Adsorption of perfluoroalkyl substances on polyamide microplastics: Effect of sorbent and influence of environmental factors

Effects of co-exposure to microplastics and perfluorooctanoic acid on the Caco-2 cells

As plastics are produced and used, humans are inevitably exposed to microplastics (MPs) on a daily basis. The pollution of MPs has aroused widespread human concern. Perfluorooctanoic acid (PFOA), a persistent organic pollutant (POP), can be adsorbed by microplastics and may exacerbate human health hazards. In this study, we investigated the effects of co-exposure of PET MPs and PFOA on the human intestinal tract in terms of both cytotoxicity and intestinal barrier through in vitro experiments. The results showed that PFOA induced cellular oxidative stress, mitochondrial dysfunction exerted cytotoxic effects, and inhibited tight junction (TJ) protein expression causing intestinal barrier damage. PET MPs can synergize with PFOA to exacerbate the deleterious effects on the intestinal tract by decreasing cell membrane permeability to increase PFOA accumulation in the cell and enhancing the ability of PFOA to inhibit zonula occludens-1 (ZO-1) proteins.

Phosphorescent Naphthalene-Doped Carbon Nitride Quantum Dots for Selective Detection of Polyamide Microplastics

Fluorescent dye labeling is a visual method for the detection of microplastics (MPs). However, the interference from the background fluorescence in complex environmental samples results in overestimation of the MP number, and the nonspecific fluorescent dye cannot selectively detect a single type of MPs. Herein, phosphorescent naphthalene-doped carbon nitride quantum dots (NDCNQDs) were prepared via incomplete condensation of urea with 1,5-diaminonaphthalene at 250 °C and used as a specific dye to stain polyamide (PA) MPs via hydrogen bonding. A phosphorescence imaging method for the selective detection of PA MPs was proposed. Benefitting from the long lifetime of phosphorescence, the interference from the background fluorescence in environmental samples was avoided. The recoveries for PA MPs in pond water samples and pond mud samples were 91.2-108.4%. PA MPs in environmental samples (e.g., streamwater, sediment, house dust) were analyzed without complicated pretreatment. This work provides a strategy for the specific detection of PA MPs in environmental samples.

Interpretable machine learning models reveal the partnership of microplastics and perfluoroalkyl substances in sediments at a century scale

It is challenging to explore the complex interactions between perfluoroalkyl substances (PFASs) and microplastics in lake sediments. The partnership of perfluoroalkyl substances (PFASs) and microplastics in lake sediments are difficult to determine experimentally. This study utilized sediment cores from Taihu Lake to reconstruct the coexistence history and innovatively reveal the collaboration between PFASs and microplastics by using post-hoc interpretable machine learning methods. Microplastics and PFASs emerged in the 1960s and have significantly increased since the 1990s. PFASs and microplastics had the highest growth rate in the 0-10 cm range, with average growth rates of 35.96 pg/g/year and 4.40 items/year per 100 g, respectively. Extreme gradient boosting demonstrated the best simulation of PFASs and microplastics in machine learning models. Feature importance and Shapley additive explanations semi-quantitatively clarified the importance of transparent and pellet microplastics on PFASs concentrations, as well as the importance of perfluorooctane sulfonate (PFOS) and ΣPFASs on microplastics. Moisture content, redox potential, χfd, and χARM were the key influencing factors on contaminants. Partial dependence plots showed the influencing thresholds were 0.30 ng/g for ΣPFASs and 0.15 ng/g for PFOS on microplastics, and 10 items per 100 g for pellets and 12 items per 100 g for transparent plastics on PFASs. This study elucidated the interactions between two typical emerging contaminants on a century-scale through the intersection of environmental geochemistry and interpretable machine learning.

How do polyhydroxyalkanoates aged by aerobic compost interact with steroidal estrogens to alter their adsorption and transport characteristics? Kinetics, isotherms, and influencing factors

Despite evidence indicating a substantial presence of microplastics (MPs) in organic fertilizers, research exploring the differences of MPs among various types of organic fertilizers remains limited. Additionally, MPs can act as carriers for organic pollutants, influencing their environmental behaviors. This study investigated the presence of MPs in organic fertilizers and their effects on the environmental behaviors of steroidal estrogens. We compared the adsorption of estrone (E1) and estrone sulfate sodium (E1-3S) by original PHA and PHA aged through cattle manure-straw compost (CS) and vermicompost (VC). PHA-CS exhibited the highest adsorption capacities for E1 (47.97 ± 2.20 μg g-1) and E1-3S (64.32 ± 2.09 μg g-1). Dissolved organic matter (DOM) from CS and VC profoundly affected estrogen adsorption onto PHA, with VC-derived DOM inhibiting and CS-derived DOM promoting adsorption. In simulated avian digestive fluid, the desorption efficiency of E1 was 72.46 %-93.43 % higher than that of E1-3S, indicating increased toxicity and bioavailability of E1 upon bird ingestion. Transport experiments strongly suggested that estrogens could be more easily retained in porous media containing aged PHA. This study advances our understanding of the adsorption mechanisms of aerobic compost-derived PHA on estrogens and their desorption behaviors under different environmental conditions.

Efficient PFAS Removal Using Reusable and Non-Toxic 3D Printed Porous Trianglamine Hydrogels

Per- and polyfluoroalkyl substances (PFAS) are now a paramount concern in water remediation. Nowadays, urgent action is required for the development of advanced technologies aimed at capturing PFAS and mitigating their impact. To offer a solution, a functional 3D printed hydrogel tailored is designed to trap a broad spectrum of PFAS contaminants. The hydrogel is made of a photo-crosslinked dimethacrylate-ureido-trianglamine (DMU-Δ) and Pluronic P123 dimethacrylate (PDM) fabricated by stereolithography (SLA). With the aid of 3D-printing, porous and nonporous hydrogels (3D-PSHΔ, 3D-SHΔ) as well as quaternized hydrogels (3D-PSHΔQ+) are prepared. These tailored hydrogels, show high uptake capacities and fast removal kinetics for PFAS from aqueous sources. The PFAS removal efficiency of these hydrogels are then compared to P123 hydrogels with no trianglamine (3D-SH). The 3D-SH hydrogel shows no affinity to PFAS, proving that the sorption is due to the interaction between the trianglamine (Δ) and PFAS. Metadynamic simulations also confirmed this interaction. The porous matrices showed the fastest and highest uptake capacity. 3D-PSHΔ is able to capture ≈ 91% of PFAS within 5 h using initial concentrations of 5 and 0.5 ppm in both deionized and river water. The sorption of PFAS is further enhanced by introducing permanent positive charges to the structure of the porous hydrogels, resulting in even faster sorption kinetics for both long and short PFAS chains with diverse polar heads. Besides the remarkable efficiency in capturing PFAS, these designed hydrogels are non-toxic and have outstanding chemical and thermal stability, making them a brilliant candidate for mass use in the combat against PFAS pollution.

Insight into the effect of natural aging of polystyrene microplastics on the sorption of legacy and emerging per- and polyfluorinated alkyl substances in seawater

Microplastics (MPs) are abundant in aquatic environments and due to their small size, surface properties, and strong hydrophobicity, they can easily sorb chemicals, thus potentially acting as pollutant carriers. To date, most studies investigating the sorption of chemicals on MPs have principally focused on virgin MPs. However, MPs in the environment undergo aging effects, which changes their physical-chemical properties and aptitude to interact with chemicals, such as per- and polyfluorinated alkyl substances (PFAS) referred to as "forever chemicals". In this study, we compared the sorption behavior of nine PFAS, exhibiting different physical-chemical properties, on virgin and naturally aged polystyrene microplastic (PS-MPs) to explore to what extent the environmental aging affects the sorption behavior of the PS-MPs for different legacy and emerging PFAS in seawater. Differences in the morphology and surface properties of aged PS-MPs were examined by infrared spectroscopy, surface area analysis, scanning electron microscopy, and X-ray diffraction. Results revealed that compared to virgin PS-MPs, aged PS-MPs exhibited morphological changes (e.g. cavities, pits, and rough surfaces) with biofilm development and signs of oxidation on the MPs surface. PFAS sorption on PS-MPs was enhanced for the aged PS-MPs compared to virgin PS-MPs with Kd values ranging from 327 L kg-1 for PFOA to 3247 L kg-1 for PFOS in aged PS-MPs. The difference in sorption capacity was mainly attributed to the physical-chemical changes and the adhered biofilm observed in aged PS-MPs. Results also showed that virgin PS-MPs adsorb PFAS mainly through steric hindrance, while the aged PS-MPs may involve more complex sorption mechanisms. This research provides additional insights into the ability of aged MPs as potential carriers of legacy and emerging contaminants in the marine environment.

A comprehensive analysis and risk evaluation of microplastics contamination in Australian commercial plant growth substrates: Unveiling the invisible threat

In Australia, quality standards for composts and potting mixes are defined by AS4454-2012 and AS3743-2012. These standards outline key parameters, including physicochemical properties, nutrient content, and plant toxicity. However, they do not address emerging pollutants like microplastics (< 1 mm). This study investigates the prevalence and characteristics of MPs in commercial plant growth substrates (PGS), including nineteen potting mixes and five composts, revealing a significant occurrence of MPs, with concentrations ranging from 233 to 7367 particles Kg-1 and an average of 1869 ± 109 particles Kg-1. MPs categorized by shape, size, and color, with fragments (491 ± 34 particles Kg-1), white colour (3700 ± 917 particles Kg-1), and size 500 µm being predominant. The polymer composition was diverse, with polyethylene being the most prevalent, followed by polypropylene and others. Polyterpene, Polyalkene, Pentaerythritol, and Propylene glycol were identified in PGS for the first time. The structural equation model showed that physicochemical properties like pH, EC, TOC, and heavy metals influence MPs abundance and characteristics. The Polymer Risk Index and Pollution Load Index indicated varying risk levels among the samples. These findings highlight the need to address MPs contamination in PGS to ensure ecosystem safety and human health.

Co-accumulation characteristics and interaction mechanism of microplastics and PFASs in a large shallow lake

Microplastics (MPs) and per- and polyfluoroalkyl substances (PFASs) coexist widely in lakes and affect ecological security. The coexistence characteristics and adsorption-desorption mechanisms between MPs and typical PFASs were explored in a typical eutrophic shallow lake (Taihu Lake). Polyvinyl chloride (PVC) and polyethylene (PE) are the primary types of MPs in Taihu Lake, with average abundances in water and sediment of 18630 n/m3 and 584 n/kg, respectively. The average concentrations of PFASs in water and sediment are 288.93 ng/L and 4.33 ng/g, with short-chain PFASs (C4-C7) being the main pollutants. Perfluorobutanoic acid (PFBA) in both water and sediment contributed 38.48 % and 44.53 %, respectively, followed by hexafluoropropylene oxide dimer acid (HFPO-DA). The morphological characteristics of MPs influence the distribution of long-chain PFAS in lake water, while the presence of HFPO-DA and perfluorohexanoic acid (PFHxA) in sediment is directly linked to the concentration and size of MPs. A combination of field investigations and indoor experiments revealed that the irreversible adsorption characteristics between MPs and HFPO-DA may promote the high cumulative flux of HFPO-DA in sediment, and the biofilm on the surface of MPs significantly accelerates this accumulation process. The results provide a new perspective on the co-transport behavior of emerging pollutants in aquatic environments.

Microplastics and PFAS air-water interaction and deposition

Although microplastics (MPs) and per- and polyfluoroalkyl substances (PFAS) have received tremendous attention separately, understanding their ubiquitous presence in the environment, persistence and toxicity requires comprehensive study of the fate and transport of co-existing MPs and PFAS. MPs may have large sorption capacity and can serve as vectors for PFAS to undergo long-range transport in water. Atmospheric deposition of both PFAS and MPs has been reported in urban, rural, and remote areas. This review identifies types and levels of PFAS and MPs in air, their interactions, and environmental factors contributing to their air-water deposition. MPs in combination with PFAS may carry combined toxicity and pose elevated risks to ecosystems and human health. Our review shows that air-water deposition of MPs and PFAS can be governed by environmental factors including precipitation, humidity, UV, wind, and particulate matter levels in the air. Increasing humidity may increase MP particle size due to hygroscopic growth, which affects its distribution and deposition rate. Humidity has been observed to have both positive and negative impacts on PFAS partitioning onto MPs. More attention should be paid to MPs and PFAS co-occurrence when addressing their transport behavior in air and deposition to aquatic systems.

Fate, distribution, and transport dynamics of Per- and Polyfluoroalkyl Substances (PFASs) in the environment

Per- and Polyfluoroalkyl Substances (PFASs) are persistent organic pollutants with significant environmental and health impacts due to their widespread occurrence, bioaccumulation potential, and resistance to degradation. This paper comprehensively reviews current knowledge of PFAS fate and transport mechanisms by correlating PFAS leaching, retention, and movement to their physicochemical properties and environmental factors based on observing PFAS fate and transport in unsaturated zones, surface water, sediments, plants, and atmosphere. The complex and unique physiochemical properties of PFASs, such as their carbon-fluorine bonds and amphiphilic nature, determine their environmental behavior and persistence. Recent studies emphasize that concentration-dependent affinity coefficients predict the transport of diverse PFAS mixtures by considering the impact of the Air-Water Interface (AWI). These studies highlight the complex interactions that influence PFAS behavior in environmental systems and the need for refined modeling techniques to account for transport dynamics. Competitive adsorption at the AWI, influenced by PFAS physicochemical properties and environmental factors, is crucial. PFAS chain length profoundly affects PFAS volatility and mobility, i.e., longer chains show higher solid matrix adsorption, while shorter chains exhibit greater atmospheric deposition potential. Solution chemistry, encompassing pH and ionic strength, variably alters PFAS sorption behaviors. Mathematical models, such as the Leverett Thermodynamic Model (LTM) and Surface Roughness Multipliers (SRM), effectively predict PFAS retention, offering enhanced accuracy for surface-active solutes through empirical adjustments. Co-contaminants' presence influences the transport behavior of PFASs in the environment. Microbial activity alters PFAS retention, while microplastics, especially polyamide, contribute to their adsorption. These complex interactions govern PFAS fate and transport in the environment. The paper identifies critical gaps in current understanding, including the fate of PFASs, analytical challenges, ecological risk assessment methods, and the influence of episodic events on PFAS transport dynamics. This paper also investigates the research gap in refining current models and experimental approaches to predict PFAS transport accurately and enhance risk mitigation efforts. Addressing these gaps is crucial for advancing remediation strategies and regulatory frameworks to mitigate PFAS contamination effectively.

Microplastics meet micropollutants in a central european river stream: Adsorption of pollutants to microplastics under environmentally relevant conditions

Microplastics have emerged as pervasive pollutants in aquatic environments, and their interaction with organic contaminants poses a significant environmental challenge. This study aimed to explore the adsorption of micropollutants onto microplastics in a river, examining different plastic materials and the effect of aging on adsorption capacity. Microplastics (low-density polyethylene (LDPE), polyethylene terephthalate (PET), and polyvinyl chloride (PVC)) were introduced into a river stream, and a comprehensive analysis involving 297 organic pollutants was conducted. Passive samplers were deployed to monitor micropollutant presence in the river. Sixty-four analytes were identified in the river flow, with telmisartan being the most prevalent. Nonaged PVC showed the highest telmisartan concentration at 279 ng/g (168 ng/m2 regarding the microplastic surface), while aged PVC exhibited a fourfold decrease. Conversely, aged LDPE preferentially adsorbed metoprolol and tramadol, with concentrations increasing 12- and 3-fold, respectively, compared to nonaged LDPE. Azithromycin and clarithromycin, positively charged compounds, exhibited higher sorption to PET microplastics, regardless of aging. Diclofenac showed higher concentrations on nonaged PVC compared to aged PVC. Aging induced structural changes in microplastics, including color alterations, smaller particle production, and increased specific surface area. These changes influenced micropollutant adsorption, with hydrophobicity, dissociation constants, and the ionic form of pollutants being key factors. Aged microplastics generally showed different sorption properties. A comparison of microplastics and control sand particles indicated preferential micropollutant sorption to microplastics, underscoring their role as vectors for contaminant transport in aquatic ecosystems. Analysis of river sediment emphasized the significance of contact time in pollutant accumulation. Overall, this study provides insights into the complex interactions between microplastics and organic pollutants under environmental conditions and contributes to a better understanding of the fate and behavior of these two types of contaminants in aquatic ecosystems.

Microplastics are effective carriers of bisphenol A and facilitate its escape from wastewater treatment systems

Microplastics (MPs) pollution is a major issue in aquatic environments. Wastewater treatment plants are significant point sources of MPs, which may also be carriers of organic pollutants. We analyzed MP number, shape, color, and polymer type distribution in sewage wastewater treatment plants. The potential of MPs to act as carriers for typical organic pollutants in sewage, such as bisphenol A (BPA), was also assessed. The predominant MPs in the influent were fibers, primarily transparent and black in color, and composed of polyethylene, polypropylene, and polystyrene. During wastewater treatment, the concentration of MPs decreased from 10.89 items per L in the influent to 0.89 items per L in the treated effluent, with significant differences in treatment efficiency at different stages. In the simulated wastewater, the three predominant MPs exhibited certain adsorption capacities for bisphenol A. Changing the temperature and pH within the range expected for wastewater could interfere with the interactions between MPs and bisphenol A, with a limited impact on adsorption. The results show that although wastewater treatment plants intercept a significant amount of MP, a considerable number of them enter the aquatic environment daily because of the high volume of wastewater discharge. These MPs, which carry pollutants such as bisphenol A, may threaten the health of fish and other aquatic organisms. However, by scientifically adjusting operational parameters, wastewater treatment plants could become "controllable sources" of MP compound pollutants.

Effect of Co-exposure to Additional Substances on the Bioconcentration of Per(poly)fluoroalkyl Substances: A Meta-Analysis Based on Hydroponic Experimental Evidence

A consensus has yet to emerge regarding the bioconcentration responses of per(poly)fluoroalkyl substances under co-exposure with other additional substances in aqueous environments. This study employed a meta-analysis to systematically investigate the aforementioned issues on the basis of 1,085 published datasets of indoor hydroponic simulation experiments. A hierarchical meta-analysis model with an embedded variance covariance matrix was constructed to eliminate the non-independence and shared controls of the data. Overall, the co-exposure resulted in a notable reduction in PFAS bioaccumulation (cumulative effect size, CES =  - 0.4287, p < 0.05) and bioconcentration factor (R2 = 0.9507, k < 1, b < 0) in hydroponics. In particular, the inhibition of PFAS bioconcentration induced by dissolved organic matter (percentage form of the effect size, ESP =  - 48.98%) was more pronounced than that induced by metal ions (ESP =  - 35.54%), particulate matter (ESP =  - 24.70%) and persistent organic pollutants (ESP =  - 18.66%). A lower AS concentration and a lower concentration ratio of ASs to PFASs significantly promote PFAS bioaccumulation (p < 0.05). The bioaccumulation of PFASs with long chains or high fluoride contents tended to be exacerbated in the presence of ASs. Furthermore, the effect on PFAS bioaccumulation was also significantly dependent on the duration of co-exposure (p < 0.05). The findings of this study provide novel insights into the fate and bioconcentration of PFAS in aquatic environments under co-exposure conditions.

The bioaccumulation and ecotoxicity of co-exposure of per(poly)fluoroalkyl substances and polystyrene microplastics to Eichhornia crassipes

Gen X and F-53B have been popularized as alternatives to PFOA and PFOS, respectively. These per(poly)fluoroalkyl substances pervasively coexist with microplastics (MPs) in aquatic environments. However, there are knowledge gaps regarding their potential eco-environmental risks. In this study, a typical free-floating macrophyte, Eichhornia crassipes (E. crassipes), was selected for hydroponic simulation of a single exposure to PFOA, PFOS, Gen X, and F-53B, and co-exposure with polystyrene (PS) microspheres. F-53B exhibited the highest bioaccumulation followed by Gen X, PFOA, and PFOS. In the presence of PS MPs, the bioavailabilities of the four PFASs shifted and the whole plant bioconcentration factors improved. All four PFASs induced severe lipid peroxidation, which was exacerbated by PS MPs. The highest integrated biomarker response (IBR) was observed for E. crassipes (IBR of shoot: 30.01, IBR of root: 22.79, and IBR of whole plant: 34.96) co-exposed to PS MPs and F-53B. The effect addition index (EAI) model revealed that PS MPs showed antagonistic toxicity with PFOA and PFOS (EAI < 0) and synergistic toxicity with Gen X and F-53B (EAI > 0). These results are helpful to compare the eco-environmental impacts of legacy and alternative PFASs for renewal process of PFAS consumption and provide toxicological, botanical, and ecoengineering insights under co-contamination with MPs.

Adsorption behaviors of perfluorooctanoic acid on aged microplastics

The presence of perfluoroalkyl substances (PFAS) in the environment poses a significant threat to ecological safety and environmental health. Widespread microplastics (MPs) have been recognized as vectors for emerging contaminants due to human activities. However, the adsorption behaviors of PFAS on MPs, especially on aged MPs, have not been extensively investigated. This study aimed to investigate the adsorption behaviors of perfluorooctanoic acid (PFOA) on aged MPs (polystyrene, polyethylene, and polyethylene terephthalate) treated with UV irradiation and persulfate oxidation under salinity and dissolve organic matter (DOM) condition. Carbonyl index values of MPs increased after the aged treatment, indicating the production of oxygen-containing groups. The PFOA adsorption on aged MPs was impacted by the co-existence of Na+ ions and DOM. As PFOA adsorption onto aged MPs was mainly controlled by hydrophobic interaction, the electrostatic interaction also made a contribution, but there was no significant change in PFOA adsorption behavior between the pristine and aged MPs. While these findings provide insight into PFAS adsorption on aged MPs, further research is necessary to account for the complexity of the real environment. PRACTITIONER POINTS: Adsorption behaviors of perfluorooctanoic acid (PFOA) on aged microplastics were investigated. Hydrophobic interaction mainly controlled PFOA adsorption on aged microplastics (MPs). Co-existence dissolve organic matter and salinity influenced PFOA adsorption behaviors on aged MPs.

Adsorption of PFAS onto secondary microplastics: A mechanistic study

Microplastics (MPs) are abundant in aquatic systems. The ecological risks of MPs may arise from their physical features, chemical properties, and/or their ability to concentrate and transport other contaminants, such as per- and polyfluoroalkyl substances (PFAS). PFAS have been extracted from MPs found in natural waters. Still, there needs to be a mechanistic investigation of the effect of PFAS chemistry and water physicochemical properties on how PFAS partition onto secondary MPs. Here, we studied the influence of pH, natural organic matter (NOM), ionic strength, and temperature on the adsorption of PFAS on MPs generated from PET water bottles. The adsorption of PFAS to the MPs was thermodynamically spontaneous at 25 °C, based on Gibb's free energy (ΔG = -16 to -23 kJ/mol), primarily due to increased entropy after adsorption. Adsorption reached equilibrium within 7-9 h. Hence, PFAS will partition to the surface of secondary PET MPs within hours in fresh and saline waters. Natural organic matter decreased the capacity of secondary PET MPs for PFAS through electrosteric repulsion, while higher ionic strength favored PFAS adsorption by decreasing electrostatic repulsion. Increased pH increased electrostatic repulsion, which negated PFAS adsorption. The study provides fundamental information for developing models to predict interactions between secondary MPs and PFAS.

Influence of microplastic contamination on the dissipation of endocrine disrupting chemicals in soil environment

Microplastic (MP) contamination is in the spotlight today, yet knowledge of their interaction with other organic contaminants in the soil environment is limited. Concerns extend to endocrine disrupting chemicals (EDCs), known for their potential to interfere with the hormonal systems of organisms and for their persistence and widespread presence in the environment. In this study, the most frequently occurring EDCs were monitored both in alluvial soil and in soil contaminated with different MPs commonly found in soil media, polyethylene, polyamide, and polystyrene. Bisphenol A and parabens were the most rapidly dissipating compounds, followed by triclosan and triclocarban, with the latter showing poor degradation. Per- and polyfluoroalkyl substances (PFAS) showed high persistence as concentrations remained nearly constant throughout the experiment. Although they fitted well with first-order dissipation kinetics, most showed biphasic behavior. The co-occurrence of MPs in the soil influenced the kinetic behavior in most cases although the differences were not very marked. MPs could impact sorption-desorption processes, affecting contaminant mobility and bioavailability to organisms in soil. These findings strengthen evidence for the influence of MPs on the behavior of soil contaminants such as EDCs, not only as vectors or sources of contaminants but by affecting dissipation kinetics.

Adsorption of Macrolide Antibiotics and a Metabolite onto Polyethylene Terephthalate and Polyethylene Microplastics in Aquatic Environments

Microplastics (MPs) and antibiotics are emerging pollutants widely found in aquatic environments, potentially causing environmental harm. MPs may act as carriers for antibiotics, affecting their environmental distribution. This study investigates the adsorption of four macrolide antibiotics and a metabolite onto two types of MPs: polyethylene terephthalate (PET) and polyethylene (PE). Results revealed a linear isotherm adsorption model, with higher adsorption to PET than to PE (R2 > 0.936 for PE and R2 > 0.910 for PET). Hydrophobic interactions and hydrogen bonding could be the main adsorption mechanisms, with pore filling potentially involved. Reduced particle size enhances adsorption due to the increase of active adsorption sites. This increasement is more pronounced in PE than in PET, leading to an 11.6% increase in the average adsorption of all macrolides to PE, compared to only 5.1% to PET. Dissolved organic matter inhibits adsorption (azithromycin adsorption to PE was reduced from 12% to 5.1%), while salinity enhances it just until 1% salinity. pH slightly influences adsorption, with maximal adsorption at neutral pH. Results in real samples showed that complexity of the matrix decreased adsorption. Overall, these findings indicate that PE and PET MPs can be a vector of macrolides in aquatic environments.

Effects of combined exposure of PVC and PFOA on the physiology and biochemistry of Microcystis aeruginosa

Microplastics (MPs) and per- and polyfluoroalkyl substances (PFASs) have drawn significant attention as emerging threats to aquatic ecosystems. There are currently just a few investigations on the combined toxicity of PFAS and MP on freshwater microalgae. In this research, the combined toxicity of polyvinyl chloride (PVC) and perfluorooctanoic acid (PFOA) to Microcystis aeruginosa was investigated. The results indicated that the combination of these pollutants inhibited the growth of M. aeruginosa and promoted the synthesis and release of Microcystin-LR (MC-LR). Individual and combined exposure caused different responses to cellular oxidative stress. Under the Individual exposure of PFOA, when the concentration was greater than 20.0 mg/L, the catalase (CAT) activity increased significantly, and when it was greater than 100.0 mg/L, the malondialdehyde (MDA) content increased significantly, but there is no significant change under combined exposure. PVC and PFOA exposure also caused physical damage to the algal cells and reduced the content of extracellular polymer substances (EPS) based on analysis of cell morphology. Metabolic analysis revealed that carbohydrate metabolism and amino acid metabolism of the algae were affected. The current study offers a fresh theoretical framework for MPs and PFASs environmental risk evaluations.

A review on the occurrence, analytical methods, and impact of microplastics in the environment

Nowadays, microplastic pollution is one of the globally urgent concerns as a result of discharging plastic products into the atmosphere, aquatic and soil environments. Microplastics have average size of less than 5 mm, are non-biodegradable, accumulative, and highly persistent substances. Thousands of tons of microplastics are still accumulated in various environments, posing an enormous threat to human health and living creatures. Here, we review the occurrence and analytical methods, and impact of microplastics in the environments including soil, aquatic media, and atmosphere. Analytical methods including visual observation, Fourier-transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy, and pyrolysis-gas chromatography-mass spectrometry were evaluated. We elucidated the environmental and human health impacts of microplastics with emphasis on life malfunction, immune disruption, neurotoxicity, diseases and other tangible health risks. This review also found some shortages of analytical equivalence and/or standardization, inconsistence in sampling collection and limited knowledge of microplastic toxicity. It is hopeful that the present work not only affords a more insight into the potential dangers of microplastics on human health but also urges future researches to establish new standardizations in analytical methods.