Microplastics in landfill and leachate: Occurrence, environmental behavior and removal strategies

Microplastic accumulation dynamics in Han river headwaters: Sediment interactions and environmental implication

The prevalence of microplastic (MP) contamination has become a significant environmental concern due to its pervasive nature and persistent effects. While sediments are considered major repositories for MPs, information on their spatial distribution within these matrices is insufficient. This research examined both the horizontal and vertical presence of MPs in the sediments surrounding Lake Paldang in South Korea, alongside a comprehensive evaluation of the physicochemical characteristics of the samples obtained. The total content of MPs varied from 2.15 to 122.2 particles g-1. The average contents of MPs on surface sediments were 40.47, 34.14, 5.01, and 8.19 particles g-1 in north mainstream (NM), south mainstream (SM), tributary (TB), and Tributary catchment (TC) based on Sonae Island, Gyeongan stream, respectively. The most abundant MP types were polyethylene (PE), polytetrafluoroethylene (PTFE), and polypropylene (PP), accounting for more than 70% of the total MPs. The most abundant sizes of MPs were within 45-100 µm. At all sediment depths, polymers were distributed in the order PE, PP, and polyester in NM, SM, and TC, respectively, whereas PTFE mainly occurred in the surface layer. MPs distribution also exhibited seasonal variation as larger inflows and flow rates varied with season.

Probing Long-Term Impacts: Low-Dose Polystyrene Nanoplastics Exacerbate Mitochondrial Health and Evoke Secondary Glycolysis via Repeated and Single Dosing

Nanoplastics (NPs) are omnipresent in the environment and contribute to human exposure. However, little is known regarding the long-term effects of NPs on human health. In this study, human intestinal Caco-2 cells were exposed to polystyrene nanoplastics (nanoPS) in an environmentally relevant concentration range (102-109 particles/mL) under two realistic exposure scenarios. In the first scenario, cells were repeatedly exposed to nanoPS every 2 days for 12 days to study the long-term effects. In the second scenario, only nanoPS was added once and Caco-2 cells were cultured for 12 days to study the duration of the initial effects of NPs. Under repeated dosing, initial subtle effects on mitochondria induced by low concentrations would accrue over consistent exposure to nanoPS and finally lead to significant impairment of mitochondrial respiration, mitochondrial mass, and cell differentiation process at the end of prolonged exposure, accompanied by significantly increased glycolysis over the whole exposure period. Single dosing of nanoPS elicited transient effects on mitochondrial and glycolytic functions, as well as increased reactive oxygen species (ROS) production in the early phase of exposure, but the self-recovery capacity of cells mitigated these effects at intermediate culture times. Notably, secondary effects on glycolysis and ROS production were observed during the late culture period, while the cell differentiation process and mitochondrial mass were not affected at the end. These long-term effects are of crucial importance for comprehensively evaluating the health hazards arising from lifetime exposure to NPs, complementing the extensively observed acute effects associated with prevalent short-term exposure to high concentrations. Our study underlines the need to study the toxicity of NPs in realistic long-term exposure scenarios such as repeated dosing.

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.

Geochemical, mineralogical records, and statistical approaches in establishing sedimentary in the environment of a Mediterranean coastal system: case of Sebkha El-Guettiate (southeastern Tunisia)

The current study was conducted within the context of the Holocene era in Sebkha El-Guettiate, located in southeastern Tunisia. The aim was to determine the factors influencing the geochemical and mineralogical composition of sediments and to elucidate the sedimentary characteristics of the Holocene within the Sebkha core. We examined a sediment core extending 100 cm from this Sebkha, subjecting it to comprehensive analysis to uncover its sedimentological, mineralogical, and geochemical properties. Several techniques were employed to strengthen and validate the connections between geochemical and mineralogical analyses, including X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM), and infrared (IR) spectroscopy, among others. Furthermore, statistical analyses utilizing principal component analysis (PCA) were applied to the results of the geochemical and mineralogical studies, aiding in the identification of patterns and relationships. A comprehensive mineralogical assessment of the core's sediments revealed the presence and interpretation of carbonate minerals, evaporite minerals, and detrital minerals. Through the application of infrared (IR) spectrometer techniques to all sediment samples, we gained insight into the mineralogical components and the distribution of key elements such as quartz, kaolinite, calcite, feldspar, and organic carbon. The geochemical composition demonstrated a clear dominance of silica (SiO2), accompanied by fluctuations in carbonate percentages (CaCO3). The prominent major elements, primarily magnesium (Mg) and calcium (Ca) originating from dolomitization, sodium (Na) and chlorine (Cl) from halite, and calcium (Ca) from gypsum, exhibited varying levels. Results from Rock-Eval 6 pyrolysis indicated that the organic matter within the sediments is generally a mixture of terrestrial and aquatic origins. This study provides practical information that underscores the diverse origins contributing to Sebkha sediment formation, often influenced by saline systems.

Leachate from municipal solid waste landfills: A neglected source of microplastics in the environment

Over the past decade or so, microplastics (MPs) have received increasing attention due to their ubiquity and potential risk to the environment. Waste plastics usually end up in landfills. These plastics in landfills undergo physical compression, chemical oxidation, and biological decomposition, breaking down into MPs. As a result, landfill leachate stores large amounts of MPs, which can negatively impact the surrounding soil and water environment. However, not enough attention has been given to the occurrence and removal of MPs in landfill leachate. This lack of knowledge has led to landfills being an underestimated source of microplastics. In order to fill this knowledge gap, this paper collects relevant literature on MPs in landfill leachate from domestic and international sources, systematically summarizes their presence within Asia and Europe, assesses the impacts of landfill leachate on MPs in the adjacent environment, and particularly discusses the possible ecotoxicological effects of MPs in leachate. We found high levels of MPs in the soil and water around informal landfills, and the MPs themselves and the toxic substances they carry can have toxic effects on organisms. In addition, this paper summarizes the potential impact of MPs on the biochemical treatment stage of leachate, finds that the effects of MPs on the biochemical treatment stage and membrane filtration are more significant, and proposes some novel processes for MPs removal from leachate. This analysis contributes to the removal of MPs from leachate. This study is the first comprehensive review of the occurrence, environmental impact, and removal of MPs in leachate from landfills in Asia and Europe. It offers a comprehensive theoretical reference for the field, providing invaluable insights.

Identification of microplastics in raw and treated municipal solid waste landfill leachates in Hong Kong, China

Plastics are indispensable in modern society but also pose a persistent threat to the environment. In particular, microplastics (MPs) have a substantial environmental impact on ecosystems. Municipal solid waste landfill leachates are a source of MPs, but leakage of MPs from leachates has only been reported in a few studies. As a modern city, Hong Kong has a remarkably high population density and a massive plastic waste generation. However, it depends on conventional landfilling for plastic waste management and traditional thermal ammonia stripping for leachate treatment. Yet, the MP leakage from landfill leachates in Hong Kong has not been disclosed. This is the first study that aimed to identify, quantify, and characterise MPs in raw and treated leachates, respectively, from major landfill sites in Hong Kong. The concentrations of MPs varied from 49.0 ± 24.3 to 507.6 ± 37.3 items/L among the raw leachate samples, and a potential correlation was found between the concentration of MPs in the raw leachate sample from a given landfill site and the annual leachate generation of the site. Most MPs were 100-500 μm fragments or filaments and were transparent or yellow. Regarding the polymeric materials among the identified MPs, poly(ethylene terephthalate) and polyethylene were the most abundant types, comprising 45.30% and 21.37% of MPs, respectively. Interestingly, leachates treated by ammonia stripping contained higher concentrations of MPs than raw leachate samples, which demonstrated that the traditional treatment process may not be sufficient regarding the removal of emerging pollutants, such as MPs. Overall, our findings provide a more comprehensive picture of the pollution of MPs in landfill leachates in Hong Kong and highlight the urgent need for adopting the consideration of MPs into the conventional mindset of waste management systems in Hong Kong.

Occurrence, transport, and toxicity of microplastics in tropical food chains: perspectives view and way forward

Microplastics, which have a diameter of less than 5 mm, are becoming an increasingly prevalent contaminant in terrestrial and aquatic ecosystems due to the dramatic increase in plastic production to 390.7 million tonnes in 2021. Among all the plastics produced since 1950, nearly 80% ended up in the environment or landfills and eventually reached the oceans. Currently, 82-358 trillion plastic particles, equivalent to 1.1-4.9 million tonnes by weight, are floating on the ocean's surface. The interactions between microorganisms and microplastics have led to the transportation of other associated pollutants to higher trophic levels of the food chain, where microplastics eventually reach plants, animals, and top predators. This review paper focuses on the interactions and origins of microplastics in diverse environmental compartments that involve terrestrial and aquatic food chains. The present review study also critically discusses the toxicity potential of microplastics in the food chain. This systematic review critically identified 206 publications from 2010 to 2022, specifically reported on microplastic transport and ecotoxicological impact in aquatic and terrestrial food chains. Based on the ScienceDirect database, the total number of studies with "microplastic" as the keyword in their title increased from 75 to 4813 between 2010 and 2022. Furthermore, various contaminants are discussed, including how microplastics act as a vector to reach organisms after ingestion. This review paper would provide useful perspectives in comprehending the possible effects of microplastics and associated contaminants from primary producers to the highest trophic level (i.e. human health).

Is the application of organic fertilizers becoming an undeniable source of microplastics and resistance genes in agricultural systems?

The application of organic fertilizers is becoming an undeniable source of microplastics and antibiotic resistance genes (ARGs) in agricultural soils. The complex microbial activity further transfers resistance genes and their host bacteria to agricultural products and throughout the entire food chain. Therefore, the current main focus is on reducing the abundance of microplastics and ARGs in organic fertilizers at the source, as well as managing microplastics and ARGs in soil. The control of microplastic abundance in organic fertilizers is currently only achieved through pre-composting selection and other methods. However, there are still many shortcomings in the research on the distribution characteristics, propagation and diffusion mechanisms, and control technologies of ARGs, and some key scientific issues still need to be urgently addressed. The high-temperature composting of organic waste can effectively reduce the abundance of ARGs in organic fertilizers to a certain extent. However, it is also important to consider the spread of ARGs in residual antibiotic-resistant bacteria (ARB). This article systematically explores the pathways and interactions of microplastics and resistance genes entering agricultural soils through the application of organic fertilizers. The removal of microplastics and ARGs from organic fertilizers was discussed in detail. Based on the limitations of existing research, further investigation in this area is expected to provide valuable insights for the development and practical implementation of technologies aimed at reducing soil microplastics and resistance genes.

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.

Environmental pitfalls and associated human health risks and ecological impacts from landfill leachate contaminants: Current evidence, recommended interventions and future directions

The improper management of solid waste, particularly the dumping of untreated municipal solid waste, poses a growing global challenge in both developed and developing nations. The generation of leachate is one of the significant issues that arise from this practice, and it can have harmful impacts on both the environment and public health. This paper presents an overview of the primary waste types that generate landfill leachate and their characteristics. This includes examining the distribution of waste types in landfills globally and how they have changed over time, which can provide valuable insights into potential pollutants in a given area and their trends. With a lack of specific regulations and growing concerns regarding environmental and health impacts, the paper also focuses on emerging contaminants. Furthermore, the environmental and ecological impacts of leachate, along with associated health risks, are analyzed. The potential applications of landfill leachate, suggested interventions and future directions are also discussed in the manuscript. Finally, this work addresses future research directions in landfill leachate studies, with attention, for the first time to the potentialities that artificial intelligence can offer for landfill leachate management, studies, and applications.

Effects of microplastic contamination on the hydraulic, water retention, and desiccation crack properties of a natural clay exposed to leachate

Microplastic (MP) can significantly affect soil behaviour and the ecosystem. This paper presents an experimental study to investigate the effects of MP contamination and leachate exposure on the desiccation cracks, hydraulic conductivity, and water retention properties of the natural black clay. The leachate was from a landfill in Australia. The black clay was incorporated with up to 2.0% MPs by weight (w/w) with diverse dimensions and mixed with water/leachate. The measured properties include saturated hydraulic conductivity (ksat), soil-water characteristic curves, moisture evaporation rates, and crack intensity factors. The results suggest that the inclusion of MPs significantly increases ksat, and this increase is more obvious for soils with larger dimensions and contents of MPs, e.g., ksat of the black clay with 2.0% of 500 μm MP increases significantly by 206% (p < 0.05). The black clay exposed to leachate exhibits a slight increase in ksat due to the low viscosity of leachate. The existence of MPs decreases the residual moisture contents and air-entry pressures, and so does the water retention capacity (v/v %) of the black clay. The exposure to leachate increases the air-entry pressures by 6.0%-15.8% of the clay. The evaporation rates increase with the dimensions and concentrations of MPs. The highest evaporation rate (0.96 g/h) can be observed in samples exposed to 2.0% 500 μm MP with water addition. For all samples, the crack intensity factors increase when MP content is between 0.2% and 1.0% and decreases slightly after that. After being exposed to leachate, the evaporation rates and crack intensity factors of the black clay are decreased by 2.4%-12.6% and 3.6%-13.7%, respectively.

Microplastics in the Asia-Pacific Region in the Plasticene Era: Exposures and Health Risks

Within the broader Anthropocene Epoch resides the Plasticene Era, where humans are subjected pervasively to nano- and microplastics (NMPs). Human's widespread exposure with NMPs occurs through the air we breathe, water we drink, and food we eat. NMP sources are wide and varied; atmospheric NMPs are largely attributed to fibres from car tyres and synthetic clothing, while particles from food packaging, personal care products, and plastic manufacturing contribute significantly to food and water contamination. NMPs have become inherent within the human body and have been found in every organ. As such, the evidence base around adverse health effects is fragmented but growing. This article presents a mini-review and report of sessions presented about NMPs at the 19th International Conference of the Pacific Basin Consortium for Environment and Health, held on Jeju Island, in 2022. Abundant evidence of substantial exposure to NMPs in the Asia-Pacific region has been exhibited. Addressing this issue necessitates the collaboration of policymakers, manufacturers, and researchers to develop safer alternatives and implement mitigation and remediation strategies. The ongoing development of a new United Nations-led global plastic treaty presents a crucial opportunity that must be acted on and not be compromised.

Microplastic, a possible trigger of landfill sulfate reduction process

The environmental impact of microplastics (MPs) formed from landfill has not been gained enough attention. This research investigated the characteristics of the MPs occurrence in landfills through field sampling. It shows that the MPs abundance in the landfill surface soil and non-landfill areas can reach 3573 items·g-1 and 3041 items·g-1, respectively. The vertical abundance of MPs increases significantly with depth, ranging from 387 to 11,599 items·g-1 with small size (≤10 μm, 65.61 %) and flake or wedge shape (38.48 %). The leachate movement in a longitudinal direction enables MPs to accumulate more easily in the landfill bottom layer with high moisture abundance. The abundance of MPs are significantly correlated with SO42- and S2- content, the two typical metabolic substrate and product of sulfate reduction process. In such heterogeneous environment, this significant correlation is not a random phenomenon in terms of the MPs have known substantial impact on biogeochemical processes. Microplastic is a possible trigger of landfill odor emission related with sulfate reduction. This research could serve as a reference for MPs and odor pollution management in landfills.

A comprehensive review of micro- and nano-plastics in the atmosphere: Occurrence, fate, toxicity, and strategies for risk reduction

Micro- and nano-plastics (MNPs) have received considerable attention over the past 10 years due to their environmental prevalence and potential toxic effects. With the increase in global plastic production and disposal, MNP pollution has become a topic of emerging concern. In this review, we describe MNPs in the atmospheric environment, and potential toxicological effects of exposure to MNPs. Studies have reported the occurrence of MNPs in outdoor and indoor air at concentrations ranging from 0.0065 items m-3 to 1583 items m-3. Findings have identified plastic fragments, fibers, and films in sizes predominantly <1000 μm with polyamide (PA), polyester (PES), polyethylene terephthalate (PET), polypropylene (PP), rayon, polyethylene (PE), polystyrene (PS), polyvinyl chloride (PVC), polyacrylonitrile (PAN), and ethyl vinyl acetate (EVA) as the major compounds. Exposure through indoor air and dust is an important pathway for humans. Airborne MNPs pose health risks to plants, animals, and humans. Atmospheric MNPs can enter organism bodies via inhalation and subsequent deposition in the lungs, which triggers inflammation and other adverse health effects. MNPs could be eliminated through source reduction, policy/regulation, environmental awareness and education, biodegradable materials, bioremediation, and efficient air-filtration systems. To achieve a sustainable society, it is crucial to implement effective strategies for reducing the usage of single-use plastics (SUPs). Further, governments play a pivotal role in addressing the pressing issue of MNPs pollution and must establish viable solutions to tackle this significant challenge.

Single and combined toxicity of polystyrene nanoplastics and PCB-52 to the aquatic duckweed Spirodela polyrhiza

As nanoplastics and persistent organic pollutants are broadly distributed in aquatic ecosystems and pose a potential threat to ecosystem, most pertinent studies have focused on aquatic animals, while studies on freshwater plants have been rarely reported. Therefore, we analyzed the single and combined toxicological impacts of various concentrations of 80 nm polystyrene nanoplastics (PS-NPs) including 0.5, 5, 10, and 20 mg/L and polychlorinated biphenyl-52 (PCB-52, 2,2',5,5'- tetrachlorobiphenyl) at 0.1 mg/L on the aquatic plant Spirodela polyrhiza (S. polyrhiza) after a 10-day hydroponic experiment. Laser confocal scanning microscopy (LCSM) showed the accumulation of PS-NPs mainly in the root surface and the lower epidermis of leaves, and the enrichment of PS-NPs was aggravated by the presence of PCB-52. PS-NPs at 10 mg/L and 20 mg/L alone or in combination with PCB-52 notably inhibited the growth of S. polyrhiza, reduced the synthesis of chlorophylls a and b, and increased the activities of superoxide dismutase (SOD) and peroxidase (POD) as well as malondialdehyde (MDA) levels, and induced osmotic imbalance (soluble protein and soluble sugar contents) (p < 0.05). However, a single treatment with low levels of PS-NPs had positive effects on the growth (0.5 mg/L) and photosynthetic systems (0.5, 5 mg/L) of S. polyrhiza, while co-exposure exacerbated the damaging impacts of PS-NPs on the antioxidant defense system of S. polyrhiza, which was more pronounced in the roots. Furthermore, correlation analysis revealed that plant growth parameters were positively correlated with chlorophyll a and b content and negatively correlated with soluble sugars, antioxidant enzymes, lipid peroxidation, and carotenoid content (p < 0.05). These results provide data to improve the understanding of the single and combined ecotoxicological effects of nanoplastics and polychlorinated biphenyls (PCBs) in aquatic plants and their application in phytoremediation measures.

Unveiling the effect of microplastics on agricultural crops - a review

Microplastics (MPs), ever since they were identified as a potential and widely distributed persistent contaminant, the number of studies highlighting their impacts on various terrestrial ecosystems have been increasing. Recently, the effect of MPs on the agricultural ecosystem has gained momentum. Hence, the present review examines the impact of microplastics on agricultural crop systems and the mechanism underlying its toxicity. The current review revealed that most of the studies were conducted at a laboratory scale and under controlled conditions. Additionally, it was observed that polystyrene (PS) followed by polyethylene (PE) are the most studied polymer type, while the most studied plants are wheat and maize. Hitherto, literature studies suggest that the microplastics' influence on plant growth can be negative or sometimes neutral; while in some cases it exerts a hormetic effect which depends on other factors determining plant growth. Notably, the main mechanisms through which microplastics influence plant growth are mechanical damage, alteration of soil properties, or by leaching of additives. Overall, with burgeoning research interest in this aspect, the current review has significant implications for the toxicity of MPs on plants and throws light on the need to develop novel guidelines toward the sustainable use of plastics in agricultural sector. However, realistic field-level studies and estimating the MPs concentration at various region are essential to develop remediation approaches. Future studies should also focus on translocation and accumulation of micron sized MPs in edible portion of crops and their effect on food safety.

Physical and chemical characterization and pollution index applied in the assessment of the polluting potential of leachate from urban landfills

During the operation of the landfills, leachate should be managed with caution to avoid possible negative environmental impacts. Considering this, the present study aims to evaluate the relationship between different variables in the leachate composition and elucidate the transformation processes through which this effluent passes during the landfill's period of operation. The study was conducted with eight sanitary landfills from the state of Minas Gerais, in southeastern Brazil, and used descriptive statistical analysis, principal component analysis (PCA), correlation analysis, and calculation of the leachate pollution index (LPI). The biochemical oxygen demand (BOD5)/chemical oxygen demand (COD) ratio was between 0.20 and 0.60. We also observed a significant correlation of 0.45 between Cl- and N-NH4+, which reflects the biological degradation processes that contribute to the presence of both variables. The PCA showed that inorganic variables and organic matter dominated the first component, with coefficients above 0.65, indicating the importance of those variables in determining the general data variability. The LPI values were between 15.26 and 25.97, with BOD5, COD, and N-NH4+ having sub-indexes above 35, being the main variables that increase the pollution potential of the leachate. On the other hand, trace metals present sub-indexes below 7 due to precipitation caused by increased pH and the characteristics of the waste discarded in landfills. The study provides essential information regarding the landfill leachate characteristics and its variation over time, which can contribute to the definition of treatment technologies for this affluent in different scenarios.

Microplastic polyamide toxicity: Neurotoxicity, stress indicators and immune responses in crucian carp, Carassius carassius

This study aimed to determine the toxicity standard and potential risks and effects of polyamide (PA) exposure on neurotoxicity, stress indicators, and immune responses in juvenile crucian carp Carassius carassius. Numerous microplastics (MPs) exists within aquatic environments, leading to diverse detrimental impacts on aquatic organisms. The C. carassius (mean weight, 23.7 ± 1.6 g; mean length, 13.9 ± 1.4 cm) were exposed to PA concentrations of 0, 4, 8, 16, 32 and 64 mg/L for 2 weeks. Among the neurotransmitters, the acetylcholinesterase (AChE) activity in the liver, gill, and intestine of C. carassius was significantly inhibited by PA exposure. Stress indicators such as cortisol and heat shock protein 70 (HSP70) in the liver, gill, and intestine of C. carassius were significantly increased, while immune responses to lysozyme and immunoglobulin M (IgM) were significantly decreased. Our study demonstrates the toxic effects of MP exposure on crucian carp's neurotoxicity, stress indicators, and immune responses.

Effects of micro(nano)plastics on soil nutrient cycling: State of the knowledge

The ecological impacts of micro(nano)plastics (MNPs) have attracted attention worldwide because of their global occurrence, persistence, and environmental risks. Increasing evidence shows that MNPs can affect soil nutrient cycling, but the latest advances on this topic have not systematically reviewed. Here, we aim to present the state of knowledge about the effects of MNPs on soil nutrient cycling, particularly of C, N, and P. Using the latest data, the present review mainly focuses on three aspects, including (1) the effects and underlying mechanisms of MNPs on soil nutrient cycling, particularly of C, N and P, (2) the factors influencing the effects of MNPs on soil nutrient cycling, and (3) the knowledge gaps and future directions. We conclude that MNPs can alter soil nutrient cycling via mediating soil nutrient availability, soil enzyme activities, functional microbial communities, and their potential ecological functions. Furthermore, the effects of MNPs vary with MNPs characteristics (i.e., polymeric type, size, dosage, and shape), chemical additives, soil physicochemical conditions, and soil biota. Considering the complexity of MNP-soil interactions, multi-scale experiments using environmental relevant MNPs are required to shed light on the effects of MNPs on soil nutrients. By learning how MNPs influence soil nutrients cycles, this review can guide policy and management decisions to safeguard soil health and ensure sustainable agriculture and land use practices.

Effect of ultrasonication conditions on polyethylene microplastics sourced from landfills: A precursor study to establish guidelines for their extraction from environmental matrices

Establishing concentration of microplastics (MPs), designated as CMP, in aqueous, semi-solid and solid samples originating from unscientifically created landfills/dumpsites (UCLDs) and engineered landfills (ELFs) is of utmost importance to assess their impact on the geoenvironment. However, the accuracy of CMP will be guided by the extraction efficiency of MPs from these samples. The extraction of MPs from semi-solid and solid samples of UCLDs/ELFs would be cumbersome, mainly due to their trapping in solid aggregates (including organic matter). Such aggregates need to be dispersed to release the MPs, which can be achieved through the assistance of ultrasonication (US) in the presence of an appropriate dispersing agent. However, mere dispersion of solid aggregates during the US might not result in the complete release of MPs adhered (AMPs) to MPs native (NMPs) to these samples. This is because MPs would adhere to the surface of the adjacent ones due to various physical-mechanical-thermal-chemical processes that prevail in landfills. Hence, guidelines for US-assisted extraction of MPs should be developed by considering an approach that would ensure (i) cleaning of NMPs' surface and (ii) release of AMPs without damaging the former. This necessitates understanding the influence of US parameters such as energy applied (Eus), time (tus) and direct/indirect exposure of NMPs from landfills that would control CMP. In this context, the influence of above mentioned US parameters on the (i) surface cleaning of polyethylene NMPs and (ii) release of AMPs and their concentrations (CAMP) was investigated. It was observed that Eus equal to 500 kJ/L during the indirect method of US would result in surface cleaning of NMPs and complete release of AMPs without damaging the farmer's structure. The present work acts as a precursor study to establish the guidelines for the US-assisted extraction of MPs in environmental samples. Also, a generalized relationship between Eus and CAMP, which can be employed to study the impact of landfill type on the release of MPs during the US was developed.

A critical review on nanoplastics and its future perspectives in the marine environment

Nanoplastics (plastic particles smaller than 1 μm) are the least-known type of marine litter. Nanoplastics (NPs) have attracted much interest in recent years because of their prevalence in the environment and the potential harm they can cause to living organisms. This article focuses on understanding NPs and their fate in the marine environment. Sources of NPs have been identified, including accidental release from products or through nano-fragmentation of larger plastic debris. As NPs have a high surface area, they may retain harmful compounds. The presence of harmful additives in NPs poses unique practical challenges for studies on their toxicity. In this review, several methods specifically adapted for the physical and chemical characterization of NPs have been discussed. Furthermore, the review provides an overview of the translocation and absorption of NPs into organisms, along with an evaluation of the release of potential toxins from NPs. Further, we have provided an overview about the existing methods suggested for the possible degradation of these NPs. We conclude that the hazards of NPs are plausible but unknown, necessitating a thorough examination of NPs' sources, fate, and effects to better mitigate and spread awareness about this emerging contaminant.

Economic viability analysis of recycling waste plastic as aggregates in green sustainable concrete

Plastic waste management is one of the major global challenges at present. Recycling single used plastic waste as partial replacement of natural aggregates in concrete may reduce problems regarding mismanagement of plastic waste and unsustainable utilisation of natural resources as aggregates. This concept has been explored in many studies and positive results are obtained, but it has not been materialized at a large scale due to the uncertainty regarding economic viability. The present study therefore focuses on the economic aspects of using Polyethylene based fine aggregates and Polyethylene Terephthalate based coarse aggregates as partial replacement (10%, 20%, 30% and 40%) of natural fine and coarse aggregates separately and simultaneously, with special emphasis given on environmental and social cost. A material flow diagram using STAN is first developed to calculate plastic waste generation. An industrial survey has been conducted to estimate production cost of plastic aggregates, while social cost as WTP is determined through CVM method. The result shows that the total cost of concrete decreases with increase of replacement percentage and cost reduction varies between 0.65% and 7.58% compare to conventional concrete depending on the percentage and type of replacement without compromising strength. So, alongside being hugely beneficial to environment and society in terms of reduction of leachate and greenhouse gas generation, micro-plastic pollution, requirement of landfill area, mosquito borne diseases, erosion, sedimentation, land loss etc.; the concept of recycling plastic waste as partial replacement of natural aggregates in concrete has been proved to be economically viable and beneficial too.

Microplastics in landfill leachate: Occurrence, health concerns, and removal strategies

Landfills are commonly used to manage solid waste, but they can contribute to microplastic (MPs) pollution. As plastic waste degrades in landfills, MPs are released into the surrounding environment, contaminating soil, groundwater, and surface water. This poses a threat to human health and the environment, as MPs can adsorb toxic substances. This paper provides a comprehensive review of the degradation process of macroplastics into microplastics, the types of MPs found in landfill leachate (LL), and the potential toxicity of microplastic pollution. The study also evaluates various physical-chemical and biological treatment methods for removing MPs from wastewater. The concentration of MPs in young landfills is higher than in old landfills, and specific polymers such as polypropylene, polystyrene, nylon, and polycarbonate contribute significantly to microplastic contamination. Primary treatments such as chemical precipitation and electrocoagulation can remove up to 60-99% of total MPs from wastewater, while tertiary treatments such as sand filtration, ultrafiltration, and reverse osmosis can remove up to 90-99%. Advanced techniques, such as a combination of membrane bioreactor, ultrafiltration, and nanofiltration (MBR + UF + NF), can achieve even higher removal rates. Overall, this paper highlights the importance of continuous monitoring of microplastic pollution and the need for effective microplastic removal from LL to protect human and environmental health. However, more research is needed to determine the actual cost and feasibility of these treatment processes at a larger scale.

Nutrient recovery from municipal solid waste leachate in the scope of circular economy: Recent developments and future perspectives

Holistically considering the current situation of the commercial synthetic fertilizer (CSF) market, recent global developments, and future projection studies, dependency on CSFs in agricultural production born significant risks, especially to the food security of foreign-dependent countries. The foreign dependency of countries in terms of CSFs can be reduced by the concepts such as the circular economy and resource recovery. Recently, waste streams are considered as a source in order to produce recovery-based fertilizers (RBF). RBFs produced from different waste streams can be substituted with CSFs as input for agricultural applications. Municipal solid waste leachate (MSWL) is one of the waste streams that have a high potential for RBF production. Distribution of the published papers over the years shows that this potential was noticed by more researchers in the millennium. MSWL contains a remarkable amount of nitrogen and phosphorus which are the main nutrients required for agricultural production. These nutrients can be recovered with many different methods such as microalgae cultivation, chemical precipitation, ammonia stripping, membrane separation, etc. MSWL can be generated within the different phases of municipal solid waste (MSW) management. Although it is mainly composed of landfill leachate (LL), composting plant leachate (CPL), incineration plant leachate (IPL), and transfer station leachate (TSL) should be considered as potential sources to produce RBF. This study compiles studies conducted on MSWL from the perspective of nitrogen and phosphorus recovery. Moreover, recent developments and limitations of the subject were extensively discussed and future perspectives were introduced by considering the entire MSW management. Investigated studies in this review showed that the potential of MSWL to produce RBF is significant. The outcomes of this paper will serve the countries for ensuring their food security by implementing the resource recovery concept to produce RBF. Thus, the risks born with the recent global developments could be overcome in this way besides the positive environmental outcomes of resource recovery.

Masses and size distributions of mechanically fragmented microplastics from LDPE and EPS under simulated landfill conditions

Landfills contain significant amounts of plastic waste (PW) and microplastics (MPs). However, the contributions of various PW fragmentation processes to the quality and quantity of MPs in landfills are unclear. In this study, LDPE and EPS pieces were mixed with sand to simulate landfilled solid waste, which experienced one-dimensional abiotic compression under vertical stress of 100-800 kPa for 1-300 days. The generated MPs were stained and quantified with a fluorescent microscope. The numbers and masses of the fragmented MPs increase with the increasing compression stress and duration following linear or exponential trends. EPS has a lower stiffness than LDPE, thus generates more MPs under the same compression conditions. Stress-dependent and time-dependent fragmentation mechanisms are distinguished, the former is driven by sand-plastic porosity reduction and the latter is due to microscopic interfacial creep with minimal porosity reduction. Most of the mechanically fragmented MPs have diameters < 100 µm. The MPs size distributions follow an established power-law model, which are dependent on stress, duration, porosity reduction, and fragmentation mechanism. Our results serve as conservative estimations on long-term MPs generation in real landfills, which provide confirmative and quantitative evidence to support the previous studies reporting the varied MPs abundances and properties within landfills.

Hydrothermal treatment of polyvinyl chloride: Reactors, dechlorination chemistry, application, and challenges

Polyvinyl chloride (PVC) plastic wastes can bring a series of problems during pyrolysis or incineration such as the emission of dioxins, corrosion, slagging in the reactors, etc. Hydrothermal treatment of PVC plastics has been intensively studied as it can efficiently remove chlorine from PVC plastics under relatively mild reaction conditions (220-300 °C) to provide value-added products. Meanwhile, the research progress, knowledge gaps, and challenges in this field have not been well addressed yet. This paper gives a comprehensive review of hydrothermal dechlorination of PVC plastics regarding reactors, process variables and fundamentals, possible applications, and challenges. The main pathways of hydrothermal dechlorination of PVC plastics are elimination and -OH nucleophilic substitution. Catalytic hydrothermal and co-hydrothermal optimize the chemical reactions and transportation, boosting the dechlorination of PVC plastics. Hydrochar derived from PVC plastics, on the one hand, is coalified close to sub-bituminous and bituminous coal and can be used as low-chlorine solid fuel. On the other hand, it is also a porous material with aromatic structure and oxygen-containing functional groups, with good potential as adsorbent or energy storage materials. Further studies are expected to focus on waste liquid treatment, revealing the energy and economic balance, reducing the dechlorination temperature and pressure, expanding the application of products, etc. for promoting the implementation of the hydrothermal treatment of PVC plastic wastes.

Microplastics pollution in freshwater sediments: The pollution status assessment and sustainable management measures

Microplastics (MPs) pollution in freshwater sediments has brought hidden dangers to food and drinking water supply. Implementing sustainable management measures for MPs pollution in freshwater sediments has become an inevitable trend for sustainable development of society. Existing studies still lacked sufficient discussion in sustainable management of MPs pollution in freshwater sediments. This makes it difficult to formulate sustainable management measures for MPs pollution in freshwater sediments. This study analyzed the pollution status of MPs in freshwater sediments from 84 study areas. The results showed that current studies on MPs pollution in freshwater sediments were mainly concentrated in densely populated and economically developed areas. The average abundance of MPs in freshwater sediments from collected study areas was 1290.88 items/kg, this brought a potential threat to sustainable development in surrounding areas. The pollution load level and potential ecological risk level of MPs in freshwater sediments from these study areas were low. Reducing MPs discharge and restricting the use of high-risk polymers are effective ways to prevent the deterioration of MPs pollution status in freshwater sediments. The abundance and types of MPs in freshwater sediments from these study areas were affected by human activities. Sustainable management of MPs pollution in freshwater sediments from collected study areas requires establishing a lifecycle management system for plastic products, and the industrial structures should be optimized. In addition, legislation and market regulation are effective ways to restrict the discharge of plastic wastes. Sustainable management of MPs in freshwater sediments requires the synergy of legislation and market regulation.