Contaminant containment for sustainable remediation of persistent contaminants in soil and groundwater

Scoping Review on Mitigating the Silent Threat of Toxic Industrial Waste: Eco-Rituals Strategies for Remediation and Ecosystem Restoration

Background

The problem of toxic industrial waste impacting soil and water quality remains a significant environmental threat, yet comprehensive solutions are lacking. This review addresses this gap by exploring the effects of industrial waste on ecosystems and proposing strategies for remediation. Its aim is to provide a thorough understanding of the issue and suggest actionable solutions to minimize environmental damage.

Methods

A comprehensive scoping review was conducted following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Data were sourced from major academic databases, including Science Direct, Scopus, PubMed, Academic Search Premier, Springer Link, Google Scholar, and Web of Science. A total of 105 relevant articles were included based on strict eligibility criteria. The review process encompassed identification, screening, and eligibility checks, followed by data abstraction and analysis.

Results

The scoping review highlights the severe impact of toxic industrial waste on soil and water quality, emphasizing pollutants such as heavy metals (cadmium, lead, chromium), organic contaminants, and excess nutrients (nitrogen and phosphorus). These pollutants degrade aquatic ecosystems, causing acidification, eutrophication, and oxygen depletion, leading to biodiversity loss and the mobilization of toxic metals. Soil health is similarly compromised, with heavy metal contamination reducing fertility and disrupting microbial communities essential for nutrient cycling. Mitigation strategies, including cleaner production technologies, effluent treatment, bioremediation, and phytoremediation, offer promising solutions. These eco-friendly approaches effectively reduce pollutants, restore ecosystems, and enhance environmental sustainability, thus mitigating the long-term risks posed by industrial waste on soil and water quality.

Conclusions and recommendations

The findings confirm that toxic industrial waste is a critical environmental threat that impacts both aquatic ecosystems and terrestrial soils. Immediate action is necessary to address ecological degradation. Recommended strategies include banning harmful raw materials, pre-treatment of waste, riparian buffering, bioremediation, and stricter regulations to control pollution and safeguard ecosystems.

Iron oxide-MXene-based composite for the removal of copper ions from wastewater

The present work primarily aims to evaluate the adsorption properties of MXene and its nanocomposite, Fe3O4@MXene, for removing heavy metal ions from industrial wastewater. Two-dimensional (2D) MXene nanosheets were combined with Fe3O4 nanoparticles through a hydrothermal synthesis process to create the Fe3O4@MXene nanocomposite. Characterization revealed that Fe3O4 nanoparticles self-assembled onto MXene sheets, forming a structure that enhanced the 2D structure of MXene, with nanoparticles uniformly distributed throughout the nanosheet network. Performance experiments demonstrated that Fe3O4@MXene nanocomposite significantly outperformed pristine MXene in adsorbing heavy metal ions from wastewater. Notably, Fe3O4@MXene nanocomposite achieved an 83% removal efficiency for Cu ions, highlighting its potential as a highly efficient adsorbent in industrial wastewater treatment. This work underscores the viability of Fe3O4@MXene for heavy metal remediation, marking an important step toward practical environmental applications of MXene-based materials.

Insights into the Restoration of Micropolluted Groundwater by Pyrite: The Contribution of Fe(IV) and Outer-Sphere Electron Transfer

Pyrite has been investigated for its potential to modulate the redox microenvironment of groundwater porous media through self-activation. However, the self-purification process of the contaminants by pyrite after their migration from surface water to groundwater has been neglected. This process is accompanied by a decrease in pollutant concentration with a transition from aerobic to anaerobic environments. Here, we selected sulfamethoxazole (SMX), a micropollutant frequently detected in groundwater, as a modeled micropollutant for the investigation. The findings indicate that pyrite could degrade micropollutants SMX (20 μg/L) by self-activation with nearly 100% degradation efficiency under anaerobic conditions. It was also found that •OH was not the primary reactive oxygen species (ROS), but rather the longer-lived and more stable Fe(IV) generated by •OHad-mediated oxidation of structural Fe(III). Additionally, SMX can be degraded by outer-sphere electron transfer with dissolved Fe3+ in the system. Whereas, the reduction product Fe2+ facilitates the supply of electrons to pyrite and promotes the production of Fe (IV). The contributions of Fe(IV) and outer-sphere electron transfer to SMX degradation were 67.5% and 32.5%, respectively. Furthermore, pyrite self-activation exhibited selective oxidation of electron-rich pollutants under anaerobic conditions. This finding provides a new insight into the self-purification of micropollutants in groundwater environments.

Migration and transformation of Pb and Cd in the unsaturated zone induced by water table fluctuations

Heavy metal migration poses serious threats to soil and groundwater environments, especially under fluctuating water table conditions, where the transport and transformation behaviors of heavy metals are more complex and difficult to predict. However, there are still limited studies on the effects of groundwater level fluctuations on the migration and transformation behavior of Pb and Cd in an unsaturated zone. This study conducted column experiments to investigate the migration, transformation, and interaction of Pb and Cd in an unsaturated zone. The results showed that Pb and Cd generally migrate to the upper sand with increasing water levels owing to their higher activity under low pH conditions. After many water table fluctuations, Pb and Cd accumulated in the sand and the Cd content in the lower layer was reduced compared to that in the upper layer. This may be due to the coexistence with Pb, leading to the conversion of some of the Cd in the sand solids to unstable (Cd(OH)2), which is susceptible to migration. The mechanism of the migration and transformation of Pb and Cd may be based on the synergistic effect of single or multiple processes, such as surface adsorption, surface precipitation, homocrystalline substitution, and interlayer cation exchange. The results show that hydrodynamic conditions affect the migration and transformation of Pb and Cd by changing the soil-groundwater hydrochemical environment, and this finding not only deepens the understanding of the heavy metal migration mechanism, but also provides an important scientific basis and technical support for the remediation of contaminated sites in areas of frequent fluctuations of the groundwater table.

Explainable no-code OECD-compliant machine learning models to predict the mutagenic activity of polycyclic aromatic hydrocarbons and their radical cation metabolites

Polycyclic aromatic hydrocarbons (PAHs) are persistent pollutants with well-known genotoxic and mutagenic effects, posing risks to ecosystems and human health. Their hydrophobic nature promotes accumulation in soils and aquatic environments, increasing exposure risks. Upon metabolic activation, PAHs generate reactive species that form DNA adducts, driving their mutagenic potential. This study presents an OECD-compliant methodology that integrates conceptual density functional theory (CDFT) calculations at the GFN2-xTB level with machine learning models to predict PAH mutagenicity. Using quantum chemical descriptors of procarcinogens and radical cation metabolites alongside Ames test data, key electronic properties linked to mutagenicity were identified. Feature selection consistently highlighted radical cation descriptors as key indicators of metabolic activation pathways. Machine learning models - including SPAARC, Random Tree, and JCHAID - achieved validation accuracies exceeding 89 %, with minimal false-negative rates, ensuring conservative predictions for environmental risk assessment. The PSL and CDP electrophilicity frameworks proved particularly effective in modeling DNA damage-related processes. This no-code, freeware-based methodology provides a scalable and cost-effective tool for assessing mutagenic risks in environmentally relevant conditions. The findings reinforce the importance of metabolic activation, validate the radical cation as a reliable proxy for this process, and demonstrate the predictive value of electronic properties in QSAR modeling. These insights support advances in environmental toxicology and contribute to improved strategies for regulatory risk assessment.

Which Pollutants Should Be Prioritized for Control in Multipollutant Complex Contaminated Groundwater of Chemical Industrial Parks?

Increasing chemical pollutants in groundwater within chemical industrial parks pose a critical environmental challenge, necessitating innovative strategies to address contaminants with the highest risks to environmental health and ensure sustainable management. Herein, we investigated 277 chemical pollutants from 367 sampling points across 10 rounds, totaling 1,016,590 measured data points. An environmental health prioritization index (EHPI) was proposed and applied to integrate multiple criteria: occurrence, migration, persistence, bioaccumulation, acute and chronic toxicity, and health effects to rank the target pollutants for priority control. Thirty pollutants were classified as the top-priority group and 81 as high-priority, with metals, polycyclic aromatic hydrocarbons, and haloalkanes ranking highest, while emerging contaminants of concern ranked lower. The top 6 pollutants were beryllium, benzo(g,h,i)perylene, nickel, benzo(a)pyrene, chrysene, and arsenic. The EHPI method was compared against five other weighting schemes, including AHP (analytic hierarchy process), entropy, AHP-entropy, AHP-TOPSIS (technique for order preference by similarity to ideal solution), and entropy-TOPSIS. EHPI effectively captured and integrated the results from more simplistic prioritization schemes. Overall, 38 pollutants are recommended for inclusion in the priority control list, focusing on the top-priority group and high detection and exceedance categories. This framework provides critical guidance for focused monitoring, assessment, and control of the highest-risk groundwater pollutants, supporting more effective environmental and human health protection.

Contamination of per- and poly-fluoroalkyl substances in agricultural soils: A review

Numerous reviews have focused on the chemistry, fate and transport, and remediation of per- and poly-fluoroalkyl substances (PFAS) across various environmental media. However, there remains a significant gap in the literature regarding a comprehensive review specifically addressing PFAS contamination within agricultural soils. Recognizing the threat PFAS pose to ecosystems and human health, this review critically examines the sources of PFAS in agricultural environments, their uptake and translocation within plant systems, and recent advancements in soil remediation techniques. PFAS ingress into agricultural soils primarily occurs through the application of biowastes, wastewater, and pesticides, necessitating a thorough examination of their pathways and impacts. Factors such as carbon chain length, salinity, temperature, and pH levels affect PFAS uptake and distribution within plants, ultimately influencing their transfer through the food web. Moreover, this review explores a range of physical, chemical, and biological strategies currently employed for the remediation of PFAS-contaminated agricultural soils.

Influence of Miscanthus floridulus on Heavy Metal Distribution and Phytoremediation in Coal Gangue Dump Soils: Implications for Ecological Risk Mitigation

Coal gangue dumps, a byproduct of coal mining, contribute significantly to heavy metal contamination, impacting soil and water quality. In order to assess the levels of heavy metal contamination in soils at different stages of abandonment, this study investigated the role of Miscanthus floridulus (M. floridulus) in the spatial distribution and remediation of six heavy metals (Cd, Cr, Mn, Ni, Cu, and Pb) in coal gangue dump soils abandoned for 0, 8, and 12 years in Pingxiang City, Jiangxi Province, China. Fieldwork was conducted at three sites operated by the Pingxiang Mining Group: Anyuan (active, barren), Gaokeng (8 years, natural vegetation), and Qingshan (12 years, partially remediated). Anyuan remains largely barren, while Gaokeng supports natural vegetation without formal remediation. In contrast, Qingshan supports diverse plant species, including M. floridulus, due to partial remediation. Using a randomized design, root exudates, heavy metal concentrations, and soil properties were analyzed. The results showed that Cd poses the highest ecological risk, with concentrations of 64.56 mg kg-1 at the active site, 25.57 mg kg-1 at the 8-year site, and 39.13 mg kg-1 at the 12-year site. Cu and Pb showed accumulation, while Cr and Mn decreased over time. Root exudates from M. floridulus enhanced metal bioavailability, influencing Cd, Cr, and Ni concentrations. These findings highlight the importance of rhizosphere processes in metal mobility and inform sustainable remediation strategies for post-mining landscapes.

Nano-bioremediation for the removal of inorganic and organic pollutants from the soil

Soil pollution is a significant problem due to harmful toxic substances, particularly organic compounds and heavy metals, resulting from various anthropogenic activities. To address this issue, a synergistic approach involving the use of nanotechnology and bioremediation has been proposed. Nano-bioremediation is a very efficient, cost-effective, and environmentally benign approach for reducing both organic and inorganic pollutants. Nanoparticles (NPs) enhance catalytic, adsorptive, and reactive properties, whereas microorganisms and extracts serve as eco-friendly catalysts. The combination of nanomaterials (NMs) and bioremediation techniques has the potential to significantly transform toxic substances either in situ or ex-situ to clean polluted environments. This article reviews recent developments in nano-bioremediation to eliminate organic and inorganic pollutants from contaminated soils. The use of NPs has the potential to enhance soil bioremediation for the removal of harmful substances through immobilization or stimulation of microbial activities and enzymes involved in the remediation process. It also discusses the mechanism of the interaction of NMs with other microorganisms and their roles in the remediation of polluted environments. Finally, the review discusses future perspectives and challenges regarding the importance of interactions between the soil microbiome, NPs, and contaminants to develop microbe-based nano-remediation strategies for organically and inorganically polluted environments.

What drives metal resistance genes in urban park soils? Park age matters across biomes

Although resistance genes are a global concern in ecosystems, the underlying factors responsible for their worldwide dissemination, especially in urban greenspaces, are poorly known. To investigate metal and metal resistance genes (MRGs) accumulation in urban parks, we used ICP-MS to analyze metal concentrations and GeoChip functional gene arrays to analyze MRGs abundances in vegetation types with labile and recalcitrant litter across urban parks and non-urban reference sites in three distinct climatic regions: Boreal (Finland), Temperate (Baltimore, USA), and Tropical (Singapore). Our results indicate that metal concentrations and MRGs abundances in park soils increase with park age across climatic zones, especially so for the dominant metals - Fe and Al - accounting for more than 90% of the total metal content, and others, e.g., Mn, Zn, and Pb. Correspondingly, Fe and Al resistance genes were the most abundant MRGs, representing 23% of all detected MRGs. Vegetation type affected metals and MRGs only in the boreal region, not in temperate or tropical regions, suggesting that vegetation context is not generalizable across climatic zones. Our analyses also indicate that the distribution of resistance genes is only weakly affected by soil properties, but largely associated with accumulation of metals from traffic and industrial sources. Our data further indicate that MRGs and antibiotic resistance genes (ARGs) are co-selected by metal accumulation. The pattern of MRG abundance between old and young parks is similar to that of ARGs, indicating a potential risk for human health in old urban parks. Our findings emphasize the importance of park age and the corresponding cumulative effects of anthropogenic activities as a driver of metal and MRG dynamics in urban soils globally.

Separation and enrichment of Cd and Pb from food and water samples based on a graphene oxide-decorated poly 2-diethylaminoethyl methacrylate nanocomposite by dispersive micro-solid phase extraction (d-μ-SPE)

In this study, a graphene oxide combined with poly(2-diethylaminoethyl methacrylate) (GO@PDEAEMA) nanocomposite was synthesized for the separation and enrichment of Cd and Pb from food and water samples using the dispersive micro-solid phase extraction (d-μ-SPE) technique. The GO@PDEAEMA nanocomposite was synthesized using surface-initiated atom transfer radical polymerization (SI-ATRP) and characterized using various analytical techniques, such as FTIR, FE-SEM, TGA, BET, and XRD. The optimal experimental conditions were pH 8, 0.5 M HNO₃ as eluent, 5 mg of sorbent, and adsorption/desorption times of 0.5 and 1 min, respectively, with a recovery range of 89-101 %. The suggested method showed low limits of detection (LOD) and quantification (LOQ) of 0.11 μg L-1 and 0.37 μg L-1 for Cd and 0.28 μg L-1 and 0.93 μg L-1 for Pb, respectively. The optimal procedure was successfully applied to real water and food samples. The study demonstrates the possibility of using GO@PDEAEMA nanocomposite as an effective sorbent for toxic metal extraction.

An efficient fungi-biochar-based system for advancing sustainable management of combined pollution

Heavy metal (HM) contamination poses significant global environmental threats, impacting ecosystems, public health, and sustainable development. Fungi, as eco-friendly alternatives to chemical treatments, have the potential to reduce HM bioavailability in contaminated soils while promoting plant growth. However, current fungal remediation methods face limitations in efficiency, long-term effectiveness, and the ability to address combined contamination, particularly with naturally occurring strains. Herein, we developed a Trichoderma reesei-Laccase (LAC)-Biochar coupling system (TLBS), based on the structural and electrostatic analyses of LAC's metal-chelated active site (T1 Cu), for the sustainable remediation of combined pollutants, including HMs. In the TLBS, genetically engineered T. reesei produces a mutated LAC with enhanced binding capability for HMs (Ni and Cd). The TLBS enables high-efficiency remediation through three steps. First, lignin-derived biochar serves as both a supportive carrier and an inducer, initiating LAC expression. Second, natural mediators are released due to the interaction between biochar and T. reesei, and LAC is activated by environmental HMs and natural mediators. Finally, TLBS achieved significant reductions in the available concentrations of Ni (93.63%) and Cd (89.68%) and efficiently remediated multiple organic pollutants (71.41-96.79%), including antibiotics and pesticides. Furthermore, the synergistic interaction among TLBS components ensures long-term remediation effects in environments rich in agricultural biomass, making it ideal for eco-friendly farming practices. This in situ amendment strategy, utilizing only green, biodegradable lignocellulosic wastes and environmentally friendly fungi, offers new pathways for the sustainable management of combined contamination and the improvement of human health.

Revisiting biochemical pathways for lead and cadmium tolerance by domain bacteria, eukarya, and their joint action in bioremediation

With the advent rise is in urbanization and industrialization, heavy metals (HMs) such as lead (Pb) and cadmium (Cd) contamination have increased considerably. It is among the most recalcitrant pollutants majorly affecting the biotic and abiotic components of the ecosystem like human well-being, animals, soil health, crop productivity, and diversity of prokaryotes (bacteria) and eukaryotes (plants, fungi, and algae). At higher concentrations, these metals are toxic for their growth and pose a significant environmental threat, necessitating innovative and sustainable remediation strategies. Bacteria exhibit diverse mechanisms to cope with HM exposure, including biosorption, chelation, and efflux mechanism, while fungi contribute through mycorrhizal associations and hyphal networks. Algae, especially microalgae, demonstrate effective biosorption and bioaccumulation capacities. Plants, as phytoremediators, hyperaccumulate metals, providing a nature-based approach for soil reclamation. Integration of these biological agents in combination presents opportunities for enhanced remediation efficiency. This comprehensive review aims to provide insights into joint action of prokaryotic and eukaryotic interactions in the management of HM stress in the environment.

Theoretical Study on Adsorption of Halogenated Benzenes on Montmorillonites Modified With M(I)/M(II) Cations

Halogenated benzenes (HBs) are hydrophobic organic chemicals belonging to persistent organic pollutants. Owing to their persistence, they represent a serious problem in environmental contamination, specifically of soils and sediments. One of the most important physical processes determining the fate of HBs in soils is adsorption to main soil components such as soil organic matter and soil minerals. Smectites, layered clay minerals of the 2:1 type, are common minerals in clay-rich soils, of which montmorillonite (Mt) is a typical representative. This work focuses on a systematic modeling study of the adsorption mechanism of selected HBs interacting with the basal (001) surface, which is the dominant surface of Mt particles. The HB···Mt interactions were studied by means of a quantum chemical approach based on the density functional theory method. HBs were represented by five molecules, particularly C6F6, C6Cl3F3, C6Cl6, C6Br3Cl3, and C6Br6. In mixed HBs (C6Cl3F3 and C6Br3Cl3) Cl atoms are in 1,3,5 or rather 2,4,6 positions. The effect of a different cation type on adsorption was investigated for M+/M2+-Mt models with cations from alkali group (M+: Li, K, Na, Rb, Cs) and alkaline earth metal group (M2+: Mg, Ca, Sr., Ba). The calculations were also performed on the gas phase HB···M+/M2+ complexes for comparison. Adsorption energies and distances of the main HB molecular plane from the Mt surface were calculated as a measure of the adsorption strength. The results showed that the strongest HB adsorption is for the Na+-Mt and Ca2+-Mt surfaces. The strongest affinity was observed for hexabromobenzene, while the weakest adsorption was found for hexafluorobenzene. The decomposition of the adsorption energy showed that its dominant component is dispersion energy and less important is the cation-π interaction. The calculated adsorption energies showed a good correlation with experimentally determined log Kd values.

Accumulation and distribution of cadmium at organic-mineral micro-interfaces across soil aggregates

Soil amendments are crucial in regulating cadmium (Cd) distribution as aggregates of varying sizes have different capacities to retain soil Cd. Directly observing the Cd distribution within aggregates and understanding their interactions with minerals and carbon at the submicron scale remain significant challenges. Pot experiments were conducted to assess the impacts of mineral, organic, and microbial amendments on the Cd distribution in soil aggregates using synchrotron radiation-based Fourier transform infrared (SR-FTIR) spectroscopy and nano-scale secondary ion mass spectrometry (NanoSIMS). Our results revealed that different soil amendments exerted varying effects on Cd accumulation in soil aggregates. The mineral and microbial amendments facilitated the Cd transfer from the macroaggregates to the silt+clay fraction, while the organic amendment increased the Cd loading in the macroaggregates. Additionally, the mineral and microbial amendments reduced the binding of Fe oxides with microbial-derived peptides in the macroaggregates and enhanced the interaction of Fe oxides with plant-derived lignin in the silt+clay fractions. Furthermore, NanoSIMS analysis provided direct evidence that the mineral and microbial amendments decreased the association between Cd with carbon and minerals in the macroaggregates, while they enhanced the binding of Cd and Fe oxides in the silt+clay fractions. Collectively, our findings revealed that the mineral and microbial amendments promoted Cd transfer, enhancing the stability of Cd in the finer soil fractions and offering essential insights for developing agricultural management strategies to alleviate Cd contamination in paddy soils.

Composites Based on Natural Zeolites and Green Materials for the Immobilization of Toxic Elements in Contaminated Soils: A Review

Soil contamination by toxic elements is a global problem, and the remediation of contaminated soils requires complex and time-consuming technology. Conventional methods of soil remediation are often inapplicable, so an intensive search is underway for innovative and environmentally friendly ways to clean up ecosystems. The use of amendments that stabilize the toxic elements in soil by reducing their mobility and bioavailability is one of the simplest and most cost-effective ways to remediate soil. This paper provides a summary of studies related to the use of composites based on natural zeolites and green materials for the immobilization of toxic elements in contaminated soils and highlights positive examples of returning land to agricultural use. The published literature on natural zeolites and their composites has shown that combinations of zeolite with biochar, chitosan and other clay minerals have beneficial synergistic effects on toxic element immobilization and soil quality. The effects of zeolite properties, different combinations, application rates, or incubation periods on toxic elements immobilization were tested in laboratory scale or field experiments, whereas the mobility of toxic elements in soil was evaluated by chemical extractions of toxic elements transferred to the plants. This review highlights the excellent potential of natural zeolites to be used as single or combined sustainable green materials to solve environmental pollution problems related to the presence of toxic elements.

Copper and cadmium co-contamination increases the risk of nitrogen loss in red paddy soils

The microbiome plays a crucial role in soil nitrogen (N) cycling and in regulating its bioavailability. However, the functional and genomic information of microorganisms encoding N cycling in response to copper (Cu) and cadmium (Cd) contamination is largely unknown. Here, metagenomics and genome binning were used to examine microbial N cycling in Cu and Cd co-contaminated red paddy soils collected from a polluted watershed in southern China. The results showed that soil Cu and Cd concentrations induced more drastic changes in microbial N functional and taxonomic traits than soil general properties. Soil Cu and Cd co-contamination stimulated microbial nitrification, denitrification, and dissimilatory nitrate reduction processes mainly by increasing the abundance of Nitrospira (phylum Nitrospirota), while inhibiting N fixation by decreasing the abundance of Desulfobacca. These contrasting changes in microbial N cycling processes suggested a potential risk of N loss in paddy soils. A high-quality genome was identified as belonging to Nitrospirota with the highest abundance in heavily contaminated soils. This novel Nitrospirota strain possessed metabolic capacities for N transformation and metal resistance. These findings elucidate the genetic mechanisms underlying soil N bioavailability under long-term Cu and Cd contamination, which is essential for maintaining agricultural productivity and controlling heavy metal pollution.

Bioelectrochemical technologies for soil and sediment remediation: Recent advances and future perspectives

Soil and sediment serve as the ultimate repositories of pollutants, presenting a significant environmental concern on a global scale. However, there is no effective measure due to the low mobility, high resistance and high cost of contaminated soil or sediment. The bioelectrochemical systems (BESs) combine microbial and electrochemical technology to achieve efficient and rapid degradation of pollutants by enriching electroactive microbial membranes with electrodes. Specifically, BESs offer an ideal solution for in-situ remediation, eliminating the secondary pollution and high energy consumption issues associated with traditional technologies. However, in soil or sediment bioelectrochemical systems (SBESs), further summarization and improvement are required to address the influencing factors during the process of pollutant remediation, given the fragility of complex geographical and natural environments. This paper provides a comprehensive overview and analysis of the removal mechanisms of organic pollutants, heavy metals and emerging contaminants within contaminated soil or sediment, elucidating the influential factors and strategies aimed at enhancing pollutant removal processes within SBESs. The current emerging problems and limitations of microbial electrochemical remediation technology are summarized, and it is suggested that future development should focus on microorganisms, reactors and practical applications.

Pollution area identification, receptor model-oriented sources and probabilistic health hazards to prioritize control measures for heavy metal management in soil

Identifying the primary source of heavy metals (HMs) pollution and the key pollutants is crucial for safeguarding eco-health and managing risks in industrial vicinity. For this purpose, this investigation was carried out to investigate the pollution area identification with soil static environmental capacity (QI), receptor model-oriented critical sources, and Monte Carlo simulation (MCS) based probabilistic environmental and human health hazards associated with HMs in agricultural soils of Narayanganj, Bangladesh. The average concentration of Cr, Ni, Cu, Cd, Pb, Co, Zn, and Mn were 98.67, 63.41, 37.39, 1.28, 23.93, 14.48, 125.08, and 467.45 mg/kg, respectively. The geoaccumulation index identified Cd as the dominant metal, indicating heavy to extreme contamination in soils. The QI revealed that over 99% of the areas were polluted for Ni and Cd with less uncertain regions whereas Cr showed a significant portion of areas with uncertain pollution status. The positive matrix factorization (PMF) model identified three major sources: agricultural (29%), vehicular emissions (25%), and industrial (46%). The probabilistic assessment of health hazards indicated that both carcinogenic and non-carcinogenic risks for adult male, adult female, and children were deemed unacceptable. Moreover, children faced a higher health hazard compared to adults. For adult male, adult female, and children, industrial operations contributed 48.4%, 42.7%, and 71.2% of the carcinogenic risks, respectively and these risks were associated with Ni and Cr as the main pollutants of concern. The study emphasizes valuable scientific insights for environmental managers to tackle soil pollution from HMs by effectively managing anthropogenic sources. It could aid in devising strategies for environmental remediation engineering and refining industry standards.

Chemical speciation and health risk assessment of potentially toxic elements in playground soil of bell metal commercial town of Eastern India

Contaminated playground soils can expose players to harmful pollutants, increasing the risk of respiratory, skin, and gastrointestinal issues and potentially impacting long-term health and development. This study investigated the chemical forms and the human health risks associated with potentially toxic elements (PTEs) found in playground soil samples from Khagra, a historic town known for its bell metal industry, located in the Murshidabad district of eastern India. Sequential extraction techniques were employed to analyze the distribution of PTEs such as As, Cd, Co, Cu, Mn, Pb, Ni, Sn, and Zn among different fractions: exchangeable (F1), bound to carbonate phase (F2), bound to iron and manganese oxides (F3), bound to organic matter (F4), and residual (F5). The playground soil showed the highest contamination with Sn, with an IPOLL value of 3.14, indicating moderate to heavy contamination, while Cd, Cu, Mn, Pb, and Zn exhibit moderate contamination. The mean concentration of PTEs in all fractions (F1-F5) follows the order: Fe > Zn > Cu > Mn > Pb > Sn > Ni > Co > As > Cd. The maximum affinity of PTEs and their percentages are as follows: Fe (F5, 80.6%), As (F5, 55.31%), Cd (F5, 48.8), Co (F5, 64.9%), Mn (F3, 44%), Ni (F5, 53.2%), Pb (F3, 44.7%), Zn (F3, -43.19%), Sn (F3, 55%), Cu (F5 -42.18). As, Cd, Co, Cu, Fe, and Ni have a high affinity for F5, indicating geogenic source, while Mn, Pb, Sn, and Zn have a high affinity for F3, indicating anthropogenic source. Fe-Mn oxide partition was dominant for nearly all PTEs due to elevated sorption of cations onto Fe-Mn oxides at high pH. The risk assessment code for Cd, Cu, Mn, Ni, Sn, and Zn in playground soil is categorized under moderate risk, below 30%, while other elements showed no risk. Also, mobility factors were calculated for each PTEs, suggesting the degree of mobility that PTEs can easily migrate and be taken up, absorbed, or adsorbed by the human body. The mobility factor in playground soil was higher for Sn (59.89%) followed by Mn (54.24%) > Pb (52.91%) > Zn (52.01%) > Cd (39.49%) > Ni (33.20%) > As (30.39%) > Co (26.56%) > Cu (21.24%) > Fe (11.20%). Risk hazard quotients for children and adults were found to follow the order: Pb (0.263; 0.040), Cu (0.098; 0.015) > As(0.056; 0.008) > Mn (0.045; 0.009) > Zn(0.36; 0.05) > Cd(0.006; 0.001) > Ni (0.004; 0.001) > Co (0.001; 0.0). PTEs detected in the environment result from atmospheric deposition from small-scale metallurgical industries (bell metal and brass), coal and oil combustion, civil works, municipal waste incineration, and fugitive emissions from road dust. The human non-carcinogenic health risk for PTEs from ingestion and dermal contact was higher than that from inhalation. In the context of carcinogenic risk, As shows the highest health risk of 2.51E-05, followed by Cd (1.02E-09) and Co (8.14E-09). This study uniquely assesses the chemical speciation of PTEs in playground soils, revealing their geogenic and anthropogenic sources, and evaluates associated health risks. Policy intervention is vital for monitoring and remediating PTEs in playgrounds to protect children's health.

Molasses-based waste water irrigation: a friend or foe for carrot (Daucus carota L.) growth, yield and nutritional quality

Management of molasses-based wastewater generated in yeast and sugar industries is a major environmental concern due to its high chemical oxygen demand and other recalcitrant substances. Several strategies have been used to reduce the inland discharge of wastewater but the results are not satisfactory due to high operating cost. However, reuse of molasses-based wastewater irrigation in agriculture has been a major interest nowadays to reduce the freshwater consumption. Thus, it is crucial to monitor the impacts of molasses-based waste water irrigation on growth, metabolism, yield and nutritional quality of crops for safer consumer's health. In present study, carrot seeds of a local cultivar (T-29) were germinated on filter paper in Petri dishes under controlled conditions. The germinated seeds were then transplanted into pots and irrigated with three different treatments normal water (T0), diluted molasses-based wastewater (T1), and untreated molasses-based wastewater (T2), in six replicates. Results revealed that carrot irrigated with untreated molasses-based waste water had exhibited significant reductions in growth, yield, physiology, metabolism, and nutritional contents. Additionally, accumulation of Cd and Pb contents in carrot roots irrigated with untreated molasses-based waste water exceed the permissible limits suggested by WHO and their consumption may cause health risks. While, diluted molasses-based waste water irrigation positively enhanced the growth, yield of carrot plants without affecting the nutritional quality. This strategy is cost effective, appeared as most appropriate alternative mean to reduce the freshwater consumption in water deficit regions of the world.

Microplastics in marine ecosystems: A comprehensive review of biological and ecological implications and its mitigation approach using nanotechnology for the sustainable environment

Microplastic contamination has rapidly become a serious environmental issue, threatening marine ecosystems and human health. This review aims to not only understand the distribution, impacts, and transfer mechanisms of microplastic contamination but also to explore potential solutions for mitigating its widespread impact. This review encompasses the categorisation, origins, and worldwide prevalence of microplastics and methodically navigates the complicated structure of microplastics. Understanding the sources of minute plastic particles infiltrating water bodies worldwide is critical for successful removal. The presence and accumulation of microplastics has far reaching negative impacts on various marine creatures, eventually extending its implications to human health. Microplastics are known to affect the metabolic activities and the survival of microbial communities, phytoplankton, zooplankton, and fauna present in marine environments. Moreover, these microplastics cause developmental abnormalities, endocrine disruption, and several metabolic disorders in humans. These microplastics accumulates in aquatic environments through trophic transfer mechanisms and biomagnification, thereby disrupting the delicate balance of these ecosystems. The review also addresses the tactics for minimising the widespread impact of microplastics by suggesting practical alternatives. These include increasing public awareness, fostering international cooperation, developing novel cleanup solutions, and encouraging the use of environment-friendly materials. In conclusion, this review examines the sources and prevalence of microplastic contamination in marine environment, its impacts on living organisms and ecosystems. It also proposes various sustainable strategies to mitigate the problem of microplastics pollution. Also, the current challenges associated with the mitigation of these pollutants have been discussed and addressing these challenges require immediate and collective action for restoring the balance in marine ecosystems.

Levels of potentially toxic and essential elements in Tocantins River sediment: health risks at Brazil's Savanna-Amazon interface

The field study aims to address identified research gaps by providing valuable information on the concentration, spatial distribution, pollution levels, and source apportionment of toxic and essential elements in sediment samples from four sampling sites (P1: Beira Rio (urban area), P2: Bananal (rural area), P3: Embiral (rural area), P4: Cidelândia (rural area) distributed along the middle Tocantins River, Brazil. Samples were collected in 2023 from river sections and analyzed using various contamination índices (geoaccumulation index, contamination factor, enrichment factor, pollution load index, sediment pollution index, potential ecological risk coefficients, and integrated risk index). Results indicated that the levels of aluminum, iron, manganese, and selenium exceeded legal standards in that year. Chromium, nickel, copper, zinc, and lead exceeded guidelines, mainly in section P1 for aluminum and section P3 for nickel and lead. Rainy months showed increased presence, indicating seasonal variability. The geoaccumulation index indicated low pollution levels, with lead and nickel notably present near urban and industrial areas. The enrichment factor highlighted elevated concentrations of lead and zinc in industrial areas. Both PLI and SPI indices raise concerns regarding Pb (P4) and Zn (P3) concentrations at specific times of the year. Overall, potential ecological risks were deemed low for most sites. Continuous monitoring and interventions are crucial to preserve water and environmental quality in the region.

Anaerobic treatment of groundwater co-contaminated by toluene and copper in a single chamber bioelectrochemical system

Addressing the simultaneous removal of multiple coexisting groundwater contaminants poses a significant challenge, primarily because of their different physicochemical properties. Indeed, different chemical compounds may necessitate establishing distinct, and sometimes conflicting, (bio)degradation and/or removal pathways. In this work, we investigated the concomitant anaerobic treatment of toluene and copper in a single-chamber bioelectrochemical cell with a potential difference of 1 V applied between the anode and the cathode. As a result, the electric current generated by the bioelectrocatalytic oxidation of toluene at the anode caused the abiotic reduction and precipitation of copper at the cathode, until the complete removal of both contaminants was achieved. Open circuit potential (OCP) experiments confirmed that the removal of copper and toluene was primarily associated with polarization. Analogously, abiotic experiments, at an applied potential of 1 V, confirmed that neither toluene was oxidized nor copper was reduced in the absence of microbial activity. At the end of each experiment, both electrodes were characterized by means of a comprehensive suite of chemical and microbiological analyses, evidencing a highly selected microbial community competent in the biodegradation of toluene in the anodic biofilm, and a uniform electrodeposition of spherical Cu2O nanoparticles over the cathode surface.

A systematic review of innovations in tannery solid waste treatment: A viable solution for the circular economy

Amidst growing global demand for leather goods, the efficient conversion of rawhide and skins into durable leather is crucial, yet approximately 80 % of these materials become solid and liquid waste during tannery operations. Improper management of tannery solid waste poses significant environmental risks, contaminating soil, groundwater, and surface water. This review explores thermochemical, biological, and phytoremediation methods for treating tannery solid waste, emphasizing their role in resource recovery and environmental sustainability. Thermochemical techniques like pyrolysis and gasification convert tannery solid waste into biochar, bio-oil, and syngas, which serve as soil amendments, renewable energy sources, or industrial feedstocks. Biological methods such as composting and anaerobic digestion decompose organic tannery solid waste components into nutrient-rich compost and biogas. Phytoremediation uses plants to remediate contaminants, including heavy metals, from tannery solid waste. These methods mitigate environmental pollution and support the leather industry's transition to sustainable practices, crucial for compliance with global regulations. Moreover, the review offers insights into current efforts and perspectives aimed at achieving a zero-waste policy, emphasizing the importance of a circular economy to alleviate the environmental burden associated with tannery operations and ensure their continued sustainability. Finally, a detailed discussion on the current challenges in terms of technology accessibility and economic feasibility was also discussed.

Effects of fluid composition in fluid injection experiments in porous media

Experiments on fluid flow in porous media, using fluids loaded with solids of various grain sizes, have been conducted in a modified Hele-Shaw setup. This setup utilised weakly cemented porous media with specific hydraulic and mechanical properties. Fluid injection in coarse granular media with clean or low-concentration fine particles, results in infiltration only, with pressure close to the material tensile strength, while injection in finer granular material causes damage alongside infiltration, with the fluid pressure still close to the material tensile strength. When larger particle sizes or higher particle concentrations are used in the mixture, the fluid travels further within the porous medium, primarily influenced by the grain size of the granular medium. In the latter case, the Darcy flow equation with an effective permeability term can be employed to determine the pressure differential. For the largest particle sizes included in the fluid, the equation is still applicable, but the effective permeability requires adjustment for particle size within the fluid rather than the granular medium. This is crucial when the injection point is locally clogged. The experiments show that fracturing conditions are controlled by different mechanisms. Dimensional and statistical analysis was used to classify the injection pressures to regimes predicted by fracturing theory or by Darcy law with modified effective permeabilities. The findings show that both the material properties and fluid composition are important designing parameters.

Advanced applications of hydroxyapatite nanocomposite materials for heavy metals and organic pollutants removal by adsorption and photocatalytic degradation: A review

This comprehensive review delves into the forefront of scientific exploration, focusing on hydroxyapatite-based nanocomposites (HANCs) and their transformative role in the adsorption of heavy metals (HMs) and organic pollutants (OPs). Nanoscale properties, including high surface area and porous structure, contribute to the enhanced adsorption capabilities of HANCs. The nanocomposites' reactive sites facilitate efficient contaminant interactions, resulting in improved kinetics and capacities. HANCs exhibit selective adsorption properties, showcasing the ability to discriminate between different contaminants. The eco-friendly synthesis methods and potential for recyclability position the HANCs as environmentally friendly solutions for adsorption processes. The review acknowledges the dynamic nature of the field, which is characterized by continuous innovation and a robust focus on ongoing research endeavors. The paper highlights the HANCs' selective adsorption capabilities of various HMs and OPs through various interactions, including hydrogen and electrostatic bonding. These materials are also used for aquatic pollutants' photocatalytic degradation, where reactive hydroxyl radicals are generated to oxidize organic pollutants quickly. Future perspectives explore novel compositions, fabrication methods, and applications, driving the evolution of HANCs for improved adsorption performance. This review provides a comprehensive synthesis of the state-of-the-art HANCs, offering insights into their diverse applications, sustainability aspects, and pivotal role in advancing adsorption technologies for HMs and OPs.

Innovative remediation strategies for persistent organic pollutants in soil and water: A comprehensive review

Persistent organic pollutants (POPs) provide a serious threat to human health and the environment in soil and water ecosystems. This thorough analysis explores creative remediation techniques meant to address POP pollution. Persistent organic pollutants are harmful substances that may withstand natural degradation processes and remain in the environment for long periods of time. Examples of these pollutants include dioxins, insecticides, and polychlorinated biphenyls (PCBs). Because of their extensive existence, cutting-edge and environmentally friendly eradication strategies must be investigated. The most recent advancements in POP clean-up technology for soil and water are evaluated critically in this article. It encompasses a wide range of techniques, such as nanotechnology, phytoremediation, enhanced oxidation processes, and bioremediation. The effectiveness, cost-effectiveness, and environmental sustainability of each method are assessed. Case studies from different parts of the world show the difficulties and effective uses of these novel techniques. The study also addresses new developments in POP regulation and monitoring, highlighting the need of all-encompassing approaches that include risk assessment and management. In order to combat POP pollution, the integration of diverse remediation strategies, hybrid approaches, and the function of natural attenuation are also examined. Researchers, legislators, and environmental professionals tackling the urgent problem of persistent organic pollutants (POPs) in soil and water should benefit greatly from this study, which offers a complete overview of the many approaches available for remediating POPs in soil and water.

Bioremediation of Pb contaminated water using a novel Bacillus sp. strain MHSD_36 isolated from Solanum nigrum

The Pb bioremediation mechanism of a multi-metal resistant endophytic bacteria Bacillus sp. strain MHSD_36, isolated from Solanum nigrum, was characterised. The strain tested positive for the presence of plant growth promoters such as indoleacetic acid, 1-aminocyclopropane-1-carboxylate deaminase, siderophores, and phosphate solubilization. The experimental data illustrated that exopolysaccharides and cell hydrophobicity played a role in Pb uptake. The data further showed that the cell wall biosorbed a significant amount (71%) of the total Pb (equivalent to 4 mg/L) removed from contaminated water, compared to the cell membrane (11%). As much as 11% of the Pb was recovered from the cytoplasmic fraction, demonstrating the ability of the strain to control the influx of toxic heavy metals into the cell and minimize their negative impacts. Pb biosorption was significantly influenced by the pH and the initial concentration of the toxic ions. Furthermore, the presence of siderophores and biosurfactants, when the strain was growing under Pb stress, was detected through liquid chromatography mass spectrometry. The strain demonstrated a multi-component based Pb biosorption mechanism and thus, has a great potential for application in heavy metal bioremediation.

Assessment of potentially toxic and mineral elements in paddy soils and their uptake by rice (Oryza sativa L.) with associated health hazards in district Malakand, Pakistan

Rice, a primary food source in many countries of the world accumulate potentially harmful elements which pose a significant health hazard to consumers. The current study aimed to evaluate potentially toxic and mineral elements in both paddy soils and rice grains associated with allied health risks in Malakand, Pakistan. Rice plants with intact root soil were randomly collected from paddy fields and analyzed for mineral and potentially toxic elements (PTEs) through inductively coupled plasma optical emission spectrometry (ICP‒OES). Through deterministic and probabilistic risk assessment models, the daily intake of PTEs with allied health risks from consumption of rice were estimated for children and adults. The results of soil pH (< 8.5) and electrical conductivity (EC > 400 μs/cm), indicated slightly saline nature. The mean phosphorus concentration of 291.50 (mg/kg) in soil samples exceeded FAO/WHO permissible limits. The normalized variation matrix of soil pH with respect to Ni (0.05), Ca (0.05), EC (0.08), and Mg (0.09), indicated significant influence of pH on PTEs mobility. In rice grains, the mean concentrations (mg/kg) of Mg (463.81), Al (70.40), As (1.23), Cr (12.53), Cu (36.07), Fe (144.32), Mn (13.89), and Ni (1.60) exceeded FAO/WHO safety limits. The transfer factor >1 for K, Cu, P and Zn indicated bioavailability and transfer of these elements from soil to rice grains. Monte Carlo simulations of hazard index >1 for Cr, Zn, As, and Cu with certainties of 89.93% and 90.17%, indicated significant noncarcinogenic risks for children and adults from rice consumption. The total carcinogenic risk (TCR) for adults and children exceeded the USEPA acceptable limits of 1×10-6 to 1×10-4, respectively. The sensitivity analysis showed that the ingestion rate was a key risk factor. Arsenic (As) primarily influenced total cancer risk (TCR) in children, while chromium (Cr) significantly impacted adults. Deterministic cancer risk values slightly exceeded probabilistic values due to inherent uncertainties in deterministic analysis. Rice consumption poses health risks, mainly from exposure to Cr, Ni and As in the investigated area.

Groundwater chlorinated solvent plumes remediation from the past to the future: a scientometric and visualization analysis

Contamination of groundwater with chlorinated hydrocarbons has serious adverse effects on human health. As research efforts in this area have expanded, a large body of literature has accumulated. However, traditional review writing suffers from limitations regarding efficiency, quantity, and timeliness, making it difficult to achieve a comprehensive and up-to-date understanding of developments in the field. There is a critical need for new tools to address emerging research challenges. This study evaluated 1619 publications related to this field using VOSviewer and CiteSpace visual tools. An extensive quantitative analysis and global overview of current research hotspots, as well as potential future research directions, were performed by reviewing publications from 2000 to 2022. Over the last 22 years, the USA has produced the most articles, making it the central country in the international collaboration network, with active cooperation with the other 7 most productive countries. Additionally, institutions have played a positive role in promoting the publication of science and technology research. In analyzing the distribution of institutions, it was found that the University of Waterloo conducted the majority of research in this field. This paper also identified the most productive journals, Environmental Science & Technology and Applied and Environmental Microbiology, which published 11,988 and 3253 scientific articles over the past 22 years, respectively. The main technologies are bioremediation and chemical reduction, which have garnered growing attention in academic publishing. Our findings offer a useful resource and a worldwide perspective for scientists engaged in this field, highlighting both the challenges and the possibilities associated with addressing groundwater chlorinated solvent plumes remediation.

Effect of pumping-induced soil settlement on the migration and transformation of aniline

This study selected a contamination site associated with pesticide production to investigate the impact of soil settlement induced by pumping on the migration and transformation of the principal pollutant, aniline. The TMVOC model was enhanced by incorporating the settlement effect and validated through a soil-column experiment, which examined aniline distribution, phase transformation, and remediation efficiency under soil settlement. The results indicate that the optimized TMVOC model can accurately simulate the impact of pumping-induced soil settlement on aniline removal. The longitudinal migration of aniline was reduced, with the area of high concentrations drawing nearer to the surface. Furthermore, soil settlement negatively affected the removal of aniline in the Non-Aqueous Phase Liquid (NAPL) phase, resulting in a 10.59 % decline in the removal rate. In contrast, soil settlement positively influenced aniline removal in the gas and aqueous phases, increasing the removal rate by 12.55 % and 5.04 %, respectively, with the gas phase showing the most significant increase. Soil porosity decreased due to soil settlement, leading to a change in the proportion of each phase, with NAPL increasing after remediation. Additionally, soil settlement exhibited hysteresis, as evidenced by a noticeable decrease in the removal rate in the 10th month of the remediation process, and the final mass removal rate was reduced by 5.93 %.

Utilizing machine learning for reactive material selection and width design in permeable reactive barrier (PRB)

Permeable reactive barrier (PRB) is an important groundwater treatment technology. However, selecting the optimal reactive material and estimating the width remain critical and challenging problems in PRB design. Machine learning (ML) has advantages in predicting evolution and tracing contaminants in temporal and spatial distribution. In this study, ML was developed to design PRB, and its feasibility was validated through experiments and a case study. ML algorithm showed a good prediction about the Freundlich equilibrium parameter (R2 0.94 for KF, R2 0.96 for n). After SHapley Additive exPlanation (SHAP) analysis, redefining the range of the significant impact factors (initial concentration and pH) can further improve the prediction accuracy (R2 0.99 for KF, R2 0.99 for n). To mitigate model bias and ensure comprehensiveness, evaluation index with expert opinions was used to determine the optimal material from candidate materials. Meanwhile, the ML algorithm was also applied to predict the width of the mass transport zone in the adsorption column. This procedure showed excellent accuracy with R2 and root-mean-square-error (RMSE) of 0.98 and 1.2, respectively. Compared with the traditional width design methodology, ML can enhance design efficiency and save experiment time. The novel approach is based on traditional design principles, and the limitations and challenges are highlighted. After further expanding the data set and optimizing the algorithm, the accuracy of ML can make up for the existing limitations and obtain wider applications.

Self-assembled B-doped flower-like graphitic carbon nitride with high specific surface area for enhanced photocatalytic performance

Graphitic carbon nitride (g-C3N4) is a promising nonmetallic photocatalyst. In this manuscript, B-doped 3D flower-like g-C3N4 mesoporous nanospheres (BMNS) were successfully prepared by self-assembly method. The doping of B element promotes the internal growth of hollow flower-like g-C3N4 without changing the surface roughness structure, resulting in a porous floc structure, which enhances the light absorption and light reflection ability, thereby improving the light utilization rate. In addition, B element provides lower band gap, which stimulates the carrier movement and increases the activity of photogenerated carriers. The photocatalytic mechanism and process of BMNS were investigated in depth by structural characterization and performance testing. BMNS-10 % shows good degradation for four different pollutants, among which the degradation effect on Rhodamine B (RhB) reaches 97 % in 30 min. The apparent rate constant of RhB degradation by BMNS-10 % is 0.125 min-1, which is 46 times faster compared to bulk g-C3N4 (BCN). And the photocatalyst also exhibits excellent H2O2 production rate under visible light. Under λ > 420 nm, the H2O2 yield of BMNS-10 % (779.9 μM) in 1 h is 15.9 times higher than that of BCN (48.98 μM). Finally, the photocatalytic mechanism is proposed from the results of free radical trapping experiments.

The impacts of climate change on groundwater quality: A review

Groundwater has been known as the second largest freshwater storage in the world, following surface water. Over the years, groundwater has already been under overwhelming pressure to satisfy human needs for artificial activities around the world. Meanwhile, the most noticeable footprint of human activities is the impact of climate change. Climate change has the potential to change the physical and chemical properties of groundwater, thereby affecting its ecological functions. This study summarizes existing research affiliated with the possible effects of a changing climate on the quality of groundwater, including changes in water availability, increased salinity and pollution from extreme weather events, and the potentiality of seawater intrusion into coastal aquifers. Previous works dealing with groundwater-induced responses to the climate system and climate impacts on groundwater quality through natural and anthropogenic processes have been reviewed. The climate-induced changes in groundwater quality including pH, dissolved oxygen level, salinity, and concentrations of organic and inorganic compounds were assessed. Some future research directions are proposed, including exploring the potential changes in the occurrences and fate of micropollutants in groundwater, examining the relationship between the increase of microcystin in groundwater and climate change, studying the changes in the stability of metals and metal complexation, and completing studies across different regional climate regions.

Efficient and fast remediation of soil contaminated by per- and polyfluoroalkyl substances (PFAS) by high-frequency heating

This study presents a novel thermal technology (high-frequency heating, HFH) for the decontamination of soil containing per- and polyfluoroalkyl substances (PFAS) and aqueous film-forming foams (AFFFs). Ultra-fast degradation of short-chain PFAS, long-chain homologs, precursors, legacy PFAS, emerging PFAS was achieved in a matter of minutes. The concentrations of PFAS and the soil type had a negligible impact on degradation efficiency, possibly due to the ultra-fast degradation rate overwhelming potential differences. Under the current HFH experiment setup, we achieved near-complete degradation (e.g., >99.9%) after 1 min for perfluoroalkyl carboxylic acids and perfluoroalkyl ether carboxylic acids and 2 min for perfluoroalkanesulfonic acids. Polyfluoroalkyl precursors in AFFFs were found to degrade completely within 1 min of HFH; no residual cationic, zwitterionic, anionic, or non-ionic intermediate products were detected following the treatment. The gaseous byproducts were considered. Most of gaseous organofluorine products of PFAS at low-and-moderate temperatures disappeared when temperatures reached 890 °C, which is in the temperature zone of HFH. For the first time, we demonstrated minimal loss of PFAS in water during the boiling process, indicating a low risk of PFAS entering the atmosphere with the water vapor. The findings highlight HFH its potential as a promising remediation tool for PFAS-contaminated soils.

Mitigation of the mobilization and accumulation of toxic metal(loid)s in ryegrass using sodium sulfide

Remediation of soils contaminated with toxic metal(loid)s (TMs) and mitigation of the associated ecological and human health risks are of great concern. Sodium sulfide (Na2S) can be used as an amendment for the immobilization of TMs in contaminated soils; however, the effects of Na2S on the leachability, bioavailability, and uptake of TMs in highly-contaminated soils under field conditions have not been investigated yet. This is the first field-scale research study investigating the effect of Na2S application on soils with Hg, Pb and Cu contents 70-to-7000-fold higher than background values and also polluted with As, Cd, Ni, and Zn. An ex situ remediation project including soil replacement, immobilization with Na2S, and safe landfilling was conducted at Daiziying and Anle (China) with soils contaminated with As, Cd, Cu, Hg, Ni, Pb and Zn. Notably, Na2S application significantly lowered the sulfuric-nitric acid leachable TMs below the limits defined by Chinese regulations. There was also a significant reduction in the DTPA-extractable TMs in the two studied sites up to 85.9 % for Hg, 71.4 % for Cu, 71.9 % for Pb, 48.1 % for Cd, 37.1 % for Zn, 34.3 % for Ni, and 15.7 % for As compared to the untreated controls. Moreover, Na2S treatment decreased the shoot TM contents in the last harvest to levels lower than the TM regulation limits concerning fodder crops, and decreased the TM root-to-shoot translocation, compared to the untreated control sites. We conclude that Na2S has great potential to remediate soils heavily tainted with TMs and mitigate the associated ecological and human health risks.

Method for Simulating the Anti-Damage Performance of Consolidation Soil Balls at the Roots of Seedlings during Transportation Using Consolidated Soil Columns

In the process of landscaping or afforestation in challenging terrain, in order to improve the survival rate of transplanted seedlings, it is necessary to transplant seedlings with a mother soil ball attached. During transportation, the soil ball at the root of the seedlings is very susceptible to breakage due to compression, bumps, and collisions. In order to ensure the integrity of the soil ball of the transplanted seedlings and improve the survival rate of seedlings, a method of chemically enhancing the soil surface strength was employed. Specifically, a polymer-based soil consolidating agent was used to solidify the root balls of the seedlings. To examine the abrasion resistance performance of the soil balls formed by consolidating the surface with polymer adhesive during the transportation process, we utilized a polymer-based consolidating agent to prepare test soil columns and developed a method to simulate the damage resistance performance of seedling root balls during transportation using these soil columns. The method primarily encompasses two aspects of testing: compressive strength testing of the consolidated soil columns and resistance to transportation vibration testing. The first method for testing the resistance to transportation vibration of the consolidated soil columns is a combination test that includes three sets of tests: highway truck transportation vibration testing, combined wheel vehicle transportation vibration testing, and impact testing. Although the method is cumbersome, testing is more accurate. The second method for testing the resistance to transportation vibration of the consolidated soil columns involves simultaneously testing multiple consolidated soil columns using a simulated transportation vibration test platform. The testing method is concise and efficient, and the test results are more intuitive. The combined assessment of the resistance to transportation vibration and compressive strength testing of the consolidated soil columns allows for a comprehensive evaluation of the soil columns' resistance to damage during transportation. This study mainly provides a quick and effective method for detecting the damage resistance of consolidated soil columns/balls during transportation, providing technical support for the application of polymer-based consolidation agents in the field of seedling transplantation.