Impact of plastic mulching as a major source of microplastics in agroecosystems

Soil C-N and microbial community were altered by polybutylene adipate terephthalate microplastics

The risks posed by biodegradable plastics to the plant-soil system have been increasingly studied due to potentially hazardous effects on soil properties and nutrient cycling. In this study, we investigated the effects of Poly (butylene adipate-co-terephthalate) microplastics (PBAT-MPs) on soil carbon, nitrogen and microbial communities under different levels of contamination (0 % (control), 0.1 %, 0.2 %, 0.5 % and 1 %), in soils planted with soybean (Glycine max (Linn.) Merr.) and maize (Zea mays L.). The results showed that PBAT-MPs significantly altered soil dissolved organic carbon, dissolved organic nitrogen and nitrate nitrogen contents, and that these effects varied by plant type and growth stage (p < 0.05). PBAT-MPs significantly increased soil microbial biomass carbon and nitrogen for both plants (p < 0.05), except for microbial biomass nitrogen at the soybean flowering stage. PBAT-MPs altered the β-diversity and composition of bacterial and fungal communities, increasing the relative abundances of Proteobacteria but decreasing the relative abundances of Acidobacteriota for both plants. FAPROTAX analysis showed that PBAT-MPs had significant effects on functional bacterial groups related to the nitrogen and carbon cycle, that varied by plant type and growth stage. These results suggest that biodegradable microplastics may have plant-specific effects on soil microbial communities and microbial metabolism, and thereby influence soil carbon and nitrogen cycling.

Unveiling the impact of soil depth on degradation of durable nanocomposite mulch-derived residue migration dynamics in plant ecosystems

The increasing use of biodegradable mulches, such as polylactic acid (PLA), offers a promising approach to tackling plastic waste. However, if PLA is improperly disposed of and degraded uncontrollably, it can negatively impact soil health and plant growth, compromising environmental benefits. This study demonstrates an interaction between hydrophobically modified nanocellulose (CA-CNC(MgSt)), which serves as a plasticizer within a PLA matrix, to create a self-degradable mulch film (PC). Specifically, PC exhibits an impressive toughness of 3.55 MJ·m-3. The use of PC mulch increased soil moisture content, stem length, and leaf area by 31.6 % and 63.2 %, respectively, while maintaining high biosafety. The degradation behavior of PC mulch varied with soil depth (-2, -7, and -14 cm), enhancing soil porosity and lowering pH, which accelerated its degradation and promoted root growth. Additionally, PC degraded faster than pure PLA (kp < kpc), attributed to the preferential hydrolysis of ester bonds. Biodegradable microplastics (BMPs) generated from mulch degradation, including P-BMPs and PC-BMPs, were studied using cherry radish growth models to explore plant-soil-microplastic interactions. This study demonstrates the potential of PC mulch to reduce plastic pollution through effective biodegradation while enhancing the stability of the soil-plant ecosystem. However, comprehensive ecological risk assessments are essential before their large-scale application.

Effortless rule: Effects of oversized microplastic management on lettuce growth and the dynamics of antibiotic resistance genes from fertilization to harvest

The complexity of soil microplastic pollution has driven deeper exploration of waste management strategies to evaluate environmental impact. This study introduced oversized microplastics (OMPs, 1-5 mm) during membrane composting to produce organic fertilizers, and conducted a 2 × 2 pot experiment: exogenous OMPs were added when normal fertilizer (no OMPs intervention) was applied, while artificial removal of OMPs was implemented when contaminated fertilizer (with OMPs) was used. The study assessed the effects of these management strategies on lettuce growth, soil environments, and potential biological safety risks related to the spread and expression of high-risk antibiotic resistance genes (ARGs) in humans. Results showed that both exogenous OMPs addition and removal negatively affected plant height and harvest index, with shifts in the rhizosphere microbial community identified as a key factor rather than soil nutrients. Exogenous OMPs altered rhizosphere and endophytic microbial communities, and plant growth-promoting bacteria were transferred to the surface of OMPs from rhizosphere soil. In contrast, bacteria such as Truepera, Pseudomonas, and Streptomyces in compost-derived OMPs supported lettuce growth, and their removal negated these effects. Some endophytic bacteria may promote growth but pose public health risks when transmitted through the food chain. OMPs in composting or planting significantly enhanced the expression of target ARGs in lettuce, particularly blaTEM. However, simulated digestion results indicated that OMPs reduced the expression of six key ARGs, including blaTEM, among the ten critical target ARGs identified in this context. Notably, the removal management strategies raised five of them posing potential risks from lettuce consumption. This study highlights that both introducing and removing OMPs may pose ecological and food safety risks, emphasizing the need for optimized organic waste management strategies to mitigate potential health hazards.

Effects of mulches on greenhouse gas emissions and soil microbial communities in cabbage production

Agricultural plastic mulches are widely used for their agronomic benefits, but their impact on greenhouse gas (GHG) emissions and soil microbes remains unclear. This study examines the effects of mulching on soil properties, microbial communities, and GHG emissions in cabbage cultivation using four treatments: NF (no mulching), FT (black traditional mulch, 0.015 mm), FBS (black biodegradable mulch, 0.010 mm), and FBB (black biodegradable mulch, 0.015 mm). The results showed no significant differences in cabbage biomass and yield across treatments. However, FT and FBB significantly reduced cumulative CO₂ emissions by 32.07 % and 26.70 %, respectively, compared to NF, while FT increased N₂O emissions and FBB reduced them (p < 0.05). Biodegradable mulch enhanced bacterial network complexity and stability, whereas traditional mulch strengthened fungal network stability. Soil properties, including porosity (19.82 %), NH₄⁺ (18.55 %∼20.19 %), and dissolved organic nitrogen (42.29 %∼85.61 %), improved under biodegradable mulch. Bacterial communities were positively correlated with soil nutrients, while fungal communities showed negative correlations. The reduction in GHG emissions could be attributed to the blocking effect of the mulch during the early stages of crop growth. Partial least squares path modeling analysis revealed that mulching-induced changes in soil hydrothermal conditions can influence soil nutrients and microbial communities, ultimately affecting GHG emissions. These findings offer insights into sustainable agricultural practices that promote soil health and reduce GHG emissions.

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.

Microplastics in Agricultural Soils: Sources, Fate, and Interactions with Other Contaminants

Microplastics (MPs) are recognized as emerging soil contaminants. However, the potential risks of MPs to agroecosystems have not been fully revealed, especially the compound toxic effects of MPs with co-existing organic or inorganic pollutants (OPs/IPs) in agricultural fields. In this study, we quantified the contributions of different agronomic practices to the sources of MPs in soil and highlighted the important influences of long-term tillage and fertilization on the migration and aging of MPs in agricultural fields. In addition, the antagonistic and synergistic interactions between MPs and OPs/IPs in soil were explored. We emphasized that the degree of adsorption of MPs and soil particles to OPs/IPs is a key determinant of the co-toxicity of those contaminants in soil. Finally, several directions for future research are proposed, and these knowledge gaps provide an important basis for understanding the contamination process of MPs in agricultural soils.

Microplastics in agricultural soils: sources, impacts, and mitigation strategies

Plastic particles smaller than 5 mm are known as microplastics, and they are becoming a major ecological and environmental hazard in agricultural soils. These particles come from a variety of sources, such as atmospheric deposition, wastewater irrigation, the breakdown of plastic mulches, and the use of biosolids. Once in the soil, microplastics change the microbial communities, water retention, and soil structure through interactions with physical, chemical, and biological processes. They may worsen soil contamination and possibly introduce harmful substances into the food chain by serving as vectors for organic pollutants and heavy metals. Sustainable agriculture is threatened by the presence of microplastics in agricultural soils, which also endanger crop productivity, ecosystem services, and soil health. Reducing plastic use, switching to biodegradable substitutes, improving waste management procedures, and creating cutting-edge technologies for the removal of microplastics are all examples of mitigation techniques. In order to protect soil health and agricultural sustainability, this review examines the causes, effects, and mitigation techniques of microplastics in agricultural soils, highlighting the necessity of coordinated research and policy interventions.

Studies on the impact of aged microplastics on agricultural soil enzyme activity, lettuce growth, and oxidative stress

Microplastics (MPs) represent an increasingly significant source of pollution, with their ubiquitous presence not only contaminating soil but also influencing plant growth. To elucidate the effects of MPs on soil-plant systems, this study examined the impact of exposure to aged polystyrene (PS), polyethylene, and polylactic acid (PLA) MPs at varying concentrations (0.1%, 1%, 5%, and 10%) on soil physicochemical properties, enzyme activities, lettuce growth, and oxidative stress conditions in a pot experiment. The results indicated that high concentrations (5% and 10%) of PLA increased soil urease activity by 18.27% and 23.57%, respectively, whereas PS reduced it by 12.02% and 27.15%, respectively, compared to the control. High concentrations (5% and 10%) of PLA reduced the fresh weight of lettuce leaves and roots by 58.38-61.08% and 49.20-51.68%, respectively. The addition of all three MPs increased the soluble sugar content in lettuce leaves by 34.10-65.30%. The presence of all three types of MPs significantly enhanced catalase (CAT) and superoxide dismutase (SOD) activities in lettuce leaves at concentrations of 0.1%, 1%, and 5%, with the greatest increase in SOD activity (26.06-31.34%) observed at the 5% concentration. Root CAT activity was elevated at low concentrations (0.1% and 1%), whereas 10% PLA significantly suppressed both CAT and SOD activities. Integrated biomarker response analysis showed that MPs induced oxidative stress in lettuce. The results of this study provide a theoretical basis for evaluating the potential ecological risks posed by MPs to the soil-plant system.

Synergistic effects of magnetic water treatment and mulching on crop and soil moisture-salinity distribution

Freshwater scarcity has increased the reliance on low quality water for irrigation purposes. Brackish and/or high salinity irrigation water may increase soil salinity and reduce yields. This study was carried out for two consecutive seasons to study the effect of magnetic treatment of brackish water and soil mulching on strawberry growth and productivity and soil moisture-salinity distribution. For this purpose, three irrigation water types were used: tap water (W1), brackish water (W2), and magnetically treated brackish water (W3). Four different soil mulches were evaluated: rice straw mulch applied at rate of 3 t ha-1 (M1), rice straw mulch applied at rate of 5 t ha-1 (M2), white polyethylene plastic mulch (M3), and black polyethylene plastic mulch (M4) compared to bare soil (M0). The results revealed that magnetic water treatment (MWT) and soil mulching significantly enhanced crop growth and productivity and improved soil moisture-salinity distribution. The difference between M2 and M4 was not statistically significant in almost all the studied traits in both growing seasons. This result highlights the potential of using rice straw as a sustainable alternative to plastic mulch in strawberry cultivation. Strawberry marketable yield and water productivity increased significantly by 26.7% and 18.6% over the two growing seasons as a result of MWT, compared to untreated water. Moreover, MWT had a positive effect on reducing soil salinization. MWT led to a significant decrease in soil salinity by 17.8% compared to untreated water (W2) and the difference in soil salinity between W1 and W3 was not statistically significant. The integration of MWT and straw mulch at 5 t ha-1 (W3M2) has resulted in marketable yield increase of 32.6 and 40.9% compared to brackish water irrigation and bare soil conditions (W2M0). Hence W3M2 could be adopted as a sustainable management practice for safe use of brackish irrigation water in strawberry cultivation.

Biodegradation of polyethylene with polyethylene-group-degrading enzyme delivered by the engineered Bacillus velezensis

Microplastics (MPs) pose an emerging threat to vegetable growing soils in Harbin, which have a relatively high abundance (11,065 n/kg) with 17.26 of potential ecological risk of single polymer hazard (EI) and 33.92 of potential ecological risk index (PERI). Polyethylene (PE) is the main type of microplastic pollution in vegetable growing soils in Harbin. In this study, the engineered Bacillus velezensis with polyethylene-group-degrading enzyme pathway (BCAv-PEase) was constructed to enhance the degradation of MPs of PE (PE-MPs). BCAv-PEase increased the biodegradation of PE-MPs, promoted weight loss of PE films, elevated surface tension, and decreased the surface hydrophobicity of PE through upregulating activities of depolymerases, dehydrogenase, and catalase. Mechanism analysis showed that BCAv-PEase degraded PE-MPs by promoting the secretion of PEase, thereby leading to the generation of new oxygenated functional groups within the PE-MPs substrate, which further accelerated the metabolic pathway of PE-MPs. The analysis of the microbial community during the PE-MPs degradation processes revealed that BCAv-PEase emerged as the principal bacterial player and stimulated the abundance of microbes and functional genes associated with the biodegradation of PE. In conclusion, this study provides a potential mechanism for biodegradation of PE-MPs mediated by BCAv-PEase via modulating substrate selectivity and optimizing biocatalytic pathways.

Tracking the translocation of nanoplastics from soil to plant: Comparison of different analytical techniques

Nanoplastics (NPs) are increasingly prevalent in the environment, posing potential risks to agricultural systems and the food web. Despite this, currently it lacks comprehensive evaluation on NPs detection and quantification techniques, which is critical for quantitatively understanding the fate and transport of NPs. To address this gap, our study systematically assesses and compares advanced analytical tools for tracking different types of NPs (derived from both top-down and bottom-up approaches) from soil to plants. For identifying and quantifying NPs from environmental samples, pyrolysis - gas chromatography - mass spectrometry (Py-GC-MS) and confocal-Raman spectroscopy demonstrate promise. For laboratory study, inductively coupled plasma mass spectrometry (ICP-MS) along with metal doped NPs enables good sensitivity for tracking NPs in plant system. Our results demonstrated a substantial NPs internalization, 1.09 × 10 ¹ ¹ NPs per gram in shoots and 1.52 × 10 ¹ ¹ NPs per gram in roots, by wheat seedlings after five days of exposure, leading to a notable 77.26 % reduction in biomass. This study highlights the importance of integrating multiple techniques to overcome the limitations of each individual technique and provides quantitative insight into the detection of NPs within plant systems, contributing to the improvement of methodology for NPs related research in environmental and agricultural fields.

Synthetic phenolic antioxidant contamination in farmland soils induced by mulching films: Distribution and transformation pathways

The occurrence and distribution of synthetic phenolic antioxidants (SPAs) originating from mulch film in farmland soils, along with their transformation characteristics and pathways, remain largely unknown. This study is the first to investigate nineteen SPAs and four transformation products (TPs) in farmland soils across China. In film-mulching soils, concentrations of SPAs (median, range: 83.6 ng/g, 20.6-863 ng/g) and TPs (46.4 ng/g, 8.36-489 ng/g) were found significantly higher than in nonfilm-mulching soils, suggesting that mulch film is an important SPA source in farmlands. The ecological risk posed by SPAs was considerable, with estimated risk quotients (RQs) reaching up to 14.7. Furthermore, a laboratory soil incubation experiment was conducted on pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionate) (Ir1010), a typical SPA with high estimated ecological risk (RQs up to 3.01). The half-life of Ir1010 in unsterilized soil was 6.73 days, much shorter than in sterilized soils, suggesting that soil microbes effectively promoted its transformation rate. Importantly, ten TPs of Ir1010 were identified in soil through nontargeted screening using high-resolution mass spectrometry, indicating aromatic epoxidation, hydroxylation, and hydrolysis as transformation pathways. This study firstly reveals the occurrence SPAs and TPs in farmland soils and suggests their transformation mechanism, highlighting the complex risks posed by these emerging agricultural contaminants.

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.

Towards sustainable agroecosystems: A life cycle assessment review of soil-biodegradable and traditional plastic mulch films

The increasing use of traditional agricultural plastic mulch films (PMs) has raised significant environmental concerns, prompting the search for sustainable alternatives. Soil-biodegradable mulch films (BDMs) are often proposed as eco-friendly replacements; however, their widespread adoption remains contentious. This review employs a comparative life cycle assessment perspective to evaluate the environmental impact of PMs and BDMs across their production, use, and end-of-life stages, providing strategies to mitigate their impact on agroecosystems. BDMs generally exhibit lower energy use and greenhouse gas emissions than PMs but contribute to greater land-use demands. Reported eutrophication and acidification potentials are less consistent, varying based on feedstock types and the scope of assessment of BDM, as well as the end-of-life management of PM. The environmental burden of both mulch types is influenced by the life cycle stage, polymer composition, farming practices, additives, film thickness, and local climatic conditions. The manufacturing stage is a major contributor to energy use and greenhouse gas emissions for both PMs and BDMs, despite their shared benefits of increasing crop yields. However, post-use impacts are more pronounced for PMs, driven by end-of-life strategy and adsorbed waste content. While starch-based BDMs offer a more sustainable alternative to PMs, uncertainties regarding the residence time of BDM residues in soil (albeit shorter than PM residues) and their effects on soil health, coupled with higher production costs, impede widespread adoption. For BDM end-of-life, soil biodegradation is recommended. Energy and material recovery options are crucial for PM end-of-life, with mechanical recycling preferred, although it requires addressing eutrophication and human toxicity. This review discusses these complexities within specific contexts and provides actionable insights to guide the sustainable integration of mulch films into agricultural practices.

Assessment of microplastics and associated ecological risk in the longest river (Godavari) of peninsular India: A comprehensive source-to-sink analysis in water, sediment and fish

Persistent microplastics (MPs) accumulation in the aqueous environments is considered a threat to the ecosystem, potentially harming aquatic species and human health. In view of the escalating problem of MPs pollution in India, a comprehensive investigation of MPs accumulation in major riverine systems is necessary. The current study aims to estimate MPs abundance in surface water, sediment, and fish samples along the entire stretch of Godavari, the largest river in peninsular India. Average MPs concentrations in water lie in the range of 311-939 MPs/m3 and 2-144 MPs/kg d.w. for sediment. Urban regions and dam reservoirs showed elevated MPs abundance, emphasizing the impact of anthropogenic activities. The μ-Raman analysis revealed PE and PP were the abundantly occurring polymers in all matrices. Polymer and ecological risk index identify most sampling sites as extremely high-risk zones, posing a potential threat to aquatic ecosystems and human health. Plotted t-SNE (t-distributed Stochastic Neighbour Embedding) revealed similarities in MPs morphology and compositions among water, sediment and fish samples. Examined MPs in edible (flesh+skin) and inedible parts (GIT and gills) of seven different fish species showed a higher average MPs abundance in edible parts (10.7 ± 14.9 MPs/fish) than gills (7 ± 8.1 MPs/fish) and GIT (6.6 ± 5.5 MPs/fish). This suggests that removing gills and GIT from fish doesn't eliminate the consumer's risk of MPs intake. Overall, our work highlights the significant MPs pollution in the Godavari River, further providing essential data on the ecological risk of MPs to guide municipal action plans, improve waste management, target high-risk areas, and raise awareness to mitigate impacts.

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

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

Biodegradable microplastics adsorb more Cd than conventional microplastic and biofilms enhance their adsorption

Biodegradable polylactic acid (PLA) mulch has been developed to replace conventional polyethylene (PE) mulch in agriculture to reduce plastic pollution and the accumulation of microplastics (MPs) in soil. Cadmium (Cd) is a significant soil contaminant, and can be adsorbed by MPs. It is increasingly recognised that in the natural environment biofilms can develop on MPs and that this can affect their adsorption properties. We exposed PLA and PE mulches outdoors for 16 months. MPs were then generated from pristine and weathered mulches. Biofilms developed on the weathered plastics. Oxygen-containing functional groups were detected on the weathered, but not the pristine PE, abundance of these groups increased for the weathered PLA. After removal of the biofilm the observed increases in oxygen-containing functional groups relative to the pristine plastics remained. In adsorption experiments pristine PLA MPs had a greater maximum adsorption capacity than pristine PE MPs (106-126 vs 23.2 mg/kg) despite having a lower specific surface area (0.325 m2/g vs 1.82 m2/g) suggesting that the greater levels of adsorption were due to MP chemistry. The weathered plastics adsorbed more Cd than the pristine plastics (e.g. maximum adsorption capacities of 153-185 and 152 mg/kg for the weathered PLA and PE respectively). However, after removal of the biofilm, adsorption of Cd to the weathered MPs was no greater than for the pristine plastics. This suggests that the increased adsorption of Cd due to weathering was caused primarily by adsorption onto the biofilm.

Polyethylene microplastics distinctly affect soil microbial community and carbon and nitrogen cycling during plant litter decomposition

Plant litter is an important input source of carbon and nitrogen in soil. While microplastics (MPs) and plant litter are ubiquitously present in soil, their combined impact on soil biogeochemical processes remains poorly understood. To address this gap, we examined the soil changes resulting from the coexistence of plant litter (Alfalfa) and polyethylene microplastics (PE). The soil changes included physicochemical properties, composition of soil dissolved organic matter, and structure of the soil microbial community. The results showed that the addition of polyethylene (PE) inhibited the degradation of humus-like substances and decreased the quantity of humic acid-like compounds in soil dissolved organic matter (DOM). PE negatively impacted plant litter decomposition, disrupted soil organic carbon (SOC) breakdown, interfered with the nitrogen cycle, and significantly altered microbial community structures during the process. By day 35, SOC and total nitrogen (TN) levels were reduced by 39.8% and 10.1%, respectively, in the presence of PE. Furthermore, PE significantly decreased the abundance of nitrogen-fixing microbes, including Streptomyces (43.1%) and Bacillus (45.9%), which play key roles in nitrate reduction to ammonium. This study highlights the environmental effects of MPs on plant litter decomposition and their potential implications for soil biogeochemical processes.

Environmental concerns on water-soluble and biodegradable plastics and their applications - A review

Water-soluble polymers are materials rapidly growing in volume and in number of materials and applications. Examples include synthetic plastics such as polyacrylamide, polyacrylic acid, polyethylene glycol, polyethylene oxide and polyvinyl alcohol, with applications ranging from cosmetics and paints to water purification, pharmaceutics and food packaging. Despite their abundance, their environmental concerns (e.g., bioaccumulation, toxicity, and persistence) are still not sufficiently assessed, especially since water soluble plastics are often not biodegradable, due to their chemical structure. This review aims to overview the most important water-soluble and biodegradable polymers, their applications, and their environmental impact. Degradation products from water-insoluble polymers designed for biodegradation can also be water soluble. Most water-soluble plastics are not immediately harmful for humans and the environment, but the degradation products are sometimes more hazardous, e.g. for polyacrylamide. An increased use of water-soluble plastics could also introduce unanticipated environmental hazards. Therefore, excessive use of water-soluble plastics in applications where they can enter the environment should be discouraged. Often the plastics can be omitted or replaced by natural polymers with lower risks. It is recommended to include non-biodegradable water-soluble plastics in regulations for microplastics, to make risk assessments for different water-soluble plastics and to develop labels for flushable materials.

Comprehensive understanding of microplastics in compost: Ecological risks and degradation mechanisms

The introduction of microplastics (MPs) into soil ecosystems via compost application has emerged as a critical environmental concern. However, the ecological risks and degradation behavior of MPs in compost remain insufficiently understood. This review addresses these gaps by synthesizing recent findings on MPs in composting systems, focusing on their sources, impacts on compost quality, ecological risks, and degradation mechanisms. MP sources vary significantly across compost matrices-domestic waste, sludge, and agricultural waste‑leading to differences in their types and quantities. MPs adversely impact compost quality by disrupting its physical structure and impairing fertility, aeration, and water retention. Furthermore, their persistence after compost application can result in long-term environmental accumulation, posing risks to soil ecosystems and biological health. This review also explores the aging and degradation of MPs during composting, a complex process influenced by physical, chemical, and biological mechanisms. Finally, we propose future research directions, emphasizing the development of standardized methodologies to assess MP behavior in compost and strategies to mitigate associated risks. These insights contribute to advancing sustainable waste management and environmental protection practices.

Influence of soil characteristics and agricultural practices on microplastic concentrations in sandy soils and their association with heavy metal contamination

Microplastics (MPs) seriously threaten soil quality and crop health, particularly in agricultural systems using plastic mulch and sewage sludge, with their abundance being strongly influenced by soil properties such as texture, structure, and chemical content. Considering this, the present study assessed MP contamination in arid agricultural soils, focusing on their abundance, morphology, composition, and association with heavy metals to evaluate environmental risks. Soil samples were collected from ten plastic-mulched fields and a control site across a 50 sq. km area. MPs were isolated using density separation and hydrogen peroxide digestion, with morphology categorized through microscopy and polymer composition analysed via FTIR. ICP-OES was used for elemental analysis. Statistical methods, including ANOVA, Pearson's correlation, scatter plots, and PCA, were applied to examine the influence of soil quality on MP levels. Results showed significantly higher MP concentrations in mulched fields (1412 ± 529 particles) compared to the control (72 ± 41 particles), with MPs primarily consisting of fibres, films, fragments, and microbeads. Positive correlations were observed between MPs and soil properties such as clay content, moisture, and organic matter content. FTIR analysis identified eight polymer types, while heavy metals, mainly Fe and Ni, were found to accumulate within MPs. MP counts were positively correlated with mulching duration (r2 = 0.46 to 0.94), indicating increased contamination over time. These findings emphasize the role of soil properties on MP retention and potential risks posed to soil health and environmental sustainability, stressing the need for strategies to mitigate MP contamination in agriculture.

Long-term investigation on the daily variability of microplastic concentration and composition - Monitoring in the effluent of a wastewater treatment plant

The discharge of treated wastewater into receiving waters by wastewater treatment plants (WWTPs) is considered as one of the main pathways for microplastics (MPs) to enter the environment. To gain a better understanding of the temporal variability of MPs in WWTP effluents, this study investigated the concentration and composition (size, shape and polymer type) of MPs in the effluent of a German WWTP over the course of one month. 24-hour mixed samples were collected daily by a custom built automated sampling unit for MPs. Particles and fibers ≥11 μm were analyzed using Fourier transform infrared microspectroscopy. The MP concentration showed large daily fluctuations and ranged between 9.64 103 m-3 and 8.44 104 m-3 MPs over the study period. However, there was no significant correlation between the MP concentration and the precipitation or discharge from the WWTP. In contrast to the MP concentration, the MP composition in terms of size and shape was consistent over the study period. There were strong correlations between the time series of the polymer types polypropylene, polyethylene, polystyrene, polyester, ethylene-vinyl-acetate, cellulose artificially modified as well as the polymer cluster acrylates/polyurethanes/varnish. The time series of polyamide showed no significant correlation with the time series of any other polymer type. This study established a one month long high-resolution time series of MP concentration and composition, and thus provides a valuable basis for future research on the temporal variability of MP inputs into the environment from WWTP effluents.

Macro- and microplastics leachates: Characterization and impact on seed germination

Although plastic mulch enhances crop yield, its removal and disposal present significant challenges, contributing to macro- and microplastic pollution in agricultural soils. The adverse effects of this pollution on soil and plant health are not fully understood but may stem from the plastic particles or the toxicity of leached chemical additives. This study assessed the impact of macro- and microplastics from nondegradable LDPE-based (LDPEb) and biodegradable PBAT-based (PBATb) mulch films, along with their leachates, on the germination of three plant species. After seven days of incubation, PBAT mulch leached compounds that significantly inhibited Arabidopsis germination, while cotton and tomato exhibited notable tolerance. Notably, PBATb mulch released a higher concentration of compounds, whereas LDPEb mulch exhibited a greater diversity of leached chemicals. Microplastic particles alone did not hinder seed germination, indicating that plastic toxicity primarily arises from the leachates. Many of these leached compounds lack global regulation and hazard information, underscoring the urgent need for further investigation into their environmental impacts and the development of appropriate regulatory frameworks to mitigate the potential toxicity of chemicals from conventional and biodegradable mulches.

Microplastic contamination accelerates soil carbon loss through positive priming

The priming effect, i.e., the changes in soil organic matter (SOM) decomposition following fresh organic carbon (C) inputs is known to influence C storage in terrestrial ecosystems. Microplastics (particle size <5 mm) are ubiquitous in soils due to the increasing use and often inadequate end-of-life management of plastics. Conventional polyethylene and bio-degradable (PHBV) plastics contain large amounts of C within their molecular structure, which can be assimilated by microorganisms. However, the extent and direction of the potential priming effect induced by microplastics is unclear. As such, we added 14C-labeled glucose to investigate how background polyethylene and PHBV microplastics (1 %, w/w) affect SOM decomposition and its potential microbial mechanisms in a short-term. The cumulative CO2 emission in soil contaminated with PHBV was 42-53 % higher than under Polyethylene contaminated soil after 60-day incubation. Addition of glucose increased SOM decomposition and induced a positive priming effect, as a consequence, caused a negative net soil C balance (-59 to -132 μg C g-1 soil) regardless of microplastic types. K-strategists dominated in the PHBV-contaminated soils and induced 72 % higher positive priming effects as compared to Polyethylene-contaminated soils (160 vs. 92 μg C g-1 soil). This was attributed to the enhanced decomposition of recalcitrant SOM to acquire nitrogen. The stronger priming effect associated in PHBVs can be attributed to cooperative decomposition among fungi and bacteria, which metabolize more recalcitrant C in PHBV. Moreover, comparatively higher calorespirometric ratios, lower substrate use efficiency, and larger enzyme activity but shorter turnover time of enzymes indicated that soil contaminated with PHBV release more energy, and have a more efficient microbial catabolism and are more efficient in SOM decomposition and nutrient resource uptake. Overall, microplastics, (especially bio-degradable microplastics) can alter biogeochemical cycles with significant negative consequences for C sequestration via increasing SOM decomposition in agricultural soils and for regional and global C budgets.

Microplastics and human health: unveiling the gut microbiome disruption and chronic disease risks

Microplastics (MPs), defined as plastic particles smaller than 5 mm, are increasingly recognized as environmental contaminants with potential health risks. These emerge as breakdown products of larger plastics and are omnipresent in marine, freshwater, and terrestrial ecosystems. They are primarily composed of polymers such as polyethylene, polypropylene, polystyrene, and additives that enhance their performance. MPs also adsorb harmful environmental chemicals like persistent organic pollutants and heavy metals, posing risks to human and environmental health. Human exposure to MPs occurs mainly through ingestion and inhalation, with MPs detected in food products, water, and even the air. MPs have been shown to accumulate in the gastrointestinal tract, disrupting the gut microbiome, and causing dysbiosis-a harmful imbalance between beneficial and harmful bacteria. This disruption has been linked to various health issues, including gastrointestinal disorders, systemic inflammation, and chronic diseases. Furthermore, the gut-brain axis may be affected, with potential neuroinflammatory consequences. As research continues to unravel the health impacts of MP exposure, understanding the mechanisms of accumulation and the broader implications on human health is crucial. This review highlights the effects of MPs on human health, emphasizing their impact on the gut microbiome. We discuss the potential connections between MP exposure and cardiometabolic and inflammatory diseases, and disorders related to the Gut-Brain Axis. By synthesizing the latest research, this work sheds light on the silent yet pervasive threat posed by MPs and underscores the importance of further studies to understand their health impacts fully.

Deciphering the role of nonylphenol adsorption in soil by microplastics with different polarities and ageing processes

In the soil environment, microplastics (MPs) commonly coexist with organic pollutants such as nonylphenol (NP), affecting the migration of NP through adsorption/desorption. However, few studies have focused on the interaction between NP and MPs in soil, especially for MPs of different types and ageing characteristics. In this study, non-polar polypropylene (PP) and polar polyamide (PA) MPs were aged either photochemically (144 h) or within soil (60 days), then used to determine the effect of 5 % MPs on the adsorption behaviour of NP (0.1-4.0 mg/L) in soil. Results showed that both ageing processes significantly promoted the conversion of -CH3 groups to C-O and CO on the surface of PPMPs, while PAMPs exhibited amide groups changes and a reduction in average particle size due to ageing. Additionally, both ageing processes promoted the adsorption of NP by soil containing PPMPs, due to an increase in oxygen-containing functional groups and specific surface area. In contrast, the NP adsorption capacity of soil containing PAMPs decreased by 15.4 % following photochemical ageing due to hydrolysis of amide groups, but increased by 21.15 % after soil ageing due to reorganization of amide groups, respectively. The soil-PAMPs systems exhibited a stronger affinity for NP compared to the soil-PPMPs systems, which was primarily attributed to the dominant role of hydrogen bonding. NP was found to be distributed mainly on soil particles in the soil-PPMPs systems, while it tended to be adsorbed by MPs in the soil-PAMPs systems, especially in the soil aged MPs system. This study provides a comprehensive analysis of the complex effects of MPs on coexisting pollutants in soil environments, highlighting the effect of MP characteristics on the adsorption of organic pollutants, which is essential for understanding the transport behaviour of organic pollutants.

Sources, environmental fate, and impacts of microplastic contamination in agricultural soils: A comprehensive review

The pervasive presence of microplastics has emerged as a pressing global environmental concern, posing threats to food security and human health upon infiltrating agricultural soils. These microplastics primarily originate from agricultural activities, including fertilizer inputs, compost-based soil remediation, irrigation, and atmospheric deposition. Their remarkable durability and resistance to biodegradation contribute to their persistent presence in the environment. Microplastics within agricultural soils have prompted concerns regarding their potential impacts on agricultural practices. Functioning as significant pollutants and carriers of microcontaminants within agricultural ecosystems, microplastics and their accompanying contaminants represent ongoing challenges. Within these soil ecosystems, the fate and transportation of microplastics can detrimentally affect plant growth, microbial communities, and, subsequently, human health via the food chain. Specifically, microplastics interact with soil factors, impacting soil health and functionality. Their high adsorption capacity for hazardous microcontaminants exacerbates soil contamination, leading to increased adverse effects on organisms and human health. Due to their tiny size, microplastic debris is easily ingested by soil organisms and can transfer through the food chain, causing physiological and/or mechanical damage. Additionally, microplastics can affect plant growth and have the potential to accumulate and be transported within plants. Efforts to mitigate these impacts are crucial to safeguarding agricultural sustainability and environmental health. Future research should delve into the long-term impacts of environmental aging processes on microplastic debris within agricultural soil ecosystems from various sources, primarily focusing on food security and human beings.

Global microplastics pollution: a bibliometric analysis and review on research trends and hotspots in agroecosystems

The prevalence of microplastics (MPs) in agricultural ecosystems poses a notable threat to dynamics of soil ecosystems, crop productivity, and global food security. MPs enter agricultural ecosystems from various sources and have considerable impacts on the physiochemical properties soil, soil organisms and microbial communities, and plants. However, the intensity of these impacts can vary with the size, shape, types, and the concentrations of MPs in the soil. Besides, MPs can enter food chain through consummation of crops grown on MPs polluted soils. In this study, we conducted a bibliometric analysis of 1636 publications on the effects of MPs on agricultural ecosystems from 2012 to May 2024. The results revealed a substantial increase in publications over the years, and China, the USA, Germany, and India have emerged as leading countries in this field of research. Social network analysis identified emerging trends and research hotspots. The latest burst keywords were contaminants, biochar, polyethylene microplastics, biodegradable microplastics, antibiotic resistance genes, and quantification. Furthermore, we have summarized the effects of MPs on various components of agricultural ecosystems. By integrating findings from diverse disciplinary perspectives, this study provides a valuable insight into the current knowledge landscape, identifies research gaps, and proposes future research directions to effectively tackle the intricate challenges associated with MPs pollution in agricultural environments.

PLA/PCL/NR ternary blown films with high ductility and thermal shrinkage performance via dynamic vulcanization

The low melt strength and brittleness of polylactic acid (PLA) significantly limit its application in high-performance and functional films. In this study, we successfully prepared ternary thermoplastic vulcanizates (TPVs) comprising of PLA, poly(caprolactone) (PCL) and natural rubber (NR), which exhibit co-continuous structure. During the peroxide-induced dynamic vulcanization process, PLA chains were effectively grafted and anchored to the cross-linked rubber network, thereby enhancing the melt strength of the material. This improvement allowed the ternary TPVs to be continuously and stably blown into films. The films exhibited excellent mechanical properties due to the synergistic effect of ductile PCL and elastic NR. Both the elongation at break and tear strength improved greatly. Interestingly, during the film blowing process, the highly stretched continuous NR crosslinked network stored large amounts of elastic energy, endowing the film with excellent heat shrinkage performance. With 15 phr NR, the heat shrinkage exceeded 35 %, which is sufficient for practical needs. This biodegradable film with heat-shrinkage properties can be processed on a large scale, offering a potential strategy to the urgent issue of plastic film pollution.

A novel strategy of artificially regulating plant rhizosphere microbial community to promote plant tolerance to cold stress

Artificial regulation of plant rhizosphere microbial communities through the synthesis of microbial communities is one of the effective ways to improve plant stress resistance. However, the process of synthesizing stress resistant microbial communities with excellent performance is complex, time-consuming, and costly. To address this issue, we proposed a novel strategy for preparing functional microbial communities. We isolated a cultivable cold tolerant bacterial community (PRCBC) from the rhizosphere of peas, and studied its effectiveness in assisting rice to resist stress. The results indicate that PRCBC can not only improve the ability of rice to resist cold stress, but also promote the increase of rice yield after cold stress relieved. This is partly because PRCBC increases the nitrogen content in the rhizosphere soil, and promotes rice's absorption of nitrogen elements, thereby promoting rice growth and enhancing its ability to resist osmotic stress. More importantly, the application of PRCBC drives the succession of rice rhizosphere microbial communities, and promotes the succession of rice rhizosphere microbial communities towards stress resistance. Surprisingly, PRCBC drives the succession of rice rhizosphere microbial communities towards a composition similar to PRCBC. This provides a feasible novel method for artificially and directionally driving microbial succession. In summary, we not only proposed a novel and efficient strategy for preparing stress resistant microbial communities to promote plant stress resistance, but also unexpectedly discovered a possible directionally driving method for soil microbial community succession.

Global perspective of ecological risk of plastic pollution on soil microbial communities

Introduction

The impacts of plastic pollution on soil ecosystems have emerged as a significant global environmental concern. The progress in understanding how plastic pollution affects soil microbial communities and ecological functions is essential for addressing this issue effectively.

Methods

A bibliometric analysis was conducted on the literature from the Web of Science Core Collection database to offer valuable insights into the dynamics and trends in this field.

Results

To date, the effects of plastic residues on soil enzymatic activities, microbial biomass, respiration rate, community diversity and functions have been examined, whereas the effects of plastic pollution on soil microbes are still controversial.

Discussion

To include a comprehensive examination of the combined effects of plastic residue properties (Type, element composition, size and age), soil properties (soil texture, pH) at environmentally relevant concentrations with various exposure durations under field conditions in future studies is crucial for a holistic understanding of the impact of plastic pollution on soil ecosystems. Risk assessment of plastic pollution, particularly for nanoplasctics, from the perspective of soil food web and ecosystem multifunctioning is also needed. By addressing critical knowledge gaps, scholars can play a pivotal role in developing strategies to mitigate the ecological risks posed by plastic pollution on soil microorganisms.

Micro plastic driving changes in the soil microbes and lettuce growth under the influence of heavy metals contaminated soil

Microplastics (MPs) have garnered global attention as emerging contaminants due to their adaptability, durability, and robustness in various ecosystems. Still, studies concerning their combination with heavy metals (HMs), their interactions with soil biota, and how they affect soil physiochemical properties and terrestrial plant systems are limited. Our study was set to investigate the combined effect of HMs (cadmium, arsenic, copper, zinc and lead) contaminated soil of Tongling and different sizes (T1 = 106 µm, T2 = 50 µm, and T3 = 13 µm) of polystyrene microplastics on the soil physiochemical attributes, both bacterial and fungal diversity, compositions, AMF (arbuscular mycorrhizal fungi), plant pathogens in the soil, and their effect on Lactuca sativa by conducting a greenhouse experiment. According to our results, the combination of HMs and polystyrene microplastic (PS-MPs), especially the smaller PS-MPs (T3), was more lethal for the lettuce growth, microbes and soil. The toxicity of combined contaminants directly reduced the physio-biochemical attributes of lettuce, altered the lettuce's antioxidant activity and soil health. T3 at the final point led to a significant increase in bacterial and fungal diversity. In contrast, overall bacterial diversity was higher in the rhizosphere, and fungal diversity was higher in the bulk soil. Moreover, the decrease in MPs size played an important role in decreasing AMF and increasing both bacterial and fungal pathogens, especially in the rhizosphere soil. Functional prediction was found to be significantly different in the control treatment, with larger MPs compared to smaller PS-MPs. Environmental factors also played an important role in the alteration of the microbial community. This study also demonstrated that the varied distribution of microbial populations could be an ecological indicator for tracking the environmental health of soil. Overall, our work showed that the combination of HMs and smaller sizes of MPs was more lethal for the soil biota and lettuce and also raised many questions for further studying the ecological risk of PS-MPs and HMs.

Microplastics and metals: Microplastics generated from biodegradable polylactic acid mulch reduce bioaccumulation of cadmium in earthworms compared to those generated from polyethylene

Biodegradable polylactic acid (PLA) mulch has been developed to replace conventional polyethylene (PE) mulch in agriculture as a response to growing concerns about recalcitrant plastic pollution and the accumulation of microplastics (MPs) in soil. Cadmium is a significant soil pollutant in China. MPs have been shown to adsorb metals. In this study the earthworm Lumbricus terrestris was exposed to either Cd (1.0-100 mg / kg) or MPs (PE and PLA, 0.1-3 % w / w), or a combination of the two, for 28 days. Cd bioavailability significantly decreased in the presence of MPs. In particular, at the end of the experiment, PLA treatments had lower measured Cd concentrations in both earthworms (2.127-29.24 mg / kg) and pore water (below detection limits - 0.1384 mg /L) relative to PE treatments (2.720-33.77 mg / kg and below detection limits - 0.2489 mg / L). In our adsorption experiment PLA MPs adsorbed significantly more Cd than PE MPs with maximum adsorption capacities of 126.0 and 23.2 mg / kg respectively. These results suggest that the PLA MPs reduce earthworm exposure to Cd relative to PE by removing it from solution and reducing its bioavailability.

Exposure to polyethylene microplastics exacerbate inflammatory bowel disease tightly associated with intestinal gut microflora

Polyethylene microplastics (PE MPs) have sparked widespread concern about their possible health implications because of their abundance, pervasiveness in the environment and in our daily life. Multiple investigations have shown that a high dosage of PE MPs may adversely impact gastrointestinal health. In tandem with the rising prevalence of Inflammatory bowel disease (IBD) in recent decades, global plastic manufacturing has risen to more than 300 million tons per year, resulting in a build-up of plastic by-products such as PE MPs in our surroundings. We have explored current advancements in the effect PE MPs on IBD in this review. Furthermore, we compared and summarized the detrimental roles of PE MPs in gut microbiota of different organisms viz., earthworms, super worm's larvae, yellow mealworms, brine shrimp, spring tails, tilapia, gilt-head bream, crucian carp, zebrafish, juvenile yellow perch, European sea bass, c57BL/6 mice and human. According to this review, PE MPs played a significant role in decreasing the diversity of gut microbiota of above-mentioned species which leads to the development of IBD and causes severe intestinal inflammation. Finally, we pinpoint significant scientific gaps, such as the movement of such hazardous PE MPs and the accompanying microbial ecosystems and propose prospective research directions.

Deficit irrigation of reclaimed water relieves oat drought stress while controlling the risk of PAEs pollution in microplastics-polluted soil

Reclaimed water irrigation has emerged as a critical alternative in agricultural regions facing water scarcity. However, soil pollution with microplastics (MPs) greatly increases the exposure risk and toxic effects of reclaimed water contaminations, such as phthalate esters (PAEs). A field experiment consisting of soil column pots evaluated the feasibility of using PAEs-contaminated water to irrigate oats (Avena sativa L.) in drought seasons. Three irrigation regimens based on soil matric potential thresholds (-10 kPa, -30 kPa, -50 kPa) explored the impact of PAE-contaminated water on oat physiology and environmental pollution in soil with and without MPs contamination. The results showed that treating oats at the SMP of -30 kPa boosted shoot biomass by 3.1%-14.0% compared to the drought condition at -50 kPa, and the root biomass of oats was significantly increased. The physiological metrics of oats indicated that irrigation at -50 kPa induced drought stress and oxidative damage in oats, particularly during the milk stage. Different irrigation treatments influenced the accumulation of PAEs in plants, soil, and leachate. The ratios of leachate to irrigation water in -10 kPa treatment with and without MPs addition were 1.18% and 4.48%, respectively, which aggravated the accumulation of pollutants in deep soil layers and may cause groundwater pollution. MPs pollution in soil increased the content of PAEs in the harvested oats and reduced the transport and accumulation of PAEs in deep soil layers (20-50 cm) and leachate. The coupling of PAEs in irrigation water with soil MPs pollution may exacerbate plant damage. However, the damage can be minimized under the scheduled irrigation at -30 kPa which could balance crop yield and potential risks.

Microplastics in agroecosystems: Soil-plant dynamics and effective remediation approaches

Increasing microplastic (MP) pollution, primarily from anthropogenic sources such as plastic film mulching, waste degradation, and agricultural practices, has emerged as a pressing global environmental concern. This review examines the direct and indirect effects of MPs on crops, both in isolation and in conjunction with other contaminants, to elucidate their combined toxicological impacts. Organic fertilizers predominantly contain 78.6% blue, 9.5% black, and 8.3% red MPs, while irrigation water in agroecosystems contains 66.2% white, 15.4% blue, and 8.1% black MPs, ranging from 0-1 mm to 4-5 mm in size. We elucidate five pivotal insights: Firstly, soil MPs exhibit affinity towards crop roots, seeds, and vascular systems, impeding water and nutrient uptake. Secondly, MPs induce oxidative stress in crops, disrupting vital metabolic processes. Thirdly, leachates from MPs elicit cytotoxic and genotoxic responses in crops. Fourthly, MPs disrupt soil biotic and abiotic dynamics, influencing water and nutrient availability for crops. Lastly, the cumulative effects of MPs and co-existing contaminants in agricultural soils detrimentally affect crop yield. Thus, we advocate agronomic interventions as practical remedies. These include biochar input, application of growth regulators, substitution of plastic mulch with crop residues, promotion of biological degradation, and encouragement of crop diversification. However, the efficacy of these measures varies based on MP type and dosage. As MP volumes increase, exploring alternative mitigation strategies such as bio-based plastics and environmentally friendly biotechnological solutions is imperative. Recognizing the persistence of plastics, policymakers should enact legislation favoring the mitigation and substitution of non-degradable materials with bio-derived or compostable alternatives. This review demonstrates the urgent need for collective efforts to alleviate MP pollution and emphasizes sustainable interventions for agricultural ecosystems.

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.

Bayesian multivariate receptor model and convolutional neural network to identify quantitative sources and spatial distributions of potentially toxic elements in soils: A case study in Qingzhou City, China

Determining sources and spatial distributions of potentially toxic elements (PTEs) is a crucial issue of soil pollution survey. However, uncertainty estimation for source contributions remains lack, and accurate spatial prediction is still challenging. Robust Bayesian multivariate receptor model (RBMRM) was applied to the soil dataset of Qingzhou City (8 PTEs in 429 samples), to calculate source contributions with uncertainties. Multi-task convolutional neural network (MTCNN) was proposed to predict spatial distributions of soil PTEs. RBMRM afforded three sources, consistent with US-EPA positive matrix factorization. Natural source dominated As, Cr, Cu, and Ni contents (78.5 %∼86.1 %), and contributed 37.1 %, 61.0 %, and 65.9 % of Cd, Pb, and Zn, exhibiting low uncertainties with uncertainty index (UI) < 26.7 %. Industrial, traffic, and agricultural sources had significant influences on Cd, Pb, and Zn (30.2 %∼61.9 %), with UI < 39.3 %. Hg originated dominantly from atmosphere deposition (99.1 %), with relatively high uncertainties (UI=87.7 %). MTCNN acquired satisfactory accuracies, with R2 of 0.357-0.896 and nRMSE of 0.092-0.366. Spatial distributions of As, Cd, Cr, Cu, Ni, Pb, and Zn were influenced by parent materials. Cd, Hg, Pb, and Zn showed significant hotspot in urban area. This work conducted a new approach exploration, and practical implications for soil pollution regulation were proposed.

Microplastics supply contaminants in food chain: non-negligible threat to health safety

The occurrence of microplastics (MPs) and organic pollutants (OPs) residues is commonly observed in diverse environmental settings, where their interactions can potentially alter the behavior, availability, and toxicity of OPs, thereby posing risks to ecosystems. Herein, we particularly emphasize the potential for bioaccumulation and the biomagnification effect of MPs in the presence of OPs within the food chain. Despite the ongoing influx of novel information, there exists a dearth of data concerning the destiny and consequences of MPs in the context of food pollution. Further endeavors are imperative to unravel the destiny and repercussions of MPs/OPs within food ecosystems and processing procedures, aiming to gain a deeper understanding of the joint effect on human health and food quality. Nevertheless, the adsorption and desorption behavior of coexisting pollutants can be significantly influenced by MPs forming biofilms within real-world environments, including temperature, pH, and food constituents. A considerable portion of MPs tend to accumulate in the epidermis of vegetables and fruits, thus necessitating further research to comprehend the potential ramifications of MPs on the infiltration behavior of OPs on agricultural product surfaces.

Mitigating microplastic stress on peanuts: The role of biochar-based synthetic community in the preservation of soil physicochemical properties and microbial diversity

Tire-derived rubber crumbs (RC), as a new type of microplastics (MPs), harms both the environment and human health. Excessive use of plastic, the decomposition of which generates microplastic particles, in current agricultural practices poses a significant threat to the sustainability of agricultural ecosystems, worldwide food security and human health. In this study, the application of biochar, a carbon-rich material, to soil was explored, especially in the evaluation of synthetic biochar-based community (SynCom) to alleviate RC-MP-induced stress on plant growth and soil physicochemical properties and soil microbial communities in peanuts. The results revealed that RC-MPs significantly reduced peanut shoot dry weight, root vigor, nodule quantity, plant enzyme activity, soil urease and dehydrogenase activity, as well as soil available potassium, and bacterial abundance. Moreover, the study led to the identification highly effective plant growth-promoting rhizobacteria (PGPR) from the peanut rhizosphere, which were then integrated into a SynCom and immobilized within biochar. Application of biochar-based SynCom in RC-MPs contaminated soil significantly increased peanut biomass, root vigor, nodule number, and antioxidant enzyme activity, alongside enhancing soil enzyme activity and rhizosphere bacterial abundance. Interestingly, under high-dose RC-MPs treatment, the relative abundance of rhizosphere bacteria decreased significantly, but their diversity increased significantly and exhibited distinct clustering phenomenon. In summary, the investigated biochar-based SynCom proved to be a potential soil amendment to mitigate the deleterious effects of RC-MPs on peanuts and preserve soil microbial functionality. This presents a promising solution to the challenges posed by contaminated soil, offering new avenues for remediation.

Microplastic accumulation in groundwater: Data-scaled insights and future research

Given that microplastics (MPs) in groundwater have been concerned for risks to humans and ecosystems with increased publications, a Contrasting Analysis of Scales (CAS) approach is developed by this study to synthesize all existing data into a hierarchical understanding of MP accumulation in groundwater. Within the full data of 386 compiled samples, the median abundance of MPs in Open Groundwater (OG) and Closed Groundwater (CG) were 4.4 and 2.5 items/L respectively, with OG exhibiting a greater diversity of MP colors and larger particle sizes. The different pathways of MP entry (i.e., surface runoff and rock interstices) into OG and CG led to this difference. At the regional scale, median MP abundance in nature reserves and landfills were 17.5 and 13.4 items/L, respectively, all the sampling points showed high pollution load risk. MPs in agricultural areas exhibited a high coefficient of variation (716.7%), and a median abundance of 1.0 items/L. Anthropogenic activities at the regional scale are the drivers behind the differentiation in the morphological characteristics of MPs, where groundwater in residential areas with highly toxic polymers (e.g., polyvinylchloride) deserves prolonged attention. At the local scale, the transport of MPs is controlled by groundwater flow paths, with a higher abundance of MP particles downstream than upstream, and MPs with regular surfaces and lower resistance (e.g., pellets) are more likely to be transported over long distances. From the data-scaled insight this study provides on the accumulation of MPs, future research should be directed towards network-based observation for groundwater-rich regions covered with landfills, residences, and agricultural land.

Exploring the potential of earthworm gut bacteria for plastic degradation

The use of plastic mulch films in agriculture leads to the inevitable accumulation of plastic debris in soils. Here, we explored the potential of earthworm gut-inhabiting bacterial strains (Mycobacterium vanbaalenii (MV), Rhodococcus jostii (RJ), Streptomyces fulvissimus (SF), Bacillus simplex (BS), and Sporosarcina globispora (SG) to degrade plastic films (⌀ = 15 mm) made from commonly used polymers: low-density polyethylene film (LDPE-f), polylactic acid (PLA-f), polybutylene adipate terephthalate film (PBAT-f), and a commercial biodegradable mulch film, Bionov-B® (composed of Mater-Bi, a feedstock with PBAT, PLA and other chemical compounds). A 180-day experiment was conducted at room temperature (x̄ =19.4 °C) for different strain-plastic combinations under a low carbon media (0.1× tryptic soy broth). Results showed that the tested strain-plastic combinations did not facilitate the degradation of LDPE-f (treated with RJ and SF), PBAT-f (treated with BS and SG), and Bionov-B (treated with BS, MV, and SG). However, incubating PLA-f with SF triggered a reduction in the molecular weights and an increase in crystallinity. Therefore, we used PLA-f as model plastic to study the influence of temperature ("room temperature" & "30 °C"), carbon source ("carbon-free" & "low carbon supply"), and strain interactions ("single strains" & "strain mixtures") on PLA degradation. SF and SF + RJ treatments significantly fostered PLA degradation under 30 °C in a low-carbon media. PLA-f did not show any degradation in carbon-free media treatments. The competition between different strains in the same system likely hindered the performance of PLA-degrading strains. A positive correlation between the final pH of culture media and PLA-f weight loss was observed, which might reflect the pH-dependent hydrolysis mechanism of PLA. Our results situate SF and its co-culture with RJ strains as possible accelerators of PLA degradation in temperatures below PLA glass transition temperature (Tg). Further studies are needed to test the bioremediation feasibility in soils.

Study on the photoaging process and metal ion release of plastic films with two kinds of structures in marine environment: Aliphatic and aromatic polymers

The prevalence of plastics in the oceans has significantly intensified microplastic pollution, contributing to broader marine secondary pollution issues. This paper examines how plastic structure affects the aging characteristics of plastics and the release of metal ions, to better understand this secondary source of marine pollution. This study simulate the photoaging of plastics in natural environments, focusing on aliphatic and aromatic polymers. The results showed that the photodegradation degree was higher for aliphatic than aromatic polymers. All polymers contained thirteen detectable metals, with their release increasing over time due to photoaging, The release dynamics of these metal ions correlated more strongly with the level of polymer degradation rather than with the polymer structure itself, adhering to a second-order kinetic model driven by surface and intraparticle diffusion processes. The results will help control and treat marine plastic pollution.

Unveiling the detrimental effects of polylactic acid microplastics on rice seedlings and soil health

The environmental impact of biodegradable polylactic acid microplastics (PLA-MPs) has become a global concern, with documented effects on soil health, nutrient cycling, water retention, and crop growth. This study aimed to assess the repercussions of varying concentrations of PLA-MPs on rice, encompassing aspects such as growth, physiology, and biochemistry. Additionally, the investigation delved into the influence of PLA-MPs on soil bacterial composition and soil enzyme activities. The results illustrated that the highest levels of PLA-MPs (2.5%) impaired the photosynthesis activity of rice plants and hampered plant growth. Plants exposed to the highest concentration of PLA-MPs (2.5%) displayed a significant reduction of 51.3% and 47.7% in their root and shoot dry weights, as well as a reduction of 53% and 49% in chlorophyll a and b contents, respectively. The activities of catalase (CAT), superoxide dismutase (SOD), peroxidase (POD), and ascorbate peroxidase (APX) in rice leaves increased by 3.1, 2.8, 3.5, and 5.2 folds, respectively, with the highest level of PLA-MPs (2.5%). Soil enzyme activities, such as CAT, urease, and dehydrogenase (DHA) increased by 19.2%, 10.4%, and 22.5%, respectively, in response to the highest level of PLA-MPs (2.5%) application. In addition, PLA-MPs (2.5%) resulted in a remarkable increase in the relative abundance of soil Proteobacteria, Nitrospirae, and Firmicutes by 60%, 31%, and 98.2%, respectively. These findings highlight the potential adverse effects of PLA-MPs on crops and soils. This study provides valuable insights into soil-rice interactions, environmental risks, and biodegradable plastic regulation, underscoring the need for further research.

Possible hazards from biodegradation of soil plastic mulch: Increases in microplastics and CO2 emissions

Biodegradable mulches are widely recognized as ecologically friendly substances. However, their degradation percentage upon entering soils may vary based on mulch type and soil microbial activities, raising concerns about potential increases in microplastics (MPs). The effects of using different types of mulch on soil carbon pools and its potential to accelerate their depletion have not yet well understood. Therefore, we conducted an 18-month experiment to investigate mulch biodegradation and its effects on CO2 emissions. The experiment included burying soil with biodegradable mulch made of polylactic acid (PLA) and polybutylene adipate terephthalate (PBAT), and control treatments with traditional mulch (PE) and no mulch (CK). The results indicated that PE did not degrade, and the degradation percentage of PLA and PBAT were 46.2% and 88.1%, and the MPs produced by the degradation were 6.7 × 104 and 37.2 × 104 items/m2, respectively. Biodegradable mulch, particularly PLA, can enhance soil microbial diversity and foster more intricate bacterial communities compared to PE. The CO2 emissions were 0.58, 0.74, 0.99, and 0.86 g C/kg in CK, PE, PLA, , PBAT, respectively. A positive correlation was observed between microbial abundance and diversity with CO2 emissions, while a negative correlation was observed with soil total organic carbon. Biodegradable mulch enhanced the transformation of soil organic C into CO2 by stimulating microbial activity.

Plastics in the environment in the context of UV radiation, climate change and the Montreal Protocol: UNEP Environmental Effects Assessment Panel, Update 2023

This Assessment Update by the Environmental Effects Assessment Panel (EEAP) of the United Nations Environment Programme (UNEP) considers the interactive effects of solar UV radiation, global warming, and other weathering factors on plastics. The Assessment illustrates the significance of solar UV radiation in decreasing the durability of plastic materials, degradation of plastic debris, formation of micro- and nanoplastic particles and accompanying leaching of potential toxic compounds. Micro- and nanoplastics have been found in all ecosystems, the atmosphere, and in humans. While the potential biological risks are not yet well-established, the widespread and increasing occurrence of plastic pollution is reason for continuing research and monitoring. Plastic debris persists after its intended life in soils, water bodies and the atmosphere as well as in living organisms. To counteract accumulation of plastics in the environment, the lifetime of novel plastics or plastic alternatives should better match the functional life of products, with eventual breakdown releasing harmless substances to the environment.

The characteristics and influencing factors of farmland soil microplastic in Hetao Irrigation District, China

Microplastic pollution, a major global concern, has garnered increasing attention in agricultural ecosystem research. China's Hetao Irrigation District, vital for grain production in the Yellow River Basin, lacks sufficient research on microplastic pollution of agricultural soils. This study, based on a detailed background investigation and testing of 47 samples, is the first to elucidate the characteristics and potential influencing factors of microplastics in the Hetao Irrigation District. The abundance of microplastics in the farmland soil ranged from 1810 to 86331 items/kg, with 90% measuring below 180 µm and mainly in film and fragment forms. Predominant polymers were polyethylene (PE, 43.0%) and polyamide (PA, 27.8%). Key pollution influencers were identified as agricultural inputs, with low-density polyethylene (LDPE) being the most extensively used plastic type. The carbonyl index and hydroxyl indices of the detected LDPE microplastics ranged from 0.041 to 0.96 and 0.092 to 1.20, respectively. The study highlights the significance of mulching management and agronomic practices in shaping microplastic characteristics. Potential pollution sources include agricultural inputs, irrigation equipment, domestic waste, and tire wear. Proposed effective strategies include responsible plastic use, robust waste management, and irrigation system upgrades, establishing a foundation for future ecological risk assessments and effective management approaches in the Hetao Irrigation District. ENVIRONMENTAL IMPLICATION: The harmful substances studied in this paper are microplastics, which are widely distributed in the environment and have potential ecological risks. This study is the first to investigate the characteristics of microplastics in farmland soil within the Hetao Irrigation Area, a region that is of critical importance to agricultural production in the Yellow River Basin of China. The study provides comprehensive insights into the factors influencing the characteristics of microplastics and speculates on their sources. These findings offer a novel perspective on the assessment of microplastic contamination in the area and provide valuable recommendations for prevention and control measures.

Phosphorus fertiliser application mitigates the negative effects of microplastic on soil microbes and rice growth

Soil microplastics (MPs) have attracted widespread attention recently. Most studies have explored how soil MPs affect the soil's physicochemical parameters, matter circulation, and soil microbial community assembly. Similarly, a key concern in agricultural development has been the use of phosphorus (P) fertiliser, which is essential for plant health and development. However, the relationship between MPs and phosphate fertilisers and their effects on the soil environment and plant growth remains elusive. This study assessed the influence of adding low-density polyethylene MPs (1%) with different phosphate fertiliser application rates on microbial communities and rice biomass. Our results showed that MPs changed the structure of soil bacterial and phoD-harbouring microbial communities in the treatment with P fertiliser at the same level and suppressed the interactions of phoD-harbouring microorganisms. In addition, we found that MPs contamination inhibited rice growth; however, the inclusion of P fertiliser in MP-contaminated soils reduced the inhibitory action of MPs on rice growth, probably because the presence with P fertiliser promoted the uptake of NO3--N by rice in MP-contaminated soils. Our results provide further insights into guiding agricultural production, improving agricultural management, and rationally applying phosphate fertilisers in the context of widespread MPs pollution and global P resource constraints.

A global review on the abundance and threats of microplastics in soils to terrestrial ecosystem and human health

Soil is the source and sink of microplastics (MPs), which is more polluted than water and air. In this paper, the pollution levels of MPs in the agriculture, roadside, urban and landfill soils were reviewed, and the influence of MPs on soil ecosystem, including soil properties, microorganisms, animals and plants, was discussed. According to the results of in vivo and in vitro experiments, the possible risks of MPs to soil ecosystem and human health were predicted. Finally, in light of the current status of MPs research, several prospects are provided for future research directions to better evaluate the ecological risk and human health risk of MPs. MPs concentrations in global agricultural soils, roadside soils, urban soils and landfill soils had a great variance in different studies and locations. The participation of MPs has an impact on all aspects of terrestrial ecosystems. For soil properties, pH value, bulk density, pore space and evapotranspiration can be changed by MPs. For microorganisms, MPs can alter the diversity and abundance of microbiome, and different MPs have different effects on bacteria and fungi differently. For plants, MPs may interfere with their biochemical and physiological conditions and produce a wide range of toxic effects, such as inhibiting plant growth, delaying or reducing seed germination, reducing biological and fruit yield, and interfering with photosynthesis. For soil animals, MPs can affect their mobility, growth rate and reproductive capacity. At present epidemiological evidences regarding MPs exposure and negative human health effects are unavailable, but in vitro and in vivo data suggest that they pose various threats to human health, including respiratory system, digestive system, urinary system, endocrine system, nervous system, and circulation system. In conclusion, the existence and danger of MPs cannot be ignored and requires a global effort.

Microplastic interactions in the agroecosystems: methodological advances and limitations in quantifying microplastics from agricultural soil

The instantaneous growth of the world population is intensifying the pressure on the agricultural sector. On the other hand, the critical climate changes and increasing load of pollutants in the soil are imposing formidable challenges on agroecosystems, affecting productivity and quality of the crops. Microplastics are among the most prevalent pollutants that have already invaded all terrestrial and aquatic zones. The increasing microplastic concentration in soil critically impacts crop plants growth and yield. The current review elaborates on the behaviors of microplastics in soil and their impact on soil quality and plant growth. The study shows that microplastics alter the soil's biophysical properties, including water-holding capacity, bulk density, aeration, texture, and microbial composition. In addition, microplastics interact with multiple pollutants, such as polyaromatic hydrocarbons and heavy metals, making them more bioavailable to crop plants. The study also provides a detailed insight into the current techniques available for the isolation and identification of soil microplastics, providing solutions to some of the critical challenges faced and highlighting the research gaps. In our study, we have taken a holistic, comprehensive approach by analysing and comparing various interconnected aspects to provide a deeper understanding of all research perspectives on microplastics in agroecosystems.