Microplastics Treatment Research Articles

Impact and mechanism of polyethylene terephthalate microplastics with different particle sizes on sludge anaerobic digestion.

Municipal wastewater treatment plants (WWTPs) are important sinks for microplastics, and the vast majority of microplastics entering WWTPs are trapped in residual sludge. In order to investigate the effect of microplastics on anaerobic digestion of sludge, polyethylene terephthalate (PET) microplastics with common particle size and physical aging were selected to conduct a comparative study. Regardless of aging, the addition of 300 and 500 μm PET microplastics inhibited methane production, with their cumulative methane production reduced by 11.3-24.9% compared to the control group. In contrast, when 100 μm microplastics were added, the raw PET promoted methane production, yielding 337 L CH4/kg VS, while the aged experimental group showed similar yields to the control group. For the 800 μm microplastics treatment group, aged microplastics facilitated methane production while raw microplastics inhibited it, with methane production of 91.0% and 111% of the control group, respectively. The effects were also investigated by model fitting, stage discussion, and microbial community structure analysis. The results discovered that the main rate-limiting steps of adding microplastics with smaller or larger particle sizes (100, 800 μm) to methane production were solubilization and hydrolysis, while the main rate-limiting step of microplastics with medium particle sizes (300, 500 μm) was methanogenesis. Physically aged PET microplastics with smaller or larger sizes showed a more significant effect on methane production. Furthermore, PET microplastics altered the microbial community structure, shifting methanogens from acetotrophic pathways to hydrotrophic pathways. This study offers new insights into the performance analysis of sludge anaerobic digestion in practical WWTPs.

Analysis and treatment of microplastics in water treatment: research trends, perspectives and implications

Analysis and treatment of microplastics in water treatment: research trends, perspectives and implications

Root traits of soybeans exposed to polyethylene films, polypropylene fragments, and biosolids

Biosolid use imports microplastics into the rhizosphere where they may interfere with root-soil-microbial interactions and cause morphological adaptations in crop root systems. Few studies have examined the response of crop roots to microplastics at documented soil concentrations, and many studies collect root traits using destructive techniques. Hence, there is little information on when and how microplastics effect the physical structure of root systems. Using the rhizobox method, soybeans (Glycine max) were grown in soil amended with biosolid microplastic mimics (polyethylene film or polypropylene fragments at 2,000 and 15,000 particles/kg dry soil) or biosolids and imaged weekly until maturity (11 weeks) using a custom scanner system. Plant biomass increased in the polyethylene treatments and decreased in the high concentration polypropylene treatment. Relative to the Control, polyethylene treatments had larger root length, reduced root diameters, reached maturity faster, had deeper root systems, and had a greater number of lateral roots. In contrast, polypropylene treatments had a mixed response, with high concentrations eliciting a lower root length, fewer laterals, and a more vertical root orientation. Segmented linear regression revealed that root growth in the Control and Biosolid treatments continued through the course of the experiment, while the microplastic treatments reached maturity up to two weeks earlier. Imagery revealed that microplastics elicited deeper rooting depth within the first week and differences in all root traits were evident by the development of the first trifoliate leaflets. Microplastic effects on root traits at early life stages suggest soil physiological drivers, while increased branching frequency and lower lateral elongation are suggestive of changes in soil nitrogen availability. The minimal difference in root traits in the biosolid treatment may be attributable to differences in microplastic properties or counteractive effects by other biosolid constituents.

Elimination of microplastic from soil by pyrolysis and potential hazard analysis: Effects of pyrolysis temperature and holding time

AbstractEfficient and harmless treatment of microplastics in soil is the current focus of microplastic pollution management. In this study, the pyrolysis effect of soil microplastics at different temperatures and holding times was analyzed. The results showed that temperature and holding time significantly affected the morphology and compositional structure of soil. Pure microplastics and product adhesion after pyrolysis at low temperature (400°C) were not easy to remove. Interestingly, compared with pure polyethylene (PE), direct pyrolysis of microplastics in soil could obtain better results, and the content of organic matter and polycyclic aromatic hydrocarbons (PAH) could be significantly reduced. However, the pyrolysis performance was very unsatisfactory even if the action time was prolonged at 400°C. Prolonged high‐temperature treatment accelerated the fragmentation of the alkane main chain of PE, thus generating more PAH, and the temperature was not high enough (400°C) for further effective degradation of PAH into carbon dioxide and water. Therefore, higher temperature and longer holding time need to be selected to ensure the pyrolysis performance. This study revealed the role and mechanism of pyrolysis in soil microplastic mixed systems, aiming to provide a basis for the treatment of microplastics in terrestrial ecosystems.

Impact of Microplastics on the Carbon and Nitrogen of Vermicompost

ABSTRACTThe impact of microplastics (MPs) on carbon (C) and nitrogen (N) content in vermicompost is not yet fully understood. This study aims to evaluate the effect of MPs on the carbon and nitrogen ratio in vermicompost, which is important for soil quality and health. The study was carried out using a control treatment and six variations of MPs in the vermicomposting process. Observations were carried out at certain time intervals for 60 days with routine measurements of pH, electrical conductivity (EC), seed germination index (GI), survival rate (SR), and C/N ratio. The results showed that all types of MPs caused a decrease in the C/N ratio compared to the control, with the high‐density polyethylene (HDPE) MPs treatment showing the most significant decrease (from 21 to 9.42). Observations also showed that MPs had an impact on reducing the SR parameters (6.88%–20.41%), pH (6.8–6.1), and EC (525.3–398 µs/cm) in vermicompost, which had an impact on the final product quality thereby reducing the GI (10%–28%). MPs have a significant effect on the C/N ratio in vermicompost, reducing the quality of the compost. This study provides new insights into how MPs can affect the composting process and the quality of the final product, important for sustainable agricultural practices and waste management.

Silicon alleviates the toxicity of microplastics on kale by regulating hormones, phytochemicals, ascorbate-glutathione cycling, and photosynthesis

Kale is rich in various essential trace elements and phytochemicals, including glucosinolate and its hydrolyzed product isothiocyanate, which have significant anticancer properties. Nowadays, new types of pollutant microplastics (MP) pose a threat to global ecosystems due to their high bioaccumulation and persistent degradation. Silicon (Si) is commonly used to alleviate abiotic stresses, offering a promising approach to ensure safe food production. However, the mechanisms through which Si mitigates MP toxicity are unknown. In this study, a pot culture experiments was conducted to evaluate the morphogenetic, physiological, and biochemical responses of kale to Si supply under MP stress. The results showed that MP caused the production of reactive oxygen species, inhibited the growth and development of kale, and reduced the content of phytochemicals by interfering with the photosynthetic system, antioxidant defense system, and endogenous hormone regulation network. Si mitigated the adverse effects of MP by enhancing the photosynthetic capacity of kale, regulating the distribution of substances between primary and secondary metabolism, and strengthening the ascorbate-glutathione (AsA-GSH) cycling system. SummaryEffects of microplastic and silicon on key indicators of kale. Note: The red arrows and blue arrows indicate the MP treatment effect compared to the control and Si treatment effect compared to the MP treatment, respectively.

Microplastics caused embryonic growth retardation and placental dysfunction in pregnant mice by activating GRP78/IRE1α/JNK axis induced apoptosis and endoplasmic reticulum stress

Microplastics (MPs), a brand-new class of worldwide environmental pollutant, have received a lot of attention. MPs are consumed by both humans and animals through water, food chain and other ways, which may cause potential health risks. However, the effects of MPs on embryonic development, especially placental function, and its related mechanisms still need to be further studied. We investigated the impact on fetal development and placental physiological function of pregnant mice by consecutive gavages of MPs at 0, 25, 50, 100 mg/kg body weight during gestational days (GDs 0–14). The results showed that continuous exposure to high concentrations of MP significantly reduced daily weight gain and impaired reproductive performance of pregnant mice. In addition, MPs could significantly induce oxidative stress and placental dysfunction in pregnant mice. On the other hand, MPs exposure significantly decreased placental barrier function and induced placental inflammation. Specifically, MPs treatment significantly reduced the expression of tight junction proteins in placentas, accompanied by inflammatory cell infiltration and increased mRNA levels of pro-inflammatory cytokines and chemokines in placentas. Finally, we found that MPs induced placental apoptosis and endoplasmic reticulum (ER) stress through the GRP78/IRE1α/JNK axis, leading to placental dysfunction and decreased reproductive performance in pregnant mice. We revealed for the first time that the effects of MPs on placental dysfunction in pregnant animals. Blocking the targets of MPs mediated ER stress will provide potential therapeutic ideas for the toxic effects of MPs on maternal pregnancy.

Long-term exposure to polystyrene microplastics reduces macrophages and affects the microbiota–gut–brain axis in mice

The remarkably increase in plastic use has led to worldwide pollution involving microplastics (MPs), which have been shown to be potentially hazardous substances. Although several studies have focused on the effects of small MPs on the brain and behavior of aquatic species, their effects on the mouse brain and the underlying mechanisms remain unclear. Our study’s aim was to investigate the effects of long-term oral ingestion of different sizes of MPs (0.1, 5, and 50 μm) on mouse colon tissue. Of these sizes, the smallest (0.1 μm) had the greatest effect. Pre-administration of MP promotes colitis but reduces tumor growth in a colitis-associated colorectal cancer (CAC) mouse mode. MPs can increase inflammation in mice via activation of the very late antigen 4–vascular cell adhesion molecule 1 (VLA4-VCAM1) signaling pathway in macrophages, while also inducing macrophage reduction in the late phase of inflammation. In the microbiota–gut–brain axis, polystyrene MP treatment altered bile acid and carbohydrate metabolism in the intestine, inhibited intestinal motility, reduced water reabsorption, and led to a certain degree of depression in mice. These findings suggest that small MPs can induce macrophage reduction, thereby affecting the physical and mental health by modulating the microbiota–gut–brain axis.

The impacts of microplastics on zebrafish behavior depend on initial personality state

Microplastic pollution is associated with inflammation, gut dysbiosis and behavioral changes in fish. Fish have distinct personality traits but the role of personality in behavioral toxicology is rarely considered. We classified zebrafish on four behavioral axes: boldness, anxiety, sociability and exploration tendency then exposed them to low- or high- concentrations of two types of polyethylene microplastics (low- and high-density) for 28 days. Behaviors, antioxidant enzymes (catalase and superoxide dismutase), and gut microbiome were then measured. There were direct effects of microplastics on boldness, anxiety and sociability. However, fish retained their initial behavioral tendencies. Exposure to all microplastic treatments reduced average swimming speed and decreased the time spent motionless. Microplastic exposure did not affect antioxidant enzymes but did cause significant changes in the composition of the gut microbiome. This study demonstrates that environmentally realistic concentrations of microplastics can alter fish behavior, but much of the variance in response can be explained by personality.

Addition of polyester microplastic fibers to soil alters the diversity and abundance of arbuscular mycorrhizal fungi and affects plant growth and nutrition

Microplastics (MPs) represent an emerging factor in global environmental change and are increasingly found in soils. However, the extent to which they affect plants and their interactions with the soil microbiome is poorly understood. Here, we test the hypothesis that increasing levels of polyester MP fibers in soil alter plant growth and nutrient acquisition responses to arbuscular mycorrhizal (AM) fungi via changes in AM fungal colonization and community composition. We used Sorghum drummondii as a model species in a fully factorial greenhouse experiment. Plants were exposed to soil treatments with 0, 0.2, 1, and 3 % MP polyester fibers either in the presence or absence of an assembled AM fungal community comprising 13 species across three families with contrasting life-history strategies. We found that the 1 % MP treatment promoted plant biomass irrespective of the presence of AM fungi. While no changes in macronutrient concentrations in plant tissues were seen, there was a significant increase in B and Mn when relatively low amounts of MPs were added, and this effect was modulated by AM fungi. Furthermore, there were shifts in AM fungal community composition in response to MP, favoring taxa such as Gigaspora sp. while negatively affecting ruderal taxa like Glomus sp. Overall, our data indicate that MP polyester fibers present in soil can in some cases be beneficial to plants and AM fungal interactions. However, the implications of these findings over the long-term and in the context of ecological repercussions of MP pollution in the environment remain to be seen.

Migration of Microplastics in the Rice–Duckweed System under Different Irrigation Modes

Microplastic (MP) pollution in agriculture is garnering growing concern due to its potential detrimental impact on soil properties and crop growth, particularly affecting staple food crops such as rice. Irrigation plays a crucial role in the migration of MPs. However, limited research has focused on how different irrigation modes affect the migration of MPs in paddy fields. To simulate real-world conditions, in this experiment, two different irrigation modes were set: shallow–frequent irrigation (FWI, I0) and controlled irrigation (CI, I1). The experiment also included treatments with and without duckweed (D0 and D1, respectively), as well as treatments with and without MPs (M0 and M1). This resulted in a total of eight treatments: I0M0D0, I0M0D1, I1M0D0, I1M0D1, I0M1D0, I0M1D1, I1M1D0, and I1M1D1. Our findings indicated that compared to CI, FWI significantly increased the MP concentration in the leakage but reduced the numbers of MPs in the first soil layer and adhered by duckweed. Notably, dry–wet cycles under CI induced soil cracking, and the MP concentrations in cracked areas were significantly higher than those of crack-free soil. Moreover, compared with the MP-free treatment, MP treatments significantly influenced rice root growth, such as enhancing the average root diameter by 13.44%, root volume by 46.87%, root surface area by 30.81%, and biomass aboveground by 26.13%, respectively. The abundance of some microorganisms was also significantly influenced by the relative mobility (RM) of MPs. Furthermore, the root length was positively correlated with Planctomycetota. Meanwhile, Actinobacteriota was negatively correlated with the root surface area, root volume, and branch number, and Bacteroidota was negatively correlated with the number of root tips. However, further research is needed to elucidate how MPs influence microorganisms and, in turn, affect rice root growth.

Enhanced sorption of hyper-cross-linked polymers for enrofloxacin via polystyrene adhesion: Exploring the feasibility of a collaborative treatment approach for emerging contaminants

The conventional treatment processes adopted by wastewater treatment plants (WWTPs) are unable to completely remove antibiotics and microplastics (MPs), resulting in the discharge of residual antibiotics and MPs into the environment, which poses threats to both ecological and human health. Therefore, targeted removal of residual antibiotics and MPs in effluent from WWTPs is crucial. Moreover, the presence of MPs in the wastewater system is likely to affect the removal of antibiotics. Here, the impact of polystyrene (PS) on the sorption characteristics and mechanisms of enrofloxacin (ENR) by hyper-cross-linked polymers (HCPs) was studied. The possibility of collaborative treatment of antibiotics and MPs was also discussed. The results showed that PS could affect the sorption of ENR by interacting with HCPs. The addition of PS increased dispersibility of HCPs and the number of sorption sites, thereby enhancing the sorption of ENR. However, as the concentration of PS increased, the repulsive energy between HCPs and PS decreased from 600 to 280 kT, leading to further heterogeneous aggregation between HCPs and PS. It prevented some of the sorption sites from being exposed to ENR, thereby reducing the promotion effect from 57% to 13%. Additionally, PS facilitated the sorption of ENR through promoting electrostatic attraction, π−π, and n−π interactions. The presence of PS also enhanced the removal of ENR in actual water samples with the efficiency of 98.2%. While removing antibiotics, MPs can also be separated from sewage by forming aggregates with HCPs. This study contributes to a deeper understanding of the role of MPs in the treatment of antibiotics within wastewater systems and offers new insights for the collaborative treatment of emerging contaminants in wastewater systems.

Characteristics of biofilms on polylactic acid microplastics and their inhibitory effects on the growth of rice seedlings: A comparative study of petroleum-based microplastics

Increasing evidence highlights the negative effects of microplastics (MPs) on crops and bio-based plastics offer an alternative to conventional plastics. However, there is limited knowledge on the impacts and mechanisms of bio-based MPs on crop physiology. In this study, bio-based polylactic acid (PLA) and petroleum-based MPs [polyamide (PA) and polypropylene (PP)] were added to hydroponic cultures planted with rice (Oryza sativa L.) seedlings to assess their toxicity. Compared to PA and PP MPs, PLA MPs experienced greater aging after 28 days of exposure, and their surfaces were loaded with more rod-shaped microorganisms with potential plastic degradation ability, such as Proteobacteria and Bacteroidota, which competed with rice seedlings for carbon and nitrogen sources for self-multiplication, thus altering the carbon fixation and nitrogen cycling processes during rice seedling growth. Down-regulation of amino acid and lipid metabolisms in the PLA treatment inhibited the normal synthesis of chlorophyll in rice seedling leaves. Consequently, decreases in the biomass and height of rice seedling roots and shoots were observed in the PLA MP treatment. This study provides evidence that bio-based MPs may have a more severe impact on crop growth than petroleum-based MPs.

Molecular simulation of the slurrying mechanism in microplastic semi-coke water slurry.

This study explores the interaction between particles in microplastic semi-coke water slurry at the molecular level using molecular simulation methods, specifically DFT calculations and MD simulations. In addition, the experiment of slurry preparation was carried out to study the viscosity and stability of the slurry. The electrostatic potential analysis shows that the interaction between microplastics and dispersant molecules occurs on atoms with large electronegativity or oxygen-containing functional groups, and the energy gap of frontier molecular orbitals indicated that PVC interacts most easily with the dispersant (0.39eV), followed by PS (1.08eV) and PET (3.65eV). In addition, it is also noted that due to the steric hindrance effect, the adsorption energy was opposite to the DFT calculation results: PET was - 213.338kcal/mol (NNO) which was highest, followed by PS (- 107.603kcal/mol, NNO), and PVC (NNO) was lowest which was - 94.808kcal/mol. And RDF shows similar results, which the probability of water molecules in the PET system was the highest, followed by PS, and finally, PVC. The MD results are consistent with the viscosity and stability characterization results of the slurry which PET has the lowest viscosity of 87.3mPa·s. Finally, this study provides new ideas for the treatment of microplastics and the improvement of the performance of semi-coke water slurry and reveals the interaction mechanism between microplastics and semi-coke water slurry. All calculations were performed using Materials Studio (MS) version 2020 software, BIOVIA Corporation. The DFT calculation was carried out through the DMol3 module. The DFT calculations include electron density, electrostatics, orbitals, and population analysis. In DMol3 module, the GGA-PBE function was selected to consider gradient changes in density in the simulated calculation. The DFT-D correction was selected, and all electrons were calculated by DNP for accurate core potentials and the DNP file was 4.4. MD simulation was performed through the Forcite module. MD simulation mainly focuses on relative concentration distribution analysis, radial distribution function, and adsorption energy calculation. All molecular geometry optimizations are performed in the Forcite module. In the molecular dynamic part, all simulations used PCFF forcefield. The NVT ensemble was adopted and using the Nosé thermostat.

Metabolic responses of the marine mussel Mytilus galloprovincialis after exposure to microplastics of different shapes and sizes

Microplastics (MP) are ubiquitous pollutants with diverse shapes, sizes, and characteristics that pose critical risks to marine organisms and the environment. In this study, we used the Mediterranean mussel Mytilus galloprovincialis as a marine benthic organism model to investigate the metabolic consequences of exposure to different polyethylene terephthalate MP sizes and shapes: round (27–32 μm), small fibers (200–400 μm), large fibers (3000 μm), small fragments (20 μm), medium fragments (45–75 μm), and large fragments (>150 μm). After exposure to high concentrations (100 mg L−1) of MP for 14 days, round and small fiber-type MP were highly accumulated in mussels. Metabolomic analysis revealed that exposure to round and small fiber-type MP induced significant changes in 150 metabolites. Partial least squares-discriminate analysis (PLS-DA) showed that the round and small fiber MP treatment groups displayed similar cluster patterns that differed from those of the control group. In addition, only 22 annotated metabolites related to histidine, valine, leucine, and isoleucine degradation/biosynthesis and vitamin B6 and aminoacyl-tRNA biosynthesis were significantly affected by round or small fiber-type MP. Among the histidine metabolites, round and small fiber-type MP upregulated the levels of L-histidine, L-glutamate, carnosine, imidazole-4-acetaldehyde, 4-imidazolone-5-propanoate, and methylimidazole acetaldehyde and downregulated methylimidazole acetic acid and N-formimino-L-glutamate. These results suggest novel insights into the potential pathways through which MP of specific sizes and shapes affect metabolic processes in mussels.

Microplastic exposure inhibits nitrate uptake and assimilation in wheat plants

Microplastic (MP) contamination in soil severely impairs plant growth. However, mechanisms underlying the effects of MPs on plant nutrient uptake remain largely unknown. In this study, we revealed that NO3− content was significantly decreased in shoots and roots of wheat plants exposed to high concentrations (50–100 mg L−1) of MPs (1 μm and 0.1 μm; type: polystyrene) in the hydroponic solution. Isotope labeling experiments demonstrated that MP exposure led to a significant inhibition of NO3− uptake in wheat roots. Further analysis indicated that the presence of MPs markedly inhibited root growth and caused oxidative damage to the roots. Additionally, superoxide dismutase and peroxidase activities in wheat roots decreased under all MP treatments, whereas catalase and ascorbate peroxidase activities significantly increased under the 100 mg L−1 MP treatment. The transcription levels of most nitrate transporters (NRTs) in roots were significantly downregulated by MP exposure. Furthermore, exposure to MPs distinctly suppressed the activity of nitrate reductase (NR) and nitrite reductase (NiR), as well as the expression levels of their coding genes in wheat shoots. These findings indicate that a decline in root uptake area and root vitality, as well as in the expression of NRTs, NR, and NiR genes caused by MP exposure may have adverse effects on NO3− uptake and assimilation, consequently impairing normal growth of plants.

Microplastics in heavy metal-contaminated soil drives bacterial community and metabolic changes

Microplastic (MP) and heavy metal pollution in soil are global issues. When MPs invade the soil, they combine with heavy metals and adversely affect soil organisms. Six common MPs—polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyethylene terephthalate, and polytetrafluoroethylene—were selected for this study to examine the effects of various concentrations and MP types on the physicochemical properties, bacterial community, and soil metabolism of heavy metal-contaminated soil. MP enhanced predation and competition among heavy metal-contaminated soil bacteria. Heavy metal-MPs alter metabolites in lipid metabolism, other pathways, and the bacterial community. MP treatment promotes energy production and oxidative stress of soil bacteria to resist the toxicity of heavy metals and degrade MP pollution. In conclusion, MP treatment changed the metabolism of the microbiome in heavy metal-contaminated soil and increased the abundance of Proteobacteria that responded to MPs and heavy metal pollution by 11.54 % on average. This study explored bacteria for the ecological regeneration and provided ideas for MPs and heavy metal-contaminated soil remediation.

The significant impact of MPs in the industrial/municipal effluents on the MPs abundance in the Nakdong River, South Korea

Owing to extensive plastic consumption, wastewater from households, business establishments, and industrial activities have been recognised as a significant contributor to microplastics (MPs) in aquatic environments. This case study represents the first investigation of MPs in the Nakdong River, Republic of Korea, that traverses through the largest industrial complex midstream and densely populated cities of Daegu and Busan downstream before flowing into the sea. Monitoring of MP abundance in effluents discharged from three municipal, two industrial, and one livestock wastewater treatment plant (WWTP) into the Nakdong River was conducted over four seasons from August 2022 to April 2023. Identification and quantification of MPs were performed using micro-Fourier transform infrared spectrometry. Seasonal variation in MPs in the Nakdong River was found to be strongly influenced by the nearest upstream WWTPs and rivers, exhibiting a linear relationship that decreased gradually with increasing distance from the WWTPs. The average concentrations of MPs in the six effluent sources ranged from 101 ± 13 to 490 ± 240 particles/L during the yearly monitoring period, while MP concentrations in the river ranged between 79 ± 25 and 120 ± 43 particles/L. Industrial effluents contained higher amounts of discharged MPs (314 ± 78 particles/L) than municipal sources (201 ± 61 particles/L). Notably, two municipal WWTPs, located in the highly densely populated city, discharged the highest total MP amounts per day and released the greatest volumes of effluents. This study provides valuable insights into the monitoring and impact of effluents on MPs in rivers, which could inform MP treatment and management strategies for in river and marine environments.

Nano- and Microplastics Increase the Occurrence of Bacterial Wilt in Tomato (Solanum lycopersicum L.).

Concern over nano- and microplastic contamination of terrestrial ecosystems has been increasing. However, little is known about the effect of nano- and microplastics on the response of terrestrial ecosystems already under biotic stress. Here, nano- and microplastics at 150-500 mg·kg-1 were exposed to tomatoes (Solanum lycopersicum L.), and the results demonstrate that the presence of nano- and microplastics increased the occurrence of bacterial wilt caused by Ralstonia solanacearum in tomatoes as a function of contaminant concentration, surface modification, and size. Our work shows that nanoplastics (30 nm, 250 mg·kg-1) increased the disease incidence by 2.19-fold. The disease severities in amino- and carboxyl-modified nanoplastic treatments were 30.4 and 21.7% higher than that in unmodified nanoplastic treatment, respectively. The severity of disease under the influence of different-sized nano- and microplastic treatments followed the order 30 > 100 nm > 1 > 50 μm. Mechanistically, nanoplastics disrupted the structure of the tomato rhizosphere soil bacterial community and suppressed the induced systemic resistance in tomato; nanoplastics in planta decreased the salicylic acid and jasmonic acid content in tomatoes, thus inhibiting systemic acquired resistance; and microplastics increased the soil water retention, leading to increased pathogen abundance in the rhizosphere. Additionally, the leachates from nano- and microplastics had no effect on disease occurrence or the growth of tomatoes. Our findings highlight a potential risk of nano- and microplastic contamination to agriculture sustainability and food security.

Exploring the potential of biochar for the remediation of microbial communities and element cycling in microplastic-contaminated soil

The detrimental effects of microplastics (MPs) on soil microbial and elemental raise significant environmental concerns. The potential of remediation with biochar to mitigate these negative impacts remains an open question. The remediation effects of biochar derived from corn and cotton straw on MPs concerning soil microorganisms and element cycling were investigated. Specifically, biochar induced substantial remediations in microbial community structure following MP exposure, restoring and fortifying the symbiotic network while exerting dominance over microbial community changes. A combined treatment of biochar and MPs exhibited a noteworthy increase in the abundance of NH4+, NO3−, and available phosphorous by 0.46–2.1 times, reversing the declining trend of dissolved organic carbon, showing a remarkable increase by 0.36 times. This combined treatment also led to a reduction in the abundance of the nitrogen fixation gene nifH by 0.46 times, while significantly increasing the expression of nitrification genes (amoA and amoB) and denitrification genes (nirS and nirK) by 22.5 times and 1.7 times, respectively. Additionally, the carbon cycle cbbLG gene showed a 2.3-fold increase, and the phosphorus cycle gene phoD increased by 0.1-fold. The mixed treatment enriched element-cycling microorganisms by 4.8–9.6 times. In summary, the addition of biochar repaired the negative effects of MPs in terms of microbial community dynamics, element content, gene expression, and functional microbiota. These findings underscore the crucial role of biochar in alleviating the adverse effects of MPs on microbial communities and elemental cycling, providing valuable insights into sustainable environmental remediation strategies.