Macro, meso, micro and nanoplastics in horticultural soils in Argentina: Abundance, size distribution and fragmentation mechanism

An integrated evaluation of potentially toxic elements and microplastics in the highland soils of the northeastern Qinghai-Tibetan Plateau

As gateways to the scenic Qinghai-Tibetan Plateau (QTP), some underexplored five grassland (GLs) and three farmland (FLs) soil locations of northeastern counties were investigated. Preliminary detection showed that in the grazing and agricultural soils, elemental concentrations (Fe>Zn>Cr>Cu>Pb>Co>As>Cd) were up to 37 and 10 mg/g, but within the China soil standards, except Cd, while microplastics (MPs) abundances were 200-3640 and 280-973 particles/kg, respectively. Polypropylene (PP: 40-55 %) dominated in GLs mostly as fragments, whereas polyethylene (PE: 72-92 %) in FLs as films. Adsorption results demonstrated that potentially toxic elements (PTEs)-MPs' interaction may chiefly depend on their types and speciation in soils, the physiochemical structure of MPs, and surrounding conditions. The integrated two-dimensional risk assessment categorized three of five GLs under Risk Level VI (high pollution), whereas one of three FLs displayed Risk Level III (moderate pollution). Correlation analysis revealed that altitude, organic matter, soil clay content, and precipitation significantly affected PTEs (p ≤ 0.01), whereas MPs were influenced by altitude, soil clay content, precipitation (p ≤ 0.001), and population density (p ≤ 0.05). Comparison with low-land soils globally designated QTP as a vulnerable region to MPs due to the expanding development. Overall, our study provides a data set to understand the pollution scenario of highlands for its targeted management.

The plastic size spectra: Assessing the size structure of plastic particles across the land-water ecotone

Plastics of different types and sizes pollute most of Earth's environmental systems. Here, we used size spectra analysis (SSA) to evaluate and characterize size-frequency patterns of plastic pollution across the land-water ecotone of 20 urban lakes. We first tested the general hypothesis that plastic particles in the environment reflect a detectable and inverse size-frequency pattern as large plastics regularly breakdown in increasingly smaller pieces. To further evaluate the utility of SSA, we tested whether slope (λ) and intercept (Γ) coefficients from lake-specific models were sensitive to distinguish trends among lake zones. Overall, our findings detected an overall inverse relationship between particle counts (#/m2) and binned particle length, confirming the presence of a plastic size spectra for all aggregated data. We further improved the explanatory power of SSA models by (1) separating thin films from thicker plastic fragments and by (2) assessing sampling environments (i.e., upland vegetation, shoreline sediments, offshore sediments) separately. Doing so revealed statistically distinct size-frequency gradients that tracked the shift from land to water for both films and fragments. Analysis and comparison of SSA models also confirmed that coefficients were sensitive enough to detect differences among lake zones. All told, the SSA framework was successfully used to detect and describe several patterns of plastic pollution in the environment. This analytic framework holds promise for developing hypothesis-driven studies to all plastics rather than focusing on small or large particles.

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

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

Co-Exposure to Polystyrene Microplastics and Bisphenol A Contributes to the Formation of Liver Fibrosis in Mice through Inhibition of the BMAL1/E-Cad Signaling Pathway

The food safety risks posed by exposure to polystyrene microplastics (PS-MPs) and bisphenol A (BPA) have become an issue worldwide. However, the toxic effects of PS-MPs and BPA coexposure on the mammalian liver remain elusive. In this study, we found that PS-MPs and BPA coexposure have synergistic toxic effects on AML12 cells and the mouse liver. Histopathological staining revealed excessive accumulation of the extracellular matrix in the coexposure liver. Co-exposure to PS-MPs and BPA downregulated Bmal1 and E-cad both in vitro and in vivo. Additionally, Bmal1-/- AML12 cells and liver-specific Bmal1-/- mice exhibited significantly reduced E-cad levels, with no significant reduction under PS-MPs and BPA coexposure. Notably, overexpression of BMAL1 and CLOCK significantly enhanced luciferase activity driven by the E-cad gene intron region (containing an E-box cis-element). These results demonstrated that coexposure to PS-MPs and BPA contributed to the development of liver fibrosis by inhibiting the BMAL1/E-cad signaling pathway.

Mesoplastics: A Review of Contamination Status, Analytical Methods, Pollution Sources, Potential Risks, and Future Perspectives of an Emerging Global Environmental Pollutant

Mesoplastics are emerging environmental pollutants that can pose a threat to the environment. Researching mesoplastics is crucial as they bridge the gap between macroplastics and microplastics by determining their role in plastic fragmentation and pathways, as well as their ecological impact. Investigating mesoplastic sources will help develop targeted policies and mitigation strategies to address plastic pollution. These pollutants are found across aquatic, terrestrial, and agricultural ecosystems. Unlike microplastics, mesoplastics are reviewed in the scientific literature. This paper focuses on existing published research on mesoplastics, determining the trends and synthesizing key findings related to mesoplastic pollution. Research primarily focused on marine and freshwater ecosystems, with surface water and beach sediments being the most studied compartments. Mesoplastics research often offers baseline data, with increased publications from 2014 to 2024, particularly in East Asia. However, certain ecosystems and regions remain underrepresented. Also, mesoplastics can disrupt ecosystems by degrading biodiversity, contaminating soils and waters, and affecting food chains. Mesoplastics can also become vectors for additives and pathogenic microorganisms, highlighting their environmental risks. Various factors influence mesoplastics' prevalence, including anthropogenic and non-anthropogenic activities. With this, future research should expand into less-studied ecosystems and regions, explore mesoplastic interactions with pollutants and organisms, and promote public awareness, education, and policy measures to reduce plastic use and mitigate pollution globally.

Polyethylene fragments in Argentinean horticultural soils: Environmental transformation to a composite material

Polyethylene macro, meso, and microplastics collected from horticultural soils in Moreno, Buenos Aires, Argentina, were studied to understand their physicochemical transformations after environmental exposure. These plastics contained mechanically stable compounds of Si (1.2-4.0 %), Al (0.91-1.5 %), and Fe (0.64-2.2 %), likely due to soil clay particles adhering to the plastic. The plastics' surfaces were oxidized, with high carbonyl (0.05-0.23) and hydroxyl (1.6-2.7) indices. Weathering led to thinner, rougher surfaces with increased contact angles due to the presence of clay and polar organic groups. Scanning electron microscopy (SEM) showed cracks and particles on the surfaces, while atomic force microscopy (AFM) revealed roughness increased from 0.44 nm in pristine polyethylene (p-PE) to 1.60 nm in weathered samples. Heavy metal sorption experiments showed that the weathered plastics absorbed significantly more Ni2+ and Pb2+ than unweathered PE (4.5 times for Ni2+ and 11 times for Pb2+). After removing clay with hydrofluoric acid, the plastics still retained the same amount of these metals, suggesting that the sorption occurred mainly on the modified plastic surface rather than the clay. Arsenate tests indicated that the plastics selectively absorbed cationic metals. This study also developed a simple ATR-FTIR method for quantifying silicate on polyethylene surfaces, contributing to an understanding of soil-derived particle interactions with plastic in agricultural settings.

Phenotypic and Gene Expression Alterations in Aquatic Organisms Exposed to Microplastics

The use of plastics, valued for its affordability, durability, and convenience, has grown significantly with the advancement of industry. Paradoxically, these very properties of plastics have also led to significant environmental challenges. Plastics are highly resistant to decomposition, resulting in their accumulation on land, where they eventually enter aquatic environments, due to natural processes or human activities. Among these plastics, microplastics, which are tiny plastic particles, are particularly concerning when they enter aquatic ecosystems, including rivers and seas. Their small size makes them easily ingestible by aquatic organisms, either by mistake or through natural feeding behaviors, which poses serious risks. Moreover, microplastics readily adsorb other pollutants present in aquatic environments, creating pollutant complexes that can have a synergistic impact, magnifying their harmful effects compared to microplastics or pollutants acting alone. As a result, extensive research has focused on understanding the effects of microplastics on aquatic organisms. Numerous studies have demonstrated that aquatic organisms exposed to microplastics, either alone or in combination with other pollutants, exhibit abnormal hatching, development, and growth. Additionally, many genes, particularly those associated with the antioxidant system, display abnormal expression patterns in these conditions. In this review, we examine these impacts, by discussing specific studies that explore changes in phenotype and gene expression in aquatic organisms exposed to microplastics, both independently and in combination with adsorbed pollutants.

Macro- and micro-plastic accumulation in soils under different intensive farming systems: A case study in Quzhou county, the North China Plain

The macroplastics (MaPs) and microplastics (MiPs) polluting agricultural soils raise great concerns. Unfortunately, scientists know little about the occurrence of MaPs/MiPs in soil among different farming systems. In this study, we analyzed MaPs/MiPs in soils (0-30 cm) collected from six different farming systems (wheat-maize rotations, cotton, vegetables, permanent orchards, greenhouses with and without mulching) in Quzhou county, the North China Plain, by using fluorescence microscope and micro-Fourier transform infrared spectroscopy. The results showed that the abundance of MaPs and MiPs ranged from 0.2 to 46.8 kg ha-1, and 4.1 × 103-3.7 × 104 items kg-1, respectively. The prominent colors of the MaPs were white and black. The predominant shape, size and chemical composition of soil MiPs were fragments (45-62%), <1 mm (98-99%), and polyethylene (38-43%), respectively. MaPs were mainly detected in the 0-10 cm soil layer. MiP abundance in the 0-10 cm soil layer was significantly higher than that in the 20-30 cm soil layers among different farming systems, except for the fields with wheat-maize rotations and permanent orchards (p < 0.05). Overall, cotton fields showed the highest MaP and MiP abundance, followed by vegetable fields and orchards. Redundancy analysis revealed that tillage practices and plastic film management greatly influence the size distribution of MiPs. A strong negative correlation between large-sized plastic fractions (0.2-1 mm) and tillage frequency was tested while the years of application of plastic films and the abundance of plastic residues showed a strong positive correlation with small-sized plastic fractions (<0.2 mm). Our findings conclude that agricultural mulch films are an important source of MaPs and MiPs in agricultural soil and distributions are strongly influenced by agricultural management practices and farming systems. Further studies should take farming systems and farming practices into account, thereby exploring the potential mechanisms of plastic fragmentation and granularization in agricultural soil.

Factors that influence the migration of sorbed pesticides in polyethylene and biodegradable mesoplastics

Trifluralin, Chlorpyrifos, and Procymidone migration performance from polyethylene (PE) and biodegradable (Mater-Bi: M-B) mulching films was examined. Desorption of pesticides from PE and M-B was studied using soil-plastic microcosms, considering temperature, soil humidity, and mulching film type as experimental variables. Trifluralin and Chlorpyrifos desorption was higher for PE than for M-B under all experimental conditions. In both cases, as the temperature increased from 25 °C to 40 °C, pesticide migration also increased, whereas as the soil humidity raised from 30% to 60%, pesticide desorption decreased. In the case of Procymidone, migration from PE and M-B at 25 °C was similar under both soil moisture conditions. Migration percentages were similar for both mulch films at 40 °C and 30% soil humidity. However, at higher soil moisture (60%), migration from M-B was greater than from PE. A linear relationship was observed between the percentage of migration and the vapor pressure of the pesticides. In all cases, migration increased with higher vapor pressure, indicating a possible migration mechanism in the vapor phase. Pesticide migration increased at high temperatures (40 °C). The effect of soil humidity in reducing pesticide migration was more significant at lower levels (30%). In addition, the mesoplastic sorption of pesticides in soil columns was studied using PE and M-B films. While the recoveries for Trifluralin, Chlorpyrifos, and Procymidone in the PE films were 0.05% ± 0.01%, 0.13% ± 0.03%, and non-detectable, the recoveries for M-B were: 0.49% ± 0.07%, 0.31% ± 0.09%, and 0.17% ± 0.10%, respectively, indicating that M-B was a better adsorbent than PE in all cases. This behavior should be considered in combination with the lower migration percentages observed for this type of mulching film in the microcosm experiments. These results could indicate a potential carrier effect of pesticide on biomesoplastic in the environment.

Global soil microplastic assessment in different land-use systems is largely determined by the method of analysis: A meta-analysis

Although microplastics (1 μm - 5 mm, MP) are increasingly recognised as a novel entity of pollutants, we still lack a basic understanding of their prevalence in different terrestrial environments. Here, we aimed at performing comparisons of MP concentrations (items kg-1) in different agro-ecosystems, with specific focus on input pathways and land uses, while accounting for the plethora of method variations available, such as analysed MP sizes, sampling depths, density separation solutions, as well as removal of organic matter. We found that the current global means of MP loads, from 89 studies (553 sites), benchmarks 2900 ± 7600 MP items kg-1 soil, substantially more than the global median of 480 MP items kg-1. Roughly 81 % of the studies were conducted in Asia; hence, continent-wide comparisons are still hampered by low study numbers for most regions. Maximum MP numbers were found for soils under both greenhouses and plastic mulching (5200 ± 8300 items kg-1), followed by arable soils with sludge amendments (3700 ± 8800 items kg-1), surprisingly without evidence of elevated MP loads in horticultural fields relative to other agricultural management practices. Intriguingly, global MP loads significantly increased with decreasing levels of urbanisation, i.e., they were highest in rural areas. Yet, quantitative comparisons among sites are biased by the methodology selected for MP analyses. Apart from inconsistencies in sampling depth and size of screened MP particles, across all sites and treatments, largest MP loads were commonly found when using high-density solutions rather than low-density ones, and when soil organic matter removal was performed after, and not before, the density separation step.

Environmental fate of microplastics and common polymer additives in non-biodegradable plastic mulch applied agricultural soils

Numerous studies have been conducted to investigate the impact of microplastics on soil eco-system, yet little attention has been given to the specific effects of mulch microplastics and the leaching of plastic additives from mulch films. This review inspects the propensity of commonly used plastic additives in mulch films, such as Di(2-ethylhexyl) phthalate (DEHP), bisphenol A (BPA), and benzophenones (BPs), to migrate into soils and pose potential risks to soil biota. Further, we highlight the degradation of non-biodegradable plastic mulch films over time, which leads to an increase in the release of plastic additives and microplastics into agricultural soils. DEHP has been detected in high concentrations for example 25.2 mg/kg in agricultural soils, indicating a potential risk of uptake, translocation and accumulation in plants, ultimately altering soil physicochemical properties and affecting soil microflora and invertebrates. The review also explores how exposure to ultraviolet (UV) radiation and microbial activities accelerates the weathering of mulch films. Moreover, the resultant plastic additives and mulch microplastics can lead to genotoxicity and growth inhibition in earthworms (Eisenia fetida) and negatively impact the soil microbiome. Despite the significant implications, there has been a lack of comprehensive reviews comparing the effects of non-biodegradable mulch film additives on agricultural soil flora and fauna. Therefore, this review addresses the knowledge gaps providing a bibliometric analysis and eco-toxicological evaluation, discussing the challenges and future perspectives regarding mulch plastic additives and microplastics, thus offering a comprehensive understanding of their impact.

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

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

The Plasticene era: Current uncertainties in estimates of the hazards posed by tiny plastic particles on soils and terrestrial invertebrates

Plastics are ubiquitous in our daily life. Large quantities of plastics leak in the environment where they weather and fragment into micro- and nanoparticles. This potentially releases additives, but rarely leads to a complete mineralization, thus constitutes an environmental hazard. Plastic pollution in agricultural soils currently represents a major challenge: quantitative data of nanoplastics in soils as well as their effects on biodiversity and ecosystem functions need more attention. Plastic accumulation interferes with soil functions, including water dynamics, aeration, microbial activities, and nutrient cycling processes, thus impairing agricultural crop yield. Plastic debris directly affects living organisms but also acts as contaminant vectors in the soils, increasing the effects and the threats on biodiversity. Finally, the effects of plastics on terrestrial invertebrates, representing major taxa in abundance and diversity in the soil compartment, need urgently more investigation from the infra-individual to the ecosystem scales.