Microplastic occurrence in urban and industrial soils of Ahvaz metropolis: A city with a sustained record of air pollution

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.

A comprehensive review of urban microplastic pollution sources, environment and human health impacts, and regulatory efforts

Microplastic (MP) pollution in urban environments is a pervasive and complex problem with significant environmental and human health implications. Although studies have been conducted on MP pollution in urban environments, there are still research gaps in understanding the exact sources, regulation, and impact of urban MP on the environment and public health. Therefore, the goal of this study is to provide a comprehensive overview of the complex pathways, harmful effects, and regulatory efforts of urban MP pollution. It discusses the research challenges and suggests future directions for addressing MPs related to environmental issues in urban settings. In this study, original research papers published from 2010 to 2024 across ten database categories, including PubMed, Google Scholar, Scopus, and Web of Science, were selected and reviewed to improve our understanding of urban MP pollution. The analysis revealed multifaceted sources of MPs, including surface runoff, wastewater discharge, atmospheric deposition, and biological interactions, which contribute to the contamination of aquatic and terrestrial ecosystems. MPs pose a threat to marine and terrestrial life, freshwater organisms, soil health, plant communities, and human health through ingestion, inhalation, and dermal exposure. Current regulatory measures for MP pollution include improved waste management, upgraded wastewater treatment, stormwater management, product innovation, public awareness campaigns, and community engagement. Despite these regulatory measures, several challenges such as; the absence of standardized MPs testing methods, MPs enter into the environment through a multitude of sources and pathways, countries struggle in balancing trade interests with environmental concerns have hindered effective policy implementation and enforcement. Addressing MP pollution in urban environments is essential for preserving ecosystems, safeguarding public health, and advancing sustainable development. Interdisciplinary collaboration, innovative research, stringent regulations, and public participation are vital for mitigating this critical issue and ensuring a cleaner and healthier future for urban environments and the planet.

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.

Distribution of microplastics in (sub)urban soils of Serbia and Cd, As, and Pb uptake by Capsella bursa-pastoris (L.) Medik

Omnipresent in terrestrial ecosystems, microplastics (MPs) represent a hazard to soil biota and human health, while their relationship with other environmental contaminants remains poorly acknowledged. This study investigated MPs prevalence in (sub)urban soils of Serbia and its impact on Cd, As, and Pb mobility in the soil-medicinal plant Capsella bursa-pastoris (L.) Medik system. Soil physicochemical parameters (pH, Eh, SOM, and texture) were analyzed alongside the Cd, As, and Pb pseudo-total (aqua regia) and phytoavailable (EDTA) contents. Toxic elements' concentrations in soil fractions and C. bursa-pastoris roots and shoots were determined by inductively coupled plasma optical emission spectroscopy (ICP-OES). Pseudo-total Cd, As, and Pb contents in soils ranged from 0.16 to 2.23 μg g-1, 2.00-36.92 μg g-1, and 0.18-65.54 μg g-1, respectively. Using an optimized density separation method with 30% H2O2 and 5% NaClO, we found an average abundance of 489 MPs per kg of soil. ATR-FTIR spectroscopy confirmed the presence of seven polymer types, whereby the main contributors were polystyrene (PS) - 28.57% and cardanol prepolymer (PCP) - 23.81%. The dominant associated pollution sources were road networks and industrial activities. Spearman correlation analysis revealed the interconnection among soil MPs, physicochemical variables, and Cd, As, and Pb mobility. We identified significant positive correlations between MPs' abundance and phytoavailable concentrations of Cd, As, and Pb (ρ = 0.82, 0.95, and 0.63). Moreover, soil MPs strongly positively correlated with Cd contents in roots (ρ = 0.61) and shoots of C. bursa-pastoris (ρ = 0.65). These findings underscore the synergistic effects of MPs and toxic metals in urban environmental pollution, with possible implications for human health. Further research is required to deepen our understanding of the impact of MPs on element mobility in complex plant-soil systems and to elucidate the broader consequences of induced alterations.

Not only in the crowd: Benthic litter characterization in a low population density area still reveals widespread pollution and local malpractices

Various anthropogenic activities affect marine coastal habitats, leading to heavy litter pollution. However, whilst high litter concentrations are nowadays common in the proximity of metropolises, few studies investigated the magnitude of this phenomenon around coastal villages and small towns. We hereby characterized the benthic litter occurring in the trawlable grounds of the Gulf of Policastro (Tyrrhenian Sea, central-western Mediterranean), a low population density area that becomes a popular tourist destination during summer. We furthermore tested differences between two depths (∼100-200 and ∼500-600 m) and the impact of tourism on the shallower waters. The area was characterized by a litter abundance of 651.12 ± 130.61 item/km2, with plastic being almost totalitarian (93%). The shallower waters hosted two-thirds of the litter found. Almost all (∼95%) the litter items had a land-based origin, while the sea-based litter was mostly found at higher depths. About 14% of the litter was found to be fouled, with the development of litter-associated communities that somehow mimic the natural ones living on hard substrates. The higher litter presence noticed during the touristic peak (July-August) suggests that tourism is an important source of local litter, although it contributed to the local accumulation in a synergic way with other factors. The majority of the litter items presumably originated from the nearby coastline, while the deeper waters were or are used as a dumping site by the local trawling fleet. The discovery of such a critical waste accumulation and management in a somehow remote area contributes to widen the perspectives on the presence of benthic litter mostly in territories characterized by wide anthropization. Moreover, it confirms that appropriate local policies and communication plans are urged even at a regional level to stimulate citizen consciousness and mitigate the ever growing litter pollution.

Unveiling microplastic's role in nitrogen cycling: Metagenomic insights from estuarine sediment microcosms

Marine microplastics (MPs) pollution, with rivers as a major source, leads to MPs accumulation in estuarine sediments, which are also nitrogen cycling hotspots. However, the impact of MPs on nitrogen cycling in estuarine sediments has rarely been documented. In this study, we conducted microcosm experiment to investigate the effects of commonly encountered polyethylene (PE) and polystyrene (PS) MPs, with two MPs concentrations (0.3% and 3% wet sediment weight) based on environmental concentration considerations and dose-response effects, on sediment dissolved oxygen (DO) diffusion capacity and microbial communities using microelectrode system and metagenomic analysis respectively. The results indicated that high concentrations of PE-MPs inhibited DO diffusion during the mid-phase of the experiment, an effect that dissipated in the later stages. Metagenomic analysis revealed that MP treatments reduced the relative abundance of dominant microbial colonies in the sediments. The PCoA results demonstrated that MPs altered the microbial community structure, particularly evident under high concentration PE-MPs treatments. Functional analysis related to the nitrogen cycle suggested that PS-MPs promoted the nitrification, denitrification, and DNRA processes, but inhibited the ANRA process, while PE-MPs had an inhibitory effect on the nitrate reduction process and the ANRA process. Additionally, the high concentration of PE-MPs treatment significantly stimulated the abundance of genus (Bacillus) by 34.1% and genes (lip, pnbA) by 100-187.5% associated with plastic degradation, respectively. Overall, in terms of microbial community structure and the abundance of nitrogen cycling functional genes, PE- and PS- MPs exhibit both similarities and differences in their impact on nitrogen cycling. Our findings highlight the complexity of MP effects on nitrogen cycling in estuarine sediments and high concentrations of PE-MP stimulated plastic-degrading genus and genes.

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.

Assessment of microplastic contamination in some commercial fishes of the southern Caspian Sea and its potential risks

This study examined the occurrence of microplastics (MPs) in the gastrointestinal tract (GIT) of 384 fishes classified into four species from 11 sites in 2022 from the southern part of the Caspian Sea. GITs of fishes were collected and digested in H2O2 and KOH at 45 °C for 72 h. After filtration, extracted MPs were observed under a stereomicroscope, and selected MP particles were identified using FTIR. Presence of MPs was 68.98% in the GIT of the investigated fish. The mean abundance of MPs was 5.9 ± 0.9 MPs/GIT in Rutilus kutum, 9.2 ± 1.2 MPs/GIT in Chelon auratus, 3.6 ± 0.7 MPs/GIT in Alosa braschnikowi, and 2.7 ± 0.5 MPs/GIT in Vimba vimba. The predominant form of MPs was fiber (58.21%), followed by fragment (34.77%). Black (34.4%), white (19.07%), and blue (14.58%) were the most frequently detected colors of MPs. Overall, 6 MP polymers were identified, dominantly polypropylene (42.86%), polystyrene (17.86%), and cellophane (14.28%). The western part of the Caspian Sea (mostly tourist spots and urban areas) showed more MP pollution in fish compared to the eastern part. Polymer hazard index (PHI) revealed alarming microplastic contamination in the southern Caspian Sea. The PHI value of the present study showed that PES (PHI = 8403.78) and PS (PHI = 535.80) were "Extreme danger" and "Danger" risk categories, respectively.

Influence of the geographic location and house characteristics on the concentration of microplastics in indoor dust

Microplastics (MPs) are known for their ubiquity, having been detected in virtually any environmental compartment. However, indoor MPs concentrations are poorly studied despite being closely related to human exposure. The present study aims to evaluate the presence of MPs in settled atmospheric dust in 60 houses distributed in 12 districts of the metropolitan city of Lima, Peru, and investigate the influence of their geographical location and house characteristics. MPs concentration ranged from 0.01 to 33.9 MPs per mg of dust. Fibers and blue were the most frequent shape and color (98 % and 69 %, respectively). Also, 82 % of the particles were between 500 μm - 5 mm in size. A higher concentration of MPs was identified in the center-south of the city. The houses located on the highest floors (levels 4 to 13 to ground) displayed higher concentrations. MPs were primarily composed of polyester (PET), polypropylene (PP), and ethylene-vinyl acetate (EVA), among others. The polymers identified suggest that MPs derived from the fragmentation of components frequently found in houses, such as synthetic clothing, food storage containers, toys, carpets, floors, and curtains. The incorporation of MPs from the outside into dwellings is not ruled out. Future studies should evaluate the influence of consumption habits and housing characteristics on the abundance of MPs.

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

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

An evaluation on microplastic accumulations in Turkish soils under different land uses

Microplastic (MP) pollution is now widely reported in soil ecosystems. However, the level of this pollution in soil ecosystems has not been sufficiently elucidated. Moreover, there is little understanding of how land use conditions affect the occurrence and distribution of MPs in soils. Therefore, this study examined 55 soil samples (44 agricultural and 11 urban) from the Mediterranean, Aegean, and Marmara regions of Türkiye, representing both agricultural and urban land uses. The samples were analyzed for MP distribution characteristics, such as abundance, shape, size, color, and type. Different types of MPs were detected in the soil samples, and their averages in agricultural and urban soils were 192.7 ± 14.2 and 127.3 ± 21.6 particles kg-1, respectively. MP abundance in the soil exhibited variations between different land uses, with agricultural areas showing higher levels compared to urban areas. In agricultural soils, MPs were predominantly blue-colored (44.6 %), in the form of fibers (74.9 %), smaller than 1000 μm (66.1 %), and primarily constituted polyethylene (90.8 %). In urban areas, MPs were also blue-colored (54.7 %), had a fiber shape (64.2 %), smaller than 1000 μm (70.6 %), and mostly belonged to the polyethylene category (78.5 %). A significant difference in MP concentrations was observed between agricultural and urban areas, reflecting the influence of distinct land uses on MP levels. Moreover, Principal Component Analysis (PCA) revealed that soil properties, including pH, electrical conductivity, organic matter, aggregate stability, average weight diameter, sand, clay, and silt, emerged as the primary determinants influencing the abundance and size of MPs within the soil. These findings contribute valuable insights into the origins of soil MPs and the intricate connections between MPs and varying soil characteristics across diverse land use categories.

Microplastic pollution in terrestrial ecosystems: Global implications and sustainable solutions

Microplastic (MPs) pollution has become a global environmental concern with significant impacts on ecosystems and human health. Although MPs have been widely detected in aquatic environments, their presence in terrestrial ecosystems remains largely unexplored. This review examines the multifaceted issues of MPs pollution in terrestrial ecosystem, covering various aspects from additives in plastics to global legislation and sustainable solutions. The study explores the widespread distribution of MPs worldwide and their potential antagonistic interactions with co-occurring contaminants, emphasizing the need for a holistic understanding of their environmental implications. The influence of MPs on soil and plants is discussed, shedding light on the potential consequences for terrestrial ecosystems and agricultural productivity. The aging mechanisms of MPs, including photo and thermal aging, are elucidated, along with the factors influencing their aging process. Furthermore, the review provides an overview of global legislation addressing plastic waste, including bans on specific plastic items and levies on single-use plastics. Sustainable solutions for MPs pollution are proposed, encompassing upstream approaches such as bioplastics, improved waste management practices, and wastewater treatment technologies, as well as downstream methods like physical and biological removal of MPs. The importance of international collaboration, comprehensive legislation, and global agreements is underscored as crucial in tackling this pervasive environmental challenge. This review may serve as a valuable resource for researchers, policymakers, and stakeholders, providing a comprehensive assessment of the environmental impact and potential risks associated with MPs.

Detection and quantification of various microplastics in human endometrium based on laser direct infrared spectroscopy

The pollution of microplastics (MPs) has received widespread attention with the increasing usage of plastics in recent years. MPs could enter the human body and exist in the circulatory system. Endometrium, with rich blood vessels, acts as an essential role in human health and female fertility. However, there is no study reporting the MPs exposure in human endometrium. We collected the endometrium samples to detect the presence of MPs qualitatively and quantitatively via laser direct infrared. We found that there was a total of 13 types of MPs existing in the collected samples, among which 6 special types of MPs were with both high abundance and high detection rate. The abundance of these MPs ranged from 0 to 117 particles/100 mg, with a median abundance of 21 particles/100 mg. Most detected MPs, accounting for 88.35 %, were in small size (20-100 μm). Among small-size MPs, ethylene-acrylic acid copolymer ranked first while polyethylene accounted for the largest proportion among large-size MPs (100-500 μm). Correlation analysis indicated there was no significant relationship between age and MP abundance or BMI and MP abundance. We also designed a questionnaire to investigate lifestyle and daily habits, aiming at revealing the potential relationship between MP exposure and living habits. We discovered that some drinking habits and chewing gum were significantly correlated with a higher level of MP exposure. For the first time, we identified the presence of MPs in human endometrium and clarified the potential connections between MP exposure and lifestyle. Further studies are still necessary to explore more underlying information.

Water retention and hydraulic properties of a natural soil subjected to microplastic contaminations and leachate exposures

The influences of microplastics (MPs) contamination on soils have been extensively studied recently. Most of previous studies focus on saturated hydraulic conductivities and water retention of loose soils under laboratory conditions. The effects of MPs on the hydraulic properties of compacted soils for engineering purposes have not been well understood. This paper presents the laboratory investigation of water retention capacity, saturated (ksat) and unsaturated (kθ) hydraulic conductivities of a compacted natural soil contaminated by MPs and exposed to fresh, medium-aged, and stabilized leachates. The saturated (kg) and unsaturated air conductivities (kgθ) are calculated. The MPs with maximum particle sizes of 500, 150 and 50 μm were added to soils to obtain samples with mass ratios of 0.5, 1.0, 2.0, and 5.0 %, respectively. Under similar ranges of dry densities, permeation of fresh leachates decreases ksat of the compacted soils by 30 % while exposure to stabilized leachates increases ksat by 10 %, due to the viscosities of liquids. The flow channel properties of the compacted soils contaminated with different sizes and concentrations of MPs vary. The most complex flow channel can be found in samples with 5 % 50 μm MPs. The inclusions of MPs decrease residual moisture contents of the compacted soils regardless of MP sizes and percentages. The effects of MPs on air-entry pressures and parameter n depend on the sizes of MPs. The kθ (kgθ) of compacted soils with MPs depend on the combined effects of ksat (kg) and tortuosity parameter (l). Though l ranges from -0.85 to 2.12 with different levels of MP exposures, it does not have a significant influence on the relative hydraulic (kθ/ksat) and air conductivities (kgθ/kg) of the compacted soils. Future studies can focus on the long-term hydraulic properties of soils under MP contamination.

Study of soil microplastic pollution and influencing factors based on environmental fragility theory

Soil microplastics (MPs) pollution is a global concern, but the distribution of MPs and the factors affecting the distribution of MPs in different ecologically fragile karst areas remain poorly understood. Here, we investigated the spatial distribution, characteristics, and composition of MPs in different ecologically fragile karst areas of Guizhou Province and explored the relationship between ecosystem fragility and MPs. Structural equation models combined with robust random forest (RF) models were used to clarify the effects of karst soil properties on MPs and quantify their relative contributions. The abundance of soil MPs in ecologically fragile karst areas was 2949 item kg-1, and the risk of MPs contamination was highest in medium-fragile areas. The robust RF models precisely predicted the abundance of soil MPs in different fragile areas, and the mean root mean square error and R2 were 0.21 and 0.93, respectively. The contribution of karst soil properties to the abundance of MPs was estimated. Some soil chemical properties had a significant effect (p < 0.05) on MPs pollution in ecologically fragile karst areas. The results of our study suggest that the fragile ecological environment may exacerbate MPs pollution. Our study also contributes to establish a scientific theoretical foundation for the utilization of plastics and the prevention and control of microplastics pollution in karst ecosystems.

Global research hotspots and trends on microplastics: a bibliometric analysis

In recent years, microplastics have become an integral part of the terrestrial and aquatic environments, which is one of the major concerns of communities around the world. Therefore, it is necessary to know the current status of studies and feasible potentials in the future. This study, conducted an in-depth bibliometric analysis of publications from 1990 to 2022 to present the influential countries, authors, institutes, papers, and journals on microplastics. Findings reveal that there has been a steady increase in microplastic publications and citations in recent years. And, the number of publications and citations has increased 19 and 35 times since 2015. Besides, we performed a comprehensive keyword analysis to show the significant keywords and clusters in this field. In particular, this study used the TF-IDF method as a text-mining analysis to extract the new keywords used in recent years (i.e., 2020-2022). New keywords can draw the attention of scholars to important issues and provide a basis for future research directions.

Identification of potentially contaminated areas of soil microplastic based on machine learning: A case study in Taihu Lake region, China

Soil microplastic (MP) pollution has recently become increasingly aggravated, with severe consequences being generated. Understanding the spatial distribution characteristics of soil MPs is an important prerequisite for protecting and controlling soil pollution. However, determining the spatial distribution of soil MPs through a large number of soil field sampling and laboratory test analyses is unrealistic. In this study, we compared the accuracy and applicability of different machine learning models for predicting the spatial distribution of soil MPs. The support vector machine regression model with radial basis function (RBF) as kernel function (SVR-RBF) has a high prediction accuracy (R² = 0.8934). Among the six ensemble models, random forest (R² = 0.9007) could better explain the significance of source and sink factors affecting the occurrence of soil MPs. Soil texture, population density, and MPs point of interest (MPs-POI) were the main source-sink factors affecting the occurrence of soil MPs. Furthermore, the accumulation of MPs in soil was significantly affected by human activity. The spatial distribution map of soil MP pollution in the study area was drawn based on the bivariate local Moran's I model of soil MP pollution and the normalized difference vegetation index (NDVI) variation trend. A total of 48.74 km² of soil was in an area of serious MP pollution, mainly concentrated in urban soil. This study provides a hybrid framework that includes spatial distribution prediction of MPs, source-sink analysis, and pollution risk area identification, providing scientific and systematic methods and techniques for pollution management in other soil environments.

Characterization of microplastic, metals associated and ecological risk assessment in the topsoil of shiraz metropolis, south west of Iran

This research studied the occurrence, risk assessment and metals associated with microplastic (MPs) in soil of different land-use types in the south west of Iran. One hundred samples were collected from topsoil and MPs were extracted using the floatation method. In total, 9258 MPs particles with mean of 92.85 ± 119.24 particles kg^-1 were counted. The mean MPs abundance in urban soils was 2.8 and 3.2 times higher than in industrial and agricultural soils, respectively. Fragment (43%) and small MPs (100-250 μm; 41%), were the dominant shape and size, respectively. Four main polymer types including Poly Ethylene (High Density Poly Ethylene and Low Density Poly Ethylene), Nylon (PA), Poly Propylene (PP), and Poly Styrene (PS) were identified. Nylon (29%) and PE (29%) were dominant polymer types. MPs particles in soil contained different levels of metals such as Cd, Cr, Cu, Fe, Hg, Pb, Zn, and Y, except La and Yb. The mean concentrations of metals were higher in MPs than in soil. The indices of MPs-induced risk (H_studyarea=16.8) showed a hazard level (III) in the study area. Pollution load index (PLI_Landusetype) showed hazard level (II) for urban soils and hazard level (I) for industrial and agriculture soils, respectively. Overall, risk index indicated high to extreme danger for MPs pollution in the study area. This is the comprehensive study on the occurrence of soil MPs and associated metals, which provides basic information for a further study concerning ecosystem health in Shiraz.

Effects of land use on the distribution of soil microplastics in the Lihe River watershed, China

Soil contamination by microplastics (MPs) has gained widespread attention, whose fate may be influenced by land use types. The effects of land use types and the intensity of human activities on the distribution and sources of soil MPs at the watershed scale are unclear. In this study, 62 surface soil sites in representing five land use types (urban, tea garden, dryland, paddy field and woodland) and 8 freshwater sediment sites were investigated in the Lihe River watershed. MPs were detected in all samples, and the average abundance of soil and sediments was 401.85 ± 214.02 and 222.13 ± 54.66 items/kg, respectively. The soil MPs abundance followed the sequence: urban > paddy field > dryland > tea garden > woodland. Soil MP distribution and MP communities were significant different (p < 0.05) among land use types. The similarity of MP community highly correlated with geographic distance, and woodlands and freshwater sediments may be a potential fate for MPs in the Lihe River watershed. Soil clay, pH, and bulk density significantly correlated with MP abundance and fragment shape (p < 0.05). The positive correlation between population density, Total- Point of Interest (POI) and MP diversity indicates the importance of intensity of human activities in exacerbating soil MP pollution (p < 0.001). Plastic waste sources accounted for 65.12%, 58.60%, 48.15% and 25.35% of MPs in urban, tea garden, dryland and paddy field soils, respectively. Differences in the intensity of agricultural activities and cropping patterns were associated with different percentages of mulching film sources in the three types of agricultural soils. This study provides new ideas for the quantitative analysis of soil MP sources in different land use types.

A first report on the spatial and temporal variability of microplastics in coastal soils of an urban town in south-western India: Pre- and post-COVID scenario

We present a first study on the temporal changes (2019-2021) in the microplastic abundance in the coastal soils of an urban town in the south-western part of India. All sampling stations exhibited higher abundances of microplastics in soils collected during 2021 (959.7 ± 277.7 particles/kg) compared to those collected in 2019 (515.1 ± 182.7 particles/kg). Morphologically, flakes, fibres, and films are the most abundant types documented in the soil environment. The microplastics of 0.3-5 mm size are relatively more abundant (60.6 %) compared to those of 0.03-0.3 mm size (39.4 %) in 2021. The three main types of polymers (polypropylene and high- and low-density polyethylene) in the soil exhibited an increase in abundance during an interval of 15 months (October 2019 to March 2021). In addition to packaging materials, the enhanced use of surgical masks during the COVID-19 period might have acted as a source of microplastic contamination in the soils.

Occurrence and risks of microplastics in the ecosystems of the Middle East and North Africa (MENA)

The ubiquitous nature of microplastics (MPs) in nature and the risks they pose on the environment and human health have led to an increased research interest in the topic. Despite being an area of high plastic production and consumption, studies on MPs in the Middle East and North Africa (MENA) region have been limited. However, the region witnessed a research surge in 2021 attributed to the COVID-19 pandemic. In this review, a total of 97 studies were analyzed based on their environmental compartments (marine, freshwater, air, and terrestrial) and matrices (sediments, water columns, biota, soil, etc.). Then, the MP concentrations and polymer types were utilized to conduct a risk assessment to provide a critical analysis of the data. The highest MP concentrations recorded in the marine water column and sediments were in the Mediterranean Sea in Tunisia with 400 items/m³ and 7960 items/kg of sediments, respectively. The number of MPs in biota ranged between 0 and 7525 per individual across all the aquatic compartments. For the air compartment, a school classroom had 56,000 items/g of dust in Iran due to the confined space. Very high risks in the sediment samples (Erⁱ > 1500) were recorded in the Caspian Sea and Arab/Persian Gulf due to their closed or semi-closed nature that promotes sedimentation. The risk factors obtained are sensitive to the reference concentration which calls for the development of more reliable risk assessment approaches. Finally, more studies are needed in understudied MENA environmental compartments such as groundwater, deserts, and estuaries.

Microplastic contamination and risk assessment in table salts: Turkey

In this study, the characterization of microplastics of table salts (n = 36) was determined by FT - IR. Then, individuals' exposure to microplastics from table salt consumption was calculated with a deterministic model, and finally, a risk assessment of table salt was performed using the polymer risk index. On average, 44 ± 26, 38 ± 40, 28 ± 9, and 39 ± 30 microplastics/kg were detected in rock salts (n = 16), lake salts (n = 12), sea salts (n = 8), and all salts (n = 36). Microplastics with 10 different polymer types (CPE, VC-ANc, HDPE, PET, Nylon-6, PVAc, EVA, PP, PS, Polyester), 7 different colors (black, red, colorless, blue, green, brown, white, gray), and 3 different shapes (fiber, granulated, film) were found in table salts. The daily, annual and lifetime (70-year) exposures to microplastics from table salt consumption in 15+-year-old individuals (general) were calculated to be 0.41 microplastic particles/day, 150 microplastic particles/year and 10,424 microplastic particles/70-year, respectively. The average microplastic polymer risk index of all table salts was calculated as 182 ± 144 and the risk level is in the medium. In order to minimize microplastic contamination in table salts, protective measures should be taken at the source of the salt, and production processes should be improved.

Microplastics occurrence, detection and removal with emphasis on insect larvae gut microbiota

Microplastics have been identified in all living forms including human beings, the present need is to restrain its spread and devise measures to remediate microplastics from polluted ecosystems. In this regard, the present review emphasizes on the occurrence, sources detection and toxic effects of microplastics in various ecosystems. The removal of microplastics is prevalent by various physico-chemical and biological methods, although the removal efficiency by biological methods is low. It has been noted that the degradation of plastics by insect gut larvae is a well-known aspect, however, the underlying mechanism has not been completely identified. Studies conducted have shown the magnificent contribution of gut microbiota, which have been isolated and exploited for microplastic remediation. This review also focuses on this avenue, as it highlights the contribution of insect gut microbiota in microplastic degradation along with challenges faced and future prospects in this area.

Abundance, spatial distribution, and characteristics of microplastics in agricultural soils and their relationship with contributing factors

Agro-ecosystem contamination with microplastics (MPs) is of great concern. However, limited research has been conducted on the agricultural soil of tropical regions. This paper investigated MPs in the agro-ecosystem of Hainan Island, China, as well as their relationships with plastic mulching, farming practices, and social and environmental factors. The concentration of MPs in the study area ranged from 2800 to 82500 particles/kg with a mean concentration of 15461.52 particles/kg. MPs with sizes between 20 and 200 μm had the highest abundance of 57.57%, fragment (58.16%) was the most predominant shape, while black (77.76%) was the most abundant MP colour. Polyethylene (PE) (71.04%) and polypropylene (PP) (19.83%) were the main types of polymers. The mean abundance of MPs was significantly positively correlated (p < 0.01) with all sizes, temperature, and shapes except fibre, while weakly positively correlated with the population (p = 0.21), GDP (p = 0.33), and annual precipitation (p = 0.66). In conclusion, plastic mulching contributed to significant contamination of soil MPs in the study area, while environmental and social factors promoted soil MPs fragmentation. The current study results indicate serious contamination with MPs, which poses a concern regarding ecological and environmental safety.

The spatial distribution of microplastics in topsoils of an urban environment - Coimbra city case-study

Due to their seemingly ubiquitous nature and links to environmental and human health problems, microplastics are quickly becoming a major concern worldwide. Artificial environments, such as those found in urban environments, represent some of the main sources of microplastic. However, very few studies have focused on the occurrence of microplastics in urban soils. The aim of the current research was to evaluate the microplastic contamination in urban soils from artificial and natural land uses throughout Coimbra city, Portugal. Sixty-seven spaces and ten land use areas were evaluated. The artificial land use areas were dumps, landfills, parking lots, industries and construction areas, and the natural land use areas were forests, urban parks, moors (wetlands), pastures and urban agricultural areas. Microplastic extraction was done by density separation. Quantification and size measurements of microplastics was carried out using a microscope. Polymer types were identified by μ-FTIR for 25% of the samples. The microplastic content ranged from 5 × 10³ to 571 × 10³ particles·kg^-1, with a mean of 106 × 10³ particle·kg^-1. The green park was the land use with the highest concentration of microplastics (158 × 10³ particle·kg^-1) and the forest was the one with the lowest concentration (55 × 10³ particle·kg^-1). The landfill (150 × 10³ particle·kg^-1), industry (127 × 10³ particle·kg^-1) and dump (126 × 10³ particle·kg^-1) were the artificial spaces with the highest levels of microplastics. The main polymers detected were polypropylene and polyethylene, followed by polyvinyl chloride and rubber, and the main sizes measured between 50 and 250 μm. Our results indicate that natural spaces can contain higher amounts of microplastics as compared to artificial spaces in the urban environment. This suggests that microplastics are easily transported through the urban landscape and that urban green spaces can retain microplastics in their soils. Land use planning may present an opportunity to better control the levels of microplastics in urban environments.

Microplastics in the Atmosphere and Water Bodies of Coastal Agglomerations: A Mini-Review

Microplastics are ubiquitously in various environments from the equator to the poles. Coastal agglomerations act as both a source and sink connecting the global microplastic cycles of oceans and continents. While the problem of microplastics is particularly severe and complex in the coastal zones, where both inland and marine pollution are concentrated, the present study aimed to provide hot topics and trends of coastal urban microplastic studies and to review the researches on microplastic pollution in the atmosphere and water bodies in coastal agglomerations in terms of characteristics, behavior, and health threat of microplastics. The results of the bibliometric analysis showed an increase in the annual output of microplastic research. Research hot topics and clusters were analyzed using the VOSviewer. Characteristics of microplastics varied in abundance, size, and polymer type in different environments and countries. Furthermore, coastal cities are taken as a system to sort out the input, output, and internal transmission pathways of microplastics. The health threat of microplastics to urban residents was briefly reviewed and the exposure and health risks of microplastics to infants and young children were of particular concern. Detailed and comprehensive studies on intervention and reduction in the transmission of microplastics between the atmosphere and water bodies, whether microplastics are harmful to infants and young children, and measures to reduce the risk of microplastic exposure are needed.

Microplastics (MPs) distribution in Surface Sediments of the Freidounkenar Paddy Wetland

There is an urgent need to increase knowledge on the distribution of microplastics (MPs) in wetlands because these are sites of special ecological value and the ever-growing use of plastic can threaten such fragile ecosystems. This research assesses, for the first time, the occurrence of MPs in surface sediment of the Freidounkenar International Wetland (Northern Iran), a valuable habitat for migratory birds. A total of 1368 MP/kg were identified in the surface sediments of the wetland. The distribution of MPs in sediments per area was Ezbaran (36.5%), Western Sorkhrood (32.0%), Freidounkenar (20.1%) and Eastern Sorkhrood Ab-bandans (11.4%). The most contaminated sites were located close to agricultural fields, Damgahs (agroecosystems for birds), fishing areas and roads. Fibers and white-transparent and black-grey MPs constituted the dominant MPs in the surface sediment. The most abundant MPs were < 250 μm and these were made of nylon, polypropylene-low density polyethylene copolymer, polystyrene, low density polyethylene and polypropylene. The identification of MPs was carried out visually and supported with Scanning Electron Microscopy (SEM)-Energy Dispersive X-Ray (EDX) and micro-Raman techniques. There were weathering signs in large proportion of the MPs, according to SEM analysis, which evidences their formation from the degradation of other plastics. This is a comprehensive study on MPs in surface sediment of this sensitive internationally recognized ecosystem with high ecological value.

Microplastics Derived from Food Packaging Waste-Their Origin and Health Risks

Plastics are commonly used for packaging in the food industry. The most popular thermoplastic materials that have found such applications are polyethylene (PE), polypropylene (PP), poly(ethylene terephthalate) (PET), and polystyrene (PS). Unfortunately, most plastic packaging is disposable. As a consequence, significant amounts of waste are generated, entering the environment, and undergoing degradation processes. They can occur under the influence of mechanical forces, temperature, light, chemical, and biological factors. These factors can present synergistic or antagonistic effects. As a result of their action, microplastics are formed, which can undergo further fragmentation and decomposition into small-molecule compounds. During the degradation process, various additives used at the plastics' processing stage can also be released. Both microplastics and additives can negatively affect human and animal health. Determination of the negative consequences of microplastics on the environment and health is not possible without knowing the course of degradation processes of packaging waste and their products. In this article, we present the sources of microplastics, the causes and places of their formation, the transport of such particles, the degradation of plastics most often used in the production of packaging for food storage, the factors affecting the said process, and its effects.

Relevance of tyre wear particles to the total content of microplastics transported by runoff in a high-imperviousness and intense vehicle traffic urban area

Microplastics (MPs) are an emerging pollutant and a worldwide issue. A wide variety of MPs and tyre wear particles (TWPs) are entering and spreading in the environment. TWPs can reach waterbodies through runoff, where main contributing particulate matter comes from impervious areas. In this paper, TWPs and other types of MPs that were transported with the runoff of a high populated-impervious urban area were characterised. Briefly, MPs were sampled from sediments in a stormwater detention reservoir (SDR) used for flood control of a catchment area of ∼36 km², of which 73% was impervious. The sampled SDR is located in São Paulo, the most populated city in South America. TWPs were the most common type of MPs in this SDR, accounting for 53% of the total MPs; followed by fragments (30%), fibres (9%), films (4%) and pellets (4%). In particular, MPs in the size range 0.1 mm-0.5 mm were mostly TWPs. Such a profile of MPs in the SDR is unlike what is reported in environmental compartments elsewhere. TWPs were found at levels of 2160 units/(kg sediment·km² of impervious area) and 87.8 units/(kg sediment·km street length); MP and TWP loadings are introduced here for the first time. The annual flux of MPs and TWPs were 7.8 × 10¹¹ and 4.1 × 10¹¹ units/(km²·year), respectively, and TWP emissions varied from 43.3 to 205.5 kg/day. SDRs can be sites to intercept MP pollution in urban areas. This study suggests that future research on MP monitoring in urban areas and design should consider both imperviousness and street length as important factors to normalize TWP contribution to urban pollution.

Microplastics in surface sediments of a highly urbanized wetland

This study investigates the incidence of MPs in surface sediment samples, collected from the Anzali Wetland, Gillan province, North of Iran. This natural habitat receives municipal wastewater effluents and hosts industries and recreational activities that could release plastic to the wetland. There is need for studies to understand MPs pollution in wetlands. A total of 40 superficial sediment samples were taken covering potential pollution hotspots in the wetland. The average level of MPs was 362 ± 327.6 MP/kg: the highest MPs levels were near the outlet of a highly urbanized river (Pirbazar River) (1380 MP/kg), which runs through Rasht city. This was followed by 1255 MP/kg where there was intense fishing, boating and tourism activities in the vicinity of Bandar-e Anzali city. Fibers were the most common type of MPs (80% of the total MPs detected). The MPs polluting the wetland were predominantly white/transparent (42%), and about 40% of them were >1000 μm. Polypropylene (PP) and polyethylene (PE) prevailed in MPs found. MPs were characterized with polarized light microscopy, Raman spectroscopy, Scanning Electron Microscopy coupled with Energy-Dispersive X-ray spectroscopy. Microplastics levels were found to correlate significantly (p > 0.7) with electrical conductivity (EC) and sand-size fraction of the sediments. Coarse-grained sediments presented large capacity to lodge the MPs. This study can be used to establish protection policies in wetlands and newly highlights the opportunity of intercepting MPs in the Anzali Wetland, which are generally >250 μm, before they fragment further.

Soil microplastic characteristics and the effects on soil properties and biota: A systematic review and meta-analysis

The soil environment serves as an assembling area for microplastics, and is an important secondary source of microplastics in other environmental media. Recently, soil microplastics have been extensively studied; however, high variability is observed among the research results owing to different soil properties, and the complexity of soil microplastic composition. The present study amassed the findings of 2886 experimental groups, across 38 studies from 2016 to 2022, and used meta-analysis to quantitatively analyze the differences in the effects of microplastic exposure on soil physicochemical properties and biota. The results showed that among the existing soil microplastic research, agricultural soils maintained a higher environmental exposure distribution than other environments. Microplastic fibers and fragments were the predominant shapes, indicating that the extensive use of agricultural films are the primary influencing factor of soil microplastic pollution at present. The results of the meta-analysis found that microplastic exposure had a significant negative effect on soil bulk density (lnRR = -0.04) and aggregate stability (lnRR = -0.085), indicating that microplastics may damage the integrity of soil structure or damage the soil surface. The significant changes in plant root biomass and soil phosphatase further signified the potential impact of microplastics on soil nutrient and geochemical element cycling. We further constructed species sensitivity distribution curves, revealing that invertebrates had a higher species sensitivity to microplastics, as they can pass through the gut wall of soil nematodes, causing oxidative stress and affecting gene expression. In general, soil is an interconnected complex, and microplastic exposure can directly or indirectly interact with environmental chemical processes in the soil environment, potentially harming the soil ecosystem; however, current research remains insufficient with respect to breadth and depth in terms of the comprehensive "source-sink" mechanism of soil microplastics, the hazard of exposure, and the overall toxic effects.

Microplastics in urban runoff: Global occurrence and fate

Public concerns on microplastic (MP) pollution and its prevalence in urban runoff have grown exponentially. Huge amounts of MPs are transported from urban environments via surface runoff to different environment compartments, including rivers, lakes, reservoirs, estuaries, and oceans. The global concentrations of MPs in urban runoff range from 0 to 8580 particles/L. Understanding the sources, abundance, composition and characteristics of MPs in urban runoff on a global scale is a critical challenge because of the existence of multiple sources and spatiotemporal heterogeneity. Additionally, dynamic processes in the mobilization, aging, fragmentation, transport, and retention of MPs in urban runoff have been largely overlooked. Furthermore, the MP flux through urban runoff into rivers, lakes and even oceans is largely unknown, which is very important for better understanding the fate and transport of MPs in urban environments. Here, we provide a critical review of the global occurrence, transport, retention process, and sinks of MPs in urban runoff. Relevant policies, regulations and measures are put forward. Future global investigations and mitigation efforts will require us to address this issue cautiously, cooperating globally, nationally and regionally, and acting locally.

Impact of simulating real microplastics on toluene removal from contaminated soil using thermally enhanced air injection

This paper investigated the impacts of various real microplastics (MPs), i.e., polyethylene (PE) and polyethylene terephthalate (PET) with different sizes (1000-2000 and 100-200 μm) and different dosages (0.5 and 5% on a dry weight basis), on the toluene removal during the thermally enhanced air injection treatment. First, microscopic tests were carried out to determine the MPs' microstructure and behavior. The PE was mainly a small block, and PET appeared filamentous and sheeted with a larger slenderness ratio. Second, the interactions between MPs and toluene-contaminated soils were revealed by batch adsorption equilibrium experiments and low-field magnetic resonance. The morphological differences and dosage of the MPs impacted soils' total porosity (variation range: 39.2-42.7%) and proportion of the main pores (2-200 μm). Third, the toluene removal during the air injection consisted of compaction, rapid growth, rapid reduction, and tailing stages, and the MPs were regarded as an emerging solid state to affect these removal stages. The final cumulative toluene concentrations of soil-PET mixtures were influenced by total porosity, and those of soil-PE mixtures were controlled by total porosity (influence weight: 0.67) and adsorption capacity (influence weight: 0.33); meanwhile, a self-built comprehensive coefficient of MPs can reflect the relationship between them and cumulative concentrations (correlation coefficient: 0.783).

First evidence of microplastics isolated in European citizens' lower airway

Microplastics (MPs) have been detected in all environmental locations, including the atmosphere. However, few studies have investigated the presence of airborne MPs in the human respiratory system. Our research purpose was to investigate these pollutants in the lower human airways of 44 adult European citizens, using bronchoalveolar lavage fluid (BALF) collection as a minimally invasive method, that enables the detection of these pollutants in living patients. We studied the relationship between the patients' life habits and physiological parameters, based on background information and medical and occupational history, and the concentration of MPs isolated from their respiratory systems. Our results indicate that most MPs were in the form of microfibers (MFs) (97.06%), with an average concentration of 9.18 ± 2.45 items/100 mL BALF, and only 5.88% (0.57 ± 0.27 items/100 mL BALF) were particulate MPs, without a significant relationship with environmental, physiological, or clinical factors. The average size was 1.73 ± 0.15 mm, with the longest dimension (9.96 mm) corresponding to a polyacrylic fiber. Taken together, the results demonstrated the occurrence of MPs in the lower human airway, although more studies are necessary to elucidate the negative effects these pollutants could induce in the human respiratory system and its associated diseases.

Microplastics in urban soils of Nanjing in eastern China: Occurrence, relationships, and sources

Although microplastic (MP) pollution has been defined as a new global challenge by the United Nations Environment Programme, their abundance and composition has only been studied in-depth within farmland soil, while minimal attention has been placed on urban soil contamination. Accordingly, within the current study, MP abundance and composition is investigated within urban soil from green spaces in Nanjing, eastern China. The average MP abundance in soil was 461 ± 222 items/kg and primarily comprised fibers (39.1%) and fragments (37.7%). MPs <1000 μm in size accounted for 83.7% of the total content and white MPs were the most abundant (26.5%). The dominant polymers were polyethylene glycol terephthalate (32.0%) and polypropylene (20.5%). Moreover, relationship network analysis generated three distinct MP modules based on community similarity. Indeed, the degree of similarity increased by ∼26.8% per kilometer. Furthermore, application of a forward selective optimal multiple regression model identified clay, sand, longitude, and points of interest for recycling bins (RecyclePOI) as the primary spatial and soil environmental factors affecting MP abundance and composition. Additionally, five potential sources of MPs were identified based on the MP diversity integrated index fitting results, and point of interest density (MDII-POI) source analysis (R² = 0.21-0.62; P < 0.05). In particular, the point of interest of express delivery points (ExpressPOI) were important sources of plastic emissions as they are widely distributed throughout urban and fringe areas. Collectively, the findings of this study provide novel insights regarding quantitative source appointment and regional ecological control of MPs in urban soil.

Coronas of micro/nano plastics: a key determinant in their risk assessments

As an emerging pollutant in the life cycle of plastic products, micro/nanoplastics (M/NPs) are increasingly being released into the natural environment. Substantial concerns have been raised regarding the environmental and health impacts of M/NPs. Although diverse M/NPs have been detected in natural environment, most of them display two similar features, i.e.,high surface area and strong binding affinity, which enable extensive interactions between M/NPs and surrounding substances. This results in the formation of coronas, including eco-coronas and bio-coronas, on the plastic surface in different media. In real exposure scenarios, corona formation on M/NPs is inevitable and often displays variable and complex structures. The surface coronas have been found to impact the transportation, uptake, distribution, biotransformation and toxicity of particulates. Different from conventional toxins, packages on M/NPs rather than bare particles are more dangerous. We, therefore, recommend seriously consideration of the role of surface coronas in safety assessments. This review summarizes recent progress on the eco-coronas and bio-coronas of M/NPs, and further discusses the analytical methods to interpret corona structures, highlights the impacts of the corona on toxicity and provides future perspectives.