Microplastics are ubiquitous and increasing in soil of a sprawling urban area, Phoenix (Arizona)

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.

Screening for microplastics in agricultural soils: Applying green chemistry principles in extraction and analysis

In recent years, microplastic (MP) pollution has garnered significant attention owing to its ability to permeate various ecosystems, including soil. These particles can infiltrate the environment, either directly or through the degradation of larger plastic items. Despite growing concerns, standardized methods for quantification are still lacking. This study aimed to screen for the presence of MPs in agricultural soils while incorporating green analytical principles in the methodology. A density separation followed by centrifugation was employed, based on the principles of the QuEChERS extraction method. This approach minimized sample quantities, reagent consumption, and waste production, ensuring efficient extraction and analysis. Recovery tests using certified soils spiked with pristine MPs, specifically polystyrene, polypropylene (PP), and ethylene-vinyl acetate for larger MPs (3-5 mm), and low-density polyethylene, polyamide 6, and tire wear particles for smaller MPs (15-300 μm), achieved recovery levels exceeding 69% for smaller MPs and over 91% for larger particles. Spectroscopic analysis revealed slight alterations in the Raman spectra of MPs after extraction. Transitioning to agricultural soil analysis has revealed challenges, including spectral interferences. Nine mesoplastics (5-20 mm) were detected, predominantly consisting of PP and polyethylene (PE), along with seven MPs, three of which were individually identified as PE-based, while the remainder were inconclusive, including one fiber. The evaluation of the method's sustainability using the Analytical Eco-Scale and Analytical Greenness Calculator Metric (AGREE), with scores of 82 out of 100 and 0.66 out of 1, respectively, demonstrated its potential as a reliable approach to MP analysis in soils. This study highlights the potential of integrating green analytical chemistry principles into MP extraction methodologies and emphasizes the value of the proposed QuEChERs-based approach for improving the sustainability and efficiency of MP monitoring in agricultural soils.

Microplastics in soil: A comprehensive review of occurrence, sources, fate, analytical techniques and potential impacts

Through their accumulation in soils, microplastics have recently become a matter of concern. The aim of this review is to assemble and investigate the recent studies about microplastics in soil by focusing on their sources, occurrence, fate in soil, and analytical methods. The objective is also to clarify and elucidate their potential impacts on soil fauna, plants and microorganisms. In this paper, articles reporting the quantity of microplastics and their characteristics in soil at 62 sites situated across 17 countries were reviewed. The land type, microplastic abundances, types and sizes were compared. We summarized and discussed the sampling and analytical methods used and the variation of microplastic concentration according to their sources. The data showed that microplastic in soil from available global studies ranged from 0 to 3573×103 particles kg-1, with major dominance of polyethylene, polystyrene and polypropylene found in 50, 37 and 32 studies, respectively. The data analysis showed the high migration of small particles, spherical shape with high polymer density in the major studies. We also described the mechanisms controlling the vertical transport of microplastics: agricultural activity (plowing: at a depth between 10 cm (very shallow plowing) and 40 cm (deeper soil tillage)), bioturbation by soil organisms and plants, and leaching that can lead to the contamination of the groundwater. This review elucidated the behavior and fate of microplastics within the soil, serving as a reference for upcoming studies aimed at devising solutions to mitigate the toxicity associated with microplastics in soil.

Mutual Effects and Uptake of Organic Contaminants and Nanoplastics by Lettuce in Co-Exposure

Organic contaminants, such as pesticides and pharmaceuticals, are commonly found in agricultural systems. With the growing use of plastic products, micro- and nanoplastics (MNPs) are increasingly detected in these agricultural systems, necessitating research into their interactions and joint effects to truly understand their impact. Unfortunately, while there has been a long history of research into the uptake of organic pollutants by plants, similar research with MNPs is only beginning, and studies on their mutual effects and plant uptake are extremely rare. In this study, we examined the effects of three agriculturally relevant organic pollutants with distinctive hydrophobicity as measured by log KOW (trimethoprim: 0.91, atrazine: 2.61, and ibuprofen: 3.97) and 500 nm polystyrene nanoplastics on their uptake and accumulation by lettuce at two different salinity levels. Our results showed that nanoplastics increased the shoot concentration of ibuprofen by 77.4 and 309% in nonsaline and saline conditions, respectively. Alternatively, organic co-contaminants slightly lowered the PS NPs uptake in lettuce with a more pronounced decrease in saline water. These results underscore the impactful interactions of hydrophobic organic pollutants and increasing MNPs on a dynamic global environment.