Impact of microplastics on bioaccumulation of heavy metals in rape (Brassica napus L.)

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.

Effects of polyethylene microplastics on cadmium accumulation in Solanum nigrum L.: A study involving microbial communities and metabolomics profiles

Combined pollution with heavy metals and microplastics (MPs) is widespread in farmland soil, and MPs can affect the efficiency and capacity of cadmium (Cd) uptake by hyperaccumulators. However, there is a significant knowledge gap regarding the response of hyperaccumulators under such conditions. This study utilized Solanum nigrum L. (S. nigrum), a well-known Cd hyperaccumulator, to investigate the combined effects of polyethylene microplastics (PE-MPs) and Cd contamination on Cd accumulation in S. nigrum, and to systematically explore the underlying mechanisms. The results demonstrated that high doses of PE-MPs significantly inhibited S. nigrum growth and reduced Cd concentration and accumulation in plants. Meanwhile, the decrement of bioavailable Cd content and the formation of C-H and -COO in rhizosphere soil were observed with the presence of PE-MPs. The simultaneous exposure of PE-MPs and Cd caused the significant increase in the proportions of Proteobacteria and Acidobacteriota, indicating that certain PE-degrading microorganisms may play a pivotal role in aforementioned processes. More importantly, the relative abundance of the genera Pseudolabrys, DEV008, and Flavobacterium was significantly elevated, likely contributing to the response of S. nigrum to combined toxicity. Co-exposure caused a significant downregulation of biosynthetic processes, involving carbohydrates and adenosine. Additionally, the biosynthesis of ABC transporters, phenylpropanoids, flavonoids, and organic acids was also significantly affected. The findings provide a comprehensive understanding of the soil-plants ecosystem under combined pollution and provide valuable information for advancing phytoremediation strategies.

Microplastics change the safe production ability of arsenic-stressed rice (Oryza sativa L.) by regulating the antioxidant capacity, arsenic absorption, and distribution in rice

Microplastics (MPs) and arsenic (As) are pervasive pollutants in agricultural soils, drawing increasing attention due to their combined toxicity. While biodegradable plastics offer a potential alternative to conventional plastics, their interactions with As and subsequent effects on edible crops remain largely unexplored. Here, we investigated the combined effect of polyethylene (PE) and polylactic acid (PLA) microplastics with As on rice growth, As accumulation, and rhizosphere microbial communities in two rice genotypes. The results showed that As-PE exposure was more detrimental to rice growth than As alone, leading to biomass reductions of 21.1-39.8% in 2A roots, 32.6-54.6% in stems, and 21.9-32.7% in leaves. In contrast, PLA mitigated As-induced growth inhibition in 2119, increasing leaf biomass by 56.1-71.9% and stem biomass by 45.6-57.9%. The presence of MPs intensified As toxicity and induced oxidative stress, with the low-As-accumulating genotype exhibiting stronger detoxification mechanisms, including enhanced sequestration of As in the leaf cell wall and MPs facilitated As adsorption and desorption in the root zone, exacerbating As accumulation in the aerial part of rice, particularly during grain filling. Different degradation characteristics of MPs altered microbial composition and function, impacting rhizosphere iron plaque formation and As availability in soil. PLA decreased the As content in 2A and 2119 roots by 6.1% and 24.0%, respectively, whereas PE increased by 10.6% and 12.9%. This study provides new insights into the comprehensive toxicity of As and MPs in the soil-plant system, highlighting their effects on As uptake and accumulation in rice.

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.

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.

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).

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

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

Uptake, growth, and oxidative stress responses of Rhizophora mucronata (Poir. in Lam.) propagules exposed to high-density polyethylene microplastics

The plastic revolution's contribution to global pollution gives rise to microplastics (MPs), bearing a toll on the marine environment. Knowledge of mangrove exposure to MPs causing adverse effects has yet to be elucidated. Hence, the physiological responses of R. mucronata propagules exposed to ubiquitous High-Density Polyethylene Microplastics (HDPE-MPs) were investigated. The set-up consists of a control (0 mg/L) and an environmentally relevant treatment group (32.65 mg/L), acclimatized and exposed for three months. Scanning Electron Microscopy (SEM) shows agglomeration of HDPE-MPs on root surfaces and translocation to the shoot system of smaller MPs (< 50 μm). Attenuated Total Reflectance Fourier Transform-Infrared Spectroscopy (ATR FT-IR) confirmed uptake in the roots. Root length, count, plant height, foliar area, and oxidative stress biomarkers (carbonyl protein and total chlorophyll) all show significant differences (p < 0.05). Indeed, plastic pollution has detrimental effects on mangroves that may consequently affect mangrove forest diversity and productivity.

Microplastics in Agricultural Crops and Their Possible Impact on Farmers' Health: A Review

The indiscriminate use of plastic products and their inappropriate management and disposal contribute to the increasing presence and accumulation of this material in all environmental zones. The chemical properties of plastics and their resistance to natural degradation lead over time to the production of microplastics (MPs) and nanoplastics, which are dispersed in soil, water, and air and can be absorbed by plants, including those grown for food. In agriculture, MPs can come from many sources (mulch film, tractor tires, compost, fertilizers, and pesticides). The possible effects of this type of pollution on living organisms, especially humans, increase the need to carry out studies to assess occupational exposure in agriculture. It would also be desirable to promote alternative materials to plastic and sustainable agronomic practices to protect the safety and health of agricultural workers.

Microbial strategies for effective microplastics biodegradation: Insights and innovations in environmental remediation

Microplastics (MPs), diminutive yet ubiquitous fragments arising from the degradation of plastic waste, pervade environmental matrices, posing substantial risks to ecological systems and trophic dynamics. This review meticulously examines the origins, distribution, and biological impacts of MPs, with an incisive focus on elucidating the molecular and cellular mechanisms underpinning their toxicity. We highlight the indispensable role of microbial consortia and enzymatic pathways in the oxidative degradation of MPs, offering insights into enhanced biodegradation processes facilitated by innovative pretreatment methodologies. Central to our discourse is the interplay between MPs and biota, emphasizing the detoxification capabilities of microbial metabolisms and enzymatic functions in ameliorating MPs' deleterious effects. Additionally, we address the practical implementations of MP biodegradation in environmental remediation, advocating for intensified research to unravel the complex biodegradation pathways and to forge effective strategies for the expeditious elimination of MPs from diverse ecosystems. This review not only articulates the pervasive challenges posed by MPs but also positions microbial strategies at the forefront of remedial interventions, thereby paving the way for groundbreaking advancements in environmental conservation.

Coupling polyethylene microplastics with other pollutants: Exploring their combined effects on plant health and technologies for mitigating toxicity

The presence of microplastics in agricultural soils has raised concerns regarding their potential impacts on ecosystem health and plant growth. The introduction of microplastics into soil can alter its physicochemical properties, leading to adverse effects on plant development. Furthermore, the adsorption capabilities of microplastics may enhance the toxicity of soil pollutants, potentially resulting in detrimental effects on plant life. Large-sized microplastics may become adhered to root surfaces, impeding stomatal function and restricting nutrient uptake. Conversely, smaller microplastics and nano-plastics may be internalized by plants, causing cellular damage and genotoxicity. In addition, the presence of microplastics in soil can indirectly affect plant growth and development by altering the soil environment. Therefore, it is essential to investigate the potential impacts of microplastics on agricultural ecosystems and develop strategies to mitigate their effects. This review describes the adsorption power between polyethylene microplastics and pollutants (heavy metals, polycyclic aromatic hydrocarbons and antibiotics) commonly found in agricultural fields and the factors affecting the adsorption process. Additionally, the direct and indirect effects of microplastics on plants are summarized. Most of the single or combined microplastic contaminants showed negative effects on plant growth, with a few beneficial effects related to the characteristics of the microplastics and environmental factors. Currently microbial action and the application of soil conditioners or plant growth promoters can alleviate the effects of microplastics on plants to a certain extent. In light of the complex nature of soil environments, future research should concentrate on mitigate and control these interactions and the impact of compound pollution on ecosystems.

Mechanistic insight into interactive effect of microplastics and arsenic on growth of rice (Oryza sativa L.) and soil health indicators

Microplastics (MPs) pollution has recently become a major concern for agroecosystems. The interplay between MPs, and heavy metal(loid)s in the soil can intensify the risks to plant growth and human health. The current study investigated the interactive effects of arsenic (As) and biodegradable and petroleum-based conventional MPs on rice growth, As bioavailability, soil bacterial communities, and soil enzyme activities. As-contaminated soil (5 mg kg-1) was treated with conventional MPs i.e., polystyrene (PS) and polyethylene (PE) and biodegradable MPs i.e., polylactic acid (PLA) and polybutylene adipate terephthalate (PBAT) at 0.1 % and 1 % rates. In a pot experiment, rice plants were cultivated in soil co-contaminated with As and MPs. PLA-MPs exhibited significant interactions with As, increasing its bioavailability and impairing rice plant growth by enhancing plant oxidative stress. The results illustrated that T2 treatment (PLA-MPs @ 1 % + As 5 mg kg-1) significantly decreased the root and shoot lengths, root and shoot dry weights as well as the rates of photosynthesis, transpiration, intercellular CO2, and stomatal conductance in rice plants. Biodegradable PLA-MPs @ 1 % resulted in increased uptake of As in rice roots, stems, and leaves by 13.4 %, 38.9 %, and 20.6 %, respectively. In contrast, conventional PE-MPs @ 1 % showed contradictory results with As uptake declined by 2.2 %, 5.1 %, and 9.9 % in rice roots, stem and leaves. Soil enzyme kinetics showed that biodegradable MPs increased the activities of soil catalase, dehydrogenase, and phytase enzymes, whereas both conventional PS and PE-MPs decreased their activities. Moreover, As and PLA-MPs combined stress altered soil bacterial communities by increasing the relative abundance of Protobacteria, Acidobacteria, Chloroflexi, and Firmicutes phyla by 49 %, 29 %, 82 %, and 57 %, respectively. This study provides new insights into MPs-As interactions in soil-plant system and ecological risks associated with their coexistence.

Review on the relationship between microplastics and heavy metals in freshwater near mining areas

Microplastics (MPs), degraded from plastic wastes, have drawn significant attention worldwide due to its prevalence and rapid transition. Contamination of freshwater with MPs has become an emerging global issue. Heavy metals (HMs), a prominent global pollutant, also garnered much attention due to their potential interaction with MPs, presenting a multifaceted environmental threat. The primary source of HM contamination in freshwater has been identified as mining sites. Additionally, the increasing use of plastic materials within mining areas raises concerns about MP release into the surrounding freshwater environments. Recent studies only provide information on the contamination of HMs status with MPs. However, studies on the mechanism responsible for MPs contamination from both external and internal sources of freshwater MPs and HMs are limited. The knowledge gaps in the deposition and fate of MPs in various mining situations and the possibility of combined impacts of heavy metals and MPs in the ecosystem raise ecological concerns. Here, we review the origins of MPs and HM pollution within mining sites and explore the potential combined detrimental impacts on plants and animal life. We found out that polystyrene (PS) and polyethylene (PE) have higher adsorption affinity to heavy metals, and the mingle toxic consequence of the MPs and HM can depend on the MP surface properties, pH, and salinity of the neighboring water solution. The Langmuir and Freundlich isotherm models enable the efficient design of adsorption systems. The Langmuir model describes single-layer adsorption at homogeneous sites, while the Freundlich model addresses multilayer adsorption on heterogeneous surfaces. The crucial mechanism of adsorption and desorption that underlies the occurrence of both MPs and heavy metals is a decisive matter in this issue.

Coexistence of microplastics and heavy metals in soil: Occurrence, transport, key interactions and effect on plants

Microplastics (MPs) pollution has raised serious environmental concerns due to its widespread generation and discharge across global ecosystems. It is estimated that approximately 400 million metric tons of plastic are produced annually, with 54% ending up as waste. The MPs account for a significant portion of this pollution. These MPs interact with heavy metals (HMs) in terrestrial ecosystems, such as cadmium (Cd), lead (Pb), and arsenic (As), which are introduced through various industrial activities at rates of thousands of tons per year. Such interactions may cause synergistic or antagonistic effects on plants. Recent studies suggest that MPs and HMs exposure impacts various physiological and biochemical pathways in plants, thereby increasing the toxicity symptoms. However, the existing scholarly understanding of the coupled effect of HMs and MPs on plants is limited, highlighting the need to explore these complex dynamics further. Through a comprehensive analysis of current research, this review underscores various pathways of MPs and HMs infiltration mechanisms, detailing their penetration, translocation, and bioaccumulation within plants. The physiological and biochemical effects of both pollutants on plants are deliberated individually and in combination. The review reveals that the co-existence of these contaminants results in a multifaceted environmental challenge, affecting overall plant growth, yield, and quality in ways that differ from individual exposure. Building on recent advancements, this article is expected to delineate the complex interactions between MPs, HMs, and plants and enhance the current understanding of the intricate interplay between them.

Effect of coexisting nutrient divalent cations on cadmium transport in soil-herbal crop systems

Cadmium (Cd) pollution in Chinese herbal medicines poses a serious risk to medication safety. Regulating Cd uptake, transport, and accumulation in plants through ion-ion interactions offers a novel, environmentally sustainable, and practical approach to address this issue. However, the effects and underlying mechanisms of coexisting divalent cations zinc (Zn), magnesium (Mg), and manganese (Mn) on Cd uptake by Ligusticum sinense cv. Chuanxiong (L. chuanxiong) have not been comprehensively studied or well understood. In this study, the application of coexisting these cations (Zn, Mg, Mn) could significantly promote the growth of L. chuanxiong (21.11%-36.04%) and change the mobility of Cd in the soil-crop system. Specifically, adding Zn decreased Cd content in soil and plants by 18.23% and 20.62%, respectively, while Mg increased it by 10.99% and 62.27%. Mn addition, however, had no significant effect. Similar trends in soil enzyme activity were also observed with Zn, Mg, and Mn treatments. Simultaneously, the findings explore how coexisting divalent cations influence plant physiological responses, including photosynthesis and antioxidant capacities, enabling L. chuanxiong to better manage Cd stress. This study underscores the potential of ion-to-ion interactions as an effective approach to mitigate Cd accumulation, offering a practical and sustainable solution for enhancing the safety of Chinese herbal medicines. Additionally, the effects of mixed cation applications on Cd dynamics are complex, shaped by interactions between ion types, dosages, and their specific properties. These insights provide a foundation for developing more effective remediation strategies for Cd-contaminated soils, particularly in the cultivation of medicinal plants.

A critical review of co-pollution of microplastics and heavy metals in agricultural soil environments

The soil environment is a primary destination for contaminants such as microplastics (MPs) and heavy metals (HMs), which are frequently detected simultaneously. The long-term coexistence of MPs and HMs in the soil necessitates unavoidable interactions, affecting their environmental chemical behavior and bioavailability. These co-contaminants pose potential threats to soil organism growth and reproduction, crop productivity, food security, and may jeopardize human health via the food chain. This paper summarizes the sources and trends of MPs in the soil environment, along with the mechanisms and current research status of MP adsorption or desorption of HMs. Additionally, this paper reviews factors affecting HM adsorption on MPs, including MP properties, HM chemical properties, and other environmental factors. Lastly, the effects of MPs and HMs on soil ecology and human health are summarized. The interaction mechanisms and potential biological effects of their co-contamination require further exploration. Future research should delve deeper into the ecotoxic effects of MP-HM co-contamination at cellular and molecular levels, to provide a comprehensive reference for understanding the environmental behavior of their co-contamination in soil.

Microplastics in the soil-water-food nexus: Inclusive insight into global research findings

Nuisance imposed by biotic and abiotic stressors on diverse agroecosystems remains an area of focus for the scientific fraternity. However, emerging contaminants such as microplastics (MP) have imposed additional dimension (alone or in combinations with other stressors) in agroecosystems and keep escalating the challenges to achieve sustainability. MP are recognized as persistent anthropogenic contaminants, fetch global attention due to their unique chemical features that keeps themselves unresponsive to the decaying process. This review has been theorized to assess the current research trends (along with possible gap areas), widespread use of MP, enhancement of the harshness of heavy metals (HMs), complex interactions with physico-chemical constituents of arable soil, accumulation in the edible parts of field crops, dairy products, and other sources to penetrate the food web. So far, the available review articles are oriented to a certain aspect of MP and lack a totality when considered from in soil-water-food perspective. In short, a comprehensive perspective of the adverse effects of MP on human health has been assessed. Moreover, an agro-techno-socio-health prospective-oriented critical assessment of policies and remedial measures linked with MP has provided an extra edge over other similar articles in influential future courses of research.

Meta-analysis reveals the combined effects of microplastics and heavy metal on plants

The combined pollution of microplastics and heavy metals is becoming increasingly serious, and its effects on toxicology and heavy metal accumulation of plants are closely related to crop yield and population health. Here, we collected 57 studies to investigate the effect of microplastics on heavy metal accumulation in plants and their combined toxicity. An assessment was conducted to discover the primary pollutant responsible for the toxicity of combined pollution on plants. The study examined the influence of microplastic characteristics, heavy metal characteristics, and experimental methods on this pollutant. The results showed that combined toxicity of plants was more similar to heavy metals, whereas microplastics interacted with heavy metals mainly by inducing oxidative stress damage. Culture environment, heavy metal type, experimental duration, microplastic concentration and microplastic size were the main factors affecting heavy metal accumulation in plants. There was a negative correlation between experimental duration, microplastic concentration and microplastic size with heavy metal accumulation in plants. The interactions among influencing factors were found, and microplastic biodegradation was the core factor of the strong interaction. These results provided comprehensive insights and guiding strategies for environmental and public health risks caused by the combined pollution of microplastics and heavy metals.

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.

Understanding the Role of Low-Dose Polystyrene Microplastic in Copper Toxicity to Rice Seed (Oryza sativa L.)

There is still much to learn with respect to the potential for microplastics (MPs) to interact with environmental toxins and biota. In the present study, we investigated the effect of MPs on the toxicity of copper (Cu) to rice seeds (Oryza sativa L.). The 7-day median effective concentration (EC50) value of MPs on rice seed germination was 864 mg/L (95% confidence interval [CI] 839 to 897 mg/L). We found that MPs slightly reduced Cu toxicity to rice seeds. The 7-day EC50 of Cu on rice seed germination increased from 7.29 mg/L (95% CI 7.10-7.52 mg/L) to 7.93 mg/L (95% CI 7.58-8.08 mg/L) in the presence of 20 mg/L MPs. We examined this toxicity reduction phenomenon by investigating the role of MPs in the process of Cu transport, Cu accumulation, and metabolic responses. Further investigation found that the MPs used in the present study hardly adsorbed Cu, but these MPs accumulated on the coats of rice seeds and significantly reduced Cu accumulation in rice seedlings. When Cu concentration was 10 mg/L, the presence of MPs reduced the accumulation of Cu in rice seedlings by 34%. We also found that, compared with only Cu present, the addition of MPs resulted in lower reactive oxygen species accumulation and higher catalase activity and glutathione levels in rice seedlings, which also contributed to Cu toxicity reduction. Collectively, the present study shows that polystyrene MPs have the potential to form associations with plant structures which can ultimately impact heavy metal bioaccessibility and therefore toxicity. Environ Toxicol Chem 2024;43:1870-1879. © 2024 SETAC.

Environmental microplastic interact with heavy metal in polluted soil from mine site in the North of Tunisia: Effects on heavy metal accumulation, growth, photosynthetic activities, and biochemical responses of alfalfa plants (Medicago saliva L.)

As emerging persistent pollutants, microplastic (MPs) pollution attracted increasing attention worldwide since it is posing several environmental concerns. MPs interact with heavy metals in soil and may provoke damages on soil properties and ultimately impaired plants and human health. The present study aims to evaluate alfalfa plants (Medicago sativa) response after exposure to heavy metal polluted soils from mine site in the North of Tunisia in presence of environmental microplastic. For that, soils were sampled from two sites of Jebel Ressass mine in addition to a control soil. Plants were exposed to the three soils in presence of two increasing rates of microplastics D1 (1 mg/kg of soil) and D2 (100 mg/kg of soil) for 60 days. After harvest, agronomic parameters, chlorophyll content as well as heavy metal accumulation in plants were analyzed. Furthermore, oxidative status was evaluated in terms of malondialdehyde accumulation (MDA), catalase (CAT) activities and glutathion-S-transferase (GST). Overall, our finding highlights that MPs disrupted agronomic parameters and the photosynthetic activities of alfalfa plants. Additionally, our results revealed that the presence of MPs in polluted soils cause an increase on heavy metal accumulation in alfalfa shoots. Biochemical analyses demonstrated that the combined exposure to MPs and heavy metal induced oxidative stress in alfalfa plants by increasing CAT activity and MDA accumulation. The present investigation highlights the ecological risks of microplastics in terrestrial environment.

Combined contamination of microplastic and antibiotic alters the composition of microbial community and metabolism in wheat and maize rhizosphere soil

The widespread application of antibiotics and plastic films in agriculture has led to new characteristics of soil pollution. The impacts of combined contamination of microplastics and antibiotics on plant growth and rhizosphere soil bacterial community and metabolisms are still unclear. We conducted a pot experiment to investigate the effects of polyethylene (0.2%) and norfloxacin/doxycycline (5 mg kg-1), as well as the combination of polyethylene and antibiotics, on the growth, rhizosphere soil bacterial community and metabolisms of wheat and maize seedlings. The results showed that combined contamination caused more serious damage to plant growth than individual contamination, and aggravated root oxidative stress responses. The diversity and structure of soil bacterial community were not markedly altered, but the composition of the bacterial community, soil metabolisms and metabolic pathways were altered. The co-occurrence network analysis indicated that combined contamination may inhibit the growth of wheat and maize seedings by simplifying the interrelationships between soil bacteria and metabolites, and altering the relative abundance of specific bacteria genera (e.g. Kosakonia and Sphingomonas) and soil metabolites (including sugars, organic acids and amino acids). The results help to elucidate the potential mechanisms of phytotoxicity of the combination of microplastic and antibiotics.

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.

Ecotoxicological effects of polyethylene microplastics and lead (Pb) on the biomass, activity, and community diversity of soil microbes

Microplastics and heavy metals are ubiquitous and persistent contaminants that are widely distributed worldwide, yet little is known about the effects of their interaction on soil ecosystems. A soil incubation experiment was conducted to investigate the individual and combined effects of polyethylene microplastics (PE-MPs) and lead (Pb) on soil enzymatic activities, microbial biomass, respiration rate, and community diversity. The results indicate that the presence of PE-MPs notably reduced soil pH and elevated soil Pb bioavailability, potentially exacerbated the combined toxicity on the biogeochemical cycles of soil nutrients, microbial biomass carbon and nitrogen, and the activities of soil urease, sucrase, and alkaline phosphatase. Soil CO2 emissions increased by 7.9% with PE-MPs alone, decreased by 46.3% with single Pb, and reduced by 69.4% with PE-MPs and Pb co-exposure, compared to uncontaminated soils. Specifically, the presence of PE-MPs and Pb, individually and in combination, facilitated the soil metabolic quotient, leading to reduced microbial metabolic efficiency. Moreover, the addition of Pb and PE-MPs modified the composition of the microbial community, leading to the enrichment of specific taxa. Tax4Fun analysis showed the effects of Pb, PE-MPs and their combination on the biogeochemical processes and ecological functions of microbes were mainly by altering amino acid metabolism, carbohydrate metabolism, membrane transport, and signal transduction. These findings offer valuable insights into the ecotoxicological effects of combined PE-MPs and Pb on soil microbial dynamics, reveals key assembly mechanisms and environmental drivers, and highlights the potential threat of MPs and heavy metals to the multifunctionality of soil ecosystems.

The potential of micro- and nanoplastics to exacerbate the health impacts and global burden of non-communicable diseases

Non-communicable diseases (NCD) constitute one of the highest burdens of disease globally and are associated with inflammatory responses in target organs. There is increasing evidence of significant human exposure to micro- and nanoplastics (MnPs). This review of environmental MnP exposure and health impacts indicates that MnP particles, directly and indirectly through their leachates, may exacerbate inflammation. Meanwhile, persistent inflammation associated with NCDs in gastrointestinal and respiratory systems potentially increases MnP uptake, thus influencing MnP access to distal organs. Consequently, a future increase in MnP exposure potentially augments the risk and severity of NCDs. There is a critical need for an integrated one-health approach to human health and environmental research for assessing the drivers of human MnP exposure and their bidirectional links with NCDs. Assessing these risks requires interdisciplinary efforts to identify and link drivers of environmental MnP exposure and organismal uptake to studies of impacted disease mechanisms and health outcomes.

Effects of combined microplastics and heavy metals pollution on terrestrial plants and rhizosphere environment: A review

Microplastics (MPs) can enter the soil environment through industry, agricultural production and daily life sources. Their interaction with heavy metals (HMs) poses a significant threat to a variety of terrestrial ecosystems, including agricultural ones, thereby affecting crop quality and threatening human health. This review initially addresses the impact of single and combined contamination with MPs and HMs on soil environment, including changes in soil physicochemical properties, microbial community structure and diversity, fertility, enzyme activity and resistance genes, as well as alterations in heavy metal speciation. The article further explores the effects of this pollution on the growth characteristics of terrestrial plants, such as plant biomass, antioxidant systems, metabolites and photosynthesis. In general, the combined contaminants tend to significantly affect soil environment and terrestrial plant growth, i.e., the impact of combined contaminants on plants weight ranged from -87.5% to 4.55%. Similarities and differences in contamination impact levels stem from the variations in contaminant types, sizes and doses of contaminants and the specific plant growth environments. In addition, MPs can not only infiltrate plants directly, but also significantly affect the accumulation of HMs in terrestrial plants. The heavy metals concentration in plants under the treatment of MPs were 70.26%-36.80%. The co-occurrence of these two pollution types can pose a serious threat to crop productivity and safety. Finally, this study proposes suggestions for future research aiming to address current gaps in knowledge, raises awareness about the impact of combined MPs + HMs pollution on plant growth and eco-environmental security.

Influencing mechanisms of microplastics existence on soil heavy metals accumulated by plants

Microplastics (MPs) and heavy metals often coexist in soil, drawing significant attention to their interactions and the potential risks of biological accumulation in the soil-plant system. This paper comprehensively reviews the factors and biochemical mechanisms that influence the uptake of heavy metals by plants, in the existence of MPs, spanning from rhizospheric soil to the processes of root absorption and transport. The paper begins by introducing the origins and current situation of soil contamination with both heavy metals and MPs. It then discusses how MPs alter the physicochemical properties of rhizospheric soil, with a focus on parameters that affect the bioavailability of heavy metals such as aggregates, pH, Eh, and soil organic carbon (SOC). The paper also examines the effect of this pollution on soil organisms and plant growth and reviews the mechanisms by which MPs affect the bioavailability and movement-transformation of heavy metals in rhizospheric soil. This examination emphasizes the roles of rhizospheric microbes, soil fauna, and root physiological metabolism. Finally, the paper outlines the research progress on the mechanisms by which MPs influence the uptake and transport of heavy metals by plant roots. Through this comprehensive review, this paper provides aims to provide environmental managers with a detailed understanding of the potential impact of the coexistence of MPs and heavy metals on the soil-plant ecosystem.

Increased risk of heavy metal accumulation in mangrove seedlings in coastal wetland environments due to microplastic inflow

The recovery phase of mangrove seedlings in coastal wetland ecosystems can be negatively affected by exposure to external pollutants. This study aimed to investigate the impact of microplastics (MPs) influx, specifically polystyrene (PS) and polymethyl methacrylate (PMMA), on the growth of Aegiceras corniculatum seedlings and their accumulation of heavy metals (HMs). PS and PMMA significantly increased HMs accumulation (up to 21.0-548%), particularly in the roots of seedlings, compared to the control treatment (CK). Additionally, elevated activities of malondialdehyde and catalase enzymes were observed in the leaves of seedlings, while peroxidase enzyme activity decreased. Topological analysis of the root sediment microbiota coexistence network revealed that the modularization data increased from 0.69 (CK treatment) to 1.07 (PS treatment) and 5.11 (PMMA treatment) under the combined stress of MPs and HMs. This suggests that the introduction of MPs intensifies microbial modularization. The primary cause of increased HMs accumulation in plants is the MPs input, which influences the secretion of organic acids by plants and facilitates the shift of HMs in sediment to bioavailable states. Furthermore, changes in microbial clustering may also contribute to the elevated HMs accumulation in plants. This study provides valuable insights into the effects of external pollutants on mangrove seedlings and offers new perspectives for the preservation and restoration of mangrove coastal wetlands.

Recent advances in phyto-combined remediation of heavy metal pollution in soil

The global industrialization and modernization have witnessed a rapid progress made in agricultural production, along with the issue of soil heavy metal (HM) pollution, which has posed severe threats to soil quality, crop yield, and human health. Phytoremediation, as an alternative to physical and chemical methods, offers a more cost-effective, eco-friendly, and aesthetically appealing means for in-situ remediation. Despite its advantages, traditional phytoremediation faces challenges, including variable soil physicochemical properties, the bioavailability of HMs, and the slow growth and limited biomass of plants used for remediation. This study presents a critical overview of the predominant plant-based HM remediation strategies. It expounds upon the mechanisms of plant absorption, translocation, accumulation, and detoxification of HMs. Moreover, the advancements and practical applications of phyto-combined remediation strategies, such as the addition of exogenous substances, genetic modification of plants, enhancement by rhizosphere microorganisms, and intensification of agricultural technologies, are synthesized. In addition, this paper also emphasizes the economic and practical feasibility of some strategies, proposing solutions to extant challenges in traditional phytoremediation. It advocates for the development of cost-effective, minimally polluting, and biocompatible exogenous substances, along with the careful selection and application of hyperaccumulating plants. We further delineate specific future research avenues, such as refining genetic engineering techniques to avoid adverse impacts on plant growth and the ecosystem, and tailoring phyto-combined strategies to diverse soil types and HM pollutants. These proposed directions aim to enhance the practical application of phytoremediation and its integration into a broader remediation framework, thereby addressing the urgent need for sustainable soil decontamination and protection of ecological and human health.

Meta-analysis of impacts of microplastics on plant heavy metal(loid) accumulation

The co-occurrence of microplastics (MPs) and heavy metal(loid)s (HMs) has attracted growing scientific interest because of their wide distribution and environmental toxicity. Nevertheless, the interactions between MPs and HMs in soil-plant systems remain unclear. We conducted a meta-analysis with 3226 observations from 87 independent studies to quantify the impact of MPs addition on the plant biomass and HMS accumulation. Co-occurrence of MPs and HMs (except for As) induced synergistic toxicity to plant growth. MPs promoted their uptake in the shoot by 11.0% for Cd, 30.0% for Pb, and 47.1% for Cu, respectively. In contrast, MPs caused a significant decrease (22.6%, 17.9-26.9%) in the shoot As accumulation. The type and dose of MPs were correlated with the accumulation of HMs. MPs increased available concentrations of Cd, Pb, and Cu, but decreased available As concentration in soils. Meanwhile, MPs addition significantly lowered soil pH. These findings may provide explanations for MPs-mediated effects on influencing the accumulation of HMs in plants. Using a machine learning approach, we revealed that soil pH and total HMs concentration are the major contributors affecting their accumulation in shoot. Overall, our study indicated that MPs may increase the environmental risks of HMs in agroecosystems, especially metal cations.

Joint toxicity of cadmium (II) and microplastic leachates on wheat seed germination and seedling growth

Cadmium (Cd) pollution ranks first in soils (7.0%) and microplastics usually have a significant adsorption capacity for it, which could pose potential threats to agricultural production and human health. However, the joint toxicity of Cd and microplastics on crop growth remains largely unknown. In this study, the toxic effects of Cd2+ and two kinds of microplastic leachates, polyvinyl chloride (PVC) and low-density polyethylene (LDPE), on wheat seed germination and seedlings' growth were explored under single and combined conditions. The results showed that Cd2+ solution and two kinds of microplastic leachates stimulated the wheat seed germination process but inhibited the germination rate by 0-8.6%. The combined treatments promoted wheat seed germination but inhibited the seedlings' growth to different degrees. Specifically, the combination of 2.0 mg L-1 Cd2+ and 1.0 mgC L-1 PVC promoted both seed germination and seedlings' growth, but they synergistically increased the antioxidant enzyme activity of seedlings. The toxicity of the PVC leachate to wheat seedlings was stronger than LDPE leachate. The addition of Cd2+ could alleviate the toxicity of PVC leachate on seedlings, and reduce the toxicity of LDPE leachate on seedlings under the same concentration class combinations but aggravated stress under different concentration classes, consistent with the effect on seedlings' growth. Overall, Cd2+, PVC, and LDPE leachates have toxic effects on wheat growth, whether treated under single or combined treatments. This study has important implications for the joint toxicity of Cd2+ solution and microplastic leachates in agriculture.

Interaction of microplastics with heavy metals in soil: Mechanisms, influencing factors and biological effects

Microplastics (MPs) and heavy metals (HMs) in soil contamination are considered an emerging global problem that poses environmental and health risks. However, their interaction and potential biological effects remain unclear. Here, we reviewed the interaction of MPs with HMs in soil, including its mechanisms, influencing factors and biological effects. Specifically, the interactions between HMs and MPs mainly involve sorption and desorption. The type, aging, concentration, size of MPs, and the physicochemical properties of HMs and soil have significant impacts on the interaction. In particular, MP aging affects specific surface areas and functional groups. Due to the small size and resistance to decomposition characteristics of MPs, they are easily transported through the food chain and exhibit combined biological effects with HMs on soil organisms, thus accumulating in the human body. To comprehensively understand the effect of MPs and HMs in soil, we propose combining traditional experiments with emerging technologies and encouraging more coordinated efforts.

Impacts of polypropylene microplastics on the distribution of cadmium, enzyme activities, and bacterial community in black soil at the aggregate level

Microplastics (MPs) can co-occur widely with heavy metals in soil. This study intended to investigate the influences of the co-exposure of polyethylene MPs (0.5 %, w/w) and cadmium (Cd) in black soil on the Cd distribution, enzyme activities, and bacterial communities in both bulk soil and different sized soil aggregates (> 1, 0.50-1, 0.25-0.50, and < 0.25 mm aggregates) after a 90-day incubation. Our results showed that the existence of MPs increased the distributions of Cd in >1 mm and < 0.25 mm soil aggregates and decreased its distributions in 0.50-1 mm and 0.25-0.50 mm soil aggregates. About 12.15 %-17.65 % and 9.03 %-11.13 % of Cd were distributed in the exchangeable and oxidizable forms in bulk soil and various sized soil aggregates after the addition of MPs which were higher than those in the only Cd-treated soil (11.17 %-14.72 % and 8.66 %-10.43 %, respectively), while opposite tendency was found for Cd in the reducible form. Urease and β-glucosidase activities in the Cd-treated soils were 1.14-1.18 and 1.07-1.31 times higher than those in the Cd-MPs treated soils. MPs disturbed soil bacterial community at phylum level and increased the bacteria richness in bulk soil. The levels of predicted functional genes which are linked to the biodegradation and metabolism of exogenous substances and soil C and N cycles were altered by the co-exposure of Cd and MPs. The findings of this study could help deepen our knowledge about the responses of soil properties, especially microbial community, to the co-occurrence of MPs and heavy metals in soil.

Potential synergy of microplastics and nitrogen enrichment on plant holobionts in wetland ecosystems

Wetland ecosystems are global hotspots for environmental contaminants, including microplastics (MPs) and nutrients such as nitrogen (N) and phosphorus (P). While MP and nutrient effects on host plants and their associated microbial communities at the individual level have been studied, their synergistic effects on a plant holobiont (i.e., a plant host plus its microbiota, such as bacteria and fungi) in wetland ecosystems are nearly unknown. As an ecological entity, plant holobionts play pivotal roles in biological nitrogen fixation, promote plant resilience and defense chemistry against pathogens, and enhance biogeochemical processes. We summarize evidence based on recent literature to elaborate on the potential synergy of MPs and nutrient enrichment on plant holobionts in wetland ecosystems. We provide a conceptual framework to explain the interplay of MPs, nutrients, and plant holobionts and discuss major pathways of MPs and nutrients into the wetland milieu. Moreover, we highlight the ecological consequences of loss of plant holobionts in wetland ecosystems and conclude with recommendations for pending questions that warrant urgent research. We found that nutrient enrichment promotes the recruitment of MPs-degraded microorganisms and accelerates microbially mediated degradation of MPs, modifying their distribution and toxicity impacts on plant holobionts in wetland ecosystems. Moreover, a loss of wetland plant holobionts via long-term MP-nutrient interactions may likely exacerbate the disruption of wetland ecosystems' capacity to offer nature-based solutions for climate change mitigation through soil organic C sequestration. In conclusion, MP and nutrient enrichment interactions represent a severe ecological risk that can disorganize plant holobionts and their taxonomic roles, leading to dysbiosis (i.e., the disintegration of a stable plant microbiome) and diminishing wetland ecosystems' integrity and multifunctionality.

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

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

Uptake of microplastics and impacts on plant traits of savoy cabbage

Anthropogenic influences such as plastic pollution are causing serious environmental problems. While effects of microplastics on marine organisms are well studied, less is known about effects of plastic particles on terrestrial organisms such as plants. We investigated the effects of microplastic particles on different growth and metabolic traits of savoy cabbage (Brassica oleracea var. sabauda). Sections of seedlings exposed to polystyrene particles were analysed by coherent Raman scattering microscopy. These analyses revealed an uptake of particles in a size range of 0.5 µm to 2.0 µm into cells of the hypocotyl. Furthermore, plants were grown in substrate amended with polyethylene and polystyrene particles of different sizes (s1: 200-500 µm; s2: 100-200 µm; s3: 20-100 µm; s4: < 100 µm, with most particles < 20 µm; s5: < 20 µm) and in different concentrations (c1 = 0.1%, c2 = 0.01%, c3 = 0.001%). After several weeks, shoot and root biomass were harvested. Leaves were analysed for their carbon to nitrogen ratio, while amino acid and glucosinolate composition were measured using high performance liquid chromatography. Plastic type, particle size and concentration showed distinct effects on certain plant traits. Shoot biomass was interactively influenced by size and concentration of polyethylene, while root biomass was not modified by any of the plastic exposure treatments. Likewise, the composition and total concentrations of leaf amino acids were not affected, but the leucine concentration was significantly increased in several of the plastic-exposed plants. Glucosinolates were also slightly altered, depending on the particle size. Some of the observed effects may be independent of plastic uptake, as larger particles were not taken up but still could affect plant traits. For example, in the rhizosphere plastic particles may increase the water holding capacity of the soil, impacting some of the plant traits. In summary, this study shows how important the plastic type, particle size and concentration are for the uptake of microplastics and their effects on plant traits, which may have important implications for crops, but also for ecosystems.

Interactive impacts of microplastics and arsenic on agricultural soil and plant traits

The ability of microplastics (MPs) to interact with environmental pollutants is currently of great concern due to the increasing use of plastic. Agricultural soils are sinks for multipollutants and the safety of biodegradable MPs in field conditions is questioned. However, still few studies have investigated the interactive effects between MPs and metals on the soil-plant system with agricultural soil and testing crops for human consumption. In this work, we tested the effect on soil and plant parameters of two common MPs, non-degradable plastic low-density polyethylene and biodegradable polymer polylactic acid at two different sizes (<250 μm and 250-300 μm) in association with arsenic (As). Lettuce (Lactuca sativa L.) was used as a model plant in a small-scale experiment lasting 60 days. Microplastics and As explained 12 % and 47 % of total variance, respectively, while their interaction explained 21 %, suggesting a higher toxic impact of As than MPs. Plant growth was promoted by MPs alone, especially when biodegradable MPs were added (+22 %). However, MPs did not affect nutrient concentrations in roots and leaves. The effect of MPs on enzyme activities was variable depending on the time of exposure (with larger effects immediately after exposure), the type and size of the MPs. On the contrary, the co-application of MP and As, although it did not change the amount of bioavailable As in soil in the short and medium term, it resulted in a significant decrease in lettuce biomass (-19 %) and root nutrient concentrations, especially when polylactic acid was applied. Generally, MPs in association with As determined the plant-soil toxicity. This work provides insights into the risk of copollution of MPs and As in agricultural soil and its phytotoxic effect for agricultural crops. However, the mechanisms of the joint effect of MP and As on plant toxicity need further investigation, especially under field conditions and in long-term experiments.

Micro/nanoplastics: Critical review of their impacts on plants, interactions with other contaminants (antibiotics, heavy metals, and polycyclic aromatic hydrocarbons), and management strategies

Microplastic/nanoplastics (MPs/NPs) contamination is not only emerging threat to the agricultural system but also constitute global hazard to the environment worldwide. Recent review articles have addressed the environmental distribution of MPs/NPs and their single-exposure phytotoxicity in various plant species. However, the mechanisms of MPs/NPs-induced phytotoxicity in conjunction with that of other contaminants remain unknown, and there is a need for strategies to ameliorate such phytotoxicity. To address this, we comprehensively review the sources of MPs/NPs, their uptake by and effects on various plant species, and their phytotoxicity in conjunction with antibiotics, heavy metals, polycyclic aromatic hydrocarbons (PAHs), and other toxicants. We examine mechanisms to ameliorate MP/NP-induced phytotoxicity, including the use of phytohormones, biochar, and other plant-growth regulators. We discuss the effects of MPs/NPs -induced phytotoxicity in terms of its ability to inhibit plant growth and photosynthesis, disrupt nutrient metabolism, inhibit seed germination, promote oxidative stress, alter the antioxidant defense system, and induce genotoxicity. This review summarizes the novel strategies for mitigating MPs/NPs phytotoxicity, presents recent advances, and highlights research gaps, providing a foundation for future studies aimed at overcoming the emerging problem of MPs/NPs phytotoxicity in edible crops.

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.

Effects of polyethylene microplastics and heavy metals on soil-plant microbial dynamics

Polyethylene (PE) microplastics are emerging pollutants that pose a significant threat to the environment and human health. However, little is known about the effects of PEs on soil‒plant interactions, especially in heavy metal (HM)-contaminated soil. In this study, the effects of PE on rhizosphere soil enzyme activities, microbial interactions and nutrient cycling processes were analyzed from ecological network and functional gene perspectives for the first time. The results indicated that PE-MP addition significantly reduced the biomass of Bidens pilosa L. In addition, the partial increase in carbon, nitrogen, and phosphorus enzyme activities suggested that the effects of PE as a carbon source on microbial functions in HM-contaminated soil should not be ignored. The average path length of bacterial network nodes was found to be higher than that of fungal network nodes, demonstrating that the bacterial ecological network in PE-MP and HM cocontaminated environments has good buffering capacity against changes in external environmental conditions. Furthermore, structural equation modeling demonstrated that particle size and dosage affect soil nutrient cycling processes and that cycling processes are acutely aware of changes in any factor, such as soil moisture, soil pH and soil nitrogen nutrients. Hence, PE-MP addition in HM-contaminated soil has the potential to alter soil ecological functions and nutrient cycles.

Soil protists are more resilient to the combined effect of microplastics and heavy metals than bacterial communities

Heavy metals and micro-/nanoplastic pollution seriously threaten the environment and ecosystems. While many studies investigated their effects on diverse microbes, few studies have focused on soil protists, and it is unclear how soil protists respond to the combined effect of micro-/nanoplastics and heavy metals. This study investigated how soil protistan and bacterial communities respond to single or combined copper and micro-/nanoplastics. The bacterial community exhibited an instantaneous response to single copper pollution, whereas the combined pollution resulted in a hysteresis effect on the protistan community. Single and combined pollution inhibited the predation of protists and changed the construction of ecological networks. Though single and combined pollution did not significantly affect the overall community structure, the exposure experiment indicated that combined pollution harmed soil amoeba's fitness. These findings offer valuable new insights into the toxic effects of single and combined pollution of copper and plastics on soil protistan and bacterial communities. Additionally, this study shows that sequencing-based analyses cannot fully reflect pollutants' adverse effects, and both culture-independent and dependent methods are needed to reveal the impact of pollutants on soil microbes.

Microplastics and potentially toxic elements: A review of interactions, fate and bioavailability in the environment

In recent years, microplastics (MPs) have obtained growing public concern due to widespread distribution and harmful impacts. Their distinctive features including porous structure, small size, as well as large specific surface area render MPs to be carriers for transporting other pollutants in the environment, especially potentially toxic elements (PTEs). Considering the hot topic of MPs, it is of great significance to comb the reported literature on environmental behaviors of co-occurrence of MPs and PTEs, and systematically discuss their co-mobility, transportation and biotoxicity to different living organisms in diverse environmental media. Therefore, the aim of this work is to systematically review and summarize recent advances on interactions and co-toxicity of MPs and PTEs, in order to provide in-depth understanding on the transport behaviors as well as environmental impacts. Electrostatic attraction and surface complexation mainly govern the interactions between MPs and PTEs, which are subordinated by other physical sorption processes. Besides, the adsorption behaviors are mainly determined by physicochemical properties regarding to different MPs types and various condition factors (e.g., ageing and PTEs concentrations, presence of substances). Generally speaking, recently published papers make a great progress in elucidating the mechanisms, impact factors, as well as thermodynamic and kinetic studies. Bioavailability and bioaccumulation by plant, microbes, and other organisms in both aquatic and terrestrial environment have also been under investigation. This review will shed novel perspectives on future research to meet the sustainable development goals, and obtain critical insights on revealing comprehensive mechanisms. It is crucial to promote efficient approaches on environmental quality improvement as well as management strategies towards the challenge of MPs-PTEs.

Environmental relevant concentrations of polystyrene nanoplastics and lead co-exposure triggered cellular cytotoxicity responses and underlying mechanisms in Eisenia fetida

Heavy metal pollution of soils and the widespread use of plastics have caused environmental problems worldwide. Nanoplastics (NPs) contaminants in water and soil environments can adsorb heavy metals, thereby affecting the bioavailability and toxicity of heavy metals. In this paper, the effect of co-exposure of polystyrene microspheres with 100 nm particle size and lead acetate (Pb) on the Eisenia fetida coelomocytes was investigated. The environmental concentration of NPs used was 0.01 mg/L and the concentration of Pb ranged from 0.01 to 1 mg/L, and the exposed cells were incubated at 298 k for 24 h. Our study demonstrated that exposure of cells to environmental relevant concentrations of NPs did not significantly affect the cytotoxicity of Pb exposure. It was shown that co-exposure induced cellular production of reactive oxygen species (ROS, increased to 134.4 %) disrupted the antioxidant system of earthworm body cavity cells, activated superoxide dismutase and catalase (CAT), produced reduced glutathione, and inhibited glutathione-dependent enzyme (GST) activity (Reduced to 64 %). Total antioxidant capacity (T-AOC) is first enhanced against ROS due to the stress of NPs and Pb. When the antioxidant reserves of cells are exhausted, the antioxidant capacity will decrease. The level of malondialdehyde, a biomarker of eventual lipid peroxidation, increased to 231.7 %. At the molecular level, due to co-exposure to NPs and Pb, CAT was loosely structured and the secondary structure is misfolded, which was responsible for exacerbating oxidative damage in E. fetida coelomocytes. The findings of this study have significant implications for the toxicological interaction and future risk assessment of co-contamination of NPs and Pb in the environment.

Interactions between phenanthrene and polystyrene micro/nano plastics: Implications for rice (Oryza sativa L.) toxicity

Micro/nano plastics (MPs/NPs) are widely distributed and are one of the global pollutants of current concern. Micro/nano plastics can adsorb a variety of persistent organic pollutants, and different particle sizes and surface charges affect the biological effects of MPs/NPs. Therefore, how the compound pollution of MPs/NPs with different particle sizes and organic pollutants produces toxic effects on plants needs to be further studied. We investigated the toxic effects of phenanthrene (Phe) and amino-modified PS (PS-NH2) with two particle sizes (50 nm, 5 μm) on rice. The stress mechanism of PS-NH2 was different between the two particle sizes. Moreover, 50 nm PS-NH2 inhibited stomatal conductance and transpiration rate, reduced photosynthetic rate, significantly enriched GO functions such as "DNA repair" and "DNA double-strand break," and caused severe DNA damage in rice. Notably, 5 μm PS-NH2 affected the gene expression of "photosynthetic lighting" and "photosynthetic antenna protein" in rice, decreased chlorophyll content, and inhibited rice growth. The toxicity of 50 nm PS-NH2 was stronger. In addition, we found that Phe reduced the toxicity of PS-NH2 with different particle sizes, and the relief effect of 50 nm PS-NH2+Phe was more evident. Further, 50 nm PS-NH2+Phe alleviated the toxicity by stimulating the activities of antioxidant enzymes, reducing oxidative damage to chloroplasts, and inhibiting photosynthesis. However, 5 μm PS-NH2+Phe can reduce the stress by reducing the degree of membrane lipid peroxidation, activating metabolic pathways related to the cell wall and cell membrane formation, and plant antitoxin biosynthesis. The results contribute to the understanding of the mechanism of toxicity of MPs/NPs and polycyclic aromatic hydrocarbons (PAHs) to crops.

Unveiling the effect of microplastics on agricultural crops - a review

Microplastics (MPs), ever since they were identified as a potential and widely distributed persistent contaminant, the number of studies highlighting their impacts on various terrestrial ecosystems have been increasing. Recently, the effect of MPs on the agricultural ecosystem has gained momentum. Hence, the present review examines the impact of microplastics on agricultural crop systems and the mechanism underlying its toxicity. The current review revealed that most of the studies were conducted at a laboratory scale and under controlled conditions. Additionally, it was observed that polystyrene (PS) followed by polyethylene (PE) are the most studied polymer type, while the most studied plants are wheat and maize. Hitherto, literature studies suggest that the microplastics' influence on plant growth can be negative or sometimes neutral; while in some cases it exerts a hormetic effect which depends on other factors determining plant growth. Notably, the main mechanisms through which microplastics influence plant growth are mechanical damage, alteration of soil properties, or by leaching of additives. Overall, with burgeoning research interest in this aspect, the current review has significant implications for the toxicity of MPs on plants and throws light on the need to develop novel guidelines toward the sustainable use of plastics in agricultural sector. However, realistic field-level studies and estimating the MPs concentration at various region are essential to develop remediation approaches. Future studies should also focus on translocation and accumulation of micron sized MPs in edible portion of crops and their effect on food safety.

Kaolinite reduced Cd accumulation in peanut and remediate soil contaminated with both microplastics and cadmium

Microplastics (MPs) increase the effective state of heavy metals (HMs) in soil and seriously threaten the yield and quality of peanuts (Arachis Hypogea L.). Kaolinite (KL) has the potential to ameliorate MP- and HM- contaminated soils, but the mechanism of action between them is not well understood. Therefore, 60-day experiments were conducted, where KL (1 %, 2 %) and MPs (0.1 %, 1 %) were individually or jointly mixed into soils with different cadmium (Cd) concentrations (0.5, 2.5, and 5.0 mg·kg-1) to cultivate peanuts in a greenhouse. Finally, soil-bioavailable Cd, peanut dry weight, peanut Cd concentrations, the pH, cation exchange capacity (CEC), dissolved organic carbon (DOC), microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) were determined. It was shown that MPs negatively affected the peanut dry weight and increased the content of soil-bioavailable Cd and Cd concentration in peanut. In the MP- and Cd-contaminated soils, KL mitigated the negative influence of MPs by increasing the dry weight of peanuts by 8.40 %-40.59 %, decreasing the soil-bioavailable Cd by 23.70-35.74 %, and significantly decreasing peanut Cd concentrations by 9.65-30.86 %. The presence of MPs decreased soil pH (7.69-7.87) and the CEC (20.96-23.95 cmol·L-1) and increased the soil DOC (1.84-2.26 mg·kg-1). KL significantly increased soil pH (7.79-8.03) and the CEC (24.96-28.28 cmol·L-1) and mitigated the adverse influence of MPs on the pH and CEC of Cd-contaminated soils. A regression path analysis (RPA) evidenced that KL decreased Cd accumulation in plants by changing the properties of soil contaminated with MPs and Cd. The research results revealed the mechanism of KL on peanut growth and Cd absorption in MP- and Cd-contaminated soil. The results of this study provide a foundation to improve the quality of MP- and HM-contaminated soils and realize safe peanut production.

The synergy of microplastics with the heavy metal zinc has resulted in reducing the toxic effects of zinc on lentil (Lens culinaris) seed germination and seedling growth

There is growing recognition of the impact of the rising presence of microplastics (MPs) on terrestrial plant growth and, in general, the terrestrial ecosystem. Simultaneously, there is growing heavy metal accumulation in agricultural lands at an astonishing rate owing to the overwhelming use of chemical fertilizers, herbicides, and weedicides. Thus, there is a need to investigate the synergetic effect of MPs along with heavy metals on the inducing combined toxicity. This study investigates effects at smaller exposure periods of a few hours using a novel optical imaging technique, Biospeckle Coherence Tomography. Biospeckle Optical Coherence Tomography (bOCT) is a novel optical imaging technique that we successfully demonstrated earlier in visualizing the internal activity of plants. Previous studies of authors using the bOCT technique have demonstrated its potential in the independent application of polyethylene microplastic (PEMPs) as well as zinc within 6 h after their treatments. The strong inhibitory effect of 100 mg L-1, Zn, and PEMPs alone on the germination of Lens culinaris could be visualized with bOCT. The current study demonstrated that against expectation, combined effects of Zn toxicity were reduced when combined with MPs. This is suggested due to the significant reduction of Zn uptake by the seedlings through the interaction of Zn and MPs in an aqueous solution. Mass-spectrometry results also indicate a reduced intake of Zn. Our findings suggest that PEMPs could be able to reduce the over-availability of Zn, thus mitigating the Zn toxicity on lentils.

Plastic in the Environment: A Modern Type of Abiotic Stress for Plant Physiology

In recent years, plastic pollution has become a growing environmental concern: more than 350 million tons of plastic material are produced annually. Although many efforts have been made to recycle waste, a significant proportion of these plastics contaminate and accumulate in the environment. A central point in plastic pollution is demonstrated by the evidence that plastic objects gradually and continuously split up into smaller pieces, thus producing subtle and invisible pollution caused by microplastics (MP) and nanoplastics (NP). The small dimensions of these particles allow for the diffusion of these contaminants in farmlands, forest, freshwater, and oceans worldwide, posing serious menaces to human, animal, and plant health. The uptake of MPs and NPs into plant cells seriously affects plant growth, development, and photosynthesis, finally limiting crop yields and endangering natural environmental biodiversity. Furthermore, nano- and microplastics-once adsorbed by plants-can easily enter the food chain, being highly toxic to animals and humans. This review addresses the impacts of MP and NP particles on plants in the terrestrial environment. In particular, we provide an overview here of the detrimental effects of photosynthetic injuries, oxidative stress, ROS production, and protein damage triggered by MN and NP in higher plants and, more specifically, in crops. The possible damage at the physiological and environmental levels is discussed.

Impact and mitigation of lead, cadmium and micro/nano plastics in fragrant rice

Heavy metals (HMs) and micro(nano)plastics (MNPs), represent a significant risk to global food supply as well as a potential risk to humankind. Over 50% of the worldwide population eat rice every day, and rice aroma is a significant qualitative trait that is highly valued by consumers and fetches premium prices in the global market. Despite the huge commercial importance of fragrant rice, limited studies were directed to investigate the influence of HMs and MNPs on yield related traits and 2-Acetyl-1-pyrroline (2-AP) compound, mainly responsible for aroma production in fragrant rice. In this review, we found that the interaction of HMs and MNPs in fragrant rice is complex and accumulation of HMs and MNPs was higher in root as compared to the grains. Nutrients and phytohormones mediated mitigation of HMs and MNPs were most effective sustainable strategies. In addition, monitoring the checkpoints of 2-AP biosynthesis and its interaction with HMs and MNPs is challenging. Finally, we explained the potential challenges that fragrant rice faces considering the continuous rise in environmental pollutants and discussed the future avenues of research to improve fragrant rice's yield and qualitative traits.

Effects of microplastics and arsenic on plants: Interactions, toxicity and environmental implications

Microplastics are emerging pollutants that are ubiquitously present in environment. Occurrence and dispersion of microplastics in the soil can pose a considerable risk to soil health and biodiversity, including the plants grown in the soil. Uptake and bioaccumulation of microplastics can have detrimental effects on different plant species. Additionally, the co-presence of microplastics and arsenic can cause synergistic, antagonistic, or potentiating toxic impacts on plants. However, limited studies are available on the combined effects of microplastics and arsenic on plants. This paper elucidates both the individual and synergistic effects of microplastics and arsenic on plants. At the outset, the paper highlighted the presence and degradation of microplastics in soil. Subsequently, the interactions between microplastics and plants, accumulation, and influences of microplastics on plant growth and metabolism were explained with underlying mechanisms. Combined effects of microplastics and arsenic on plant growth, metabolism, and toxicity were discussed thereafter. Combined toxic effects of microplastics and arsenic on plants can have detrimental implications on environment, ecosystems and biodiversity. Further investigations on food chain and human health are needed in the context of microplastic-arsenic interactions.