Co-exposure of maize to polyethylene microplastics and ZnO nanoparticles: Impact on growth, fate, and interaction

Metagenomic analysis reveals soil microbiome responses to microplastics and ZnO nanoparticles in an agricultural soil

Both microplastics (MPs) and engineered nanoparticles are pervasive emerging contaminants that can produce combined toxicity to terrestrial ecosystems, yet their effects on soil microbiomes remain inadequately understood. Here, metagenomic analysis was employed to investigate the impacts of three common MPs [i.e., polyethylene (PE), polystyrene (PS), and polylactic acid (PLA)] and zinc oxide nanoparticles (nZnO) on soil microbiomes. Both MPs and nZnO significantly altered the taxonomic, genetic, and functional diversity of soil microbes, with distinct effects depending on dosage or type. Archaea, fungi, and viruses exhibited more pronounced responses compared to bacteria. Higher doses of MPs and nZnO reduced gene abundance for nutrient cycles like C degradation and N cycling, but enhanced CO2 fixation and S metabolism. nZnO consistently decreased the complexity, connectivity, and modularity of microbial networks; however, these negative effects could be mitigated by co-existing MPs, particularly at elevated doses. Notably, PLA (10 %, w/w) exhibited greater harm to fungal communities and increased negative interactions between microbes and nutrient-cycling genes, posing unique risks compared to PE and PS. These findings demonstrate that MPs and nZnO interact synergistically, complicating ecological predictions and emphasizing the need to consider pollutant interactions in ecological risk assessments, particularly for biodegradable MPs.

Micro/Nanoplastics in plantation agricultural products: behavior process, phytotoxicity under biotic and abiotic stresses, and controlling strategies

With the extensive utilization of plastic products, microplastics/nanoplastics (MPs/NPs) contamination not only poses a global hazard to the environment, but also induces a new threat to the growth development and nutritional quality of plantation agricultural products. This study thoroughly examines the behavior of MPs/NPs, including their sources, entry routes into plants, phytotoxicity under various biotic and abiotic stresses (e.g., salinity, polycyclic aromatic hydrocarbons, heavy metals, antibiotics, plasticizers, nano oxide, naturally occurring organic macromolecular compounds, invasive plants, Botrytis cinerea mycorrhizal fungi.) and controlling strategies. MPs/NPs in agricultural systems mainly originate from mulch, sewage, compost fertilizer, municipal solid waste, pesticide packaging materials, etc. They enter plants through endocytosis, apoplast pathways, crack-entry modes, and leaf stomata, affecting phenotypic, metabolic, enzymatic, and genetic processes such as seed germination, growth metabolism, photosynthesis, oxidative stress and antioxidant defenses, fruit yield and nutrient quality, cytotoxicity and genotoxicity. MPs/NPs can also interact with other environmental stressors, resulting in synergistic, antagonistic, or neutral effects on phytotoxicity. To address these challenges, this review highlights strategies to mitigate MPs/NPs toxicity, including the development of novel green biodegradable plastics, plant extraction and immobilization, exogenous plant growth regulator interventions, porous nanomaterial modulation, biocatalysis and enzymatic degradation. Finally, the study identifies current limitations and future research directions in this critical field.

Environmental concentrations of 6PPD and 6PPD-Q cause oxidative damage and alter metabolism in Eichhornia crassipes

N-(1,3-dimethylbutyl)-N '-phenyl-p-phenylenediamine (6PPD) and N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine-quinone (6PPD-Q) are ubiquitous in the environment and can cause toxicity to aquatic animals. However, research on the toxicological effects of 6PPD and 6PPD-Q on aquatic plants remains limited. The present study investigated the physiological, biochemical, and metabolic responses of the floating aquatic plant Eichhornia crassipes (E. crassipes) to environmentally relevant concentrations (0.1, 1, and 10 μg·L-1) of 6PPD and 6PPD-Q. We found that 6PPD and 6PPD-Q elicited minimal effects on plant growth, but 6PPD induced a concentration-dependent decrease in the content of photosynthetic pigments. Low doses (0.1 μg·L-1 and 1 μg·L-1) of 6PPD-Q significantly elevated Reactive Oxygen Species (ROS) content in E. crassipes roots, indicating oxidative damage. Furthermore, 6PPD-Q induced a more pronounced osmotic stress compared to 6PPD. Metabolic analyses revealed that carbohydrates were significantly altered under 6PPD and 6PPD-Q treatments. The findings of this study enhance the understanding of the environmental risks posed by 6PPD and 6PPD-Q to plants and reveal the potential mechanisms of phytotoxicity.

Environmental efficacy of polyethylene microplastics: Enhancing the solidification of CuO nanoparticles and reducing the physiological toxicity to peanuts

Microplastics and metal-based nanoparticles (NPs) are environmental pollutants that have attracted significant attention. However, there have been relatively few studies on the combined pollution of these substances in the soil-plant system. To investigate the environmental impact and interaction mechanisms of these two pollutants, a pot experiment was conducted to examine the effects of soil exposure on peanut growth. The experiment results revealed that polyethylene (PE) had a minimal effect on peanut growth, while CuO NPs significantly inhibited peanut growth. Peanut biomass decreased by over 50 % in all Cu treatments. The presence of PE significantly impacted the dissolution and absorption of CuO NPs. When 0.5 % PE was present, the dissolution and transformation of CuO NPs were limited, resulting in a total Cu concentration of 458 mg/kg. Conversely, when 5 % PE was present, the dissolution and transformation of CuO NPs were promoted, leading to a DTPA-Cu concentration of 141 mg/kg, the highest level observed. The distribution of trace elements in peanut stems also responded to the differences in Cu concentration. Both pollutants significantly disrupted soil bacteria, with CuO NPs having a more pronounced effect than PE. Throughout the entire growth cycle of peanuts, no chemical adsorption occurred between PE and CuO NPs, and CuO NPs had no significant impact on the aging rate of PE. In summary, this study provides insights into the environmental impact and transport mechanisms of composite pollution involving microplastics and metal-based nanoparticles in the soil-peanut system.

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

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

Effect of microplastics used in agronomic practices on agricultural soil properties and plant functions: Potential contribution to the circular economy of rural areas

The extensive use of plastic materials and their improper disposal results in high amounts of plastic waste in the environment. Aging of plastics leads to their breakdown into smaller particles, such as microplastics (MPs) and nanoplastics. This research investigates plastics used in agricultural practices as they contribute to MP pollution in agricultural soils. The distribution and characteristics of MPs in agricultural soils were evaluated. In addition, the effect of MPs on soil properties, the relationship between MPs and metals in soil, the effect of MPs on the fate of pesticides in agricultural soils and the influence of MPs on plant growth were analysed, discussing legume, cereal and vegetable crops. Finally, a brief description of the main methods of chemical analysis and identification of MPs is presented. This study will contribute to a better understanding of MPs in agricultural soils and their effect on the soil-plant system. The changes induced by MPs in soil parameters can lead to potential benefits as it is possible to increase the availability of micronutrients and reduce plant uptake of toxic elements. Furthermore, although plastic pollution remains an emerging threat to soil ecosystems, their presence may result in benefits to agricultural soils, highlighting the principles of the circular economy.

Enhancing zinc biofortification and mitigating cadmium toxicity in soil-earthworm-spinach systems using different zinc sources

Cadmium (Cd) pollution poses significant threats to soil organisms and human health by contaminating the food chain. This study aimed to assess the impact of various concentrations (50, 250, and 500 mg·kg-1) of zinc oxide nanoparticles (ZnO NPs), bulk ZnO, and ZnSO4 on morphological changes and toxic effects of Cd in the presence of earthworms and spinach. The results showed that Zn application markedly improved spinach growth parameters (such as fresh weight, plant height, root length, and root-specific surface area) and root morphology while significantly reducing Cd concentration and Cd bioconcentration factors (BCF-Cd) in spinach and earthworms, with ZnO NPs exhibiting the most pronounced effects. Earthworm, spinach root, and shoot Cd concentration decreased by 82.3 %, 77.0 %, and 75.6 %, respectively, compared to CK. Sequential-step extraction (BCR) analysis revealed a shift in soil Cd from stable to available forms, consistent with the available Cd (DTPA-Cd) results. All Zn treatments significantly reduced Cd accumulation, alleviated Cd-induced stress, and promoted spinach growth, with ZnO NPs demonstrating the highest Cd reduction and Zn bioaugmentation efficiencies compared to bulk ZnO and ZnSO4 at equivalent concentrations. Therefore, ZnO NPs offer a safer and more effective option for agricultural production and soil heavy metal pollution management than other Zn fertilizers.

Evidence of parental transfer of nanoplastics in pea (Pisum sativum) plants

The increasing abundance of nanoplastics in the environment is a cause of serious concern and its acute and chronic effects on ecosystems need to be thoroughly investigated. Toward this end, this study investigated the parental transfer of nanoplastics by chronically exposing Pisum sativum (pea) plants to nanoplastics through soil medium. We observed the presence of nanoplastics in harvested fruits and a subsequent generation of plants replanted in uncontaminated soil using confocal laser scanning microscopy. The fluorescence was located in the cell wall of the vascular bundles, but not in the epidermis, indicating the parental transfer of nanoplastics. In addition, we determined the effects of nanoplastics on the health of subsequent plant generations by estimating the reproductive factors and measuring the content of individual nutrients in peas. Decreases in crop yield and fruit biomass, in addition to changes in nutrient content and composition, were noted. The transgenerational effects of nanoplastics on plants can profoundly impact terrestrial ecosystems, including both plant species and their predators, raising critical safety concerns. Our findings highlight the evidence of parental transfer of nanoplastics in the soil through plants and shows that the chronic effects of nanoplastics on plants may pose a threat to the food supply.

Effects of polystyrene microplastics on the agronomic traits and rhizosphere soil microbial community of highland barley

This study investigated the influence of polystyrene microplastics (MPs) with two different particle sizes (<1 mm, 1-5 mm) and three concentrations (1 g/m2, 10 g/m2, 50 g/m2), as well as added degrading bacteria, on the agronomic traits of highland barley and the bacterial communities in the rhizosphere soil. Results revealed that the small particle size treatment had a significant effect on reducing the 1000-grain weight of highland barley, while the large particle size treatment had an effect on reducing the spike length, width, and awn length (P < 0.05). Additionally, the MP treatment was found to significantly reduce the rhizosphere soil bacterial diversity and richness, including the Shannon, Chao1, observed species, and dominance indices (P < 0.05). Interestingly, the inoculation treatment also reduced microbial diversity, though the microbial diversity after treatment was similar to that of the control community structure, indicating its regulating effect on the soil microbial community. The abundance of Domibacillus, Pedosphaeraceae, and Enterococcus decreased due to the MP treatment, whereas Achromobacter, Massilia, Ralstonia, and Nitrosospira increased (P < 0.05). Furthermore, functional prediction indicated that MP treatment resulted in the enrichment of microbial functions, such as an AraC-type DNA-binding domain, etc. The microbial communities exposed to different sizes and concentrations of MPs had their own unique functions in response to the effects of the MPs. This study provided novel insights into the effects of different particle sizes and concentrations of MPs on the rhizosphere microbial community and agronomic traits of highland barley. It could be used to improve the understanding of the impact of MPs on the rhizosphere soil microecology and enhance bioremediation of MPs.

Environmental fate, aging, toxicity and potential remediation strategies of microplastics in soil environment: Current progress and future perspectives

Microplastics (MPs) are small plastic debris (<5 mm) that result from the fragmentation of plastic due to physical and physiochemical processes. MPs are emerging pollutants that pose a significant threat to the environment and human health, primarily due to their pervasive presence and potential bioaccumulation within the food web. Despite their importance, there is a lack of comprehensive studies on the fate, toxicity, and aging behavior of MPs. Therefore, this review aims to address this gap by providing a cohesive understanding of several key aspects. Firstly, it summarizes the sources and fate of MPs, highlighting their ubiquitous presence and the potential pathways through which they enter ecosystems. Secondly, it evaluates the aging process of MPs and the factors influencing it, including the morphological and physiological changes observed in crops and the release of pollutants from aged MPs, which can have detrimental effects on the environment and human health. Furthermore, the impacts of aging MPs on various processes are discussed, such as the mobilization of other pollutants in the environment. The influence of aged MPs on the soil environment, particularly their effect on heavy metal adsorption, is examined. Finally, the review explores strategies for the prevention technologies and remediation of MPs, highlighting the importance of developing effective approaches to tackle this issue. Overall, this review aims to contribute to our understanding of MPs, their aging process, and their impacts on the environment and human health. It underscores the urgency of addressing the issue of MPs and promoting research and remediation efforts to mitigate their adverse effects.