Effect of cadmium on the sorption of tylosin by polystyrene microplastics

Microplastic and antibiotics in waters: Interactions and environmental risks

Antibiotics (ATs) are ubiquitously detected in natural waters worldwide, and their tendency to co-migrate with microplastics (MPs) post-adsorption leads to heightened environmental risk. Research on the adsorption of ATs on MPs and their subsequent effects on the environmental risks is gaining significant attention globally. This adsorption process predominantly occurs through hydrophobic forces, hydrogen bonds, and electrostatic interactions and is influenced by various environmental factors. The interaction between MPs and ATs exhibited varying degrees of efficiency across different pH levels and ionic strengths. Furthermore, this paper outlines the environmental risks associated with the co-presence of MPs and ATs in aquatic environments, emphasizing the potential effect of MPs on the distribution of antibiotic resistance genes (ARGs) and related environmental risks. The potential hazards posed by MPs and ATs in aquatic systems warrant serious consideration. Future research should concentrate on the adsorption of ATs/ARGs on MPs under real environmental conditions, horizontal gene transfer on MPs, as well as biofilm formation and agglomeration behavior on MPs that needs to be emphasized.

Influence of cephalexin on cadmium adsorption onto microplastic particles in water: Human health risk evaluation

This paper explores the impact of environmental factors on the adsorption of cadmium (Cd) and cephalexin (CEX) onto polyethylene (PE) microplastics. The study focused on Cd adsorption behavior on microplastics (MPs) of various sizes, revealing that particles sized 30-63 μm exhibited the highest adsorption capacity compared to other sizes. Cd sorption was significantly influenced by initial pH and salinity levels. Experimental data closely matched both the Langmuir (R2 > 0.91) and Freundlich (R2 > 0.92) isotherms. Cd adsorption onto PE particles was greater than CEX adsorption, with the maximum Cd uptake capacity measured at 1.8 mg/g. FTIR analysis indicated that Cd and CEX adsorption onto MPs was likely governed by physical interactions, as no new functional groups were detected post-uptake. The desorption rates of Cd and CEX from PE microplastics were evaluated in various liquids, including aqueous solution, tap water, seawater, and synthetic gastric juice. The health risks associated with Cd, in combination with MPs and CEX, for both children and adults were assessed in groundwater and aqueous solutions. This study offers scientific insights and guidelines for examining the environmental behavior, migration, and transformation of microplastics and their related ecological risks in scenarios of combined pollution.

Microplastics and Co-pollutants in soil and marine environments: Sorption and desorption dynamics in unveiling invisible danger and key to ecotoxicological risk assessment

Microplastics (MPs) and their co-pollutants pose significant threats to soil and marine environments, necessitating understanding of their colonization processes to combat the plastic pandemic and protect ecosystems. MPs can act as invisible carriers, concentrating and transporting pollutants, leading to a more widespread and potentially toxic impact than the presence of either MPs or the pollutants alone. Analyzing the sorption and desorption dynamics of MPs is crucial for understanding pollutants amplification and predicting the fate and transport of pollutants in soil and marine environments. This review provides an in-depth analysis of the sorption and desorption dynamics of MPs, highlighting the importance of considering these dynamics in ecotoxicological risk assessment of MPs pollution. The review identifies limitations of current frameworks that neglect these interactions and proposes incorporating sorption and desorption data into robust frameworks to improve the ability to predict ecological risks posed by MPs and co-pollutants in soil and marine environments. However, failure to address the interplay between sorption and desorption can result in underestimation of the true impact of MPs and co-pollutants, affecting livelihoods and agro-employments, and exacerbate poverty and community disputes (SDGs 1, 2, 3, 8, 9, and 16). It can also affect food production and security (SDG 2), life below water and life on land (DSGs 14 and 15), cultural practices, and natural heritage (SDG 11.4). Hence, it is necessary to develop new approaches to ecotoxicological risk assessment that consider sorption and desorption processes in the interactions between the components in the framework to address the identified limitations.

Prediction of the bioaccessibility and accumulation of cadmium in the soil-rice-human system based on optimized DGT and BCR coupled models

Cadmium, as a typical heavy metal, has the potential to induce soil pollution and threaten human health through the soil-plant-human pathway. The conventional evaluation method based on the total content in soil cannot accurately represent the content migrated from the food chain to plants and the human body. Previous studies focused on the process of plant enrichment of heavy metals in soil, and very few studies directly predicted human exposure or risk through the labile state of Cd in soil. Hence, a relatively accurate and convenient prediction model of Cd release and translocation in the soil-rice-human system was developed. This model utilizes available Cd and soil parameters to predict the bioavailability of Cd in soil, as well as the in vitro bioaccessibility of Cd in cooked rice. The bioavailability of Cd was determined by the Diffusive Gradients in Thin-films technology and BCR sequential extraction procedure, offering in-situ quantification, which presents a significant advantage over traditional monitoring methods and aligns closely with the actual uptake of heavy metals by plants. The experimental results show that the prediction model based on the concentration of heavy metal forms measured by BCR sequential extraction procedure and diffusive gradients in thin-films technique can accurately predict the Cd uptake in rice grains, gastric and gastrointestinal phase (R2=0.712, 0.600 and 0.629). This model accurately predicts Cd bioavailability and bioaccessibility across the soil-rice-human pathway, informing actual human Cd intake, offering scientific support for developing more effective risk assessment methods.

Assessing microplastics-antibiotics coexistence induced ciprofloxacin-resistant Pseudomonas aeruginosa at a water region scale

Microplastics (MPs) waste is widespread globally in water systems. The opportunistic human pathogen Pseudomonas aeruginosa can cause serious acute and chronic infections that are notoriously difficult to treat. Ciprofloxacin (CIP) is broadly applied as an anti-P. aeruginosa drug. A growing evidence reveals that antibiotic-resistance genes-carrying Pseudomonas aeruginosa were detected on MPs forming plastisphere due to their adsorbability along with high occurrence of CIP in water environments. The MPs-niched CIP-resistant P. aeruginosa has been likely to emerge as an unignorable public health issue. Here, we offered a novel approach to assess the development of CIP-resistant P. aeruginosa under MPs-antibiotic coexistence at a water region scale. By combing the adsorption isotherm models used to estimate CIP condensation around MPs and a pharmacokinetic/pharmacodynamic-based microbial population dynamic model, we predicted the P. aeruginosa development on CIP-adsorbed MPs in waters. Our assessment revealed a high antibiotic resistance in the P. aeruginosa populations (∼50 %) with a wider range of waterborne total cell counts (∼10-2-104 cfu mL-1) among water regions in that the resistance proportion was primarily determined by CIP pollution level and relative abundance of various polymer type of MPs. We implicate that water region-specific MPs were highly likely to provide media for P. aeruginosa propagation. Our results highlight the importance of antibiotic-resistant pathogen colonization-emerging environmental medium interactions when addressing global threat from MPs pollution, in the context of MPs-antibiotics co-contamination assessment and for the continued provision of water system management.

When antibiotics encounter microplastics in aquatic environments: Interaction, combined toxicity, and risk assessments

Antibiotics and microplastics (MPs), known as emerging pollutants, are bound to coexist in aquatic environments due to their widespread distribution and prolonged persistence. To date, few systematic summaries are available for the interaction between MPs and antibiotics in aquatic ecosystems, and a comprehensive reanalysis of their combined toxicity is also needed. Based on the collected published data, we have analyzed the source and distribution of MPs and antibiotics in global aquatic environments, finding their coexistence occurs in a lot of study sites. Accordingly, the presence of MPs can directly alter the environmental behavior of antibiotics. The main influencing factors of interaction between antibiotics and MPs have been summarized in terms of the characteristics of MPs and antibiotics, as well as the environmental factors. Then, we have conducted a meta-analysis to evaluate the combined toxicity of antibiotics and MPs on aquatic organisms and the related toxicity indicators, suggesting a significant adverse effect on algae, and inapparent on fish and daphnia. Finally, the environmental risk assessments for antibiotics and MPs were discussed, but unfortunately the standardized methodology for the risk assessment of MPs is still challenging, let alone assessment for their combined toxicity. This review provides insights into the interactions and environment risks of antibiotics and MPs in the aquatic environment, and suggests perspectives for future research.

Effect of cadmium on polystyrene transport in parsley roots planted in a split-root system and assessment of the combined toxic effects

Micro and nanoplastics (MPs/NPs) coupled with heavy metals are prevalent in both aquatic and terrestrial ecosystems. Their ecological toxicity and combined adverse effects have obtained significant concern. Past studies primarily focused on how MPs/NPs influence the behavior of heavy metals. Yet, the possible effects of heavy metals on MP/NP transport and toxicity within co-contaminated systems are still not well-understood. In this study, we conducted split-root experiments to explore the transport and toxicity of polystyrene (PS) particles of varying sizes in parsley seedlings, both with and without the addition of cadmium (Cd). Both the PS-NPs (100 nm) and PS-MPs (300 nm) traveled from the PS-spiked roots (Roots-1) to the non-PS-spiked roots (Roots-2), with or without Cd, possibly because of phloem transport. Furthermore, the presence of Cd reduced the accumulation and movement of PS-NP/MP in the roots, likely due to the increased positive charge (Cd2+) on the PS surface. PS-NPs/MPs in both Roots-1 and Roots-2 were observed using transmission electron microscopy (TEM). When Cd was added to either Roots-1 (PS + Cd|H) or Roots-2 (PS|Cd), there was a minor reduction in the chlorophyll a and carotenoids content in leaves with PS|H. The adverse impacts of MPs|H on both indicators were influenced by the MP concentration. However, chlorophyll b significantly increased in the PS|H, PS + Cd|H, and PS|Cd treatments. Consequently, the chlorophyll a/b ratio declined, indicating inhibition of photosynthesis. The dehydrogenase content showed a minor change in Roots-1 and Roots-2 without Cd stress, whereas it significantly decreased on the Cd-spiked side and subsequently inhibited root growth. In contrast, the marked rise in glutathione (GSH) levels within Cd-spiked roots suggested, based on Gaussian analysis, that GSH and Cd chelation were instrumental in mitigating Cd toxicity. When Cd was introduced to both Roots-1 and Roots-2 simultaneously (PS + Cd|Cd), the aforementioned index showed a notable decline.

Adsorption characteristics of ciprofloxacin hydrochloride on polystyrene microplastics in freshwater

In order to reveal the adsorption mechanism of microplastics (MPs) on antibiotics, polystyrene (PS) was chosen as a typical microplastic, Fenton and high-temperature aging methods were used to obtain aged MPs particles. The adsorption behavior and mechanism of ciprofloxacin hydrochloride (CIP) on PS before and after aging were studied by batch adsorption experiments, and other influencing environmental conditions were evaluated concurrently. The results showed that the adsorption of CIP on PS was an exothermic reaction, the pseudo-second-order model and Freundlich isothermal models could fit the adsorption of CIP on PS. Aging treatment enhanced the adsorption capacity of PS to CIP, and Fenton aging for 7 days had the best effect. The highest adsorption was observed when the solution pH was 6. The adsorption capacity of microplastics gradually decreased with increasing ionic strength and the concentration of fulvic acid, while the aging microplastics changed little with the concentration of fulvic acid. The presence of both Cu (II) and CIP inhibits the adsorption of each other on microplastics. Based on the above findings, the adsorption of CIP on PS is dominated by physical adsorption, and electrostatic interactions and hydrogen bonding interactions are also important mechanisms for the adsorption of CIP on microplastics.

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.

New insights into the size-independent bioactive potential of pristine and UV-B aged polyethylene microplastics

The present study investigates the morphological, physicochemical, and structural changes occurred by the UV-B aging process of low-density polyethylene microplastics (LDPE MPs), as well as the bioactive potential of both pristine and UVaged MPs towards healthy peripheral blood lymphocytes. Specifically, LDPE MPs (100-180 μm) prepared by mechanical milling of LDPE pellets, were UV-B irradiated for 120 days (wavelength 280 nm; temperature 25 °C; relative humidity 50 %) and further examined for alterations in their particle size and surface, their functional groups, thermal stability, and crystallinity (by means of SEM, FTIR spectroscopy, XRD patterns, and TGA measurements, respectively). In parallel, isolated human peripheral blood lymphocytes were treated with different concentrations (25-500 μg mL-1) of either pristine or aged MPs (UVfree and UV120d LDPE MPs) for assessing the cytogenotoxic (by means of trypan blue exclusion test and the cytokinesis-block micronucleus assay using cytochalasin-B) and oxidative effects (using the DCFH-DA staining) in both cases. According to the results, UVfree and UV120d-LDPE MPs, with a size ranging from 100 to 180 μm, can differentially promote cytogenotoxic and oxidative alterations in human lymphocytes. In fact, UVfree LDPE MPs not being able to be internalized by cells due to their size, could indirectly promote the onset of mild oxidative and cytogenotoxic damage in human peripheral lymphocytes, via a dose-dependent but size-independent manner. The latter is more profound in case of the irregular-shaped UV120d-LDPE MPs, bearing improved dispersibility and sharp edges (by means of cracks and holes), as well as oxygen-containing and carbonyl groups. To our knowledge, the present findings provide new data regarding the bioactive behavior of pristine and UV-B aged LDPE MPs, at least in the in vitro biological model tested, thus giving new evidence for their size-independent and/or indirect mode of action.

Impact of microplastics on nicosulfuron accumulation and bacteria community in soil-earthworms system

Microplastics (MPs) widely co-occur with various pollutants in soils. However, the data related to the impacts of MPs on terrestrial animal and microbial properties in pesticide-contaminated soils are few. In this study, the influence of MPs (0.01%, 0.1%, and 1%) on nicosulfuron concentrations in soil (10 µg/g) and earthworms were investigated, moreover, microbial community structure and diversity in soil and earthworm gut were also measured. After 30 days, the concentration of nicosulfuron in soil decreased to 1.27 µg/g, moreover, the residual concentration of nicosulfuron in soil (1%MPs and nicosulfuron) was only 44.8% of that in the single nicosulfuron treatment group. The accumulation of nicosulfuron in earthworms (1%MPs and nicosulfuron) was 7.37 µg/g, which was 1.82 times of that in the single nicosulfuron treatment group. In addition, 1% MPs decreased the richness and diversity of the soil and gut bacterial community in earthworms as well as altered microbial community composition, leading to the enrichment of specific microbial community. Our findings imply that MPs may change the migration of pesticides to terrestrial animal and as well as microbial diversity in earthworms and soil.

A review of the occurrence and degradation of biodegradable microplastics in soil environments

The use of plastics for manufacturing of products and packaging has become ubiquitous. This is because plastics are cheap, pliable, and durable. However, these characteristics of plastics have also led to their disposal in landfill, where they persist. To overcome the environmental challenge posed by conventional plastics (CPs), biodegradable plastics (BDPs) are increasingly being used. However, BDPs form residual microplastics (MPs) at a rate that far exceeds that of CPs, and MPs have negative impacts on the soil environment. This review aimed to evaluate whether the move away from CPs to BDPs is having an overall positive impact on the environment considering the formation of MPs. Topics focused on in this review include the degradation of BDPs in the soil environment and the impacts of MPs originating from BDPs on soil physical and chemical properties, microbial communities, animals, and plants. The information collated in this review can provide scientific guidance for sustainable development of the BDPs industry.

Ecotoxicological effects of antibiotic adsorption behavior of microplastics and its management measures

Microplastics adsorb heavy metals and organic pollutants to produce combined pollution. Recently, the adsorption behavior of antibiotics on microplastics has received increasing attention. Exploring the sorption behavior of pollutants on microplastics is an important reference in understanding their ecological and environmental risk studies. In this paper, by reviewing the academic literature in recent years, we clarified the current status of research on the adsorption behavior of antibiotics on microplastics, discussed its potential hazards to ecological environment and human health, and summarized the influence of factors on the adsorption mechanisms. The results show that the adsorption behavior of antibiotics on microplastics is controlled by the physical and chemical properties of antibiotics, microplastics, and water environment. Antibiotics are adsorbed on microplastics through physical and chemical interactions, which include hydrophobic interaction, partitioning, electrostatic interaction, and other non-covalent interactions. Intensity of adsorption between them is mainly determined by their physicochemical properties. The basic physicochemical properties of the aqueous environment (e.g., pH, salinity, ionic strength, soluble organic matter content, and temperature) will affect the physicochemical properties of microplastics and antibiotics (e.g., particle size, state of dispersibility, and morphology), leading to differences in the type and strength of their interactions. This paper work is expected to provide a meaningful perspective for better understanding the potential impacts of antibiotic adsorption behavior of microplastics on aquatic ecology and human health. In the meantime, some indications for future related research are provided.

Interaction between antibiotics and microplastics: Recent advances and perspective

Both microplastics and antibiotics are emerging pollutants, which are ubiquitous in aquatic environments. With small size, high specific surface area, and attached biofilm, microplastics are capable of adsorbing or biodegrading antibiotic pollutants across aquatic environments. However, the interactions between them are poorly understood, especially factors that affect microplastics' chemical vector effects and the mechanisms driving these interactions. In this review, the properties of microplastics and their interaction behavior and mechanisms towards antibiotics were comprehensively summarized. Particularly, the impact of weathering properties of microplastics and the growth of attached biofilm was highlighted. We concluded that compared with virgin microplastics, aged microplastics usually adsorb more types and quantities of antibiotics from aquatic environments, whilst the attached biofilm could further enhance the adsorption capacities and biodegrade some antibiotics. This review can answer the knowledge gaps of the interaction between microplastics and antibiotics (or other pollutants), offer basic information for evaluating their combined toxicity, provide insights into the distribution of both emerging pollutants in the global water chemical cycle, and inform measures to remove microplastic-antibiotic pollution.

Simultaneous removal of pharmaceuticals and heavy metals from aqueous phase via adsorptive strategy: A critical review

The coexistence of pharmaceuticals and heavy metals is regarded as a serious threat to aquatic environments. Adsorbents have been widely applied to the simultaneous removal of pharmaceuticals and metals from aqueous phase. Through a comprehensive review, behaviors that promote, inhibit, or have no effect on simultaneous adsorption of pharmaceuticals and heavy metals were found to depend on the system of contaminants and adsorbents and their environmental conditions, such as: characteristics of adsorbent and pollutant, temperature, pH, inorganic ions, and natural organic matter. Bridging and competition effects are the main reasons for promoting and inhibiting adsorption in coexisting systems, respectively. The promotion is more significant in neutral or alkaline conditions. After simultaneous adsorption, a solvent elution approach was most commonly used for regeneration of saturated adsorbents. To conclude, this work could help to sort out the theoretical knowledge in this field, and may provide new insights into the prevention and control of pharmaceuticals and heavy metals coexisting in wastewater.

Adsorption behavior of aniline pollutant on polystyrene microplastics

Microplastic contamination is ubiquitous in aquatic environments. As global plastic production increases, the abundance of microplastic contaminants released into the environment has also continued to soar. The hydrophobic surfaces of plastic particles can adsorb a variety of chemical pollutants, and could therefore facilitate toxin accumulation through the food chain. In this study, the adsorption behavior of aniline, a priority environmental pollutant from industrial production, on the surface of polystyrene microplastics (mPS) was investigated. The results showed that the maximum adsorption capacity of mPS was 0.060 mg/g. Adsorption equilibrium was reached after 24 h, and the pseudo-second-order model was employed to explain the adsorption kinetics of aniline on the mPS particles. The Freundlich models could describe the adsorption isotherms. The potential adsorption mechanisms may include π-π interactions and hydrophobic interactions. pH, ionic strength, and ambient temperature of the solution played important roles in the adsorption process.

Antibiotic sorption onto microplastics in water: A critical review of the factors, mechanisms and implications

Microplastics as vectors for contaminants in the environment is becoming a topic of public interest. Microplastics have been found to actively adsorb heavy metals, per-fluorinated alkyl substances (PFAS), polychlorinated biphenyls (PCBs), polyaromatic hydrocarbons (PAHs), pharmaceuticals and personal care products (PPCPs) and polybrominated diethers (PBDs) onto their surface. Particular interest in microplastics capacity to adsorb antibiotics needs further attention due to the potential role this interaction plays on antibiotic resistance. Antibiotic sorption experiments have been documented in the literature, but the data has not yet been critically reviewed. This review aims to comprehensively assess the factors that affect antibiotic sorption onto microplastics. It is recognised that the physico- chemical properties of the polymers, the antibiotic chemical properties, and the properties of the solution all play a crucial role in the antibiotic sorption capacity of microplastics. Weathering of microplastics was found to increase the antibiotic sorption capacity by up to 171%. An increase in solution salinity was found to decrease the sorption of antibiotics onto microplastics, in some instances by 100%. pH also has a substantial effect on sorption capacity, illustrating the significance of electrostatic interactions on the sorption of antibiotics onto microplastics. The need for a uniform experimental design when testing antibiotic sorption is highlighted to remove inconsistencies in the data currently presented. Current literature examines the link between antibiotic sorption and antibiotic resistance, however, further studies are still required to fully understand this emerging global crisis.

Adsorption of typical natural organic matter on microplastics in aqueous solution: Kinetics, isotherm, influence factors and mechanism

With rapid urbanization, microplastics and natural organic matters (NOMs) are ubiquitous in aquatic environment, and microplastics could act as carriers for organic matters in the aqueous solution and may pose a potential risk. In this study, the adsorption behaviors and mechanism of typical NOM, humic acid (HA), on polyvinyl chloride (PVC) and polystyrene (PS) microplastics were investigated. Various influence factors such as solution pH, ions species and concentrations, particle size, and coexisting surfactants were studied. The results suggested that HA adsorption onto PVC and PS was low pH-dependent, and ion species and concentrations have a significant impact on the adsorption capacity. In addition, the particle size of PVC and PS microplastics exhibited a significant correlation with HA adsorption, and the adsorption process was influenced by the surfactant species and concentrations. Moreover, the adsorption behaviors of HA in different real water environments were tested, and UV aging exhibited the opposite effects on adsorption capacity of PVC and PS. Furthermore, the adsorption mechanisms of HA onto PVC and PS were explored, indicating halogen bonding, hydrogen bonding, and π-π interaction play important roles in the adsorption process.

Effects of heavy metals on the adsorption of ciprofloxacin on polyethylene microplastics: Mechanism and toxicity evaluation

Microplastics are plastic particles less than 5 mm in diameter and are widely present in water environments. Their unique surface structures can adsorb coexisting pollutants in the surrounding environment, such as antibiotics and metal ions, leading to compound pollution. The adsorption of ciprofloxacin on polyethylene microplastics under different environmental conditions (pH and salinity) was investigated. The Freundlich model fitted well at 25 °C, indicating that the adsorption of ciprofloxacin by polyethylene microplastics was multilayered, and Fourier Transform infrared spectroscopy (FTIR) analysis indicated that the adsorption of ciprofloxacin by polyethylene microplastics was physical. The kinetic adsorption of ciprofloxacin on polyethylene microplastics followed a pseudo-second-order mode. Heavy metals (Cu²⁺, Cr³⁺, Cr⁶⁺, Cd²⁺, and Pb²⁺) affected the adsorption of ciprofloxacin by microplastics, which was related to the type and concentration of metal ions and the valence state of the ions. The acute toxicity of microplastics and the microplastic-ciprofloxacin-Cu²⁺ complex were evaluated using luminescent Photobacterium phosphoreum, demonstrating the polyethylene toxicity microplastic-ciprofloxacin-Cu²⁺ complex was mainly caused by Cu²⁺ and ciprofloxacin rather than microplastics. This study provides theoretical support for the environmental behavior and ecological effects of microplastics in aqueous environments.

Insights into the interaction mechanism of ofloxacin and functionalized nano-polystyrene

Nano-plastics (NPs), an emerging contaminant in the environment, have a larger specific surface area and can act as a carrier of other contaminants. Thus, insights into the interaction mechanisms between NPs and other pollutants are crucial for the assessment of environmental impacts of NPs in the ecosystems. In this study, the interaction mechanism between NPs and ofloxacin (OFL) were investigated via kinetics, fluorescence quenching, and two-dimensional correlation spectroscopy (2DCOS). The adsorption kinetics of OFL on carboxyl-modified polystyrene (PS-COOH) and amine modified polystyrene (PS-NH₂) closely fitted the pseudo-second-order kinetics model (R² = 0.99). Adsorption kinetics indicated that chemical adsorption is dominant mechanism, and the Fourier Transform Infrared Spectrometer (FT-IR) and X-ray photoelectron spectroscopy (XPS) results showed that the electronic interaction, π-π, and H-binding were also involved in the adsorption process. OFL showed strong fluorescence quenching in the presence of NPs. Stern-Volmer quenching was negatively related with the temperature, which was dominated by the static type of quenching. 2DCOS indicated that the π-π conjugation was dominant in the interaction process, and the interaction process was dependent on the solution pH and salinity. Overall, this work provides new insights into the interaction mechanism of NPs and antibiotics in the aquatic ecosystems.

Heavy metal-mediated adsorption of antibiotic tetracycline and ciprofloxacin on two microplastics: Insights into the role of complexation

Microplastics (MPs) have recently become an emerging environmental concern. Nevertheless, limited information is known about the adsorption of MPs for organic contaminants under combined heavy metals pollution, with an emphasis on the role of complexation. Thus, this study aims to comprehensively compare and investigate the adsorption performance of antibiotic tetracycline (TC) and ciprofloxacin (CIP) on two polar MPs (polyamide (PA) and polyvinyl chloride (PVC)) affected by Cu(II) and Cd(II) with contrasting complexation abilities. Batch adsorption experiments were used in combination with speciation calculation, zeta potential determination, FTIR spectroscopy characterization and investigation of the affinity of MPs for heavy metals. Results showed that the sorption kinetics and isotherms of TC and CIP on PA and PVC could be well fitted to pseudo-second-order and Langmuir models, respectively, both in the absence and presence of Cu and Cd, suggesting that multiple interactions and monolayer adsorption played an important role in the adsorption process. The presence of Cu substantially improved TC and CIP adsorption and obviously changed the pH dependence of their adsorption onto both MPs, which may result from the Cu-induced strong complexation with TC and CIP. The presence of Cd slightly enhanced TC adsorption on both MPs while reduced CIP adsorption especially on PVC, which may be ascribed to the Cd-induced cationic bridging effects in TC adsorption and the competitive adsorption of Cd in CIP adsorption. Therefore, the heavy metal-mediated complexation effects may play a dominant role in antibiotic adsorption by MPs only in the presence of heavy metals with strong complexation ability while the adsorption performance in the presence of heavy metals with negligible complexation capacity may be influenced by effects other than complexation. This study helps further understand the heavy metal-mediated adsorption behavior of organic contaminants on polar MPs and the role of complexation reactions therein.

The weathering process of polyethylene microplastics in the paddy soil system: Does the coexistence of pyrochar or hydrochar matter?

This study is based on a particular test site to simulate the weathering process of microplastics (MPs) in paddy soil. A substantial amount of plastic waste, especially MPs, inevitably accumulates in agricultural soil due to the high consumption and short average use of plastics. Recently, MP pollution has become a global environmental concern. However, insight into the soil weathering process of MPs in paddy soil, particularly in the presence of biochar, is lacking. In this study, the physicochemical properties of polyethylene (PE) MPs were determined through a 24-week weathering system conducted in paddy soil, paddy soil with pyrochar, or hydrochar. Moreover, the sorption of original and weathered PE MPs toward three typical pollutants (cadmium/Cd, bisphenol A/BPA, and dimethyl phthalate/DMP) was investigated. The surface of PE MPs was fractured, 1.1-fold rougher, yellow-colored (11.7 units), and 1.8-fold more oxidized after paddy soil weathering. In addition, the crystallinity, negative charge, and stronger hydrophilicity of weathered PE MPs increased compared to original PE MPs. Weathering in a pyrochar or hydrochar system caused fissures, extensive destruction of amorphous areas, and accelerated chemical or bio-oxidation processes for PE MPs, resulting in a more noticeable change in roughness (1.4-2.2-fold), yellow color (12.7-13.7), crystallinity (1.2-1.5-fold), and oxygen content (2.5-3.6-fold). Weathered PE MPs facilitated the sorption with Cd and BPA, attributed to larger specific surface area, abundant polar functional groups, and increased negatively charged sites. However, sorption of DMP to PE MPs was highly influenced by their hydrophobicity, resulting in decreased hydrophobic partition sorption on weathered PE MPs. Overall, paddy soil weathering affected the properties of PE MPs and enhanced sorption of Cd and BPA but reduced sorption of DMP. The coexistence of biochar exacerbated the paddy soil weathering effect. The insight gained from this study assists in better understanding the weathering process of PE MPs in agricultural soils.

Roles of polystyrene micro/nano-plastics as carriers on the toxicity of Pb2+ to Chlamydomonas reinhardtii

Little information could be consulted on the impacts of micro-plastics as carriers on toxicity of heavy metals, especially for micro-plastics of different sizes. Therefore, this study investigated the adsorption and desorption of Pb²⁺ on polystyrene plastics with nano- and micro-size (NPs and MPs), and further evaluated the roles of NPs and MPs as carriers on the toxicity of Pb²⁺ to Chlamydomonas reinhardtii (C. reinhardtii). The results showed that NPs showed higher adsorption capacities and a lower desorption rate for Pb²⁺ than MPs. The growth inhibitory rates (IR) of mixed and loaded Pb²⁺ with MPs to C. reinhardtii were 18.29% and 15.76%, respectively, which were lower than that of Pb²⁺ (22.28%). The presence of MPs decreased the bioavailability of Pb²⁺ to C. reinhardtii by a competitive adsorption for Pb²⁺ between MPs and algal cells, and suppressed membrane damage and oxidative stress caused by Pb²⁺. Maximum IR was observed for the mixture of NPs with Pb²⁺ (35.64%), followed by Pb²⁺ loaded on NPs (30.13%), single NPs (26.71%) and Pb²⁺ (21.01%). The internalization of NPs with absorbed Pb²⁺ intensified lipid peroxidation. The mixed and loaded microplastics with Pb²⁺ had more negative effects on C. reinhardtii than the single microplastics. The size-dependent effect was observed in the capacity of heavy metal ions carried by microplastics and the roles of microplastics as carriers on the toxicity of Pb²⁺. The results showed that the indirect risk of microplastics as 'carriers' could not be ignored, especially for NPs.

Structure, mechanism, and toxicity in antibiotics metal complexation: Recent advances and perspectives

Antibiotic-metal complexes (AMCs) formed by antibiotics and metal ions have attracted considerable attentions in recent years. Although different removal methods for AMCs have been reported in the literature, very few investigations have focused on the mechanisms and toxic effects of antibiotic-metal coordination. This review briefly describes the structural characteristics of various commonly used antibiotics and the coordination mechanisms with metal ions. Considering the complexity of the real environment, various environmental factors affecting AMC formation are highlighted. The effects of AMCs on microbial community structure and the role of metal ions in influencing resistant genes from the molecular perspective are of interest within this work. The toxicities and mechanisms of AMCs on different species of biota are also discussed. These findings underline the need for more targeted detection and analysis methods and more suitable toxicity markers to verify the combination of antibiotics with metal ions and reveal environmental toxicities in future. This review presents an innovative idea that antibiotics combined with metal ions will change the toxicity and environmental behavior of antibiotics.

Competitive and cooperative sorption between triclosan and methyl triclosan on microplastics and soil

The sorption behavior of single contaminant on microplastics (MPs) has been extensively studied; however, little is known about that in the more actual scenario containing multiple contaminants. In this study, the interaction between triclosan (TCS) and its primary metabolite, methyl triclosan (MTCS) on polyethylene (PE), polystyrene (PS), and soil was investigated. Results indicate that the more hydrophobic MTCS had much higher sorption capacity and affinity than TCS. Competitive sorption between them occurred in most cases and appeared to be concentration-dependent (in the range of 0.1-5 mg TCS/L and 0.01-≤0.05 mg MTCS/L of primary solutes, respectively): more pronounced at low concentrations of primary solute, while progressively weaker with the increase of concentrations. Among the sorbents, MTCS exhibited strong antagonistic effect on TCS sorption for MPs, especially PS, while significant suppression of MTCS sorption by TCS took place for soil and PS rather than PE. Additionally, it is interesting to observe that the presence of TCS substantially facilitated the sorption of MTCS exclusively at high concentrations on both PS and soil, presumably attributed to the solute-multilayer formation. Furthermore, the magnitude of the two effects varied with solution pH: TCS sorption at alkaline pH was the most suppressed by MTCS because the less hydrophobic dissociated TCS tended to be displaced, and the highest cooperative sorption of MTCS with TCS occurred at acidic pH because neutral TCS preferentially adsorbed on sorbent surface could provide additional sorption sites for MTCS. Both competitive and cooperative effects between multiple contaminants may affect their fate and transport, thereby these findings are helpful for assessing the environmental risk of MPs and TCS in soil.

Adsorption of Tannic Acid and Macromolecular Humic/Fulvic Acid onto Polystyrene Microplastics: A Comparison Study

Dissolved organic matter (DOM) has been widely reported to influence the environmental behavior of microplastics (MPs), but little is known about the properties and mechanisms of interaction between specific DOM components and MPs. Here, we studied the adsorption of three representative DOM components (humic acid, HA; fulvic acid, FA; and tannic acid, TA) on polystyrene (PS) MPs in batch adsorption experiments. Results revealed that HA/FA adsorption was greater under acidic conditions, while higher TA adsorption on PS was found at pH 4 and 6. The divalent cation (Ca2+) exerted a more prominent role in enhancing HA, FA, and TA adsorption on PS than did monovalent ones (K+ and Na+). The adsorption process fitted well with the Freundlich isotherm model and the pseudo-second-order kinetics model. The adsorption site heterogeneity was evaluated using the site energy distribution analysis based on the Freundlich model. The greater binding ability of HA on the PS surface caused a more negatively charged surface than FA/TA, as reflected by Zeta potential values. The findings of this study not only provide valuable information about the adsorption behavior and interaction processes of various DOM components on PS MPs, but also aid our efforts to evaluate the environmental behaviors of MPs.

Photocatalytic degradation of (micro)plastics using TiO2-based and other catalysts: Properties, influencing factor, and mechanism

(Micro)plastics pollution has raised global concern because of its potential threat to the biota. The review on recent developments of photocatalytic degradation of (micro)plastics is still insufficient. In this study, we have discussed various bare and composites photocatalysts involved in the photocatalytic degradation of (micro)plastics. The photocatalytic mechanisms and factors affecting the degradation were also discussed. To improve the performance of photocatalysts, their surface is modified with metal or non-metal dopants. These doped photocatalysts are then compounded with a variety of environmentally friendly and nontoxic polymers to prepare multifunctional composites. The generation of reactive oxygen species (ROS) plays an important role in the photocatalytic degradation of (micro)plastics, and superoxide ions (O₂^-) and hydroxyl radicals (OH) participate in the photocatalytic degradation, leading to the breaking of the polymer chain and the production of some intermediates. Although satisfactory progress has been achieved in the photodegradation of (micro)plastics, most photocatalytic degradation technologies investigated to date cannot realize the complete mineralization of (micro)plastics. Furthermore, based on the current challenges of the existing photocatalytic degradation technologies, perspectives for future research directions have been proposed. This review presents a systematic summary of the progress made in the photocatalytic degradation of (micro)plastics and offers a comprehensive reference for future research on improving the (micro)plastics photocatalytic degradation efficiency.

New insights on metal ions accelerating the aging behavior of polystyrene microplastics: Effects of different excess reactive oxygen species

Microplastics (MPs) will coexist with various pollutants in the environment, but it is not clear whether these pollutants will affect the aging process of MPs. The aging process of polystyrene microplastics (PS-MPs) mediated by Cu²⁺ and Pb²⁺ was investigated in this study. The results showed that the aging rate of PS-MPs mediated by Cu²⁺ and Pb²⁺ were significantly higher than that of ultrapure water (After 7 days of light irradiation, the CI values of aging PS-MPs mediated by ultrapure water, Cu²⁺ and Pb²⁺ increased from 0.030 of original PS-MPs to 0.034, 0.048 and 0.086 respectively). This process may be related to the generation of a large amount of reactive oxygen species, because OH were detected in PS-MPs suspension mediated by Cu²⁺, which were significantly higher than those in ultrapure water, while ¹O₂ mediated by Pb²⁺ were more. However, these photo-aging effects were significantly inhibited by reactive oxygen species (ROS) quencher, which indicated that excessive ROS production was the main reason for metal ions to promote the photo-aging of PS-MPs. In addition, this study reported that excessive ROS will accelerate the formation of carbonyl group on the surface of PS-MPs, and lead to the change of physical and chemical properties of PS-MPs. This study provides new insights for the environmental behavior of MPs under the condition of combined pollution.

Current status of microplastics pollution in the aquatic environment, interaction with other pollutants, and effects on aquatic organisms

Microplastics, as emerging pollutants, have received great attention in the past few decades due to its adverse effects on the environment. Microplastics are ubiquitous in the atmosphere, soil, and water bodies, and mostly reported in aqueous environment. This paper summarizes the abundance and types of microplastics in different aqueous environments and discusses the interactions of microplastics with other contaminants such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), antibiotics, and heavy metals. The toxicity of microplastics to aquatic organisms and microorganisms is addressed. Particularly, the combined toxic effects of microplastics and other pollutants are discussed, demonstrating either synergetic or antagonistic effects. Future prospectives should be focused on the characterization of different types and shapes of microplastics, the standardization of microplastic units, exploring the interaction and toxicity of microplastics with other pollutants, and the degradation of microplastics, for a better understanding of the ecological risks of microplastics.

Photo-transformation of microplastics and its toxicity to Caco-2 cells

In recent years, microplastics (MPs) pollution, as a global environmental problem, has been widely concerned by countries all over the world. However, the research on the impact of MPs on human health is still limited. In this study, we studied the photo-transformation behavior of polystyrene microplastics (PS-MPs) under ultraviolet light and its toxicity to Caco-2 cells. Our results showed that the surface of PS-MPs was roughened by light, and cracks and pits appeared. UV-vis spectra showed that the opening of phenyl ring and the formation of carbonyl group might exist in this process. Based on FTIR and 2D-COS analysis, we observed the formation of carbonyl group and hydroxyl group, and preliminarily determined that the order of photo-transformation of PS-MPs was 698 (CH) > 752 (CH) > 1030 (CO) > 3645 (OH/OOH) > 1740 (CO). XPS showed that the photo-transformation of PS-MPs was a process in which carbon-containing functional groups were gradually partially transformed into oxygen-containing functional groups. Finally, the toxicity results showed that with the increase of PS-MPs concentration and the extension of light irradiation time, the survival rate of Caco-2 cells gradually decreased and the integrity of cell membrane was destroyed. The increased cytotoxicity can be explained at least in part by the fact that the toxicity of oxygen-containing functional groups is greater than that of carbon-containing functional groups, but how these functional groups affect the cytotoxicity of cells still needs sustained research in the future. This study can provide new insights for understanding the environmental behavior and ecological effects of PS-MPs in the environment.

Microplastics as a vehicle of heavy metals in aquatic environments: A review of adsorption factors, mechanisms, and biological effects

Microplastics (MPs) have recently attracted much attention due to their widespread distribution in the aquatic environment. Microplastics can act as a vector of heavy metals in the aquatic environment, causing a potential threat to aquatic organisms and human health. This review mainly summarized the occurrence of microplastics in the aquatic environment and their interaction with heavy metals. Then, we considered the adsorption mechanisms of MPs and heavy metals, and further critically discussed the effects of microplastics properties and environmental factors (e.g., pH, DOM, and salinity) on the adsorption of heavy metals. Finally, the potential risks of combined exposure of MPs and heavy metals to aquatic biota were briefly evaluated. This work aims to provide a theoretical summary of the interaction between MPs and heavy metals, and is expected to serve as a reference for the accurate assessment of their potential risks in future studies.

Interaction of Microplastics with Antibiotics in Aquatic Environment: Distribution, Adsorption, and Toxicity

As two major types of pollutants of emerging concerns, microplastics (MPs) and antibiotics (ATs) coexist in aquatic environments, and their interactions are a source of increasing concern. Therefore, this work examines the interaction mechanisms of MPs and ATs, and the effect of MPs on ATs bioavailability and antibiotic resistance genes (ARGs) abundance in aquatic environments. First, the mechanisms for ATs adsorption on MPs are summarized, mainly including hydrophobic, hydrogen-bonding, and electrostatic interactions. But other possible mechanisms, such as halogen bonding, CH/π interaction, cation-π interaction, and negative charge-assisted hydrogen bonds, are newly proposed to explain the observed ATs adsorption. Additionally, environmental factors (such as pH, ionic strength, dissolved organic matters, minerals, and aging conditions) affecting ATs adsorption by MPs are specifically discussed. Moreover, MPs could change the bioaccumulation and toxicity of ATs to aquatic organisms, and the related mechanisms on the joint effect are reviewed and analyzed. Furthermore, MPs can enrich ARGs from the surrounding environment, and the effect of MPs on ARGs abundance is evaluated. Finally, research challenges and perspectives for MPs-ATs interactions and related environmental implications are presented. This review will facilitate a better understanding of the environmental fate and risk of both MPs and ATs.

Interactions between microplastics/nanoplastics and vascular plants

Microplastics and nanoplastics are distributed in the environments universally. The interrelationship between vascular plants and micro/nanoplastics began to attract attention in recent years. Based on the relevant literatures collected from various databases, this review focuses on two topics: 1) the effect of vascular plants on the fate of micro/nanoplastics; 2) the effects of micro/nanoplastics on vascular plants. The review of the available studies reveals that vascular plants can act as sinks for microplastics and nanoplastics as their surfaces can adsorb these plastics; moreover, nanoplastics can be internalized by plants. Plastics on the surfaces and in the interiors of vascular plants can cause various phytotoxicity effects, including impacts on growth, photosynthesis, and oxidative stress. Furthermore, the results and mechanisms of phytotoxicity effects caused by microplastics or nanoplastics can be very different. However, knowledge gaps still exist in the relationships between micro/nanoplastics and vascular plants based on the analysis of available studies; thus, potential subjects for future studies were proposed, including the fates, analysis methods, influencing factors, mechanisms of phytotoxicity, and further influences of microplastics and nanoplastics in the vascular plant ecosystems. This study presents a review of micro/nanoplastics-vascular plant research and reaches a basis for future research.

Sorption of tetracycline onto hexabromocyclododecane/polystyrene composite and polystyrene microplastics: Statistical physics models, influencing factors, and interaction mechanisms

Microplastics (MPs) are becoming a major concern due to their great potential to sorb and transport pollutants in the aquatic environment; hexabromocyclododecane (HBCD) is a common chemical additive in polystyrene (PS) MPs. However, the underlying mechanisms for the interaction of tetracycline (TC) onto HBCD-PS composites MPs (HBCD-PS MPs) are still not well documented. Our findings showed that the addition of HBCD resulted in a relatively higher hydrophobicity of PS MPs, and significantly enhanced the sorption ability of HBCD-PS MPs for TC. The kinetic models suggested that the sorption of TC onto PS and HBCD-PS MPs were mainly controlled by film diffusion and intra-particle diffusion, respectively. The statistical physics models were used to elucidate the sorption of TC onto PS and HBCD-PS MPs was associated with the formation of the monolayer, and the results indicated the TC was sorbed onto the two MPs by both multi-molecular and non-parallel processes. The TC sorption was solution pH-dependent while the effect of NaCl content on TC sorption was negligible. The presence of Cu(Ⅱ), Pb(Ⅱ), Cd(Ⅱ), and Zn(Ⅱ) ions had different influences on the TC sorption onto both the MPs. Overall, various mechanisms including π-π and hydrophobic interactions jointly regulated the sorption of TC onto both the MPs. Our results provided new insights into the sorption behavior and interaction mechanisms of TC onto both the MPs and highlighted that the addition of HBCD likely increased the enrichment capacity of MPs for pollutants in the environment.