Effects of Microplastics in Soil Ecosystems: Above and Below Ground

Microplastics removal from stormwater runoff by bioretention cells: A review

Microplastics (MPs), as a new category of environmental pollutant, have been the hotspot of eco-friendly issues nowadays. Studies based on the aging process, the migration pattern of MPs in runoff rainwater, and the use of bioretention cells to remove MPs from runoff rainwater are beginning to attract widespread attention. This review analyses the migration patterns of MPs in rainwater runoff through their sources, structure and characteristics. The mechanism of removing MPs from runoff stormwater, the purification efficiency of different fillers and their influencing factors, and the accumulation, fate, and aging of MPs in bioretention cells are described. Furthermore, the hazards of MP accumulation on the performance of bioretention cells are summarised. Future directions for removing MPs in bioretention cells are proposed: (1) research on MPs smaller than 100 µm; (2) influence of MPs aging process on bioretention cells; (3) exploration of more effective fillers to enhance their removal efficiency; (4) research on synergistic removal mechanism of MPs and other pollution.

Impacts of different plastic residues on soil volatile profiles associated with microbiome dynamics

Plastic pollution poses a significant threat to soil ecosystems, yet the role of volatile organic compounds (VOCs) in plastic degradation is not well-studied. The present research focuses on the impact of polyethylene (PE), polylactic acid (PLA), and poly(butylene-adipate-co-terephthalate) (PBAT) residues on soil in a 12-week long lab-scale aerobic experiment. The study focused on the dynamics of VOC profiles, soil physicochemical properties, and microbial communities. PBAT, known for its biodegradability, produced a distinct VOC profile with hazardous compounds such as 1,3-butadiene, which is consistently associated with cardiovascular diseases and leukemia. Microbial analysis of PBAT revealed distinct bacterial and fungal diversity responses, along with unique KEGG pathway profiles compared to PE and PLA, suggesting its biodegradation process may involve biofilm formation and quorum sensing. Correlation analysis based on the relevant abundance of specific microbes exhibited strong positive correlations, such as Streptomyces with propyne emission and Hydrogenispora with ethylene emission. These results demonstrated distinct biodegradation patterns of various plastics in soil, identified through the combination of VOC detection and microbiome analysis.

Mechanism of nanoplastics altering soil carbon turnover under freeze-thaw cycle

Nanoplastics (NPs) affect soil carbon (C) turnover, but their influence on this process through modifications in soil aggregate stability under freeze-thaw cycles remains unclear. In this study rare earth oxides (REOs) and C isotope (13C) labeling, combined with Soil Microstructure Scanning Computed Tomography (SMS-CT) and data modeling, were used to examine the relationship between soil aggregate turnover and C turnover under NPs. Compared with the control group, the total phase porosity and surface area of soil treated with NPs increased by 11.9 % and 30.9 %, respectively under freeze-thaw cycle. NPs exhibited a positive effect on the stability of soil aggregates, and the change in soil aggregate stability were attributed to shifts in aggregate composition. During the freeze-thaw cycle, the distribution of 13C in 0.5-1 mm aggregates decreased by 41.9 % compared with the control group, while it increased by 60.8 % in < 0.25 mm aggregates, indicating NPs redirected C toward microaggregates. Freeze-thaw cycles improved the connection between soil aggregates and C turnover, whereas NPs increased resistance of aggregate to freeze-thaw forces. This study provides new insights into the environmental effects of NPs on soil ecosystems and food security.

Microplastic-induced alterations in growth and microecology of mulberry seedlings: Implications for sustainable forest-soil systems

This study investigated the ecotoxicological effects of polyethylene (PE) and polylactic acid (PLA) microplastics (MPs) on mulberry growth and soil-microbe interactions through controlled pot experiments (0.1 % and 1 % concentrations). PE exposure significantly increased mulberry height by 16 % (0.1 %) and 18 % (1 %) (p < 0.05), whereas PLA reduced total biomass by 12 % (0.1 %) and 66 % (1 %), highlighting polymer- and concentration-dependent responses. MPs differentially modulated soil biogeochemistry: PE decreased nitrate and ammonium nitrogen levels while enhancing nitrogen fixation (nifH) (from 0.9 × 107 to 6.1 × 107 copies/g) and denitrification (nirK) (from 1.0 × 108 to 1.9 × 108 copies/g) gene expression via Acidobacteriota enrichment, which was correlated with increased soil organic matter mobilisation and photosynthetic rates. PLA disrupted phosphorus cycling and destabilised structure of fungal communities critical for nutrient assimilation. Structural equation modelling identified direct microplastic-soil-plant linkages, with real-time polymerase chain reaction validating PE-driven suppression of nitrogen loss through microbial functional shifts. These findings illuminate the dual roles of microplastics as ecological stressors and modifiers, providing actionable insights for balancing agricultural productivity and soil health in MP-contaminated forest ecosystems.

Machine learning-driven analysis of soil microplastic distribution in the Bang Pakong Watershed, Thailand

Microplastics (MPs) have emerged as a pervasive environmental pollutant due to their persistence and global distribution. However, MPs relationships with covariables remain largely unexplored. This study investigates factors influencing MPs occurrence and distribution in the Bang Pakong Watershed, using 40 soil samples across various land-use types and assess machine learning for their spatial distribution. Samples were sorted into three sizes: 1.2 μm-500 μm, 500 μm-1 mm, and 1-2 mm and analyzed using zinc chloride (ZnCl2) density separation, hydrogen peroxide (H2O2) digestion, and Fourier transform infrared spectroscopy (FTIR) for polymer identification. Results reveal a significant MPs presence, averaging 1121 ± 2465.6 items/kg dry soil, with particles <0.5 mm (49 %), fragments (74.2 %), transparent (49 %), and polypropylene (PP) (52 %) predominating. Urban soils contained highest concentrations (67.6 %) at 2331 ± 4114 items/kg, followed by irrigation (555 ± 571), agricultural (552 ± 432), and forest soils (417 ± 365). Predictive modeling incorporated 14 variables, including soil properties and environmental factors. The Random Forest model (RF), optimized for complex non-linear relationships and high data variability, shows higher predictive accuracy (R2 = 0.82), with silt content and distance-to-river as key variables. Spatial distribution analysis, developed on model predictions and inverse distance weighting (IDW), demonstrates a concentration gradient increasing southwestward toward the Bang Pakong River. Flood susceptibility and drainage density analysis correlate with interpolation results, suggesting that these factors influence MPs transport and deposition processes. These results refine MPs management, emphasizing urbanization and hydrological factors as drivers for distribution, necessitating targeted mitigation in high-risk areas.

Potential impacts of polyethylene microplastics and heavy metals on Bidens pilosa L. growth: Shifts in root-associated endophyte microbial communities

This study investigates the impact of polyethylene (PE) microplastics of varying particle sizes and concentrations on the growth of Bidens pilosa L. and its root-associated microbial communities in cadmium (Cd) and lead (Pb) co-contaminated soil. PE microplastics had a significant impact on plant growth. Notably, at the P05-10 level, root length, root weight, and total biomass exhibited the greatest reductions by 48.9 %, 44.1 %, and 45.2 %, respectively. Furthermore, PE microplastics reduced photosynthetic pigment levels and promoted the accumulation of reactive oxygen species, as indicated by a 264.8 % and 57.2 % increase in H2O2 content in roots and leaves. High-throughput sequencing revealed substantial alterations in the composition of bacterial and fungal communities, with stress-resilient taxa such as Actinobacteria, Verrucomicrobiota, and Rhizophagus exhibiting increased relative abundance. Correlation analyses indicated that variations in soil pH and enzymatic activity influenced microbial community structure, which in turn affected plant physiological responses. Functional predictions using PICRUSt2 and BugBase suggested enhanced oxidative stress tolerance, increased secondary metabolite biosynthesis, and a higher prevalence of stress-resistant phenotypes under conditions of elevated PE concentrations and smaller particle sizes. Overall, this study provides novel insights into the potential effects of microplastics on Bidens pilosa L., particularly in its role as a hyperaccumulator, highlighting its capacity for heavy metal uptake under microplastic exposure.

Environmental factors influence airborne microplastic deposition in the soil of urban allotment gardens

The widespread contamination of urban soils by airborne microplastics (MPs) is an emerging environmental concern, particularly in urban allotment gardens (UAGs) where food production occurs. This study investigates the vertical distribution of MPs in three UAGs in Berlin, Germany, over 90 days. Soil samples were collected at three depths (surface, 1-15 cm, and 15-30 cm) and analysed for MPs composition and concentration, with a detection limit of 0.1 μm using Optical PhotoThermal InfraRed (O-PTIR) spectroscopy. Results revealed that fibres were the dominant MP type, with the highest concentrations found in surface layers. MPs concentrations decreased with soil depth, and fibres showed limited vertical penetration. We also identified 19 different polymer types, with polyethylene terephthalate (PET), polyester (PES), and polyethylene (PE) being the most common. Temporal variations in MPs deposition were observed, with a significant peak at 90 days. Environmental factors, including PM2.5 concentration, precipitation, and wind velocity, played a role in MPs deposition. Precipitation and PM2.5 were positively associated with increased deposition, while higher wind speeds reduced MPs accumulation. These findings highlight the pervasive presence of MPs in urban soils and suggest that environmental conditions significantly influence MPs distribution. Understanding these dynamics is essential for assessing the long-term ecological impacts of MPs on soil health in urban environments.

Decreased particle size enhances the aging behavior of microplastics during sewage sludge composting: Physicochemical properties and cadmium loading

Although aerobic composting is capable of aging microplastics (MPs), the influence of size on MPs aging during composting and loading of cadmium (Cd) remains unclear. Therefore, we investigated variations in the physicochemical properties of polyethylene terephthalate microplastics (PET-MPs) with different sizes (1.0 -5.0, 0.2 -1.0, and 0.05 -0.2 mm) during composting and the concentration of Cd accumulated on the surface of different-sized aged PET-MPs. The results indicated that PET-MPs exhibited size-dependent as they aged during composting, with smaller sizes aging faster. After composting, the 0.05 -0.2 mm PET-MPs had the greatest increase in specific surface area (205.5 %), compared with the 1.0 -5.0 mm (18.7 %) and 0.2 -1.0 mm (95.6 %) PET-MPs. The greatest increase in the carbonyl index/oxygen-to-carbon atom ratio was also observed for the 0.05 -0.2 mm PET-MPs, which were 2.25 / 3.27 and 0.02 / 2.11 times higher than those of the 1.0 -5.0 mm and 0.2-1.0 mm PET-MPs, respectively. Similarly, size-dependent accumulation of Cd on the aged PET-MPs was also observed: 0.05-0.2 mm (5.37 mg/kg Cd) > 0.2 -1.0 mm (2.90 mg/kg Cd) > 1.0-5.0 mm (0.78 mg/kg Cd). These findings demonstrate that the aging behavior of polymer is closely related to their size, emphasizing the role of size in the fate and pollutant loading of polymer.

Occurrence and environmental consequences of microplastics and nanoplastics from agricultural reuse of wastewater and biosolids in the soil ecosystem: A review

The contamination of soil and groundwater ecosystems by plastic particles (micro- and nanoplastics) was discussed, focusing on wastewater and biosolids recycled into agricultural soils. The impact of these contaminants was critically examined. Livestock (average: 18; min.: 8 - max.: 42 MP/L) and municipal (average: 2226; min: 0.08 - máx: 31,400 MP/L) wastewater, vinasse, and biosolids (>30,000 MP/L) from wastewater treatment plants are the most frequently reported in the literature for their nutritional potential in agricultural reuse. However, aside from municipal wastewater and biosolids, plastic particles in these other matrices are still largely unexplored, posing a potential threat to soil quality due to the limited understanding of their contribution to soil contamination. The particles accumulate in deeper layers, altering the hydraulic conductivity, fertility, organic matter availability, greenhouse gas emissions, and soil fauna and microorganisms. Nanoplastics have a more pronounced impact than microplastics and represent a greater threat. Due to their vertical mobility, nanoplastics have a greater capacity to accumulate in deep layers, including in groundwater. Different from what is observed for microplastics, current detection and quantification methodologies for nanoplastics are broad and nonspecific. It currently considers extensive size ranges (0-5000 μm), making it difficult to accurately identify these compounds, highlighting the need for more suitable methods for detecting nanoplastics. Given the recognized impacts on soil, it is essential to advance studies to ensure the benefits of reusing wastewater and organic soil amendments while effectively eliminating plastic particles from these matrices to prevent critical contamination scenarios.

Nanoplastic and phthalate induced stress responses in rhizosphere soil: Microbial communities and metabolic networks

The widespread use of plastic products in agriculture has introduced micro-nano plastics (MNPs) and dibutyl phthalate (DBP) into soil ecosystems, disrupting microbial communities and altering metabolite profiles. However, their effects on the rhizosphere soil characteristics of medicinal plants like dandelion remain understudied. This study systematically examined the impact of PS NPs and DBP on rhizosphere microbial communities and metabolites by integrating high-throughput sequencing with liquid chromatography-mass spectrometry. Results demonstrated that individual and combined exposures to PS NPs and DBP decreased soil pH, organic matter content, and enzyme activities while reshaping the diversity, structure, and composition of rhizosphere bacteria and fungi. Notably, bacterial network stability and complexity increased under combined exposure, while fungal networks became more simplified, with a 33.72 % decrease in positive correlations. We identified potential PS NPs and DBP-degrading bacteria and biomarkers, including Nocardioides, Pseudarthrobacter, and Arenimonas. We revealed that co-exposure elevated differential soil metabolites associated with tyrosine metabolism and steroid biosynthesis. The significant positive associations between rhizosphere microorganisms and metabolites highlighted that metabolite accumulation was a key microbial response mechanism to stress. However, within the complex soil environment, the compensatory actions of microorganisms and metabolites were insufficient to mitigate the detrimental effects of PS NPs and DBP, resulting in continued inhibition of dandelion growth by 38.66 %. Consequently, these findings highlight that soil fungi and metabolism play key roles in responding to stress and influencing crop growth, providing novel insights into the impact of nanoparticle and plasticizer exposure on medicinal plant cultivation.

The combination of microplastics and glyphosate affects the microbiome of soil inhabitant Enchytraeus crypticus

Microplastics and pesticides are emerging contaminants that threaten soil ecosystems, yet their combined effects on soil health and soil fauna remain poorly understood. In this study, we constructed a microcosm to assess the individual and combined effects of microplastics and glyphosate on soil physicochemical properties, microbial communities, and the gut microbiome of soil invertebrates (Enchytraeus crypticus). Biodegradable polylactic acid (PLA) and conventional polyethylene terephthalate (PET) were introduced at environmentally relevant concentrations. Our results revealed that PLA had a stronger disruptive effect on soil microbial communities than PET, altering microbial diversity and functional composition. Glyphosate, in contrast, primarily influenced the gut microbiome of E. crypticus, reducing microbial diversity and inducing oxidative stress. Combined exposure to microplastics and glyphosate significantly intensified oxidative stress but did not amplify microbial dysbiosis beyond the effects of microplastics alone. Compare to PET, PLA combined with glyphosate had the most pronounced effects on both soil and gut microbiomes, suggesting that biodegradable microplastics may pose greater ecological risks than conventional microplastics when used alongside pesticides. These findings underscore the need for a reassessment of biodegradable plastic use in agriculture and highlight the complex interactions between microplastics and pesticides in shaping soil ecosystem health.

Characteristics, influencing factors, and ecological risks of microplastics in the north branch tidal marshes of the Yangtze River estuary

Microplastic pollution is a growing global environmental issue, particularly in vulnerable tidal marsh ecosystems, where its environmental behaviour and ecological risks remain poorly understood. This study investigated the microplastic contamination in the north branch tidal marshes of the Yangtze River estuary. Surface sediment samples were collected from 42 stations across 6 transects, revealing an average microplastic abundance of 506.80 ± 386.82 items/kg. The distribution of microplastics was strongly influenced by salinity and vegetation, with seawater intrusion playing a critical role. A significant negative correlation between salinity and microplastic abundance was observed; areas dominated by Phragmites australis (low salinity) had higher microplastic abundance compared to high-salinity areas with sparse vegetation. 12 types of microplastics were identified, with polyethylene and polystyrene being the most abundant (20 % and 19 %, respectively). The most common colours were transparent (26 %) and yellow (23 %), while the predominant shapes were granular (37 %) and fragmentary (32 %). Most microplastics measured under 2000 μm, with the 200-500 μm size range accounting for 49 % of the total. Likely sources of microplastics include aquaculture equipment, industrial products, agricultural cultivation supplies, and daily necessities. Although the ecological risk index for the region is relatively low, the presence of diverse species highlights potential ecological threats.

Polypropylene microplastics reshape diazotrophic community composition and interactions in the plastisphere without affecting the rhizosphere of Capsicum annuum L

Interactions between microorganisms and microplastics play a crucial role in soil biological processes; however, the response of microbial functional groups in the presence of microplastics (MP) remains unclear. In this study, we investigated the diversity and composition of free-living nitrogen-fixing microorganisms (diazotrophs) in the rhizosphere and plastisphere of pepper (Capsicum annuum L.) across three growth stages under MP stress, using an optimized pipeline for functional nifH gene sequence analysis. Our results showed that MP addition suppressed plant growth, although soil properties were not significantly altered, except for soil pH, which was significantly reduced at each plant growth stage. Notable differences in diazotrophic community composition were observed between the rhizosphere and plastisphere, with the genus Rubrivax exhibiting a significantly lower relative abundance in the plastisphere. Moreover, we found strong deterministic assembly processes and intense network structures of diazotrophs in the plastisphere. Interestingly, MP addition did not significantly alter the diversity, composition, or network properties of diazotrophic communities in the rhizosphere compared to control soils. Our study provides insights into the interactions between microbial functional groups and microplastics, enhancing our understanding of the biological processes that drive ecological nutrient cycling and balance in changing environments.

The combined effect of microplastics and tetracycline on soil microbial communities and ARGs

Microplastics (MPs), due to their difficult degradation and adsorption characteristics, are highly prone to form compound contamination with antibiotic residues in the soil environment, thereby disrupting the soil ecosystem. To address this issue of compound contamination, this study investigated the effects of compound contamination composed of three common MPs-polyethylene (PE), polyamide (PA), and polyvinyl chloride (PVC)-combined with tetracycline(TC), on the structure of soil microbial communities and resistance genes. The results showed that the effects of composite pollution on soil physicochemical properties, enzyme activities, bacterial communities, and antibiotic resistance genes (ARGs) were more significant compared to single-contaminant pollution. Among the composite contaminants, TC combined with PVC and PE significantly increased the absolute abundance of the tetC gene, while the composite contamination of TC with PA had the greatest effect on bacterial diversity. This also increased the relative abundance of the phylum Actinobacteria and significantly affected the relative abundance of the phylum Ascomycetes. In addition, significant correlations were found between soil physicochemical properties, enzyme activities, microbial communities, and ARGs. A positive correlation between the intl1 integrator gene and all target genes suggests that horizontal gene transfer contributes to the enrichment of ARGs. Furthermore, the bacterial genera correlated with ARGs-Ascomycetes, Acidobacteria, Actinobacteria, and Anaplasma-are the major bacterial hosts for ARGs in soil samples. This study provides data to support the investigation of combined microplastic and antibiotic contamination in soil.

Polyvinyl Chloride and Polypropylene Microplastics Impact Soil Total Antioxidant Capacity and Exoenzyme Secretions

Microplastics (MPs), notably polyvinyl chloride (PVC) and polypropylene (PP), are major pollutants in terrestrial and aquatic ecosystems. PVC and PP are the most used polymers for manufacturing plastic goods and therefore constitute bulk of plastic debris which are the major sources of MPs. This study examines the impact of PVC and PP MPs on soil total antioxidant capacity (TAC) and microbial exoenzyme activities. A 0.25% (w/w) MP addition significantly reduced soil TAC and the activities of amylase, invertase, and dehydrogenase over 72 h, while cellulase activity increased. The effects varied by MP type, with molecular docking revealing stronger MP binding affinities to exoenzymes for PP than PVC, particularly with cellulase. The findings indicate MPs reduce soil antioxidants and most exoenzyme activities, except for cellulase.

Kinetics of plasticiser release and degradation in soils

Despite the increasing use of emerging phthalate and non-phthalate plasticisers as replacements for restricted phthalates, few studies have investigated their rates of entry and persistence in soils. We investigated release of the emerging plasticiser diethyl hexyl terephthalate (DEHTP) from polyvinyl chloride microplastics (PVC; 4 mm diameter; 21% DEHTP w/w) in soils in a 3-month laboratory study. DEHTP was released rapidly, with 6.6-12.1 ng DEHTP released per mg PVC within <2 h, although this was a small proportion of the amount in the pellets (<0.006%). Degradation rates of 8 phthalate plasticisers and 4 non-phthalate emerging plasticisers in the soils were measured in a separate 3-month laboratory study. For 7 of the 12 plasticisers, pseudo-first order half-lives were <30 days, suggesting relatively low persistence. 5 higher molecular weight plasticisers, including the emerging trioctyl trimellitate and DEHTP, were more persistent, with half-lives >100 days. Plasticiser half-lives in soils were significantly positively correlated with logKOW. Degradation was typically slower in acidic heathland (pH 3.8; organic matter 3.7%), than in alkaline grassland (pH 7.3; OM 16%) or sandy loam agricultural (pH 5.3; OM 5%) soils. Rapid release and potential persistence of some emerging plasticisers in soils indicates that presence of these contaminants may increase in the future.

Ecological effects of micro/nanoplastics on plant-associated food webs

Micro/nanoplastics (MNPs) contamination is a potential threat to global biodiversity and ecosystem functions, with unclear ecological impacts on aboveground (AG) and belowground (BG) food webs in terrestrial ecosystems. Here, we discuss the uptake, ingestion, bioaccumulation, and ecotoxicological effects of MNPs in plants and associated AG-BG biota at various trophic levels. We propose key pathways for MNPs transfer between the AG-BG food webs and elaborate their impact on terrestrial ecosystem multifunctionality. We conclude that MNPs are bioaccumulated in most studied plants and associated AG-BG biota and can be transferred along AG-BG food webs, which may profoundly impact ecosystem functioning. However, most pathways are still untested. Future research on MNPs should focus on the interactions within AG-BG food webs in terrestrial ecosystems.

Microplastics in sandy soils: Alterations in thermal conductivity, surface albedo, and temperature

Rapid growth in plastic production has exacerbated disposal of plastic wastes in terrestrial ecosystems. Unfortunately, soils represent large reservoirs for disposal of microplastics (MPs). MPs infiltrate into the soil through various pathways and alter its intrinsic properties. Despite advances in understanding the impact of MPs on soil physical, biological, and hydrological processes, their influence on surface energy balance and soil temperature remains understudied. Such information is more necessary than ever, considering the ongoing changes to soil systems caused by climate variations and extremes. We conducted laboratory experiments on sandy soils to investigate how MPs with different characteristics impact soil temperature dynamics. The changes in the soil thermal conductivity and surface albedo, in the presence of polyethylene (PE) and polyvinylchloride (PVC) particles at various concentrations were measured. The results demonstrate that MPs, and particularly PVC, with amorphous characteristics may decrease effective thermal conductivity of sand by 38%. Moreover, the deposition of MPs at the surface of samples may increase surface albedo by 28% and 77% with addition of 5% PVC and 5% PE, respectively. Such effects are pronounced at higher soil moisture contents, facilitating migration and deposition of MPs on the surface. We ultimately examined the impact of changes in soil thermal and radiative properties on soil temperature dynamics by monitoring the thermal regime in drying sand columns. Our findings indicate that MPs significantly alter evaporative flux and subsurface temperature profile, hence providing insights into understanding the changes in soil energy balance due to the presence of MPs.

Indoleacetic acid protection against microplastic induced oxidative stress in Pinellia ternata antioxidant enzyme and secondary metabolite regulation

Microplastic (MP) has emerged as a potential threat to crops and agro-ecosystems. The research on their impact on secondary metabolism in medicinal plants and functional foods is limited. Pinellia ternata is a medicinal plant, and its pharmacological characteristics are related to its secondary metabolites. Indole-3-acetic acid (IAA) has been proven to enhance plants' resistance to various abiotic stresses. This study investigated the effects of MP, IAA, and their combination on P. ternata growth, secondary metabolites, reactive oxygen species (ROS) levels, endogenous hormones, and the ascorbic acid-glutathione (AsA-GSH) cycle. Compared with the control group (CK), IAA significantly increased the contents of secondary metabolites, nutrients, ascorbic acid (AsA) and glutathione (GSH). The MP group reduced plant height, tuber weight, ascorbic acid peroxidase (APX), dehydroascorbic acid reductase (DHAR), and soluble protein of P. ternata over the CK. MP + IAA increased tuber weight, APX, DHAR, and soluble protein by 10.3, 26.6, 7.7, 18.2, and 12.5%, respectively, compared with MP. MP elevated the rate of O2·- production, flavonoids, alkaloids, β-sitosterol, and PAL compared to CK. MP + IAA significantly declined the alkaloids, soluble sugar contents, and PAL compared with the MP group. MP reduced DHAR, MDHAR, and APX activities by 30.5, 12.5, and 16.1%, respectively, over the CK. While MP + IAA increased DHAR and APX activities by 18.2 and 7.7%, respectively, compared with MP. Summarily, IAA alleviated the oxidative stress induced by MP and maintained the levels of secondary metabolites, highlighting its potential in protecting the quality of medicinal plants under MP stress.

Effects of polyethylene microplastics on soil microbial assembly and ecosystem multifunctionality in the remote mountain: Altitude matters

Microplastics (MPs) are ubiquitously present in almost every ecosystem globally, including the remote mountains. To date, the effects of MPs on the properties and functioning of soils in remote mountainous ecosystems have been less explored. This study aimed to investigate the ecological impacts of polyethylene (PE) MPs at ∼0.2 % (w/w) on soils in three typical altitude zones of Changbai Mountain, China, including the mixed coniferous and broad-leaved forest (MF) zone, birch forest (BF) zone, and alpine tundra (AT) zone. The results showed that PE MPs exerted diverse effects on soil carbon and nitrogen nutrients across altitude zones but consistently increased soil pH. PE MPs enhanced the humification of soil dissolved organic matter (DOM) and the α-diversity of the bacterial community in the lower-altitude MF zone but exerted negligible effects in the higher-altitude BF and AT zones. Phyla Proteobacteria and Actinobacteria dominated bacterial communities under all treatments but exhibited opposite variation patterns on exposure to MPs. PE MPs contributed to the enrichment of a larger number of carbohydrate-active enzymes (CAZy) gene families in the BF and particularly MF zones. Soil ecosystem multifunctionality was significantly improved by PE MPs in the AT and MF zones but was less affected in the BF zone. The soil bacterial diversity, pH, organic carbon, DOM chemodiversity, and climatic factors (i.e., mean annual temperature) were the pivotal predictors of soil ecosystem multifunctionality. This study provides new insights for evaluating the ecological impacts of MPs on soils in remote mountains.

Soil texture-driven modulation of poly-3-hydroxybutyrate (P3HB) biodegradation: Microbial shifts, and trade-offs between nutrient availability and lettuce growth

Poly-3-hydroxybutyrate (P3HB) is a promising alternative to persistent conventional plastics, capable of biodegrading within months. However, its microbial-driven degradation raises concerns about nutrient immobilization and impacts on plant growth. The biodegradation process occurs in multiple stages, during which shifts in the microbial community can alter soil properties and influence utilization of both intrinsic and polymer-derived organic matter. This study employs a novel approach to investigate how nutrient dynamics during the late stage of P3HB biodegradation affect lettuce (Lactuca sativa var. capitata cv. Brilliant) growth. Soil-to-sand mixtures (100_0, 80_20, 60_40, 40_60, 20_80, and 0_100 ratios) were spiked with P3HB, allowed to biodegrade for eight weeks, and then planted with sprouted lettuce seeds, which were cultivated for another eight weeks. P3HB addition inhibited plant growth and root development in all soil-sand mixtures. However, increasing the sand proportion enhanced plants' nitrogen content by 13-45 % compared to 100 % soil + P3HB. Depending on the sand-to-soil ratio, P3HB stimulated most enzymes involved in carbon, nitrogen and phosphorus acquisition. Basal and substrate-induced respirations were 9-209 % higher under P3HB addition compared to P3HB-free soil, likely due to an increase in the stabilized soil organic matter fraction. Residual P3HB analysis revealed that diluting soil with 20 % sand accelerated biodegradation, despite a decrease in bacterial abundance. In the 80_20 variant, the microbial community shifted toward higher fungal abundance, 19 % more than in 100_0 soil. While microbial proliferation was observed, it effect was outweighed by negative impacts on dry aboveground and root biomass. The highest P3HB biodegradation rate occurred in the 80_20 variant, underscoring soil texture as a critical factor in P3HB biodegradation. While microbial communities can degrade bioplastics, this process may compromise plant nutrient availability and hinder plant growth.

Tiny pollutants, big consequences: investigating the influence of nano- and microplastics on soil properties and plant health with mitigation strategies

The impact of nanoplastics (NPs) and microplastics (MPs) on ecosystems and human health has recently emerged as a significant challenge within the United Nations Agenda 2030, drawing global attention. This paper provides a critical analysis of the influence of plastic particles on plants and soils, with the majority of data collected from recent studies, primarily over the past five years. The absorption and translocation mechanisms of NPs/MPs in plants are first described, followed by an explanation of their effects-especially particles like PE, PS, PVC, PLA, and PES, as well as those contaminated with heavy metals-on plant growth, physiology, germination, oxidative stress, and nutrient uptake. The study also links the characteristics of plastics (size, shape, concentration, type, degradability) to changes in the physical, chemical, and microbial properties of soils. Various mitigation strategies, including physical, chemical, and biological processes, are explored to understand how they address these changes. However, further research, including both laboratory and field investigations, is urgently needed to address knowledge gaps, particularly regarding the long-term effects of MPs, their underlying mechanisms, ecotoxicological impacts, and the complex interactions between MPs and soil properties. This research is crucial for advancing sustainability from various perspectives and should contribute significantly toward achieving sustainable development goals (SDGs).

Exploring the response of bacterial community functions to microplastic features in lake ecosystems through interpretable machine learning

Microplastics (MPs) are ubiquitous and have various characteristics. However, their impacts on bacterial community functions in lakes remain elusive. In this study, we identified 33 different MPs features including their abundance, shape, color, size, and polymer type, from Taihu Lake, China. These features were used to construct 48 machine learning models, utilizing four types of machine learning regression algorithms, to investigate how different MP features influence human health, carbon/nitrogen cycling, and energy source-related functions of bacterial communities. The XGBoost models provided the best performance with an average R2 of 0.85 in explaining the abundance of functions. Yellow-, fragment-, and polyethylene terephthalate (PET) MPs were the most important features by Shapley values. Yellow- and PET-MPs mainly had primarily negative impacts on human pathogens pneumonia and chemoheterotrophy, respectively. Fragment-MPs had a primarily positive impact, which shifted from positive to negative at a proportion of 0.5 for methanol oxidation. Moreover, MPs may affect community structure by filtering for functional traits. These findings are important for understanding the effects of MP pollution on bacterial community function and its role in the global carbon and nitrogen cycling and human health and help us to determine the potential impacts of MP pollution on ecosystems.

Vertical distribution of microplastics in soil affects plant response to microplastics

The impacts of microplastics on plants have been extensively researched, yielding a variety of responses: promoting growth, limiting growth, or causing no change in plants. Experimental studies, following basic principles of ecotoxicology, typically use a homogeneous distribution of microplastics in soils, where soil and microplastic are well-mixed. However, in the environment, plastic is not homogeneously distributed. Therefore, we tested whether the distribution of microplastics in soils affects the impact observed on plants. For this purpose, we tested the effect of homogeneously distributed microplastics and heterogeneously distributed microplastics (at different levels) on the growth of spring onions. In addition, the presence of drought was also included in our greenhouse experiment. The results show that the distribution of microplastics (whether it is homogeneous or heterogeneous) affects the growth of spring onions differently, especially the shoot and root mass. First, differences of 21-22 % in shoot mass and 29-38 % in root mass were observed between heterogeneously distributed treatments and the homogeneous treatment. Second, under drought conditions, the effects -particularly on shoot mass and the C:N (carbon:nitrogen) ratio- may differ compared to non-drought. Differences of 30-37 % in shoot mass, and up to 16 % in the carbon/nitrogen ratio were observed between different heterogeneously distributed treatments and the homogeneous treatment in the drought case. In addition, shoot mass and the C:N ratio varied depending on drought conditions. Our results strongly suggest that future experiments on microplastic effects in soil should consider at least vertically heterogeneity of the pollutant to arrive at more realistic effect estimates.

Microbial diversity in active and abandoned desert kangaroo rat burrows and from proximal surface sand

Desert kangaroo rats (Dipodomys deserti) construct burrows that can create micro-niches favorable to increased microbial activity. The aim of this study was to characterize the bacterial communities found in kangaroo rat burrows, in proximal desert surface sand, and in samples from kangaroo rats. We collected samples from burrow ceilings of actively inhabited burrows, from burrows that were no longer in use, and from the proximal surface sand in the Sonoran Desert, Yuma, AZ. Following DNA extraction from samples, 16S rRNA gene sequencing was performed, and functional predictions were made and assessed for each characterized bacterial community. Active burrow samples exhibited greater alpha diversity but similar beta diversity when compared to surface sand (P < 0.05), with no significant differences observed between abandoned and active burrows. Bacterial genera and genes related to nitrogen fixation, nitrification, and urea hydrolysis were found in significantly higher abundance in active burrows compared to the surface sand (P < 0.05). The core microbiome of active burrow samples was different from surface sand, including higher abundances of Acidimicrobiales and Acidobacteria subdivision Gp7. Active burrow samples included 30 unique genera. Kangaroo rat anal swabs shared 12, cheek pouches shared 6 unique genera with burrows. These findings suggest that kangaroo rats can shape the microbial composition of their burrow environment through the introduction of food material and waste, facilitating increased species richness and bacterial diversity.IMPORTANCEAnimals can alter soil parameters, including microbial composition through burrowing activities, excretion, and dietary composition. Desert kangaroo rats (Dipodomys deserti) construct burrows within loose desert sand that have microclimatic conditions different from the surrounding desert climate. In this study, we explored the effect of disturbance from kangaroo rat activities on the bacterial composition of sand. We compared the bacterial community compositions of kangaroo rat (D. deserti) samples, their burrows, and the proximal surface sand. The results showed that burrow sand shows higher richness and diversity of bacterial community with higher abundances of bacterial genera and genes associated with nitrogen fixation, nitrification, and urea hydrolysis compared to the surface sand. These findings suggest that kangaroo rats affect the microbial composition of their burrow environment through the introduction of food material and waste.

Soil nitrogen deficiency aggravated the aging of biodegradable microplastics in paddy soil under the input of organic substances with contrasting C/N ratios

The application of organic substances to the agricultural field has effectively enhanced soil nutrient levels and crop yields. Biodegradable microplastics (bio-MPs), a pervasive emerging contaminant, may potentially impact the soil ecosystem through their aging process. Here, a 150-day dark incubation experiment was conducted to elucidate the disparities in the aging process of polylactic acid bio-MPs (PLA-MPs) in soils with contrasting C/N ratios of organic substances, as the mechanisms underlying this process remain unclear. The study found that PLA-MPs resulted in an increase in soil pH, nutrient levels, and organic carbon content in soil-straw system. Additionally, PLA-MPs significantly influenced bacterial community composition and microbial metabolic activity in soil-straw system. Notably, more pronounced aging features of PLA-MPs was observed in soil-straw system (lower soil nitrogen environment) compared to soil-fertilizer system (higher soil nitrogen environment). Under lower soil nitrogen conditions, microorganisms may accelerate the aging process of PLA-MPs due to their preference for readily available energy sources; conversely, under higher soil nitrogen conditions, the aging of PLA-MPs may be decelerated as microorganisms preferentially utilize substances with easily accessible energy sources. Our findings provide valuable insights into the interaction between PLA-MPs and soil amended with the organic substances of contrasting C/N ratios.

Biodegradable microplastics affect tomato (Solanum lycopersicum L.) growth by interfering rhizosphere key phylotypes

Biodegradable microplastics (BMPs), which form as biodegradable plastics degrade in agricultural settings, may influence plant growth and soil health. This study investigates the effects of BMPs on tomato growth and the microbial mechanisms involved. A greenhouse experiment applied BMPs-polyhydroxyalkanoate (PHA), polylactic acid (PLA), poly(butylene succinate-co-butylene adipate) (PBSA), and poly(butylene-adipate-co-terephthalate) (PBAT)-to tomato plants. The study analyzed their effects on plant growth, soil properties, and rhizosphere microbial communities. BMP treatments significantly reduced tomato biomass, height, and chlorophyll content compared to the control. PLA0.1 decreased the chlorophyll a/b ratio, while PLA1 increased it. Elemental analysis showed PLA1 increased phosphorus, calcium, and potassium in leaves, whereas all BMPs reduced nitrogen levels. BMPs also altered soil nitrogen and DOC levels, significantly shifting rhizosphere microbial communities, with a notable increase in Betaproteobacteria abundance. Ecological network analysis revealed that BMPs disrupted key microbial modules linked to plant growth. Beneficial modules positively associated with biomass and nutrient uptake were reduced under BMP treatments, whereas harmful microbial taxa in module 3, associated to poor plant health, were promoted. These shifts suggest that BMPs disrupt microbial ecological relationships critical for optimal plant growth. The findings highlight the potential negative impacts of BMPs on tomato growth through changes in microbial dynamics and soil properties.

Exposure to mm-scale microplastic particles does not cause weight loss in two earthworm species belonging to different ecological groups

The aim of this study was to estimate the effect of relatively large (1-5 mm) fragments of high-density polyethylene films on two widespread earthworm species belonging to different ecological groups-endogeic Aporrectodea caliginosa and epigeic Lumbricus rubellus. In a microcosm experiment lasting 8 weeks, we tested the food dilution hypothesis, which suggests that the adverse effect of microplastic on earthworms is caused by the dilution of food by plastic, which has zero energetic value. Both earthworm species ingested plastic particles, and both species were seemingly limited by the availability of food. In particular, the addition of food substrate (aspen litter) to the soil had a significant positive effect on the weight of A. caliginosa. In contrast to our expectations, microplastic at relatively high concentrations (0.3% and 2.3% w/w in the soil for A. caliginosa, and 33% and 48% w/w in the litter for L. rubellus) had no significant effect on earthworm biomass. This suggests that the food dilution effect is not likely to be the main mechanism of the adverse effect of microplastic on earthworms. Our work adds to the growing evidence that in many cases microplastic does not harm soil animals.

Microplastic exposure reduces seed germination in a coastal plant

Plastic contamination presents major environmental threats through its degradation into micro-sized particles that are harmful to a variety of organisms, including plants. Among terrestrial habitats, coastal dunes are likely some of the most plastic-polluted, but very few studies thus far have examined microplastic effects on wild plants native to this habitat. Moreover, current research on microplastics has limited environmental relevancy due to the common use of homogenously shaped un-weathered microplastics in exceeding concentrations. Our research examined the effects of microplastics from biodegradable and non-biodegradable origin, in their pristine (raw) and weathered form, at a concentration of 106 particles per ml, on the native coastal plant Cutandia maritima. We first synthesized engineered microplastics of high environmental relevancy from bulk plastic products. Then, we exposed C. maritima plants to the microplastics in the soil. While no effect was found on the plants following chronic exposure to all microplastic types, weathered plastic reduced seed germination after exposure of the mother plants, suggesting epigenetic modifications might have an effect at the embryo stage. In contrast, direct exposure of microplastics, specifically polylactic acid, facilitated seeds germination. Our results highlight the importance of studying the effects of microplastic on seed germination and raise the ongoing ecological consequences of environmental microplastic coastal contamination, which should be taken into account in regulatory and environmental assessments.

Effects of long-term wastewater irrigation on microplastics pollution in agricultural soil

Microplastic (MP) pollution in agroecosystems is a growing concern with unknown consequences for sustainable agricultural activities. Few studies have revealed MPs in soil as a result of wastewater irrigation, despite the increasing application of wastewater irrigation and inadequacy of conventional wastewater treatment plants in removing microplastics (MPs). In this study, the effect of treated wastewater (TWW) irrigation on MPs accumulation in agricultural soils of Konya City (in Türkiye) and the potential risks on agricultural ecosystem were investigated. For this purpose, 202 soil samples taken from 90 TWW irrigated lands and 11 non-agricultural control lands, at depths of 0-10 cm and 10-20 cm, were analyzed for color, shape, and polymer type. The risk level of MPs pollution was determined by the pollution factor (CF), pollution load index (PLI), and polymer risk index (H). The relationship between some physico-chemical properties of the soil and MPs pollution level was also analyzed. The findings of this study revealed a significant difference (P < 0.0001) in the MP count in the TWW irrigated soils, and control soils. While the average numbers of MPs for control soils were 169 ± 46.8 MPs/kg (100-220 MPs/kg) and 140 ± 44.7 MPs/kg (80-240 MPs/kg) for the 0-10 cm and 10-20 cm soil depths, respectively; 329 ± 139.5 MPs/kg (100-840 MPs/kg) and 295 ± 115.4 MPs/kg (80-660 MPs/kg) were identified for TWW irrigated soil samples taken from the same soil depths. Fiber, film, and fragment type MPs were found to be dominant polymer types in TWW irrigated soil, with 56%, 23%, and 16%, respectively. Transparent colored MPs were predominant. MP decreased from 0-10 cm to 10-20 cm depths. Most of the samples were significantly contaminated with MPs (3 ≤ CF < 6), categorized in hazard category class I (PLI < 10). The findings of this study indicate that TWW irrigation increases the accumulation of MPs in agricultural soils, which poses a higher risk to more fertile soils with higher organic matter, total nitrogen, and available phosphorus content. Hazard index assessments reveal that the soils of Konya, often referred to as the "granary of Türkiye," are at risk of MPs contamination. The findings showed that MPs, a neglected type of pollution for soil, will become an even more important problem with increasing wastewater irrigation.

Arbuscular mycorrhizal fungi improve treatment performance and vegetative resilience in constructed wetlands exposed to microplastics

Microplastics are increasingly present in municipal wastewater and wastewater treatment plant effluent, prompting the use of constructed wetlands (CWs) for additional treatment. Enhancing CWs with arbuscular mycorrhizal fungi (AMF), known to aid nutrient removal and alleviate plant pollution stress, is gaining interest. This study is the first to examine the influence of two microplastic polymers (polyethylene microspheres and polyester microfibers) at concentrations of 0.1 and 1 mg/L on nutrient removal, plant health, and microbial composition in AMF-inoculated CWs. The results indicate that AMF inoculation combined with microplastic treatments significantly enhances nutrient removal in wetlands, achieving a 45.7% increase in total nitrogen removal and a 25.3% increase in phosphate removal. The effects of microplastics on plant health vary depending on the inoculation status, with an increase in lipid peroxidation (73.4% ± 25.4), and a decrease in the effective quantum yield of PSII (13.4% ± 5) observed in all treatments. High concentrations of polyester microfibers significantly altered the microbial community, increasing AMF colonization frequency and microbial richness, decreasing evenness and the abundance of denitrifying genera, and creating distinct clusters in beta diversity analysis. AMF inoculation maintained higher species richness and evenness, contributing to the resilience of CWs to microplastic pollution. Overall, AMF-inoculated wetlands and plants showed superior treatment performance, highlighting the successful bio-augmentation potential of this approach.

UV-aging reduces the effects of biodegradable microplastics on soil sulfamethoxazole degradation and sul genes development

In recent years, the biodegradable plastics has extensively used in industry, agriculture, and daily life. Herein, the effects of two biodegradable microplastics (BMPs), poly(butyleneadipate-co-terephthalate) (PBAT) and polyhydroxyalkanoate (PHA), on soil sulfamethoxazole (SMX) degradation and sul genes development were comparatively studied based on the type, dosage, and state. The addition of virgin BMPs significantly increased soil DOC following a sequential order PBAT > PHA and high dose > low dose. Meanwhile virgin PBAT significantly reduced soil pH. In general, the addition of BMPs not only promoted soil SMX degradation but also increased the abundance of sul genes, with an exception that pH reduction in virgin PBAT inhibited the proliferation of sul genes. The driving effects of BMPs on soil microbial diversity following the same order as that on DOC. Specific bacteria stimulated by BMPs, such as Arthrobacter and two genera affiliated with phylum TM7, accounted for the accelerated degradation of SMX. Intriguingly, UV-aging hindered the release of DOC from BMPs and the reduction in pH, mitigated the stimulation of microbial communities, and ultimately reduced the promotion effect of BMPs on SMX degradation and sul genes proliferation. Our results suggest that more attention should be paid to the proliferation risk of ARGs in the environment affected by BMPs and UV-aging can be employed sometimes to reduce this risk.

Simulated Microplastic Release from Cutting Boards and Evaluation of Intestinal Inflammation and Gut Microbiota in Mice

BACKGROUND

Plastic cutting boards are commonly used in food preparation, increasing human exposure to microplastics (MPs). However, the health implications are still not well understood.

OBJECTIVES

The objective of this study was to assess the impacts of long-term exposure to MPs released from cutting boards on intestinal inflammation and gut microbiota.

METHODS

MPs were incorporated into mouse diets by cutting the food on polypropylene (PP), polyethylene (PE), and willow wooden (WB) cutting boards, and the diets were fed to mice over periods of 4 and 12 wk. Serum levels of C-reactive protein (CRP), tumor necrosis factor-α (TNF-α ), interleukin-10 (IL-10), lipopolysaccharide (LPS, an endotoxin), and carcinoembryonic antigen (CEA), along with ileum and colon levels of interleukin-1β (IL-1 β ), TNF-α , malondialdehyde (MDA), superoxide dismutase (SOD), secretory immunoglobulin A (sIgA), and myosin light chain kinase (MLCK), were measured using mouse enzyme-linked immunosorbent assay (ELISA) kits. The mRNA expression of mucin 2 and intestinal tight junction proteins in mouse ileum and colon tissues was quantified using real-time quantitative reverse transcription polymerase chain reaction. Fecal microbiota, fecal metabolomics, and liver metabolomics were characterized.

RESULTS

PP and PE cutting boards released MPs, with concentrations reaching 1,088 ± 95.0 and 1,211 ± 322 μ g / g in diets, respectively, and displaying mean particle sizes of 10.4 ± 0.96 vs. 27.4 ± 1.45 μ m . Mice fed diets prepared on PP cutting boards for 12 wk exhibited significantly higher serum levels of LPS, CRP, TNF-α , IL-10, and CEA, as well as higher levels of IL-1β , TNF-α , MDA, SOD, and MLCK in the ileum and colon compared with mice fed diets prepared on WB cutting boards. These mice also showed lower relative expression of Occludin and Zonula occludens-1 in the ileum and colon. In contrast, mice exposed to diets prepared on PE cutting boards for 12 wk did not show evident inflammation; however, there was a significant decrease in the relative abundance of Firmicutes and an increase in Desulfobacterota compared with those fed diets prepared on WB cutting boards, and exposure to diets prepared on PE cutting boards over 12 wk also altered mouse fecal and liver metabolites compared with those fed diets prepared on WB cutting boards.

DISCUSSION

The findings suggest that MPs from PP cutting boards impair intestinal barrier function and induce inflammation, whereas those from PE cutting boards affect the gut microbiota, gut metabolism, and liver metabolism in the mouse model. These findings offer crucial insights into the safe use of plastic cutting boards. https://doi.org/10.1289/EHP15472.

Microplastic-Induced Alterations in Soil Aggregate-Associated Carbon Stabilization Pathways: Evidence from δ13C Signature Analysis

Microplastics (MPs) are known to affect soil carbon stability in a numerous ways. However, the mechanisms by which they alter the carbon stability within soil aggregates remain unclear . Herein, a one-year field experiment was conducted in an arid agricultural region employing stable isotope techniques to evaluate the soil organic carbon flow in the presence of both persistent (PE, PVC) and biodegradable (PLA, PHA) MPs. PE and PVC reduced the stability of soil aggregates, while PLA and PHA maintained it. Additionally, organic carbon content increased in microaggregates but decreased in small macroaggregates for PE and PVC treatments. By contrast, treatment with PLA and PHA enhanced organic carbon content across aggregates. The δ13C values of PE- and PVC-treated aggregates ranged from -25.34 to -20.85‰, while those of PLA and PHA ranged from -16.29 to -9.26‰. Notably, MPs altered the direction of carbon flow between aggregates, reduced carbon flux, and accelerated carbon emissions. RFP and PLS-PM analyses revealed that persistent MPs affected carbon flow primarily via abiotic factors, whereas biodegradable MPs influenced it via biotic factors. These findings provide insights into the mechanisms by which MPs impact aggregate-associated carbon, highlighting their effects on soil ecosystem services.

Microplastics in agricultural soils: sources, impacts on soil organisms, plants, and humans

Agricultural land has long been regarded as a resource for food production, but over time, the effects of climate change have reduced the ability of soil to produce food efficiently. Nowadays, farmers have moved from traditional to modern techniques of farming. Across the globe, plastic mulching has become widely used on farmlands. According to a few studies, the breakdown of plastic mulches releases microplastics (MPs) into the soil. Despite studies reporting the presence of MPs in soils, there are limited studies on the sources and impacts on soil organisms, plant growth, fruits, and human health. This study evaluated research articles collected from the Web of Science to assess the origin of MP in soil and crops and its effects on soil organisms, plants, and humans. It was observed that MPs come from different sources such as waste water, organic fertilizer, irrigation water, sewage, and sludge. Plastic mulching, which can spread across agricultural fields at varying depths, is the dominant source. Furthermore, it was observed that MPs alter crop quality, reduce the leaf count of wheat, and decrease the root length of crops such as maize, water spinach, black gram, and garden cress. MP can decrease the abundance of soil microarthropods and nematodes, damage the intestinal walls of earthworms, and reduce the feeding and excretion of snails. MP causes liver damage, inflammation, respiratory irritation, and immunological issues. Ultimately, these contaminants (MPs) can transfer and have been detected in fruits and vegetables, which pose adverse effects on human health.

Potential impacts of microplastic pollution on soil-water-plant dynamics

This study was designed to assess the potential impact of microplastic (MP) pollution on soil hydrology, specifically in retaining and releasing moisture. Herein, High-Density Polyethylene (HDPE) MP of different sizes (i.e., 0.5-1, 1-3, and 3-5 mm) and shapes (i.e., fiber, film, and fragment) were evaluated for their effects on water retention curve (WRC) of sandy loam soil, chosen for its agricultural relevance and widespread environmental presence of HDPE. Nine contamination scenarios were simulated with a low MP pollution rate, 0.01% w/w. Van Genuchten models were used to assess plant available water (PAW), wilting point (WP), and water holding capacity (WHC). Results showed that studied MP could significantly affect WRC and PAW mainly by changing WHC rather than WP and that this effect varied with MP shape and size. According to the results, fragment MP had the greatest impact on soil WHC by increasing 36.3%, followed by fibers and films by 19.8% and 15.7%. MP particles significantly increased WHC, while WP remained relatively unchanged. An observed trend indicated that the impact on WHC increased with the size of the MP particles. These findings emphasize the need to manage soil MP pollution to protect plant growth, agriculture, and water dynamics.

Assessing the impact of micro and nanoplastics on the productivity of vegetable crops in terrestrial horticulture: a comprehensive review

Micro and nano plastics (MNPs) pollution has emerged as a significant environmental issue in recent years. Plastic contamination in the environment poses risks to both human health and other organisms within the ecosystem. This review discusses the overall impact of MNPs on the performance of vegetable crops, including a global perspective on the topic. Bibliometric analysis reveals that most research on this subject has been concentrated in a few countries, although the number of studies has notably increased in recent years. MNPs accumulate in arable lands due to human activities, often altering the soil's physical, chemical, and biological properties in the rhizosphere. Vegetable crops absorb these MNPs mainly through their roots, leading to accumulation in the edible parts of the plants. Consequently, this results in phytotoxic symptoms and poor growth and development. The phytotoxic effects of MNPs are attributed to genetic and metabolic changes within the plant's cellular structure. Current research on MNPs has been limited to a few vegetable cultivars. Future studies should encompass a broader range of vegetable crops under both laboratory and field conditions to advance this burgeoning field of research. Additionally, examining various types of plastics is essential to comprehensively understanding their impact.

Polyethylene microplastics inhibit the growth and reproduction of Colorado potato beetle and the predation efficiency of Stinkbug

Microplastics, as an environmental pollutant, are receiving increasing attention due to their ubiquitous presence in ecosystems and their ability to transfer and accumulate through food chains. Although it is well known that microplastics can enter plants through nutrient and water uptake by plant roots, the effects of microplastics on the growth, development and predation efficiency of herbivorous insects and predatory natural enemies after transfer from plants are still lacking. In order to investigate the impacts of polyethylene microplastics (PE-MPs) on the growth, reproduction of herbivorous insects and the predation efficiency of their predatory natural enemies, the quarantine pest globally - Leptinotarsa decemlineata and its predatory natural enemy - the Arma chinensis were selected as the research objects. Constructed a transfer system of polyethylene microplastics (PE-MPs) soil - potato plants - L. decemlineata and PE-MPs feed - Tenebrio molitor - A. chinensis. The key attention is paid to the reproduction, growth, and development of the L. decemlineata, as well as changes in the predation behavior and ability of A. chinensis against the L. decemlineata. We found that PE-MPs treatment reduced the egg production of adult L. decemlineata, prolonged their developmental time, and decreased their survival rate. Additionally, it extended the resting time, searching time, paralyzing time, and the latent period of A. chinensis, while decreasing the predation amount of A. chinensis on L. decemlineata larvae. Although the effects of PE-MPs on the growth and reproduction of L. decemlineata and the predatory efficiency of armpit A. chinensis were limited, our study still revealed the adverse effects of PE-MPs on phytophagous pests and predatory natural enemies. Finally, the mechanisms underlying these effects remain uncertain, necessitating further research to assess whether microplastics have potential long-term impacts on interactions between herbivorous insects and their predatory enemies. Collectively, these studies provide new insights into the effects of microplastics on herbivorous insects and predatory natural enemies.

Transcription-metabolism analysis of various signal transduction pathways in Brassica chinensis L. exposed to PLA-MPs

Biodegradable plastics, regarded as an ideal substitute for traditional plastics, are increasingly utilized across various industries. However, due to their unique degradation properties, they can generate microplastics (MPs) at a faster rate, potentially posing a threat to plant development. This study employed transcriptomics and metabolomics to investigate the effects of polylactic acid microplastics (PLA-MPs) on the physiological and biochemical characteristics of Brassica chinensis L. over different periods. The findings indicated that exposure to varying concentrations of PLA-MPs had distinct influences on the growth and development of Brassica chinensis L. Transcriptomic analysis showed different concentrations of PLA-MPs directly influenced the expression of genes associated with plant hormones, such as SnRK2 and BnaA01g27170D. In addition, it was observed that these PLA-MPs also impacted plant growth and development by modulating the expression of other genes, eg. related to sulfur metabolism and glycerophosphate metabolism. Metabolomic analysis demonstrated alterations levels of metabolites such as L-glutamine, and arginine in response to PLA-MPs, which influenced pathways related to vitamin B6 metabolism, the one-carbon folate pool, glycerophospholipid metabolism, and cysteine. This study offers new insights into the potential impacts of biodegradable microplastics (BMPs) on plants and underscores the need for further investigation into the potentially more significant effects of BMPs on terrestrial ecosystems.

Smallest microplastics intensify maize yield decline, soil processes and consequent global warming potential

Microplastic pollution seriously affects global agroecosystems, strongly influencing soil processes and crop growth. Microplastics impact could be size-dependent, yet relevant field experiments are scarce. We conducted a field experiment in a soil-maize agroecosystem to assess interactions between microplastic types and sizes. Microplastics were added to soils used for maize cultivation: either polyethylene or polystyrene, of 75, 150, or 300 µm size. Overall, we found that microplastic contamination led to increased soil carbon, nitrogen and biogeochemical cycling. Polyethylene contamination was generally more detrimental than polystyrene. Smallest polyethylene microplastics (75 µm) were associated with two-fold raised CO2 and N2O emissions - hypothetically via raised microbial metabolic rates. Increased net greenhouse gases emissions were calculated to raise soil global warming potential of soils. We infer that MPs-associated emissions arose from altered soil processes. Polyethylene of 75 µm size caused the greatest reduction in soil carbon and nitrogen pools (1-1.5 %), with lesser impacts of larger microplastics. These smallest polyethylene microplastics caused the greatest declines in maize productivity (∼ 2-fold), but had no significant impact on harvest index. Scanning electron microscopy indicated that microplastics were taken up by the roots of maize plants, then also translocated to stems and leaves. These results raise serious concerns for the impact of microplastics pollution on future soil bio-geochemical cycling, food security and climate change. As microplastics will progressively degrade to smaller sizes, the environmental and agricultural impacts of current microplastics contamination of soils could increase over time; exacerbating potential planetary boundary threats.

Impact of particle size and oxide phase on microplastic transport through iron oxide-coated sand

The presence of microplastics in aquatic environments threatens the ecological system and human health. This study investigates the transport and retention of polystyrene microplastics (PSMPs) in clean sand, and hematite-, goethite-, and magnetite-coated iron oxide - sands as a function of size ratio and ionic strength. The breakthrough curves (BTCs), retention profiles, and hydraulic pressure were measured through soil-column experiments, and the retention of PSMPs was assessed from the observed BTCs, RPs and first-order attachment coefficients. In addition, the maximum attachment capacity was evaluated to assess the long-term retention of PSMPs. Experimental data showed that the retention of PSMPs increased in the order of goethite-, hematite-, and magnetite-coated sands in all size ratios, which is consistent with the order of attraction energy calculated by extended Derjaguin-Landau-Verwey-Overbeek theory. The findings demonstrated the feasibility of mitigating the transport of microplastic particles using naturally abundant iron-rich soils.

Plastics aplenty in paddy lands: incidence of microplastics in Indian rice fields and ecotoxicity on paddy field phytoplankton

Occurrence of microplastics (MP) in natural paddy fields and its impact are less studied. This study reports the abundance of MP in two paddy fields of Kerala, India, cultivating rice crops, 'Pokkali' and 'Uma' crops, which are vital to Kerala's food security and climate resilience. Fourier transform infrared spectroscopy (FTIR) analyses confirmed the presence of polyethylene (PE) and polypropylene (PP) fragments as major MP in the surface water of paddy fields during vegetative (transplantation) and ripening (near harvesting) phases. MP density in the vegetative phase of 'Pokkali' (1370 ± 468.51 fragments/m3) and 'Uma' (1110 ± 304.96 fragments/m3) was thrice more than the ripening phase concentrations (400 ± 196.85 and 370 ± 57.00 fragments/m3, respectively). Subsequently, ecotoxicity of MP and plastic leachates (PL) on phytoplankton that are naturally found in rice fields was examined. Microalga, Chlorococcum sp., and cyanobacterium, Synechococcus sp., were grown in modified BG11 and BG11 media, respectively, and tested with paddy field concentrations for PE-MP and PE-PL. MP bestowed a significant hormetic effect on the specific growth rate of the microalga (121% of the control) whereas the cyanobacterial growth was negatively impacted (70% of the control). Both phytoplankton exhibited a similar response when exposed to PL, but results were neither dose-dependent nor significant. Further, increased catalase activity and compromised superoxide dismutase machinery in the cyanobacterium corroborated the toxic impact on growth (p ≤ 0.05), which indicates reactive oxygen species (ROS) generation in MP-treated groups. ROS generation indicates oxidative stress following MP exposure in the studied phytoplankton perhaps through surface contact or by leaching of toxic intermediates into the medium. The distinctive responses of paddy field phytoplankton to MP and PL stress suggest that MP pollution may enrich certain resilient species over others leading to a possible change in phytoplankton community structure. Pollution load indices suggest that even environmental concentrations of MP and PL may affect the rice productivity as paddy field phytoplankton play a significant role in sustaining and enhancing crop health. Therefore, the presence of MP at alarming concentrations in the paddy fields signifies the emergence of a global environmental and food security concern.

Environmental release behavior, cell toxicity and intracellular distribution of novel biodegradable plastic materials

In response to the increasingly severe issue of plastic waste, biodegradable plastics have garnered extensive attention as a potential alternative to traditional plastics. Among these materials, biodegradable plastics hold a dominant position. The objective of this study was to assess the environmental risks of five commercially available biodegradable plastics: polyglycolic acid (PGA), polylactic acid (PLA), poly(butylene succinate) (PBS), poly(butylene carbonate) (PBC), and poly(butylene adipate-co-terephthalate) (PBAT). The evaluation included their physical properties, microplastic release behavior, and cytotoxicity. In addition, the effect of age process on the environmental behavior of biodegradable plastic materials was further investigated. The results revealed that PGA and PBS exhibited lower risks in terms of microplastic release, whereas PLA demonstrated higher environmental mobility. Further cytotoxicity experiments indicated that PLA and PBS exerted significant toxic effects on human cell lines, including human normal liver cells (LO2), human monocytic leukemia cells (THP-1), human umbilical vein endothelial cells (HUVECs), and human colon carcinoma cells (Caco-2). Additionally, this study utilized Nile Red labeling to observe the co-culture system of PGA with THP-1 cells, uncovering that THP-1 cells gradually engulfed and internalized PGA microplastics over time. This finding provides new insights into the potential mechanism by which microplastics promote cell proliferation. Moreover, we also found that the aging process partially reduced the cytotoxicity of PGA, but had little effect on environmental mobility. Considering the comprehensive research findings, PGA is considered an ideal material for large-scale applications due to its low cytotoxicity and environmental risks. In contrast, the environmental safety of other types of plastics requires more comprehensive risk assessment to determine their suitability. This study provides significant scientific evidence for the environmental impact assessment of biodegradable plastics and plays a crucial role in promoting the development of sustainable plastic alternatives.

The coexistence characteristics of microplastics and heavy metals in rhizomes of traditional Chinese medicine in mulch planting area

Rhizomatous traditional Chinese medicines (RTCMs) are widely crushed into powder and swallowed directly as medicine and food or health products to treat various diseases; however, they may contain toxic microplastics (MPs) and heavy metals. Currently, there are no reports on the detection of MPs and MP-heavy metal synergies in RTCMs. In this study, we selected eight representative RTCMs to investigate the abundance, types, sizes, and polymers of MP and heavy metals and to assess the level of contamination of MPs and synergies between MPs and heavy metals in RTCMs. The abundance of MPs in different RTCM ranged from 20.83 to 43.65 items/g. The dominant type was fragment (95.43%), and the dominant particle size was < 0.5 mm (73.72%) in MPs. Polyurethane (PU) (29.21%) and acrylics (ACR 13.53%) were the dominant polymers of MP. MP polymers showed obvious correlations with type and particle size: PU was enriched in 0-50-mm and 100-300-mm fragments, whereas ethylene vinyl acetate and ACR were enriched in 0-30-mm fibers. The heavy metals arsenic (As), lead (Pb), and chromium (Cr) were found to be more susceptible to synergistic contamination with MPs in RTCMs compared to other heavy metals. The estimated daily intake (EDI) of the MPs and heavy metals for RG (Rehmannia glutinosa) and RAY (Rhizoma atractylodis) were higher than others. The results showed that MP pollution is common in RTCMs and carries the potential risk of heavy metal or MP poisoning in humans who consume RTCMs.

Evaluating the impacts of microplastics on agricultural soil physical, chemical properties, and toxic metal availability: An emerging concern for sustainable agriculture

Microplastics (MPs) are an emerging environmental issue that might endanger the health of agricultural soil. Even though several research on the particular toxicity of MPs to species have been carried out, there is little information on MPs' impacts on soil physicochemical properties and heavy metals (HMs) availability of HMs contaminated and without contaminated soils. This study examined the changes in soil characteristics for both HMs contaminated and without contaminated soils by five distinct MPs, including Polyethylene (PE), Polyethylene terephthalate (PET), Polystyrene Foam (PS), Polyamide (PA), and a combination of these four types of MPs (Mixed MPs), at two different concentrations (0.2% and 1%; w/w), where soil incubation experiments were setup for this studies and the standard analytical techniques employed to measure soil characteristics and toxic metal availability. After the ending of soil incubation studies (90 days), significant changes have been observed for physicochemical properties [bulk density, porosity, water holding capacity, pH, electrical conductivity (EC), organic carbon (OC), and organic matter (OM)]. The soil nutrients change in descending order was found as NH4+ -N> PO43+ > Na > Ca > NO3- > Mg for lower concentrations of MPs compared to higher concentrations. The HMs availability is reducing with increasing MPs concentration and the descending order for metal availability was as follows Pb > Zn > Cd > Cr > Cu > Ni. Based on MP type, the following descending order of MPs PS > Mix (MPs) > PA > PET > PE, respectively act as a soil properties influencer. Usually, effects were reliant on MPs' category and concentrations. Finally, this study concludes that MPs may modify metal movements, and soil quality; consequently, a possible threat will be created for soil health.

From plankton to fish: The multifaceted threat of microplastics in freshwater environments

The detrimental impact of emerging pollutants, specifically microplastics (MPs), on the ecological environment are receiving increasing attention. Freshwater ecosystems serve as both repositories for terrestrial microplastic (MP) sources and conduits for their subsequent entry into marine environments. Consequently, it is imperative to rigorously investigate the toxicological effects of MPs on freshwater ecosystems. This article provides a comprehensive analysis of the ecological toxicity effects of MP pollution, both in isolation and in combination with other pollutants, on freshwater aquatic organisms, including plankton, benthic organisms, and fish. The review elucidates potential mechanisms underlying these effects, which encompass oxidative stress, metabolic disorders, immune and inflammatory responses, dysbiosis of the gut microbiota, DNA damage, and cell apoptosis. This paper advocates for the integrated application of multi-omics technologies to investigate the molecular mechanisms underlying the toxicity of MPs to freshwater aquatic organisms from interdisciplinary and multifaceted perspectives. Additionally, it emphasizes the importance of enhancing research on the compounded pollution effects arising from various pollution modes, particularly in conjunction with other pollutants. This study aims to establish a foundation for assessing the ecological risks posed by MPs in freshwater ecosystem and offers valuable insights for the protection of aquatic biodiversity and ecosystem stability.

Soil Decomposer Can Regulate the Legacy Effect of Photodegradation on Forest Marcescent Litter Decomposition, but Emerging Microplastics Disrupt This

Photodegradation-photochemical mineralization of standing litters-often exerts a legacy effect aiding biodegradation in soil (PLE), which is overlooked in deciduous forests containing marcescent leaves. Meanwhile, increasing anthropogenic microplastics have deposited in forests, how they would affect the PLE on subsequent litter bio-decomposition is currently unknown. Here, we employed an ultraviolet-accelerated aging chamber to replicate the abiotic photodegradation process of a naturally marcescent tree, Lindera glauca, then manipulated mesocosm bio-incubations to quantify how decomposers (microbial alone or with soil animals) and microplastic contamination would interactively affect the PLE. We found abiotic photodegradation significantly decreased litter lignin content before and after the bio-incubation. During an early phase decomposition, lignin lost greatly and displayed a crucial role in determining the ways that soil animal and photodegradation affect the bio-decomposition. Microbial decomposer alone led to a positive PLE universally. Soil animals depressed microbial biomass and inhibited the microbial-mediated PLE in unpolluted mesocosms but intensified the PLE in contaminated soils. We conclude that decomposer interactions can attenuate PLE, but microplastics will disrupt the established equilibrium, making contaminated soil more susceptible to photodegradation-induced litter chemical changes. This promotes integration of radiation and emerging pollution to further our understanding of biogeochemical cycle in forest ecology.

Environmental impact of microplastics and potential health hazards

Microscopic plastic (microplastic) pollutants threaten the earth's biodiversity and ecosystems. As a result of the progressive fragmentation of oversized plastic containers and products or manufacturing in small sizes, microplastics (particles of a diameter of 5 mm with no lower limit) are used in medicines, personal care products, and industry. The incidence of microplastics is found everywhere in the air, marine waters, land, and even food that humans and animals consume. One of the greatest concerns is the permanent damage that is created by plastic waste to our fragile ecosystem. The impossibility of the complete removal of all microplastic contamination from the oceans is one of the principal tasks of our governing body, research scientists, and individuals. Implementing the necessary measures to reduce the levels of plastic consumption is the only way to protect our environment. Cutting off the plastic flow is the key remedy to reducing waste and pollution, and such an approach could show immense significance. This review offers a comprehensive exploration of the various aspects of microplastics, encompassing their composition, types, properties, origins, health risks, and environmental impacts. Furthermore, it delves into strategies for comprehending the dynamics of microplastics within oceanic ecosystems, with a focus on averting their integration into every tier of the food chain.

Form and Function: The Factors That Influence the Efficacy of Nanomaterials for Gene Transfer to Plants

Nanoparticle (NP)-mediated gene delivery offers a promising alternative to traditional methods in plant biotechnology, facilitating genetic transformations with enhanced precision and efficiency. This review discusses key factors influencing NP efficacy, including plant cell wall composition, DNA/NP ratios, exposure time, cargo loading, and post-transformation assessments. We explore the challenges of NP cytotoxicity, transformation efficiency, and regeneration while addressing environmental impacts and regulatory considerations. We emphasize the potential for stimulus-responsive NPs and scalable delivery methods to optimize gene editing in agriculture.

Impact of Polystyrene Microplastics on Soil Properties, Microbial Diversity and Solanum lycopersicum L. Growth in Meadow Soils

The pervasive presence of microplastics (MPs) in agroecosystems poses a significant threat to soil health and plant growth. This study investigates the effects of varying concentrations and sizes of polystyrene microplastics (PS-MPs) on the Solanum lycopersicum L.'s height, dry weight, antioxidant enzyme activities, soil physicochemical properties, and rhizosphere microbial communities. The results showed that the PS0510 treatment significantly increased plant height (93.70 cm, +40.83%) and dry weight (2.98 g, +100%). Additionally, antioxidant enzyme activities improved across treatments for S. lycopersicum L. roots. Physicochemical analyses revealed enhanced soil organic matter and nutrient levels, including ammonium nitrogen, phosphorus, and effective potassium. Using 16S rRNA sequencing and molecular ecological network techniques, we found that PS-MPs altered the structure and function of the rhizosphere microbial community associated with S. lycopersicum L. The PS1005 treatment notably increased microbial diversity and displayed the most complex ecological network, while PS1010 led to reduced network complexity and more negative interactions. Linear discriminant analysis effect size (LEfSe) analysis identified biomarkers at various taxonomic levels, reflecting the impact of PS-MPs on microbial community structure. Mantel tests indicated positive correlations between microbial diversity and soil antioxidant enzyme activity, as well as relationships between soil physicochemical properties and enzyme activity. Predictions of gene function revealed that PS-MP treatments modified carbon and nitrogen cycling pathways, with PS1005 enhancing methanogenesis genes (mcrABG) and PS1010 negatively affecting denitrification genes (nirK, nirS). This study provides evidence of the complex effects of PS-MPs on soil health and agroecosystem functioning, highlighting their potential to alter soil properties and microbial communities, thereby affecting plant growth.