Leachable Additives of Tire Particles Explain the Shift in Microbial Community Composition and Function in Coastal Sediments

The spatio-temporal accumulation of 6 PPD-Q in greenbelt soils and its effects on soil microbial communities

6 PPD-Q (6 PPD-Quinone) is an ozone-induced byproduct derived from the degradation of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6 PPD), commonly found in road dust resulting from tire wear. However, the extent of 6 PPD-Q pollution in urban soil remains unclear. This study investigates the spatial and temporal accumulation patterns of 6 PPD-Q in greenbelt soils in Ningbo, and explores the correlation between 6 PPD-Q accumulation and soil microbial community composition and functions. Our findings indicate that 6 PPD-Q is present (ranging from 0.85 to 12.58 μg/kg) in soil samples collected from both sides of urban traffic arteries. Soil fungi exhibit higher sensitivity to 6 PPD-Q accumulation compared to bacteria, and associated fungi (Basidiomycota) may be potential biomarkers for environmental 6 PPD-Q contamination. Co-occurrence network analysis reveals that the bacterial microbial network in summer exhibits greater stability and resilience in response to 6 PPD-Q inputs than in winter. However, 6 PPD-Q accumulation disrupts the network structure of fungal communities to some extent, leading to reduced diversity in fungal microbial communities. Long-term accumulation of 6 PPD-Q weakens the nitrogen and phosphorus cycling potential within urban soil, while the enhancement of carbon cycling may further promote 6 PPD-Q degradation in urban soil. Taken together, this study provides new insights into the ecological risks of 6 PPD-Q in urban soils.

Beyond plastic pollution: Unveiling chemical release from plastic debris in river water and seawater using non-target screening

Oceans and rivers are predominant sinks, reservoirs, and carriers of plastic debris that are proposed to be long term sources of a variety of contaminants in the environments. This research unveiled kinetics of chemical releases from plastic debris in freshwater and marine environment via artificial river water (ARW) and seawater (ASW) in combination of nontarget screening. Chemical leaching from PVC cord particles in the ARW and ASW basically followed the first order kinetics, reaching pseudo-equilibrium in 30d and 14d, respectively, associated with both particle surface - water partitioning and inner-particle diffusion of chemicals. Dissolved organic carbon, finer size, and weathering of plastic particles might enhance whereas metal ions potentially hinder chemical releases from plastic debris in waters, respectively. Salinity and pH showed moderate effects on chemical leaching. In addition, chemicals' physiochemical properties might also affect their leaching behavior. Hundreds to thousands of chemicals would be released from plastic debris in days once entering waters, among which > 80% were unknown with rare or no information about eco-toxicity and environmental fate, posing unpredicted risks to the environment. Furthermore, new chemicals may keep being released with increasing weathering and extending retention time of plastics in waters, leading to increases in both numbers and complexities of released chemicals. Chemical leaching from plastics showed product-dependence and certain differences in freshwater and seawater. Large numbers of unknown chemicals potentially released from plastic debris in rivers, lakes, and oceans and subsequent environmental risks warrant in-depth research.

Ecological linkages between top-down designed benzothiazole-degrading consortia and selection strength: From performance to community structure and functional genes

The inefficient biodegradation and incomplete mineralization of nitrogenous heterocyclic compounds (NHCs) have emerged as a pressing environmental concern. The top-down design offers potential solutions to this issue by targeting improvements in community function, but the ecological linkages between selection strength and the structure and function of desired microbiomes remain elusive. Herein, the integration of metagenomics, culture-based approach, non-targeted metabolite screening and enzymatic verification experiments revealed the effect of enrichment concentration on the top-down designed benzothiazole (BTH, a typical NHC)-degrading consortia. Significant differences were observed for the degradation efficiency and community structure under varying BTH selections. Notably, the enriched consortia at high concentrations of BTH were dominated by genus Rhodococcus, possessing higher degradation rates. Moreover, the isolate Rhodococcus pyridinivorans Rho48 displayed excellent efficiencies in BTH removal (98 %) and mineralization (∼ 60 %) through the hydroxylation and cleavage of thiazole and benzene rings, where cytochrome P450 enzyme was firstly reported to participate in BTH conversion. The functional annotation of 460 recovered genomes from the enriched consortia revealed diverse interspecific cooperation patterns that accounted for the BTH mineralization, particularly Nakamurella and Micropruina under low selection strength, and Rhodococcus and Marmoricola under high selection strength. This study highlights the significance of selection strength in top-down design of synthetic microbiomes for degrading refractory organic pollutants, providing valuable guidance for designing functionally optimized microbiomes used in environmental engineering.

Microplastic-contamination can reshape plant community by affecting soil properties

Microplastics, as emerging contaminants, pose a serious threat to terrestrial ecosystems, yet their impact on plant communities remains largely unexplored. This study utilized the soil seed bank to establish naturally germinated plant communities and investigated the effects of polyethylene (PE) and polypropylene (PP) on community characteristics. Additionally, the study aimed to elucidate the mechanisms by which variations in soil properties influenced plant community. The results indicated that microplastics led to a significant increase in soil available potassium (AK), likely due to alterations in soil microorganism proliferation. Furthermore, microplastics caused a decrease in soil salinity, total phosphorus (TP), and ammonium nitrogen (AN). Additionally, plant community composition shifted, resulting in reduced stability and niche breadth of dominant species. Microplastics also impacted niche overlap and interspecific associations among dominant species, possibly due to the reduced accessibility of resources for dominant species. Salinity, AK, and TP were identified as major drivers of changes in niche breadth, niche overlap, and community stability, with TP exerting the strongest impact on plant community composition. These findings provide valuable insights for the restoration of plant communities in coastal saline-alkali wetland contaminated by microplastics.

Microplastics-biofilm interactions in biofilm-based wastewater treatment processes: A review

Microplastics, pervasive contaminants from plastic, present significant challenges to wastewater treatment processes. This review critically examines the interactions between microplastics and biofilm-based treatment technologies, specifically focusing on the concepts of "biofilm on microplastics" and "microplastics in biofilm". It discusses the implications of these interactions in contaminant removal and process performance. Advanced characterization techniques, including morphological characterization, chemical composition analysis, and bio-information analysis, are assessed to elucidate the complex interplay between microplastics and biofilms within biofilters, biological aerated filters (BAFs), rotating biological contactors (RBCs), and moving bed biofilm reactors (MBBRs). This review synthesizes current research findings, highlighting that microplastics can either hinder or enhance the treatment processes, contingent on their concentration, physicochemical properties, and the specific biofilm technology employed. The insights gained from this review are essential for developing strategies to mitigate the adverse effects of microplastics and for optimizing the design and operation of wastewater treatment.

Hotspots lurking underwater: Insights into the contamination characteristics, environmental fates and impacts on biogeochemical cycling of microplastics in freshwater sediments

The widespread presence of microplastics (MPs) in aquatic environments has become a significant concern, with freshwater sediments acting as terminal sinks, rapidly picking up these emerging anthropogenic particles. However, the accumulation, transport, degradation and biochemical impacts of MPs in freshwater sediments remain unresolved issues compared to other environmental compartments. Therefore, this paper systematically revealed the spatial distribution and characterization information of MPs in freshwater (rivers, lakes, and estuaries) sediments, in which small-size (<1 mm), fibers, transparent, polyethylene (PE), and polypropylene (PP) predominate, and the average abundance of MPs in river sediments displayed significant heterogeneity compared to other matrices. Next, the transport kinetics and drivers of MPs in sediments are summarized, MPs transport is controlled by the particle diversity and surrounding environmental variability, leading to different migration behaviors and transport efficiencies. Also emphasized the spatio-temporal evolution of MPs degradation processes and biodegradation mechanisms in sediments, different microorganisms can depolymerize high molecular weight polymers into low molecular weight biodegradation by-products via secreting hydrolytic enzymes or redox enzymes. Finally, discussed the ecological impacts of MPs on microbial-nutrient coupling in sediments, MPs can interfere with the ecological balance of microbially mediated nutrient cycling by altering community networks and structures, enzyme activities, and nutrient-related functional gene expressions. This work aims to elucidate the plasticity characteristics, fate processes, and potential ecological impact mechanisms of MPs in freshwater sediments, facilitating a better understanding of environmental risks of MPs in freshwater sediments.

Cocktail effects of tire wear particles leachates on diverse biological models: A multilevel analysis

Tire wear particles (TWP) stand out as a major contributor to microplastic pollution, yet their environmental impact remains inadequately understood. This study delves into the cocktail effects of TWP leachates, employing molecular, cellular, and organismal assessments on diverse biological models. Extracted in artificial seawater and analyzed for metals and organic compounds, TWP leachates revealed the presence of polyaromatic hydrocarbons and 4-tert-octylphenol. Exposure to TWP leachates (1.5 to 1000 mg peq L-1) inhibited algae growth and induced zebrafish embryotoxicity, pigment alterations, and behavioral changes. Cell painting uncovered pro-apoptotic changes, while mechanism-specific gene-reporter assays highlighted endocrine-disrupting potential, particularly antiandrogenic effects. Although heavy metals like zinc have been suggested as major players in TWP leachate toxicity, this study emphasizes water-leachable organic compounds as the primary causative agents of observed acute toxicity. The findings underscore the need to reduce TWP pollution in aquatic systems and enhance regulations governing highly toxic tire additives.

Undisclosed contribution of microbial assemblages selectively enriched by microplastics to the sulfur cycle in the large deep-water reservoir

The accumulation of microplastics in reservoirs due to river damming has drawn considerable attention due to their potential impacts on elemental biogeochemical cycling at the watershed scale. However, the effects of plastisphere communities on the sulfur cycle in the large deep-water reservoir remain poorly understood. Here, we collected microplastics and their surrounding environmental samples in the water and sediment ecosystems of Xiaowan Reservoir and found a significant spatiotemporal pattern of microplastics and sulfur distribution in this Reservoir. Based on the microbial analysis, plastic-degrading taxa (e.g., Ralstonia, Rhodococcus) involved in the sulfur cycle were enriched in the plastisphere of water and sediment, respectively. Typical thiosulfate oxidizing bacteria Limnobacter acted as keystone species in the plastisphere microbial network. Sulfate, oxidation reduction potential and organic matter drove the variations of the plastisphere. Environmental filtration significantly affected the plastisphere communities, and the deterministic process dominated the community assembly. Furthermore, predicted functional profiles related to sulfur cycling, compound degradation and membrane transport were significantly enriched in the plastisphere. Overall, our results suggest microplastics as a new microbial niche exert different effects in water and sediment environments, and provide insights into the potential impacts of the plastisphere on the sulfur biogeochemical cycle in the reservoir ecosystem.

Aging increases the particulate- and leachate-induced toxicity of tire wear particles to microalgae

The toxic effects of tire wear particles (TWPs) on organisms have attracted widespread concerns over the past decade. However, the underlying toxicity mechanism of TWPs, especially aged TWPs to marine microalgae remains poorly understood. This study investigated the physiological and metabolic responses of Phaeodactylum tricornutum to different concentrations of TWPs (Experiment 1), virgin and differently aged TWPs (Experiment 2) as well as their leachates and leached particles (Experiment 3). Results demonstrated that TWPs promoted the growth of microalgae at low concentrations (0.6 and 3 mg L-1) and inhibited their growth at high concentrations (15 and 75 mg L-1). Moreover, aged TWPs induced more profound physiological effects on microalgae than virgin TWPs, including inhibiting microalgae growth, decreasing the content of Chla, promoting photosynthetic efficiency, and causing oxidative damage to algal cells. Untargeted metabolomics analysis confirmed that aged TWPs induced more pronounced metabolic changes than virgin TWPs. This study represented the first to demonstrate that both particulate- and leachate-induced toxicity of TWPs was increased after aging processes, which was confirmed by the changes in the surface morphology of TWPs and enhanced release of additives. Through the significant correlations between the additives and the microalgal metabolites, key additives responsible for the shift of microalgal metabolites were identified. These results broaden the understanding of the toxicity mechanism of aged TWPs to microalgae at the physiological and metabolic levels and appeal for considering the effects of long-term aging on TWP toxicity in risk assessment of TWPs.

Biomonitoring of microplastics, anthropogenic microfibres and glass retroreflective beads by marine macroalgae

Microplastics and other microscopic debris are a concern in the coastal environment but measurements in the water column and sediment are often problematic and rely on non-standardised and highly variable methodologies. To this end, we explore the potential of different species of temperate-cold marine macroalgae as passive biomonitors of anthropogenic microparticles at three contrasting locations in southwest England. Specifically, fronds from samples of fucoids and Ulva lactuca (n = 9 in total, and three from each location) have been sectioned and analysed directly under a microscope and anthropogenic microparticles counted and subsequently characterised for chemical composition. Microparticles were heterogeneously distributed throughout sections from the same sample. However, on a dry weight basis, combined microparticle concentrations for each sample ranged from about 7.5 g-1 to 110 g-1, and from about 0.2 cm-2 to 0.9 cm-2, and for a given species were higher in samples from a semi-enclosed harbour and urban beach than in samples from a protected beach facing the open sea. These values compare with published concentrations of microplastics and microfibres reported for the regional water column on the order of 0.1 m-3. Most particles were cellulosic (e.g., rayon) and petroleum-based (mainly polyester and polyethylene terephthalate) fibres but plastic fragments were also present on most samples. Glass retroreflective beads derived from road markings were also present at up to 18 g-1 on fucoids from the urban beach because of its proximity to a stormwater effluent. Most microparticles were adhered to the smooth parts of the macroalgal surface but some displayed wrapping around edges and creases or entrapment by appendages. The practical and environmental implications of macroalgae passively capturing significant quantities of anthropogenic microparticles are discussed.

Effects of microplastics on sedimentary geochemical properties and microbial ecosystems combined with hydraulic disturbance

Microplastics (MPs) pollution is widely investigated owing to its potential threats to river ecosystems. However, it remains unclear whether hydraulic disturbance deepens or mitigates the effects of MPs-contaminated sediments on the river environment. Herein, we studied the impact of sediment aggregates, organic matter, and enzyme activity, with emphasis on microbial community structure and function in sediments exposed to MPs (1 %, 5 %, and 10 % w/w) in conjunction with hydraulic disturbance. The experimental results showed that the influence of MPs on the sediment under hydraulic disturbance is more significant than that of static culture, especially for various environmental factors (MWD, MBC, and sucrase activity etc.). The proportions of the >0.05 mm-fraction aggregates increased from 74-76 % to 82-88 % in the sediment throughout the entire disturbance process. It has been found that the disturbance generally promotes the interaction between MPs and sediments. FAPROTAX analysis demonstrated that the disturbance reduced the difference in effects on microbial functional genes between the control group and the MPs-added groups by up to 10 times, suggesting that the effects of disturbance on MPs-contaminated sediments are relatively complex. This work provides new insights into the effects of hydraulic disturbance on physicochemical properties and microbial communities of MPs-contaminated sediment.

Synthetic and natural rubber associated chemicals drive functional and structural changes as well as adaptations to antibiotics in in vitro marine microbiomes

The leaching of additives from plastics and elastomers (rubbers) has raised concerns due to their potential negative impacts on the environment and the development of antibiotic resistance. In this study, we investigated the effects of chemicals extracted from two types of rubber on microbiomes derived from a benthic sea urchin and two pelagic fish species. Additionally, we examined whether bacterial communities preconditioned with rubber-associated chemicals displayed adaptations to antibiotics. At the highest tested concentrations of chemicals, we observed reduced maximum growth rates and yields, prolonged lag phases, and increased alpha diversity. While the effects on alpha and beta diversity were not always conclusive, several bacterial genera were significantly influenced by chemicals from the two rubber sources. Subsequent exposure of sea urchin microbiomes preconditioned with rubber chemicals to the antibiotic ciprofloxacin resulted in decreased maximum growth rates. This indicates a more sensitive microbiome to ciprofloxacin when preconditioned with rubber chemicals. Although no significant interaction effects between rubber chemicals and ciprofloxacin exposure were observed in bacterial alpha and beta diversity, we observed log-fold changes in two bacterial genera in response to ciprofloxacin exposure. These findings highlight the structural and functional alterations in microbiomes originating from various marine species when exposed to rubber-associated chemicals and underscore the potential risks posed to marine life.

Tire particles and its leachates: Impact on antibiotic resistance genes in coastal sediments

Tire particles (TPs), a significant group of microplastics, can be discharged into the coastal environments in various ways. However, our understanding of how TPs impact the antibiotic resistance and pathogenic risks of microorganisms in coastal sediments remains limited. In this study, we used metagenomics to investigate how TPs and their leachates could affect the prevalence of antibiotic resistance genes (ARGs), virulence factor genes (VFGs), and their potential risks to the living creatures such as soil invertebrates and microorganisms in the coastal sediments. We discovered that TP addition significantly increased the abundance and diversity of ARGs and VFGs in coastal sediments, with raw TPs displayed higher impacts than TP leachates and TPs after leaching on ARGs and VFGs. With increasing TP exposure concentrations, the co-occurrence frequency of ARGs and mobile genetic elements (MGEs) in the same contig also increased, suggesting that TPs could enhance the dispersal risk of ARGs. Our metagenome-based binning analysis further revealed that exposure to TPs increased the abundance of potentially pathogenic antibiotic-resistant bacteria (PARB). In addition, chemical additives of TP leachates (e.g., Zn and N-cyclohexylformamide) significantly affected the changes of ARGs in the pore water. In summary, our study provides novel insights into the adverse effects of TP pollutions on aggravating the dissemination and pathogenic risks of ARGs and PARB in the coastal environment.

Tire materials disturb transformations of nitrogen compounds and affect the structure of biomass in aerobic granular sludge reactors

Tire materials (TMs) present a notable hazard due to their potential to release harmful chemicals and microplastics into the environment. They can infiltrate wastewater treatment plants, where their effects remain inadequately understood, raising concerns regarding their influence on treatment procedures. Thus, this study investigated the impact of TMs in wastewater (10, 25, 50 mg/L) on wastewater treatment efficiency, biomass morphology, and microbial composition in aerobic granular sludge (AGS) reactors. TM dosage negatively correlated with nitrification and denitrification efficiencies, reducing overall nitrogen removal, but did not affect the efficiency of chemical-oxygen-demand removal. The presence of TMs increased the diameter of the granules due to TM incorporation into the biomass. The most frequently leached additives from TMs were N-(1,3-dimethylbutyl)-N'-phenyl-1,4-phenylenediamine, benzothiazole (BTH), and 2-hydroxybenzothiazole. In the treated wastewater, only BTH and aniline were detected in higher concentrations, which indicates that tire additives were biodegraded by AGS. The microbial community within the AGS adapted to TMs and their chemicals, highlighting the potential for efficient degradation of tire additives by bacteria belonging to the genera Rubrivivax, Ferruginibacter, and Xanthomonas. Additionally, our research underscores AGS's ability to incorporate TMs into biomass and effectively biodegrade tire additives, offering a promising solution for addressing environmental concerns related to TMs.

Metagenomics reveals the influence of small microplastics on microbial communities in coastal sediments

The ecological impact of microplastics (MPs) in coastal environments has been widely studied. However, the influence of small microplastics in the actual environment is often overlooked due to measurement challenges. In this study, Hangzhou Bay (HZB), China, was selected as our study area. High-throughput metagenomic sequencing and micro-Raman spectrometry were employed to analyze the microbial communities and microplastics of coastal sediment samples, respectively. We aimed to explore the ecological impact of MPs with small sizes (≤ 100 μm) in real coastal sediment environments. Our results revealed that as microplastic size decreased, the environmental behavior of MPs underwent alterations. In the coastal sediments, no significant correlations were observed between the detected MPs and the whole microbial communities, but small MPs posed potential hazards to eukaryotic communities. Moreover, these small MPs were more prone to microbial degradation and significantly affected carbon metabolism in the habitat. This study is the first to reveal the comprehensive impact of small MPs on microbial communities in a real coastal sediment environment.

Farmland Microhabitat Mediated by a Residual Microplastic Film: Microbial Communities and Function

How the plastisphere mediated by the residual microplastic film in farmlands affects microhabitat systems is unclear. Here, microbial structure, assembly, and biogeochemical cycling in the plastisphere and soil in 33 typical farmland sites were analyzed by amplicon sequencing of 16S rRNA genes and ITS and metagenome analysis. The results indicated that residual microplastic film was colonized by microbes, forming a unique niche called the plastisphere. Notable differences in the microbial community structure and function were observed between soil and plastisphere. Residual microplastic film altered the microbial symbiosis and assembly processes. Stochastic processes significantly dominated the assembly of the bacterial community in the plastisphere and soil but only in the plastisphere for the fungal community. Deterministic processes significantly dominated the assembly of fungal communities only in soil. Moreover, the plastisphere mediated by the residual microplastic film acted as a preferred vector for pathogens and microorganisms associated with plastic degradation and the nitrogen and sulfur cycle. The abundance of genes associated with denitrification and sulfate reduction activity in the plastisphere was pronouncedly higher than that of soil, which increase the potential risk of nitrogen and sulfur loss. The results will offer a scientific understanding of the harm caused by the residual microplastic film in farmlands.

Effects of polyethylene, polylactic acid, and tire particles on the sediment microbiome and metabolome at high and low temperatures

Global warming has led to a high incidence of extreme heat events, and the frequent occurrence of extreme heat events has had extensive and far-reaching impacts on wetland ecosystems. The widespread distribution of plastics in the environment, including polyethylene (PE), polylactic acid (PLA), and tire particles (TPs), has caused various environmental problems. Here, high-throughput sequencing techniques and metabolomics were used for the first time to investigate the effects of three popular microplastic types: PE, PLA, and TP, on the sediment microbiome and the metabolome at both temperatures. The microplastics were incorporated into the sediment at a concentration of 3% by weight of the dry sediment (wt/wt), to reflect environmentally relevant conditions. Sediment enzymatic activity and physicochemical properties were co-regulated by both temperatures and microplastics producing significant differences compared to controls. PE and PLA particles inhibited bacterial diversity at low temperatures and promoted bacterial diversity at high temperatures, and TP particles promoted both at both temperatures. For bacterial richness, only PLA showed inhibition at low temperature; all other treatments showed promotion. PE, PLA, and TP microplastics changed the community structure of sediment bacteria, forming two clusters at low and high temperatures. Furthermore, PE, PLA, and TP changed the sediment metabolic profiles, producing differential metabolites such as lipids and molecules, organic heterocyclic compounds, and organic acids and their derivatives, especially TP had the most significant effect. These findings contribute to a more comprehensive understanding of the potential impact of microplastic contamination.IMPORTANCEIn this study, we added 3% (wt/wt) microplastic particles, including polyethylene, polylactic acid, and tire particles, to natural sediments under simulated laboratory conditions. Subsequently, we simulated the sediment microbial and ecosystem responses under different temperature conditions by incubating them for 60 days at 15°C and 35°C, respectively. After synthesizing these results, our study strongly suggests that the presence of microplastics in sediment ecosystems and exposure under different temperature conditions may have profound effects on soil microbial communities, enzyme activities, and metabolite profiles. This is important for understanding the potential hazards of microplastic contamination on terrestrial ecosystems and for developing relevant environmental management strategies.

Temperature-dependent effects of microplastics on sediment bacteriome and metabolome

The increasing prevalence of microplastics in the environment has become a concern for various ecosystems, including wetland ecosystems. Here, we investigated the effects of three popular microplastic types: polyethylene, polylactic acid, and tire particles at 5 °C and 25 °C on the sediment microbiome and metabolome at the 3% (w/w) level. Results indicated that temperature greatly influenced catalase and neutral phosphatase activities, whereas the type of microplastic had a more significant impact on urease and dehydrogenase activities. The addition of microplastic, especially tire particles, increased microbial diversity and significantly altered the microbial community structure and metabolic profile, leading to the formation of different clusters of microbial communities depending on the temperature. Nonetheless, the effect of temperature on the metabolite composition was less significant. Functional prediction showed that the abundance of functional genes related to metabolism and biogeochemical cycling increased with increasing temperature, especially the tire particles treatment group affected the nitrogen cycling by inhibiting ureolysis and nitrogen fixation. These observations emphasize the need to consider microplastic type and ambient temperature to fully understand the ecological impact of microplastics on microbial ecosystems.

Photo-oxidation of Micro- and Nanoplastics: Physical, Chemical, and Biological Effects in Environments

Micro- and nanoplastics (MNPs) are attracting increasing attention due to their persistence and potential ecological risks. This review critically summarizes the effects of photo-oxidation on the physical, chemical, and biological behaviors of MNPs in aquatic and terrestrial environments. The core of this paper explores how photo-oxidation-induced surface property changes in MNPs affect their adsorption toward contaminants, the stability and mobility of MNPs in water and porous media, as well as the transport of pollutants such as organic pollutants (OPs) and heavy metals (HMs). It then reviews the photochemical processes of MNPs with coexisting constituents, highlighting critical factors affecting the photo-oxidation of MNPs, and the contribution of MNPs to the phototransformation of other contaminants. The distinct biological effects and mechanism of aged MNPs are pointed out, in terms of the toxicity to aquatic organisms, biofilm formation, planktonic microbial growth, and soil and sediment microbial community and function. Furthermore, the research gaps and perspectives are put forward, regarding the underlying interaction mechanisms of MNPs with coexisting natural constituents and pollutants under photo-oxidation conditions, the combined effects of photo-oxidation and natural constituents on the fate of MNPs, and the microbiological effect of photoaged MNPs, especially the biotransformation of pollutants.

Effects of microplastics on cold seep sediment prokaryotic communities

Cold seep sediments are an important reservoir of microplastics (MPs) whose impact on the structure and function of prokaryotic community is not well understood. In this study, the impact of 0.2% and 1% (w/w) polyethylene (PE), polystyrene (PS), and polypropylene (PP) MPs on the cold seep sediment prokaryotic community was investigated in a 120-day laboratory incubation experiment. The results revealed that exposure to MPs altered sedimentary chemical properties in a type- and concentration-dependent manner. Furthermore, MPs significantly altered the structure of bacterial community, with some MPs degradation-associated bacterial phyla significantly increasing (p < 0.05). However, in the case of archaea, the changes in the structure of microbial community were less pronounced (p > 0.05). Co-occurrence network analysis revealed that the addition of MPs reduced the network complexity, while PICRUSt2 and FAPROTAX analyses suggested that 0.2% PP and 1% PS MPs had the most significant effects on the nitrogen and carbon cycles (p < 0.05). Overall, this study provides new insights into the effects of MPs on the structure and function of microbial communities in cold seep sediments.

Sulfate radical-based advanced oxidation process effects on tire wear particles aging and ecotoxicity

Tire wear particles (TWPs) are widely distributed in natural water and pose as major pollutants in aquatic environments. In this study, heat-activated persulfate (HPT) and ultraviolet-activated persulfate treatments (UPT) were employed to investigate the influence of sulfate radical (SO4-•)-based advanced oxidation process (SAOPs) on TWP physicochemical properties and to clarify their ecotoxic effects in laboratory-level studies. Results showed that the specific surface areas of TWPs increased after UPT but decreased after HPT. In terms of chemical properties, the increase of oxygen-containing functional groups on the surfaces of TWPs was more evident in UPT than that in HPT. The atrazine (ATZ) adsorption capacity of TWPs after HPT and UPT was increased compared with the untreated TWPs. Atrazine adsorbed by TWPs was easily resolved and released in artificial intestinal fluid (1.89-2.08 mg/g) and artificial gastric fluid (1.60-2.04 mg/g) conditions. Acute toxicity experiments of Photobacterium phosphoreum and SEM-EDS detection results suggested that various heavy metals (e.g., Zn2+, Cu2+) in the TWPs would be released into the water system in SAOPs. ATZ released from TWPs that adsorbed ATZ herbicide, rather than TWPs themselves, had a negative effect on aquatic plant growth (e.g., C. vulgaris). The leaching solution of oxidized TWPs (after HPT and UPT) showed a more significant inhibition effect on the zebrafish survival compared with that of untreated TWPs, which was possibly caused by the generation of oxidation byproducts such as N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine-quinone.

Integrating metabolomics and high-throughput sequencing to investigate the effects of tire wear particles on mung bean plants and soil microbial communities

Tire wear particles (TWPs) generated by vehicle tires are ubiquitous in soil ecosystems, while their impact on soil biota remains poorly understood. In this study, we investigated the effects of TWPs (0.1%, 0.7%, and 1.5% of dry soil weight) on the growth and metabolism of mung bean (Vigna radiata) plants over 32 days in soil pots. We found that TWPs-treated soils had high levels of heavy metals and polycyclic aromatic hydrocarbons (PAHs). However, there was no significant impact of TWPs exposure on plant growth, suggesting that mung bean plants have a degree of tolerance to TWPs. Despite the lack of impact on plant growth, exposure to TWPs had significant effects on soil enzyme activities, with a decrease of over 50% in urease and dehydrogenase activity. Furthermore, TWPs exposure resulted in marked changes in the plant metabolite profile, including altered levels of sugars, carboxylic acids, and amino acids, indicating altered nitrogen and amino acid-related metabolic pathways. TWPs exposure also disrupted the rhizospheric and bulk soil microbiota, with a decrease in the abundance of bacterial (Blastococcus) and fungal (Chaetomium) genera involved in nitrogen cycles and suppressing plant diseases. In summary, our study provides new insights into the effects of TWPs on plants and soil, highlighting the potential ecological consequences of TWPs pollution in terrestrial ecosystems and underscoring the need for further research in this area.

Responses of soil and collembolan (Folsomia candida) gut microbiomes to 6PPD-Q pollution

The potential risk of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine quinone (6PPD-Q) to soil organisms remains poorly understood. Here we showed that 6PPD-Q pollution inhibited the survival of collembolans (Folsomia candida) with the chronic median lethal concentration (LC50) of 16.31 μg kg-1 in a 28-day soil culture. The microbe-microbe interactions between abundant taxa in soil and collembolan gut helped alleviate the negative impact of 6PPD-Q on soil microbial community, while rare taxa contributed to maintaining microbial network complexity and stability under 6PPD-Q stresses. Gammaproteobacteria, Alphaproteobacteria and Actinobacteria in the gut of both adult and juvenile collembolans were identified as potential indicators for 6PPD-Q exposure. Such responses were accompanied by increases in the relative abundances of genes involved in nutrient cycles and their interactions between soil and collembolan gut microbiomes, which enhanced nitrogen and carbon turnover in 6PPD-Q polluted soil, potentially alleviating the stresses caused by 6PPD-Q. Overall, this study sheds new light on the toxicity of 6PPD-Q to soil organisms and links 6PPD-Q stresses to microbial responses and soil functions, thus highlighting the urgency of assessing its potential risk to the terrestrial ecosystem.

Stress response mechanism of wastewater biological nitrogen removal systems to environmentally realistic concentrations of tire wear particles: Contribution of leachable additives

The study quantified the biological nitrogen removal performance, microbial metabolism, microbial community structure, and antioxidant system in a sequencing batch reactor under long-term exposure to 0.1 and 1 mg/L tire wear particles (TWPs), and determined the contribution of leachable additives to the biotoxicity of TWPs. The results showed that long-term exposure to 0.1 and 1 mg/L TWPs inhibited both the nitrification and denitrification processes, reducing ammonia nitrogen (NH4+-N) and total nitrogen (TN) removal efficiency. The TWP leachate (TWPL) primarily contributed to the denitrification inhibition by TWPs, potentially due to the high concentration of zinc ions in the leachable additive. Furthermore, both TWP and TWPL inhibit nitrogen conversion, with TWP inhibiting the generation and transfer of electrons, while TWPL only negatively affects the electron transfer process. This study presents novel insights into the impact of TWPs on biological nitrogen removal, underscoring its broader implications for the geochemical nitrogen cycle.

Effects of microplastics on denitrification and associated N2O emission in estuarine and coastal sediments: insights from interactions between sulfate reducers and denitrifiers

Global estuarine and coastal zones are facing severe microplastics (MPs) pollution. Sulfate reducers (SRB) and denitrifiers (DNB) are two key functional microorganisms in these zones, exhibiting intricate interactions. However, whether and how MPs modulate the interactions between SRB and DNB, with implications for denitrification and associated N2O emissions, remains poorly understood. Here, we simultaneously investigated the spatial response patterns of SRB-DNB interactions and denitrification and associated N2O emissions to different MPs exposure along an estuarine gradient in the Yangtze Estuary. Spatial responses of denitrification to polyvinyl chloride (PVC) and polyadipate/butylene terephthalate (PBAT) MPs exposure were heterogeneous, while those of N2O emissions were not. Gradient-boosted regression tree and multiple regression model analyses showed that sulfide, followed by nitrate (NO3-), controlled the response patterns of denitrification to MPs exposure. Further mechanistic investigation revealed that exposure to MPs resulted in a competitive and toxic (sulfide accumulation) inhibition of SRB on DNB, ultimately inhibiting denitrification at upstream zones with high sulfide but low NO3- levels. Conversely, MPs exposure induced a competitive inhibition of DNB on SRB, generally promoting denitrification at downstream zones with low sulfide but high NO3- levels. These findings advance the current understanding of the impacts of MPs on nitrogen cycle in estuarine and coastal zones, and provide a novel insight for future studies exploring the response of biogeochemical cycles to MPs in various ecosystems.

Microplastics affect C, N, and P cycling in natural environments: Highlighting the driver of soil hydraulic properties

As microplastics (MPs) are organic polymers with a carbon-based framework, they may affect nutrient cycling. Information regarding how MPs influence N, P, and C cycling and the underlying driving force remains lacking. N, P, and C cycling induced by soil hydraulic properties under MPs exposure (including polyethylene (PE), polyvinyl chloride (PVC), polystyrene (PS), polypropylene (PP)) in the natural environment were investigated in this study. MPs exposure increased the soil water content (11.2-84.5%) and reduced bulk density (11.4-42.8%); soil saturated hydraulic conductivity increased by 7.3-69.4% under PP and PE exposure. MPs exposure led to increases in available phosphorus, NO3--N, NH4+-N, and soil organic matter; the bacterial communities related to N and C cycling were significantly changed. Expression levels of soil N and C cycling-related genes were enhanced under low concentrations (0.5% and 2%) of MPs, except PVC; consequently, soil nitrogen storage and organic carbon storage increased by 12-75% and 6.7-93%, respectively. Correlation analyses among soil hydraulic properties, bacterial communities, and functional genes related to nutrient cycling revealed that soil hydraulic properties (including soil water content, saturated water capacity, and soil saturated hydraulic conductivity) were the dominant factors affecting soil N and C storage under MPs exposure.

Ubiquity of Amino Accelerators and Antioxidants in Road Dust from Multiple Land Types: Targeted and Nontargeted Analysis

Amino accelerators and antioxidants (AAL/Os), as well as their degradation derivatives, are industrial additives of emerging concern due to their massive production and use (particularly in rubber tires), pervasiveness in the environment, and documented adverse effects. This study delineated their inter-regional variations in road dust collected from urban/suburb, agricultural, and forest areas, and screened for less-studied AAL/O analogues with high-resolution mass spectrometry. 1,3-Diphenylguanidine (DPG; median concentration: 121 ng/g) and N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine quinone (6PPD-Q; 9.75 ng/g) are the most abundant congeners, constituting 69.7% and 41.4% of the total concentrations of AAL/Os (192 ng/g) and those of AAO transformation products (22.3 ng/g), respectively. The spatial distribution across the studied sites suggests evident human impacts, reflected by the pronounced urban signature and vehicle-originated pollution. Our nontargeted analysis of the most-contaminated road dust identified 16 AAL/O-related chemicals, many of which have received little investigation. Particularly, environmental and toxicological information remains extremely scarce for five out of the 10 most concerning compounds prioritized in terms of their dusty residues and toxicity including 1,2-diphenyl-3-cyclohexylguanidine (DPCG), N,N''-bis[2-(propan-2-yl)phenyl]guanidine (BPPG), and N-(4-anilinophenyl)formamide (PPD-CHO). Additionally, dicyclohexylamine (DChA), broadly applied as an antioxidant in automobile products, had an even greater median level than DPG. Therefore, future research on their health risks and (eco)toxic potential is of high importance.

Addressing chemical pollution in biodiversity research

Climate change, biodiversity loss, and chemical pollution are planetary-scale emergencies requiring urgent mitigation actions. As these "triple crises" are deeply interlinked, they need to be tackled in an integrative manner. However, while climate change and biodiversity are often studied together, chemical pollution as a global change factor contributing to worldwide biodiversity loss has received much less attention in biodiversity research so far. Here, we review evidence showing that the multifaceted effects of anthropogenic chemicals in the environment are posing a growing threat to biodiversity and ecosystems. Therefore, failure to account for pollution effects may significantly undermine the success of biodiversity protection efforts. We argue that progress in understanding and counteracting the negative impact of chemical pollution on biodiversity requires collective efforts of scientists from different disciplines, including but not limited to ecology, ecotoxicology, and environmental chemistry. Importantly, recent developments in these fields have now enabled comprehensive studies that could efficiently address the manifold interactions between chemicals and ecosystems. Based on their experience with intricate studies of biodiversity, ecologists are well equipped to embrace the additional challenge of chemical complexity through interdisciplinary collaborations. This offers a unique opportunity to jointly advance a seminal frontier in pollution ecology and facilitate the development of innovative solutions for environmental protection.

Enhanced Formation of 6PPD-Q during the Aging of Tire Wear Particles in Anaerobic Flooded Soils: The Role of Iron Reduction and Environmentally Persistent Free Radicals

Rapid urbanization drives increased emission of tire wear particles (TWPs) and the contamination of a transformation product derived from tire antioxidant, termed as N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine-quinone (6PPD-Q), with adverse implications for terrestrial ecosystems and human health. However, whether and how 6PPD-Q could be formed during the aging of TWPs in soils remains poorly understood. Here, we examine the accumulation and formation mechanisms of 6PPD-Q during the aging of TWPs in soils. Our results showed that biodegradation predominated the fate of 6PPD-Q in soils, whereas anaerobic flooded conditions were conducive to the 6PPD-Q formation and thus resulted in a ∼3.8-fold higher accumulation of 6PPD-Q in flooded soils than wet soils after aging of 60 days. The 6PPD-Q formation in flooded soils was enhanced by Fe reduction-coupled 6PPD oxidation in the first 30 days, while the transformation of TWP-harbored environmentally persistent free radicals (EPFRs) to superoxide radicals (O2•-) under anaerobic flooded conditions further dominated the formation of 6PPD-Q in the next 30 days. This study provides significant insight into understanding the aging behavior of TWPs and highlights an urgent need to assess the ecological risk of 6PPD-Q in soils.

Impact of microplastics on lead-contaminated riverine sediments: Based on the enzyme activities, DOM fractions, and bacterial community structure

Microplastics (MPs) are able to interact with diverse contaminants in sediments. However, the impacts of MPs on sediment properties and bacterial community structure in heavy metal-contaminated sediments remain unclear. In this study, we investigated the adsorption of Pb(II) by sediment-MPs mixtures and the effects of different concentration MPs on sediment enzyme activities, DOM fractions, and Pb bioavailability in riverine sediments, and further explored the response of sediment microbial community to Pb in the presence of MPs. The results indicated that the addition of MPs significantly decreased the adsorption amount of Pb(II) by sediments, especially decreased by 12.6% at 10% MPs treatment. Besides, the changes in enzyme activities, DOM fractions exhibited dose-dependent effects of MPs. The higher level of MPs (5% and 10%) tends to transform Pb into more bioavailable fractions in sediments. Also, MPs amendment was observed to alter sediment bacterial community structures, and community differences were evident in the uncontaminated and lead-contaminated sediments. Therein, significant increase of Bacteroidota, Proteobacteria and decrease of Firmicutes abundance in Pb-contaminated sediment at the phylum level were observed. These findings are expected to provide comprehensive information for assessing the combined ecological risks of heavy metals and MPs in riverine sediments.

Microplastics stimulated nitrous oxide emissions primarily through denitrification: A meta-analysis

Microplastics can profoundly alter nitrogen cycling. However, it remains poorly understood how microplastics impact soil nitrogen processes and generate N₂O. A meta-analysis was conducted for this investigation based on 60 published studies to elucidate the effects of microplastics on soil nitrogen cycling, from genes to processes. Under microplastic exposure, the emissions of soil N₂O was significantly increased (140.6%), while the nitrate reductase activities increased by 4.8%. The denitrification rate and number of denitrifier genes were increased by 17.8% and 10.6%, respectively. Meanwhile, the nitrification rate and nitrifier genes were not significantly altered, so did the nitrogen immobilization and mineralization rates. The additional emission of soil N₂O might primarily from stimulated denitrification. Soil N₂O emission and denitrification genes were always increased, regardless of the concentrations of microplastic or experiment duration. As a result, the nitrite was increased by 38.8% and nitrate was decreased by 22.4%, respectively. Interestingly, the N₂O emission increments and copy number of denitrifiers genes diminished over time. This study revealed divergent changes in soil nitrogen processes and highlighted N₂O emissions with a greater denitrification rate under microplastic exposure. The negative impacts of microplastics on soil health were revealed from the perspective of soil nitrogen availability and N₂O emissions.

Analysis of microplastics in soils on the high-altitude area of the Tibetan Plateau: Multiple environmental factors

Microplastics (MPs), a class of emerging contaminants, are ubiquitous in the environment, but limited information is known about them in remote terrestrial environment at high-altitude areas with inconvenient traffic and sparsely populated. In this study, 54 soil samples were collected from various land use patterns (greenhouse, ordinary farmland, grassland, and bare land) in western area of the Tibetan Plateau to determine the influence of land use type, altitude, meteorological parameters, and distance from the road edge on MP distribution. The MP abundance ranged from 0 (not detected) to 190 items/kg, with an average number of 64.8 items/kg. The concentration of MPs was slightly negatively correlated with altitude because of less human activities in high-altitude areas (especially agricultural activities). The random forest (RF) models showed that altitude was the most important driving factor that affected the MP distribution. Small-sized MPs were more abundant at higher altitudes than at low ones, and the special natural environment of the high-altitude areas (tall vegetation scarcely, UV, and strong wind speed) may be conducive to the degradation of MPs in surface soils. The special source of MPs in non-agricultural soils was associated with traffic behavior: parking and rest behavior beside roads at high altitude areas, which filled an important source of MPs in the plateau area. This study emphasized the need to investigate the effects of traffic activities on MPs in remote areas at high altitudes.