Surface functional groups determine adsorption of pharmaceuticals and personal care products on polypropylene microplastics

Laser Direct Infrared Spectroscopy: A cutting-edge approach to microplastic detection in environmental samples

Microplastic pollution has emerged as a significant global environmental concern, affecting marine, terrestrial, and atmospheric ecosystems. As microplastic contamination continues to intensify, the need for precise, efficient, and scalable detection method is growing. This review highlights recent advancements in microplastic detection technologies, with a particular focus on Laser Direct Infrared (LDIR) spectroscopy. Utilizing a Quantum Cascade Laser (QCL), LDIR offers rapid, sensitive, and automated detection capabilities. It significantly reduces analysis time compared to conventional techniques such as Fourier Transform Infrared (FTIR) and Raman spectroscopic techniques, making it ideal for large-scale environmental monitoring. Its ability to identify particles as small as 10 μm, combined with enhanced wavelength accuracy, positions LDIR as a promising tool for microplastic analysis across various environmental matrices. Despite some limitations, such as a narrower spectral range, LDIR's superior speed and precision make it a critical advancement for understanding and addressing the global microplastic crisis.

A comprehensive review of microplastic aging: Laboratory simulations, physicochemical properties, adsorption mechanisms, and environmental impacts

As a new type of ecological environment problem, microplastic pollution is a severe challenge faced by the world, and its threat and potential risk to the ecosystem have become a hot research spot in the current environmental field. Microplastics (MPs) in the natural environment will experience aging effect, aging will change the physical and chemical properties of MPs and affect the adsorption behavior. Recently reported characterization techniques of MPs and laboratory simulation of aging are reviewed. The aging mechanism between MPs and different pollutants and the intervention mechanism of environmental factors (MPs, pollutants and water quality environment) were revealed. In addition, to further understand the potential ecological toxicity of MPs after aging, the release and harm of additives during aging, produce the environmentally persistent free radicals, and the mechanism of reactive oxygen species (ROS) removal of pollutants adsorbed on the surface of MPs were summarized. Future research efforts should focus more on bridging the disparity between laboratory aging simulations and natural environmental conditions to enhance the authenticity and ecological relevance of such studies. The ROS production mechanism of MPs provides a reference direction for removing pollutants adsorbed by aged MPs.

A critical review of microplastics in the shrimp farming environment: Incidence, characteristics, effects, and a first mass balance model

This review provides a critical overview of the sources, incidence, accumulation, effects, and interactions of microplastics (MPs) with other contaminants in the shrimp aquaculture environment, emphasizing this sector's challenges and future implications. A first and novel mass MPs balance model was developed to explore the fate and fluxes of MPs within shrimp farming systems. Two literature searches were conducted: one focused on MPs, crustaceans, and shrimp in aquaculture, and other on the effects of MPs in crustaceans, emphasizing shrimp. A total of 78 and 461 peer-reviewed papers were retrieved, respectively. This review details aspects of MPs in the shrimp farming environment, including water, sediments, food, zooplankton, and shrimp tissues. MPs can act as vectors for contaminants, including biological and chemical substances commonly used in shrimp aquaculture. A primary concern is the interaction between MPs and pathogens; thus MPs can facilitate the transport and retention of disease-causing agents. Key questions involve identifying which pathogen groups are most efficiently transported by MPs and how this may exacerbate disease outbreaks in aquaculture. This suggests that microorganisms can establish on MPs surfaces to disseminate an infection. Therefore, the possibility of disease outbreaks and epidemics is expected to rise as MP abundance increases. The mass balance shows that the primary source of MPs is associated with water during the filled (19.3 %) and water exchange (77.2 %) of shrimp ponds, indicating that MPs in the water input play a critical role in the MP dynamic in the shrimp farming environment. However, this initial mass balance model has several weaknesses, including liming, atmospheric deposition, and natural food, which must be addressed as other MPs suppliers. Macrofauna that incidentally enters shrimp ponds may also constitute a significant part of the MPs inventory. Future research should focus on the impact of polystyrene and polyethylene fibers commonly found in crustacean tissues.

Reductive soil disinfestation influences microbial aging of low-density polyethylene and polyhydroxyalkanoate microplastics and microbial communities in plastispheres

The extensive use of plastic products has led to the accumulation of microplastics (MPs) in agricultural soils, raising concerns about their fate in various environments. Reductive soil disinfestation (RSD) treatment is increasingly being adopted in various countries to address agricultural soil health issues. However, the treatment can alter the soil microbial environment, potentially affecting the fate of contaminants, including MPs. The effect of RSD on the aging of low-density polyethylene (LDPE) and polyhydroxyalkanoates (PHA) MPs was studied through an incubation experiment. The mechanism involved was further investigated by microbial community analysis. The characterization results shown that RSD treatment inhibited the aging of LDPE but promoted the aging of PHA. The results indicated that RSD reshaped the microbial community and reduced the relative abundance of lipid metabolism in the LDPE plastisphere, thereby hindering LDPE aging. Predicted functional genes in the plastispheres were primarily involved in metabolism (77.15-87.48%) and genetic information processing (8.774-12.62%). The enrichment of bacteria related to poly(3-hydroxybutyrate) depolymerase (phaZ) in the PHA plastisphere explained the higher aging degree of PHA during RSD. Some fungus also involved in the MPs aging, while some fungus pathogens can proliferate in the MPs plastispheres. The 3DEEM analysis indicated that PHA MPs aging increased tyrosine-like substances in soil extracts. These findings provide new insights into the ecological implications of RSD and enhance our understanding of microbial communities within plastispheres.

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.

Hydrophobic ZIF-8 nanoparticles loaded on chitosan for improved methanol adsorption from fermented wine

Metal-organic frameworks (MOFs) have great potential for the adsorption of minor molecular alcohols in the vapor phase. However, the drawbacks of powdered MOFs, including low recyclability and problematic separation, limit their application in fermented wine. Chitosan (CS) is a low-cost, eco-friendly, moldable matrix used in the food industry. In this study, a novel CS@ZIF-8 adsorbent with excellent microporous surface area was successfully synthesized by incorporating hydrophobic ZIF-8 into CS. The results showed that CS@ZIF-8 beads had a high adsorption affinity for methanol at a Zn2+/2-methylimidazole molar ratio of 1:5. The adsorption mechanism of methanol on CS@ZIF-8 beads was systematically studied by X-ray photoelectron spectroscopy, isotherms, and kinetics. The Langmuir model calculated the maximum adsorption of methanol to 56.8 mg/g. Adsorption kinetics are consistent with pseudo-second-order models. Furthermore, CS@ZIF-8 beads presented excellent recyclability for removing methanol for five consecutive cycles. It could treat 60 bed volumes of Chinese yellow wine in column filtration experiments to make the concentration below 50 mg/L. In summary, the highly efficient CS@ZIF-8 adsorbent has great potential for methanol adsorption from fermented wines. PRACTICAL APPLICATION: Methanol will exhibit adverse symptoms such as weakness and headaches after it is ingested. Therefore, methanol control is an important safety factor in the production of fermented wine. The adsorption method is recognized as a widely used technique due to its high efficiency and selectivity. The CS@ZIF-8 adsorbent synthesized in this paper provides a new idea for methanol removal.

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.

Isolation and Identification of Four Strains of Bacteria with Potential to Biodegrade Polyethylene and Polypropylene from Mangrove

With the rapid growth of global plastic production, the degradation of microplastics (MPs) has received widespread attention, and the search for efficient biodegradation pathways has become a hot topic. The aim of this study was to screen mangrove sediment and surface water for bacteria capable of degrading polyethylene (PE) and polypropylene (PP) MPs. In this study, two strains of PE-degrading bacteria and two strains of PP-degrading candidate bacteria were obtained from mangrove, named Pseudomonas sp. strain GIA7, Bacillus cereus strain GIA17, Acinetobacter sp. strain GIB8, and Bacillus cereus strain GIB10. The results showed that the degradation rate of the bacteria increased gradually with the increase in degradation time for 60 days. Most of the MP-degrading bacteria had higher degradation rates in the presence of weak acid. The appropriate addition of Mg2+ and K+ was favorable to improve the degradation rate of MPs. Interestingly, high salt concentration inhibited the biodegradation of MPs. Results of scanning electron microscopy (SEM), atomic force microscopy (AFM), and Fourier-transform infrared spectroscopy (FTIR) indicated the degradation and surface changes of PP and PE MPs caused by candidate bacteria, which may depend on the biodegradation-related enzymes laccase and lipase. Our results indicated that these four bacterial strains may contribute to the biodegradation of MPs in the mangrove environment.

Application of metal-organic frameworks for photocatalytic degradation of microplastics: Design, challenges, and scope

Microplastics (MPs), plastic particles smaller than 5 mm, are pervasive pollutants challenging wastewater treatment due to their size and hydrophobicity. They infiltrate freshwater, marine, and soil environments, posing ecological threats. In marine settings, MPs ingested by organisms cause cytokine release, cellular and DNA damage, and inflammation. As MPs enter the food chain and disrupt biological processes, their degradation is crucial. While biodegradation, pyrolysis, and chemical methods have been extensively studied, the use of metal-organic frameworks (MOFs) for MP pollution mitigation is underexplored. In this study, we explored the photocatalytic degradation mechanisms of MPs by MOFs in aquatic environments. We analyzed the hydrolysis, oxidation, and adsorption processes, while focusing on the environmentally friendly and cost-effective photocatalytic approach. Additionally, we analyzed the literature on MP decomposition for various types of MOFs, providing a detailed understanding of the degradation mechanisms specific to each MOF. Furthermore, we evaluated the degradation efficiencies of different MOFs and discussed the challenges and limitations in their application. Our study highlights the need for an integrated approach that involves the application of MOFs while considering environmental factors and safety concerns to develop effective MP degradation models. This review provides a framework for developing reliable photocatalytic materials with high MP removal and degradation efficiencies, thereby promoting the use of MOFs for marine plastic pollution mitigation.

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

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

A QSAR prediction model for adsorption of organic contaminants on microplastics: Dubinin-Astakhov plus linear solvation energy relationships

Numerous pharmaceuticals and personal care products (PPCPs) co-exist with various types of microplastics (MPs) in the environment, making it extremely hard to experimentally measure all their adsorption interactions. Thus, a precise prediction model is on demand. In this study, we combined the commonly used Dubinin-Astakhov (DA) model and the linear solvation energy relationships (LSERs) model to predict the adsorption capacity (Q0) and adsorption affinity (E) of MPs for PPCPs, including the key parameters of MP (specific surface area, oxygen-containing functional groups), and the Kamlet-Taft solvation parameters of organic contaminants. The model was validated with the experimental data of 8 PPCPs and 8 MPs (i.e. pristine and aged PE, PET, PS, PVC) plus some published adsorption data. This new model also indicated that the adsorption of PPCPs on those MPs was primarily governed by hydrophobic interaction and hydrogen bonding. The developed model can predict the adsorption of PPCPs onto MPs with a high accuracy and can also provide insights into the understanding of interaction forces in the adsorption process.

Nitrogen-doped mesoporous activated carbon from Lentinus edodes residue: an optimized adsorbent for pharmaceuticals in aqueous solutions

In this study, phosphoric acid activation was employed to synthesize nitrogen-doped mesoporous activated carbon (designated as MR1) from Lentinus edodes (shiitake mushroom) residue, while aiming to efficiently remove acetaminophen (APAP), carbamazepine (CBZ), and metronidazole (MNZ) from aqueous solutions. We characterized the physicochemical properties of the produced adsorbents using scanning electron microscopy (SEM), nitrogen adsorption isotherms, and X-ray photoelectron spectroscopy (XPS). MR1, MR2, and MR3 were prepared using phosphoric acid impregnation ratios of 1, 2, and 3 mL/g, respectively. Notably, MR1 exhibited a significant mesoporous structure with a volume of 0.825 cm3/g and a quaternary nitrogen content of 2.6%. This endowed MR1 with a high adsorption capacity for APAP, CBZ, and MNZ, positioning it as a promising candidate for water purification applications. The adsorption behavior of the contaminants followed the Freundlich isotherm model, suggesting a multilayer adsorption process. Notably, MR1 showed excellent durability and recyclability, maintaining 95% of its initial adsorption efficiency after five regeneration cycles and indicating its potential for sustainable use in water treatment processes.

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.

Groundwater systems under siege: The silent invasion of microplastics and cock-tails worldwide

Microplastics (MPs) contamination is one of the significant escalating environmental concerns worldwide, and this stems from the increasing production and unlawful disposal of plastic materials. Regretfully, the synthesis of plastic materials is expected to triple in the upcoming years. Nevertheless, MPs pollution in marine, aquatic, and terrestrial settings has received much attention, unlike in groundwater systems. This study exhaustively reviewed varying degrees of recent publications in various search engines and provided a detailed state of current knowledge and research progress vis-à-vis MPs and cock-tail pollution in groundwater systems. Evidently, groundwater sources are severely contaminated as a result of growing anthropogenic activities and vertical movement of MPs and cock-tails from the atmospheric, terrestrial, and aquatic environments, however, fewer researchers have fixated their attention on estimating the occurrence of MPs in groundwater resources, while sufficient information regarding their sources, sampling methods, abundance, transport pathways, fate, modeling techniques, appropriate and adequate data, sorption properties, separation from other environmental media, toxicity, and remedial measures are extensively lacking. In addition, MPs may combine with other toxic emerging contaminants to improve migration and toxicity; however, no research has been conducted to fully understand cock-tail migration mechanisms and impacts in groundwater systems. Over time, groundwater may be regarded as the primary sink for MPs, if effective actions are neglected. Overall, this study detected a lack of concern and innumerable voids in this field; hence, vital and nascent research gaps were identified for immediate, advanced, and interdisciplinary research investigations.

Implications of polystyrene and polyamide microplastics in the adsorption of sulfonamide antibiotics and their metabolites in water matrices

Microplastics (MP) and antibiotics coexist in the environment and their combined exposure represents a source of increasing concern. MP may act as carriers of antibiotics because of their sorption capacity. Knowledge of the interactions between them may help improve understanding of their migration and transformation. In this work, the adsorption behaviour of a group of sulfonamides and their acetylated metabolites on different sizes of polyamide (PA) and polystyrene (PS) MP were investigated and compared. Sulfonamides were adsorbed on both MP (qmax up to 0.699 and 0.184 mg/g, for PA and PS, respectively) fitting to a linear isotherm model (R2 > 0.835). A low particle size and an acidic and salinity medium significantly enhances the adsorption capacity of sulfonamides (i.e. removal of sulfamethoxazole increased from 8 % onto 3 mm PA pellets to 80 % onto 50 mm of PA pellets). According to characterization results, adsorption mechanism is explained by pore filling and hydrogen bonds (for PA) and hydrophobic interactions (for PS). After adsorption, surface area was increased in both MP as result of a potential ageing of the particles and the intensity of XRD peaks was higher denoting a MP structure more amorphized. Metabolites were adsorbed more efficiently than their parent compounds on PS while the opposite effect was observed on PA explained by the acetylation of the amine group and, subsequently the reduction of hydrogen bond interactions. Although the dissolved organic matter inhibits sulfonamides adsorption, removal up to 65.2 % in effluent wastewater and up to 72.1 % in surface water were observed in experiments using real matrices denoting the role of MP as vectors of sulfonamide antibiotics in aquatic media.

Cotransport of nanoplastics and plastic additive bisphenol AF (BPAF) in unsaturated hyporheic zone: Coupling effects of surface functionalization and protein corona

The ecological risk of combined pollution from microplastics (MPs) and associated contaminants usually depends on their interactions and environmental behavior, which was also disturbed by varying surface modifications of MPs. In this study, the significance of surface functionalization and protein-corona on the cotransport of nanoplastics (NPs; 100 nm) and the related additive bisphenol AF (BPAF) was examined in simulated unsaturated hyporheic zone (quartz sand; 250-425 μm). The electronegative bovine serum albumin (BSA) and electropositive trypsin were chosen as representative proteins, while pristine (PNPs), amino-modified (ANPs), and carboxyl-modified NPs (CNPs) were representative NPs with different charges. The presence of BPAF inhibited the mobility of PNPs/CNPs, but enhanced the release of ANPs in hyporheic zone, which was mainly related to their hydrophobicity changes and electrostatic interactions. Meanwhile, the NPs with high mobility and strong affinity to BPAF became effective carriers, promoting the cotransport of BPAF by 16.4 %-26.4 %. The formation of protein-coronas altered the mobility of NPs alone and their cotransport with BPAF, exhibiting a coupling effect with functional groups. BSA-corona promoted the transport of PNPs/CNPs, but this promoting effect was weakened by the presence of BPAF via increasing particle aggregation and hydrophobicity. Inversely, trypsin-corona aggravated the deposition of PNPs/CNPs, but competition deposition sites and increased energy barrier caused by coexisting BPAF reversed this effect, facilitating the cotransport of trypsin-PNPs/CNPs in hyporheic zone. However, BPAF and protein-coronas synergistically promoted the mobility of ANPs, owing to competition deposition sites and decreased electrostatic attraction. Although all of the NPs with two protein-coronas reduced dissolved BPAF in the effluents via providing deposition sites, the cotransport of total BPAF was improved by the NPs with high mobility (BSA-PNPs/CNPs) or high affinity to BPAF (BSA/trypsin-ANPs). However, the trypsin-PNPs/CNPs inhibited the transport of BPAF due to their weak mobility and adsorption with BPAF. The results provide new insights into the role of varying surface modifications on NPs in the vertical cotransport of NPs and associated contaminants in unsaturated hyporheic zone.

How do polystyrene microplastics affect the adsorption of copper in soil?

Microplastics (MPs) commonly coexist with heavy metals in the soil environment. MPs can influence the activity of heavy metals, and the specific mechanisms need to be further explored. Here, different contents of polystyrene (PS) MPs were added to soil to explore their effects on the adsorption and desorption characteristics of copper (Cu2+) in soil. The adsorption process was mainly chemical adsorption and belonged to a spontaneous, endothermic reaction. The hydrophobicity of MPs slowed down the adsorption and desorption rates. The main adsorption mechanisms included complexation by oxygen-containing functional groups, ion exchange (accounting for 33.97-36.04 % of the total adsorption amounts), and electrostatic interactions. MPs lacked oxygen-containing functional groups and were predominantly engaged in ion exchange and electrostatic interactions. MPs diluted, blocked the soil, and covered the active sites of soil, which reduced adsorption (3.56-16.18 %) and increased desorption (0.90-2.07 %) of Cu2+ in soil samples, thus increasing the activity and mobility of Cu2+. These findings provide new insights into the effects of MPs on the fate and risk of heavy metals in soil. ENVIRONMENTAL IMPLICATION: The existing literature concerning the effects of microplastics on the adsorption of heavy metals in soil is insufficient. Our investigation unveiled that the main adsorption mechanisms of different soil samples included complexation by oxygen-containing functional groups, ion exchange (accounting for 33.97-36.04 % of the total adsorption amounts), and electrostatic interactions. MPs lacked oxygen-containing functional groups and were predominantly engaged in ion exchange and electrostatic interactions. MPs diluted, blocked the soil, and covered the active sites of soil, which reduced adsorption (3.56-16.18 %) and increased desorption (0.90-2.07 %) of Cu2+ in soil samples, thus increasing the activity and mobility of Cu2+.

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.

Surface functional groups on nanoplastics delay the recovery of gut microbiota after combined exposure to sulfamethazine in marine medaka (Oryzias melastigma)

Nanoplastics can interact with antibiotics, altering their bioavailability and the ensuing toxicity in marine organisms. It is reported that plain polystyrene (PS) nanoplastics decrease the bioavailability and adverse effects of sulfamethazine (SMZ) on the gut microbiota in Oryzias melastigma. However, the influence of surface functional groups on the combined effects with SMZ remains largely unknown. In this study, adult O. melastigma were fed diet amended with 4.62 mg/g SMZ and 3.65 mg/g nanoplastics (i.e., plain PS, PS-COOH and PS-NH2) for 30 days (F0-E), followed by a depuration period of 21 days (F0-D). In addition, the eggs produced on the last day of exposure were cultured under standard protocols without further exposure for 2 months (F1 fish). The results showed that the alpha diversity or the bacterial community of gut microbiota did not differ among the SMZ + PS, SMZ + PS-COOH, and SMZ + PS-NH2 groups in the F0-E and F1 fish. Interestingly, during the depuration, a clear recovery of gut microbiota (e.g., increases in the alpha diversity, beneficial bacteria abundances and network complexity) was found in the SMZ + PS group, but not for the SMZ + PS-COOH and SMZ + PS-NH2 groups, indicating that PS-COOH and PS-NH2 could prolong the toxic effect of SMZ and hinder the recovery of gut microbiota. Compared to plain PS, lower egestion rates of PS-COOH and PS-NH2 were observed in O. melastigma. In addition, under the simulated fish digest conditions, the SMZ-loaded PS-NH2 was found to desorb more SMZ than the loaded PS and PS-COOH. These results suggested that the surface -COOH and -NH2 groups on PS could influence their egestion efficiency and the adsorption/desorption behavior with SMZ, resulting in a long-lasting SMZ stress in the gut during the depuration phase. Our findings highlight the complexity of the carrier effect and ecological risk of surface-charged nanoplastics and the interactions between nanoplastics and antibiotics in natural environments.

Mineralization characteristics and behavior of polyethylene microplastics through ozone-based treatment

The elimination of microplastics (MPs) has become an urgent issue due to their large quantities and imperfect treatment technologies. In this work, polyethylene (PE), which is ubiquitous in the environment, was selected to study its removal by ozone-based treatment. Catalysts including α-MnO2 and α-FeOOH were synthesized for catalytic ozonation to improve efficiency. The study focused on simulating the conversion of CO2 in the off-gas via the detection of inorganic carbon produced. The morphology and structure of the remaining PE MPs were characterized using scanning electron microscope and Fourier-transform infrared spectroscopy-attenuated total reflection. Our results confirmed that fragmentation and oxidation occurred in the remaining PE MPs, which enhanced the adsorption capacity of ofloxacin (OF). Besides, the 20 mM α-FeOOH could better improve the mineralization efficiency by 3.27 folds with more production of •OH (1.09*10-12 M). Moreover, possible products identified by liquid chromatography-time-of-flight mass spectrometer confirmed the decomposition of main chains of MPs into low-molecular-weight organic compounds with functional groups such as C-OH, C-O-C, and CO. The finding that photoaged PE MPs could be efficiently mineralized under the attack of O3/•OH provides a solid foundation for the removal of natural MPs in the environment.

Effects of microplastic properties and dissolved organic matter on phosphorus availability in soil and aqueous mediums

Plastic mulching films and phosphate fertilizers have been widely used to improve agricultural soil productivity. Microplastics (MP) and phosphorus (P) significantly accumulate in agricultural soil and water bodies. However, the effects of residual MP on P availability in soil and aqueous mediums remain unclear. In this study, available P (Olsen-P) in soils and P adsorption capacity in aqueous medium were determined to examine the influence of MP properties on P availability in laboratory. In agricultural soils, Olsen-P was significantly affected by MP types. Conventional MP (mulching film particles), such as polyethylene (PE) and polyvinyl chloride (PVC), and biodegradable MP, such as polylactic acid (PLA), substantially reduced soil Olsen-P by 9.7-38.6% and 38.4-73.6%, respectively. The size and concentration of MP strongly affected soil Olsen-P, with smaller (25 μm) and more concentrated (5%) MP causing greater reductions in Olsen-P. In the soil contaminated with MP, increased fulvic acid content significantly increased Olsen-P levels. Microplastics exhibited strong P adsorption capacities, leading to decreased P availability in aqueous medium. Conventional MP exhibited a higher P adsorption capacity than biodegradable MP, with P distribution coefficients (Kd values) ordered as PVC (5.19 L kg-1) > PE (4.23 L kg-1) > PLA (2.48 L kg-1). Notably, the Kd values increased with decreasing sizes of conventional MP, whereas the opposite trend was observed for PLA. The presence of fulvic acid affected the adsorption of P by MP in aqueous medium. Increased fulvic acid content reduced P adsorption capacity of MP, thus enhancing P availability. Our findings contribute to a better understanding of P dynamics in MP-contaminated agricultural soil and aqueous medium, which could aid in formulating sustainable agricultural practices and effective environmental management strategies for plastic mulching films and P contamination.

The comparative effects of visible light and UV-A radiation on the combined toxicity of P25 TiO2 nanoparticles and polystyrene microplastics on Chlorella sp

The ubiquitous presence of TiO2 nanoparticles (nTiO2) and microplastics (MPs) in marine ecosystems has raised serious concerns about their combined impact on marine biota. This study investigated the combined toxic effect of nTiO2 (1 mg/L) and NH2 and COOH surface functionalized polystyrene MPs (PSMPs) (2.5 and 10 mg/L) on Chlorella sp. All the experiments were carried out under both visible light and UV-A radiation conditions to elucidate the impact of light on the combined toxicity of these pollutants. Growth inhibition results indicated that pristine nTiO2 exhibited a more toxic effect (38%) under UV-A radiation when compared to visible light conditions (27%). However, no significant change in the growth inhibitory effects of pristine PSMPs was observed between visible light and UVA radiation conditions. The combined pollutants (nTiO2 + 10 mg/L PSMPs) under UV-A radiation exhibited more growth inhibition (nTiO2 + NH2 PSMPs 66%; nTiO2 + COOH PSMPs 50%) than under visible light conditions (nTiO2 + NH2 PSMPs 55%; TiO2 + COOH PSMPs 44%). Independent action modeling indicated that the mixture of nTiO2 with PSMPs (10 mg/L) exhibited an additive effect on the algal growth inhibition under both the light conditions. The photoactive nTiO2 promoted increased production of reactive oxygen species under UV-A exposure, resulting in cellular damage, lipid peroxidation, and impaired photosynthesis. The effects were more pronounced in case of the mixtures where PSMPs added to the oxidative stress. The toxic effects of the binary mixtures of nTiO2 and PSMPs were further confirmed through the field emission electron microscopy, revealing specific morphological abnormalities. This study provides valuable insights into the potential risks associated with the combination of nTiO2 and MPs in marine environments, considering the influence of environmentally relevant light conditions and the test medium.

High-performance biochar-loaded MgAl-layered double oxide adsorbents derived from sewage sludge towards nanoplastics removal: Mechanism elucidation and QSAR modeling

Utilization of sewage sludge for the fabrication of environmental functional materials is highly desirable to achieve pollution mitigation and resource recovery. In the present work, we introduced a novel MgAl-layered double oxide (LDO)@biochar composite adsorbent in-situ fabricated from Al-rich sewage sludge, and its excellent application in nanoplastics adsorption. Initially, fifteen model contaminants with varied conjugate structures, hydrogen bonding and ionic properties were selected for an investigation of adsorption behavior and adsorption selectivity on LDO@biochar. Structural variation of LDO@biochar suggested reconstruction of the layered double hydroxide (LDH) during the adsorption process due to the "memory effect". Under the synergy of LDH and biochar, the contaminants were adsorbed via multiple adsorbent-adsorbate interactions, including anion exchange, electrostatic interaction, hydrogen bonding and π-π conjugation. Then, a quantitative structure-activity relationship (QSAR) model was constructed by integrating the number of hydrogen bond acceptors, polarity surface area, number of aromatic rings, and Fukui index f(-)x together to reflect the affinity of each contaminant to the adsorbent. Guided by the QSAR model, the negatively charged polystyrene nanoplastics with continuously conjugated aromatic rings were predicted to be effectively adsorbed on LDO@biochar. Experimental tests confirmed a great capacity of LDO@biochar towards the polystyrene nanoplastics, given the equilibrium adsorption capacity as high as 360 mg g-1 at 30-50 °C. This work not only opened up a new avenue for sustainable utilization of sewage sludge towards high-performance environmental functional materials, but also demonstrated the potential of the QSAR analysis as a rapid and accurate approach for guiding the application of an adsorbent to new emerging containments.

Interactions between microplastics and contaminants: A review focusing on the effect of aging process

Microplastics (MPs) in the environment are a major global concern due to their persistent nature and wide distribution. The aging of MPs is influenced by several processes including photodegradation, thermal degradation, biodegradation and mechanical fragmentation, which affect their interaction with contaminants. This comprehensive review aims to summarize the aging process of MPs and the factors that impact their aging, and to discuss the effects of aging on the interaction of MPs with contaminants. A range of characterization methods that can effectively elucidate the mechanistic processes of these interactions are outlined. The rate and extent of MPs aging are influenced by their physicochemical properties and other environmental factors, which ultimately affect the adsorption and aggregation of aged MPs with environmental contaminants. Pollutants such as heavy metals, organic matter and microorganisms have a tendency to accumulate on MPs through adsorption and the interactions between them impact their environmental behavior. Aging enhances the specific surface area and oxygen-containing functional groups of MPs, thereby affecting the mechanism of interaction between MPs and contaminants. To obtain a more comprehensive understanding of how aging affects the interactions, this review also provides an overview of the mechanisms by which MPs interact with contaminants. In the future, there should be further in-depth studies of the potential hazards of aged MPs in different environments e.g., soil, sediment, aquatic environment, and effects of their interaction with environmental pollutants on human health and ecology.

Analyzing disinfection by-products yield and mechanisms in UV/Cl2 using response surface methodology and quantitative structure-activity relationship models

The study aimed to investigate the formation of halogenated disinfection byproducts (DBPs) during applying UV/chlorine (UV/Cl2) and unravel the interactive impacts of critical operational parameters and the mechanisms behind DBPs formation. Response surface methodology and quantitative structure-activity relationship models were developed to evaluate the contribution of electrophilic, nucleophilic, and free radical reactions to the formation of DBPs in UV/Cl2. The study found that Cl2 and its interactions dominated the total DBPs and non-Br-DBPs formation, while Br- and the Cl2-Br- interaction played a decisive role in the Br-DBPs formation. The study also observed significant interactions of Br, Cl2, and pH on chloroform, bromodichloromethane, dichloroacetonitrile, 1,1-dichloro-2-propanone, trichloroactic acid, and chlorodibromoacetic acid formations, while no evident interaction on chloral hydrate, dibromochloromethane, trichloroacetone, dibromoacetic acid, and bromodichloroacetic acid formations. The electrophilic substitution of HOBr mainly controlled the formation of trihalomethanes, and the contribution of nucleophilic, electrophilic, and free radical (•OH, Cl•, Cl2•- and ClO•) reactions depended on the molar ratio of Cl2 to Br, and pH-determined hydrolysis rate constants of DBPs and the types of free radicals. Overall, the response surface methodology and quantitative structure-activity relationship models provided a reference for revealing DBPs formation mechanisms in other disinfection processes.

Effect of Polymer Aging on Uptake/Release Kinetics of Metal Ions and Organic Molecules by Micro- and Nanoplastics: Implications for the Bioavailability of the Associated Compounds

The main driver of the potential toxicity of micro- and nanoplastics toward biota is often the release of compounds initially present in the plastic, i.e., polymer additives, as well as environmentally acquired metals and/or organic contaminants. Plastic particles degrade in the environment via various mechanisms and at different rates depending on the particle size/geometry, polymer type, and the prevailing physical and chemical conditions. The rate and extent of polymer degradation have obvious consequences for the uptake/release kinetics and, thus, the bioavailability of compounds associated with plastic particles. Herein, we develop a theoretical framework to describe the uptake and release kinetics of metal ions and organic compounds by plastic particles and apply it to the analysis of experimental data for pristine and aged micro- and nanoplastics. In particular, we elucidate the contribution of transient processes to the overall kinetics of plastic reactivity toward aquatic contaminants and demonstrate the paramount importance of intraparticulate contaminant diffusion.

How effective is biological activated carbon in removing micropollutants? A comprehensive review

Micropollutants (MPs), also called emerging contaminants, are detected in various environmental compartments. Wastewater is their main entry pathway due to the incomplete removal of MPs in wastewater treatment plants (WWTPs). These contaminants are a risk to human health and the integrity of the ecosystem because they are persistent and toxic to organisms. Complementary treatments such as adsorption are studied to increase the efficiency of existing WWTPs. However, a disadvantage of using activated carbon is its high cost of production and regeneration. Biological activated carbon (BAC) is an alternative to overpass this scenario. In BAC, biofilm development occurs on the surface of activated carbon, which enables bioregeneration of the adsorbent and extends its lifetime. This review focused on the studies that applied BAC to remove MPs in aqueous matrices. The review methodology was based on bibliometric and systematic analysis. Tables and thematic maps were presented to investigate trends and gaps in research and related themes. The study points out the leading MPs researched in adsorption in the last ten years. The systematic analysis showed that most studies bring sequential treatments with real wastewater/water, in which BAC is the final process. BAC has the potential to be a complementary treatment for removing MPs. However, there is a lack of articles investigating only BAC as the main tertiary treatment. Topics that should be further investigated in this area are the microbiological community formed in the biofilm, the column's lifetime, and the cost analysis of BAC implementation and operation.

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.

Degradation of ciprofloxacin by persulfate activated by Fe(III)-doped BiOCl composite photocatalyst

Fe-BOC-X photocatalyst was successfully prepared by solvothermal method. The photocatalytic activity of Fe-BOC-X was determined by ciprofloxacin (CIP), a typical fluoroquinolone antibiotic. Under sunlight irradiation, all Fe-BOC-X showed better CIP removal performance than original BiOCl. In comparison, the photocatalyst with iron content of 50 wt% (Fe-BOC-3) has excellent structural stability and the best adsorption photodegradation efficiency. The removal rate of CIP (10 mg/L) by Fe-BOC-3 (0.6 g/L) reached 81.4% within 90 min. At the same time, the effects of photocatalyst dosage, pH, persulfate, persulfate concentration, and combinations of different systems (PS, Fe-BOC-3, Vis/PS, Vis/Fe-BOC-3, Fe-BOC-3/PS, and Vis/Fe-BOC-3/PS) on the reaction were systematically discussed. In reactive species trapping experiments, electron spin resonance (ESR) signals revealed that the photogenerated holes (h+), hydroxyl radical (•OH), sulfate radical (•SO4-), and superoxide radical (•O2-) played an important role in CIP degradation; hydroxyl radicals (•OH) and sulfate radicals (•SO4-) play a major role. Various characterization methods have demonstrated that Fe-BOC-X has larger specific surface area and pore volume than original BiOCl. UV-vis DRS indicate that Fe-BOC-X has wider visible light absorption and faster photocarrier transfer and provides abundant surface oxygen absorption sites for effective molecular oxygen activation. Accordingly, a large number of active species were produced and participated in the photocatalytic process, thus effectively promoting the degradation of ciprofloxacin. Based on HPLC-MS analysis, two possible decomposition pathways of CIP were finally proposed. The main degradation pathways of CIP are mainly due to the high electron density of piperazine ring in CIP molecule, which is mainly attacked by various free radicals. The main reactions include piperazine ring opening, decarbonylation, decarboxylation, and fluorine substitution. This study can better open up a new way for the design of visible light driven photocatalyst and provide more ideas for the removal of CIP in water environment.

Adsorption behavior of triclosan on microplastics and their combined acute toxicity to D. magna

Microplastics (MP) have been recently identified as emerging water contaminants in worldwide. Owing to its physicochemical properties, MP have been considered as a vector of other micropollutants and may affect their fate and ecological toxicity in the water environment. In this study, triclosan (TCS), which is a widely-used bactericide, and three frequently found types of MP (PS-MP, PE-MP, and PP-MP) were investigated. The adsorption behavior of TCS on MP was investigated by the effect of reaction time, initial concentration of TCS, and other water chemistry factors. Elovich model and Temkin model are the most fitted well with kinetics and adsorption isotherms, respectively. The maximum TCS adsorption capacities were calculated for PS-MP (9.36 mg/g), PP-MP (8.23 mg/g), and PE-MP (6.47 mg/g). PS-MP had higher affinity to TCS owing to hydrophobic and π-π interaction. The TCS adsorption on PS-MP was inhibited by decreasing concentrations of cations, and increasing concentration of anion, pH, and NOM concentration. At pH 10, only 0.22 mg/g of adsorption capacity was obtained because of the isoelectric point (3.75) of PS-MP and pKa (7.9) of TCS. And almost no TCS adsorption occurred at NOM concentration of 11.8 mg/L. Only PS-MP had no acute toxic effect on D. magna, whereas TCS showed acute toxicity (EC_50,24h of TCS = 0.36 ± 0.4 mg/L). Although survival rate increased when TCS with PS-MP due to lower the TCS concentration in solution via adsorption, PS-MP was observed in intestine and body surface of D. magna. Our findings can contribute to understanding the combined potential effects of MP fragment and TCS to aquatic biota.

Abandoned disposable masks become hot substrates for plastisphere, whether in soil, atmosphere or water

A large number of surgical masks (SMs) to be discarded indiscriminately during the spread of COVID-19. The relationship between the changes of masks entering the environment and the succession of the microorganisms on them is not yet clear. The natural aging process of SMs in different environments (water, soil, and atmosphere) was simulated, the changes and succession of the microbial community on SMs with aging time were explored. The results showed that the SMs in water environment had the highest aging degree, followed by atmospheric environment, and SMs in soil had the lowest aging degree. The results of high-throughput sequencing demonstrated the load capacity of SMs for microorganisms, showed the important role of environment in determining microbial species on SMs. According to the relative abundance of microorganisms, it is found that compared with the water environment, the microbial community on SMs in water is dominated by rare species. While in soil, in addition to rare species, there are a lot of swinging strains on the SMs. Uncovering the ageing of SMs in the environment and its association with the colonization of microorganisms will help us understand the potential of microorganisms, especially pathogenic bacteria, to survive and migrate on SMs.

New insights into the migration, distribution and accumulation of micro-plastic in marine environment: A critical mechanism review

Microplastics (MPs) are widely distributed in the marine environment, posing a significant threat to marine biota. The contribution of anthropogenic and terrestrial sources to the aquatic ecosystem has led to an increase in MPs findings, and their abundance in aquatic biota has been reported to be of concern. MPs are formed mainly via photo degradation of macroplastics (large plastic debris), and their release into the environment is a result of the degradation of additives. Eco-toxicological risks are increasing for marine organisms, due to the ingestion of MPs, which cause damage to gastrointestinal (GI) tracts and stomach. Plastics with a size <5 mm are considered MPs, and they are commonly identified by Raman spectroscopy, Fourier transfer infrared (FTIR) spectroscopy, and Laser direct infrared (LDIR). The size, density and additives are the main factors influencing the abundance and bioavailability of MPs. The most abundant type of MPs found in fishes are fiber, polystyrenes, and fragments. These microscale pellets cause physiological stress and growth deformities by targeting the GI tracts of fishes and other biota. Approximately 80% MPs come from terrestrial sources, either primary, generated during different products such as skin care products, tires production and the use of MPs as carrier for pharmaceutical products, or secondary plastics, disposed of near coastal areas and water bodies. The issue of MPs and their potential effects on the marine ecosystem require proper attention. Therefore, this study conducted an extensive literature review on assessing MPs levels in fishes, sediments, seawater, their sources, and effects on marine biota (especially on fishes), chemo-physical behavior and the techniques used for their identification.

Multispectroscopic Characterization of Surface Interaction between Antibiotics and Micro(nano)-sized Plastics from Surgical Masks and Plastic Bottles

Recent studies have shown that plastic particles can sorb antibiotics, and these sorption properties have been examined in various studies; however, the possible mechanism responsible for the interactions requires a deeper investigation in terms of further interaction with living systems. Moreover, the usage of disposable surgical masks and plastic bottles has increased the plastic pollution risk for living systems like humans. Therefore, this study aimed to examine the sorption characteristics between antibiotics (amoxicillin and spiramycin) and plastic particles from surgical masks and plastic bottles through batch sorption experiments. In the study, their surface interactions were characterized using multispectroscopic approaches including FTIR, Raman spectrometry, and SEM-EDX, and various surface indicators (e.g., surface oxidation, deformation, and biological potential) were examined. The sorption results showed that adsorption kinetics and the isotherm of amoxicillin and spiramycin on micro(nano)plastics from surgical masks and plastic bottles closely fit the pseudo-second-order kinetic model and Langmiur isotherm. These results indicated that the evidence for the antibiotic interaction with particles was changes in the surface functional group intensities and up-shifting, and this correlated with the sorption of antibiotics on micro(nano)-sized plastics. The C/N ratio of the plastic particles before and after antibiotic treatment was used as an indicator for the surface biological interaction, and the results showed that C/N ratios of surgical mask particles increased with both types of antibiotic sorption. However, the C/N of the particles from plastic bottles showed antibiotic type-dependence. The surface deformation indicators (e.g., O/C, C=O, C=C, and O-H indices) showed that the O/C ratios of micro(nano)plastics from surgical masks were higher with the amoxicillin and spiramycin sorption, and the C=O indices were positively linked with the amoxicillin sorption stages, whereas the C=C and O-H had a negative correlation with the amoxicillin sorption stages. Moreover, amoxicillin sorption influenced the O/C ratio and indices of O-H and C=C of micro(nano)plastics from plastic bottles in a limited manner. The C=O groups of the micro(nano)plastics from plastic bottles were positively influenced by the spiramycin sorption stages, whereas it was negatively linked with amoxicillin sorption stages. Overall, the findings from surface indicators indicated that the micro(nano)plastics from surgical masks can be more influenced with antibiotic sorption compared to plastic bottles.

Exploration of Reactive Black 5 Dye Desorption from Composite Hydrogel Beads—Adsorbent Reusability, Kinetic and Equilibrium Isotherms

A low-cost adsorbent was prepared by using cherry stones powder and chitosan and used to retain Reactive Black 5 dye from aqueous solution. Then, the spent material was submitted to a regeneration process. Five different eluents (water, sodium hydroxide, hydrochloric acid, sodium chloride and ethanol) were tested. Among them, sodium hydroxide was selected for an advanced investigation. Values of three working conditions, namely the eluent volume, its concentration and the desorption temperature, were optimized by Response Surface Methodology-Box–Behnken Design. In the established settings (NaOH volume: 30 mL, NaOH concentration: 1.5 M, working temperature: 40 °C), three successive cycles of adsorption/desorption were conducted. The analysis performed by Scanning Electron Microscopy and by Fourier Transform Infrared Spectroscopy revealed the evolution of the adsorbent throughout the dye elution from the material. Pseudo-second-order kinetic model and Freundlich equilibrium isotherm were able to accurately describe the desorption process. Based on the acquired results, our outcomes sustain the suitability of the synthesized material as dye adsorbent and the possibility of efficaciously recycling and reusing it.

Biological responses of Chironomus sancticaroli to exposure to naturally aged PP microplastics under realistic concentrations

Microplastic (MP) is yet another form of chronic anthropogenic contribution to the environment. MPs are plastic particles (<5 mm) that have been widely found in the most diverse natural environments, but their real impacts on ecosystems are still under investigation. Here, we studied the toxicity of naturally aged secondary polypropylene (PP) MPs after constant exposure to ultraviolet radiation (26 µm) to the third instar larvae of Chironomus sancticaroli, a dipteran species. The concentrations tested were 13.5; 67.5; and 135 items g^-1 of dry sediment. C. sancticaroli organisms were investigated for fragment ingestion, mortality and changes in enzymatic biomarkers after 144 h of exposure. The organisms were able to ingest MPs from the first 48 h, and the amount of items internalized was dose-dependent and time-dependent. Overall, the results show that mortality was low, being significant at the lowest and highest concentrations (13.5 and 135 items g^-1). Regarding changes in biochemical markers, after 144 h MDA and CAT activities were both significantly altered (increased and reduced, respectively), while SOD and GST levels were unchanged. In the present study, naturally aged polypropylene MPs induced biochemical toxicity in C. sancticaroli larvae, with toxicity being higher according to exposure time and particle concentration.

A proposed reporting framework for microplastic-metal mixtures research, with emphasis on environmental considerations known to influence metals

In recent years, there has been an increase in research to understand the consequences of microplastic contamination. A subset of this research assesses the interaction of microplastics with metals and the subsequent effects of the resulting microplastic-metal complexes in freshwater environments. While our understanding of how microplastics behave in freshwater remains largely unknown, our knowledge of metal behavior in those same environments is well-established. The behavior (partitioning, speciation, bioavailability) of metals is highly dependent on environmental characteristics, including water quality variables such as hardness, pH, and dissolved organic matter. This study reveals that despite our understanding of metal behavior, there is little consideration for these influential factors in the current body of microplastic-metal research. Multiple instances highlighted throughout this study show that even when similar plastic, metal, and biota are utilized, there are conflicting observations as to whether the mixture is toxic; we stress that without adequate reporting of environmental conditions, these contradictions are likely to persist without explanation. Through justification of water quality characteristics known to influence metal behavior, this study proposes a framework of reporting requirements for all future microplastic-metal research.

Insights into the removal of microplastics and microfibres by Advanced Oxidation Processes

Water treatment plants' effluents are hotspots of microplastics (MPs) and microfibres (MFs) released into the aquatic environment because they were not designed to capture these particles. Special attention should be given to MFs, since they mainly come from laundry and are related to one of the main MP shapes detected in water and wastewater treatment plants. In this sense, Advanced Oxidation Processes (AOPs) could be a feasible solution for tackling MP and MF pollution, however, it is still premature to extract conclusions due to the limited number of studies on the degradation of these particles (specifically MFs) using AOPs. This review addresses the impacts of AOPs on MPs/MFs, focusing on their degradation efficiency, toxicity, and sustainability of the processes, among other aspects. The review points out that polyamide MFs can achieve mass loss >90% by photocatalytic system using TiO₂. Also, the low oxidation of MPs (<30 %) by conventional Fenton process affects mainly the surface of the MPs. However, other Fenton-based processes can provide better removal of some types of MPs, mainly using temperatures >100 °C, reaction time ≥ 5 h, and initial pH ≤ 3, achieving MP weight loss up to 96 %. Despite these results, better operating conditions are still required for AOPs since the ones reported so far are not feasible for full-scale application. Additionally, ozonation in treatment plants has increased the fragmentation of MPs (including MFs), leading to a new generation of MPs. More attention is needed on toxicity effects of intermediates and methods of analysis employed for the analysis of MPs/MFs in wastewater effluent should be standardized so that studies can be compared effectively. Future research should focus on the sustainability of the AOP for MP removal in water treatment (power consumption, chemicals consumed and operational costs) for a better understanding of full-scale applicability of AOP adapted to MP treatment.

A systematic review of microplastics in the environment: Sampling, separation, characterization and coexistence mechanisms with pollutants

Microplastics (<5 mm) (MPs) are widely distributed throughout the world, and their accumulation and migration in the environment have caused health and safety concerns. Currently, most of the reviewed literatures mainly focus on the distribution in various environmental media, adsorption mechanisms with different pollutants, and characterization of MPs. Therefore, the present review mainly highlights the characterization techniques of MPs and the underlying mechanisms of their combination with conventional coexisting substances (heavy metals, organic pollutants, and nutrients). We observed that massive MP pollution has been found in many areas, especially in Africa, Asia, India, South Africa, North America and Europe. The separation methods of MPs in different environmental media are basically similar, including sampling, pre-treatment, flotation, filtration and digestion. The combination of multiple characterization technologies can more precisely identify the shape, abundance, colour, and particle size of MPs. Notably, although recent reports have confirmed that MPs can act as carriers of heavy metals and carry them into organisms to cause harm, MPs have different adsorption and desorption characteristics for various heavy metals. The adsorption capacity of organic pollutants onto MPs is closely related to their hydrophobicity, specific surface area and functional group characteristics. The relative abundance of MPs in sediments and lakes had a significantly positive correlation with the mass concentration of total nitrogen in lake water, but this finding still needs to be further verified. Based on current research, we suggest that future MP research should focus on characterization technology, environmental migration, ecological effects, health risks and degradation methods.

Aging dependent plastic bag derived-microplastics as a vector of metals in lake water

The adsorption of microplastics (MPs) for metals in aquatic environment remains poorly understood due to the use of either commercial MPs, which have different property from the MPs in environments, or artificial solutions, which have not only the significantly higher concentration of metals than natural aqueous environment but also the different natures. In this study, we elaborated the adsorption throughout the aging process of plastic bag derived-MPs (initially 1-2 mm) by potassium persulfate (K₂S₂O₈) solution to metals in lake water. Comparatively, plastic bag derived-MPs had the highest adsorption capacity for Zn²⁺ followed by Fe³⁺, Pb²⁺, Mn²⁺, Cr⁶⁺, Ni²⁺, Cu²⁺ and Cd²⁺, which is not completely consistent with the literature. Both the adsorption capacity and distribution coefficients of Cu²⁺, Ni²⁺, Zn²⁺, Mn²⁺ and Pb²⁺ had significant linear correlation with carbonyl index (p < 0.05). Although the aging overall enhanced the adsorption, the adsorption capacities of MPs might fluctuate depending on metal.

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

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

New insights into adsorption mechanism of pristine and weathered polyamide microplastics towards hydrophilic organic compounds

The widespread coexistence of hydrophilic organic compounds and microplastics (MPs) in the environment has greatly increased their associated environmental problems. To evaluate the potential carrier effect of oxygen-containing MPs on coexisting pollutants, adsorption behaviors of four hydrophilic organic compounds (benzoic acid, sulfamethoxazole, sulfamerazine and ciprofloxacin) on MPs (pristine and weathered polyamide (PA)) were studied in the aquatic environment. The results showed that the surface morphology, size, oxygen content, molecular structure, surface charge and crystallinity of PA were changed after weathering, and the weathering degree of PA treated with heat-activated potassium persulfate was the highest. The main adsorption mechanisms included hydrogen bonding, hydrophobic interaction, charge-assisted hydrogen bonding, and electrostatic interaction. Hydrogen bonding and hydrophobic interaction contributed to the adsorption, while electrostatic interaction weakened the adsorption under the specific pH conditions. The formation of charge-assisted hydrogen bonding (CAHB) was also verified through pH influence experiments, and this force can overcome the electrostatic repulsion. The high adsorption of KPA (PA weathered by K₂S₂O₈) under alkaline conditions was well explained by the formation of homonuclear CAHB due to the increase of oxygen-containing functional groups compared to the other three PA. Additionally, weathering did not always enhance the adsorption of hydrophilic organic compounds on PA, which was related to the changes in surface charge, crystallinity and hydrophilicity of PA. Overall, the physical and chemical properties (e.g., specific surface area, oxygen content, molecular structure) of PA after weathering and its trend of adsorption were different from other oxygen-free MPs in this study. This work can provide basic data for environmental risk of MPs and contribute to clarify and understand the processes of oxygenated MPs in the aquatic environment.

Methine initiated polypropylene-based disposable face masks aging validated by micromechanical properties loss of atomic force microscopy

The contagious coronavirus disease-2019 pandemic has led to an increasing number of disposable face masks (DFMs) abandoned in the environment, when they are exposed to the air condition, the broken of chemical bond induced aging is inevitably occurred which meantime would cause a drastic decrease of the mechanical flexibility. However, the understanding of between chemical bond change related to aging and its micromechanical loss is limited due to the lack of refined techniques. Herein, the atomic force microscopy (AFM) technique was firstly used to observe the aging process induced by methine of the polypropylene-based DFMs. By comparing the micromechanical properties loss, the influences of humidity and light density on the DFM aging were systematically studied in the early 72 h, and it revealed that the increasing scissions number of the easiest attacked methine (C^t-H) can gradually decrease the micromechanical properties of the polypropylene (PP)-based DFM. Furthermore, the results are also validated by the in- situ FTIR and XPS analysis. This work discloses that an aging process can be initially estimated with the micromechanical changes observed by AFM, which offers fundamental data to manage this important emerging plastic pollution during COVID-19 pandemic.

Insight into the microplastics release from disposable face mask: Simulated environment and removal strategy

The fight against the COVID-19 epidemic significantly raises the global demand for personal protective equipment, especially disposable face masks (DFMs). The discarded DFMs may become a potential source of microplastics (MPs), which has attracted much attention. In this work, we identified the detailed source of MPs released from DFMs with laser direct infrared spectroscopy. Polypropylene (PP) and polyurethane (PU) accounted for 24.5% and 57.1% of released MPs, respectively. The melt-blown fabric was a dominant MPs source, however, previous studies underestimated the contribution of mask rope. The captured polyethylene terephthalate (PET), polyamide (PA), polyethylene (PE), and polystyrene (PS) in airborne only shared 18.4% of released MPs. To deepen the understanding of MPs release from medical mask into the aquatic environment, we investigated the effects of environmental factors on MPs release. Based on regression analysis, the effects of temperature, incubation time, and wearing time significantly affect the release of MPs. Besides, acidity, alkalinity, sodium chloride, and humic acid also contributed to the MPs release through corroding, swelling, or repulsion of fibers. Based on the exposure of medical mask to simulated environments, the number of released MPs followed the order: seawater > simulated gut-fluid > freshwater > pure water. Considering the risk of MPs released from DFMs to the environment, we innovatively established a novel flotation removal system combined with cocoamidopropyl betaine, achieving 86% removal efficiency of MPs in water. This work shed the light on the MPs release from DFMs and proposed a removal strategy for the control of MPs pollution.

Predicting the aggregation number of cationic surfactants based on ANN-QSAR modeling approaches: understanding the impact of molecular descriptors on aggregation numbers

In this work, a quantitative structure-activity relationship (QSAR) study is performed on some cationic surfactants to evaluate the relationship between the molecular structures of the compounds with their aggregation numbers (AGGNs) in aqueous solution at 25 °C. An artificial neural network (ANN) model is combined with the QSAR study to predict the aggregation number of the surfactants. In the ANN analysis, four out of more than 3000 molecular descriptors were used as input variables, and the complete set of 41 cationic surfactants was randomly divided into a training set of 29, a test set of 6, and a validation set of 6 molecules. After that, a multiple linear regression (MLR) analysis was utilized to build a linear model using the same descriptors and the results were compared statistically with those of the ANN analysis. The square of the correlation coefficient (R 2) and root mean square error (RMSE) of the ANN and MLR models (for the whole data set) were 0.9392, 7.84, and 0.5010, 22.52, respectively. The results of the comparison revealed the efficiency of ANN in detecting a correlation between the molecular structure of surfactants and their AGGN values with a high predictive power due to the non-linearity in the studied data. Based on the ANN algorithm, the relative importance of the selected descriptors was computed and arranged in the following descending order: H-047 > ESpm12x > JGI6> Mor20p. Then, the QSAR data was interpreted and the impact of each descriptor on the AGGNs of the molecules were thoroughly discussed. The results showed there is a correlation between each selected descriptor and the AGGN values of the surfactants.

The effect of adsorption on the fate of colloidal polystyrene microplastics in drinking water distribution system pipe scales

With microplastics (MPs) being continuously found in various environments, the pollution of water supply systems by MPs is receiving increasing attention. As the sediment in drinking water distribution systems (DWDSs), pipe scales act as the interface for complex reactions between bulk water and pipe surfaces. Consequently, the fate of MPs in pipe scales requires exploration, especially colloidal MPs. In this study, MPs were detected in different pipe scale layers, with concentrations of 0.32-3.10 items g^-1. Subsequently, the adsorption interaction mechanisms between pipe scales and colloidal polystyrene microplastics (PSMPs) were investigated through batch adsorption experiments. The findings indicated that pipe scales showed a potential adsorption capacity for PSMPs. The adsorption kinetics and isotherms results demonstrated that the PSMP adsorption process was physically dominant and complicated. van der Waals and electrostatic interactions, hydrogen bonding, and pore filling were the main adsorption mechanisms. These results verify that colloidal MPs can be adsorbed by pipe scales, demonstrating that pipe scales play an essential role in the fate of colloidal MPs in DWDSs and the quality and security of drinking water. The secondary release of MPs from pipe scales is also worthy of attention due to the environmental and health risks.

Single and combined effects of antibiotics and nanoplastics from surgical masks and plastic bottles on pathogens

Over the last decade, pollution of plastics and antibiotics has increased in its threat to the environment and human health. However, very limited information is available concerning impact of co-presence of plastics and antibiotics on environment and human health. Moreover, the potential ingestion and inhalation of nano(micro)plastics due to the disposable materials has dramatically increased. With the outbreak and spread of the COVID-19 in the world, disposable surgical masks and plastic bottles have been widely used by the public, and their rapid use and improper dispensing can cause to increase plastic pollution risk on human. However, impacts of co-presence of nano(micro)plastics and antibiotics on pathogens have yet been demonstrated. Therefore, this study aims to investigate the impact the individual and combined influences of nano-sized plastics (surgical mask and plastic bottles) and antibiotics (amoxicillin and spiramycin) towards the main susceptible bacterium (Staphylococcus epidermidis, Staphylococcus aureus, Bacillus subtilis, Escherichia coli, and Pseudomonas aeruginosa) by microbial activity, biofilm formation and their biochemical characteristics. The results showed that antimicrobial efficiencies of the tested antibiotics were reduced (approximately 10-98%) with the plastics. Moreover, the biochemical pathways of the microbial activity changed by the plastics entrance. Polymer structure and sorption play the role on the reduction in the inhibition of pathogens. In the meantime, the biofilm formation changed and characteristic of the extracellular polymeric substance with the co-presence of plastics and antibiotics mostly depended on the polymer structure, exposure time and sorption.

Critical review of microplastics removal from the environment

Globally, microplastics pollution has become a serious environmental threat due to their multitude sources, widespread occurrence, persistence, and adverse effects to ecosystem and the human health. Addressing this multifaceted threat requires innovative technologies that can efficiently remove microplastics from the environment. In this review, we first overviewed the source, occurrence, and potential adverse impacts of microplastics to human health. We then identified promising technologies for microplastics removal, including physical, chemical, and biological approaches. A detailed analysis of the advantages and limitations of different techniques was provided. We concluded this review with the current challenges and future research priorities, which will guide us through the path addressing microplastics contamination.