Recent advances in biochar-mediated mitigation of microplastics: A comprehensive review on removal mechanisms, toxicity alleviation strategies, and synergistic environmental impacts.

Biochar-derived dissolved organic matter (BC-DOM), a critical byproduct of biochar aging, plays a pivotal role in governing the fate of microplastics (MPs) in terrestrial and aquatic ecosystems. As MPs (<5 mm) proliferate globally, their persistence and ecotoxicity threaten soil health, water quality, and food security, depending on the composition and content of organic compounds. The purpose of this review was to examine and analyze the existing studies to explore and summarize the properties and environmental behavior of BC-DOM, and emerging evidence on how BC-DOM interacts with MPs to influence their environmental behavior. BC-DOM, rich in reactive oxygen species-generating aromatic and lipid-like compounds, accelerates MP degradation by promoting photoaging processes (e.g., via singlet oxygen and hydroxyl radicals) that fragment MPs into smaller, more biodegradable particles. Concurrently, BC-DOM alters MP surface properties, enhancing their hydrophobicity and adsorption capacity for co-contaminants like heavy metals, thereby modulating MP mobility and retention in soils and sediments. For instance, BC-DOM with high SUVA254 values increases MP aggregation in aquatic systems, reducing their bioavailability but potentially prolonging environmental persistence. These interactions carry significant environmental implications: BC-DOM-driven MP degradation could mitigate long-term ecological risks, while its role in MP adsorption may influence contaminant transport across ecosystems. Therefore, long-term studies need to be carried out to fully understand the interaction mechanism between BC-DOM and MPs and its environmental impact to provide a scientific basis for the safe application of BC in soil and aquatic ecosystems.

Efficient degradation of polyethylene microplastics with VUV/UV/PMS: The critical role of VUV and mechanism

• Comprehensive systematic review on microbial bioremediation as a sustainable approach for microplastic (MP) degradation. • Explores bacterial, fungal, and algal degradation mechanisms, emphasizing enzymatic activity, biofilm formation. • Analyses key influencing factors such as polymer crystallinity, molecular weight, and environmental conditions affecting MP biodegradation. • Discusses advanced analytical methods (FTIR, SEM, TGA, and gravimetric analysis) for assessing MP degradation and microbial interactions. • Highlights innovations in bioremediation, including bioaugmentation, genetically engineered microbes, enzymatic bioreactors, and omics technologies for optimizing MP degradation. Microplastic pollution represents an alarming environmental crisis, affecting ecosystems and posing significant threats to biodiversity and human health. This systematic review explores microbial bioremediation as an effective microplastics (MPs) removal approach, focusing on bacterial, fungal, and algal degradation mechanisms. Unlike conventional methods, microbial bioremediation leverages enzymatic activity, biofilm formation, and metabolic pathways to break down MPs into less harmful byproducts. Key influencing factors, such as polymer crystallinity, molecular weight, surface properties, and environmental conditions, play a crucial role in determining microbial degradation efficiency. Analytical methods, including FTIR, SEM, TGA, and gravimetric analysis, provide critical insights into MPs degradation pathways and microbial interactions. Recent innovations, such as bioaugmentation, genetically engineered microbial strains, and enzymatic bioreactors, have further enhanced the efficiency of MPs biodegradation. The integration of omics technologies, including genomics, transcriptomics, proteomics, and metabolomics, has advanced the understanding of microbial metabolic pathways and the identification of novel plastic-degrading enzymes. This review also discusses the specific roles of bacteria, fungi, and algae in MPs degradation, highlighting their enzymatic capabilities and interactions with different polymer types. Despite significant advancements, challenges such as scalability, varying degradation rates across environments, and potential ecological risks remain. Future research should focus on optimizing microbial consortia, improving enzymatic activity, and developing large-scale applications to effectively address MPs pollution.

Changes in physicochemical and leachate characteristics of microplastics during hydrothermal treatment of sewage sludge

A comprehensive review of biochar-derived dissolved matters in biochar application: Production, characteristics, and potential environmental effects and mechanisms

Microplastics (MP), defined as plastic particles ranging from 1 to 5000 µm, have become a significant environmental concern due to the drastic increase in plastic use. Agricultural soils are highly susceptible to MP contamination from both direct and indirect sources such as plasticulture, biosolids application, irrigation systems, and atmospheric deposition. These contaminants disrupt soil physical and biological functions, altering porosity, water retention, and microbial communities essential for nutrient cycling, ultimately impairing plant productivity. MPs also act as vectors for associated pollutants, raising concerns about their transfer to the food chain and potential health risks. Despite these critical impacts, agricultural soils have received far less attention than aquatic systems.The global diversity of soil types poses challenges to the development of standardized protocols for sampling, extraction, and analysis of MPs. Existing methods often lack reproducibility and comparability across regions, hindering effective management strategies. To address these challenges, a harmonized, globally applicable framework is needed. This framework should consider soil properties and ensure reliable identification and quantification of MPs through standardized procedures for sampling, density separation, and polymer-specific analysis, while accounting for particle size and shape. Such protocols will provide a reliable foundation for MP monitoring in soils, while remaining adaptable for diverse research applications.The Soil and Water Management & Crop Nutrition Laboratory (SWMCNL) in Seibersdorf, in collaboration with international experts, has conducted research on MPs. This includes soil incubation experiments using isotopes to monitor organic matter stability and MP degradation. Additionally, methods for extracting MPs from various soil types, including both conventional and biodegradable plastics, area being developed and tested. Recent work has focused on preparing protocols based on methods from the MINAGRIS project, in collaboration with Coordinated Research Project (CRP) experts. These protocols integrate density separation, organic matter removal, and microscopic analysis and provide improved MP recovery rates, particularly for particles larger than 300 µm. Additionally, emphasis was placed on determining the isotopic changes of δ13C by EA-IRMS due to the extraction procedure. This is to support research involving carbon isotopes, such as in incubation experiments. These methodological advances are important steps towards establishing a robust and scalable Standard Operating Procedure (SOP) for MP research in soils.Furthermore, in collaboration with the International Network on Soil Pollution (INSOP) from FAO, we aim to develop global working groups focused on MP extraction, identification and quantification of MPs in soil. INSOP’s overall aim is to stop soil pollution and achieve the global goal of zero pollution, covering assessment and remediation, as well as impacts on the environment and human health. INSOP also aims to strengthen technical capacities, legislative frameworks, and promotes the exchange of experiences and technologies for sustainable soil management and remediation.Aligned with the UN Plastics Treaty, this initiative aims to enhance Member States’ technical capacities to address soil pollution and provide tools for evidence-based policymaking. By integrating harmonized monitoring protocols with adaptable research frameworks, we can better understand MP impacts on agricultural soils and support global efforts to mitigate plastic pollution.

Hydrothermal processing (HTP) is an efficient thermochemical technology to achieve sound treatment and resource recovery of sewage sludge (SS) in hot-compressed subcritical water. However, microplastics (MPs) and heavy metals can be problematic impurities for high-quality nutrients recovery from SS. This study initiated hydrothermal degradation of representative MPs (i.e., polyethylene (PE), polyamide (PA), polypropylene (PP)) under varied temperatures (180–300 °C) to understand the effect of four ubiquitous metal ions (i.e., Fe3+, Al3+, Cu2+, Zn2+) on MPs degradation. It was found that weight loss of all MPs in metallic reaction media was almost four times of that in water media, indicating the catalytic role of metal ions in HTP. Especially, PA degradation at 300 °C was promoted by Fe3+ and Al3+ with remarkable weight loss higher than 95% and 92%, respectively, which was ca. 160 °C lower than that in pyrolysis. Nevertheless, PE and PP were more recalcitrant polymers to be degraded under identical condition. Although higher temperature thermal hydrolysis reaction induced severe chain scission of polymers to reinforce degradation of MPs, Fe3+ and Al3+ ions demonstrated the most remarkable catalytic depolymerization of MPs via enhanced free radical dissociation rather than hydrolysis. Pyrolysis gas chromatography-mass spectrometry (Py GC–MS) was further complementarily applied with GC–MS to reveal HTP of MPs to secondary MPs and nanoplastics. This fundamental study highlights the crucial role of ubiquitous metal ions in MPs degradation in hot-compressed water. HTP could be an energy-efficient technology for effective treatment of MPs in SS with abundant Fe3+ and Al3+, which will benefit sustainable recovery of cleaner nutrients in hydrochar and value-added chemicals or monomers from MPs.

Selectively colonized microbial communities and enriched antibiotic resistance genes (ARGs) in (micro)plastics in aquatic and soil environments make the plastisphere a great health concern. Although microplastics (MPs) are distributed in indoor environments in high abundance, information on the effect of MPs on a microbial community in an indoor environment is lacking. Here, we detected polymers (containing MPs and natural polymers), bacterial communities, and 18 kinds of ARGs in collected indoor dust samples. A significant correlation by Procrustes analysis between bacterial community composition and the abundance of MPs was observed, and correlation tests and redundancy analysis identified specific associations between MP polymers and bacterial taxa, such as polyamide and Actinobacteria. In addition, the abundance of MPs showed a positive correlation with the relative abundance of the ARGs (to 16S RNA), while natural polymers, such as cellulosics, showed positive correlations with the absolute abundance of ARGs and 16S rRNA. Simulated experiments verified that significantly higher bacterial biomasses and ARGs were observed on the surface of cotton, hair, and wool than on MPs, while a higher relative abundance of ARGs was detected on MPs. However, a significantly higher amount of ARG was found on MPs of poly(lactic acid), the biodegradable plastics with the highest yield. In addition to the plastisphere in water and soil environments, MPs in an indoor environment may also affect the bacterial community and specifically enrich ARGs. Moreover, degradable MPs and nondegradable MPs may result in different health hazards due to their distinct effects on bacterial community.

Biochar has received widespread attention as a promising amendment for heavy metal stabilization due to its abundant porosity and surface functional groups. However, the role of biochar-derived dissolved organic matter (BDOM) is usually overlooked. In this study, we systematically investigated the leaching dynamics of BDOM from garden wastes through hydrothermal carbonization (HC), pyrolysis (PC) and hydro/pyrolysis (HPC) and explored their impacts on Cr(vi) environmental behavior in an extremely acidic environment. Results showed that BDOM leaching dynamics followed the first order model, and HC leached more BDOM than PC and HPC, especially for Ar-P, SMP and Ha-L fractions. Although carbonized using various methods, the biochars displayed a similar adsorption capacity for Cr(vi) at an environmental-related concentration of 2 mg L-1. The presence of BDOM accelerated the Cr(vi) adsorption rate on biochars due to their pre-complexing. Simultaneously, HC-BDOM acted as an electron donor and participate in Cr(vi) reduction directly, resulting in the synchronous reduction of Cr(vi) during its adsorption process. However, PC- and HPC-BDOM preferentially acted as electron acceptors, thus competing with Cr(vi) for Fe(ii) oxidation and decreased the Cr(vi) reduction rate. This study suggested that biochar from garden wastes has a great remediation potential for Cr-contaminated land and that BDOM (especially HC-BDOM) plays a significant role in increasing soil organic matter, stabilizing heavy metals and detoxifying toxic substances by oxidation-reduction.

Degradation of microplastics in the natural environment: A comprehensive review on process, mechanism, influencing factor and leaching behavior.

In recent years, microplastics (MPs) and nanoplastics (NPs) have become significant environmental concerns due to their persistent nature and potentially harmful effects on ecosystems and human health. Most of the reported materials and methods for the degradation of such toxic pollutants show limitations such as low recovery, high energy consumption and environmental impacts. As a result, more efficient green materials and methods are the need of the hour. Recently, researchers have reported efficient materials for the degradation of MPs and NPs. Hence, in this chapter, a comprehensive overview of eco-friendly initiatives and preventive measures is highlighted. It covers detailed information about the sources of MPs and NPs and their toxic impact on the environment and human health. It also highlights the existing techniques for processing and degradation of MPs and NPs and the potential of green nanomaterials in the degradation of plastics. The authors believe that this information will pave the way for the design and development of new alternate methods for further implementation.

Microplastics (MPs) are increasingly reported as contaminants in sewage sludge, with wastewater treatment plants retaining approximately 103–106 particles kg−1 of dry sludge. Anaerobic digestion (AD), widely applied for sludge stabilization and energy recovery, does not consistently remove these particles; MPs frequently persist and, at elevated or sensitive loadings, have been shown to affect methane production, microbial communities and sludge quality. In parallel, thermal hydrolysis and related pretreatments are being implemented at full scale to enhance sludge biodegradability, exposing embedded MPs to high temperature and pressure prior to AD. This review compiles and analyzes experimental studies on MPs in sludge pretreatment and AD systems, with an emphasis on how pretreatment severity, MP type, particle size and concentration influence MP transformation and process performance. Reported data indicate that intensified pretreatment accelerates MP aging, causing fragmentation, oxidative surface modification and additive release, while subsequent AD generally induces limited further MP degradation but can be negatively affected through reduced methane yields, shifts in microbial consortia and altered behavior of co-contaminants. Mechanisms implicated include leaching of plastic additives, enhanced oxidative and physiological stress, and formation of plastisphere biofilms that perturb syntrophic interactions. Mitigation approaches, including optimized thermal hydrolysis–AD configurations and the use of carbonaceous sorbents, are assessed with regard to their effects on MP-associated inhibition and their practical constraints. Analytical limitations, uncertainties in MP mass balances and environmental fate, and key research needs for evaluating MP risks and designing MP-resilient sludge treatment and biosolid management strategies are identified.

Hydrodynamics regulates microbial degradation of microplastics by modulating bottom-up and top-down effects in a river-lake confluence zone.

This study investigated the photodegradation of microplastics (MPs) by α-Fe2O3/g-C3N4. The effects of α-Fe2O3/g-C3N4 on MPs' surface were investigated through various techniques. With the addition of α-Fe2O3/g-C3N4 and under visible light irradiation, cracks and folds were observed on the MP films and particles. Compared to the treatment without photocatalyst addition, the mass loss of MPs increased with irradiation time when α-Fe2O3/g-C3N4 was added. Specifically, polystyrene films and particles in water showed 9.94% and 7.81% increased mass loss, respectively. The degradation of MPs using α-Fe2O3/g-C3N4 demonstrated the behavior consistent with the pseudo-first-order kinetic model. The presence of α-Fe2O3/g-C3N4 led to an increase in surface oxygen-containing functional groups and crystallinity while decreasing the average molecular weight of MPs. After 30days of irradiation, the characteristic tensile bands of MPs with α-Fe2O3/g-C3N4 significantly increased, and the detection of carboxyl bands indicated the formation of carboxylic acid, ketones, and lactones as degradation products.

Microplastics (MPs) are an emerging pollutant that needs effective bioremediation strategies. Strategies, including microbial implementation, enzymes, and insect-mediated degradation, have been effectively deployed and reviewed for the biodegradation of MPs. Thus, this review focused on utilizing multiple stressors (biotic and abiotic) to enhance MPs biodegradation. MPs degradation mechanism, major enzymes involved, and stress-mediated bacterial responses are highlighted. The key routes for MPs biodegradation under various stress are covered. Furthermore, the applications of stresses on wastewater treatment plants (WWTPs) for real-world application are also considered. Thermus sp. is reported to remediate polystyrene (PS) by 43.7% at 40-80°C stress, whereas pH stress showed enhanced low-density polyethylene (LDPE) biodegradation (9.9%) under B. krulwichiae. Salinity up to 3M NaCl, when applied to Bacillus sp., showed 48 times higher protease content. Radiation UV-C on P. aeruginosa increased polyethylene/polystyrene (PE/PS) protease activity by 75.47%. The bacterial response to stress was reported to be mediated by enzyme upregulation, biofilm formation, and metabolic shifts. Targeted stress enhanced MPs biodegradation through specific bacterial adaptations and enzymatic activity. Particular stress requires a specific mechanism to accelerate bacterial MPs degradation. Future research should aim to explore the synergistic effects of combined stressors, conduct comprehensive ecological risk assessments, and implement large-scale field trials to ensure the sustainability and ecosystem compatibility of stress-mediated MPs bioremediation.