Integrating Biochar, Bacteria, and Plants for Sustainable Remediation of Soils Contaminated with Organic Pollutants

Reduction of antimony bioavailability with the application of stable exogenous organic matter: a comparative study between rice straw and manure compost

Considering the widespread use of organic amendments to improve soil quality and enhance soil carbon sequestration, it is crucial to understand their impact on the bioavailability of metalloids in soils. Antimony (Sb), a priority pollutant, is particularly impacted by organic matter, yet the effects of different organic amendments-varying in stability and composition-on Sb bioavailability remain unclear. This study investigates the influence of different organic amendments, rice straw and compost, on Sb bioavailability in the rice-soil system, with rice ingestion being a major Sb exposure pathway in humans. Results show that while both amendments increased dissolved organic carbon in soil solution, their effects on Sb bioavailability differed markedly. Rice straw increased CDGT-SbIII by 13.24 %-66.63 %, whereas compost decreased CDGT-SbIII by 32.47 %-43.51 %. These differences were also reflected in Sb accumulation in rice shoots, where compost application resulted in lower Sb content. This reduction may be attributed to increased microbial genera such as Ramlibacter and Sphingomonas, which are associated with SbIII oxidation. Conversely, organic matter with low stability, prone to rapid degradation, could promote reducing soil conditions, thereby increasing SbIII concentrations. Our findings suggest that stable exogenous organic matter, such as pre-decomposed compost, is preferable for managing Sb-contaminated soils.

Higher remediation efficiency of Cd and lower CO2 emissions in phytoremediation systems with biochar application

Biochar has been considered a promising material for soil carbon sequestration. However, there are huge knowledge gaps regarding the carbon reduction effects of biochar-plant-polluted soil. Here, rice straw biochar (RB) was applied in ryegrass-cadmium (Cd)-contaminated soil to investigate the full-cycle carbon dioxide (CO2) emission and intrinsic mechanism. RB resulted in a 37.00 %-115.64 % reduction in accumulative CO2 emissions and a 31.61 %-45.80 % reduction in soil bioavailable Cd throughout the whole phytoremediation period. CO2 emission reduction triggered by RB can be attributed to the regulation of plant and rhizosphere ecological functions. RB could bolster photosynthetic carbon fixation by maintaining the stability of the structure of the chloroplasts and thylakoids, accelerating the consumption of terminal photosynthate, upregulating photosynthetic pigments, and mitigating oxidative damage. Besides, RB reduced the metabolism of readily mineralizable carbon sources while reinforcing the utilization of certain nutrient substrates. Besides, the composition of rhizosphere microbial communities was altered, especially those associated with carbon cycling (Chloroflexi, Actinobacteriota, and Acidobacteriota phyla) to orient soil microbial evolution to lower soil CO2 emission. This study aims to establish a win-win paradigm of "carbon reduction-pollution alleviation" to deepen the understanding of biochar in carbon neutrality and soil health and provide a theoretical basis for field pilot-scale studies.

Remediation strategies of biochar and microbial inoculum for PAHs-contaminated soil: Quorum sensing-mediated PAHs degradation and element cycling

The pyrolysis of straw for biochar production offers significant advantages in resource recycling and soil improvement. However, the concurrent effects of biochar on contaminant degradation and biogeochemical cycles in polycyclic aromatic hydrocarbons (PAHs)-contaminated soil remain unclear. This study aims to integrate the roles of functional microorganisms, PAHs degradation pathways, and soil element cycles to elucidate the remediation characteristics of PAHs-contaminated soil. The results demonstrated that the addition of biochar increased the removal rate of phenanthrene (PHE) of PAHs in soil by 75.7 %, and microbial inoculum enhanced this rate to 93.4 %. Both treatments simultaneously improved soil physicochemical properties. Additionally, these amendments influenced the composition of the microbial community, increasing microbial diversity as evidenced by a rise in the Chao1 index by 2.75 % and 4.50 %, and the Shannon index by 8.73 % and 7.60 %, respectively. Moreover, the addition of biochar and microbial inoculum enabled quorum sensing and key microbial species to play a significant role in PHE degradation and ecological restoration. Specifically, these amendments have altered the degradation pathways of soil PHE: biochar promoted PHE degradation via the phthalate pathway, whereas microbial inoculum favored the salicylic acid pathway. Furthermore, both amendments expedited nutrient element cycling in soils. Biochar stimulated nitrate assimilation and the degradation of labile organic carbon compounds, while microbial inoculum enhanced the biodegradation of refractory organic carbon, carbon and nitrogen fixation, and concurrently reduced greenhouse gas emissions. This study presents an innovative strategy for ecologically rehabilitating PHE-contaminated soils by integrating microbial interactions with soil element circulation.

Physiological and Agronomic Responses of Maize (Zea mays L.) to Compost and PGPR Under Different Salinity Levels

Salinity stress severely limits maize (Zea mays L.) productivity, necessitating sustainable mitigation strategies to ensure food security in affected regions. This study investigates the efficacy of compost (5 and 10 t/ha) and plant growth-promoting rhizobacteria (PGPR; Azospirillum brasilense) in enhancing maize productivity and soil health under salinity stress (ECe 3.5 and 6.3 dS/m) across three varieties (Single Cross 131, 132, and 178) in field experiments conducted in 2023 and 2024. Combined compost-10 + PGPR treatment significantly increased grain yield by up to 197% and straw yield by nearly 300% in Single Cross 178 under high salinity, surpassing single treatments. Nitrogen content in grains and straw rose by 157%, while proline, peroxidase activity, and chlorophyll content improved, indicating robust stress tolerance. Soil properties, including pH, ECe, sodium adsorption ratio, and exchangeable sodium percentage, were significantly ameliorated, with bulk density reduced and porosity increased. Soil organic matter and microbial populations (bacteria and fungi) were also enhanced. Single Cross 178 exhibited superior stress tolerance, highlighting varietal differences. These findings, supported by comparisons with the existing literature, underscore the synergistic role of compost and PGPR in improving nutrient uptake, antioxidant defenses, and soil structure. This study offers a sustainable strategy for maize cultivation in saline environments, with implications for global food security.

Mechanisms of Phenol Adsorption on Banana Leaves and Coffee Husk Biochars

In this study, biochars were produced from banana leaves (BB) and coffee husk (BC) for phenol adsorption. The biochars were characterized using Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, textural analysis, point of zero charge measurement, and determination of surface acidic and basic groups. For both biochars, a higher pyrolysis temperature led to losses of oxygenated groups as well as increases of graphitic structures and greater basic character. For biochars produced at 400 °C, phenol adsorption kinetics was best described by the pseudo-second-order model. Chemisorption involving π-π interactions was identified as the main adsorption mechanism. For biochars produced at 500 °C, a smaller pore size resulted in limited adsorption by intraparticle diffusion. The Freundlich model provided the best fit to the isotherm data due to the high surface heterogeneity. Moreover, the results also suggested the formation of multilayers or pore filling as adsorption mechanisms for the obtained biochars. The maximum adsorption capacity values (q e) were 13.8 and 21.2 mg g-1 for phenol adsorption on BB400 and BB500, and 17.3 and 19.1 mg g-1 for BC400 and BC500, respectively. The results showed that the agroindustrial residues are suitable for phenol adsorption in aqueous solutions.

Machine Learning-Enhanced Prediction for Soil-to-Air VOC Emission and Environmental Impact Pertaining Contaminated Fractured Aquifers

How to scientifically and efficiently quantify the impact and hazards of volatile organic compounds (VOCs) pollution and volatilization from complex groundwater systems on surface air environments is a critical environmental issue. This paper employed an integrated modeling approach, incorporating numerical simulations, statistical analyses, and machine learning to address this issue. We comprehensively accounted for the different driving mechanisms, along with the various migration and transformation processes of groundwater VOCs. This investigation identified 11 key factors influencing surface pollutant flux. The data-enhanced statistical surrogate models and sampling-fusion-based support vector machine (SVM) surrogate models were established for appropriate generic modeling applications in which the high computation burden and difficulty could be avoided of the complicated numerical modeling. Those models would enable accurate prediction of surface fluxes and reliable classification of environmental risks. Notably, the pollutant fluxes through the soil-air interface over a short period could be sufficient to cause slow-airflow space air concentrations to exceed acceptable levels. Particularly, the established generic statistical surrogate models and SVM surrogate models have significant implications in efficiently and rapidly assessing the VOCs surface fluxes and environmental risk with meaningful quantified uncertainties for specific site conditions.

Influence mechanisms underlying the degradation of petroleum hydrocarbons in response to various nitrogen dosages supplementation through metatranscriptomics analysis

Exogenous nitrogen supplementation for the bioremediation of petroleum-contaminated soils is a widely adopted and effective environmentally friendly strategy. However, the mechanism by which varying nitrogen dosages affect hydrocarbon degradation pathways remains unclear. This study conducted bioremediation on soil with a total petroleum hydrocarbon (TPH) content of 17,090 mg/kg over 210 days. The results indicated that low-dosage nitrogen supplementation (136 mg N/kg, LN) achieved a 24.8 % TPH removal, significantly outperforming high-dosage nitrogen treatment (1360 mg N/kg, HN), which achieved only 12.8 % TPH removal. The LN treatment demonstrated nitrogen availability efficiency (NAVE) and nitrogen partial factor availability (NPFA) values of 6.03 mg/mg and 31.11 mg/mg, respectively, compared to -0.90 mg/mg and 1.60 mg/mg for the HN treatment. The metatranscriptomic data were employed to investigate differential gene expression across individual samples and for GO and KEGG functional annotation. The annotation results revealed a significant increase in the number of differentially expressed genes (DEGs) associated with each functional category as the nitrogen dose increased. Notably, the LN treatment upregulated genes such as bbsE, bbsF, golA, and badH, which are crucial for encoding aromatic hydrocarbon degradation. Additionally, pyruvate metabolism genes including aceE, acdA, and atoB were enriched due to the LN treatment. In contrast, the HN treatment promoted soil nitrogen metabolism through enhanced expression of nitrogen cycling-related genes such as narK, narG, narH, nirA, and nirK, contributing to competitive interactions with carbon metabolism and impeding hydrocarbon degradation by soil microorganisms. These results suggest that the regulation of nitrogen application is crucial for enhancing hydrocarbon biodegradation efficiency in petroleum-contaminated soils.

Promoting the remediation of contaminated soils using biochar in combination with bioaugmentation and phytoremediation techniques

Pollutants in soils are detrimental to ecosystems and agricultural production and may also be a pressing threat to human health. In this context, biochar could be used as part of nature-based solutions to remediate polluted areas. In this work, a series of innovative biochar-based strategies were tested in a soil contaminated by hydrocarbons C > 12 and copper (Cu) to investigate their effectiveness in soil decontamination and revegetation potential. Specifically, biochar was applied to soil alone (SB) or combined with bioaugmentation (SBB) and/or phytoremediation (SBP and SBBP) techniques. Overall results showed that after nine months (T9) biochar added to soil increased hydrocarbon degradation to 66.7% with respect to control soil (46%, natural attenuation). Moreover, the biochar in combination with a microbial consortium and/or plants significantly increased hydrocarbon removal by up to 90%. Concurrently, the fraction of Cu associated with organic matter, characterized by low bioavailability, increased significantly (1.4-2-fold) when biochar was applied. Soil microbial abundance increased over time in all conditions, reaching highest values in SBB and SBBP. This was associated with the higher levels of available phosphorus in the soil. The consortium's presence enhanced plant growth compared to SB. On the contrary, plants grown on contaminated soil alone were not able to survive until the end of the experiment. Overall, the results of this work make a significant contribution to the understanding of the interaction of biochar with contaminants, plants and microorganisms, providing a useful tool for future brownfield revegetation/remediation programs.

Effective microbial formulations using sustainable carriers for the remediation of plastic-affected soils

The increasing use of mulching films in intensive agriculture, together with their inefficient end-of-life disposal, has led to a significant plastic accumulation in soils, which contributes to disrupting ecosystems. The aim of this work was to determine the ability of different sustainable carriers to harbor and introduce plastic-degrading microorganisms into contaminated soils to provide a biotechnological tool that potentially enhances plastic decontamination, ameliorating the harmful effect of this type of pollutant in soil. To this end, pure cultures and co-cultures of Bacillus subtilis and Pseudomonas alloputida (specialized plastic-degrading strains) were added to three sustainable carriers (vermicompost, biochar, and calcium alginate beads) for the preparation of microbial formulations. After a storage period, the maintenance of cell viability and enzymatic activities related to the bioremediation potential of plastic materials of the inocula tested in the different microbial formulations (carrier + inoculant) were evaluated. The effectiveness of the formulations for plastic mineralization was tested by measuring CO2 emissions after two months. The results showed that biochar, followed by vermicompost, favored greater microbial survival (107 CFU g-1), while alginate formulations showed variable cell viability results, from 107 to 104 CFU g-1. Biochar also excelled in maintaining enzymatic activities related to plastic degradation, achieving the expression of 100% of the tested enzymes. Additionally, biochar-based formulations applied to soils contaminated with LLDPE plastic showed the highest mineralization rates, with statistically significant differences compared to the plastic-free control. These results lay the foundation for the development of new plastic decontamination technologies paving the way for the sustainable treatment of polluting and recalcitrant materials such as plastic.

Biochar mediated fixation of nitrogen compounds (ammonia and nitrite) in soil: a review

Biochar (BC) is a carbon-rich material created from biomass pyrolysis. It is an efficient addition for reducing ammonia inhibition due to its large specific surface area, porosity, conductivity, redox characteristics, and functional groups making it favorable for both soil and water remediation. The efficacy of biochar on the N cycle is associated with biochar properties which are mainly affected by feedstock type and pyrolysis condition. The addition of BC to soil affects nitrogen adsorption pathways. Other advantages include improved soil fertility, nutrient immobilization, and slow-release carbon storage. Biochar adsorption of ammonia reduces ammonia (NH3) and nitrate (NO3) losses during composting after manure applications and provides a method for creating slow-release fertilizers. Depending on the N source and the properties of the biochar, NH3 loss reductions vary. Besides improving soil dynamics, BC can also be used in wastewater treatment. Engineered or designer biochar is positioned as a promising material for wastewater treatment due to its enhanced properties and versatility.

Resource utilization of tea waste in biochar and other areas: Current status, challenges and future prospects

The consumption of tea, one of the most popular non-alcoholic beverages, has steadily increased, leading to a significant rise in global tea production and consequently the generation of substantial amounts of tea waste annually. China alone generates more than 5 million tons of tea waste annually, comprising trimmed stems, discarded leaves and buds, waste from the manufacturing process, and residue after brewing. Tea is rich in polyphenols, polysaccharides, amino acids, alkaloids, and other active substances. Leveraging substantial quantities of tea waste can produce cost-effective derivatives across various sectors, thereby enhancing its utilitarian value and promoting a circular economy, for "Waste to Treasure". This study aims to evaluate the potential for resourceful utilization of tea waste in diverse applications. The current state of research concerning various applications of tea waste, including its use in biochar, composting feedstock, sludge performance modifiers, disinfection and biocides, as well as animal feed is comprehensively summarized. Focusing on the preparation and application of tea-waste-derived biochar (TWB), this study identifies several limitations in current TWB production technologies, including challenges related to performance, yield, and economic viability. Combined with bibliometric analysis, machine learning methods have emerged as valuable tools for evaluating and predicting biochar performance, as well as optimizing the biochar production process. An economic assessment of TWB production costs revealed that its production cost ($434.2/ton) is lower than that of corn stover ($454.19/ton) and wheat straw ($448.01/ton), but higher than rice straw ($425.73/ton). Furthermore, the analysis highlighted pyrolysis time and heating rate as critical factors influencing production costs, offering new insights compared to prior studies. This paper summarizes the progress and challenges faced by tea wastes in the field of biochar and looks at future directions. Results will provide sustainable utilization of tea waste and assist in exploiting this abundant and cheap waste biomass in many ways.

Spent Mushroom Substrate-Derived Biochar and Its Applications in Modern Agricultural Systems: An Extensive Overview

Spent mushroom substrate (SMS), a nutrient-dense byproduct of mushroom cultivation, has emerged as a promising feedstock for biochar production, offering a sustainable solution to modern agricultural and environmental challenges. This review explores SMS properties, its conversion into biochar, and its various applications. Due to its lignocellulosic structure, high organic matter (OM), and essential nutrients, SMS is ideal for pyrolysis, a process that enhances biochar's porosity, nutrient retention, and carbon stability. These properties improve soil fertility, water retention, microbial activity, and plant growth while also contributing to climate change mitigation through carbon sequestration. SMS-derived biochar stands out for its superior benefits, including a balanced pH, a rich nutrient profile, and the ability to adsorb heavy metals, which mitigates soil and water contamination and minimizes toxic risks in the food chain. By enhancing soil structure, nutrient cycling, and moisture retention, SMS-derived biochar supports sustainable farming practices that reduce chemical fertilizer use and boost climate resilience. Beyond soil applications, SMS-derived biochar is effective in wastewater treatment, mitigating plant diseases, and improving mushroom cultivation substrates, thereby enhancing mycelial growth and productivity. Economically, it is a cost-effective alternative due to the abundant availability and inexpensive nature of SMS. Nevertheless, challenges still exist, particularly in optimizing production methods and ensuring consistency in biochar properties, influenced by variations in pyrolysis conditions and SMS types. Advances in production technology and sustainable practices are vital for scaling up SMS-derived biochar production. This paper emphasizes the transformative potential of SMS-derived biochar, advocating for its integration into circular economy frameworks and sustainable agricultural systems. Recommendations for future research and policy support are provided to maximize the ecological and economic benefits of SMS-derived biochar, fostering its widespread adoption in global agricultural and environmental strategies.

Synergistic effects of allantoin and Achyranthes japonica-biochar profoundly alleviate lead toxicity during barley growth

Lead (Pb), a toxic metal, causes severe health hazards to both humans and plants due to environmental pollution. Biochar addition has been efficiently utilized to enhance growth of plants as well as yield in the presence of Pb-induced stress. The present research introduces a novel use of biochar obtained from the weed Achyranthes japonica to enhance the growth of plants in Pb-contaminated soil. An experiment was performed with 7 treatments: Control, Pb2+ (10 mg kg-1) only, biochar (4 %) only, allantoin (4 g kg-1) only, biochar combined with Pb2+, allantoin combined with biochar, as well as a combination of allantoin and biochar with Pb2+. Lead toxicity alone markedly diminished plant growth metrics, including root and shoot length, biomass (wet and dry), chlorophyll concentration, and grain production. The application of biochar, allantoin, or their joint administration markedly enhanced the length of shoots (by 50.3 %, 29 %, and 70 %), length of roots (by 69 %, 50 %, and 69 %), and fresh biomass of shoots (by 5 %, 29 %, and 5 %), respectively. This enhancement is ascribed to improved soil characteristics and more efficient absorption of nutrients. The application of biochar, allantoin and their combination improved the tolerance against Pb2+ by increasing the total chlorophyll level by 12 %, 16 %, and 17 %, respectively, vs. the control. Likewise, these amendments significantly (p < 0.05) improved the activity of antioxidant enzymes, including SOD, POD, and CAT by 49 %, 29 %, and 49 %, respectively. The resistance towards Pb2+ was enhanced by biochar, allantoin, and their combined application, with lower Pb2+ concentrations in shoots (59.9 %, 40.1 %, and 49.8 %), roots (48.2 %, 24.1 %, and 58.3 %), and grains (60.2 %, 29.7 %, and 40.1 %) compared to solely Pb-stress, respectively. In summary, converting the weed Achyranthes japonica into biochar and integrating it with allantoin provides an eco-friendly approach to control its proliferation while efficiently alleviating Pb-induced toxicity in plants.

Visualizing Hydrogen Peroxide Diffusion in Soils with Precipitation-Based Fluorescent Probe

Hydrogen peroxide (H2O2)-based advanced oxidation technology has emerged as a cost-effective and green solution for tackling soil pollution. Given the highly heterogeneous nature of soil, the effectiveness of H2O2 remediation is significantly influenced by its diffusion distance in soils. However, the dynamics of H2O2 diffusion and its effective range remain largely unexplored, primarily due to the lack of analytical methods for mapping H2O2 in soils. This study introduces a precipitation-based fluorescent probe (PFP) method for in situ, high-resolution (micrometer scale) mapping of H2O2 diffusion in soils. Using the PFP method, we visualized real-time H2O2 diffusion in various types of soils, revealing distinct diffusion patterns with rates ranging from 0.011 to >0.56 mm min-1. The observed differences in diffusion rates are associated with soil permeability. Additionally, soils exhibited a wide range of diffusion distances, from 0.22 to >11 mm in 20 min. Soil's reactivity for H2O2 decomposition, a previously overlooked factor, is critical in determining the diffusion distance of H2O2. We further demonstrate that the efficacy of H2O2 diffusion in soils is a pivotal factor in controlling pollutant degradation and soil remediation efficiency. These findings enhance our understanding of reagent diffusion processes in soil remediation, informing the optimization of more efficient soil remediation strategies.

Applying cross-scale regulations to Sedum plumbizincicola for strengthening the bioremediation of the agricultural soil that contaminated by electronic waste dismantling and revealing the underlying mechanisms by multi-omics

Electronic waste dismantling has induced the surrounding agricultural soils suffered from combined contamination of heavy metals and organic pollutants. Lower efficiency and complex mechanisms of bioremediation remain to be resolved. Here, we adopted regulations to Sedum plumbizincicola cross aboveground and belowground scales to strengthen the bioremediation efficiency. Results showed that the S. plumbizincicola intercropping with the Astragalus sinicusL. that inoculated with Rhizobium had the highest performance in reductions of Cd, PBDEs and PCBs from soils by 0.11 mg/kg, 67.93 μg/kg and 38.91 μg/kg, respectively. Rhizosphere soil metabolomics analysis demonstrated that reductions in Cd and PBDEs significantly associated with 2-Methylhippuric acid and L-Saccharopine, which were involved in phenylalanine metabolism, biosynthesis of amino acids and lysine. Metagenomics analysis revealed that these functional pathways were mediated by Frankia, Mycobacterium, Blastococcus, etc. microbial taxa, which were also significantly altered by regulations. Moreover, regulation regimes significantly affected transcription genes of S. plumbizincicola. Functional annotation revealed that cross-scale regulations significantly improved bioremediation efficiency through microorganisms and metabolites in the rhizosphere and transcription genes of S. plumbizincicola, which were illustrated to promote plant growth and tolerance to environmental stress. Our integration of multi-omics provides comprehensive and deep insights into molecular mechanisms in the cross-scale regulations of S. plumbizincicola, which would favor remediation techniques advances for the soil contaminated by electronic waste dismantling.

Bioaccessibility and health risk assessment of hydrophobic organic pollutants in soils from four typical industrial contaminated sites in China

There have been reports of potential health risks for people from hydrophobic organic pollutants, such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated hydrocarbons (PCHs), and organophosphate flame retardants (OPFRs). When a contaminated site is used for residential housing or public utility and recreation areas, the soil-bound organic pollutants might pose a threat to human health. In this study, we investigated the contamination profiles and potential risks to human health of 15 PAHs, 6 PCHs, and 12 OPFRs in soils from four contaminated sites in China. We used an in vitro method to determine the oral bioaccessibility of soil pollutants. Total PAHs were found at concentrations ranging from 26.4 ng/g to 987 ng/g. PCHs (0.27‒14.3 ng/g) and OPFRs (6.30‒310 ng/g) were detected, but at low levels compared to earlier reports. The levels of PAHs, PCHs, and OPFRs released from contaminated soils into simulated gastrointestinal fluids ranged from 1.74% to 91.0%, 2.51% to 39.6%, and 1.37% to 96.9%, respectively. Based on both spiked and unspiked samples, we found that the oral bioaccessibility of pollutants was correlated with their logKow and molecular weight, and the total organic carbon content and pH of soils. PAHs in 13 out of 38 contaminated soil samples posed potential high risks to children. When considering oral bioaccessibility, nine soils still posed potential risks, while the risks in the remaining soils became negligible. The contribution of this paper is that it corrects the health risk of soil-bound organic pollutants by detecting bioaccessibility in actual soils from different contaminated sites.

Bioenhanced remediation of dibutyl phthalate contaminated black soil by immobilized biochar microbiota

To address the contamination caused by DBP residues prevalent in black soils, this study developed a multifunctional bioremediation material (BHF@DK-P3) using humic acid and iron-modified corn stover biochar in combination with microbiota. The microbiota contained DBP-degrading bacteria (Enterobacterium sp. DNB-S2), phosphorus-solubilizing bacteria (Enterobacter sp. P1) and potassium-solubilizing bacteria (Paenibacillus sp. KT), and formed a good mutualistic symbiosis. In the biochar microenvironment, the microflora had lower DBP biotoxicity responses and more cell membrane formation. The addition of BHF@DK-P3 brought the structure of the DBP-contaminated black soil closer to the optimal three-phase ratio. The microbiota was able to perform their biological functions stably under both DBP stress and acid-base stress conditions. The stability of soil aggregates and the efficiency of N, P, K nutrients were improved, with available phosphorus increasing by 21.45%, available potassium by 12.54% and alkali-hydrolysable nitrogen by 14.74%. The relative abundance of copiotrophic bacterial taxa in the soil increased and the relative abundance of oligotrophic bacterial taxa decreased, providing a good mechanism for the conversion and utilization of soil nutrients. Biochar and microbiota jointly influenced soil carbon and nitrogen metabolism in response to DBP.

Nano-micro materials regulated biocatalytic metabolism for efficient environmental remediation: Fine engineering the mass and electron transfer in multicellular environments

The escalating energy and environmental crises have spurred significant research interest into developing efficient biological remediation technologies for sustainable contaminant and resource conversion. Integrating engineered nano-micro materials (NMMs) with these biocatalytic processes offers a promising approach to improve the microbial performance for environmental remediation. Core to such material-enhanced hybrid biocatalysis systems (MHBSs) is the rational regulation of metabolic processes with the assistance of NMMs, where a fine engineered mass and electron transfer is beneficial for the improved biocatalytic activity. However, the specific mechanisms of those NMMs-enhanced microbial metabolisms are normally overlooked. Here, we review the recent progress in MHBSs, focusing primarily on the mass/electron transfer regulation strategies for an enhanced microbial behavior. Specifically, the NMMs-regulated mass and electron transfer in extracellular, interfacial, and intracellular environment are summarized, where the patterns of diverse microbiological response are discussed thoroughly. Notably, fine modifications of cell interfaces and intracellular compartments by NMMs could even endow the biohybrids with new metabolic functions beyond their natural capabilities. Further, we also emphasize the importance of matching the various metabolic demands of biosystems with the diverse properties of NMMs to achieve efficient environmental remediation through a coordinated regulation strategy. Finally, major challenges and opportunities for the future development and practical implementation of MHBSs for environment remediation practices are given, aiming to provide future system design guidelines for attaining desirable biological behaviors.

A phytoremediation approach for the restoration of coal fly ash polluted sites: A review

Coal fly ash (CFA) is a predominant waste by-product of coal combustion which is disposed of in open ash dams that utilize large pieces of land. This waste material is classified as a hazardous substance in South Africa as well as in other countries due to its fine particles that are easily blown to the atmosphere and the unacceptable levels of heavy metals and persistent organic pollutants. Contaminants in CFA can pollute surface and ground water, agricultural sites, soil and therefore pose risks to the health of humans and the environment. More than 500 million tons of CFA is produced yearly and over 200 million tons remain unused globally. The production will continue due to high consumer energy demands, especially in countries with heavy reliance on coal for power generation. Despite a significant progress made on the application of phytoremediation approach for decontamination of polluted sites, there is very limited evidence for its potential in the rehabilitation of CFA dumps. Low organic carbon, microbial activities and availability of nutrients including nitrogen contribute to restricted plant growth in CFA, and therefore converting ash dumps to barren lands devoid of vegetation. Leguminous plant species can fix atmospheric nitrogen through symbiotic association with bacteria. Therefore, their intercropping mixture development can improve the chemistry of the substrate and facilitate nutrients availability to the companion plants. This approach can enhance the performance of phytoremediation and promote sustainable practices. The paper provides an overview of the ongoing burden of CFA disposal and discusses the ecological and economic benefits of using legumes, aromatic and bioenergy plants. We identify knowledge gaps to establishing vegetation in ash dumping sites, and provide insights to encourage continued research that will enhance the applicability of phytoremediation in restoration programs.

Rapid screening of indigenous degrading microorganisms for enhancing in-situ bioremediation of organic pollutants-contaminated soil

Organic pollutants (OPs) have caused severe environmental contaminations in the world and aroused wide public concern. Autochthonous bioaugmentation (ABA) is considered a reliable bioremediation approach for OPs contamination. However, the rapid screening of indigenous degrading strains from in-situ environments remains a primary challenge for the practical application of ABA. In this study, 3,5,6-Trichloro-2-pyridinol (TCP, an important intermediate in the synthesis of various pesticides) was selected as the target OPs, and DNA stable isotope probing (DNA-SIP) combined with high-throughput sequencing was employed to explore the rapid screening of indigenous degrading microorganisms. The results of DNA-SIP revealed a significant enrichment of OTU557 (Cupriavidus sp.) in the 13C-TCP-labeled heavy DNA fractions, indicating that it is the key strain involved in TCP metabolism. Subsequently, an indigenous TCP degrader, Cupriavidus sp. JL-1, was rapidly isolated from native soil based on the analysis of the metabolic substrate spectrum of Cupriavidus sp. Furthermore, ABA of strain JL-1 demonstrated higher remediation efficacy and stable survival compared to the exogenous TCP-degrading strain Cupriavidus sp. P2 in in-situ TCP-contaminated soil. This study presents a successful case for the rapid acquisition of indigenous TCP-degrading microorganisms to support ABA as a promising strategy for the in-situ bioremediation of TCP-contaminated soil.

Does the Incorporation of Biochar into Biodegradable Mulch Films Provide Agricultural Soil Benefits?

The pollution caused by plastic mulch film in agriculture has garnered significant attention. To safeguard the ecosystem from the detrimental effects of plastic pollution, it is imperative to investigate the use of biodegradable materials for manufacturing agricultural plastic film. Biochar has emerged as a feasible substance for the production of biodegradable mulch film (BDM), providing significant agricultural soil benefits. Although biochar has been widely applied in BDM manufacturing, the effect of biochar-filled plastic mulch film on soil carbon stock after its degradation has not been well documented. This study provides an overview of the current stage of biochar incorporated with BDM and summarizes its possible pathway on soil carbon stock contribution. The application of biochar-incorporated BDM can lead to substantial changes in soil microbial diversity, thereby influencing the emissions of greenhouse gases. These alterations may ultimately yield unforeseen repercussions on the carbon cycles. However, in light of the current knowledge vacuum and potential challenges, additional study is necessary to ascertain if biochar-incorporated BDM can effectively mitigate the issues of residual mulch film and microplastic contamination in agricultural land. Significant progress remains necessary before BDM may fully supplant traditional agricultural mulch film in agricultural production.

Bioaccumulation mechanisms of perfluoroalkyl substances (PFASs) in aquatic environments: Theoretical and experimental insights

Per- and polyfluoroalkyl substances (PFASs) are persistent, bioaccumulative contaminants found in water resources at levels hazardous to human health. However, the PFAS bioaccumulation mechanism remains poorly understood. In this study, we incorporated density functional theory (DFT), molecular dynamics (MD), and experiments to analyze the partitioning pathways and to establish the structure-bioaccumulation relationship. DFT- and MD-calculated environmental fate parameters, comprising LogPO,W, LogPA,W, and diffusion coefficients, coincide with experiments at various ranges of PFAS molecules, with a correction coefficient (R²) of 0.783. MD simulations revealed that medium or long-chain-length PFASs spontaneously aggregate into submicelles in aquatic environments, enhancing their bioaccumulation effect. The short-chain PFASs show weak aggregation, but they also permeate into biological membranes. Particularly, it was discovered that aggregating PFASs "dissolve" into the lipid membrane matrix, owing significantly to van der Waals interactions rather than electrostatic effects. Thermodynamic analysis suggests that PFAS translocation involves spatial flips along the free energy surface. Short-chain PFASs exhibit low steric hindrance, contributing to bioaccumulation-a factor previously neglected in research. PFAS bioaccumulation depends on chain length, as further confirmed by intracellular reactive oxygen species formation and live/dead quantification in HepG2 cells. These insights advance our understanding of PFAS bioaccumulation mechanisms and highlight critical factors influencing their environmental and biological behavior.

Toxicity evaluation and degradation of cypermethrin-contaminated soil using biochar and Bacillus cereus amendments

Cypermethrin (Cyp), a persistent synthetic pyrethroid insecticide widely used for insect control. The persistence of Cyp creates toxicity to both humans and the environment This study investigates biochar and Bacillus cereus distinct and collective effects on Cyp -contaminated soil during a 90-day incubation. This study also investigates the effects of different concentrations of Cyp (50, 100, ,500 to 1000 mg kg-1) on soil physicochemical and biological activities during a 90-day incubation period. Microbial biomass carbon and soil respiration rates decreased significantly across all cypermethrin concentrations, with the most substantial reductions observed at 1000 mg kg-1. However noticeable variations in soil enzymes and MBC over time during the entire incubation period. On 1st day, the GMean Enz and MBC rate for Cyp treatments (50, 100, ,500 to 1000 mg kg-1) ranged from 0.98 to 0.63, and 9.06, to 5.03, respectively. Under Cyp pollution, microbial biomass carbon exhibited significant decreases, with the highest inhibition (86.2%) at 1000 mg kg-1 on 1st day of incubation. Soil respiration rates dropped 77%, at 1000 mg kg-1, and Integrated biomarker response (IBR) values peaked on day 30, indicating environmental stress. Biochar and Bacillus cereus effectively facilitated the degradation of Cyp, achieving approximately 85% degradation within the first 45 days of the experiment. The combined application of biochar and Bacillus cereus increased soil pH to a neutral level from 5.9, to 7.1, reduced electrical conductivity from 1.41 µS cm- 1 to 1.20 µS cm-1, and elevated cation exchange capacity from 1.54 ± 0.04 to 6.18 C mol kg-1, while also improving organic carbon content to 3.135%. However, the dehydrogenase activity was decresed upto 47% in the combined application and all other enzymes including urasese catlayse and phostasese enzymes with Gmean enzymeatic activities were significantly improved. These findings suggest biochar and bacterial interaction for soil management to enhance soil resilience against pesticide stress.

A framework and generic models for quantifying surface environmental impact of VOCs emissions from the complex fractured rocks

To analyze the surface cumulative mass of VOCs from residual sources in dual-media fractured rocks and assess environmental health risks, complex 3D numerical models were constructed. These models comprehensively considered fracture-rock interactions, density-driven effects, and surface pressure fluctuations. The investigation identified the key control factors affecting surface cumulative mass, including the fracture aperture, pollutant source location, fracture density, and so on. Additionally, a regression-based general surrogate model was established using the obtained representative dataset. According to U.S. EPA's Respiratory Inhalation Reference Concentrations, the cumulative mass of CH2ClCHCl2 in one day for one-third of the model exceeds the concentration limit. Benzene and TCE concentrations reached 29 and 740 times the reference limits, significantly impacting air quality and health. Surrogate model analysis showed that in the worst-case scenario, 1 min's surface cumulative mass could cause Benzene concentrations to exceed the limit by 57 times. The implications of the study lies in reminding us that even after groundwater remediation in the saturated zone, residual VOCs in the capillary zones can still significantly impact surface environmental health risks. This investigation also presents an effective framework that integrates complex, time-consuming numerical modeling with simple, efficient statistical modeling to predict concerned variables and their uncertainties. This study provides a reference basis for the control of environmental pollution pertaining to VOCs volatilization from buried capillary zones at specific depths.

Emerging hazardous chemicals and biological pollutants in Canadian aquatic systems and remediation approaches: A comprehensive status report

Emerging contaminants can be natural or synthetic materials, as well as materials of a chemical, or biological origin; these materials are typically not controlled or monitored in the environment. Canada is home to nearly 7 % of the world's renewable water supply and a wide range of different kinds of water systems, including the Great Lake, rivers, canals, gulfs, and estuaries. Although the majority of these pollutants are present in trace amounts (μg/L - ng/L concentrations), several studies have reported their detrimental impact on both human health and the biota. In Canadian aquatic environments, concentrations of pharmaceuticals (as high as 115 μg/L), pesticides (as high as 1.95 μg/L), bioavailable heavy metals like dissolved mercury (as high as 135 ng/L), and hydrocarbon/crude oil spills (as high as 4.5 million liters) have been documented. Biological threats such as genetic materials of the contagious SARS-CoV-2 virus have been reported in the provinces of Québec, Ontario, Saskatchewan and Manitoba provinces, as well as in the Nunavut territory, with a need for more holistic research. These toxins and emerging pollutants are associated with nefarious short and long-term health effects, with the potential for bioaccumulation in the environment. Hence, this Canadian-focused report provides the footprints for water and environmental sustainability, in light of this emerging threat to the environment and society. Several remediation pathways/tools that have been explored by Canadian researchers, existing challenges and prospects are also discussed. The review concludes with preventive measures and strategies for managing the inventory of emerging contaminants in the environment.

Evaluation of the immobilized enzymes function in soil remediation following polycyclic aromatic hydrocarbon contamination

The bioremediation of polycyclic aromatic hydrocarbon (PAHs) from soil utilizing microorganisms, enzymes, microbial consortiums, strains, etc. has attracted a lot of interest due to the environmentally friendly, and cost-effective features. Enzymes can efficiently break down PAHs in soil by hydroxylating the benzene ring, breaking the C-C bond, and catalyze the hydroxylation of a variety of benzene ring compounds via single-electron transfer oxidation. However, the practical application is limited by its instability and ease to loss function under harsh environmental conditions such as pH, temperature, and edaphic stress etc. Therefore, this paper focused on the techniques used to immobilize enzymes and remediate PAHs in soil. Moreover, previous research has not adequately covered this topic, despite the employment of several immobilized enzymes in aqueous solution cultures to remediate other types of organic pollutants. Bibliometric analysis further highlighted the research trends from 2000 to 2023 on this field of growing interest and identified important challenges regarding enzyme stability and interaction with soil matrices. The findings indicated that immobilized enzymes may catalyzed PAHs via oxidation of OH groups in benzene rings, and generate benzyl radicals (i.e., •OH and •O2) that undergo further reaction and release water. As a result, the intermediate products of PAHs further catalyze by enzyme and enzyme induced microbes producing carbon dioxide and water. Meanwhile efficiency, activity, lifetime, resilience, and sustainability of immobilized enzyme need to be further improved for the large-scale and field-scale clean-up of PAHs polluted soils. This could be possible by integrating enzyme-based with microbial and plant-based remediation strategies. It can be coupled with another line of research focused on using a new set of support materials that can be derived from natural resources.

The interaction between biochar and earthworms: Revealing the potential ecological risks of biochar application and the feasibility of their co-application

Biochar's interaction with soil-dwelling organisms, particularly earthworms, is crucial in ensuring the effective and secure utilization of biochar in the soil. This review introduces the application of biochar in soil, summarizes how earthworms respond to biochar-amended soil and the underlying factors that can influence their response, discusses the synergistic and antagonistic impacts of earthworm activity on the efficacy of biochar, and considers the feasibility of applying them together. A review of existing research has identified uncertainty in the effect of biochar exposure on earthworms, with biochar derived from animal wastes, produced at higher pyrolysis temperatures, and used at higher doses of biochar having more negative effects on earthworms. Habitat modification, toxicity release, particle effects, and contaminant immobilization are underlying factors in how biochar affects earthworm indicators. While biochar in contaminated soils may alleviate the stress of pollutants on earthworms by decreasing their bioaccumulation, this remedial effect is not always effective. Additionally, earthworm bioturbation can enhance the migration, fragmentation, and oxidation of biochar, while also stimulating extracellular enzymes that convert biochar into 'vermichar'. Earthworms and biochar can synergize well to improve soil fertility and remediate soil organic pollution, yet exhibit contrasting roles in soil C sequestration and immobilizing heavy metals in soil. These findings highlight both the advantages and risks of their co-application. Therefore, when considering the use of biochar alone or with earthworms, it is crucial to thoroughly assess its potential ecotoxicity on earthworms and other soil organisms, as well as the influence of bioturbation, such as that caused by earthworms, on the effectiveness of biochar.

Enhancing the efficiency of phytoremediation using water hyacinth (Eichhornia crassipes) for 2,4-dichlorophenoxyacetic acid removal with modified biochar as an assisted agent

This study explores an innovative integrated system for removing the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) from aquatic environments, utilizing a combination by modified biochar derived from waste biomass of palm kernel shells (PKS-BM) and water hyacinth (Eichhornia crassipes). The characterization of the biochar revealed significant surface functional groups, a substantial surface area, and a mesoporous structure conducive to adsorption application. Biochar-assisted phytoremediation demonstrated markedly higher removal efficiencies of 2,4-D as compared to phytoremediation alone, achieving up to 98.7%, 96.9%, and 90.3% removal efficiency for 2,4-D concentrations of 50 mg/L, 100 mg/L, and 150 mg/L, respectively. Additionally, the presence of biochar significantly enhanced the morphological growth of Eichhornia crassipes, particularly under higher concentrations of 2,4-D, by mitigating toxic effects and supporting healthier plant development. These findings suggest that integrating biochar into phytoremediation system offers a promising, sustainable approach for effectively removing herbicides from contaminated water bodies while also promoting plant health and growth.

Biochar influences phytoremediation of heavy metals in contaminated soils: an overview and perspectives

Heavy metals (HMs) contamination has gained much attention due to its high degree of toxicity for living organisms. Therefore, different techniques are underway to eradicate HMs from the environment. Among the biological techniques, phytoremediation is a suitable method, but owing to the slow rate and chance of HMs penetration into the food chain, alternative techniques are needed to reduce their phytotoxicity, and biochar is one of them. Due to the diverse characteristics, biochar immobilizes HMs in the soil by improving soil pH, ion exchange, electrostatic interactions, complexation, precipitation, surface adsorption, and microbial activation. Thereby, amendment of biochar in the HMs-contaminated soils reduces HMs toxicity to plants and limits their penetration into the food chain. In contrast, some biochars have also been studied to induce metal availability in soils and subsequently its uptake by plants. This dual role of biochar depends on the feedstock of biochar, incineration temperature, and the rate of application. Moreover, biochar treatments enhance plant growth under HMs stress by improving nutrient availability, water retention capacity, scavenging of reactive oxygen species, and photosynthetic efficiency. Owing to the beneficial characteristics of biochar in HMs-contaminated sites, the number of publications has tremendously increased. Additionally, the plant species and the types of HMs that have been tested frequently under biochar treatments in these articles have been studied. Overall, the current study would help in understanding the mechanisms of how biochar influences phytoremediation of HMs and improves plant growth in HMs-polluted soils and the current scenario of the available literature.

Enhanced phytoremediation of vanadium using coffee grounds and fast-growing plants: Integrating machine learning for predictive modeling

Vanadium (V) contamination posed a significant environmental challenge, while phytoremediation offered a sustainable solution. Phytoremediation performance was often limited by the slow growth cycles of traditional plants. A novel approach to enhancing V phytoremediation by integrating coffee grounds with fast-growing plants such as barley grass, wheat grass, and ryegrass was investigated in this study. The innovative use of coffee grounds leveraged not only their nutrient-rich composition but also their ability to reduce oxidative stress in plants, thereby significantly boosting phytoremediation efficiency. Notably, ryegrass achieved 48.7% V5+ removal within 6 d with initial 20 mg/L V5+ (0.338 mg/L·d·g ryegrass). When combined with coffee grounds, V5+ removal by using wheat grass increased substantially, rising from 30.51% to 62.91%. Gradient Boosting and XGBoost models, trained with optimized parameters including a learning rate of 0.1, max depth of 3, and n_estimators of 300, were employed to predict and optimize V5+ concentrations in the phytoremediation process. These models were evaluated using mean squared error (MSE) and coefficient of determination (R2) metrics, achieving high predictive accuracy (R2 = 0.95, MSE = 1.20). Feature importance analysis further identified the initial V5+ concentration and experimental duration as the most significant factors influencing the model's predictions. The addition of coffee grounds not only mitigated the stress of heavy metals on ryegrass, leading to significant reductions in CAT (87.2%), POD (98.8%), and SOD (39.2%) activities in ryegrass roots, but also significantly altered the microbial community abundance in the plant roots. This research provided an innovative enhancement to traditional phytoremediation methods, and established a new paradigm for using machine learning to predict and optimize V5+ remediation outcomes. The effectiveness of this technology in multi-metal polluted environments warrants further investigation in the future.

The critical role of electron donating rate of pyrogenic carbon in mediating the degradation of phenols in the aquatic environment

Phenols are the widely detected contaminants in the aquatic environment. Pyrogenic carbon (PyC) can mediate phenols degradation, but the specific properties of PyC or phenols influencing this reaction remain unknown. The present study investigated the kinetic process and mechanism of removal of various phenols by different PyC in aqueous phase system. To avoid the impact of the accumulated degradation byproducts on the overall reaction, we conducted a short-term experiment, quantified adsorption and degradation, and obtained reaction rate constants using a two-compartment first-order kinetics model. The adsorption rate constants (ka) of phenols by PyC were 10-220 times higher than degradation rate constants (kd), and they were positively correlated. Interestingly, no correlation was found between kd and common PyC properties, including functional groups, electron transfer capacities, and surface properties. Phenols were primarily attacked by •OH in the adsorbed phase. But neither the instantly trapped •OH, nor the accumulated •OH could explain phenol degradation. Chemical redox titration revealed that the electron transfer parameters, such as the electron donating rate constant (kED) of PyC, correlated well with kd (r>0.87, P < 0.05) of phenols. Analysis of 13 phenols showed that Egap and ELUMO negatively correlated with their kd, confirming the importance of the electronic properties of phenols to their degradation kinetics. This study highlights the importance of PyC electron transfer kinetics parameters for phenols degradation and manipulation of PyC electron transfer rate may accelerate organic pollutant removal, which contributes to a deeper understanding of the environmental behavior and application of PyC systems.

Synergistic biochar and Serratia marcescens tackle toxic metal contamination: A multifaceted machine learning approach

Metal contamination in soil poses environmental and health risks requiring effective remediation strategies. This study introduces an innovative approach of synergistically employing biochar and bacterial inoculum of Serratia marcescens to address toxic metal (TM) contamination. Physicochemical, enzymatic, and microbial analyses were conducted, employing integrated biomarker response (IBR) and machine-learning approaches for toxicity estimation. The combined application significantly reduced the Cd, Cr, and Pb concentrations by 71.6, 31.2, and 57.1%, respectively, while the Cu concentration increased by 85% in the individual Serratia marcescens treatment. Biochar enhanced microbial biomass by 33-44% after 25 days. Noteworthy physicochemical improvements included a 44.7% increase in organic content and a decrease in pH and electrical conductivity. The K⁺ and Ca2⁺ concentrations increased by 196.9 and 21.6%, respectively, while the Mg2⁺ content decreased by 86.4%. Network analysis revealed intricate relationships, displaying direct and indirect negative correlations between metals and soil physicochemical parameters. The IBR index values indicated effective mitigation of TM toxicity in Serratia marcescens and biochar with individual and combined treatments. Binary classification demonstrated high sensitivity (80.1%) and specificity (80.5%) in identifying TM-contaminated soil. These findings indicate significant biochar- and Serratia marcescens-induced impacts on toxic metal availability, physicochemical properties, and enzymatic activities in metal-contaminated soil, suggesting that blending soil with biochar and microorganisms is an effective remediation strategy.

Molecular fractionation mediates genotoxicity evolution of hydrochar-derived dissolved organic matter at the iron oxyhydroxides-water interface

Adsorption fractionation of dissolved organic matter (DOM) induced by soil minerals is a common geochemical process, which has been widely documented on natural DOM. Hydrochar is a promising functional material in soil remediation but can continuously release abundant endogenic DOM with potential biotoxicity. However, adsorption fractionation at molecular level and its influence on toxicity evolution of hydrochar-derived DOM (HDOM) at genetic level at the soil-water interface remain poorly understood. Herein, we investigated the molecular fractionation of HDOM on three typical soil iron minerals (i.e., ferrihydrite, goethite, and hematite). Results from ultrahigh-resolution mass spectrum showed that HDOM molecules with high molecular weight and high contents of unsaturated oxidized or aromatic structures (e.g., unsaturated phenolic compounds, polyphenols, and organic acids) were preferentially absorbed by iron oxyhydroxides, while aliphatic molecules and poorly oxygenated compounds (e.g., hydrocarbon, phenols, and alcohols) were retained in aqueous phase. Furthermore, we quantitatively evaluated their genotoxicity variation using a toxicogenomics assay using green fluorescence protein-fused whole-cell array, and results showed that oxidative, protein, membrane, and DNA stresses were primary responses upon exposure to original HDOM. Interface fractionation induced by iron oxyhydroxides significantly reduced genotoxicity of HDOM, especially for oxidative, membrane and DNA stresses. Overall, the selective absorption of HDOM molecules by iron oxyhydroxides shifted its biotoxicity, which might change the ecological effects of hydrochar amendment, e.g., microbial community structure, environmental pollutant transformation, and even the ecological function of terrestrial and aquatic ecosystems. These findings would contribute to unraveling the environmental geochemistry process of HDOM in the natural soil-water interface and provide a new insight into the biotoxicity of hydrochar usage to terrestrial and aquatic environments.

Acid-modified hydrochar for higher biodegradation rate of atrazine in various conditions by Paenarthrobacter sp. KN0901: Higher cell viability and bacterial number

Microbial remediation is a viable and eco-friendly approach for decontaminating pollution. However, its effectiveness can be limited by the microorganisms' survival and growth in changing environments. Hydrochar materials have been utilized in this study to increase the growth and atrazine degradation capabilities of Paenarthrobacter sp. KN0901, a strain capable of atrazine biodegradation. Acid-modified hydrochars exhibited a higher carbonation rate, specific surface area, and number of defect sites compared to raw hydrochar. Following three days of incubation at 15 °C, the atrazine degradation rate increased from 90.7 % to 98.2 % when utilizing H3PO4-modified hydrochar (PHC). Additionally, the addition of PHC resulted in an increase in both bacterial concentration and cell viability of strain KN0901, by 1.6 and 1.4 times, respectively. Under various conditions, including temperatures of 4 ºC and 35 ºC, as well as pH levels of 5 and 9, and dd·H2O media, PHC exhibited a significant enhancement in atrazine degradation and cell viability of strain KN0901. Furthermore, PHC demonstrated the ability to sustain high proliferation and viability of strain KN0901 over five cycles, indicating its remarkable stability and biocompatibility. This study offers a new perspective on the development and application of bioremediation approaches in restoring atrazine-polluted environments, even under challenging conditions.

Bioremediation of petroleum-contaminated soil based on both toxicity risk control and hydrocarbon removal-progress and prospect

Petroleum contamination remains a worldwide issue requiring cost-effective bioremediation techniques. However, establishing a universal bioremediation strategy for all types of oil-polluted sites is challenging. This difficulty arises from the heterogeneity of soil textures, the complexity of oil products, and the variations in local climate and environment across different oil-contaminated regions. Several factors can impede bioremediation efficacy: (i) differences in bioavailability and biodegradability between aliphatic and aromatic fractions of crude oil; (ii) inconsistencies between hydrocarbon removal efficiency and toxicity attenuation during remediation; (iii) varying adverse effect of aliphatic and aromatic fractions on soil microorganisms. This review examines the ecotoxicity risk of petroleum contamination to soil fauna and flora. It also discusses three primary bioremediation strategies: biostimulation with nutrients, bioaugmentation with petroleum degraders, and phytoremediation with plants. Based on current research and state-of-the-art challenges, we highlighted future research scopes should focus on (i) exploring the ecotoxicity differentiation of aliphatic and aromatic fractions of crude oil, (ii) establishing unified risk factors and indicators for evaluating oil pollution toxicity, (iii) determining the fate and transformation of aliphatic and aromatic fractions of crude oil using advanced analytical techniques, and (iv) developing combined bioremediation techniques that improve petroleum removal and ecotoxicity attenuation.

Biochar alters the soil fauna functional traits and community diversity: A quantitative and cascading perspective

With the widespread use of biochar, the cascading effects of biochar exposure on soil fauna urgently require deeper understanding. A meta-analysis quantified hierarchical changes in functional traits and community diversity of soil fauna under biochar exposure. Antioxidant enzymes (24.1 %) did not fully mitigate the impact of MDA (13.5 %), leading to excessive DNA damage in soil fauna (21.2 %). Concurrently, reproduction, growth, and survival rates decreased by 20.2 %, 8.5 %, and 21.2 %, respectively. Due to a 39.7 % increase in avoidance behavior of soil fauna towards biochar, species richness ultimately increased by 80.2 %. Compared to other feeding habits, biochar posed a greater threat to the survival of herbivores. Additionally, macrofauna were the most sensitive to biochar. The response of soil fauna also depended on the type, size, concentration, and duration of biochar exposure. It should be emphasized that as exposure concentration increased, the damage to soil fauna became more severe. Furthermore, the smaller the biochar sizes, the greater the damage to soil fauna. To mitigate the adverse effects on soil fauna, this study recommens applying biochar at appropriate times and selecting large sizes in low to medium concentrations. These findings confirm the threat of biochar to soil health from the perspective of soil fauna.

Biochar regulates the functions of keystone taxa to reduce p-coumaric acid accumulation in soil

Introduction

Applying biochar (BC) to reduce toxic substance accumulation in soil, either through direct adsorption or modulation of the microbial community, has received considerable attention. However, a knowledge gap exists regarding how BC regulates microbial community structure and functions to mitigate toxic substance accumulation.

Methods

We previously identified p-coumaric acid (p-CA) as a representative autotoxin in tobacco rhizosphere soil. On this basis, this study simulated a soil environment with p-CA accumulation to investigate the impacts of BC on p-CA, soil physicochemical properties, and microbial community structure and function.

Results

The results showed that p-CA could be directly adsorbed onto BC, which followed the pseudo-second-order kinetic model (R 2 = 0.996). A pot experiment revealed that BC significantly reduced soil p-CA, altered soil microbial composition, and enhanced bacterial community diversity. A weighted correlation network analysis showed a close association between taxon 1 in the microbial network and p-CA, suggesting a pivotal role for this taxon in reducing p-CA, with Devosia and Nocardioides identified as potential key contributors to this process. The prediction of possible keystone taxa functions showed that BC increased the relative abundances of aromatic compound degraders. Mantel tests indicated that soil organic matter exerted the greatest influence on keystone taxa functions and hub genera.

Discussion

These findings suggest that BC may either directly chemisorb p-CA or indirectly facilitate p-CA degradation by regulating the functioning of keystone taxa. The results of this study provide a novel perspective for further investigation of the mechanisms through which BC reduces the accumulation of toxic substances in soil.

Unveiling biochar potential to promote safe crop production in toxic metal(loid) contaminated soil: A meta-analysis

Biochar application emerges as a promising and sustainable solution for the remediation of soils contaminated with potentially toxic metal (loid)s (PTMs), yet its potential to reduce PTM accumulation in crops remains to be fully elucidated. In our study, a hierarchical meta-analysis based on 276 research articles was conducted to quantify the effects of biochar application on crop growth and PTM accumulation. Meanwhile, a machine learning approach was developed to identify the major contributing features. Our findings revealed that biochar application significantly enhanced crop growth, and reduced PTM concentrations in crop tissues, showing a decrease trend of grains (36.1%, 33.6-38.6%) > shoots (31.1%, 29.3-32.8%) > roots (27.5%, 25.7-29.2%). Furthermore, biochar modifications were found to amplify its remediation potential in PTM-contaminated soils. Biochar application was observed to provide favorable conditions for reducing PTM uptake by crops, primarily through decreasing available PTM concentrations and improving overall soil quality. Employing machine learning techniques, we identified biochar properties, such as surface area and C content as a key factor in decreasing PTM bioavailability in soil-crop systems. Furthermore, our study indicated that biochar application could reduce probabilistic health risks associated with of the presence of PTMs in crop grains, thereby contributing to human health protection. These findings highlighted the essential role of biochar in remediating PTM-contaminated lands and offered guidelines for enhancing safe crop production.

Review on biochar as a sustainable green resource for the rehabilitation of petroleum hydrocarbon-contaminated soil

Petroleum pollution is one of the primary threats to the environment and public health. Therefore, it is essential to create new strategies and enhance current ones. The process of biological reclamation, which utilizes a biological agent to eliminate harmful substances from polluted soil, has drawn much interest. Biochars are inexpensive, environmentally beneficial carbon compounds extensively employed to remove petroleum hydrocarbons from the environment. Biochar has demonstrated an excellent capability to remediate soil pollutants because of its abundant supply of the required raw materials, sustainability, affordability, high efficacy, substantial specific surface area, and desired physical-chemical surface characteristics. This paper reviews biochar's methods, effectiveness, and possible toxic effects on the natural environment, amended biochar, and their integration with other remediating materials towards sustainable remediation of petroleum-polluted soil environments. Efforts are being undertaken to enhance the effectiveness of biochar in the hydrocarbon-based rehabilitation approach by altering its characteristics. Additionally, the adsorption, biodegradability, chemical breakdown, and regenerative facets of biochar amendment and combined usage culminated in augmenting the remedial effectiveness. Lastly, several shortcomings of the prevailing methods and prospective directions were provided to overcome the constraints in tailored biochar studies for long-term performance stability and ecological sustainability towards restoring petroleum hydrocarbon adultered soil environments.

Removal of environmental pollutants using biochar: current status and emerging opportunities

In recent times, biochar has emerged as a novel approach for environmental remediation due to its exceptional adsorption capacity, attributed to its porous structure formed by the pyrolysis of biomass at elevated temperatures in oxygen-restricted conditions. This characteristic has driven its widespread use in environmental remediation to remove pollutants. When biochar is introduced into ecosystems, it usually changes the makeup of microbial communities by offering a favorable habitat. Its porous structure creates a protective environment that shields them from external pressures. Consequently, microorganisms adhering to biochar surfaces exhibit increased resilience to environmental conditions, thereby enhancing their capacity to degrade pollutants. During this process, pollutants are broken down into smaller molecules through the collaborative efforts of biochar surface groups and microorganisms. Biochar is also often used in conjunction with composting techniques to enhance compost quality by improving aeration and serving as a carrier for slow-release fertilizers. The utilization of biochar to support sustainable agricultural practices and combat environmental contamination is a prominent area of current research. This study aims to examine the beneficial impacts of biochar application on the absorption and breakdown of contaminants in environmental and agricultural settings, offering insights into its optimization for enhanced efficacy.

Application of microbial agents in organic solid waste composting: a review

The rapid growth of organic solid waste has recently exacerbated environmental pollution problems, and its improper treatment has led to the loss of a large number of biomass resources. Here, we expound the advantages of microbial agents composting compared with conventional organic solid waste treatment technology, and review the important role of microbial agents composting in organic solid waste composting from the aspects of screening and identification, optimization of conditions, mechanism of action, combination with other technologies and ultra-high-temperature and ultra-low-temperature microbial composting. We discuss the value of microorganisms with different growth conditions in organic solid waste composting, and put forward a seasonal multi-temperature composite microbial composting technology. Provide new ideas for the all-round treatment of microbial agents in organic solid waste in the future. © 2024 Society of Chemical Industry.

Enhanced removal of 2,4-dichlorophenol by a novel biotic-abiotic hybrid system based on zeolitic imidazolate framework-8

Biotic-abiotic hybrid systems have recently emerged as a potential technique for stable and efficient removal of persistent contaminants due to coupling of microbial catabolic with abiotic adsorption/redox processes. In this study, Burkholderia vietnamensis C09V (B.V.C09V) was successfully integrated with a Zeolitic Imidazolate Framework-8 (ZIF-8) to construct a state-of-art biotic-abiotic system using polyvinyl alcohol/ sodium alginate (PVA/SA) as media. The biotic-abiotic system (PVA/SA-ZIF-8 @B.V.C09V) was able to remove 99.0 % of 2,4-DCP within 168 h, which was much higher than either PVA/SA, PVA/SA-ZIF-8 or PVA/SA@B.V.C09V (53.8 %, 72.6 % and 67.2 %, respectively). Electrochemical techniques demonstrated that the carrier effect of PVA/SA and the driving effect of ZIF-8 collectively accelerated electron transfer processes associated with enzymatic reactions. In addition, quantitative-PCR (Q-PCR) revealed that ZIF-8 stimulated B.V.C09V to up-regulate expression of tfdB, tfdC, catA, and catC genes (2.40-, 1.68-, 1.58-, and 1.23-fold, respectively), which encoded the metabolism of related enzymes. Furthermore, the effect of key physical, chemical, and biological properties of PVA/SA-ZIF-8 @B.V.C09V on 2,4-DCP removal were statistically investigated by Spearman correlation analysis to identify the key factors that promoted synergistic removal of 2,4-DCP. Overall, this study has created an innovative new strategy for the sustainable remediation of 2,4-DCP in aquatic environments.

Emerging technologies for the removal of pesticides from contaminated soils and their reuse in agriculture

Pesticides are becoming more prevalent in agriculture to protect crops and increase crop yields. However, nearly all pesticides used for this purpose reach non-target crops and remain as residues for extended periods. Contamination of soil by widespread pesticide use, as well as its toxicity to humans and other living organisms, is a global concern. This has prompted us to find solutions and develop alternative remediation technologies for sustainable management. This article reviews recent technological developments for remediating pesticides from contaminated soil, focusing on the following major points: (1) The application of various pesticide types and their properties, the sources of pesticides related to soil pollution, their transport and distribution, their fate, the impact on soil and human health, and the extrinsic and intrinsic factors that affect the remediation process are the main points of focus. (2) Sustainable pesticide degradation mechanisms and various emerging nano- and bioelectrochemical soil remediation technologies. (3) The feasible and long-term sustainable research and development approaches that are required for on-site pesticide removal from soils, as well as prospects for applying them directly in agricultural fields. In this critical analysis, we found that bioremediation technology has the potential for up to 90% pesticide removal from the soil. The complete removal of pesticides through a single biological treatment approach is still a challenging task; however, the combination of electrochemical oxidation and bioelectrochemical system approaches can achieve the complete removal of pesticides from soil. Further research is required to remove pesticides directly from soils in agricultural fields on a large-scale.

Engineered lignocellulosic based biochar to remove endocrine-disrupting chemicals: Assessment of binding mechanism

The safety and health of aquatic organisms and humans are threatened by the increasing presence of pollutants in the environment. Endocrine disrupting chemicals are common pollutants which affect the function of endocrine and causes adverse effects on human health. These chemicals can disrupt metabolic processes by interacting with hormone receptors upon consumptions by humans or aquatic species. Several studies have reported the presence of endocrine disrupting chemicals in waterbodies, food, air and soil. These chemicals are associated with increasing occurrence of obesity, metabolic disorders, reproductive abnormalities, autism, cancer, epigenetic variation and cardiovascular risk. Conventional treatment processes are expensive, not environment friendly and unable to achieve complete removal of these harmful chemicals. In recent years, biochar from different sources has gained a considerable interest due to their adsorption efficiency with porous structure and large surface areas. biochar derived from lignocellulosic biomass are widely used as sustainable catalysts in soil remediation, carbon sequestration, removal of organic and inorganic pollutants and wastewater treatment. This review conceptualizes the production techniques of biochar from lignocellulosic biomass and explores the functionalization and interaction of biochar with endocrine-disrupting chemicals. This review also identifies the further needs of research. Overall, the environmental and health risks of endocrine-disrupting chemicals can be dealt with by biochar produced from lignocellulosic biomass as a sustainable and prominent approach.

Long-term Application of Agricultural Amendments Regulate Hydroxyl Radicals Production during Oxygenation of Paddy Soils

Hydroxyl radicals (•OH) play a significant role in contaminant transformation and element cycling during redox fluctuations in paddy soil. However, these important processes might be affected by widely used agricultural amendments, such as urea, pig manure, and biochar, which have rarely been explored, especially regarding their impact on soil aggregates and associated biogeochemical processes. Herein, based on five years of fertilization experiments in the field, we found that agricultural amendments, especially coapplication of fertilizers and biochar, significantly increased soil organic carbon contents and the abundances of iron (Fe)-reducing bacteria. They also substantially altered the fraction of soil aggregates, which consequently enhanced the electron-donating capacity and the formation of active Fe(II) species (i.e., 0.5 M HCl-Fe(II)) in soil aggregates (0-2 mm), especially in small aggregates (0-3 μm). The highest contents of active Fe(II) species in small aggregates were mainly responsible for the highest •OH production (increased by 1.7-2.4-fold) and naphthalene attenuation in paddy soil with coapplication of fertilizers and biochar. Overall, this study offers new insights into the effects of agricultural amendments on regulating •OH formation in paddy soil and proposes feasible strategies for soil remediation in agricultural fields, especially in soils with frequent occurrences of redox fluctuations.

Activated carbon as a strong DOM adsorbent mitigates antimony and arsenic release in flooded mining-impacted soils

In Southern China, the co-occurrence of arsenic (As) and antimony (Sb) contamination in soils around Sb mines presents an environmental challenge. During the flooding period of mining-impacted soils, anaerobic reduction of iron (Fe) oxides enhances the mobilization and bioavailability of Sb and As, further elevating the risk of Sb and As entering the food chain. To address this problem, activated carbon (AC) and biochar (BC) were applied to remediate flooded mining-impacted soils. Our results explored that AC can significantly decrease mobilization by 9-97 % for Sb and 9-67 % for As through inhibiting Fe(III) mineral reduction and dissolution in flooded soils. In contrast, there was no significant effect of BC. This was attributed to the strong adsorption of soil dissolved organic matter (DOM) by AC compared to BC, while DOM as electron shuttle is crucial for microbial Fe(III) reduction. Consequently, the DOM sequestration by AC effectively mitigates Sb and As leaching in contaminated mining soils.

Mitigating microplastic stress on peanuts: The role of biochar-based synthetic community in the preservation of soil physicochemical properties and microbial diversity

Tire-derived rubber crumbs (RC), as a new type of microplastics (MPs), harms both the environment and human health. Excessive use of plastic, the decomposition of which generates microplastic particles, in current agricultural practices poses a significant threat to the sustainability of agricultural ecosystems, worldwide food security and human health. In this study, the application of biochar, a carbon-rich material, to soil was explored, especially in the evaluation of synthetic biochar-based community (SynCom) to alleviate RC-MP-induced stress on plant growth and soil physicochemical properties and soil microbial communities in peanuts. The results revealed that RC-MPs significantly reduced peanut shoot dry weight, root vigor, nodule quantity, plant enzyme activity, soil urease and dehydrogenase activity, as well as soil available potassium, and bacterial abundance. Moreover, the study led to the identification highly effective plant growth-promoting rhizobacteria (PGPR) from the peanut rhizosphere, which were then integrated into a SynCom and immobilized within biochar. Application of biochar-based SynCom in RC-MPs contaminated soil significantly increased peanut biomass, root vigor, nodule number, and antioxidant enzyme activity, alongside enhancing soil enzyme activity and rhizosphere bacterial abundance. Interestingly, under high-dose RC-MPs treatment, the relative abundance of rhizosphere bacteria decreased significantly, but their diversity increased significantly and exhibited distinct clustering phenomenon. In summary, the investigated biochar-based SynCom proved to be a potential soil amendment to mitigate the deleterious effects of RC-MPs on peanuts and preserve soil microbial functionality. This presents a promising solution to the challenges posed by contaminated soil, offering new avenues for remediation.

A comparative evaluation of biochar and Paenarthrobacter sp. AT5 for reducing atrazine risks to soybeans and bacterial communities in black soil

Application of biochar and inoculation with specific microbial strains offer promising approaches for addressing atrazine contamination in agricultural soils. However, determining the optimal method necessitates a comprehensive understanding of their effects under similar conditions. This study aimed to evaluate the effectiveness of biochar and Paenarthrobacter sp. AT5, a bacterial strain known for its ability to degrade atrazine, in reducing atrazine-related risks to soybean crops and influencing bacterial communities. Both biochar and strain AT5 significantly improved atrazine degradation in both planted and unplanted soils, with the most substantial reduction observed in soils treated with strain AT5. Furthermore, bioaugmentation with strain AT5 outperformed biochar in enhancing soybean growth, photosynthetic pigments, and antioxidant defenses. While biochar promoted higher soil bacterial diversity compared to strain AT5, the latter selectively enriched specific bacterial populations. Additionally, soil inoculated with strain AT5 displayed a notable increase in the abundance of key genes associated with atrazine degradation (trzN, atzB, and atzC), surpassing the effects observed with biochar addition, thus highlighting its effectiveness in mitigating atrazine risks in soil.

Emerging contaminants: A One Health perspective

Environmental pollution is escalating due to rapid global development that often prioritizes human needs over planetary health. Despite global efforts to mitigate legacy pollutants, the continuous introduction of new substances remains a major threat to both people and the planet. In response, global initiatives are focusing on risk assessment and regulation of emerging contaminants, as demonstrated by the ongoing efforts to establish the UN's Intergovernmental Science-Policy Panel on Chemicals, Waste, and Pollution Prevention. This review identifies the sources and impacts of emerging contaminants on planetary health, emphasizing the importance of adopting a One Health approach. Strategies for monitoring and addressing these pollutants are discussed, underscoring the need for robust and socially equitable environmental policies at both regional and international levels. Urgent actions are needed to transition toward sustainable pollution management practices to safeguard our planet for future generations.