Microplastic contamination of an unconfined groundwater aquifer in Victoria, Australia

Advancing pharmaceutical tablet analysis with laser direct infrared (LDIR) imaging

Laser direct infrared spectroscopy (LDIR) imaging is an emerging vibrational spectroscopic technique that enables rapid surface imaging by using reflectance spectra to capture critical physicochemical properties, such as chemical identity, particle size, shape, and distribution of components, within minutes or even seconds. Despite its advantages, LDIR imaging technology is still in its developmental stages, particularly in understanding method parameters such as the selection of wavenumber for peak and baseline points and the appropriate step size (pixels) for pharmaceutical analysis. In this study, in-house prepared and commercially available tablets were analyzed using LDIR imaging to assess the effects of method development options, particularly the relationship between step size and data acquisition time. Hyperspectral reflectance mode LDIR images were also collected and compared with those obtained from Raman microscopy to validate the accuracy of the LDIR images. The findings emphasize the need for careful wavenumber selection during method development. LDIR images for the evaluated tablets showed good agreement with Raman mapping and hyperspectral mode data sets, although the mean Feret diameter of particles was consistently smaller (14-40 % for active pharmaceutical ingredients (APIs) in the tested tablets) in the LDIR images. Overall, LDIR demonstrates strong potential as a valuable spectroscopic imaging technology for pharmaceutical applications.

A threat beneath the surface: Microplastic contamination in the groundwater of one of Europe's largest wetland complexes

The widespread use of plastic has contributed to a significant accumulation of plastic waste in the environment, much of which is deposited on land. Microplastic (MP) from this waste can infiltrate the soil and reach groundwater, leading to accumulation in subsurface environments. Although MP contamination in soils and groundwater has only recently drawn scientific attention, our study investigates this issue within the Biebrza Valley, one of Europe's largest and most ecologically significant wetland areas. We collected samples from 102 wells distributed across the valley to provide comprehensive coverage and establish baseline MP levels in the groundwater of lowland Europe. MP particles were detected in 101 wells, with concentrations up to 14.1 particles/L and a mean value of 1.3 ± 2.1 particles/L. No significant relationship was found between MP contamination and population density across the valley. Instead, our results suggest a patchy distribution of MP, potentially influenced by the immediate surroundings of each well. Polyurethane and polyamide were the most common polymers identified, suggesting agricultural sources of contamination. Importantly, our study underscores the need for reliable verification techniques, as only 3 % of suspected particles were confirmed as MP through Raman spectroscopy.

Application of high-resolution site characterisation tools and sampling methods for assessing microplastic migration beneath MSW dumpsites

The study addresses a significant environmental issue: the accumulation of microplastics (MPs) in municipal solid waste (MSW) dumpsites and their migration into deeper soil and groundwater (GW). Given the global increase in plastic production and limited waste management, this topic is highly relevant. Furthermore, many studies lack robust methodologies for tracking MP movement through complex soil strata. This study presents an innovative approach, employing advanced site characterisation and sampling techniques, including cone penetration test (CPT), hydraulic profiling tool (HPT), continuous soil sampling, and discrete GW sampling. This integrated method facilitates the identification of high-permeability zones, enabling large-depth sampling while reducing cross-contamination risk. Key findings reveal a substantial MSW layer containing plastics, textiles, and metals in specific zones, while natural soils dominate other areas. Unsaturated zones are mainly sandy, with occasional low-compressibility clay layers. MP concentrations are notably high at the MSW-soil interface 6600-8800 items/kg and decrease significantly with depth to 300-700 items/kg in saturated zones. Smaller MPs (<500 µm), mainly polyethylene, polypropylene, polyamide, and polyester, dominate soil samples. In GW, MP levels range from 26 to 171 items/L, with fibers (<250 µm) comprising about 80 % of MPs, highlighting subsurface soils as partial barriers to MP migration.

Microplastics in groundwater: Environmental fate and possible interactions with coexisting contaminants

Microplastics (MPs) are emerging environmental pollutants which represent a serious threat to ecosystems and human health and have received significant attention from the global community. Currently, a growing number of studies have found the presence of MPs in groundwater. This study exhaustively reviewed varying degrees of recent publications in Web of Science database and investigated the characteristics of MPs (concentration, types, sizes and shapes) in groundwater ecosystems, their migration characteristics, and interactions with co-occurring contaminants. Results suggested that current global research on MPs in groundwater has primarily focused on countries such as India, South Korea, China, Italy and United States. Pollution levels of MPs in groundwater show significant variability, ranging from 0 to 6832 n/L. The predominant plastic polymer types include PP, PE, PS, PA, PET and PVC. The sources of MPs in groundwater are primarily classified as associated with natural processes and anthropogenic activities. The physical, chemical and biological properties can influence the migration of MPs into groundwater. Furthermore, MPs can act as carriers, interacting with co-occurring contaminants, thereby enhancing their migration and toxicity, potentially posing a threat to groundwater ecosystems and human health. Consequently, the major challenges and associated recommendations for forthcoming research on MPs in groundwater are proposed.

Disruption of midgut homeostasis by microplastics in Spodoptera frugiperda: Insights into inflammatory and oxidative mechanisms

Microplastics have evolved as widespread contaminants in terrestrial and aquatic environments, raising significant environmental concerns due to their persistence and bioaccumulation. In this study, we investigated the toxicity of polyethylene microplastics (PE-MPs) on the agricultural insect, Spodoptera frugiperda. Maize leaves containing three sizes (0.5 μm, 5 μm, and 50 μm) of PE-MPs were fed to fall armyworm larvae for 12 days at concentrations of 1.25 g/ L, 5 g/L, and 20 g/L. The results showed that smaller size and higher concentration of microplastics led to increased toxicity. Furthermore, different sizes and maximum concentrations of PE-MPs were selected for subsequent experiments to observe changes in histological and enzymatic biomarkers, midgut microbiome, and metabolic responses. Following PE-MPs exposure, inflammation signs and oxidative stress were detected in the midgut. Significant changes were also observed in midgut microbiota and metabolomes, most related with oxidative stress, inflammatory disorders, and energy metabolism. These results provide evidence of midgut damage and alterations in the microbiota and metabolome of S. frugiperda because of PE-MPs exposure, highlighting the harm that microplastics can inflict on agricultural insects. Additionally, the study lays a theoretical foundation for future research on the transmission of microplastics through the food chain in agricultural ecosystems.

Microplastic pollution of thermal waters in Kütahya, Turkey

Microplastics (MPs) are emerging pollutants in aquatic systems, but their presence in groundwater, particularly thermal waters, is understudied. This study investigates the prevalence and characteristics of MPs in the thermal waters of Kütahya, Turkey, marking the first such exploration in the country and globally in thermal groundwater systems. Twenty-one samples (3 L each) were collected across nine regions and filtered using GF/C filters (0.45-µm pore size). Microscopic examination and μ-Raman spectroscopy revealed an average MP concentration of 0.85 ± 0.71 MPs/L (850 MPs/m3), with the highest at ST-8 (4.88 ± 2.98 MPs/L). Fibers (50%), fragments (39.8%), and films (10.2%) were identified, with polyethylene (22.2%) being the most common polymer type. Variability in MP abundance across stations suggests multiple contamination sources, including agricultural runoff, anthropogenic activities, and material used in water transport infrastructure. The findings indicate low-level MP contamination in thermal groundwater systems, which could influence both ecological health and human activities relying on these waters, such as thermal tourism and greenhouse irrigation. This pioneering study highlights the necessity for integrated waste management policies to mitigate MP pollution and underscores the role of thermal waters in understanding the transport dynamics of MPs in groundwater systems.

Remediation of Micro- and Nanoplastics by Membrane Technologies

Micro- and nanoplastics (NPs) cannot be completely removed from water/wastewater in conventional wastewater treatment plants (WWTPs) and drinking water treatment plants (DWTPs). According to the literature analysis, membrane processes, one of the advanced treatment technologies, are the most effective and promising technologies for the removal of microplastics (MPs) from water and wastewater. In this article, firstly, the properties of MPs commonly found in water and wastewater treatment and their removal efficiencies are briefly reviewed. In addition, research on the use of microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), reverse osmosis (RO), and membrane bioreactors (MBR) for the remediation of MPs and NPs from water/wastewater is reviewed, and the advantages/disadvantages of each removal method are discussed. Membrane filtration is also compared with other methods used to remove MPs. Furthermore, the problem of membrane fouling by MPs during filtration and the potential for MPs to be released from the polymeric membrane structure are discussed. Finally, based on the literature survey, the current status and gaps in research on MPs removal by membrane technologies are identified, and recommendations for further research are made.

The aging and pollution behavior of microplastics in tap water supply system subjected to residual chlorine exposure

This study investigated the aging and pollution behavior of acrylonitrile butadiene styrene (ABS) and polycarbonate (PC) microplastics (MPs) exposed to residual chlorine in tap water distribution systems. The ABS and PC MPs in the aging processes were analyzed using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Results revealed that 0.4 mg/L residual chlorine could induce morphological changes, increase surface oxygen-containing functional groups, and enhance the hydrophilicity of MPs at the CT value of 9216 mg·min/L. Additionally, both ABS and PC MPs released dissolved organic matter (DOM) into water, with higher DOM concentrations observed in the presence of residual chlorine. Besides, this interaction also led to the formation of trichloromethane (TCM). And the TCM production increased with higher MPs concentrations, smaller particle size, and longer chlorine exposure time.

Methodologic insights aimed to set-up an innovative Laser Direct InfraRed (LDIR)-based method for the detection and characterization of microplastics in wastewaters

Wastewater treatment plants (WWTPs) are generally reported to be effective in removing microplastics (MPs). Nevertheless, the lack of standardized methodologies for their counting and characterization hinders direct comparison across literature reports, limiting the establishment of reliable benchmarks. In this perspective, this work aimed to provide methodological insights on a feasible approach for detecting and characterizing MPs in both raw and treated wastewater by exploiting the innovative Laser Direct InfraRed (LDIR) technique. MPs of various polymeric nature, size and shape were specially produced and used to fine-tune and validate a LDIR-based method for both their chemical identification and size/morphology description, while well-established techniques were employed to evaluate the reliability of collected data. The robustness of the tailored protocol was then assessed through a monitoring campaign conducted at a large municipal WWTP in Tuscany (Italy), for which an average MPs removal efficiency of 82 % was estimated. Various polymers were detected in the processed samples, with a high relative content of cellulose-based materials in both influent and effluent (32 % and 54 % of particles, respectively). Most MPs had a characteristic size lower than 100 μm, with particles <30 μm representing about 45 % and 29 % of MPs in the influent and effluent, respectively. MPs were in the form of fibers (25-39 %), fragments (32-43 %) and pellets (29-32 %). The consistency of the obtained results suggested the robustness and reliability of the proposed LDIR-based method, highlighting its potential for more in-depth monitoring of MPs in WWTPs.

Laser Direct Infrared Spectroscopy: A cutting-edge approach to microplastic detection in environmental samples

Microplastic pollution has emerged as a significant global environmental concern, affecting marine, terrestrial, and atmospheric ecosystems. As microplastic contamination continues to intensify, the need for precise, efficient, and scalable detection method is growing. This review highlights recent advancements in microplastic detection technologies, with a particular focus on Laser Direct Infrared (LDIR) spectroscopy. Utilizing a Quantum Cascade Laser (QCL), LDIR offers rapid, sensitive, and automated detection capabilities. It significantly reduces analysis time compared to conventional techniques such as Fourier Transform Infrared (FTIR) and Raman spectroscopic techniques, making it ideal for large-scale environmental monitoring. Its ability to identify particles as small as 10 μm, combined with enhanced wavelength accuracy, positions LDIR as a promising tool for microplastic analysis across various environmental matrices. Despite some limitations, such as a narrower spectral range, LDIR's superior speed and precision make it a critical advancement for understanding and addressing the global microplastic crisis.

Airborne microplastic contamination and health risks in Greater Cairo, Egypt

Air pollution by microplastics (MPs) is an increasingly concerning environmental issue, but the presence of MPs in the atmosphere and its potential health risks has not been studied in Greater Cairo. The sites were therefore selected during the winter season from the north to the south of the Cairo metropolitan area, representing urban and residential/industrial areas in terms of population, traffic, and industrial pressure. This was achieved through a combination of quantitative MP detection, mathematical modeling, and a risk assessment approach based on total suspended particulate matter (TSP) at these sites. The TSP concentration was investigated in the air and associated MP particles. The highest MP values were found at the study sites with higher population and more traffic than at lower locations. The spatial distribution of site concentrations was from high to low. Helwan site (87 particles/m3) had the most MP, followed by Dokki (69 particles/m3) and Nasr City (60 particles/m3), and El-Nozha had the least MP during the investigation (30 particles/m3). The morphology, composition, and size of these MPs in the samples were determined by scanning electron microscopy (SEM) and gas chromatography-mass spectrometry (GC-MS). Various MP forms have been identified in these sites, including fibers, fragments, films, and pellets, with fragments being the most common. Three different MP polymers (PE, PP, and PS) were identified. The potential health risks posed by airborne MPs cannot be ignored when exposed to outdoor airborne substances at maximum annual levels. This study confirms the widespread existence of the inhaled MP in the air and provides a solid basis for future studies aimed at understanding real-world conditions of inhalation exposure to MP.

Spatiotemporal distribution and ecological hazards of microplastic pollution in soil water resources around a wastewater treatment plant and municipal solid waste site

Research into the relative contributions of microplastic (MP) sources to aquatic and terrestrial environments is essential for understanding their fate and transport which is a prerequisite for designing effective pollution management strategies. This study explores the spatial distribution, seasonal variations, and ecological hazards of MPs in surface water, groundwater, soil, sediment, and leachate matrices adjacent to municipal solid waste (MSW) and sewage treatment plant (STP) sites in Northern India. Elevated MP concentrations were observed in leachate (283.22 ± 15.78 particles/L; pre-monsoon), whereas groundwater exhibited significantly reduced levels (10.75 ± 2.04 particles/L; pre-monsoon), indicating the attenuation efficiency and filtration potential of the subsurface zone. Seasonal variations revealed a dilution effect from monsoonal runoff, reducing MP concentrations. The identified MP shapes were predominantly fibers, followed by fragments, with transparent particles being the most common. The size distribution was dominated by smaller MPs (<0.3 mm), which exhibited a positive correlation with overall MP concentrations. The polymer types of MPs identified in the samples categorise the polymer hazard index (PHI) as a hazard level V (>1000) in all the samples indicating a high chemical risk in both the seasons. Similarly, the principal component analysis (PCA) revealed MP hotspots, particularly in soils near the MSW site, with concentrations reaching 53,580 ± 720 particles/kg emphasizing the vulnerability of terrestrial systems. This research highlights the importance of implementing effective waste management practices and provides valuable insights into the fate and transport of MPs by presenting strong evidence of MP movement from typical MSW/STP sites into adjacent land and water resources.

Exploring the ecotoxicological impacts of microplastics on freshwater fish: A critical review

Microplastics (MPs) have become ubiquitous in the environment, prompting significant concern among ecotoxicologists due to their potential toxic effects. These particles originate from various sources, including the fragmentation of larger plastic debris (secondary microplastics) and consumer products such as liquid soaps, exfoliants, and cleaning agents. The widespread use of plastics, coupled with inadequate waste management, poses a growing threat to ecosystem health worldwide. MPs are plastic particles composed of high-molecular-weight polymers that exhibit biochemical stability. Plastics break down into MPs and even smaller nanoplastics through various degradation mechanisms, such as exposure to UV radiation from sunlight and other environmental factors. Due to their resemblance to certain types of zooplankton and food particles, MPs are often ingested by fish, entering their digestive systems. Once inside, they do not remain solely in the gut; rather, they infiltrate the fish's circulatory and lymphatic systems, eventually distributing throughout various tissues and organs. Microplastics have been found in fish gills, muscles, liver, heart, swim bladders, ovaries, spinal cords, and even brains. The presence of MPs in these organs has been linked to significant adverse effects, including reproductive, neurological, hormonal, and immune system disruptions. This toxicity extends beyond fish, as bioaccumulation and biomagnification of MPs affect other organisms as well, marking MPs as a major anthropogenic stressor that impacts ecosystems at multiple levels. Research indicates that nearly all aquatic environments globally are at risk of MP contamination. Laboratory and field studies highlight fish as particularly susceptible to MP ingestion, though freshwater species have been less extensively studied than marine counterparts. After exposure, fish may suffer various health issues, either directly from MPs or from their interaction with other contaminants. The broader environmental implications of these laboratory findings and the specific role of MPs in increasing fish exposure to harmful chemicals remain topics of ongoing debate. This review aims to contribute to ecotoxicological insights on fish contamination by MPs and outline areas for future investigation.

Global distribution, drivers, and potential hazards of microplastics in groundwater: A review

Since microplastics (MPs) were first detected in groundwater, an increasing number of studies have focused on groundwater pollution by MPs. However, knowledge of the global properties of groundwater MPs: distribution, concentration, composition, and morphology remains limited, while potential factors regulating their transport and distribution in groundwater, especially the hydrogeological background and climate warming conditions, have been omitted from most analyses. Furthermore, previous field investigations did not assess the risks posed by groundwater MPs to the environment and to human health, a necessary preliminary to remediation. In this work, to promote future MP pollution studies and remediation policies, we assimilated and synthesized the current knowledge on this topic. We reviewed current data on global groundwater pollution by MPs, analyzed the driving factors of their transport and distribution, and summarized the ecological and health hazards posed by MPs, before discussing current knowledge limits and suggesting perspectives for future work.

Microplastic migration from landfill-mined soil through earth filling operations and ecological risk assessment: a case study in New Delhi, India

Microplastics (MPs), plastic pieces smaller than 5 mm, are emerging as a critical ecological threat, potentially disrupting ecosystems and complicating waste management practices. Landfill-Mined Soil-Like Material (LMSLM), a byproduct of landfill reclamation, is gaining global traction for rehabilitating degraded land and repurposing it for geotechnical applications. While studies have examined contaminants like heavy metals and salts, MPs contamination has been largely overlooked, raising environmental concerns. The widespread use of LMSLM in earth-filling increases the risk of MP pollution. Additionally, significant gaps remain in understanding how MPs are distributed across different size fractions during sieving, which is critical for developing effective remediation strategies and informing future policies. This study aims to fill the existing knowledge gap by investigating the presence of microplastics in LMSLM collected from three aged waste dumpsites in New Delhi, India, and evaluating the ecological risks associated with its reuse. The results revealed the presence of MPs in all LMSLM samples with concentrations ranging from 25950 to 41110 items/kg. Fibers and fragments were the dominant shapes, with 60 % of particles measuring less than 425 µm. The color characteristics revealed the dominance of white, transparent, and black color. Polyethylene and polypropylene were the most common polymers, with smaller amounts of polyamide, polyethylene terephthalate, and polyester. SEM-EDX analysis revealed weathering effects and the presence of heavy metals, including Lead (Pb), Cadmium (Cd), and Arsenic (As), adsorbed on the MP surface. Ecological risk assessment using the Polymer Hazard Index and Pollution Load Index identified hazard levels of V and II, respectively, while the Potential Ecological Risk Index indicated a medium risk. Furthermore, the dimensional analysis demonstrates that MP width, particularly in fiber-shaped MPs, plays a crucial role in determining retention and migration during sieving, while MPs with uniform shapes, like spheres and fragments, exhibit limited movement. These findings underscore the need for protective measures when using LMSLM in geotechnical applications to prevent MP migration and contamination of surrounding environments. The study highlights the importance of further research on MP contamination in reclaimed landfill materials and its implications for sustainable land use and waste management.

Microplastics in ecosystems: Critical review of occurrence, distribution, toxicity, fate, transport, and advances in experimental and computational studies in surface and subsurface water

Microplastics (MPs), particles under 5 mm, pervade water, soil, sediment, and air due to increased plastic production and improper disposal, posing global environmental and health risks. Examining their distribution, quantities, fate, and transport is crucial for effective management. Several studies have explored MPs' sources, distribution, transport, and biological impacts, primarily focusing on the marine environment. However, there is a need for a comprehensive review of all environmental systems together for enhanced pollution control. This review critically examines the occurrence, distribution, fate, and transport of MPs in the following environments: freshwater, marine, and terrestrial ecosystems. The concentration of MPs is highly variable in the environment, ranging from negligible to significant amounts (0.003-519.223 items/liter in water and 0-18,000 items/kg dry weight sediment, respectively). Predominantly, these MPs manifest as fibers and fragments, with primary polymer types including polypropylene, polystyrene, polyethylene, and polyethylene terephthalate. A complex interplay of natural and anthropogenic actions, including wastewater treatment plant discharges, precipitation, stormwater runoff, inadequate plastic waste management, and biosolid applications, influences MPs' presence and distribution. Our critical synthesis of existing literature underscores the significance of factors such as wind, water flow rates, settling velocities, wave characteristics, plastic morphology, density, and size in determining MPs' transport dynamics in surface and subsurface waters. Furthermore, this review identifies research gaps, both in experimental and simulation, and outlines pivotal avenues for future exploration in the realm of MPs.

Limits, challenges, and opportunities of sampling groundwater wells with plastic casings for microplastic investigations

Investigating microplastics (MPs) in groundwater suffers from problems already faced by surface water research, such as the absence of common protocols for sampling and analysis. While the use of plastic instruments during the collection, processing, and analysis of water samples is usually avoided in order to minimize unintentional contamination, groundwater research encompassing MPs faces unique challenges. Groundwater sampling typically relies on pre-existing monitoring wells (MWs) and water wells (WWs) that are often constructed with polyvinyl chloride (PVC) casings or pipes due to their favorable price-performance ratio. Despite the convenience, however, the suitability of PVC casings for MP research is questionable. Unfortunately, the specifics of these wells are often not detailed in published studies. Current literature does not indicate significant pollution risks from PVC casings, suggesting these wells might still be viable for MP studies. Our preliminary analysis of the existing literature indicates that if PVC exceeds 6 % of the total MP concentration, it is likely that casings and pipes made of PVC are a source of pollution. Above this threshold, additional investigations in MWs and WWs with PVC casings and pipes are suggested.

A review of the influence mechanisms of climate-induced events on groundwater microplastic contamination: A focus on aquifer vulnerabilities and mitigation strategies

Climate change and plastic pollution are two main issues that our world is currently facing, and they are mainly linked through various processes, mechanisms, and chemical blueprint. Emerging issues related to microplastic (MP) contamination in freshwater are expanding and diverse research is being carried out globally. Factors causing climate change are increasing the frequency of extreme weather phenomena such as floods, drought, sea level rise, and heat waves, which can directly or indirectly influence the plastic/MP contamination in various ecosystems including groundwater environments. Here, we review the impacts of extreme weather events on MP contamination in freshwater with a specific focus on groundwater environments. This narrative review shows that flooding can have the most adverse effect on the MP pollution in groundwater environments through recharge events. Drought can also have major effects on MP pollution. Karst, alluvial, and coastal aquifers exhibit the highest levels of MP contamination among various aquifer types. Climate change's impact on different types of aquifers can vary depending on hydrogeological conditions and other factors in the groundwater environment. Prevention and comprehensive solutions are crucial for addressing MPs in the environment, with downstream measures being supplementary to upstream ones.

Fate and transport of fragmented and spherical microplastics in saturated gravel and quartz sand

Microplastics in urban runoff undergo rapid fragmentation and accumulate in the soil, potentially endangering shallow groundwater. To improve the understanding of microplastic transport in groundwater, column experiments were performed to compare the transport behavior of fragmented microplastics (FMPs ∼1-µm diameter) and spherical microplastics (SMPs ∼1-, 10-, and 20-µm diameter) in natural gravel (medium and fine) and quartz sand (coarse and medium). Polystyrene microspheres were physically abraded with glass beads to mimic the rapid fragmentation process. The experiments were conducted at a constant flow rate of 1.50 m day-1 by injecting two pore volumes of SMPs and FMPs. Key findings indicate that SMPs showed higher breakthrough, compared to FMPs in natural gravel, possibly due to size exclusion of the larger SMPs. Interestingly, FMPs exhibited higher breakthrough in quartz sand, likely due to tumbling and their tendency to align with flow paths, while both sizes (larger and smaller relative to FMPs) of SMPs exhibited higher removal in quartz sand. Therefore, an effect due to shape and size was observed.

Unveiling the ecotoxicological impact of microplastics on organisms - the persistent organic pollutant (POP): A comprehensive review

Microplastics have been ubiquitous in our environment for decades, and numerous studies have revealed their extensive dispersion, reaching far beyond the surface of the land, soil, aquatic ecosystems. They have infiltrated the food-chain, the food web, even the air we breathe, as well as the water we drink. Microplastics have been detected in the food we consume, acting as vectors for hazardous chemicals that adhere to their hydrophobic surfaces. This can result in the transfer of these chemicals to the aquatic life, posing a threat to their well-being. The release of microplastics into different environmental settings can give rise to various eco-toxicological implications. The substantial body of literature has led scientists to the consensus that microplastic pollution is a global problem with the potential to impact virtually any type of ecosystem. This paper aims to discuss crucial information regarding the occurrence, accumulation, and ecological effects of microplastics on organisms. It also highlights the new and emerging disease named "Plasticosis" that is directly linked to microplastics and its toxicological effects like permanent scarring and long-term inflammation in the digestive system of the seabirds. By comprehending the behaviour of these microplastic pollutants in diverse habitats and evaluating their ecological consequences, it becomes possible to facilitate a better understanding of this toxicological issue.

Vertical transfer of microplastics in nearshore water by cultured filter-feeding oysters

Microplastics (MPs) are widely distributed in the sea, but the vertical transfer of MPs by marine organisms in coastal area is still poorly understood. In this study, we used laser direct infrared (LDIR) spectroscopy to determine the number and characteristics of MPs deposited by cultured oyster Crassostrea gigas and further compared the differences between MPs of natural deposit and biodeposit in field environments. The amounts of MPs found in the biodeposit of cultured oysters were 3.54 times greater than that in the natural deposition. The polymer types of biodeposit MPs also differed from those of natural deposition. It was estimated that a single oyster can deposit 15.88 MPs per day, which is a figure much higher than the initial results, and hotspots of MPs deposition may be formed within the oyster aquaculture area. We used generalized linear mixed model (GLMM) to further infer the sources of MPs in sediments and found that distance to shore, cultured zone and urban center were important predictors of MPs abundance in sediments of aquaculture area. The above results suggest that cultured bivalves have an important capacity for MPs biodeposition and will further change the vertical distribution pattern of MPs in coastal environments.

Research advances on microplastics contamination in terrestrial geoenvironment: A review

The contamination of microplastics in terrestrial geoenvironment (CMTG) is widespread and severe and has, received considerable attention. However, studies on CMTG are in their initial stages. The literature on CMTG published in the past decade was analyzed through bibliometric analysis, such as the annual publications, countries with the highest contributions, prolific authors, and author keywords. The sources, compositions, migrations and environmental impacts of CMTG are summarized, and possible future directions are proposed. This study analyzed the annual publications, countries with the highest contributions, prolific authors, and author keywords related to microplastics. The results demonstrated that 15,306 articles were published between 2014 and 2023. China is the leading country in terms of the total number of publications. The main sources of CMTG include landfills, agricultural non-point sources, sewage treatment systems and transportation systems. The composition of the CMTG exhibits significantly temporal and spatial variability from different sources. The migration paths of the CMTG were within the soil, groundwater seepage and wind transportation of suspended particles. Microplastics increase soil cohesion, decrease porosity, reduce pore scale, decrease air circulation, and increase water retention capacity, and the exudation of highly water-soluble additives in microplastics can cause secondary contamination of geological entities. Microplastics have an adverse effect on plant growth, animal digestion, microbial activity, energy and lipid metabolism, oxidative stress, and respiratory diseases in humans. It is recommended to develop more efficient and convenient quantitative testing methods for microplastics, formulate globally harmonized testing and evaluation standards, include microplastic testing in testing programs for contaminated soils, and develop efficient methods for the remediation of microplastic contaminated geological bodies.

Impact of Type and Shape of Microplastics on the Transport in Column Experiments

The pervasive nature of plastic and the longevity of plastics leaves a legacy of microplastics (MPs) that contaminate our environment, including drinking water sources. Although MPs have been documented in every environmental setting, a paucity of research has focused on the transport and fate of MPs in groundwater. Previous field and laboratory studies have shown that MPs can migrate through aquifer material and are influenced by environmental factors. This study used controlled column experiments to investigate the influence of polymer type (polyamide, polyethylene, polypropylene, and polyester) and particle shape (fragment, fiber, and sphere) on MP retardation and retention. The results showed that all individual MP types investigated were retarded compared to the NaCl tracer, with a retardation factor ranging from 1.53 to 1.75. While hypothesized that presence of multiple types and shapes could change mobility, the results indicate that this hypothesis is not correct for the conditions tested. This study provides new insights into MP transport in groundwater systems based on the characteristics of MP particles. In addition, this study demonstrates the need for further research on types of MPs and under more conditions, especially in the presence of a mixture of types and shapes of MPs to gauge what is occurring in natural systems where many MPs are present together.

Microplastics in multi-environmental compartments: Research advances, media, and global management scenarios

During the past decades, microplastics (MPs) have become an emerging concern due to their persistence and potential environmental threat. MP pollution has become so drastic that it has been found in the human food chain, breast milk, polar regions, and even the Himalayan basin, lake, etc. Inflammation, pulmonary hypertension, vascular occlusions, increased coagulability and blood cell cytotoxicity, disruption of immune function, neurotoxicity, and neurodegenerative diseases can all be brought on by severe microplastic exposure. Although many MPs studies have been performed on single environmental compartments, MPs in multi-environmental compartments have yet to be explored fully. This review aims to summarize the muti-environmental media, detection tools, and global management scenarios of MPs. The study revealed that MPs could significantly alter C flow through the soil-plant system, the structure and metabolic status of the microbial community, soil pH value, biomass of plant shoots and roots, chlorophyll, leaf C and N contents, and root N contents. This review reveals that MPs may negatively affect many C-dependent soil functions. Different methods have been developed to detect the MPs from these various environmental sources, including microscopic observation, density separation, Raman, and FT-IR analysis. Several articles have focused on MPs in individual environmental sources with a developed evaluation technique. This review revealed the extensive impacts of MPs on soil-plant systems, microbial communities, and soil functions, especially on water, suggesting possible disturbances to vital ecological processes. Furthermore, the broad range of detection methods explored emphasizes the significance of reliable analytical techniques in precisely evaluating levels of MP contamination in various environmental media. This paper critically discusses MPs' sources, occurrences, and global management scenarios in all possible environmental media and ecological health impacts. Future research opportunities and required sustainable strategies have also been suggested from Bangladesh and international perspectives based on challenges faced due to MP's pollution.

Microplastics in urban water systems, Tehran Metropolitan, Iran

Urban water systems are potential sources of secondary microplastics (MPs) as well as a distributor of MPs in the environment. In the present study, the presence of MPs in the urban water systems of the Tehran Metropolitan (Capital of Iran) was investigated. In addition, the probable relationship of MPs with different land uses (i.e., residential-commercial, forest, military, and highway) was assessed. The results showed that all parts of Tehran's urban water system in the study area were contaminated with MPs (107.1 ± 39, 37.8 ± 10.5, 48.3 ± 3.1, 46.9 ± 5.6, 59.4 ± 26.5, 1.7, 2.0 ± 0.6, 7.9 ± 1, 1.8 ± 0.2 particles/liter at the residential, integrated, military, forest, highway runoffs, drinking water, groundwater, seasonal river, and the effluent of the wastewater treatment plants; respectively). However, significant differences were found between different land uses. As expected, the residential runoff had the highest rate of MPs pollution, with 107.1 ± 39 particles/liter. According to the obtained results and our estimation, more than five million MPs/day can enter into the water bodies and soil of the study area through the wastewater treatment plants. While there are significant differences in MPs in the different land uses, our findings suggest that residential areas and highways need further attention in controlling the spread of MPs in urban areas.

Groundwater systems under siege: The silent invasion of microplastics and cock-tails worldwide

Microplastics (MPs) contamination is one of the significant escalating environmental concerns worldwide, and this stems from the increasing production and unlawful disposal of plastic materials. Regretfully, the synthesis of plastic materials is expected to triple in the upcoming years. Nevertheless, MPs pollution in marine, aquatic, and terrestrial settings has received much attention, unlike in groundwater systems. This study exhaustively reviewed varying degrees of recent publications in various search engines and provided a detailed state of current knowledge and research progress vis-à-vis MPs and cock-tail pollution in groundwater systems. Evidently, groundwater sources are severely contaminated as a result of growing anthropogenic activities and vertical movement of MPs and cock-tails from the atmospheric, terrestrial, and aquatic environments, however, fewer researchers have fixated their attention on estimating the occurrence of MPs in groundwater resources, while sufficient information regarding their sources, sampling methods, abundance, transport pathways, fate, modeling techniques, appropriate and adequate data, sorption properties, separation from other environmental media, toxicity, and remedial measures are extensively lacking. In addition, MPs may combine with other toxic emerging contaminants to improve migration and toxicity; however, no research has been conducted to fully understand cock-tail migration mechanisms and impacts in groundwater systems. Over time, groundwater may be regarded as the primary sink for MPs, if effective actions are neglected. Overall, this study detected a lack of concern and innumerable voids in this field; hence, vital and nascent research gaps were identified for immediate, advanced, and interdisciplinary research investigations.

Microplastics in different municipal solid waste treatment and disposal systems: Do they pose environmental risks?

Microplastic (MP) pollution is a significant worldwide environmental and health challenge. Municipal solid waste (MSW) can be an important source of MPs in the environment if treated and disposed of inappropriately, causing potential ecological risks. MSW treatment and disposal methods have been gradually shifting from landfilling/dumping to more sustainable approaches, such as incineration or composting. However, previous studies on MP characteristics in different MSW treatment and disposal systems have mainly focused either on landfills/dumpsites or composts. The lack of knowledge of multiple MSW treatment and disposal systems makes it difficult to ensure effective MP pollution control during MSW treatment and disposal. Therefore, this study systematically summarizes the occurrence of MPs in different MSW treatment and disposal systems (landfill/dumpsite, compost, and incineration) on the Eurasian scale, and discusses the factors that influence MPs in individual MSW treatment and disposal systems. In addition, the paper assesses the occurrence of MPs in the surrounding environment of MSW treatment and disposal systems and their ecological risks using the species sensitivity distribution approach. The study also highlights recommendations for future research, to more comprehensively describe the occurrence and fate of MPs during MSW treatment and disposal processes, and to develop appropriate pollution control measures to minimize MP pollution.

Detection and characterisation of microplastics in tap water from Gauteng, South Africa

This study reports the presence, concentration, and characteristics of microplastics (MPs) in tap water in three suburbs in Gauteng Province in South Africa. Physical characterisation was conducted using stereomicroscopy and scanning electron microscopy following staining of MPs with the Rose Bengal dye. The concentrations of MPs in all samples ranged from 4.7 to 31 particles/L, with a mean of 14 ± 5.6 particles/L. Small-sized (<1 mm) and fibrous-shaped MPs were most abundant in all samples. Fibers accounted for 83.1% of MPs in samples from all the three areas, followed by fragments (12.4%), pellets/beads (3.1%), and films (1.5%), with a minor variation in the distribution of shapes and sizes in samples from each area. Raman microspectroscopy was used for chemical analysis, and five polymers were identified, namely: high-density polyethylene, polyurethane, polyethylene terephthalate, poly(hexamethylene terephtalamide), and poly(acrylamide-co-acrylic acid). C.I Pigment Red 1, C.I. Solvent Yellow 4, Potassium indigotetrasulphonate, and C.I Pigment Black 7 were the colourants detected. These colourants are carcinogenic and mutagenic and are potentially toxic to humans. The prevalence of MPs in tap water implies their inadequate removal during water treatment. For instance, the presence of poly(AM-co-AA) suggests that drinking water treatment plants may be a potential source of MPs in tap water. Other polymers, e.g., high-density polyethylene may be released from pipes during the transportation of drinking water. The estimated daily consumption of MPs from tap water was 1.2, 0.71, and 0.50 particles/kg.day for children, men, and women, respectively. The findings of this study provide evidence of the presence of MPs in drinking water in South Africa, thus giving some insights into the performance of treatment plants in removing these contaminants and a benchmark for the formulation of standard limits for the amount of MPs in drinking water.

Analysing micro- and nanoplastics with cutting-edge infrared spectroscopy techniques: a critical review

The escalating prominence of micro- and nanoplastics (MNPs) as emerging anthropogenic pollutants has sparked widespread scientific and public interest. These minuscule particles pervade the global environment, permeating drinking water and food sources, prompting concerns regarding their environmental impacts and potential risks to human health. In recent years, the field of MNP research has witnessed the development and application of cutting-edge infrared (IR) spectroscopic instruments. This review focuses on the recent application of advanced IR spectroscopic techniques and relevant instrumentation to analyse MNPs. A comprehensive literature search was conducted, encompassing articles published within the past three years. The findings revealed that Fourier transform infrared (FTIR) spectroscopy stands as the most used technique, with focal plane array FTIR (FPA-FTIR) representing the cutting edge in FTIR spectroscopy. The second most popular technique is quantum cascade laser infrared (QCL-IR) spectroscopy, which has facilitated rapid analysis of plastic particles. Following closely is optical photothermal infrared (O-PTIR) spectroscopy, which can furnish submicron spatial resolution. Subsequently, there is atomic force microscopy-based infrared (AFM-IR) spectroscopy, which has made it feasible to analyse MNPs at the nanoscale level. The most advanced IR instruments identified in articles covered in this review were compared. Comparison metrics encompass substrates/filters, data quality, spatial resolution, data acquisition speed, data processing and cost. The limitations of these IR instruments were identified, and recommendations to address these limitations were proposed. The findings of this review offer valuable guidance to MNP researchers in selecting suitable instrumentation for their research experiments, thereby facilitating advancements in research aimed at enhancing our understanding of the environmental and human health risks associated with MNPs.

Experimental and simulated microplastics transport in saturated natural sediments: Impact of grain size and particle size

Microplastics (MPs) present in terrestrial environments show potential leaching risk to deeper soil layers and aquifer systems, which threaten soil health and drinking water supply. However, little is known about the environmental fate of MPs in natural sediments. To examine the MPs transport mechanisms in natural sediments, column experiments were conducted using different natural sediments and MPs (10-150 µm) with conservative tracer. Particle breakthrough curves (BTCs) and retention profiles (RPs) were numerically interpreted in HYDRUS-1D using three different models to identify the most plausible deposition mechanism of MPs. Results show that the retention efficiency for a given particle size increased with decreasing grain size, and RPs exacerbated their hyper-exponential shape in finer sediments. Furthermore, the amounts of MPs present in the effluent increased to over 85 % as MPs size decreased to 10-20 µm in both gravel and coarse sand columns, while all larger MPs (125-150 µm) were retained in the coarse sand column. The modeling results suggested that the blocking mechanism becomes more important with increasing particle sizes. In particular, the attachment-detachment without blocking was the most suited parameterization to interpret the movement of small MPs, while a depth-dependent blocking approach was necessary to adequately describe the fate of larger particles.

Presence of microplastics in the groundwater of volcanic islands, El Hierro and La Palma (Canary Islands)

The increasing amount of plastic litter worldwide is a serious problem for the environment and its biodiversity, ecosystems, animal and human welfare and the economy. The degradation of these plastics leads to microplastics (MPs), which have been reported for the first time in groundwater in the Canary archipelago. This research investigates the presence of MPs at nine different points on La Palma and El Hierro, where samples were collected in galleries, wells and springs during the month of December 2022. Six different polymers were found with Fourier transform infrared spectroscopy (FTIR) - polypropylene (PP), polyethylene (PE), cellulose (CEL), polyethylene terephthalate (PET), polystyrene (PS) and polymethyl methacrylate (PMMA). The particle concentrations found ranged from 1 to 23 n/L, with a maximum particle size of 1900 μm, the smallest being 35 μm. PP and PE were the most common polymers found in the analysis, associated with the use of packaging, disposable products, textiles and water pipes, related to poorly maintained sewerage networks where leaks occur, allowing these MPs to escape into the environment and end up in groundwater. The detection of microplastic pollution in groundwater emphasises environmental hazards, including biodiversity disruption and water source contamination. Additionally, it presents potential risks to human health by transferring contaminants into the food chain and through respiratory exposure.

Microplastic pollution calls for urgent investigations in stygobiont habitats: A case study from Classical karst

Microplastic pollution in karst systems is still poorly studied, despite the presence of protected species and habitats, and important water reserves. Vulnerable key species hosted in these habitats could consume or assimilate microplastics, which can irreversibly damage management efforts, and thus ecosystems functionality. This can be particularly true for subterranean water habitats where microplastic pollution effects on wildlife management programs are not considered. The aim of this study is to provide a case study from the Classical Karst Region, which hosts peculiar habitats and key species protected at European level, such as the olm Proteus anguinus. As this area has been deeply exploited and modified over time, and is adjacent to highways, roads and railways, which could contribute to pollution within the karst system, threatening the ecosystems, it provides a perfect model system. In this study we collected and investigated water and sediment samples from aquatic environments of surface and subterranean habitats hosting several subterranean environment-adapted organisms. Examined particles were counted and characterized by size, color and shape via visual identification under a microscope, with and without UV light. Furthermore, spectroscopic analyses were carried out in order to identify microplastics typology. Microplastics were found in all examined habitats. In water, microplastics concentration ranged from 37 to 86 items/L, in sediments from 776 to 2064 items/kg. Fibre-shape was the main present, followed by fragments and beads, suggesting multiple sources of pollution, especially textile products. Most of the particles were fluorescent under UV light and were mainly transparent, while not-fluorescent ones were especially black, blue or brown. Samples contained especially polyesters and copolymers. These results highlight intense MP pollution in karst areas, with significant impacts on water quality, and potential effects on subterranean environment-dwelling species. We stress the importance of monitoring pollution in these critical environments for biodiversity and habitat conservation: monitoring in karst areas must become a priority for habitat and species protection, and water resources management, improving analyses on a larger number of aquatic surface and subterranean habitats.

Evidence of internalized microplastics in mussel tissues detected by volumetric Raman imaging

Microplastics are a global ecological concern due to their potential risk to wildlife and human health. Animals ingest microplastics, which can enter the trophic chain and ultimately impact human well-being. The ingestion of microplastics can cause physical and chemical damage to the animals' digestive systems, affecting their health. To estimate the risk to ecosystems and human health, it is crucial to understand the accumulation and localization of ingested microplastics within the cells and tissues of living organisms. However, analyzing this issue is challenging due to the risk of sample contamination, given the ubiquity of microplastics. Here, an analytical approach is employed to confirm the internalization of microplastics in cryogenic cross-sections of mussel tissue. Using 3D Raman confocal microscopy in combination with chemometrics, microplastics measuring 1 μm in size were detected. The results were further validated using optical and fluorescence microscopy. The findings revealed evidence of microplastics being internalized in the digestive epithelial tissues of exposed mussels (Mytilus galloprovincialis), specifically within the digestive cells forming digestive alveoli. This study highlights the need to investigate the internalization of microplastics in organisms like mussels, as it helps us understand the potential risks they pose to aquatic biota and ultimately to human health. By employing advanced imaging techniques, challenges associated with sample contamination can be overcome and valuable insights into the impact of microplastics on marine ecosystems and human consumers are provided.

Quantification and characterization of microplastics in coastal environments: Insights from laser direct infrared imaging

The study identified and quantified nine plastic polymers frequently detected in the environment by collecting sediment and seawater samples from coastal areas in Auckland, New Zealand. Polymer types, size distributions, and number of microplastics (MPs) were analyzed using a laser direct infrared (LDIR) imaging technique. Compared to conventional spectroscopic or microscopic methods, LDIR enabled capturing and quantifying MPs in much lower size ranges (20-5000 μm). The results demonstrated the widespread occurrence of MPs in the Auckland coastal environment, with polyethylene terephthalate (PET) being the most frequently detected plastic polymer. MP contamination levels ranged from 13 to 83 particles per liter of coastal water and from 1200 to 3400 particles/kg of dry sand in beach sediments. Six additional locations were investigated to assess the contribution of MPs from stormwater drains to the coastal environment. The total count of identified MPs extracted from sediments near stormwater drains reached a maximum of 18,000 particles/kg of dry sand, representing an order of magnitude increase compared to MP levels found in beach sediments at the same location. In contrast to the prevalence of PET and polyamide observed in beach sediments and coastal waters, polyurethane and polyethylene emerged as the predominant plastic polymers in the vicinity of stormwater drain sediments, implying that the variation could potentially stem from distinct sources of plastics. This significant disparity in quality and quantity underscored the potential link between urban runoff and MP pollution in marine ecosystems. A sample preparation method using 100 g sediment samples was developed and used to assess and compare MPs detection in sediment samples. The commonly used 5 g sample method showed higher extraction efficiency and better detection of the most abundant MPs, but the new 100 g method enabled the detection of previously missed, less abundant plastics.

Quantitative analysis of nanoplastics in environmental and potable waters by pyrolysis-gas chromatography-mass spectrometry

Nanoplastics are emerging environmental contaminants, but their presence in environmental and potable water remains largely understudied due to the absence of quantitative analytical methods. In this study, we developed and validated a pretreatment method that combines hydrogen peroxide digestion and Amicon® Stirred Cell ultrafiltration (at 100 kDa, approximately 10 nm) with subsequent detection by pyrolysis gas chromatography-mass spectrometry (Pyr-GC/MS). This method allows for the simultaneous identification and quantification of nine selected nanoplastic types, including poly(ethylene terephthalate) (PET), polyethylene (PE), polycarbonate (PC), polypropylene (PP), poly(methyl methacrylate) (PMMA), polystyrene (PS), polyvinylchloride (PVC), nylon 6, and nylon 66, in environmental and potable water samples based on polymer-specific mass concentration. Limits of quantification ranged from 0.01 to 0.44 µg/L, demonstrating the method's ability to quantitatively detect nanoplastics in environmental and potable water samples. Most of the selected nanoplastics were detected at concentrations of between 0.04 and 1.17 µg/L, except for PC, which was consistently below the limit of detection (<0.44 µg/L). The prevalent polymer components in the samples were PE (0.10 - 1.17 µg/L), PET (0.06 - 0.91 µg/L), PP (0.04 - 0.79 µg/L), and PS (0.06 - 0.53 µg/L) nanoplastics. The presented analytical method offers an accurate means to identify, quantify, and monitor nanoplastics in complex environmental and potable water samples. It fills gaps in our understanding of nanoplastic pollution levels, providing a valuable methodology and crucial reference data for future studies.

Effects of groundwater sample volume on identified microplastics in groundwater of an agricultural area in Korea

Groundwater serves various purposes worldwide, including agricultural, drinking, domestic, and industrial uses. In the Republic of Korea, groundwater is used primarily for agricultural purpose. Understanding the quality of groundwater is crucial because microplastics (MPs) can enter groundwater through agricultural activities and potentially pose harm to humans. Therefore, groundwater sampling plays a vital role in determining the presence of MPs. However, the optimal volume of groundwater sampling required for accurate MP assessment remains uncertain. This study examined the optimal sample size for collecting MPs from groundwater in the heavy agricultural area of the Haean Basin, Korea. Groundwater sampling and MP analyses were conducted during the wet and dry seasons of 2022. A total of 500 L of groundwater was continuously sampled in increments of 100 L to 500 L (100, 200, 300, 400, and 500 L). Additionally, we investigated the land use surrounding the sampling wells and the predominant types of plastics used in agriculture. To ensure reliable MP analysis, precautions were taken to minimize plastic contact during sampling, pretreatment, and μ-FTIR analysis. The concentration of MPs in groundwater ranged from 0.04 to 17.77 particles/L during the wet season and from 0 to 0.56 particles/L during the dry season. The highest concentration of MPs was observed at the first 100 L sample volume, with concentrations decreasing as the sampling volume increased. Fragmented particles accounted for 86.3 % during the wet season and 91.5 % during the dry season, whereas fibers constituted 13.7 and 8.5 %, respectively. MPs in the size range of 20-100 μm were predominant in both seasons. The polymers identified in both seasons were polypropylene (PP), polyethylene (PE), polyvinyl chloride (PVC), and polyamide (PA). While some studies suggest that 500 L is the optimal sample volume for assessing MPs in groundwater, the findings of this study indicate that a larger sample volume may be necessary. This study was the first attempt to determine the optimum sample volume required to collect MPs from groundwater, emphasizing the importance of conducting further research to validate these findings.

Impact of a nanofiltration system on microplastic contamination in Geneva groundwater (Switzerland)

Microplastics (MPs) have been observed in the oceans, fresh waters, karstic water and remote water bodies. However, little is known on groundwater contamination, which is a natural resource of utmost importance for millions of people and is often perceived as a reliable source of water. Moreover, nanofiltration is perceived as a reliable technology to remove contaminants from water. In this study, large sample volumes of a silty-sandy gravel aquifer and the corresponding nanofiltered water were analysed for the presence of MPs (> 20 µm) using Fourier transform infrared (FTIR) microscopy. Concentration in ground water was 8 ± 7 MPs/m3 and increased to 36 ± 11 MPs/m3 in nanofiltered water. All MPs had a maximum Ferret diameter lower than 500 µm. Size distribution of MPs was towards the small size class (20-50 µm). In groundwater, 33% of MPs were detected in the smallest size class (20-50 µm) and 67% in the 50-100-µm-size class. In comparison, around 52% of MPs in nanofiltered water were observed in the 20-50 µm size class. Moreover, 33% of the MPs observed in nanofiltered water were in the 50-100 µm size class and 15% in the 100-500-µm-size class. From a chemical point of view, different plastic polymers were identified in groundwater and in nanofiltered water, such as polypropylene (PP), polyvinyl chloride (PVC), ethylene (vinyl acetate) copolymer (EVA), polyethylene (PE), polyethylene terephthalate (PET), polymethyl methacrylate (PMMA) and other polymer materials (such as polystyrene-based copolymers, vinyl-based copolymers). Fibres were observed in all samples, but only a small number of fibres (near 1%) were identified as PP synthetic fibres in nanofiltered water. Furthermore, no clear difference of fibre concentrations was observed between groundwater (232 ± 127 fibres/m3) and nanofiltered water (247 ± 118 fibres/m3). Groundwater had extremely low levels of microplastics, and although the nanofiltration effectively removes suspended particulate matter, it slightly contaminates the filtered water with MPs.

Leaching of organic matter from microplastics and its role in disinfection by-product formation

Natural organic matter (NOM) is the primary precursor of disinfection by-products (DBPs). However, as emerging environmental contaminants continue to increase in natural waters, there is a possibility of new precursors of DBPs. We investigated the potential of microplastics (MPs), a growing environmental concern, for leaching organic matter (OM) and subsequent DBP formation. Two experimental setups were used, including chlorinated water containing MPs (Cl2-MP), and non-chlorinated water containing MPs (Non-Cl2-MP), using polyethylene (PE), polyethylene tetrahydrate (PET), polypropylene (PP), and polyvinyl chloride (PVC) as MP materials. The UV absorbance spectra of Cl2-PET/PP/PVC showed peaks at 218 nm, which were significantly correlated with dissolved organic carbon (DOC), indicating lower aromaticity of the leached OM. The DOC concentrations in Cl2-MP samples were several times higher than those in Non-Cl2-MP samples. The leached OM from MPs formed trihalomethanes (THMs) and haloacetic acids (HAAs) in Cl2-MP samples. Among the MPs tested, PVC showed the highest total THM formation after 7 days, followed by PET, PE, and PP. Brominated THMs were predominant, while HAAs were highly chlorinated. THM formation increased with contact time for PE, PET, and PVC, and decreased for PP. Compared to THMs, the concentration of HAAs was low (highest total THM = 185.5 μg/L per g-MP and highest total HAA = 120.7 μg/L per g-MP). Further, the total THM concentration decreased and the total HAA concentration increased over the reaction period, indicating the leaching of different types of OM with increasing contact time. Additionally, the differences in the pattern of DOC leaching and DBP formation among different MPs suggested changes in the leached OM.

Polyurethane-Degrading Potential of Alkaline Groundwater Bacteria

Plastic waste is a global environmental burden and long-lasting plastic polymers, including ubiquitous and toxic polyurethanes (PUs), rapidly accumulate in the water environments. In this study, samples were collected from the three alkaline groundwater occurrences in the geotectonic regions of the Pannonian basin of northern Serbia (Torda and Slankamen Banja) and Inner Dinarides of western Serbia (Mokra Gora) with aim to isolate and identify bacteria with plastic- and lignocellulose-degrading potential, that could be applied to reduce the burden of environmental plastic pollution. The investigated occurrences belong to cold, mildly alkaline (pH: 7.6-7.9) brackish and hyperalkaline (pH: 11.5) fresh groundwaters of the SO4 - Na + K, Cl - Na + K and OH, Cl - Ca, Na + K genetic type. Full-length 16S rDNA sequencing, using Oxford Nanopore sequencing device, was performed with DNA extracted from colonies obtained by cultivation of all groundwater samples, as well as with DNA extracted directly from one groundwater sample. The most abundant genera belong to Pseudomonas, Acidovorax, Kocuria and Methylotenera. All screened isolates (100%) had the ability to grow on at least 3 of the tested plastic and lignocellulosic substrates, with 53.9% isolates degrading plastic substrate Impranil® DLN-SD (SD), a model compound for PUs degradation. Isolates degrading SD that were identified by partial 16S rDNA sequencing belong to the Stenotrophomonas, Pseudomonas, Paraburkholderia, Aeromonas, Vibrio and Acidovorax genera. Taking into account that plastics, including commonly produced PUs, are widespread in groundwater, identification of PUs-degrading bacteria may have potential applications in bioremediation of groundwater polluted with this polymer.

Nano- and micro-plastic transport in soil and groundwater environments: Sources, behaviors, theories, and models

With the increasing use of plastics, nano- and micro-plastic (NMP) pollution has become a hot topic in the scientific community. Ubiquitous NMPs, as emerging contaminants, are becoming a global issue owing to their persistence and potential toxicity. Compared with studies of marine and freshwater environments, investigations into the sources, transport properties, and fate of NMPs in soil and groundwater environments remain at a primary stage. Hence, the promotion of such research is critically important. Here, we integrate existing information and recent advancements to compile a comprehensive evaluation of the sources and transport properties of NMPs in soil and groundwater environments. We first provide a systematic description of the various sources and transport behaviors of NMPs. We then discuss the theories (e.g., clean-bed filtration and Derjaguin-Landau-Verwey-Overbeek theories) and models (e.g., single-site and dual-site kinetic retention and transport models) of NMP transport through saturated porous media. Finally, we outline the potential limitations of current research and suggest directions for future research. Overall, this review intends to assimilate and outline current knowledge and provide a useful reference frame to determine the sources and transport properties of NMPs in soil and groundwater environments.

Microplastic pollution in the groundwater under a bedrock island in the South China sea

Groundwater is the only freshwater resource on islands. Research on microplastic pollution in groundwater on islands is scarce. This study is the first to explore microplastic pollution in the groundwater under a bedrock island (Dawanshan Island) located in the South China Sea. The influence of hydrogeological factors on the distribution, source, and ageing features of microplastics in the groundwater were investigated. Despite the small scale of industrial and agricultural activities on the island, the amount of microplastics in the groundwater ranged from 34 to 64 particles/L, with over 80% of the microplastics being polyester fibres with diameters smaller than 2 mm, which is comparable to those in coastal cities. These microplastics were originated from inland plastic usage, rather than from the surrounding sea, which was confirmed by the lack of seawater intrusion on the island. Owing to the low permeability of granite, microplastics were mainly distributed in the water of the loose layer of porous sediment, and their quantity decreased with depth. In addition, the abundance of microplastics in pore groundwater increased with an increase in the velocity of groundwater flow. The severity of microplastic pollution in the groundwater increased with an increase and decrease in the content of total dissolved solids and dissolved oxygen, respectively. The microplastics originated from plastic waste disposed of on the island, rather than from seawater intrusion. Also, through groundwater infiltration into exposed soil at recharge areas, artificial wells at residential areas, and water exchange with surface water at valley areas. Microplastics buried in the groundwater aged faster along the migration path of the groundwater. These microplastics threaten the safety of people and plants on the island through exposure resulting from the extraction of groundwater for irrigation, while they endanger marine life through submarine groundwater discharge.

Characterizing microplastics in urban runoff: A multi-land use assessment with a focus on 1-125 μm size particles

Urban areas play a significant role in generating microplastics (MPs) through increased vehicular and human activities, making urban runoff a key source of MP pollution in receiving waterways. The composition of MPs is anticipated to vary with land use; hence, identifying the hotspots of contamination within urban areas is imperative for the targeted interventions to reduce MPs at their sources. This study collected one-liter stormwater runoffs from three different land uses as sheet flow during two storm events to quantify the MPs and identify the polymers transported from land-based sources. The analytical method included a combination of Fourier transform infrared spectrometer, Raman microscope, and Nile red staining techniques. This study analyzed the broad spectrum of MPs, i.e., 1 μm-5 mm, and tire wear and bitumen particles, considered the two major research gaps in stormwater studies. The MP concentrations were 67.7 ± 11.3 pL-1in commercial, 23 ± 10.3 pL-1 in residential, and 168.7 ± 37.1 pL-1in highways. The trend of MP concentrations followed an order of highway > commercial > residential with an exclusive presence of polymethylmethacrylate and ethylene-vinyl acetate in highways; cellophane, methylcellulose, polystyrene, polyamide, and polytetrafluorethylene in commercial; and high-density polyethylene in residential areas. The dominant MP morphology consisted of fragments, accounting for 89 % of the identified MPs, followed by 10 % fibers and 1 % films. This study observed a prevalence of MPs sizes <125 μm constituting 49 % of the total composition. These findings underscore the vital role of land use patterns in shaping MP abundance and reinforce the urgency of implementing effective management strategies to mitigate MP pollution in stormwater runoff.

Quantification of two-site kinetic transport parameters of polystyrene nanoplastics in porous media

In this study, a combination of column experiments, interface chemistry theory and transport model with two-site kinetics was used to systematically investigate the effect of pH on the transport of polystyrene nanoparticles (PSNPs) in porous media. The porous media containing quartz sand (QS) and three kinds of clay minerals (CMs)-kaolinite (KL), illite (IL) and montmorillonite (MT), was used in column experiments to simulate the porous media in the soil-groundwater systems. Experimental results showed that the inhibitory effect of CMs on the transport of PSNPs is weakened as pH increases. The two-dimensional (2D) surface of the DLVO interaction energy (2D-pH-DLVO) was built to calculate the interactions between PSNPs and CMs under different conditions of pH. Results suggested the inflection point of PSNP-QS, PSNP-KL, PSNP-IL and PSNP-MT are 2.42, 3.30, 2.84 and 3.69, respectively. Most importantly, there was a significant correlation between the two-site kinetic parameters related to PSNPs transport and the DLVO energy barrier (DB). The contributions of the interactions of PSNPs-PSNPs and PSNPs-minerals were determined for PSNPs transport in porous media. The critical values of pH related to the migration ability of PSNPs in porous media could be determined by a combination of column experiments, 2D-pH-DLVO and PSNPs transport model. The critical values of pH were 2.95-3.01, 3.22-3.51, 2.98-3.02, 3.31-3.33 for the migration ability of PSNPs in QS, QS + KL, QS + IL and QS + MT porous media, respectively. The stronger migration ability of PSNPs under high pH conditions is attributed to the enhanced deprotonation of the media surface and increased negative surface charge, which increases the electrostatic repulsion between PSNPs and porous media (QS, CMs). Moreover, the agglomeration of PSNPs usually is weaker and the average particle size of agglomerates is smaller under the condition of high pH, thus leading to the stronger migration ability of PSNPs under high pH conditions.

Patterns and variability in the microplastic contamination along the southwest coast of India with emphasis on submarine groundwater discharge sites

Beach sediments of the southwest coast of India were analysed to estimate the microplastic contamination with emphasis on the submarine groundwater discharge (SGD) zones. Both SGD and non-SGD sites were assessed for abundance, morphotype and polymer type of microplastics. Microplastic load was 230.429 ± 62.87 particles per 100 g. Fibre, mainly blue, was the abundant morphotype, followed by fragment, foam and film. The polymer types were POLYETHYLENE (PE) (30.77 %), POLYPROPYLENE (PP) (26.92 %), POLYAMIDE (PA) (19.23 %), POLYSTYRENE (PS) (11.54 %), ETHYLENE VINYL ACETATE (EVA) (7.692 %) and POLYVINYL CHLORIDE (PVC) (3.846 %). The SGD zones exhibited higher microplastic contamination with statistically significant variations from non SGD sites. The study accounts the levels of microplastic contamination along the southwest coast of India, a major fishery zone. The higher abundance of microplastic in the SGD zones indicates the significance of subterranean groundwater through flow as a pathway of anthropogenic contaminants towards marine ecosystems.

A review of microplastic removal from water and wastewater by membrane technologies

Microplastics (MPs) cannot be completely removed from water/wastewater in conventional wastewater treatment plants (WWTPs) and drinking water treatment plants (DWTPs). According to the literature analysis, membrane technologies, one of the advanced treatment technologies, are the most effective and promising technologies for MP removal from water and wastewater. In this paper, firstly, the properties of MPs commonly present in WWTPs/DWTPs and the MP removal efficiency of WWTPs/DWTPs are briefly reviewed. In addition, research studies on MP removal from water/wastewater by microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), reverse osmosis (RO), and membrane bioreactors (MBRs) are reviewed. In the next section, membrane filtration is compared with other methods used for MP removal from water/wastewater, and the advantages/disadvantages of the removal methods are discussed. Moreover, the problem of membrane fouling with MPs during filtration and the potential for MP release from polymeric membrane structure to water/wastewater are discussed. Finally, based on the studies in the literature, the current status and research deficiencies of MP removal by membrane technologies are identified, and recommendations are made for further studies.

Exploring the vertical transport of microplastics in subsurface environments: Lab-scale experiments and field evidence

Microplastics (MPs) defined as smaller 5 mm plastic particles have received increasing attention due to their global occurrence and potential toxicity. This study investigated the effects of environmental factors (rainfall intensity, 13 and 29 mm/h) and MP characteristics (morphology (fiber, flake, and film), polymer type (polypropylene (PP), polyethylene terephthalate (PET), and polystyrene (PS)) and size (100-300, 300-500, and 500-1000 μm)) on the vertical transport of MP in unsaturated soil conditions using lab-scale column experiments. Additionally, the occurrence and characteristics of MP detected in soil/sediment (total 13 samples) and groundwater samples (total 6 samples) were explored in the field study. Laboratory-scale column experiments revealed that heavy rainfall intensity (29 mm/h) increased the degree of MP vertical transport in unsaturated soil conditions and MP fibers showed the greatest vertical mobility among the various morphologies of MPs assessed. For the polymer type and size, the lighter PP polymer or the larger size of MP (500-1000 μm) showed higher mobility. In the field study, a statistical difference in MP abundance was observed depending on the population density and degree of urban development in both soil and groundwater samples. Comparing to the two different types of environmental media samples obtained from the same site, there was a significant difference in the composition of polymer types present while statistically no difference in MP abundance was observed between the two media samples (i.e., soil or sediment and groundwater). In addition, MP fibers and polyethylene (PE) were predominantly detected in our two study areas. These results suggest that various types of MP can pass through the unsaturated zone by water infiltration, even if it takes a long time to reach groundwater. Overall, we found that the degree of vertical transport of the MPs was highly sensitive to environmental conditions and MP characteristics.

Microplastic contamination in groundwater on a volcanic Jeju Island of Korea

Microplastic (MPs) contamination in groundwater has received massive attention since plastic waste has been released directly into the environment. This study investigates MPs contamination in groundwater on the Jeju volcanic Island, Korea. To the best of our knowledge, this is the first study to identify MPs in groundwater from volcanic islands. A total of 21 sites were sampled for groundwater wells and springs in July and September (2021). Sampling was performed without cross-contamination through quality assurance and quality control. The results showed that MPs abundance ranged from 0.006 to 0.192 particles/L in groundwater samples. Additionally, MPs were detected in deep groundwater wells where the groundwater level was 143 m below ground surface. Eight MPs polymer types, including polypropylene, polyethylene, polyethylene terephthalate, polyvinyl chloride, polystyrene, polyamide, acrylonitrile butadiene styrene, and polyurethane, were detected using Micro-Fourier Transform Infrared Spectroscopy (μ-FT-IR). Most of the detected MPs size ranged from 20 to 100 μm, accounting for 95% of the total. Fragments and fiber shaped MPs were detected, with the majority of them being fragmented in groundwater samples. The concentrations of MPs and major ions in groundwater showed a positive correlation. A negative correlation was observed between MPs concentration and topographic elevation (r = -0.59, p = 0.01). The source of MPs contamination is most likely attributed to agricultural activities, such as plastic mulching and greenhouses, which account for most of the land use in the study area. In this study, MPs entered the aquifer through the soil at the surface and seeped through cracks in fractured rock on basalt with sealed groundwater wells. This study takes 500 L of samples to prevent sample bias, reveal plastic contamination in groundwater, and indicating the characteristics and sources of contaminated plastics.

Prevailing impacts of river management on microplastic transport in contrasting US streams: Rethinking global microplastic flux estimations

While microplastic inputs into rivers are assumed to be correlated with anthropogenic activities and to accumulate towards the sea, the impacts of water management on downstream microplastic transport are largely unexplored. A comparative study of microplastic abundance in Boulder Creek (BC), and its less urbanized tributary South Boulder Creek (SBC), (Colorado USA), characterized the downstream evolution of microplastics in surface water and sediments, evaluating the effects of urbanization and flow diversions on the up-to-downstream profiles of microplastic concentrations and loads. Water and sediment samples were collected from 21 locations along both rivers and microplastic properties determined by fluorescence microscopy and Raman spectroscopy. The degree of catchment urbanization affected microplastic patterns, as evidenced by greater water and sediment concentrations and loads in BC than the less densely populated SBC, which is consistent with the differences in the degree of urbanization between both catchments. Microplastic removal through flow diversions was quantified, showing that water diversions removed over 500 microplastic particles per second from the river, and caused stepwise reductions of downstream loads at diversion points. This redistribution of microplastics back into the catchment should be considered in large scale models quantifying plastic fate and transport to the oceans.

Microplastics in caves: A new threat in the most famous geo-heritage in the world. Analysis and comparison of Italian show caves deposits

Microplastic pollution represent a worldwide concern, however, in karst areas is still largely unknown, especially in underground environments. Caves are the most important geological heritage worldwide, rich in speleothems, unique ecosystems custodians of important drinking water reserves, and a significant economic resource. Thank to their relatively stable environmental conditions, they can preserve information for a long time such as paleontological/archaeological remains, however, these characteristics make caves vulnerable environments too, easily damaged by climate variations and pollution. To increase the current knowledge of microplastic pollution, the deposits of different Italian show caves were investigated, improving the method for microplastic separation. Microplastic were identified and characterised using MUPL automated software, observed with and without UV light under a microscope, and verified under μFTIR-ATR, highlighting the importance of combine different methods. Microplastics were present in sediments of all examined caves, and were always greater along the tourist route (an average of 4300 items/kg) than the speleological areas (an average of 2570 items/kg). Microplastics less than 1 mm dominated the samples and the amount increased with the decrease in the size considered. Fibre-shaped dominated the samples and 74% particles was fluorescent under UV light. Analysed sediment samples contained especially polyesters and polyolefins. Our results highlight the presence of microplastic pollution in show caves, giving useful information to assess risks posed by microplastics in show caves and emphasizing the importance of pollutants monitoring in underground environments to define strategies for the conservation and management of caves and natural resources.

First insight into microplastic groundwater pollution in Latin America: the case of a coastal aquifer in Northwest Mexico

Microplastics have been studied on biota and other environmental domains, such as soils. Despite the importance of groundwater as a resource for millions of people worldwide as drinking water and personal hygiene, domestic, agricultural, mining, and industrial purposes, there are very few studies concerning microplastics in this domain around the world. We present the first study in Latin America addressing this topic. Six capped boreholes were analyzed in terms of abundance, concentration, and chemical characterization, at three different depths, from a coastal aquifer in Northwest Mexico. This aquifer is highly permeable and affected by anthropogenic activities. A total of 330 microplastics were found in the eighteen samples. In terms of concentration, the interval ranged from 10 to 34 particles/L, with an average of 18.3 particles/L. Four synthetic polymers were identified: isotactic polypropylene (iPP), hydroxyethylcellulose (HEC), carboxylated polyvinyl chloride (PVC), and low-density polyethylene (LDPE); with iPP being the most abundant (55.8%) in each borehole. Agriculture activities and septic outflows are considered the potential regional sources of these contaminants into the aquifer. Three possible transport pathways to the aquifer are suggested: (1) marine intrusion, (2) marsh intrusion, and (3) infiltration through the soil. More research about the occurrence, concentration, and distribution of the different kinds of microplastics in groundwater is needed to have a better understanding of the behavior and health risks to organisms, including human beings.