Plastic-Rock Complexes as Hotspots for Microplastic Generation

Adsorption and desorption of phenanthrene and 1-hydroxyphenanthrene by goethite-coated polyvinyl chloride

Microplastics loaded with phenanthrene and derivatives are widely detected in aquatic environments, and the coating of natural minerals or organic macromolecules may change the environmental behavior of microplastics. In this study, three kinds of composites with different coverage were prepared by coating goethite on the surface of polyvinyl chloride microplastics to investigate the adsorption and desorption behavior of phenanthrene (PHE) and 1-hydroxyphenanthrene (1-OHPHE), and the effect of mucin on desorption was investigated. The results showed that goethite promoted the adsorption of PHE and 1-OHPHE by increasing the specific surface area of the composites. With the increase of the cover degree, the adsorption of PHE decreased because of the decrease in hydrophobicity; while the adsorption of 1-OHPHE initially increased and then decreased with the contributions of hydrophobic interaction and hydrogen bond. The adsorption of 1-OHPHE could be influenced by the pH and ionic strength primarily through electrostatic interactions and Ca2+ bridging. The goethite significantly increased the desorption hysteresis for two chemicals due to the complicated pore structures and increased adsorption affinity. Mucin promoted the desorption of PHE through competitive adsorption, and inhibit the desorption of 1-OHPHE through hydrophobic interaction, hydrogen bonding and Ca2+ bridging. This study elucidated the effects of natural minerals on the adsorption and desorption behavior of organic pollutants on microplastics, briefly discussed the effects of organic macromolecules on the desorption behavior of pollutants with different properties, and emphasized the different environmental behaviors of pollutants.

Biodegradation characterization and mechanism of low-density polyethylene by the enriched mixed-culture from plastic-contaminated soil

Plastic pollution poses significant ecological and health risks. In this study, we enriched microbial consortia from plastic-contaminated soil capable of degrading low-density polyethylene (LDPE) film over a 28-day incubation period. Using two kinds of enriched cultures, the mean film weight loss rate (WLR) of 0.27 ± 0.04 % (p < 0.01) was 9 times higher than the control. Scanning electron microscopy (SEM) revealed a average hole occurrence area of 0.67 ± 0.11 μm2 in the topmost sample, while the control had no change. Fourier transform infrared (FTIR) revealed specific changes in hydrophilicity (increased by 5.70 ± 0.02 times) and crystallinity (decreased by 15.73 ± 3.26 %). Meanwhile, FTIR analyses including peak occurrence at 3741 cm-1, carbonyl index and Lambert-Beer law calculations revealed moisture infiltration and predominant aldehyde carbonyl formation (88.69 % in total carbonyl). The results of high-throughput sequencing indicated Brevibacillus, Bacillus and Sporosarcina were dominate genera in the mixed-cultures, and PICRUSt2 implied they could use LDPE as the sole carbon source. Our study aims to provided theoretical basis driving plastic degradation and to mitigate plastic pollution based on microbial resource development.

Amplification of benzo[a]pyrene toxicity persistence in earthworms by polystyrene nanoplastics: From organismal health to molecular responses

Typically, nanoplastics (NPs) are contaminated before entering soil, and the impact of NPs on the biotoxicity of Persistent Organic Pollutants (POPs) they carry remains unclear. This study simulated two environmentally relevant scenarios: singular exposure of benzo[a]pyrene (BaP) in soil and exposure via NPs loading (NP-BaP). Correlation analysis and machine learning revealed that injury in earthworms exposed for 28 days was significantly associated with NPs. Moreover, when the soil exposure concentration of BaP was 4 mg/kg, the NP-BaP group exhibited 10.67 % greater pigmentation than the BaP-only group. Despite the lower biota soil accumulation factor (BSAF) of earthworms in the NP-BaP group, the concentration of BaP in the soil remained at higher levels in the late stages of exposure. This led to NP-BaP inducing a stronger trend of oxidative damage compared to BaP alone. Furthermore, molecular-level studies indicated that the differential preferences of NPs and BaP for damaging antioxidant enzymes were linked to individual oxidative stress responses. This study confirmed that NPs, at non-toxic concentrations, could increase the persistence of BaP's biological toxicity after prolonged exposure, highlighting the potential safety risks of NPs as carriers of POPs to soil organisms.

Unveiling plastifoamcrete: Composition, characteristics, and environmental threats of urban plastic variants

As plastic pollution research advances, novel plastic forms continue to emerge, posing new challenges for pollution control and environmental management. While coastal plastic pollution has been widely studied, urban environments remain understudied. This study introduces plastifoamcrete, a newly identified variant of plasticoncrete found in urban waste in Mexico City. Plastifoamcrete refers to fragmented pieces of concrete containing embedded microplastic Styrofoam beads, formed from the breakdown of foamed concrete during demolition and improper disposal. We analyzed 12 samples, each exhibiting various shapes and sizes (ranging from 3.56 x 3.66 to 16.18 × 10.50 cm) and signs of pitting, possibly due to bead release during construction demolition or bead shaping during foamed concrete production. Bead distribution was uneven, with abundances ranging from 395 to 1938 cm2, and sizes between 0.46 and 5.8 mm. FTIR analysis confirmed their polystyrene composition. Given its friable nature, plastifoamcrete poses a risk of microplastic release and facilitates the transport of synthetic debris across terrestrial and aquatic environments. Its degradation not only can contribute to microplastic pollution but may also alter environmental pH, promote biofilm colonization, and serve as a vector for pollutant accumulation and dispersal, amplifying its ecological impact. By identifying plastifoamcrete within urban waste streams, this study broadens the scope of plastic pollution research and underscores the importance of integrating construction waste management into environmental policies.

Modeling microplastic transport through porous media: Challenges arising from dynamic transport behavior

Modelling microplastic transport through porous media, such as soils and aquifers, is an emerging research topic, where existing hydrogeological models for (reactive) solute and colloid transport have shown limited effectiveness thus far. This perspective article draws upon recent literature to provide a brief overview of key microplastic transport processes, with emphases on less well-understood processes, to propose potential research directions for efficiently modeling microplastic transport through the porous environment. Microplastics are particulate matter with distinct physicochemical properties. Biogeochemical processes and physical interactions with the surrounding environment cause microplastic properties such as material density, geometry, chemical composition, and DLVO interaction parameters to change dynamically, through complex webs of interactions and feedbacks that dynamically affect transport behavior. Furthermore, microplastic material densities, which cluster around that of water, distinguish microplastics from other colloids, with impactful consequences that are often underappreciated. For example, (near-)neutral material densities cause microplastic transport behavior to be highly sensitive to spatio-temporally varying environmental conditions. The dynamic nature of microplastic properties implies that at environmentally relevant large spatio-temporal scales, the complex transport behavior may be effectively intractable to direct physical modeling. Therefore, efficient modeling may require integrating reduced-complexity physics-constrained models, with stochastic or statistical analyses, supported by extensive environmental data.

Integrated Ziegler-Natta/Brookhart-Ni Catalysts for the Synthesis of Sutured Polar High-Impact Polypropylenes

The direct synthesis of polar high-impact polypropylenes using industrially-preferred heterogeneous catalysts is challenging due to the poisoning of polar functional groups towards metal center and the high stereo-selectivity requirement. In this work, dual-site catalysts combining Ziegler-Natta and Brookhart-Ni catalysts were used to produce polar polyolefin ionomers, followed by polar high-impact polypropylenes containing isotactic polypropylene and branched polyethylene as toughening agents. Three combination modes between these catalysts were investigated, including mixed, core-shell, and integrated types. The integrated dual-site catalyst achieved the optimal material properties because the polyolefin ionomer acted as a suture molecule that stitched different components into a whole network. This produced sutured polar high-impact polypropylenes with excellent mechanical properties and compatibility with polar substances. The restraining effect of the suture molecules greatly reduced the release of microplastic particles after aging. Moreover, the obtained polar high-impact polypropylene can serve as an efficient compatibilizer to recycle polyethylene/polypropylene mixed-waste plastics. This work provides an appealing and potentially practical strategy to upgrade the widely used polypropylenes and to alleviate the ever-growing plastic pollution issue.

Long-term soil remediation using layered double hydroxides: Field evidence for simultaneous immobilization of both cations and oxyanions

Layered double hydroxides (LDHs) have great potential for immobilizing potentially toxic elements in soil. Nevertheless, their practical effectiveness under field conditions remains largely unknown. In this study, we conducted a 2.5-year field trial using pristine Mg-Al LDHs, Ca-Al LDHs, and iron (Fe)-modified LDHs to simultaneously immobilize both oxyanions (including As and Sb) and cations (including Cd and Pb) in historically contaminated soil affected by mining activities since the 1950s. The immobilization performance of LDHs was examined using various batch tests, including water and DTPA extraction, and by measuring metal(loid) concentrations in Coriandrum sativum (coriander). We found that both pristine and Fe-modified LDHs showed promising initial immobilization performance 7 days after application, achieving significant reductions in DTPA-extractable concentrations of As, Sb, Cd, and Pb by 45.6%-68.3%, 55.4%-94.2%, 11.2%-50.9%, and 62.9%-64.9%, respectively, compared to the control soil without amendment. Notably, pristine LDHs showed diminished immobilization performance in the long term, while Fe-modified LDHs exhibited long-term stability over 2.5 years. A conditional probability-based model was used to depict long-term metal(loid) leaching characteristics in LDH-amended soils. Temporal changes in metal(loid) concentrations in the aboveground edible parts (namely, stems and leaves) of coriander corroborated well with DTPA extraction results. Coriander grown in Fe-modified LDH-amended soils had much lower metal(loid) concentrations compared to those grown in pristine LDH-amended soils. As a result, reductions of 35.1%-42.2% for As, 54.4%-66.2% for Sb, 8.5%-22.8% for Cd, and 56.0%-62.7% for Pb concentrations in coriander were still observed 2.5 years after soil amendment with Fe-modified LDHs. To the best of our knowledge, this is the first field-based evidence using LDHs to simultaneously stabilize both cations and oxyanions in soil. The findings support the potential of LDHs for long-term immobilization of metal(loid)s in soil.

When plastisphere and drilosphere meet: Earthworms facilitate microbiome and nutrient turnover to accelerate biodegradation of agricultural plastic films

Agricultural plastic mulching films have been an environmental concern for decades. The effects of the interactions between the anthropogenic plastisphere and other soil biospheres, particularly that of earthworms, on the fate of plastics remain poorly understood. Here, we investigated the decomposition of buried nonbiodegradable low-density polyethylene (LDPE) versus biodegradable PBTA/PLA copolymers in the presence of earthworms (Amynthas cortices) in dynamic microcosms. Earthworms significantly enhanced the biodegradation of plastic films in situ, as confirmed by mass reduction, surface modification, and changes in the molecular weights of films. Notably, the PBTA/PLA films exhibited a 1.41-fold increase in mass loss and a 5.69% reduction in the number-average molecular weight when incubated with earthworms. Earthworms influenced the microbial assembly within the plastisphere by increasing both bacterial and fungal biodiversity, as well as their network complexity. The time-decay patterns in the abundance of keystone degrader taxa, including the genera Noviherbaspirillum, Rhizobacter, and Mortierella, were mitigated by earthworms over the 60-day period. Additionally, earthworms preferentially consumed recalcitrant dissolved organic matter in LDPE and PBAT/PLA plastisphere soils, thereby increasing the bioavailability of components that serve as nutrient supplies for plastisphere microbiomes. Our findings demonstrate that earthworms enhance the decomposition of plastics in soils via cross-species interplay within the plastisphere and drilosphere, contributing not only to soil conditioning and biodiversity but also to plastic biodegradation in natural agroecosystems.

Unveiling the crucial role of iron oxide transformation in simultaneous immobilization of nanoplastics and organic matter

Nanoplastics (NPs) have been found in natural environments. However, the sequestration of NPs and natural organic matter (NOM) coupled with the Fe(III) hydrolysis and subsequent iron oxides transformation remains unclear. Here, we investigated the behaviors of NPs during the dynamic transformation process of iron oxides in the presence of humic acids (HA). The quantification results of europium chelate-labeled polystyrene (PS) NPs and HA indicate that 87.60 % of NPs and 49.45 % of HA were sequestered in the precipitate by the end of the transformation (240 h). High-angle annular dark-field-scanning transmission electron microscopy-energy dispersive X-ray spectroscopy (HAADF-STEM-EDS) images show that NPs were doped into iron oxides during the recrystallization of ferrihydrite aggregates, while HA were adsorbed or penetrated into the nanoscale pores on the mineral surfaces, suggesting the formation of a stable iron oxides-NPs-NOM ternary nanocomplex with a core-shell structure. Fourier transform infrared spectrometer (FTIR) and two-dimensional correlation spectroscopy (2D-COS) analysis indicate that functional groups of iron oxides and HA, including hydroxyl, carboxyl, and FeO bonds, played a role in the binding process. In the presence of HA, the stability of the coprecipitation system was enhanced due to the increased electrostatic repulsion, which facilitated the full incorporation of NPs with iron oxides. These findings provide a new insight into the simultaneous immobilization of NPs and NOM.

Enhanced immobilization of trace nickel by nanoplastic-Fe-Mn oxide complexes in sedimentary systems

Fe/Mn oxides are widely distributed mineral components in marine sediments and act as significant scavengers of trace metals. The emergence of plastic-rock complexes has led to an increasing recognition that plastics may influence the environmental behavior of minerals. Plastics, especially nanoplastics, can affect the formation of Fe/Mn oxides and their ability to immobilize heavy metals. In this study, the role of polystyrene nanoplastics (PS NPs) in the mineralization of FeMn oxides and their effects on the immobilization of heavy metals (using Ni(II) as an example) at the trace concentrations in the environment were investigated. Characterization analysis indicated that PS NPs not only adsorb Fe and Mn ions from the environment through electrostatic attraction (the force that draws together objects with opposite electrical charges) but also serve as a substrate for the heterogeneous nucleation and growth of FeMn oxides. The large specific surface area of the PS NPs provides a site for the growth of FeMn. This results in smaller particle sizes and larger specific surface areas for the generated FeMn oxides. Consequently, Fe-PS-Mn@SiO2 exhibits significantly greater adsorption efficiency for Ni(II) under various environmental conditions (such as different pH and salinity) compared to Fe-Mn@SiO2. Additionally, Fe-PS-Mn@SiO2 remained stable under sunlight at 60 °C over 1.5 years. These findings presented new insights into the impact of NPs on mineral formation and environmental behavior, expanding our understanding of the actual fate of NPs in sediment environments.

A review of methods for mitigating microplastic contamination in biosolids from wastewater treatment plants before agricultural soil application

Wastewater treatment plants (WWTP) are recognized as major sources of microplastic (MP) particles in terrestrial environments, particularly in agricultural soils through biosolids application. While many reviews have focused on the distribution, detection, and mitigation of MPs in wastewater effluent to limit their discharge into oceans, our understanding of methods to mitigate biosolid contamination remains limited. This review focuses on methods for mitigating MPs contamination in biosolids at various intervention points, including sources, WWTP including the primary and secondary treatment stages where sludge is generated, and post-contamination. These methods are categorized as physical, physicochemical, and biological approaches, and their advantages and limitations are discussed. For instance, physicochemical methods, especially froth flotation, are cost-effective but are hindered by contaminants and reagents. Physical methods like microfibre filtration devices (MFD) are safe but their efficiency depends on the filter pore size and design. Biological methods, particularly microbial degradation, are limited by the varying efficiencies of microorganisms in breaking down MPs and the extended time required for their effective degradation. Other physical methods including dissolved air flotation, and ultrasonication already exist in WWTPs but may require retrofitting or optimization to enhance MP removal from biosolids. As each method inherently has limitations, the key to achieving MP-free biosolids, and thus preventing their release into agricultural soil, lies in integrating these methods through multi-coupling strategies.

Increased methane production associated with community shifts towards Methanocella in paddy soils with the presence of nanoplastics

BACKGROUND

Planetary plastic pollution poses a major threat to ecosystems and human health in the Anthropocene, yet its impact on biogeochemical cycling remains poorly understood. Waterlogged rice paddies are globally important sources of CH4. Given the widespread use of plastic mulching in soils, it is urgent to unravel whether low-density polyethylene (LDPE) will affect the methanogenic community in flooded paddy soils. Here, we employed a combination of process measurements, short-chain and long-chain fatty acid (SCFAs and LCFAs) profiling, Fourier-transform ion cyclotron resonance mass spectrometry, quantitative PCR, metagenomics, and mRNA profiling to investigate the impact of LDPE nanoplastics (NPs) on dissolved organic carbon (DOC) and CH4 production in both black and red paddy soils under anoxic incubation over a 160-day period.

RESULTS

Despite significant differences in microbiome composition between the two soil types, both exhibited similar results to NPs exposure. NPs induced a change in DOC content and CH4 production up to 1.8-fold and 10.1-fold, respectively. The proportion of labile dissolved organic matter decreased, while its recalcitrance increased. Genes associated with the degradation of complex carbohydrates and aromatic carbon were significantly enriched. The elevated CH4 production was significantly correlated to increases in both the PCR-quantified mcrA gene copy numbers and the metagenomic methanogen-to-bacteria abundance ratio. Notably, the latter was linked to an enrichment of the hydrogenotrophic methanogenesis pathway. Among 391 metagenome-assembled genomes (MAGs), the abundance of several Syntrophomonas and Methanocella MAGs increased concomitantly, suggesting that the NPs treatments stimulated the syntrophic oxidation of fatty acids. mRNA profiling further identified Methanosarcinaceae and Methanocellaceae to be the key players in the NPs-induced CH4 production.

CONCLUSIONS

The specific enrichment of Syntrophomonas and Methanocella indicates that LDPE NPs stimulate the syntrophic oxidation of LCFAs and SCFAs, with Methanocella acting as the hydrogenotrophic methanogen partner. Our findings enhance the understanding of how LDPE NPs affect the methanogenic community in waterlogged paddy soils. Given the importance of this ecosystem, our results are crucial for elucidating the mechanisms that govern carbon fluxes, which are highly relevant to global climate change.

Modeling the temporal evolution of plastic film microplastics in soil using a backpropagation neural network

Plastic films are a crucial aspect of agricultural production in China, as well as a key source of microplastics in farmland. However, research into the environmental behavior of microplastics derived from polyethylene (PE) and biodegradable plastic films such as polybutylene adipate-co-terephthalate (PBAT) is limited by inadequate knowledge of their evolution and fate in soil. Therefore, we conducted controlled soil incubation experiments using new and aged microplastics derived from prepared PE and PBAT plastic films to determine their temporal evolution characteristics in soil. The results indicated that PBAT microplastics exhibited more pronounced changes in abundance, size, and shape over time than PE microplastics. Notably, the magnitude and timing of changes in newly introduced PBAT microplastics were consistently delayed relative to those of aged microplastics. Specifically, the abundance of aged PBAT microplastics initially increased then decreased, whereas their size continuously decreased, ultimately reaching 21.9 % and 47.5 % of the initial values, respectively. Furthermore, we constructed a novel backpropagation neural network model based on our morphological and spectral data, which effectively identified the incubation duration of PE and PBAT microplastics, with recognition accuracies of 98.1 % and 84.6 %, respectively. These findings offer a novel perspective for assessing the environmental persistence and fate of plastic film microplastics.

The dual role of coastal mangroves: Sinks and sources of microplastics in rapidly urbanizing areas

Mangrove ecosystems are vital for coastal protection, biodiversity, and pollution interception, yet their interactions with microplastics in rapidly urbanizing regions remain underexplored. This study investigated the microplastic dynamics in the Maozhou River and Dasha River, along with the coastal Xiwan Mangrove Park in the Pearl River Estuary, the second largest estuary in China. Samples were collected from mangrove and surrounding areas, identifying microplastics using Fourier-transform infrared spectroscopy (FTIR) and Laser Direct Infrared (LDIR) techniques. Microplastic concentrations ranged from 245.8 to 1562.4 n/m³ in water and 374.3 to 7475.3 n/kg in sediments. The Maozhou River exhibited consistent microplastic levels across varying hydrological conditions, while the Dasha River and Xiwan Mangrove showed greater sensitivity to water flow changes influenced by urban land use. During high-flow periods, urban river microplastic concentrations decreased due to dilution, whereas mangrove areas experienced elevated levels in water from urban runoff, upstream retention, and sediment resuspension, suggesting a potential for outward release. Weaker water dynamics led to increased microplastic accumulation in mangrove sediments. The distribution of microplastic types was influenced by multiple urban pollution sources, with synthetic rubbers linked to urban transportation comprising over 50 % of some samples, peaking at 79 %. These findings underscore the dual role of mangroves as microplastic sinks and potential sources, highlighting the significant impact of hydrological conditions on their function. This study offers new insights into microplastic pollution in urban mangrove ecosystems and emphasizes the urgent need for improved management strategies in coastal areas facing rapid urbanization.

Polyethylene microplastic pollution changes the electrical resistance and thermal conductivity of loess soil

While plastics provide convenience, they also endanger the safety of the natural environment. Microplastic pollution caused by plastic aging has become an urgent concern in public places. In order to study the effects of microplastics on soil physical properties, the electrical resistance and thermal conductivity of soils containing different polyethylene and moisture content were tested. The results show that polyethylene have two effects on soil electrical resistance: one is that the plastic particles increase electrical resistance, and the other is that the electrostatic field carried by the plastic particles reduces electrical resistance. The effect of the two factors is balanced by the content of polyethylene at 6-8%. When the polyethylene content of the soil was 6% and 10%, the coefficients of electrical resistance variation were 0.89, 0.67, 0.85, 0.96, 0.97, 0.99 and 0.95, 0.68, 0.71, 0.93, 0.95, 0.96, respectively. Polyethylene alters soil properties by affecting water distribution through hydrophobicity. The water content gradually increases to 10%, the liquid conduction area inside the soil increases, and the higher the soil's ability to conduct electricity and heat. The results can provide theoretical reference for evaluating and controlling soil microplastic pollution.

The synchronized dynamic release behavior of microplastics during farmland soil erosion process

Microplastics (MPs) are widespread in farmland soil. However, the risks associated with their loss through soil erosion remain unknown. This study investigates the occurrence and behavior of MPs in farmland soil in a southeastern coastal area of China, focusing on their synchronized dynamic release during soil erosion scenarios. The results showed that the abundance of MPs in the tested farmland soil ranged from 2.40 × 104 to 1.04 × 105 items·kg-1. MPs predominantly appear as fragments and particles, with sizes concentrated between 30 and 100 μm. During the process of soil erosion, characterized by rapid soil subsidence, the amount of MPs released into water bodies initially decreases, averaging a reduction of 1.08 × 104 items·kg-1. This is followed by an average increase of 1.89 × 104 items·kg-1. The competition between the adsorption, collision, and sedimentation of soil particles and the desorption and release of settled particles, determines this behavior. This pattern is strongly related to the physicochemical properties and mechanical composition of the soil. Deep learning predictions revealed that, without external influences, 49.42% of MPs in farmland soil could be synchronously released into water bodies during erosion. The analysis shows that MPs exhibit dynamic behavior in time and space, posing serious threats to aquatic ecosystems. Controlling soil erosion in farmland is crucial for the source management of MP migration.

Unveiling the impacts of microplastics on cadmium transfer in the soil-plant-human system: A review

The co-contamination of soils by microplastics (MPs) and cadmium (Cd), one of the most perilous heavy metals, is emerging as a significant global concern, posing risks to plant productivity and human health. However, there remains a gap in the literature concerning comprehensive evaluations of the combined effects of MPs and Cd on soil-plant-human systems. This review examines the interactions and co-impacts of MPs and Cd in soil-plant-human systems, elucidating their mechanisms and synergistic effects on plant development and health risks. We also review the origins and contamination levels of MPs and Cd, revealing that sewage, atmospheric deposition, and biosolid applications are contributors to the contamination of soil with MPs and Cd. Our meta-analysis demonstrates that MPs significantly (p<0.05) increase the bioavailability of soil Cd and the accumulation of Cd in plant shoots by 6.9 and 9.3 %, respectively. The MPs facilitate Cd desorption from soils through direct adsorption via surface complexation and physical adsorption, as well as indirectly by modifying soil physicochemical properties, such as pH and dissolved organic carbon, and altering soil microbial diversity. These interactions augment the bioavailability of Cd, along with MPs, adversely affect plant growth and its physiological functions. Moreover, the ingestion of MPs and Cd through the food chain significantly enhances the bioaccessibility of Cd and exacerbates histopathological alterations in human tissues, thereby amplifying the associated health risks. This review provides insights into the coexistence of MPs and Cd and their synergistic effects on soil-plant-human systems, emphasizing the need for further research in this critical subject area.

Characteristics and release potential of microplastics in municipal solid waste incineration bottom ash

Incineration is an effective method for reducing and safely treating municipal solid waste. However, microplastics (MPs) inevitably remain in the bottom ash, potentially introducing new pollution risks during subsequent treatment processes. This study conducted an analysis of the accumulation and release potential of MPs in bottom ash samples collected from 4 municipal solid waste incineration plants in Zhejiang, China. The results showed that the abundance of MPs ranged from 20 to 118 items g-1. Remarkably, MPs were found to accumulate predominantly in smaller bottom ash particles below 4.75 mm accounted for up to 70% of the total MPs. Most MPs in the bottom ash were under 100 μm in size, with a majority exceeding 50% being less than 50 μm, typically manifesting as shafts and fibers. In scenarios of secondary crushing, the abundance of MPs increased gradually with the degree of bottom ash crushing. When bottom ash was crushed to a particle size of less than 0.6 mm, the abundance of MPs reached up to 87-901 items g-1, which is 5-10 times higher than the original bottom ash. It is estimated that the annual release of MPs may reach up to 4.05 × 1016 particles. Re-incinerating thoroughly crushed bottom ash at 600 °C successfully decomposed the MPs. Mechanical stress can significantly increase the risk of MPs releasing in bottom ash. This risk can be eliminated by using secondary incineration to achieve complete MPs decomposition.

Element cycling with micro(nano)plastics

Plastics in the environment can alter a wide range of biogeochemical cycles.

Nanoscale Abrasive Wear of Polyethylene: A Novel Approach To Probe Nanoplastic Release at the Single Asperity Level

There is a growing concern that nanoplastic pollution may pose planetary threats to human and ecosystem health. However, a quantitative and mechanistic understanding of nanoplastic release via nanoscale mechanical degradation of bulk plastics and its interplay with photoweathering remains elusive. We developed a lateral force microscope (LFM)-based nanoscratch method to investigate mechanisms of nanoscale abrasive wear of low-density polyethylene (LDPE) surfaces by a single sand particle (simulated by a 300 nm tip) under environmentally relevant load, sliding motion, and sand size. For virgin LDPE, we found plowing as the dominant wear mechanism (i.e., deformed material pushed around the perimeter of scratch). After UVA-weathering, the wear mechanism of LDPE distinctively shifted to cutting wear (i.e., deformed material detached and pushed to the end of scratch). The shift in the mechanism was quantitatively described by a new parameter, which can be incorporated into calculating the NP release rate. We determined a 10-fold higher wear rate due to UV weathering. We also observed an unexpected resistance to initiate wear for UV-aged LDPE, likely due to nanohardness increase induced by UV. For the first time, we report 0.4-4 × 10-3 μm3/μm sliding distance/μN applied load as an initial approximate nanoplastic release rate for LDPE. Our novel findings reveal nanoplastic release mechanisms in the environment, enabling physics-based prediction of the global environmental inventory of nanoplastics.

First record of plastiglomerates, pyroplastics and plasticrusts along the beaches of Tamilnadu, Southeast coast of India

Plastic litter affects coastal and marine ecosystems globally. This study represents the first record of pyroplastics and plasticrust in the beaches of Tamil Nadu, India. All samples were FTIR spectroscopically examined to confirm the polymer composition of the suspected plastics. The 16 plastic formations were found in TamilNadu, including six plastiglomerates nine pyroplastics and one plasticrust. Five types of polymers (PET, PP, PVC, PA, and PE) were found on the plastic matrices. The study also revealed that pyroplastics and plasticrust formed by degradation of plastics through weathering in the coastal environment. The present study also found that four types of marine fouling organisms such as oyster larvae, bryozoan, barnacle and polychaete worm were encrusted on the two pyroplastics. The emergence of these new forms of plastic raises concerns about their interactions with the environment and biota.

Travertine deposition rather than tourism activity is the primary contributor to the microplastic risks in alpine karst lakes

Microplastics (MPs) are emerging as anthropogenic vectors to form plastisphere, facilitating microbiome colonization and pathogenic dissemination, thus contributing to environmental and health crises across various ecosystems. However, a knowledge gap persists regarding MPs risks and their driving factors in certain unique and vulnerable ecosystems, such as Karst travertine lakes, some of which are renowned World Natural Heritage Sites under ever-increasing tourism pressure. We hypothesized that tourism activities serve as the most important factor of MPs pollution, whereas intrinsic features, including travertine deposition can exacerbate potential environmental risks. Thus, metagenomic approaches were employed to investigate the geographical distribution of the microbiome, antibiotic resistance genes (ARGs), virulence factor genes (VFGs), and their combined environmental risks in Jiuzhaigou and Huanglong, two famous tourism destinations in Southwest China. The plastisphere risks were higher in Huanglong, contradicting our hypothesis that Jiuzhaigou would face more crucial antibiotic risks due to its higher tourist activities. Specifically, the levels of Lipopolysaccharide Lewis and fosD increased by sevenfold and 20-fold, respectively, from upstream to downstream in Huanglong, whereas in Jiuzhaigou, no significant accrual was observed. Structural equation modeling results showed that travertine deposition was the primary contributor to MPs risks in alpine karstic lakes. Our findings suggest that tourism has low impact on MPs risks, possibly because of proper management, and that travertine deposition might act as an MPs hotspot, emphasizing the importance of considering the unique aspects of travertine lakes in mitigating MPs pollution and promoting the sustainable development of World Natural Heritage Sites.

Highly flame retardancy, barrier, mechanical and persistent antibacterial polylactic acid film with high-parallel interconnected thousand layered cake architecture

In this work, a bio-based material (CGP) is obtained by combing chitosan, gelatin and polyvinyl alcohol through a simple solution mixing to simultaneously address polylactic acid film (PLA)' flammability and poor barrier, toughness and antibacterial properties by soaking. The results of open fire testing show that modified PLA films can effectively prolong the combustion time, improve the thermal stability and reduce the release of heat in the cone calorimeter test. For the PLA sample after soaking for 5 times (PLA-5) in particular, it can reduce the peak heat release rate (pHRR) and total heat release (THR) values to 85.8 kW/m2 and 1.3 MJ/m2 from the values of 129.5 kW/m2 and 1.8 MJ/m2 for PLA, respectively. Structural analysis suggests that CGP primarily operates in the condensed phase by forming physical barriers. Meanwhile, the modified PLA films can exhibit superior barrier effects, which indicate the oxygen transmission rate value of PLA-5 decreases to 0.9 cm3/(m2·day) from the 392.5 cm3/(m2·day) of raw PLA film. Moreover, the PLA-5 also have excellent toughness (the value increased to 200.5 % from 31.0 %) and persistent antibacterial effects (it still has 100 % sterilization after 500 days).

Emerging contaminants: A One Health perspective

Environmental pollution is escalating due to rapid global development that often prioritizes human needs over planetary health. Despite global efforts to mitigate legacy pollutants, the continuous introduction of new substances remains a major threat to both people and the planet. In response, global initiatives are focusing on risk assessment and regulation of emerging contaminants, as demonstrated by the ongoing efforts to establish the UN's Intergovernmental Science-Policy Panel on Chemicals, Waste, and Pollution Prevention. This review identifies the sources and impacts of emerging contaminants on planetary health, emphasizing the importance of adopting a One Health approach. Strategies for monitoring and addressing these pollutants are discussed, underscoring the need for robust and socially equitable environmental policies at both regional and international levels. Urgent actions are needed to transition toward sustainable pollution management practices to safeguard our planet for future generations.

Anthropogenic and biological activities elevate microplastics pollution in headwater ecosystem of Yangtze tributaries in Hindu Kush-Himalayan region

Microplastic (MP) pollution is widely spread in oceans, freshwater, and terrestrial environments but MPs in mountainous headwater ecosystem are rarely reported. This study focuses on the headwater of Yangtze tributaries of the Hindu Kush-Himalayan (HKH) region. Five streams at elevations of 900 to 3300 m were selected to investigate the distribution of MPs in water and sediments across altitudes. MPs were found in all water and sediment samples from top stream zone nearly in absence of anthropogenic activity, low anthropogenic zone, and high anthropogenic zone, increased from 12-54, 81-185 to 334-847 items/L, and 2-35, 26-84 to 124-428 items/kg, respectively. This elevation-dependent MP distribution indicated that as elevation decreased, anthropogenic activities intensified and increased MPs input and their abundance, size, and diversity. Notably, hydraulic projects, such as damming, were identified as potential barriers to the migration of MPs downstream. Microbiome analyses revealed the presence of bacterial genes associated with plastic biodegradation in all sediment samples. The study indicates that Shangri-la mountainous streams have been polluted with MPs for years with potential risk of generation of nano-sized particles via natural fragmentation and biodegradation, and thus raises concern on MPs pollution in headwaters streams in mountainous regions.

Uranium accumulation in environmentally relevant microplastics and agricultural soil at acidic and circumneutral pH

The co-occurrence of microplastics (MPs) with potentially toxic metals in the environment stresses the need to address their physicochemical interactions and the potential ecological and human health implications. Here, we investigated the reaction of aqueous U with agricultural soil and high-density polyethylene (HDPE) through the integration of batch experiments, microscopy, and spectroscopy. The aqueous initial concentration of U (100 μM) decreased between 98.6 and 99.2 % at pH 5 and between 86.2 and 98.9 % at pH 7.5 following the first half hour of reaction with 10 g of soil. In similar experimental conditions but with added HDPE, aqueous U decreased between 98.6 and 99.7 % at pH 5 and between 76.1 and 95.2 % at pH 7.5, suggesting that HDPE modified the accumulation of U in soil as a function of pH. Uranium-bearing precipitates on the cracked surface of HDPE were identified by SEM/EDS after two weeks of agitation in water at both pH 5 and 7.5. Accumulation of U on the near-surface region of reacted HDPE was confirmed by XPS. Our findings suggest that the precipitation of U was facilitated by the weathering of the surface of HDPE. These results provide insights about surface-mediated reactions of aqueous metals with MPs, contributing relevant information about the mobility of metals and MPs at co-contaminated agricultural sites.

Microplastic generation from field-collected plastic gauze: Unveiling the aging processes

Accumulation of plastic debris in the environment is a matter of global concern. As plastic ages, it generates microplastic (MP) particles with high mobility. Understanding how MPs are generated is crucial to controlling this emerging contaminant. In this study, we utilized high-density polyethylene (HDPE) plastic gauze, collected from urban settings, as a representative example of plastic waste. The plastic gauze was subjected to various aging conditions, including freeze-thaw cycling, mechanical abrasion, and UV irradiation. Following aging, the plastic gauze was rinsed with water, and the number of generated MPs were quantified. It was found that aged plastic gauze generated up to 334 million MP particles per m2 (> 10 µm) during rinsing, a number two orders of magnitude higher than unaged plastic. Fragmentation occurred in two dimensions for bulk MPs of all morphotypes. However, specific aging approaches (i.e., mechanical abrasion and UV irradiation) generated spheres and fibers via pseudo-3D fragmentation. Additionally, changes in molecular weight, size distribution, and surface oxidation characteristics unveiled a complex pattern (i.e., irregular changes with exposure time). This complexity underscores the intricate nature of plastic debris aging processes in the environment.

The distribution, fate, and environmental impacts of food additive nanomaterials in soil and aquatic ecosystems

Nanomaterials in the food industry are used as food additives, and the main function of these food additives is to improve food qualities including texture, flavor, color, consistency, preservation, and nutrient bioavailability. This review aims to provide an overview of the distribution, fate, and environmental and health impacts of food additive nanomaterials in soil and aquatic ecosystems. Some of the major nanomaterials in food additives include titanium dioxide, silver, gold, silicon dioxide, iron oxide, and zinc oxide. Ingestion of food products containing food additive nanomaterials via dietary intake is considered to be one of the major pathways of human exposure to nanomaterials. Food additive nanomaterials reach the terrestrial and aquatic environments directly through the disposal of food wastes in landfills and the application of food waste-derived soil amendments. A significant amount of ingested food additive nanomaterials (> 90 %) is excreted, and these nanomaterials are not efficiently removed in the wastewater system, thereby reaching the environment indirectly through the disposal of recycled water and sewage sludge in agricultural land. Food additive nanomaterials undergo various transformation and reaction processes, such as adsorption, aggregation-sedimentation, desorption, degradation, dissolution, and bio-mediated reactions in the environment. These processes significantly impact the transport and bioavailability of nanomaterials as well as their behaviour and fate in the environment. These nanomaterials are toxic to soil and aquatic organisms, and reach the food chain through plant uptake and animal transfer. The environmental and health risks of food additive nanomaterials can be overcome by eliminating their emission through recycled water and sewage sludge.

Deciphering fluorescent and molecular fingerprint of dissolved organic matter leached from microplastics in water

Despite extensive research into the presence and behavior of microplastics (MPs) in the environment, limited attention has been given to the investigation of the characteristics of dissolved organic matter (DOM) that leaches from MPs (MPs-DOM). Herein, two frequently encountered plastic particles in aquatic environments, specifically polyethylene terephthalate (PET)- and polyethylene (PE)-MPs, were subjected to leaching in the aquatic settings for seven days, both in the absence of light and under UV irradiation. Measurements of dissolved organic carbon (DOC) indicated that UV exposure enhanced the liberation of DOM from PET-MPs, while PE-MPs did not exhibit such leaching. After UV treatment for seven days, the DOM released from PET-MPs increased by 25 times, while that from PE-MPs remained almost unchanged. Then, the molecular diversity and the evolving formation of DOM originating from different MPs were comprehensively analyzed with fluorescence excitation-emission matrix (EEM) and Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). Specifically, both PET- and PE-DOM exhibited three fluorescence signatures, with the predominant C1 (tryptophan-like) component showing a decline in PET-DOM and a rise in PE-DOM during aging. The FT-ICR-MS analysis unveiled that PET-DOM grew more recalcitrant under UV exposure, while PE-DOM became increasingly labile. In brief, UV irradiation influences MPs-DOM release and transformation differently, depending on the plastic composition. This highlights the significance of exploring MPs-DOM transformation in securing environmental safety.

Plastisphere characterization in habitat of the highly endangered Shinisaurus crocodilurus: Bacterial composition, assembly, function and the comparison with surrounding environment

Plastisphere is a new niche for microorganisms that complicate the ecological effects of plastics, and may profoundly influence biodiversity and habitat conservation. The DaGuishan National Nature Reserve, one of the largest habitats of the highly endangered crocodile lizard (Shinisaurus crocodilurus), is experiencing plastic pollution without sufficient attention. Here, plastisphere collected from captive tanks of crocodile lizards in this nature reserve was characterized for the first time. Three types of plastic (PE-PP, PE1, and PE2) together with the surrounding water and soil samples, were collected, and 16S rRNA sequencing technology was used to characterize the bacterial composition. The results demonstrated that plastisphere was driven by stochastic process and had a distinct bacterial community with higher diversity than that in surrounding water (p < 0.05). Bacteria related to nitrogen and carbon cycles (Pseudomonas psychrotolerans, Methylobacterium-Methylorubrum) were more abundant in plastisphere than in water or soil (p < 0.05). More importantly, plastics recruited pathogens and those bacteria function in antibiotic resistant genes (ARGs) coding. Bacteria related to polymer degradation also proliferated in plastisphere, especially Bacillus subtilis with a fold change of 42.01. The PE2 plastisphere, which had the lowest diversity and was dominated by Methylobacterium-Methylorubrum differed from PE 1 and PE-PP plastispheres totally. Plastics' morphology and aquatic nutrient levels contributed to the heterogeneity of different plastispheres. Overall, this study demonstrated that plastispheres diversify in composition and function, affecting ecosystem services directly or indirectly. Pathogens and bacteria related to ARGs expression enriched in the plastisphere should not be ignored because they may threaten the health of crocodile lizards by increasing the risk of infection. Plastic pollution control should be included in conservation efforts for crocodile lizards. This study provides new insights into the potential impacts of plastisphere, which is important for ecological risk assessments of plastic pollution in the habitats of endangered species.

Plastitar in the Mediterranean Sea: New records and the first geochemical characterization of these novel formations

A new geological formation consisting of plastic debris admixed to petroleum oil residue, termed "plastitar", has been recently described in the Canary Islands. Here, we report its widespread occurrence across the Mediterranean coast and new insights into its biogeochemical composition. Specifically, we found marked differences in the diagenetic stable indicator profiles, suggesting a heterogeneous seeps provenance. Moreover, the 801 plastic particles found in the 1372 g of tar surveyed, with a maximum concentration of 2.0 items/g, showed interesting patterns in the tar mat, with nurdles predominantly layered in the external of the tar mat and lines in the inner core. Overall, the collected observation suggests that tar entraps plastics through a stepwise process and is a sink for them.

Compound effect and mechanism of oxidative damage induced by nanoplastics and benzo [a] pyrene

Nanoplastics and polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in soil environments. In order to objectively evaluate the toxic interaction between polystyrene nanoplastics (PS NPs) and benzo [a] pyrene (BaP), oxidative damage at the level of earthworm cells and biomacromolecules was investigated by experiments combined with molecular dynamics simulation. Studies on cells reveal that PS NPs and BaP had synergistic toxicity when it came to causing oxidative stress. Cellular reactive oxygen species (ROS) levels under combined pollutant exposure were 24% and 19% higher, respectively than when PS NPs and BaP were exposed alone (compared to the blank group). In addition, BaP and PS NPs inhibited the ability of CAT to decompose H2O2 by affecting the structure of the proximal amino acid Tyr 357 in the active center of CAT, which exacerbated oxidative stress to a certain extent. Therefore, the synergistic toxic effect of BaP and PS NPs is due to the mutual complement of the two to the induction of protein structural looseness, and the strengthening of the stability of the conjugate (CAT-BaP-PS) under the weak interaction. This work provides a new perspective and approach on how to talk about the toxicity of combined pollutants.

Heavy metal pollution in Mongolian-Manchurian grassland soil and effect of long-range dust transport by wind

Grasslands provide a range of valuable ecosystem services, but they are also particularly fragile ecosystems easily threatened by human activities, such as long-term open-pit mining and related industrial activities. In grassland area, dust containing heavy metal(loid)s generated by mines may further migrate to remote places, but few studies have focused on the long-range transport of contaminants as an important pollution source. In the present study, one of the largest and most intact grassland ecosystems, the Mongolian-Manchurian steppe, was selected to investigate its pollution status and track potential sources. A total of 150 soil samples were collected to explore reginal distribution of nine heavy metal(loid)s that has potential risk in grassland. We conducted a combined multi-variant analysis of positive matrix factorization (PMF) and machine learning, which foregrounded the source of long-range transport of contaminants and inspired the hypothesis of a novel stochastic model to describe contaminants distribution. Results showed four different sources accounting for 44.44% (parent material), 20.28% (atmospheric deposition), 20.39% (farming), and 14.89% (transportation) of the total concentration, respectively. Factor 2 indicated that coal surface mining lead to a significant enrichment of As and Se with their concentration far above the global average level, which was different from other reported grassland areas. Machine learning results further confirmed that atmospheric and topographic features were their contamination controlling factors. The model results proposed that As, Se and Cu released by surface mining will be transported over long distance under prevailing monsoon, until finally deposited in the windward slope of mountain due to terrain obstruction. The long-range transport by wind and deposition of contaminants may be a prevailing phenomenon in temperate grassland, making it a pollution source that cannot be ignored. Evidence from this study reveals the urgency of precautions for fragile grassland ecosystems around industrial areas and provides a basis for its management and risk control policies.