Plastic Bag Derived-Microplastics as a Vector for Metal Exposure in Terrestrial Invertebrates

Sources, interactions, influencing factors and ecological risks of microplastics and antibiotic resistance genes in soil: A review

Microplastics (MPs) and antibiotic resistance genes (ARGs) are gaining increasing attention as they pose a threat to the ecological environment and human health as emerging contaminants. MPs has been proved to be a hot spot in ARGs, and although it has been extensively studied in water environment, the results of bibliometrics statistical analysis in this paper showed that relevant studies in soil ecological environment are currently in the initial stage. In view of this, the paper provides a systematic review of the sources, interactions, influencing factors, and ecological risks associated with MPs and ARGs in soil environments. Additionally, the mechanism and influencing factors of plastisphere formation and resistance are elaborated in detail. The MPs properties, soil physicochemical properties, soil environmental factors and agricultural activities are the primarily factors affecting the interaction between MPs and ARGs in soil. Challenges and development directions of related research in the future are also prospected. It is hoped that the review could assist in a deeper comprehension and exploration of the interaction mechanism between MPs and ARGs in soil as well as the function of MPs in the transmission process of ARGs among diverse environmental media and organisms, and provide theory basis and reference for the MPs and ARGs pollution control and remediation 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.

Microplastic pollution in the Amazon Basin: Current scenario, advances and perspectives

The presence of microplastics (MPs) has been reported in ecosystems in the most different regions of the world and rivers have been identified as one of the main means of transporting this debris to oceans. Recent research shows microplastic deposition and accumulation in the Amazon Basin and, despite being scarce, microplastic pollution is ubiquitous in the region. Of the 9 countries that make up the Amazon Basin, only Brazil, Guyana, Ecuador and Peru have published on the topic, with the main focus on biota (58 %). Several Amazon regions such as Northern Amazon in the Far North of Brazil still have no evidence of microplastic pollution with published data. MP abundance ranges from 5 to 74,500 MPs m-3 for waters, 0 to 8178 MPs kg-1 for sediment and 0.34 to 38.3 MPs individual-1 for biota, with nanoplastic scale (<100 μm) in the sediment. Blue and colorless are the predominant colors, mainly from secondary sources (fibers and fragments). The most commonly found polymers are polyamide, polyethyleneterephthalate and polypropylene. Microplastic abundance in aquatic systems is higher than that found in other rivers, such as the Guayas in Ecuador, the Magdalena, in Colombia and the Surabaya in Indonesia and are similar to regions with intense anthropogenic activity such as the Guanabara Bay - Brazil and the Yellow River in China. The precarious basic sanitation structure, urban planning, waste management, combined with the extensive network of navigable waters, are aggravating factors for the increase in plastic pollution in the region. It is necessary to increase research investment on the topic, considering MP quantification, impacts and the relationship with the hydrosedimentological dynamics of the Amazon Basin. The creation and enforcement of laws that minimize the accumulation of these materials is emerging, besides the development of the bioeconomy and sustainable proposals to minimize plastic pollution in the Amazon.

Investigating the impact of microplastics on triphenyl phosphate adsorption in soil: Insights into environmental factors and soil properties

Microplastics (MPs) pose significant environmental pollution problems owing to their diverse properties such as various shapes, sizes, compositions, surface features, and levels of degradation. Moreover, their interactions with toxic chemicals and aging processes add complexity to environmental research. This study investigated the adsorption of triphenyl phosphate (TPhP) in soil-only, MP-only, and soil-MP simulated environments under different conditions. The experiment involved three phases: initial exposure to a pH of 5.5 under fluorescent light, subsequent introduction of ultraviolet (UV) radiation, and pH adjustment to 4.0 and 7.0, while maintaining UV exposure, each lasting 7 days. The study found that environmental factors affected TPhP sorption capacity, with higher adsorption observed under UV radiation and acidic conditions. In contrast, the MP-only systems showed no clear trend for TPhP adsorption, suggesting kinetic limitations. When MPs were added to the soil, the adsorption dynamics were altered, with varying adsorption capacities observed for different MP polymers under different aging conditions. ATR-FTIR spectroscopy, micro-Raman spectroscopy, and water contact angle measurements suggested potential photooxidation processes and changes in the surface hydrophobicity of the MPs subjected to simulated environmental conditions. This study provides valuable insights into the interplay between soil properties, MP characteristics, and environmental factors in determining TPhP sorption dynamics in soil-MP environments.

Significant influence of land use types and anthropogenic activities on the distribution of microplastics in soil: A case from a typical mining-agricultural city

Microplastics pollution in soil has become a prominent issue in the field of ecological environment. However, relevant data on the microplastics pollution characteristics in mining industry-agricultural soil ecosystems is still limited. In this study, an extensive investigation on the characteristics of microplastics pollution in typical mining-agricultural city soil was conducted, revealing abundances, features, and influencing factors of microplastics in five land use types including facility farmland (FF), traditional farmland (TF), residential land (RL), industrial land (IL), and grassland (GL). The results showed that the distribution of microplastics abundances exhibits a nonuniform pattern, and the highest microplastics abundance was found in FF (3738 ± 2097 items·kg-1) compared with the other four land use types of this study area. Moreover, the key polymers identified were polypropylene (PP) and polyethylene (PE) with a smaller size (<0.01 mm) accounting for the majority at ,45 %, primary colors of microplastics were transparent with the dominant shapes being fibers and fragments. Additionally, principal component analysis and cluster analysis characterized microplastics features across various land use patterns, revealing that agricultural plastic waste, irrigation, and fertilization may be the main the primary sources of agricultural microplastics, while domestic sewage, household waste (include construction waste), and mining transportation activities are the potential urban sources. Correlation analysis indicates a positive relationship between TN, TP, SOC, and the abundances of microplastics (P < 0.05), and a negative relationship between pH and microplastic abundances. Furthermore, Cd, Cu, and As exhibit a significant positive correlation with microplastic characteristics (P < 0.05). Notably, the distribution trends of Cd content and microplastic abundance are similar. Overall, comprehensive analysis of environmental dynamics on microplastics in agricultural soil in coal industrial cities is crucial for developing effective measures to prevent and control microplastic pollution.

Seasonal change in fate and transport of plastics from Red River to the coast of Vietnam

A Lagrangian-particle tracking model, Delft3D-PART, combined with hydrodynamics models are used to investigate the fate and transport of buoyant plastics from Ba Lat river mouth in Red River Delta, northern Vietnam. It was found that during the dry season (Dec-Feb), 23 % (26.43 ton) of the plastics reached the shoreline while 76.1 % (68.3 ton) moved towards the coast further south of Red River Delta. During the wet season (Jun-Aug), 42 % (56.3 ton) were transported offshore away from the coast and 20 % (26.43 ton) distributed along the shore. The two bays adjacent to the river mouth are major hotspots with the intensity skewed towards the upwind side relative to the seasonal monsoon. This phenomenon is exacerbated by storm events which reverse the typical transport and lead to formation of hotspots at the upwind side of the plastic source. Guidance of model results for targeted cleanup operations is discussed.

Microplastics and nanoplastics in soil: Sources, impacts, and solutions for soil health and environmental sustainability

The present review discusses the growing concern of microplastics (MPs) and nanoplastics (NPs) in soil, together with their sources, concentration, distribution, and impact on soil microorganisms, human health, and ecosystems. MPs and NPs can enter the soil through various pathways, such as agricultural activities, sewage sludge application, and atmospheric deposition. Once in the soil, they can accumulate in the upper layers and affect soil structure, water retention, and nutrient availability. The presence of MPs and NPs in soil can also have ecological consequences, acting as carriers for pollutants and contaminants, such as heavy metals and persistent organic pollutants. Additionally, the leaching of chemicals and additives from MPs and NPs can pose public health risks through the food web and groundwater contamination. The detection and analyses of MPs and NPs in soil can be challenging, and methods involve spectroscopic and microscopy techniques, such as Fourier-transform infrared spectroscopy and scanning electron microscopy. To mitigate the presence and effects of MPs and NPs in soil, it is essential to reduce plastic waste production, improve waste management practices, and adopt sustainable agricultural practices. Effective mitigation measures include implementing stricter regulations on plastic use, promoting biodegradable alternatives, and enhancing recycling infrastructure. Additionally, soil amendments, such as biochar and compost, can help immobilize MPs and NPs, reducing their mobility and bioavailability. This review article aims to provide a comprehensive understanding of these emerging environmental issues and identify potential solutions to alleviate their impact on soil health, ecosystem functioning, and community health.

Nano- and microplastics drive the dynamic equilibrium of amoeba-associated bacteria and antibiotic resistance genes

As emerging pollutants, microplastics have become pervasive on a global scale, inflicting significant harm upon ecosystems. However, the impact of these microplastics on the symbiotic relationship between protists and bacteria remains poorly understood. In this study, we investigated the mechanisms through which nano- and microplastics of varying sizes and concentrations influence the amoeba-bacterial symbiotic system. The findings reveal that nano- and microplastics exert deleterious effects on the adaptability of the amoeba host, with the magnitude of these effects contingent upon particle size and concentration. Furthermore, nano- and microplastics disrupt the initial equilibrium in the symbiotic relationship between amoeba and bacteria, with nano-plastics demonstrating a reduced ability to colonize symbiotic bacteria within the amoeba host when compared to their microplastic counterparts. Moreover, nano- and microplastics enhance the relative abundance of antibiotic resistance genes and heavy metal resistance genes in the bacteria residing within the amoeba host, which undoubtedly increases the potential transmission risk of both human pathogens and resistance genes within the environment. In sum, the results presented herein provide a novel perspective and theoretical foundation for the study of interactions between microplastics and microbial symbiotic systems, along with the establishment of risk assessment systems for ecological environments and human health.

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.

Photoaging of polystyrene-based microplastics amplifies inflammatory response in macrophages

The continuous release of municipal and industrial products into the environment poses a growing concern for public health. Among environmental pollutants, polystyrene (PS) stands out as a primary constituent of environmental plastic waste, given its widespread use and high production rates owing to its durability and user-friendly properties. The detection of polystyrene microparticles (PS-MPs) in various living organisms has been well-documented, posing a serious threat due to their potential passage into the human ecosystem. In this manuscript, we aimed to study the toxicological effects of low concentrations of pristine and photoaged PS-MPs in a murine macrophage cell line. To this purpose, PS-MPs were photoaged by indoor exposure to visible light to simulate environmental weathering due to solar irradiation (PS-MPs3h). Physical characterization revealed that the irradiation treatment results in particle degradation and the possible release of nanoparticles. Monocultures of the RAW264.7 cell line were then exposed to PS-MPs and PS-MPs3h at concentrations comparable to experimental measurements from biological samples, to assess cytotoxicity, intracellular oxidative stress, primary genotoxicity, and inflammatory effects. Significant toxicity-related outcomes were observed in cells treated with both pristine PS-MPs and PS-MPs3h even at low concentrations (0,10 μg/ml and 1 μg/ml). PS-MPs3h exhibited greater adverse effects compared to PS-MPs, including reduced cell viability, increased ROS production, elevated DNA damage, and upregulation of IL-6 and NOS2 gene expression. Therefore, we can conclude that changes induced by environmental aging in the physicochemical composition of PS microplastics play a crucial role in the adverse health outcomes associated with microplastic exposure.

Occurrence Characteristics and Ecotoxic Effects of Microplastics in Environmental Media: a Mini Review

The issue of environmental pollution caused by the widespread presence of microplastics (MPs) in environmental media has garnered significant attention. However, research on MPs pollution has mainly focused on aquatic ecosystems in recent years. The sources and pollution characteristics of MPs in the environment, especially in solid waste, have not been well-described. Additionally, there are few reports on the ecotoxicity of MPs, which highlights the need to fill this gap. This review first summarizes the occurrence characteristics of MPs in water, soil, and marine environments, and then provides an overview of their toxic effects on organisms and the relevant mechanisms. This paper also provides an outlook on the hotspots of research on pollution characterization and ecotoxicity of MPs. Finally, this review aims to provide insights for future ecotoxicity control of MPs. Overall, this paper expands our understanding of the pollution characteristics and ecological toxicity of MPs in current environmental media, providing forward-looking guidance for future research.

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.

Distribution characteristics of soil microplastics and their impact on soil physicochemical properties in agricultural areas of the North China plain

Microplastic (MPs) pollution has become a global issue, with particular concern regarding MPs in soil. To determine the characteristics of MPs in agricultural production areas and their impact on soil physicochemical properties, soil samples were collected from different land use types in the North China Plain. Layered sampling was conducted and the soil physicochemical properties were determined. A novel image recognition method based on fluorescence staining was proposed for the batch analysis of MPs in the study area. Together with the results of the soil physicochemical properties, the impact of MPs on soil physicochemical properties was analyzed and evaluated. The results showed that the soil MPs abundance in this agricultural area was moderate to low compared to other agricultural areas, with a larger proportion of particle-type and fragment-type MPs smaller than 10 μm. The soil MPs were predominantly composed of polyvinyl chloride (PVC) and polypropylene (PP). MPs abundance was higher in farmland and forest land than in vegetable fields. The impact of MPs on soil physicochemical properties was mainly manifested in the changes in soil structure due to the different MPs characteristics. Apart from abundance, the type of MPs was found to be the main factor affecting soil bulk density, with particle size and shape influencing the soil aggregate structure. MPs may effect the pH values of sandy and loamy soils, primarily by altering the soil porosity and water holding capacity, but also by increasing the area and duration of contact between the soil medium and external water sources. This study revealed the MPs characteristics in agricultural areas as well as the pathways by which they can impact soil physicochemical properties.

The competition of heavy metals between hyporheic sediments and microplastics of driving factors in the Beiluo River Basin

Both sediments and microplastics (MPs) are medias of heavy metals (HMs) in river ecosystems. This study investigated HMs (Mn, Cr, V, As, Cu, Co, Cd, Pb, and Ni) concentration and driving factors for competitive enrichment between hyporheic sediments versus MPs. The medias basic characteristics indicated that the sediments were mostly sand and rich in Fe2O3; three polymer types were identified, with blue, fragment, less than 500 µm being the main types of MPs. The results have shown that the average content of extracted HMs in MPs was much higher than that of the same metals accumulated in sediments. HMs in sediments and MPs reached heavily polluted at some points, among which As and Cd were ecological risks. Electrostatic adsorption and surface complexation, and biofilm-mediated and organic matter complexation were the interaction mechanism of HMs with sediments and MPs. Further, the driving factors affecting the distribution of HMs in the two carriers were analyzed by multivariate statistical analysis. The results demonstrated that carrier characteristics, hydrochemical factors, and the inherent metal load of MPs were the main causes of the high HMs content. These findings improved our understanding of HMs fate and environmental risks across multiple medias.

Environmentally relevant concentrations of microplastics from agricultural mulch and cadmium negatively impact earthworms by triggering neurotoxicity and disrupting homeostasis

Recent research has highlighted the ecological risk posed by microplastics (MPs) from mulching film and heavy metals to soil organisms. However, most studies overlooked real environmental levels of MPs and heavy metals. To address this gap, pristine and aged polyethylene (PE) mulching film-derived MPs (PMPs, 500 mg/kg; AMPs, 500 mg/kg) were combined with cadmium (Cd, 0.5 mg/kg) to assess the acute toxicity to earthworms and investigate associated molecular mechanisms (oxidative stress, osmoregulation pressure, gut microbiota, and metabolic responses) at environmentally relevant concentrations. Compared to Cd alone and Cd + PMPs treatments (11.15 ± 4.19 items/g), Cd + AMPs treatment resulted in higher MPs bioaccumulation (23.73 ± 13.14 items/g), more severe tissue lesions, and increased cell membrane osmotic pressure in earthworms' intestines. Cd + AMPs induced neurotoxicity through elevated levels of glutamate and acetylcholinesterase. Earthworm intestines (0.98 ± 0.49 to 3.33 ± 0.37 mg/kg) exhibited significantly higher Cd content than soils (0.19 ± 0.01 to 0.51 ± 0.06 mg/kg) and casts (0.15 ± 0.01 to 0.25 ± 0.05 mg/kg), indicating PE-MPs facilitated Cd transport in earthworms' bodies. Metabolomic analysis showed Cd + AMPs exposure depleted energy and nucleotide metabolites, disrupted cell homeostasis more profoundly than Cd and Cd + PMPs treatments. Overall, co-exposure to AMPs + Cd induced more severe neurotoxicity and disruption of homeostasis in earthworm than Cd and PMPs + Cd treatments. Our study, using Cd and MPs with environmental relevance, underscores MPs' role in amplifying Cd accumulation and toxicity in earthworms.

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.

Enhanced Cadmium Adsorption Dynamics in Water and Soil by Polystyrene Microplastics and Biochar

Microplastics (MPs) are prevalent emerging pollutants in soil environments, acting as carriers for other contaminants and facilitating combined pollution along with toxic metals like cadmium (Cd). This interaction increases toxic effects and poses substantial threats to ecosystems and human health. The objective of this study was to investigate the hydrodynamic adsorption of Cd by conducting experiments where polystyrene microplastics (PS) and biochar (BC) coexisted across various particle sizes (10 µm, 20 µm, and 30 µm). Then, soil incubation experiments were set up under conditions of combined pollution, involving various concentrations (0.5 g·kg-1, 5 g·kg-1, 50 g·kg-1) and particle sizes of PS and BC to assess their synergistic effects on the soil environment. The results suggest that the pseudo-second-order kinetic model (R2 = 0.8642) provides a better description of the adsorption dynamics of Cd by PS and BC compared to the pseudo-first-order kinetic model (R2 = 0.7711), with an adsorption saturation time of 400 min. The Cd adsorption process in the presence of PS and BC is more accurately modeled using the Freundlich isotherm (R2 > 0.98), indicating the predominance of multilayer physical adsorption. The coexistence of 10 µm and 20 µm PS particles with BC enhanced Cd absorption, while 30 µm PS particles had an inhibitory effect. In soil incubation experiments, variations in PS particle size increased the exchangeable Cd speciation by 99.52% and decreased the residual speciation by 18.59%. The addition of microplastics notably impacted the exchangeable Cd speciation (p < 0.05), with smaller PS particles leading to more significant increases in the exchangeable content-showing respective increments of 45.90%, 106.96%, and 145.69%. This study contributes to a deeper understanding of the mitigation mechanisms of biochar in the face of combined pollution from microplastics and heavy metals, offering theoretical support and valuable insights for managing such contamination scenarios.

Effects of microplastics and cadmium co-contamination on soil properties, maize (Zea mays L.) growth characteristics, and cadmium accumulation in maize in loessial soil-maize systems

Microplastics (MPs) are pervasive pollutants found in agricultural soils, yet research on the combined impacts of MPs and heavy metals on soil-plant systems remains limited. This study investigates the combined impact of low-density polyethylene (LDPE) microplastics (L: 1 mm, S: 100 μm, 0.1%, 1%) and Cd on soil properties, available Cd content, maize growth, and Cd accumulation by mazie through pot experiments. The findings unveiled notable impacts of the treatment groups, namely MP-L0.1%, MP-S0.1%, MP-L1%, and MP-S1%, on soil organic carbon (SOC), maize height, and catalase (CAT) activity (P < 0.05). The dosage of MPs significantly influenced maize height, MP-S0.1% treatment resulted in a 5.6% reduction, while the other groups had insignificant effects. Particle size and dosage significantly affected SOC and CAT (P < 0.01). The MP-L1% and MP-S1% groups resulted in increases of SOC by 121.5% and 281.0%, respectively. CAT reductions were 32.6%, 62.8%, 41.9%, and 34.9% in MP-L0.1%, MP-S0.1%, MP-L1%, and MP-S1% groups, individually. The Cd treatment induced a significant decrease in soil cation exchange capacity (CEC), maize stem diameter, and root length, accompanied by significant increases in maize plant height, malondialdehyde (MDA), CAT, and superoxide dismutase (SOD) activities. Combined LDPE and Cd contamination had significant effects on maize height and Cd content in leaves. Specifically, MP-L0.1%+Cd, MP-S0.1%+Cd, MP-L1%+Cd, and MP-S1%+Cd reduced maize height by 4.1%, 4.5%, 8.7%, and 13.8%, respectively. The co-presence of LDPE and Cd increased available Cd content in soil while elevating Cd concentration in maize shoots and roots, with a notable 25.5% increase in Cd concentration in maize leaves in the MP-L1%+Cd group compared to the Cd group. Furthermore, LDPE effects on soil-plant systems varied depending on particle size and dosage. This research provides important perspectives on evaluating the concurrent contamination and potential dangers of MPs and toxic metals in soil-plant environments.

A multivariate analysis of microplastics in soils along the headwaters of Yangtze river on the Tibetan Plateau

Microplastics (MPs) are among the most widespread anthropogenic pollutants of natural environments, while limited research has focused on the fate of MPs in soils along the Plateau rivers. In this study, we investigated MPs in soils along the source areas of the Yangtze River on the Qinghai-Tibet Plateau. The results showed mean MP abundance values of (89.4 ± 51.0) and (64.4 ± 24.5) items/kg of dry soils around the tributary and mainstream areas, respectively. Film, transparent colors, and polyethylene were common shape, color, and compositions, respectively. The correlation analysis and PCA revealed that MP abundance was related to soil heavy metals (Cr and Ni) and nutrients (TOC and TP) (p < 0.05). Structural equation modeling also revealed that population density was the dominant driving factor contributing to MPs, with a total effect coefficient of 0.45. In addition, the conditional fragmentation model further distinguished the differences in MP sources from upstream to downstream along the Jinsha River. The significant sources of MPs in the bare land and grasslands from the upper reaches of the Jinsha River included traffic, tourism, and atmospheric transport. In contrast, MP transport during farming activities mainly contributed to MPs in the agricultural soil in the lower reaches.

Modeling of microplastics degradation in aquatic environments using an experimental plan

The aim of this article is to apply advanced predictive modeling techniques to understand the degradation process of microplastics in aquatic environments. Utilizing a Fractional Factorial Central Composite Experimental Plan, this study seeks to develop precise predictive statistical models that enable forecasting the quantity of pollutants generated during the degradation of microplastics under various environmental conditions. This tool was applied to model changes in DOC (dissolved organic carbon) and DEHP (bis(2-ethylhexyl) phthalate) values during the degradation of microplastics in aquatic ecosystems. The methods were developed using data derived from laboratory tests conducted using the GC-MS technique. The obtained approximating functions, considering factors such as degradation time, water temperature, and particle size, significantly reduced the analysis time. A two-stage verification of the approximating functions was conducted, considering the accuracy of the function form, its adequacy, the statistical significance of input variables, and their correlation with DOC and DEHP. The employed a Fractional Factorial Central Composite Experimental Plan allowed for the simultaneous reduction in the number of experiments and prediction of the influence of variables on the output values. Precise predictive models support understanding of the microplastic degradation process, facilitating the development of effective strategies for managing this pollution.

Advancing sustainable agriculture: Evaluation of Poly (lactic acid) (PLA) based mulch films and identification of biodegrading microorganisms among soil microbiota

Non-biodegradable polyolefin based plastic mulch residues in agricultural fields after the end of a crop cycle have raised several concerns as an environmental pollutant in recent years. This study explores the potential of Poly (lactic acid) (PLA) and Poly (butylene adipate-co-terephthalate) (PBAT) based compostable films reactively blended with compatibilizers and chain extenders as a promising solution to environmental challenges associated with traditional plastic mulch films. Epoxidized soybean oil (ESO) and Epoxy-functionalized styrene acrylic copolymer (ESA) have been used as reactive compatibilizers and chain extenders respectively. In-depth analysis of the mechanical, thermal, and barrier properties of the developed films, revealed that the PLA/PBAT blend films at 75:25 weight ratio in the presence of 5 phr ESO and 0.5 phr ESA exhibit improved performance characteristics for application as mulch films. Furthermore, the films were subjected to 360-h UV exposure to gauge their stability under prolonged exposure, specifically investigating changes in the carbonyl index. Additionally, a rigorous real-time field trial of the mulch films spanning eight months with various crops was carried out to understand their performance in practical agricultural settings. The study also involved the identification of microorganisms responsible for the degradation of the developed mulch films employing 16S rRNA sequencing.

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.

A Study on the Growth and Physiological Toxicity Effects of the Combined Exposure of Microplastics and Cadmium on the Vicia faba L. Seedlings

To investigate the toxicological effects of polystyrene microplastics (PS-MPs), cadmium (Cd), and their combined contamination on the growth and physiological responses of V. faba seedlings, this experiment employed a hydroponic method. The Hoagland nutrient solution served as the control, changes in root growth, physiological and biochemical indicators of V. faba seedlings under different concentrations of PS-MPs (10, 100 mg/L) alone and combined with 0.5 mg/L Cd. The results demonstrated that the root biomass, root vitality, generation rate of superoxide radicals (O2·-), malondialdehyde (MDA) content, and superoxide dismutase (SOD) activity increased with increasing concentration under the influence of PS-MPs alone, while the soluble sugar content and peroxidase (POD) activity decreased. In the combined treatment with Cd, the trends of these indicators are generally similar to the PS-MPs alone treatment group. However, root vitality and SOD activity showed an inverse relationship with the concentration of PS-MPs. Furthermore, laser confocal and electron microscopy scanning revealed that the green fluorescent polystyrene microspheres entered the root tips of the V. faba and underwent agglomeration in the treatment group with a low concentration of PS-MPs alone and a high concentration of composite PS-MPs with Cd.

Asian clam Corbicula fluminea as potential biomonitor of microplastics and metal(oid)s in a Patagonian River

This study summarizes the concentration in dry weight (dw) of several metal(oid)s (As, Cd, Cr, Cu, Mn, Ni, Pb, and Zn), as well as the abundance and characteristics of microplastics (MP) in wet weight (ww) of the soft tissues of clam Corbicula fluminea from Chubut River (Patagonia, Argentina). The contents of essential elements were in the following decreasing order: Zn > Mn > Cu > Ni; meanwhile, non-essential elements Cd, Cr and Pb were below the detection limit (<0.5 μg/g dw). A high mean concentration of As (6.1 ± 0.3 μg/g dw) was found, surpassing the maximum allowable limit established by the Argentine Food Code for bivalve molluscs. The number of MP ranged from 0.07 to 1.27 items/ind. and from 0.2 to 2.9 items/g ww. Fibers were the most common shape, mainly transparent. The size of MP ranged from 42 to 1917 μm, accounting for 62 % of MP between 50 and 450 μm. The dominant polymer was PET based on the results of Raman spectroscopy. Based on the widespread distribution of MP in the environment and the wide range of effects on organisms, it is necessary to develop long-term monitoring programs for MP contamination in different environmental matrices. Understanding the bioaccumulation of MP in bivalves is crucial to assess the potential risk to human health through consumption and to the ecosystem. We propose that the widespread Asian clam could serve as a useful biomonitor for MP and As pollution in freshwater and estuarine environments such as the Chubut River.

Occurrence characteristics and potential risk of microplastics under different land conditions

Microplastics (MPs) pollution has caused widespread concern, more researchers have focused on MPs in farmland soil. However, the distribution of MPs in different land use types, land restoration years and crop types remained largely unexplored. Therefore, the study investigated the distribution characteristics and evaluated ecological risk of MPs in soil of northern Shaanxi Province, China. The abundance, particle size, morphology and polymer types of MPs in soil were analyzed by sample collection, Raman spectroscopy and laser direct infrared spectroscopy (LDIR). The ecological risk index (H) and pollution load index (PLI) were employed to assess the risks posed by MPs in the soil. It was shown that the concentration of MPs in farmland soil was the highest (4483 items·kg-1) among the different land use types. The average abundance of microplastics in farmland soil was 1.98 times than that in industrial park soil. An increase in restoration years corresponded with a decrease in MPs abundance and an increase in smaller-sized MPs. In addition, the content of MPs in the soil of perennial crops was more stable, with fluctuations less than 25%, and the size of MPs was smaller than that of the annual crops. The main types of MPs in the soil of the study area were PP (28.5%) and PET (24.1%), MPs with size between 20 and 40 μm were dominated. Based on the pollution load index (PLI), 51.9% of the sampling sites were categorized as moderately polluted, and the MPs pollution risk of farmland soil was the highest. Mild and moderate pollution caused fewer adverse impact, while extremely strong pollution was detrimental to ecosystems and human health. In general, the study would provide a foundational understanding of MPs pollution levels and environment risk associated with different land use types, land restoration years and crop types.

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.

Non-negligible impact of microplastics on wetland ecosystems

There has been much concern about microplastic (MP) pollution in marine and soil environments, but attention is gradually shifting towards wetland ecosystems, which are a transitional zone between aquatic and terrestrial ecosystems. This paper comprehensively reviews the sources of MPs in wetland ecosystems, as well as their occurrence characteristics, factors influencing their migration, and their effects on animals, plants, microorganisms, and greenhouse gas (GHG) emissions. It was found that MPs in wetland ecosystems originate mainly from anthropogenic sources (sewage discharge, and agricultural and industrial production) and natural sources (rainfall-runoff, atmospheric deposition, and tidal effects). The most common types and forms of MPs identified in the literature were polyethylene and polypropylene, fibers, and fragments. The migration of MPs in wetlands is influenced by both non-biological factors (the physicochemical properties of MPs, sediment characteristics, and hydrodynamic conditions) and biological factors (the adsorption and growth interception by plant roots, ingestion, and animal excretion). Furthermore, once MPs enter wetland ecosystems, they can impact the resident microorganisms, animals, and plants. They also have a role in global warming because MPs act as unique exogenous carbon sources, and can also influence GHG emissions in wetland ecosystems by affecting the microbial community structure in wetland sediments and abundance of genes associated with GHG emissions. However, further investigation is needed into the influence of MP type, size, and concentration on the GHG emissions in wetlands and the underlying mechanisms. Overall, the accumulation of MPs in wetland ecosystems can have far-reaching consequences for the local ecosystem, human health, and global climate regulation. Understanding the effects of MPs on wetland ecosystems is essential for developing effective management and mitigation strategies to safeguard these valuable and vulnerable environments.

The triple exposure nexus of microplastic particles, plastic-associated chemicals, and environmental pollutants from a human health perspective

The presence of microplastics (MPs) is increasing at a dramatic rate globally, posing risks for exposure and subsequent potential adverse effects on human health. Apart from being physical objects, MP particles contain thousands of plastic-associated chemicals (i.e., monomers, chemical additives, and non-intentionally added substances) captured within the polymer matrix. These chemicals are often migrating from MPs and can be found in various environmental matrices and human food chains; increasing the risks for exposure and health effects. In addition to the physical and chemical attributes of MPs, plastic surfaces effectively bind exogenous chemicals, including environmental pollutants (e.g., heavy metals, persistent organic pollutants). Therefore, MPs can act as vectors of environmental pollution across air, drinking water, and food, further amplifying health risks posed by MP exposure. Critically, fragmentation of plastics in the environment increases the risk for interactions with cells, increases the presence of available surfaces to leach plastic-associated chemicals, and adsorb and transfer environmental pollutants. Hence, this review proposes the so-called triple exposure nexus approach to comprehensively map existing knowledge on interconnected health effects of MP particles, plastic-associated chemicals, and environmental pollutants. Based on the available data, there is a large knowledge gap in regard to the interactions and cumulative health effects of the triple exposure nexus. Each component of the triple nexus is known to induce genotoxicity, inflammation, and endocrine disruption, but knowledge about long-term and inter-individual health effects is lacking. Furthermore, MPs are not readily excreted from organisms after ingestion and they have been found accumulated in human blood, cardiac tissue, placenta, etc. Even though the number of studies on MPs-associated health impacts is increasing rapidly, this review underscores that there is a pressing necessity to achieve an integrated assessment of MPs' effects on human health in order to address existing and future knowledge gaps.

The impact of arbuscular mycorrhizal fungi and endophytic bacteria on peanuts under the combined pollution of cadmium and microplastics

It remains unclear how symbiotic microbes impact the growth of peanuts when they are exposed to the pollutants cadmium (Cd) and microplastics (MPs) simultaneously. This study aimed to investigate the effects of endophytic bacteria Bacillus velezens SC60 and arbuscular mycorrhizal fungus Rhizophagus irregularis on peanut growth and rhizosphere microbial communities in the presence of Cd at 40 (Cd40) or 80 (Cd80) mg kg-1 combined without MP or the presence of low-density polyethylene (LDPE) and poly butyleneadipate-co-terephthalate (PBAT). This study assessed soil indicators, plant parameters, and Cd accumulation indicators. Results showed that the application of R. irregularis and B. velezens significantly enhanced soil organic carbon and increased Cd content under the conditions of Cd80 and MPs co-pollution. R. irregularis and B. velezens treatment increased peanut absorption and the enrichment coefficient for Cd, with predominate concentrations localized in the peanut roots, especially under combined pollution by Cd and MPs. Under treatments with Cd40 and Cd80 combined with PBAT pollution, soil microbes Proteobacteria exhibited a higher relative abundance, while Actinobacteria showed a higher relative abundance under treatments with Cd40 and Cd80 combined with LDPE pollution. In conclusion, under the combined pollution conditions of MPs and Cd, the co-treatment of R. irregularis and B. velezens effectively immobilized Cd in peanut roots, impeding its translocation to the shoot.

Toxicological Research on Nano and Microplastics in Environmental Pollution: Current Advances and Future Directions

This review explains the sources of nanoplastics (NPs) and microplastics (MPs), their release, fate, and associated health risks in the aquatic environment. In the 21st century, scientists are grappling with a major challenge posed by MPs and NPs. The global production of plastic has skyrocketed from 1.5 million tons in the 1950s to an astonishing 390.7 million tons in 2021. This pervasive presence of these materials in our environment has spurred scientific inquiry into their potentially harmful effects on living organisms. Studies have revealed that while MPs, with their larger surface area, are capable of absorbing contaminants and pathogens from the surroundings, NPs can easily be transferred through the food chain. As a result, living organisms may ingest them and accumulate them within their bodies. Due to their minuscule size, NPs are particularly difficult to isolate and quantify. Furthermore, exposure to both NPs and MPs has been linked to various adverse health effects in aquatic species, including neurological impairments, disruption of lipid and energy metabolism, and increased susceptibility to cytotoxicity, oxidative stress, inflammation, and reactive oxygen species (ROS) production. It is alarming to note that MPs have even been detected in commercial fish, highlighting the severity of this issue. There are also challenges associated with elucidating the toxicological effects of NPs and MPs, which are discussed in detail in this review. In conclusion, plastic pollution is a pressing issue that governments should tackle by ensuring proper implementation of rules and regulations at national and provincial levels to reduce its health risks.

Research progress on the origin, fate, impacts and harm of microplastics and antibiotic resistance genes in wastewater treatment plants

Previous studies reported microplastics (MPs), antibiotics, and antibiotic resistance genes (ARGs) in wastewater treatment plants (WWTPs). There is still a lack of research progress on the origin, fate, impact and hazards of MPs and ARGs in WWTPs. This paper fills a gap in this regard. In our search, we used "microplastics", "antibiotic resistance genes", and "wastewater treatment plant" as topic terms in Web of Science, checking the returned results for relevance by examining paper titles and abstracts. This study mainly explores the following points: (1) the origins and fate of MPs, antibiotics and ARGs in WWTPs; (2) the mechanisms of action of MPs, antibiotics and ARGs in sludge biochemical pools; (3) the impacts of MPs in WWTPs and the spread of ARGs; (4) and the harm inflicted by MPs and ARGs on the environment and human body. Contaminants in sewage sludge such as MPs, ARGs, and antibiotic-resistant bacteria enter the soil and water. Contaminants can travel through the food chain and thus reach humans, leading to increased illness, hospitalization, and even mortality. This study will enhance our understanding of the mechanisms of action among MPs, antibiotics, ARGs, and the harm they inflict on the human body.

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.

Innovative overview of the occurrence, aging characteristics, and ecological toxicity of microplastics in environmental media

Microplastics (MPs), pollutants detected at high frequency in the environment, can be served as carriers of many kinds of pollutants and have typical characteristics of environmental persistence and bioaccumulation. The potential risks of MPs ecological environment and health have been widely concerned by scholars and engineering practitioners. Previous reviews mostly focused on the pollution characteristics and ecological toxicity of MPs, but there were few reviews on MPs analysis methods, aging mechanisms and removal strategies. To address this issue, this review first summarizes the contamination characteristics of MPs in different environmental media, and then focuses on analyzing the detection methods and analyzing the aging mechanisms of MPs, which include physical aging and chemical aging. Further, the ecotoxicity of MPs to different organisms and the associated enhanced removal strategies are outlined. Finally, some unresolved research questions related to MPs are prospected. This review focuses on the ageing and ecotoxic behaviour of MPs and provides some theoretical references for the potential environmental risks of MPs and their deep control.

Exchangeable versus residual metals in naturally aged plastic litter

Metals may be associated with plastics as additives arising from manufacture or through acquisition from the environment, but these associations are often poorly defined or referred to synonymously when considering metal availability. In this study, samples of plastic litter (n = 22) have been collected from various environmental and industrial compartments of Lublin Province, Poland, and fractionated according to polymer type (polyethylene, polyethylene terephthalate, nylon, expanded polystyrene, polypropylene, and "mixed") before being micronised to < 2 mm. Composites (n = 89) were subjected to two phases of a standardised and widely employed sequential extraction protocol (Bureau Communautaire de Reference; BCR) in order to define available (acid-soluble and exchangeable) and residual (soluble in boiling aqua regia) concentrations of Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Zn. For a given metal, total content, calculated by summing available and residual components, was highly variable, both between locations and amongst polymer categories, reflecting the heterogeneous distribution of a multitude of different additives. Overall, however, concentrations were greatest for Fe, with medians of several hundred to several thousand mg kg-1 amongst the different polymers, and lowest for Cd, Co, and Ni, where nearly all concentrations were below 10 mg kg-1. Median percentage metal availabilities were greatest for expanded polystyrene and were above 25% for Mn and Zn and below 10% for Cr and Fe in all polymer types. These observations are largely, but not entirely, attributed to the relative contributions of metals acquired from the environment and metals present as additives and residues. Significantly, the approach employed allows direct comparisons of metal availability in plastics with metal availability in environmental solids in order to evaluate the overall impacts of plastics in metal risk assessments.

Assessment of microplastic contamination in shrimps from the Bay of Bengal and associated human health risk

Microplastics (MPs) were analyzed in seven shrimp species Tiger shrimp (Penaeus monodon), Red tiger shrimp (Caridina cantonensis), Indian shrimp (Penaeus indicus), Red shrimp (Metapenaeus dobsoni), White shrimp (Penaeus merguiensis), Brown shrimp (Metapenaeus monoceros), and Roshna shrimp (Palaemon styliferus) collected from the Bay of Bengal. The abundance and characteristics of MPs were assessed in the gastrointestinal tract (GIT), which certainly translocated to the muscle of shrimp species. The highest MP abundance was found in C. cantonensis with 7.2 items/individual (25.3 items/g in the GIT and 6.3 items/g in muscle). The prominent types of MPs in shrimp samples were fibers (30 %) and fragments (29 %). The ingestion rate of MPs of black and transparent color was comparatively higher, with 64 % of the ingested MPs were < 100 μm. The primary polymer types detected based on Fourier Transform Infrared (FTIR) analysis were Low-Density Polyethylene (LDPE), High-Density Polyethylene (HDPE), Polymethyl Methacrylate (PMMA), Polyvinyl Chloride (PVC), Polypropylene (PP), and Ethylene Vinyl Acetate (EVA). Results from Scanning Electron Microscopy (SEM) showed rough surface textures and adhered particles on the MPs isolated from shrimps. The margin of exposure for females was 71.42, and for males, it was 80.64, indicating that women in Bangladesh are more likely to be exposed to MPs and face a higher risk than men. Sensitivity analysis revealed that MPs particle size was the most sensitive parameter. These findings provide a comprehensive understanding of MP ingestion, human exposure, and contamination in shrimps of Bangladesh, which can help future monitoring efforts.

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.

Size- and concentration-dependent effects of microplastics on soil aggregate formation and properties

Plastics fragment and threaten soil ecosystems. Degradation of soil structure is one of the risks. Despite this, data on impacts of different sized microplastics (MPs) on soil aggregates is lacking. This study systematically investigated the effects of pristine polyethylene powders of different sizes (< 35, < 125, < 500 µm) and concentrations (0, 0.1, 1.0, 10 wt%) on aggregate formation and their properties for two contrasting soils (woodland soil, WS; agricultural soil, AS). 75 day wet-dry cycles produced newly-formed aggregates in all treatments. MP size and concentration impacted the incorporation of MPs in aggregates and this varied with aggregate size; the size distribution of aggregates also varied with MP size and concentration. Aggregates produced in soil containing 10 wt% < 35 µm MPs had significantly lower MWDs (mean weight diameters) than controls. The wettability of aggregates (> 4 mm) reduced with increasing MP exposure concentration and decreasing MP exposure size. MP incorporation decreased the water stability of aggregates (1-2 mm) in WS but increased it in AS. The particle density of aggregates (> 4 mm) significantly decreased with increasing MP concentration, whereas MP size had no effect. As MPs breakdown, fragment and become smaller over time, their potential risk to the aggregated structure of soil increases.

Co-exposure to environmental microplastic and the pesticide 2,4-dichlorophenoxyacetic acid (2,4-D) induce distinctive alterations in the metabolome and microbial community structure in the gut of the earthworm Eisenia andrei

Microplastics (MPs) are recognized as emergent pollutants and have become a significant environmental concern, especially when combined with other contaminants. In this study, earthworms, specifically Eisenia andrei, were exposed to MPs (at a concentration of 10 μg kg-1 of soil), herbicide 2,4-D (7 mg kg-1 of soil), and a combination of the two for 7 and 14 days. The chemical uptake in the earthworms was measured, and the bacterial and archaeal diversities in both the soil and earthworm gut were analyzed, along with the metabolomic profiles. Additionally, data integration of the two omics approaches was performed to correlate changes in gut microbial diversity and the different metabolites. Our results demonstrated that earthworms ingested MPs and increased 2,4-D accumulation. More importantly, high-throughput sequencing revealed a shift in microbial diversity depending on single or mixture exposition. Metabolomic data demonstrated an important modulation of the metabolites related to oxidative stress, inflammatory system, amino acids synthesis, energy, and nucleic acids metabolism, being more affected in case of co-exposure. Our investigation revealed the potential risks of MPs and 2,4-D herbicide combined exposure to earthworms and soil fertility, thus broadening our understanding of MPs' toxicity and impacts on terrestrial environments.

Adsorption and desorption of Hg(II) by four aged microplastics and its effects on gaseous elemental mercury production in seawater

Microplastics (MPs) weather after entering the environment gradually, and the interaction with metal ions in the aqueous environment has received extensive attention. However, there are few studies on Hg(Ⅱ), especially the effect of MPs on the release of Hg0(DEM) in water after entering the aqueous environment. In this study, four types of MPs (PP, PE, PET, PVC) were selected to study the adsorption and desorption behavior of Hg(Ⅱ) after photoaging and to explore the influence of MPs on the release of DEM in seawater under different lighting conditions. The results showed that the specific surface area, negative charges, and oxygen-containing functional group of MPs increased after aging. The adsorption capacity of aged MPs for Hg(Ⅱ) was significantly improved, which was consistent with the pseudo-first-order and pseudo-second-order model, indicating that the adsorption process was a chemical and physical adsorption. The fitting results of the in-particle diffusion model indicated that the adsorption was controlled by multiple steps. Hg(Ⅱ) was easier to desorb in the simulated gastric fluid environment. Because the aged MPs had the stronger binding force to Hg(Ⅱ), their desorption rate is lower than new MPs. Under visible light and UVA irradiation, MPs inhibited the release of Hg0. Under UVA, the mass of DEM produced in seawater with aged PE and PVC was higher than that of new PE and PVC. The aged PE and PVC could produce more ·O2-, which was conducive to the reduction of mercury. However, in UVB irradiation, the addition of MPs promoted the release of DEM, and ·O2- also played an important contribution in affecting the photochemical reaction of mercury. Therefore, the presence of aged MPs will significantly affect the water-air exchange of Hg in water. Compared with new MPs, aged MPs improved the contribution of free radicals in Hg transformation by releasing reactive oxygen species. This study extends the understanding of the effects of MPs on the geochemical cycle of Hg(Ⅱ) in seawater, better assesses the potential combined ecological risks of MPs and Hg(Ⅱ), and provides certain guidance for the pollution prevention and control of MPs.

The combined effects of polystyrene nanoplastics with nickel on oxidative stress and related toxic effects to earthworms from individual and cellular perspectives

Nanoplastics may adsorb other pollutants in the environment due to their high specific surface area and small size. We used earthworms as experimental organisms to evaluate the ecotoxicity of NPs and Ni combined pollution at the individual and cellular levels. The results showed that when only 20 mg/L Ni2+ was added to the combined pollution system, the antioxidant system of earthworm coelomocytes was destroyed to a certain extent, the ROS level increased, the cell viability decreased significantly, and the redox balance was destroyed. With the introduction of PS-NPs and the increase of concentration, the oxidative damage in the coelomocytes of earthworms gradually increased, and finally tended to be stable when the maximum concentration of 50 mg/L PS-NPs and Ni were exposed together. At the animal level, the activities of CAT and SOD decreased within 28 days of exposure, and the combined pollution showed a synergistic effect. At the same time, it promoted the synthesis of GST in earthworms, improved their detoxification ability and reduced oxidative damage. The changes of T-AOC and MDA showed that the combined pollution caused the accumulation of ROS and caused more serious toxicological effects. With the increase of exposure time, the antioxidant system of earthworms was continuously destroyed, and the oxidative damage was serious, which induced more serious lipid peroxidation and caused the damage of earthworm body wall structure.

Coexistence of microplastics and Cd alters soil N transformation by affecting enzyme activity and ammonia oxidizer abundance

Interactions between heavy metal and microplastics represent a serious threat to ecosystems and human health, but the effect of their coexistence on the soil N transformation processes is unclear. The mechanism in which metal-polluted soil reacts to additional microplastics stress and their toxicology interactions on soil N transformation were determined by investigating the dynamics of soil microbial N transformation in response to Cd stress and different doses of polythene (PE) microplastics by conducting a 14 days aerobic 15N microcosmic incubation experiment. The gross nitrification rates (n_gross) were decreased by 7.47% and 12.5% in the 1% and 2% (w/w) PE groups, respectively, through the direct effect on enzyme activity (β-glucosidase, N-acetylglucosaminidase, and leucine-aminopeptidase) and the abundance and community composition of ammonia oxidizer. It also exerted indirect effect by reducing nitrification substrate concentrations. PE microplastics (>1% [w/w]) significantly increased the gross N immobilization rate, and this change could have been driven by C/N stoichiometry. Cd stress alone led to a rapid short-term mineralization-immobilization turnover (1.67 times of the control). However, such effect was offset when Cd coexisted with PE microplastics, possibly because Cd was directly adsorbed by PE microplastics, and/or microplastics satisfied the C demand by microorganisms under Cd stress. Our findings demonstrated that the coexistence of microplastics and Cd significantly altered soil N nitrification and immobilization, which would change the N bioavailability in soil and alter the effect N cycling on the ecological environment.

Physical characteristics of microplastic particles and potential for global atmospheric transport: A meta-analysis

Recent interest in microplastic pollution of natural environments has brought forth samples which confirm the pollutant's omnipresence in a variety of ecosystems. This includes locations furthest removed from human activity. Atmospheric transport and deposition are suspected as the primary transport pathway to these remote locations. The factors most influential on participation in atmospheric transport are yet to be determined. This meta-analysis aims to identify patterns that exist between physical characteristics of microplastic particles and their potential for atmospheric transport. Our review addresses the following questions: Which characteristics of microplastic particles promote atmospheric transport and deposition into remote regions, and how significant are these factors in determining distance transported from their sources? This article analyzes commonly reported physical attributes-- shape, polymer composition and color-- from studies in urban and remote areas. The analysis of 68 studies, composed of data from 2078 samples, shows higher occurrence of microplastic particles in remote samples with fiber shapes, polyester compositions, and red, blue, and transparent colors. This meta-analysis is the first to identify patterns between physical properties of microplastic particles and extent of their participation in atmospheric transport to global remote locations.

Microplastics in soils: Production, behavior process, impact on soil organisms, and related toxicity mechanisms

In recent years, microplastics (MPs) pollution has become a hot ecological issue of global concern and MP pollution in soil is becoming increasingly serious. Studies have shown that MPs have adverse effects on soil biology and ecological functions. Although MPs are evident in soils, identifying their source, abundance, and types is difficult because of the complexity and variability of soil components. In addition, the effects of MPs on soil physicochemical properties (PCP), including direct effects such as direct interaction with soil particles and indirect effects such as the impact on soil organisms, have not been reported in a differentiated manner. Furthermore, at present, the soil ecological effects of MPs are mostly based on biological toxicity reports of their exudate or size effects, whereas the impact of their surface-specific properties (such as environmentally persistent free radicals, surface functional groups, charge, and curvature) on soil ecological functions is not fully understood. Considering this, this paper reviews the latest research findings on the production and behavioral processes of MPs in soil, the effects on soil PCP, the impacts on different soil organisms, and the related toxic mechanisms. The above discussion will enhance further understanding of the behavioral characteristics and risks of MPs in soil ecosystems and provide some theoretical basis for further clarification of the molecular mechanisms of the effects of MPs on soil organisms.

A biodegradable oxidized starch/carboxymethyl chitosan film coated with pesticide-loaded ZIF-8 for tomato fusarium wilt control

Film mulching is one of the most important methods to control soil-borne diseases. However, the traditional mulch may cause microplastic pollution and soil ecological damage. Herein, a biodegradable film was developed using oxidized starch and carboxymethyl chitosan and incorporated ZIF-8 carrying fludioxonil to sustainably control soil-borne disease. The microstructure, mechanical properties, optical properties, and water barrier properties of the composite films (Flu@ZIF-8-OS/CMCS) were investigated. The results show that Flu@ZIF-8-OS/CMCS had a smooth and uniform surface and excellent light transmittance. The excellent mechanical properties of the films were verified by tensile strength, elongation at break and Young's modulus. Higher contact angle and lower water vapor permeability indicate water retention capacity of the soil was improved through using Flu@ZIF-8-OS/CMCS. Furthermore, the release properties, biological activity, degradability and safety to soil organisms of Flu@ZIF-8-OS/CMCS was determined. The addition of ZIF-8 significantly improved the film's ability to retard the release of Flu, while the Flu@ZIF-8-OS/CMCS has good soil degradability. In vitro antifungal assays and pot experiments demonstrated excellent inhibitory activity against Fusarium oxysporum f. sp. Lycopersici. Flu@ZIF-8-OS/CMCS caused only 13.33 % mortality of earthworms within 7 d. This research provides a new approach to reducing microplastic pollution and effectively managing soil-borne diseases.

The adsorption and release mechanism of different aged microplastics toward Hg(II) via batch experiment and the deep learning method

Aged microplastics are ubiquitous in the aquatic environment, which inevitably accumulate metals, and then alter their migration. Whereas, the synergistic behavior and effect of microplastics and Hg(II) were rarely reported. In this context, the adsorptive behavior of Hg(II) by pristine/aged microplastics involving polystyrene, polyethylene, polylactic acid, and tire microplastics were investigated via kinetic (pseudo-first and second-order dynamics, the internal diffusion model), Langmuir, and Freundlich isothermal models; the adsorption and desorption behavior was also explored under different conditions. Microplastics aged by ozone exhibited a rougher surface attached with abundant oxygen-containing groups to enhance hydrophilicity and negative surface charge, those promoted adsorption capacity of 4-20 times increment compared with the pristine microplastics. The process (except for aged tire microplastics) was dominated by a monolayer chemical reaction, which was significantly impacted by pH, salinity, fulvic acid, and co-existing ions. Furthermore, the adsorbed Hg(II) could be effectively eluted in 0.04% HCl, simulated gastric liquids, and seawater with a maximum desorption amount of 23.26 mg/g. An artificial neural network model was used to predict the performance of microplastics in complex media and accurately capture the main influencing factors and their contributions. This finding revealed that aged microplastics had the affinity to trap Hg(II) from freshwater, whereafter it released the Hg(II) once transported into the acidic medium, the organism's gastrointestinal system, or the estuary area. These indicated that aged microplastics could be the sink or the source of Hg(II) depending on the surrounding environment, meaning that aged microplastics could be the vital carrier to Hg(II).

Natural aging and adsorption/desorption behaviors of polyethylene mulch films: Roles of film types and exposure patterns

Polyethylene (PE) mulch films are an important source of microplastics (MPs) in agricultural soils, which may further affect the bioavailability of coexisting pollutants. In this study, white (WM), black (BM), and silver-black (SM) PE mulch films were aged on the soil surface and under soil burial to simulate the two exposure patterns of abandoned mulch films in the field. Results indicated that the soil-surface exposure induced more pronounced aging characteristics, and WM seemed the most susceptible. Serious surface deterioration by aging led to a drastic decrease in the tensile properties of the films, suggesting the tendency to fragment. Oxygen-containing functional groups were generated on the film surfaces, with oxygen/carbon ratios increasing by up to 29 times, which contributed to the prominent increase in Pb adsorption on the film-derived MPs. Additionally, the film surface became more hydrophobic when exposed to the soil surface but more hydrophilic in the soil-burial exposure, which was in agreement with the change in triclosan adsorption, i.e., promotion and suppression, respectively. Aging generally decreased the desorption potential of the adsorbed pollutants in simulated gastrointestinal solutions due to increased interactions. By comparison, exposure patterns were revealed to be the critical factor for these changes, regardless of film types.

Deciphering survival strategies: Oxidative stress and microbial interplay in Eisenia fetida under tetracycline contamination

Soil contamination resulting from residual antibiotics presents a pressing need to understand the survival mechanisms of soil organisms in polluted environments. This study focused on Eisenia fetida, and tetracycline stress experiments were conducted in a controlled environment using sterile artificial soil. The stress concentration ranged from 0 to 600 mg/kg, and stress cycles lasted either 10 or 30 days. The objective of this study was to assess the effects of oxidative stress and the changes in microbial communities both within and outside the earthworms. A comprehensive mathematical model was developed to elucidate the responses of organisms following exposure to stress utilizing factor analysis, grey relational analysis, and hierarchical entropy weight analysis. Under tetracycline stress, the initial stage (1-3 days) exhibited a coordinated regulation of oxidative stress and microbial communities in the soil with the assistance of CAT and GPX enzymes. The subsequent stage (4-5 days) further emphasized the influence of soil microbial communities. A notable "feedback regulation" of soil microbial communities on oxidative stress was observed during the third stage (6-8 days). Earthworms maintained a metabolic balance in the fourth stage (9-10 days). In the long term, the stress-induced a self-detoxification mechanism within soil microbial communities, which collaborated with GPX to respond to oxidative stress.

Polyethylene microplastic can adsorb phosphate but is unlikely to limit its availability in soil

In plant growth experiments, the presence of microplastics (MPs) often reduces plant growth. We conducted laboratory experiments to investigate the potential of microplastics to adsorb the major soil nutrient phosphate; adsorption to MPs was then compared to adsorption to soil. Adsorption experiments used two contrasting soils, pristine high density polyethylene and artificially weathered material (the same material but exposed to 185 nm UV light for 420 h over 105 days), phosphate solutions (dissolved KH2PO4) ranging from 0.2 to 200 mg L-1 and a solid (g) to liquid (mL) ratio of 1: 150 at different values of pH (2-12) and different concentrations of background electrolyte (0.00-0.10 M NaNO3). The adsorption data were best fitted to linear and Freundlich isotherms. In initial experiments where pH was not fixed and with a background electrolyte of 0.10 M NaNO3, Kd values ranged from 3.37 to 27.65 L kg-1, log Kf from 1.21 to 1.96 and 1/n from 0.36 to 0.84. Exposure of the MP to 185 nm UV radiation led to the appearance of a C=O functional group in the MP; the partition coefficient Kd, calculated from the linear isotherm did not increase but the logKf value derived from fits to the Freundlich isotherm increased by a factor of 1.5. Kd values for soils were 3-7.5 times greater than those for MPs and log Kf values 1.1-1.7 greater. In the experiments in which initial pH and ionic strength were varied, adsorption was similar across all treatments with adsorption parameters for the higher organic content soil sometimes having the highest values and the pristine microplastic the lowest. In the desorption experiments most of the adsorbed phosphate desorbed. Overall our findings indicate that despite their ability to adsorb phosphate, MPs are unlikely to control the fate and behaviour of phosphate in soil.

A bibliometric analysis of global research hotspots and progress on microplastics in soil‒plant systems

Plastic pollution has become a global and persistent challenge, posing threats to ecosystems and organisms. In recent years, there has been a rapid increase in scientific research focused on understanding microplastics in the soil‒plant system. This surge is primarily driven by the direct impact of microplastics on agricultural productivity and their association with human activities. In this study, we conducted a comprehensive bibliometric analysis to provide an overview of the current research on microplastics in soil‒plant systems. We systematically analysed 192 articles and observed a significant rise in research interests since 2017. Notably, China has emerged as a leading contributor in terms of published papers, closely followed by Germany and the Netherlands. Through co-authorship network analysis, we identified 634 different institutions that participated in publishing papers in this field, with the Chinese Academy of Sciences having the most collaborations. In the co-occurrence keyword network, we identified four clusters focusing on the diversity of microplastics within the agroecosystem, transportation, and quantification of microplastics in soil, analysis of plastic contamination type and impact, and investigation of microplastic phytotoxicity. Furthermore, we identified ten research priorities, categorized into the effects of microplastics in "soil" and "plant". The research hotspots were found to be the effect of microplastics on soil physicochemical properties and the synergistic phytotoxicity of microplastics with other pollutants. Overall, this bibliometric analysis holds significant value, serving as an important reference point and offering valuable suggestions for future researchers in this rapidly advancing field.

Soils in distress: The impacts and ecological risks of (micro)plastic pollution in the terrestrial environment

Plastics have revolutionised human industries, thanks to their versatility and durability. However, their extensive use, coupled with inadequate waste disposal, has resulted in plastic becoming ubiquitous in every environmental compartment, posing potential risks to the economy, human health and the environment. Additionally, under natural conditions, plastic waste breaks down into microplastics (MPs<5 mm). The increasing quantity of MPs exerts a significant burden on the soil environment, particularly in agroecosystems, presenting a new stressor for soil-dwelling organisms. In this review, we delve into the effects of MP pollution on soil ecosystems, with a specific attention to (a) MP transport to soils, (b) potential changes of MPs under environmental conditions, (c) and their interaction with the physical, chemical and biological components of the soil. We aim to shed light on the alterations in the distribution, activity, physiology and growth of soil flora, fauna and microorganisms in response to MPs, offering an ecotoxicological perspective for environmental risk assessment of plastics. The effects of MPs are strongly influenced by their intrinsic traits, including polymer type, shape, size and abundance. By exploring the multifaceted interactions between MPs and the soil environment, we provide critical insights into the consequences of plastic contamination. Despite the growing body of research, there remain substantial knowledge gaps regarding the long-term impact of MPs on the soil. Our work underscores the importance of continued research efforts and the adoption of standardised approaches to address plastic pollution and ensure a sustainable future for our planet.