constant rate with increasing depth, the majority of MPs were retained near the column inlet). Neutral, sinking, and buoyant MPs within the same size range were selected, with stable water isotope applied as conservative tracer to explore water and MP movement in the tested sediments. The results showed that 95.5 ± 1.4% of sinking MPs remained in columns packed with gravel, followed by buoyant and neutral MPs, thus indicating that particle density does affect MP mobility. Similar recovered amounts of MPs were found in columns packed with glass beads, indicating that tested sediment types do not affect the deposition behavior of MPs. The breakthrough curves of MPs were accurately described by the selected model. However, the simulated retention profiles overestimated the observed MP amount in layers closest to the column inlet. The coupled experimental and modeled results suggest an enhanced retention of sinking MPs, while neutrally and buoyant MPs exhibit a higher mobility in comparison. Thus, neutral or buoyant MPs can potentially pose a higher contamination risk to subsurface porous media environments compared to sinking MPs. Discrepancies between observed and simulated retention profiles indicate that future model development is needed for advancing the MP deposition as affected by particle density.

Bioelectrochemical remediation of soil antibiotic and antibiotic resistance gene pollution: Key factors and solution strategies

In recent years, owing to the overuse and improper handling of antibiotics, soil antibiotic pollution has become increasingly serious and an environmental issue of global concern. It affects the quality and ecological balance of the soil and allows the spread of antibiotic resistance genes (ARGs), which threatens the health of all people. As a promising soil remediation technology, bioelectrochemical systems (BES) are superior to traditional technologies because of their simple operation, self-sustaining operation, easy control characteristics, and use of the metabolic processes of microorganisms and electrochemical redox reactions. Moreover, they effectively remediate antibiotic contaminants in soil. This review explores the application of BES remediation mechanisms in the treatment of antibiotic contamination in soil in detail. The advantages of BES restoration are highlighted, including the effective removal of antibiotics from the soil and the prevention of the spread of ARGs. Additionally, the critical roles played by microbial communities in the remediation process and the primary parameters influencing the remediation effect of BES were clarified. This study explores several strategies to improve the BES repair efficiency, such as adjusting the reactor structure, improving the electrode materials, applying additives, and using coupling systems. Finally, this review discusses the current limitations and future development prospects, and how to improve its performance and promote its practical applications. In summary, this study aimed to provide a reference for better strategies for BES to effectively remediate soil antibiotic contamination.

Effects of micro-nano plastics on the environmental biogeochemical cycle of nitrogen: A comprehensive review

Micro-nano plastics (MNPs; size <5 mm), ubiquitous and emerging pollutants, accumulated in the natural environment through various sources, and are likely to interact with nutrients, thereby influencing their biogeochemical cycle. Increasing scientific evidences reveal that MNPs can affect nitrogen (N) cycle processes by affecting biotopes and organisms in the environmental matrix and MNPs biofilms, thus plays a crucial role in nitrous oxide (N2O) and ammonia (NH3) emission. Yet, the mechanism and key processes behind this have not been systematically reviewed in natural environments. In this review, we systematically summarize the effects of MNPs on N transformation in terrestrial, aquatic, and atmospheric ecosystems. The effects of MNPs properties on N content, composition, and function of the microbial community, enzyme activity, gene abundance and plant N uptake in different environmental conditions has been briefly discussed. The review highlights the significant potential of MNPs to alter the properties of the environmental matrix, microbes and plant or animal physiology, resulting in changes in N uptake and metabolic efficiency in plants, thereby inhibiting organic nitrogen (ON) formation and reducing N bioavailability, or altering NH3 emissions from animal sources. The faster the decomposition of plastics, the more intense the perturbation of MNPs to organisms in the natural ecosystem. Findings of this provide a more comprehensive analysis and research directions to the environmentalists, policy makers, water resources planners & managers, biologists, and biotechnologists to do integrate approaches to reach the practical engineering solutions which will further diminish the long-term ecological and climatic risks.

Influence of microplastics on the availability of antibiotics in soils

Microplastics (MPs) and antibiotics, as two major types of emerging pollutants, inevitably coexist in the soil environment due to agricultural film residue, sewage irrigation and sludge application. However, the impact of MPs on antibiotic availability in soils with varying characteristics has not been extensively studied. Therefore, in this study, an interference experiment was conducted using three types of MPs (polyethylene (PE), polyvinyl chloride (PVC) and polypropylene (PP)) in red soil, paddy soil and cinnamon soil. The available antibiotics in soils were evaluated using diffusive gradients in thin-films (DGT). Results showed that MPs had a significant impact on the amount of antibiotics adsorbed on soil solid (Cs) by providing additional binding sites or altering soil characteristics (e.g., pH and dissolved organic carbon). The most significant effects on Cs were observed in cinnamon soil, and the Cs values were dependent on concentration of MPs. The available antibiotics, as measured by DGT significantly decreased after the addition of MPs. This decrease was influenced by the soil characteristics. However, the concentration of antibiotics in soil solutions (Cd) was only slightly impacted by MPs. Therefore, the influence of MPs on the migration of antibiotics was reflected by their impact on the soil/water partition coefficient (Kd), while the resupply ability (R) from the soil solid phase was less influential. Moreover, the dosage of MPs had a significant effect on the availability of antibiotics in CS by promoting the adsorption of antibiotics on the solid phase, while in RS and PS, the soil properties played a dominate role in the changes in antibiotic availability after MP addition. These results indicate that the impact of MPs on available antibiotics mainly depends on soil properties. In addition, DGT measurement is more sensitive than soil solution to investigate the effects of coexisting pollutants on the behavior of antibiotics in soil.

High-sensitive determination of tetracycline antibiotics adsorbed on microplastics in mariculture water using pre-COF/monolith composite-based in-tube solid phase microextraction on-line coupled to HPLC-MS/MS

Microplastics (MPs) act as carriers for organic pollutants (e.g. antibiotics) and microorganisms (e.g. bacteria) in waters, leading to the proliferation of antibiotic resistance genes. Moreover, the antibiotics adsorbed on MPs may exacerbate this process. For further research, it is necessary to understand the types and amounts of antibiotics adsorbed on MPs. However, due to the heavy work of MPs collection and sample pretreatment, there is a lack of analytical methods and relevant data. In this study, an in-tube solid phase microextraction (IT-SPME) on-line coupled to HPLC-MS/MS method based on amorphous precursor polymer of three-dimensional covalent organic frameworks/monolith-based composite adsorbent was developed, which could efficiently capture, enrich and analyze tetracycline (TCs) antibiotics. Under the optimal extraction parameters, the developed method was capable of detecting TCs at levels as low as 0.48-1.76 pg. This method was applied to analyze the TCs adsorbed on MPs of different particle sizes in mariculture water for the first time, requiring a minimum amount of MPs of only 1 mg. Furthermore, it was observed that there could be an antagonistic relationship between algal biofilm and TCs loaded on MPs. This approach could open up new possibilities for analyzing pollutants on MPs and support deeper research on MPs.

Insight into the key factors and mechanism of excellent tetracycline adsorption on amorphous cobalt carbonate nanosheets

The extensive use of tetracyclines (TCs) has led to their widespread distribution in the environment, causing serious harm to ecosystems because of their toxicity and resistance to decomposition. Adsorption is presently the principal approach to dispose of TCs, and the development of excellent adsorbents is crucial to TC removal. Herein, a novel amorphous cobalt carbonate hydroxide (ACCH) was successfully prepared by a one-step solvothermal method, which was identified as Co(CO3)0·63(OH)0.74·0.07H2O. The ultimate adsorption capacity of ACCH for TC reaches 2746 mg g-1, and the excellent adsorption performance can be maintained over a wide pH (3.0-11.0) and temperature (10-70 °C) range. Moreover, ACCH also exhibits a wonderful adsorption performance for other organic contaminants, such as ciprofloxacin and Rhodamine B. The TC adsorption process can be reasonably described by the pseudo-second-order kinetic model, intraparticle model and Langmuir isothermal model. The experimental results in this work suggest that the excellent adsorption performance of ACCH is ascribed to the large specific surface area, alkaline characteristics and numerous functional groups of ACCH. Accordingly, this work provides a promising strategy for the development of highly-efficient adsorbents and demonstrates their application prospects in environmental remediation.

Experimental and simulated microplastics transport in saturated natural sediments: Impact of grain size and particle size

Microplastics (MPs) present in terrestrial environments show potential leaching risk to deeper soil layers and aquifer systems, which threaten soil health and drinking water supply. However, little is known about the environmental fate of MPs in natural sediments. To examine the MPs transport mechanisms in natural sediments, column experiments were conducted using different natural sediments and MPs (10-150 µm) with conservative tracer. Particle breakthrough curves (BTCs) and retention profiles (RPs) were numerically interpreted in HYDRUS-1D using three different models to identify the most plausible deposition mechanism of MPs. Results show that the retention efficiency for a given particle size increased with decreasing grain size, and RPs exacerbated their hyper-exponential shape in finer sediments. Furthermore, the amounts of MPs present in the effluent increased to over 85 % as MPs size decreased to 10-20 µm in both gravel and coarse sand columns, while all larger MPs (125-150 µm) were retained in the coarse sand column. The modeling results suggested that the blocking mechanism becomes more important with increasing particle sizes. In particular, the attachment-detachment without blocking was the most suited parameterization to interpret the movement of small MPs, while a depth-dependent blocking approach was necessary to adequately describe the fate of larger particles.

Microplastics strengthen nitrogen retention by intensifying nitrogen limitation in mangrove ecosystem sediments

Mangrove wetlands are hotspots of the global nitrogen (N) cycle and important sinks of microplastics (MPs) due to their ecotone location between terrestrial and marine ecosystems. However, the effects of MPs on N cycle processes in mangrove ecosystems are still poorly understood. Thus, the present study assessed the impacts by adding MPs to mangrove sediments in a microcosm incubation experiment. The results showed that MPs increased dissolved organic carbon and nitrate but reduced ammonium contents in the sediments. MPs increased C:N stoichiometric and N:C-acquiring enzymatic ratios, indicating an intensified N limitation in mangrove sediments following exposure of MPs. MPs decreased microbial community diversity and shifted sediment microbial communities from r- to K-strategists, consistent with the intensified N limitation. In response, dissimilatory nitrate reduction to ammonium (DNRA) rates increased while nitrous oxide (N2O) production reduced suggesting more efficient N utilization in MPs treatments. The MPs with heteroatoms such as PLA- and PVC-MPs, increased DNRA rates by 67.5-78.7%, exhibiting a stronger impact than PE-MPs. The variation partitioning analysis revealed that the variances of DNRA rates and N2O production could be attributed to synergistic effects of physicochemical properties, nutrient limitation, and microbial community in mangrove sediments. Overall, this study provides pertinent insights into the impacts of MPs as a new carbon source on nutrient limitation and N turnover in mangrove ecosystems.

Adsorption of azoxystrobin and pyraclostrobin onto degradable and non-degradable microplastics: Performance and mechanism

Microplastics (MPs) exist after agricultural operations and thus present potential hazards to the environment and human health. However, the ecological risks posed by MPs carrying pesticides remain unclear. In this study, the adsorption and desorption behaviors of two pesticides, azoxystrobin and pyraclostrobin, on degradable and non-degradable MPs of poly(butylene adipate-co-terephthalate) (PBAT) and polyethylene (PE) were compared before and after UV aging. Additionally, the bioaccessibility of MPs carrying pesticides within a condition simulating gastrointestinal fluids was evaluated. The results showed that, after UV aging, the adsorption capacity of PBAT for pesticides decreased, while that of PE increased. Moreover, PBAT possessed higher adsorption ability towards both the pesticides due to its higher specific surface area, pore volume, contact angle, and lower crystallinity, as well as stronger van der Waals forces, electrostatic interactions, and hydrogen bonding indicated by theoretical calculation. Bioaccessibility experiments showed that azoxystrobin and pyraclostrobin had a higher risk of desorption from PBAT than PE, which is mainly dependent on the LogKow of pesticides according to the random forest analysis. In brief, the study highlights the potential risks of degradable MPs carrying pesticides to human health and the ecosystem, especially when compared to their non-degradable counterparts, manifesting that the ecological risk posed by degradable MPs should not be ignored.

Micro/nanoplastics: Critical review of their impacts on plants, interactions with other contaminants (antibiotics, heavy metals, and polycyclic aromatic hydrocarbons), and management strategies

Microplastic/nanoplastics (MPs/NPs) contamination is not only emerging threat to the agricultural system but also constitute global hazard to the environment worldwide. Recent review articles have addressed the environmental distribution of MPs/NPs and their single-exposure phytotoxicity in various plant species. However, the mechanisms of MPs/NPs-induced phytotoxicity in conjunction with that of other contaminants remain unknown, and there is a need for strategies to ameliorate such phytotoxicity. To address this, we comprehensively review the sources of MPs/NPs, their uptake by and effects on various plant species, and their phytotoxicity in conjunction with antibiotics, heavy metals, polycyclic aromatic hydrocarbons (PAHs), and other toxicants. We examine mechanisms to ameliorate MP/NP-induced phytotoxicity, including the use of phytohormones, biochar, and other plant-growth regulators. We discuss the effects of MPs/NPs -induced phytotoxicity in terms of its ability to inhibit plant growth and photosynthesis, disrupt nutrient metabolism, inhibit seed germination, promote oxidative stress, alter the antioxidant defense system, and induce genotoxicity. This review summarizes the novel strategies for mitigating MPs/NPs phytotoxicity, presents recent advances, and highlights research gaps, providing a foundation for future studies aimed at overcoming the emerging problem of MPs/NPs phytotoxicity in edible crops.

Long-term aged fibrous polypropylene microplastics promotes nitrous oxide, carbon dioxide, and methane emissions from a coastal wetland soil

Microplastics (MPs) has been suggested that it can greatly affect soil greenhouse gases (GHGs) emissions via altering soil physical, chemical, and biological properties. However, the difference in GHGs emissions, especially for those from coastal wetland soils, between varied aged MPs was rarely explored and the underlying mechanisms of GHGs emissions affected by the aged MPs were poorly understood. Therefore, the implications of fibrous polypropylene MPs (FPP-MPs) exposure on N2O, CO2, and CH4 emissions were examined by a 60-day soil incubation experiment. Compared with the control, the additions of un-aged FPP-MPs with both two rates (0.2 and 2 %) and aged FPP-MPs with a low rate (0.2 %) showed an insignificant effect on N2O emission, while the aged FPP-MPs added with a high rate (2 %) resulted in a remarkably increase in N2O emission, especially for those of the 30-day-aged FPP-MPs. A significant increase in CO2 emission was only observed in the 30-day-aged FPP-MPs treatments, compared with the control, and a higher addition rate produced a higher increase of CO2 emission. Regarding CH4 emission, it was significantly increased by adding aged FPP-MPs, and a longer aging period or/and a higher addition rate generated a higher degree of promotion of CH4 emission. However, compared with the CO2 emission, the quantity of CH4 emission was extremely low. These increased GHGs emissions can be ascribed to the improvements in soil physical structure and other chemical properties (e.g., pH and contents of soil organic matter and dissolved organic carbon) and enhancements in the abundances of denitrification- and carbon mineralization-related microorganisms. Overall, our results highlight the risk of elevated GHGs emissions from the soil polluted with 30-day-aged FPP-MPs, which should not be ignored as long-term aged FPP-MPs continue to increase in coastal wetland soils.

Recycling waste iron-rich algal flocs as cost-effective biochar activator for heterogeneous Fenton-like reaction towards tetracycline degradation: Important role of iron species and moderately defective structures

Harvesting aquatic harmful algal blooms (HABs) and reusing them is a promising way for antibiotic degradation. Herein, a novel iron-rich biochar (Fe-ABC), derived from algal biomass harvested by magnetic coagulation, was successfully designed and fabricated as activator for heterogeneous Fenton-like reaction. The modification methods and pyrolysis temperatures (400-800 °C) were optimized to enhance the formation of rich iron species and moderately defective structure, yielding Fe-ABC-600 with enhanced electron transfer and H2O2 activation capability. Thus, Fe-ABC-600 exhibited superior removal efficiency (95.33%) on tetracycline (TC), where the presence of multiple iron species (Fe3+, Fe2+ and Fe4+) and moderately defective structure accelerating the Fenton-like oxidation. The concentration of leaching Fe after each reaction was all below 0.74 mg/L in five cycles, ensuring the sustained degradation. And •OH was proved to be the major radical contributing to the degradation of TC, as well as the direct electron transfer mechanism together, in which the CO acted as electron regulator and electron donor. Fe-ABC as a cost-effective catalyst has notable application potentials in TC removal from wastewater owing to its remarkable advantages of high resource utilization, enhanced catalytic property, high ecological safe, notable TC degradation efficiency, low cost and environmental-friendliness.

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.

Predicting aqueous sorption of organic pollutants on microplastics with machine learning

Microplastics (MPs) are ubiquitously distributed in freshwater systems and they can determine the environmental fate of organic pollutants (OPs) via sorption interaction. However, the diverse physicochemical properties of MPs and the wide range of OP species make a deeper understanding of sorption mechanisms challenging. Traditional isotherm-based sorption models are limited in their universality since they normally only consider the nature and characteristics of either sorbents or sorbates individually. Therefore, only specific equilibrium concentrations or specific sorption isotherms can be used to predict sorption. To systematically evaluate and predict OP sorption under the influence of both MPs and OPs properties, we collected 475 sorption data from peer-reviewed publications and developed a poly-parameter-linear-free-energy-relationship-embedded machine learning method to analyze the collected sorption datasets. Models of different algorithms were compared, and the genetic algorithm and support vector machine hybrid model displayed the best prediction performance (R2 of 0.93 and root-mean-square-error of 0.07). Finally, comparison results of three feature importance analysis tools (forward step wise method, Shapley method, and global sensitivity analysis) showed that chemical properties of MPs, excess molar refraction, and hydrogen-bonding interaction of OPs contribute the most to sorption, reflecting the dominant sorption mechanisms of hydrophobic partitioning, hydrogen bond formation, and π-π interaction, respectively. This study presents a novel sorbate-sorbent-based ML model with a wide applicability to expand our capacity in understanding the complicated process and mechanism of OP sorption on MPs.

Effects of incorporating Mn into goethite on adsorption of dissolved organic matter and potentially toxic elements in soil: Isotherms, kinetics, and mechanisms

Goethite is ubiquitous in the environment and plays key role in preserving dissolved organic matter (DOM) and deactivating potentially toxic elements (PTEs) by adsorbing DOM and PTEs. Various non-Fe metals are usually incorporated into natural goethite, substituting Fe in the goethite structure, which dramatically influence the physico-chemical properties and adsorption behavior of the goethite. In the present study, adsorption of DOM and Pb(II) on Mn-substituted goethite samples was investigated. The results displayed that the specific surface area (SSA) of mineral samples increased by 67.6% as the incorporation of Mn for Fe, from 25.71 m2 g-1 for pure goethite to 43.09 m2 g-1for Mn-goethite. Besides, the Mn substitution caused more hydroxyl groups and relatively fewer positive charges on mineral surface, and Mn in the Mn-goethite samples was predominantly present as Mn(III). The amount of DOM adsorbed to per unit mass of goethite was increased as Mn content increased, which was attributed to Mn incorporation increasing the SSA of mineral samples. However, the SSA-normalized absorption capacity for goethite to DOM was decreased by Mn because Mn substitution decreased the number of positive charges of mineral samples, which weakened the electrostatic attraction between DOM and the minerals. The amount of Pb(II) adsorbed to per unit mass of goethite was increased by Mn substitution, and the amount of Pb(II) adsorbed to per unit SSA of goethite increased as the amount of Mn substitution increased, indicating that the increased capacity for adsorbing Pb was not only caused by the SSA increasing but also by there were more surface hydroxyl groups on the Mn-goethite than pure goethite and Pb(II) preferentially adsorbed to Mn sites on the Mn-goethite. The present study results showed that Mn-goethite could be used to sequester DOM and remediate soil contaminated with PTEs because Mn-goethite has a high adsorption capacity and is environmentally benign.

Co-existence of polyethylene microplastics and tetracycline on soil microbial community and ARGs

Microplastics are plastic particles with particle size less than 5 mm in the environment. As an emerging organic pollutant, the presence of microplastics in the soil environment has been widely noticed. Secondly, due to the overuse of antibiotics, a large amount of antibiotics that cannot be fully absorbed by humans and livestock enter the soil environment in the form of urine or manure, making the soil suffer from serious antibiotic contamination problems. To address the environmental problems of microplastics and antibiotic contamination in soil, this study was conducted to investigate the effects of PE microplastics on antibiotic degradation, microbial community characteristics and ARGs in tetracycline-contaminated soils. The results showed that the addition of PE microplastics inhibited the degradation of tetracycline, and significantly increased the organic carbon content and decreased the neutral phosphatase activity. The addition of PE microplastics significantly reduced the alpha diversity of soil microbial community. Compared to the single tetracycline contamination. In addition, combined contamination with PE microplastics and tetracycline significantly affected bacterial genera such as Aeromicrobium, Rhodococcus, Mycobacterium and Intrasporangium. Metagenome sequencing studies revealed that the addition of PE microplastics inhibited the dissipation of ARGs in tetracycline-contaminated soils. There were strong positive correlations between Multidrug, Aminoglycoside and Clycopeptide resistance genes and Chloroflexi and Proteobacteria in tetracycline contaminated soils, and there was a strong positive correlation between Aminoglycoside resistance genes and Actinobacteria in combined contamination of PE microplastics and tetracycline. This study will provide some data support for the current environmental risk assessment of the coexistence of multiple contaminants in soil.

Effect of polyethylene, polyamide, and polylactic acid microplastics on Cr accumulation and toxicity to cucumber (Cucumis sativus L.) in hydroponics

Microplastics (MPs) in farmland soil may affect the environmental fate and toxicity of heavy metals; however, how non-biodegradable and biodegradable MPs change the accumulation and phytotoxicity of Cr(VI) to the plants is still unknown. In this study, we explored the impacts of Cr(VI) concentrations (0, 20, 50, 100, 200, and 500 μmol/L), MP types (polyethylene (PE), polyamide (PA), and polylactic acid (PLA)), sizes (13, 48, and 500 µm), and concentrations (40, 200, and 1000 mg/L) on the Cr accumulation and toxicity to cucumber (Cucumis sativus L.) under hydroponic conditions for 14 days. The results show that the presence of PE-MPs promoted the Cr accumulation in root by 8-39.8%. However, PA-MPs inhibited the Cr accumulation in the whole plant under less than 100 μmol/L Cr(VI). Notably, 1000 mg/L PA-MPs significantly reduced Cr accumulation in root and stem by 44.70% and 48.20%, respectively. Moreover, PE-MPs and PLA-MPs reduced the chlorophyll content and slowed down the growth of seedlings, while PA-MPs were beneficial to the growth of cucumber under 50-500 μmol/L Cr(VI) treatments, increasing the biomass by 20.99-189.99%. Furthermore, PE-MPs enhanced the content of MDA, especially under 500 μmol/L Cr(VI) concentration by 27.39%; however, the addition of PA-MPs and PLA-MPs slightly enhanced the enzyme activities including superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT). Significantly, 1000 mg/L PA-MPs promoted biomass and reduced MDA content compared the control due to their high Cr(VI) adsorption efficiency. Thus, MP type, especially PE-MPs, mainly determined the Cr accumulation and phytotoxicity, which was attributed to the various adsorption capacities of MPs to Cr(VI).

Antibiotic resistance genes proliferation under anaerobic degradation of polylactic acid and polyhydroxy butyrate bioplastics

As the global concern over plastic pollution grows, efforts are underway to find environmentally friendly alternatives to traditional plastics. Bioplastics are being extensively researched and developed as a possible solution. This study compared the impact of two bioplastics, polylactic acid (PLA) and polyhydroxy butyrate (PHB), on the proliferation of antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs) during anaerobic digestion (AD). Both bioplastics (250-500 particles) could be degraded to a certain extent over 79 days, as indicated by higher methane production than the control without bioplastic particles. The PHB 500 reactor showed the highest methane yield along with the highest biodegradation efficiency (91 %) than other reactors amended with PHB and PLA particles. The highest ARG and MGE abundances were also observed in PLA 500, and the lowest ARG abundance was in PLA 250. Conversely, PHB reactors showed a relatively lower ARG abundance than the control. The correlation analysis suggested that most ARGs were positively correlated with PLA and negatively correlated with PHB (except for tetA, tetB, and tetX). Moreover, a correlation between MGEs and ARGs in PLA and PHB reactors was revealed by correlation analysis. These results show that AD responds differently to the different types/levels of bioplastics, which can ultimately influence the behavior of ARG proliferation. Thus, bioplastics may also pose a potential risk for spreading antibiotic resistance. These findings can be used as a basis for setting environmental standards for bioplastics and creating monitoring and control measures to prevent potential negative impacts on public health.

Desorption behavior of antibiotics by microplastics (tire wear particles) in simulated gastrointestinal fluids

Microplastics (MPs) are widely distributed throughout the environment. Upon ingesting MPs, the pollutants that they carry are then desorbed into organisms. This results in the accumulation of various chemicals within the organism. This study systematically examined the mechanism of antibiotic desorption using tire wear particles (TWP) as a carrier of antibiotics in simulated human gastrointestinal fluid and fish intestinal fluid. The findings of this study revealed the formation of cracks, pores, and depressions on the surface of photoaged TWP in an aquatic environment, as well as additional adsorption sites that are more favorable for the attachment of pollutants. Furthermore, the simulated human gastric fluid had a higher desorption rate than that of the fish intestinal fluid. The competition for TWP adsorption sites in the gastrointestinal fluid and the potential dissolution of antibiotics were the primary drivers of the increase in the desorption rate. The desorption rate in the simulated human gastrointestinal fluid was greater than that in the simulated fish intestinal fluid due to the composition of the gastrointestinal fluid. However, the carrying of pollutants by MPs poses a potential threat to human health. This study improves our understanding of TWP toxicity and has significant implications for the development of risk assessments.

Investigation of the adsorption-desorption behavior of antibiotics by polybutylene succinate and polypropylene aged in different water conditions

Microplastics (MPs) are widely present in aqueous environments and aged by natural components of complex water environments, such as salinity (SI) and dissolved organic matter (DOM). However, the effects of multicondition aging on the physicochemical properties and environmental behavior of MPs have not been completely investigated. In this study, the degradable MP polybutylene succinate (PBS) was used to investigate the environmental behavior of sulfamethoxazole (SMZ) and was compared with polypropylene (PP). The results showed that the single-factor conditions of DOM and SI, particularly DOM, promoted the aging process of MPs more significantly, especially for PBS. The degrees of MP aging under multiple conditions were lower than those under single-factor conditions. Compared with PP, PBS had greater specific surface area, crystallinity, and hydrophilicity and thus a stronger SMZ adsorption capacity. The adsorption behavior of MPs fitted well with the pseudo-second-order kinetic and Freundlich isotherm models, indicating multilayer adsorption. Compared with PP, PBS showed relatively a higher adsorption capacity, for example, for MPs aged under DOM conditions, the adsorption of SMZ by PBS was up to 5.74 mg/g, whereas that for PP was only 3.41 mg/g. The desorption experiments showed that the desorption amount of SMZ on MPs in the simulated intestinal fluid was greater than that in Milli-Q water. In addition, both the original PBS and the aged PBS had stronger desorption capacities than that of PP. The desorption quantity of PBS was 1.23-1.84 times greater than PP, whereas the desorption rates were not significantly different. This experiment provides a theoretical basis for assessing the ecological risks of degradable MPs in complex water conditions.

UV and chemical aging alter the adsorption behavior of microplastics for tetracycline

This study evaluates the "vector" effects of different microplastics (MPs) on coexisting pollutants. The adsorption of tetracycline was studied on biodegradable plastics poly(butylene adipate-co-terephthalate) (PBAT) and non-biodegradable plastics polystyrene (PS), polypropylene (PP), and polyethylene (PE) after UV aging and chemical aging. The physicochemical properties of PBAT changed more obviously after UV radiation and chemical aging comparing to PS, PP and PE. Pores and cracks appear on the surface of aged PBAT. The crystallinity increased from 29.2% to 52.62%. In adsorption experiments, pristine and aged PBAT had strong vector effects on the adsorption of tetracycline than PS, PP and PE. The adsorption capacity of tetracycline on PBAT was increased from 0.7980 mg g^-1 to 1.2669 mg g^-1 after chemical aging. The adsorption mechanism indicated that electrostatic interactions and hydrogen bonds contribute to the adsorption process. In addition, for the adsorption of tetracycline on PS, π-π interaction was the main cause, and the adsorption mechanism was not considerably changed by aging. In conclusion, this study demonstrates that biodegradable plastics have substantial vector effect on coexisting pollutants at the end of their life cycle, this contributes to assessment of the risk from microplastic pollution.