Sorption, transport and biodegradation - An insight into bioavailability of persistent organic pollutants in soil

Synergy, antagonism, and feedback between soil properties and polychlorinated biphenyls

In this paper, the migration and transformation behavior of polychlorinated biphenyls (PCBs) in soil environmental system and their interaction with environmental factors were reviewed. The migration and transformation of PCBs are mainly regulated by soil organic matter, temperature and microorganisms. Soil organic matter immobilizes PCBs through adsorption sites and functional groups (including carbonyl and carboxyl groups), and microorganisms reduce and dechlorinate PCBs by reducing dehalogenase (anaerobic), biphenyl dioxygenase (aerobic) and other biological enzymes. However, these mechanisms are influenced by pH, temperature, water content, microbial population, and PCBs structure. In addition, there are significant differences in the response of PCBs conversion to oxygen content (aerobic and anaerobic) in soil systems. However, most current studies focus on the environmental behavior of PCBs from the perspective of single factors such as pH, soil organic matter, and microorganisms, and the comprehensive analysis under the interaction of multiple factors is limited. Therefore, the synergistic, antagonistic and feedback effects of PCBs in soil systems are analyzed comprehensively for the first time in this paper, which fills the gap of existing research. The aim is to provide a theoretical framework for the future environmental behavior effect of PCBs in soil and the contribution ability of environmental factors to PCBs pollution.

The role of electroactive biofilms in enhanced para-chlorophenol transformation collaborated with biosynthetic palladium nanoparticles

Bioremediation is a cost-effective strategy for decomposition of chlorinated organic contaminants, but its application is often hindered by the generation of toxic chlorinated byproducts. Though the design of functional biofilms, incorporating microbially-inspired catalytic materials, has emerged as a promising solution for tackling the byproducts issues, the microbial mechanisms driving these processes remain inadequately understood. This study demonstrates a hybrid electroactive biofilm (EAB)-palladium nanoparticles (Pd NPs) system that effectively separates the dechlorination and mineralization of para-chlorophenol (4-CP), and most importantly, it provides new insights into the microbial and genetic roles of EABs in this process. Under an applied potential of -0.6 V, Pd NPs via palladate reduction were biogenically synthesized and deposited on the cytomembranes within the biofilm, achieving an 82 % decrease in 4-CP concentration within 48 h. The ultra-performance liquid chromatogram and mass spectrum confirmed that 4-CP was initially dechlorinated to phenol by the biogenic Pd NPs before undergoing further degradation by the biofilm, effectively preventing toxic chlorinated byproducts. The Dechloromonas, Pseudomonas, and Geobacter were identified as predominant genera in the system and the metagenomics analysis noted increased relative abundance of ring-cleavage genes like pcaG, dmpB/xylE, and catA. Importantly, the abundance of dmpB/xylE was primarily associated with Dechloromonas and Pseudomonas, further highlighted that the dmpB/xylE-pathway was important for rapid 4-CP decomposition in the system. This study advances the understanding of EAB-Pd NPs synergy, showcasing an innovative and sustainable approach for the efficient removal of halogenated pollutants.

Stereoisomer-specific bacterial mechanisms for hexabromocyclododecane biotransformation

Hexabromocyclododecane (HBCD), a flame retardant classified as a Persistent Organic Pollutant (POP), undergoes stereoisomer-specific microbial transformation with significant environmental and health implications. However, the underlying mechanisms of this stereoisomer-specific microbial transformation remain poorly understood. In this study, high-purity HBCD chiral isomers were isolated using an optimized high-performance liquid chromatography (HPLC) method and their transformation by Acinetobacter hemolyticum sp. strain HW-2 was investigated through transcriptomic analysis. Within three days, strain HW-2 removed (+) α-, (-) α-, (+) β-, (-) β-, (+) γ-, and (-) γ-HBCD with respective removal efficiencies of 52.38 %, 71.08 %, 71.07 %, 63.34 %, 47.47 %, and 77.05 %. Transcriptomic data revealed stereoisomer-specific processes in HBCD transport, response, and transformation. Strain HW-2 upregulated major facilitator superfamily (MFS) transport genes for HBCD uptake, with distinct genes activated for different diastereoisomers. Compared to γ-HBCD, α- and β-HBCD exerted greater stress on strain HW-2, leading to increased expression of efflux genes and antioxidant-related genes. The transformation of HBCD stereoisomers involved distinct functional enzymes, with only (-) γ-HBCD metabolized via the aromatic compound metabolic pathway. This study elucidates the stereoisomeric-specific transformation mechanisms underlying HBCD transformation by strain HW-2, offering valuable insights for theoretical and practical applications in HBCD remediation.

Integrated landfarming strategy for remediation of HCH-contaminated soil: Synergistic effects of bioaugmentation, organic amendments, and nanoscale zero-valent iron

Hexachlorocyclohexane (HCH) isomers are toxic and persistent pollutants that pose serious risks to the environment and human health. Here we tested the capacity of various nature-based solutions to degrade HCH in contaminated soils of O Porriño area (Galicia, Spain). To this end, eight microcosms were established using combinations of tailor-made biostabilized organic amendments, nanoscale zero-valent iron (nZVI), and an autochthonous microbial inoculum. Throughout a 60-day experiment, we conducted HCH quantification, leachability tests, bacterial community analysis, and soil health assessment. Our results showed that landfarming alone achieved a reduction of up to 83 % in ∑HCH concentrations, demonstrating its cost-effectiveness, facilitated by the physical disruption of HCH aggregates and the presence of HCH-degrading bacteria as Sphingobium, Mesorhizobium and Cupriavidus. Organic amendments did not improve the HCH degradation rate of landfarming, but, notably, reduced HCH leachability and improved soil properties; the combination of the inoculum with the organic amendments revealed the same positive effects but a higher HCH depletion similar to that of landfarming. Thus, the synergistic effects of organic amending and inoculum in an integrated landfarming allows a reduction of the environmental risk and a potential long-term soil restoration, while a landfarming without amendments appear as a cost-effective option but only to reduce HCH contents. These findings aim to provide valuable insights into integrated approach for HCH large-scale landfarming remediation.

Bifunctional chitosan-modified urea-formaldehyde fertilizer for soil restoration and slow, sustained nitrogen release

Nutrient supply and heavy metals (HMs) remediation are key for agricultural development. However, achieving both goals with a single agent is challenging. In this study, bifunctional chitosan-modified urea-formaldehyde (CSUF) gel beads having a three-dimensional structure were developed to serve as a slow-release nitrogen fertilizer and a HM fixative for soil treatment. The adsorption capacities for Cd(II), Cu(II), and Cr(VI) reached 49.8, 6.63, and 40 mg/g, respectively. Further, over 10 d, CSUF removed 86 %, 93.28 %, and 91.32 % of Cd(II), Cu(II), and Cr(VI), respectively, from the soil while releasing 40 % of the nitrogen. Crucially, the adsorbed HM ions were not re-released, although the nitrogen continued to be released for 15 d. Plant growth experiments indicated that CSUF promoted mung bean sprout growth, increasing the dry and fresh weights by 33.33 % and 47.83 %, respectively, and significantly mitigating HM stress effects by reducing the Cd(II), Cu(II) and Cr(VI) content in the plant tissue by 89.28 %, 92.08 %, and 94.97 %, respectively. Overall, the bifunctional fertilizer shows potential for promoting sustainable agriculture.

Co-occurrence of multiple contaminants: Unentangling adsorption behaviour in agricultural soils

The co-occurrence of pesticides, pharmaceuticals, and MPs has resulted in combined toxicity and high risks to ecosystems and human health. However, understanding on the interactions among co-occurring pollutants in soils remains limited. This study focused on adsorption behaviour of a pesticide mixture (chlorpyrifos (CPF), pendimethalin (PDM) and pyraclostrobin (PCS)) in three soils (sandy soil (S1), loamy soil (S2), and silt soil (S3)) to examine the absorption behaviour of pesticides in the presence of the pharmaceutical compound albendazole (ALB) and starch-based microplastics (MPs). The results showed that ALB significantly decreased (p < 0.05) the adsorption of CPF, PDM, and PCS by 29 %-41 % in S1. The adsorption of CPF (+20 %) and PCS (+101 %) in S2 were significantly enhanced but PDM (-22 %) adsorption was inhibited by ALB. ALB also significantly (p < 0.05) promoted CPF and PCS adsorption in S3 by 39 % and 120 %, respectively, but did not change PDM adsorption. In soil-MP matrices, ALB significantly reduced the adsorption of CPF (-25 %), PDM (-26 %), and PCS (-21 %) in the S1-MP matrix, but no significant change in the S2 and S3-MP matrices was observed. Moreover, MPs significantly (p < 0.05) increased the adsorption of the pesticide mixture by 120-730 %, but reduced ALB adsorption by 11-24 % in soils. Further, regardless of ALB presence, correlation analysis suggested that Kd of pesticides showed positive correlations (p < 0.01) to soil organic matter, specific surface area, and clay content in soil matrices without MP-contamination, while no significant positive correlation between Kd of pesticides and soil properties was observed in soil-MPs matrices. This study indicates that co-occurring pollutants could alter the adsorption behaviour of pesticides in soil and thereby affect their bioavailability and mobility in the soil ecosystem. Further study is urgently needed to assess the ecotoxicity of co-occurring multi-contaminants, as well as their potential transport to other environmental compartments.

Occurrence, persistence and risk assessment of pesticide residues in European wheat fields: A continental scale approach

Pesticide residues in agricultural soils represent an environmental concern that requires special attention due to their potential ecological and public health risks. We analyzed 614 pesticides in 188 wheat fields across Europe subjected to both conventional and organic farming systems. At least one pesticide residue was detected in 141 soils. Seventy-eight pesticides or their metabolites were detected. The presence of pesticides was significantly higher in both number and concentration in conventional fileds (up to 0.98 mg kg-1) compared to organically managed sites (up to 0.40 mg kg-1). A total of 88 % of conventional fields and 63 % of organic fields contained two or more pesticides. Conversion from conventional to organic farming does not guarantee that soils will be pesticide-free in the short term. Fenbutatin oxide was the most frequently detected pesticide in both farming systems, followed by AMPA. Other substances, such as boscalid, epoxiconazole, diflufenican, tebuconazole, dinoterb, bixafen, and DEET, were found in ≥ 10 % of samples. Some Persistent Organic Pollutants, including dieldrin, endosulfan sulphate, and chlorpyrifos, were also detected. Ecological risks were higher in conventionally managed fields, with 46 % exhibiting high-risk levels, compared to just 1 % in organic fields. Epoxiconazole and boscalid were the substances with the highest risk levels.

Carbon, hydrogen, nitrogen and chlorine isotope fractionation during 3-chloroaniline transformation in aqueous environments by direct photolysis, TiO2 photocatalysis and hydrolysis

This study investigates carbon, hydrogen, nitrogen and chlorine isotope fractionation during the transformation of 3-chloroaniline (3-CA) via direct photolysis, TiO2 photocatalytic degradation at neutral condition and hydrolysis at pH 3, pH 7 and pH 11. Direct photolysis and ∙OH reaction (UV/H2O2) showed similar inverse isotope fractionation (ε) for carbon (1.9 ± 0.4 ‰ and 1.9 ± 0.6 ‰), for hydrogen (6.9 ± 1.6 ‰ and 5.0 ± 2.6 ‰), and inverse chlorine (13.9 ± 3.8 ‰ and 11.9 ± 2.9 ‰) and no nitrogen isotope fractionation, respectively. In contrast, significantly different normal carbon (-0.5 ± 0.1 ‰), inverse hydrogen (6.6 ± 1.5 ‰), and normal nitrogen (-0.8 ± 0.2 ‰) and inverse chlorine (5.2 ± 3.7 ‰) isotope fractionations were observed for the photocatalysis of 3-CA by TiO2 indicating a different degradation pathway as expected from ∙OH. For hydrolysis, inverse carbon (0.7 ± 0.3 ‰) and hydrogen (12.5 ± 3.3 ‰) isotope fractionation have been found at pH 3 while a normal carbon isotope fractionation was observed at pH 7 (-0.9 ± 0.3 ‰) and pH 11 (-1.3 ± 0.4 ‰), respectively. The correlation of 2H and 13C, 15N and 13C, and 37Cl and 13C isotope fractionation (Λ) allowed to distinguish direct photodegradation (ΛHC = -4.6 ± 1.7 (ΛHC-YORK=-5.2 ± 1.0) and ΛCl-C = 8.7 ± 0.9 (ΛCl-C-YORK=8.0 ± 0.3)), UV/H2O2 oxidation (ΛHC = -4.7 ± 1.0 (ΛHC-YORK=-4.5 ± 0.6) and ΛCl-C = 6.7 ± 0.8 (ΛCl-C-YORK=7.0 ± 1.0)), UV/TiO2 photocatalysis (ΛHC = -9.2 ± 3.1 (ΛHC-YORK=-9.3 ± 1.4), ΛCl-C = -10.2 ± 1.5 (ΛCl-C-YORK=-12.4 ± 1.7) and ΛNC -2.2 ± 0.3 (ΛNC-YORK=-2.3 ± 0.4)) and the modes of hydrolysis (ΛHC = 15.2 ± 5.3 (ΛHC-YORK=17.9 ± 2.9) and ΛCl-C = 0.9 ± 0.2 (ΛCl-C-YORK=1.1 ± 0.1) at pH 3) of 3-CA. The results were mechanistically interpreted highlighting the potential of CSIA to elucidate chemical oxidation and hydrolysis mechanisms of 3-CA.

Positive effects of composite material immobilized enzymes in 2,4,6-trichlorophenol degradation on soil properties and plant growth

2,4,6-Trichlorophenol (2,4,6-TCP) is recognized as a bio-toxic compound which is widely present in water and soil, and immobilized enzymes technology is widely used to degrade 2,4,6-TCP efficiently. However, previous studies have primarily focused on the degradation capability of immobilized enzymes towards 2,4,6-TCP, while the impacts on soil after degradation remain largely unexplored. In this study, sodium alginate/hydroxyapatite/chitosan microspheres immobilized with enzymes were used for 2,4,6-TCP degradation, and the impacts of degradation on soil properties and plant growth were explored. The results indicated that sodium alginate/hydroxyapatite/chitosan microsphere-immobilized enzymes achieved a removal rate of 94.72% for 160 mg L-1 2,4,6-TCP over 24 h and 73.17% for 160 mg kg-1 2,4,6-TCP contaminated soil over 72 h. Soil dehydrogenase and catalase activities were enhanced during degradation. The inhibitory effects of 2,4,6-TCP on wheat root and leaf elongation were mitigated by immobilized enzymes that degrade 2,4,6-TCP. Nutrients, such as fast-acting phosphorus and fast-acting potassium, were increased by immobilized enzymes that release nutrient elements. The changes of wheat growth observed in the soil after 2,4,6-TCP degradation by immobilized enzymes were driven by nutrients and degradation. These insights may facilitate the advancement of future applications of immobilized enzyme degradation technologies, contributing to sustainable soil management and ecological restoration.

Insights into anaerobic biotransformation of polychlorinated biphenyls in Dehalococcoides mccartyi CG1 through kinetic and stable isotopic analysis

Microbial degradation processes largely govern the fate of organic contaminants in the environment. Therefore, reliable evaluation of in situ biodegradation is essential for effective on-site contaminant management. Although compound-specific isotope analysis (CSIA) shows significant potential for assessing in situ attenuation and evaluating chemical and biodegradation mechanisms, empirical evidence supporting its application in the microbial degradation of polychlorinated biphenyls (PCBs) is still lacking. Microbial degradation of trace persistent organic pollutants is a multifaceted process influenced by various factors, with substrate concentration being a key factor affecting isotopic fractionation. Herein, to the best of our knowledge, for the first time, batch biodegradation experiments were conducted for analyzing the kinetics and carbon/chlorine isotope fractionation of chiral substrates (-)/(+)-PCB132 by Dehalococcoides mccartyi CG1 at varying substrate concentrations (0.3, 1.7, 2.4, 3.5, and 4.7 μM). The dechlorination of (-)/(+)-PCB132 was predominantly consistent with pseudo-first-order kinetics (kobs) in most cases. However, when the ratio of substrate concentration to the density of functional microorganisms falls below a specific threshold (<5.3 × 10-3 μmol/( × 1010 CG1 cells)), a decline in observed kobs is noted as degradation time increases, ultimately approaching the lower limit of bioavailability (kobs = 0). Notably, substantial normal isotope fractionation was observed for the first time during the anaerobic degradation of (-)/(+)-PCB132, with the isotopic enrichment factor (ƐC) varying from -1.27 ± 0.18‰ to -2.22 ± 0.01 for (-)/(+)-PCB132. Our findings indicate that, in addition to the effect of substrate concentration, the observed isotope fractionation of (-)/(+)-PCB132 was considerably affected by putative biodegradation activity. Enhanced activity within the anaerobic degradation system resulted in pronounced isotope masking. This study aims to contribute to a foundational understanding of bacterial reductive dehalogenation of PCBs at differing substrate concentrations while considering bioavailability.

Microplastic characterization and factors influencing its abundance in coastal wetlands: insights from the world's largest mangrove ecosystem, Sundarbans

Water and sediment samples were collected from 20 sampling sites within two major river systems within the world's largest mangrove ecosystem. The primary objectives of the study were to determine MPs' abundance, composition, and potential ecological risks and to identify the factors influencing their distribution and characteristics. Results revealed MP abundances, ranging from 2 to 53 items/m3 in water and 17 to 177 items/kg in sediment. The most prevalent types of MPs were films, fragments, foams, and fibers, with the most abundant fragments. Transparent MPs of various colors, such as red, green, blue, white, and yellow, were commonly observed. Additionally, sizes of MPs ranged from < 0.5 to 5 mm, with particles < 0.5 mm dominating in water and 4-5 mm particles prevailing in sediment. Six major polymers were identified, including polystyrene (PS), polyamide (PA), Polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), and ethylene propylene diene monomer (EPDM), with PS being the most abundant in both river systems. Linear mixed effect models showed that factors, such as distance from Mongla port and water velocity impacted MP abundance in water, while distance from Mongla port, total organic carbon (TOC), and total phosphorus (TP) contents affected their distribution in sediment. The Shannon-Weaver Index revealed a higher MP diversity in the Shela River compared to the Pasur. Overall, the pollution load index (PLI) and polymeric hazard index (PHI) indicated that MPs impacted both river systems, but the finding from the ecological risk index (ERI) was negligible at the individual sites. Our study recommends the long-term monitoring of MP abundance and implementation of strict regulations to reduce MPs in aquatic environments and proposes various engineering and biotechnological approaches for effective MP remediation. Further research is needed to identify both point and non-point sources of MPs and develop comprehensive strategies and policies to mitigate plastic pollution in the mangrove ecosystem.

Environmental and toxicological aspects of sulfamethoxazole photodegradation in the presence of oxidizing agents

Sulfamethoxazole (SMX) is a popular active substance, which is extensively applied to treat bacterial infections in humans and animals. Due to its widespread use, SMX enters the natural environment, where it can undergo degradation. Similarly to other emerging contaminants, SMX photodegradation and the use of oxidants in wastewater treatment processes can lead to the formation of potentially adverse transformation products for ecosystems. This study investigated the efficiency of SMX photodegradation in the presence of oxidizing agents (H2O2 and Fenton reagent). The potential environmental consequences of degradation product formation were analyzed based on experimental toxicity characterization. Standardized tests employing diverse organisms were utilized: Alivibrio fischeri (Microtox®), Daphnia magna (Daphtoxkit F®), and Lemna minor (Lemna sp. GIT). The potential environmental impact of the products identified in the reaction mixtures was evaluated using parameters describing aqueous solubility, hydrophobicity, toxicity, bioconcentration, persistence, and mobility. The analysis revealed that photodegradation produces transformation products with higher toxicity than SMX, as confirmed by in vitro tests of the reaction mixtures. Most of the detected compounds were found to have low mobility potential. The formation rates of key environmentally relevant transformation products, such as 1,4-benzoquinone, aniline, and phenol, were also discussed. The changes in total organic carbon (TOC) affected by photodegradation under the influence of the considered oxidizing agents were characterized.

Remote sampling of persistent organic pollutants by a home-made thin film device

Fast and accurate determination of persistent organic pollutants (POPs) plays a crucial role in addressing concerns related to public security and environmental safety. Herein, a unique thin film based solid phase microextraction (denoted as TF-SPME) method was reported and used for on-site analysis of POPs via loading the TFs into a homemade sampling device and equipped on a drone, which can load up to 6 pieces of TFs at the same time. The parallel 6 pieces of TFs offered significant advantages in terms of efficiency, accuracy, cost-effectiveness and comparability of sampling. The detection limit for polychlorinated biphenyls and polyaromatic hydrocarbons was as low as 0.03 ng L-1, far below the regulatory thresholds for drinking water prescribed by the United States Environmental Protection Agency. The standard deviations were ranged between 2.7 % and 9.9 %, showcasing its remarkable precision on POPs analysis. Then, by facilely equipping TF-SPME on a drone, remotely controlled sampling and on-site analysis in real water samples was realized. The concentrations were determined to be from 0.12 ng L-1 to 1.01 ng L-1 for PCBs and 0.53 ng L-1 to 19.93 ng L-1 for PAHs in the river water of Guangzhou downtown area. This study demonstrates the possibility of practical monitoring POPs with constructing novel sampling device and hopefully expands the toolbox for remote analysis of potential chemotoxicity and biotoxicity samples.

Data-Driven Machine Learning Strategy for Designing Metal-Ion-Doped γ-Bi2MoO6 Photocatalysts to Enhance Degradation Performance

Doped semiconductors are often used to improve photocatalytic efficiency and address the challenges of easy recombination of electron-hole pairs and poor photoluminescence. However, the reproducibility and complexity of experimental studies result in time-consuming and less cost-effective studies, and it is difficult to gain insights into the intrinsic properties of doped photocatalysts to control their performance. Introducing a machine learning approach, we constructed a photocatalytic model of transition-metal- and rare earth metal-ion-doped γ-Bi2MoO6. We selected 18 factors of preparation conditions and dopant ion properties, and constructed 806 data sets through literature collection for correlation analysis, paving the way for a more efficient and cost-effective research process. The results of our study are promising. The trained and improved XGboost model demonstrated high resistance to the variability caused by data segmentation, with a cross-validated model showing a coefficient of determination of 0.942. Through the combination of characteristic importance and Shapley additive explanation analysis, the importance and correlation trends of preparation conditions and dopant ion properties are obtained, especially the positive correlation trend of excitation time and preparation time and the negative correlation trend of atomic mass and bandwidth. Model prediction and experimental validation are used to demonstrate the effectiveness and behavioral prediction ability, and the Zn and Cd elements are successfully predicted for doping modification means. This study contributes to the modification and preparation of γ-Bi2MoO6 materials and provides a solid foundation for the efficient design of photocatalysts.

Development of an analytical method involving thiol methylation for the analysis of pentachlorothiophenol in food using gas chromatography-tandem mass spectrometry

Organic pollutants such as pentachlorothiophenol are a major environmental and food safety hazard owing to their degradation resistance and bioaccumulation potential. Since existing methods for detecting and quantifying PCTP are applicable only to environmental and aquatic samples, it is imperative to develop methods applicable to foods. Herein, a method involving gas chromatography-tandem mass spectrometry and optimized methylation conditions is proposed for quantifying PCTP concentrations in food. The method was validated using six food samples, and the performance parameters were found to be within acceptable standards. Reproducibility was the most significant factor influencing the measurement uncertainty. An analysis of 870 food samples covering agricultural, livestock, and fishery categories showed PCTP concentrations ranging from not detected (ND) to 13.63 ng/g wet weight, with dairy products (ND to 4.97 ng/g) showing the highest level. In animal-derived food, PCTP was detected only in eggs (ND to 3.10 ng/g) and mussels (ND to 4.36 ng/g).

Integrative modeling of POPs output flux from soil at a regional scale: A comprehensive approach

Plot-scale natural attenuation models provide valuable insights into localized pollutant behavior but struggle to account for regional-scale hydrological processes. Existing research has predominantly concentrated on single processes, lacking comprehensive models to describe the output flux of persistent organic pollutants (POPs) by transport and transformation from soil at a regional scale. To address this gap, a model was developed by combining natural attenuation processes (e.g., degradation, volatilization, plant uptake) with hydrological transport processes (e.g., leaching, water washout, sediment transport). The model was validated using data from a petrochemical area in China and compared with the previous model (mass balance and neural networks model) to assess pollutant output flux. Results indicated that water washout was the dominant output pathway from soil for both Phenanthrene (Phe) (94.67 %) and Benzo(a)pyrene (BaP) (98.33 %). Phe exhibited a broader output flux range (0-67.8 mg∙m-2∙a-1) compared to BaP (0-12.9 mg∙m-2∙a-1), due to its higher volatility and solubility. Performance evaluation through 10-fold cross-validation yielded coefficient of determination (R2) values greater than 0.7 and root mean square error (RMSE) below 3 %, outperforming the previous model. Sensitivity analysis revealed that the soil organic carbon mass fraction (foc) was the most influential parameter at both a plot and regional scale. This study fills a gap in environmental research by providing a comprehensive model for accurate estimates of POPs output fluxes from soil.

Impact mechanisms of various surfactants on the biodegradation of phenanthrene in soil: Bioavailability and microbial community responses

The present study was conducted to systematically explore the mechanisms underlying the impact of various surfactants (CTAB, SDBS, Tween 80 and rhamnolipid) at different doses (10, 100 and 1000 mg/kg) on the biodegradation of a model polycyclic aromatic hydrocarbon (PAH) by indigenous soil microorganisms, focusing on bioavailability and community responses. The cationic surfactant CTAB inhibited the biodegradation of phenanthrene within the whole tested dosage range by decreasing its bioavailability and adversely affecting soil microbial communities. Appropriate doses of SDBS (1000 mg/kg), Tween 80 (100, 1000 mg/kg) and rhamnolipid at all amendment levels promoted the transformation of phenanthrene from the very slow desorption fraction (Fvslow) to bioavailable fractions (rapid and slow desorption fractions, Frapid and Fslow), assessed via Tenax extraction. However, only Tween 80 and rhamnolipid at these doses significantly improved both the rates and extents of phenanthrene biodegradation by 22.1-204.3 and 38.4-76.7 %, respectively, while 1000 mg/kg SDBS had little effect on phenanthrene removal. This was because the inhibitory effects of anionic surfactant SDBS, especially at high doses, on the abundance, diversity and activity of soil microbial communities surpassed the bioavailability enhancement in dominating biodegradation. In contrast, the nonionic surfactant Tween 80 and biosurfactant rhamnolipid enhanced the bioavailability of phenanthrene for degradation and also that to specific degrading bacterial genera, which stimulated their growth and increased the abundance of the related nidA degradation gene. Moreover, they promoted the total microbial/bacterial biomass, community diversity and polyphenol oxidase activity by providing available substrates and nutrients. These findings contribute to the design of suitable surfactant types and dosages for mitigating the environmental risk of PAHs and simultaneously benefiting microbial ecology in soil through bioremediation.

Recyclable Biomimetic Sunflower Pollen-based Photocatalyst for Enhanced Degradation of Pharmaceuticals

Recent trends in addressing the impending water crisis focus on the development of innovative water treatment methods. This work utilizes pollen as a core template to synthesize highly efficient onion-like photocatalysts for pollutant mineralization. The study showcases a novel electrochemical synthesis method that maintains the structural integrity of pollen, resulting in increased surface area and enhanced photocatalytic activity. After 90-min of visible light irradiation, over 99% mineralization is achieved. These hybrid photocatalysts demonstrate exceptional stability and efficacy in degrading pollutants. The used photocatalysts can be recycled into biopellets with an ash content of less than 7% (weight), moisture content of less than 8% (weight), and a calorific value of ≈22.1 ± 0.3 MJ kg-1. Additionally, the resulting ashes serve as effective peroxymonosulphate activators for pollutant mineralization. This process offers sustainable waste management while minimizing waste production, providing a practical solution for water purification. The efficacy of this approach in pollutant removal is underscored by mineralization rates exceeding 99%.

Co-pollution risk of petroleum hydrocarbons and heavy metals in typically polluted estuarine wetlands: Insights from the Xiaoqing River

Excessive accumulation of total petroleum hydrocarbons (TPH) and heavy metals (HMs) in sediments poses a significant threat to the estuarine ecosystem. In this study, the spatial and temporal distribution, ecological risks, sources, and their impacts on the microbial communities of TPH and nine HMs in the estuarine sediments of the Xiaoqing River were determined. Results showed that the spatial distribution of TPH and HMs were similar but opposite in temporal. Ni, Cr, Pb, and Co concentrations were similar to the reference values (RVs). However, the other five HMs (Cu, Zn, Cd, As, and Hg) and TPH concentrations were 2.00-763.44 times higher than RVs; hence, this deserves attention, particularly for Hg. Owing to the water content of the sediments, Hg was mainly concentrated on the surface during the wet season and on the bottom during the dry season. Moreover, because of weak hydrodynamics and upstream pollutant sinks, TPH-HMs in the river were higher than those in the estuary. TPH and HM concentrations were negatively correlated with microbial diversity. Structural equation modeling showed that HMs (path coefficient = -0.50, p < 0.001) had a negative direct effect on microbial community structure and a positive indirect effect on TPH. The microbial community (path coefficient = 0.31, 0.01 < p < 0.05) was significantly correlated with TPH. In summary, this study explores both the chemical analysis of pollutants and their interaction with microbial communities, providing a better understanding of the co-pollution of TPH and HMs in estuarine sediments.

Mechanochemical remediation of contaminated soil: A review

Mechanochemical techniques have been garnering growing attention in remediation of contaminated soil. This paper summarizes the performance, mechanism, influential factors, and environmental impacts of mechanochemical remediation (MCR) for persistent organic pollutants (POPs) contaminated soil and heavy metal(loid) s (HMs) contaminated soil. Firstly, in contrast to other technologies, MCR can achieve desirable treatment of POPs, HMs, and co-contaminated soil, especially with high-concentration pollutants. Secondly, POPs undergo mineralization via interaction with mechanically activated substances, where aromatic and aliphatic pollutants in soil may go through varied degradation routes; inorganic pollutants can be firmly combined with soil particles by fragmentation and agglomeration induced by mechanical power, during which additives may enhance the combination but their contact with anionic metal(loid)s may be partially suppressed. Thirdly, the effect of MCR primarily hinges on types of milling systems, the accumulation of mechanical energy, and the use of reagents, which is basically regulated through operating parameters: rotation speed, ball-to-powder ratio, reagent-to-soil ratio, milling time, and soil treatment capacity; minerals like clay, metal oxides, and sand in soil itself are feasible reagents for remediation, and alien additives play a crucial role in synergist and detoxification; additionally, various physicochemical properties of soil might influence the mechanochemical effect to varying degrees, yet the key influential performance and mechanism remain unclear and require further investigation. Concerning the assessment of soil after treatment, attention needs to be paid to soil properties, toxicity of POPs' intermediates and leaching HMs, and long-term appraisement, particularly with the introduction of aggressive additives into the system. Finally, proposals for current issues and forthcoming advancements in this domain are enumerated in items. This review provides valuable insight into mechanochemical approaches for performing more effective and eco-friendly remediation on contaminated soil.

Dicyandiamide Applications Mitigate the Destructive Effects of Graphene Oxide on Microbial Activity, Diversity, and Composition and Nitrous Oxide Emission in Agricultural Soil

The widespread production and utilization of graphene oxide (GO) raise concerns about its environmental release and potential ecological impacts, particularly in agricultural soil. Effective nitrogen (N) management, especially through nitrification inhibitors like dicyandiamide (DCD), might mitigate the negative effects of GO exposure on soil microbes via N biostimulation. This study quantified changes in soil physicochemical properties, nitrous oxide (N2O) emissions, microbial activity, biomass, and community after treatments with GO and DCD. The GO exposure significantly reduced bacterial 16S rRNA gene abundance and the biomass of major bacterial phyla. It also stimulated pathways linked to human diseases. However, DCD application alleviated the negative effects of GO exposure on soil bacterial biomass. While DCD application significantly reduced soil N2O emission, the GO application tended to hinder the inhibiting performance of DCD. Our findings highlight the hazards of GO exposure to soil microbes and the potential mitigation strategy with soil N management.

Insights into the characteristics of changes in dissolved organic matter fluorescence components on the natural attenuation process of toluene

Natural attenuation (NA) is of great significance for the remediation of contaminated groundwater, and how to identify NA patterns of toluene in aquifers more quickly and effectively poses an urgent challenge. In this study, the NA of toluene in two typical soils was conducted by means of soil column experiment. Based on column experiments, dissolved organic matter (DOM) was rapidly identified using fluorescence spectroscopy, and the relationship between DOM and the NA of toluene was established through structural equation modeling analysis. The adsorption rates of toluene in clay and sandy soil were 39 % and 26 %, respectively. The adsorption capacity and total NA capacity of silty clay were large. The occurrence of fluorescence peaks of protein-like components and specific products indicated the occurrence of biodegradation. Arenimonas, Acidovorax and Brevundimonas were the main degrading bacteria identified in Column A, while Pseudomonas, Azotobacter and Mycobacterium were the main ones identified in Column B. The pH, ORP, and Fe(II) were the most important factors affecting the composition of microbial communities, which in turn affected the NA of toluene. These results provide a new way to quickly identify NA of toluene.

Biochar-based composites for removing chlorinated organic pollutants: Applications, mechanisms, and perspectives

Chlorinated organic pollutants constitute a significant category of persistent organic pollutants due to their widespread presence in the environment, which is primarily attributed to the expansion of agricultural and industrial activities. These pollutants are characterized by their persistence, potent toxicity, and capability for long-range dispersion, emphasizing the importance of their eradication to mitigate environmental pollution. While conventional methods for removing chlorinated organic pollutants encompass advanced oxidation, catalytic oxidation, and bioremediation, the utilization of biochar has emerged as a prominent green and efficacious method in recent years. Here we review biochar's role in remediating typical chlorinated organics, including polychlorinated biphenyls (PCBs), triclosan (TCS), trichloroethene (TCE), tetrachloroethylene (PCE), organochlorine pesticides (OCPs), and chlorobenzenes (CBs). We focus on the impact of biochar material properties on the adsorption mechanisms of chlorinated organics. This review highlights the use of biochar as a sustainable and eco-friendly method for removing chlorinated organic pollutants, especially when combined with biological or chemical strategies. Biochar facilitates electron transfer efficiency between microorganisms, promoting the growth of dechlorinating bacteria and mitigating the toxicity of chlorinated organics through adsorption. Furthermore, biochar can activate processes such as advanced oxidation or nano zero-valent iron, generating free radicals to decompose chlorinated organic compounds. We observe a broader application of biochar and bioprocesses for treating chlorinated organic pollutants in soil, reducing environmental impacts. Conversely, for water-based pollutants, integrating biochar with chemical methods proved more effective, leading to superior purification results. This review contributes to the theoretical and practical application of biochar for removing environmental chlorinated organic pollutants.

PFOA-contaminated soil remediation: a comprehensive review

Soil and groundwater contamination has been raised as a concern due to the capability of posing a risk to human health and ecology, especially in facing highly toxic and emerging pollutants. Because of the prevalent usage of perfluorooctanoic acid (PFOA), in industrial and production processes, and subsequently the extent of sites contaminated with these pollutants, cleaning up PFOA polluted sites is paramount. This research provides a review of remediation approaches that have been used, and nine remediation techniques were reviewed under physical, chemical, and biological approaches categorization. As the pollutant specifications, environmental implications, and adverse ecological effects of remediation procedures should be considered in the analysis and evaluation of remediation approaches, unlike previous research that considered a couple of PFAS pollutants and generally dealt with technical issues, in this study, the benefits, drawbacks, and possible environmental and ecological adverse effects of PFOA-contaminated site remediation also were discussed. In the end, in addition to providing sufficient and applicable understanding by comprehensively considering all aspects and field-scale challenges and obstacles, knowledge gaps have been found and discussed.

Antibacterial mechanism of Pseudomonas aeruginosa UKMP14T rhamnolipids against multidrug resistant Acinetobacter baumannii

Rhamnolipids, a major category of glycolipid biosurfactant, have recently gained enormous attention in medical field because of their relevance as effective antibacterial agents against a wide variety of pathogenic bacteria. Our previous studies have shown that rhamnolipids from an environmental isolate of Pseudomonas aeruginosa UKMP14T possess antibacterial, anti-adhesive and anti-biofilm activity against multidrug-resistant ESKAPE (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacter sp.) pathogens. However, the mechanism of their antibacterial action remains unclear. Thus, this study aimed to elucidate the mechanism of the antibacterial action of P. aeruginosa UKMP14T rhamnolipids by studying the changes in cells of one of the ESKAPE pathogens, Acinetobacter baumannii, which is the most difficult strain to kill. Results revealed that rhamnolipid treatment rendered A. baumannii cells more hydrophobic as evaluated through contact angle measurements. It also induced the release of cellular proteins measuring 510 μg/mL at a rhamnolipid concentration of 1000 μg/mL. In addition, rhamnolipids were found to be bactericidal in their action as they could permeate the inner membranes, leading to a leak-out of nucleotides. More than 50 % of the cells were found to be killed upon 1000 μg/mL rhamnolipid treatment as observed through fluorescence microscopy. Other cellular changes such as irregular shape and size, membrane perturbations, clumping, shrinkage and physical damage were clearly visible in SEM, FESEM and laser micrographs. Furthermore, rhamnolipid treatment inhibited the levels of acyl-homoserine lactones (AHLs) in A. baumannii, which are vital for their biofilm formation and virulence. The obtained results indicate that P. aeruginosa UKMP14T rhamnolipids target outer and inner bacterial membranes through permeation, including physical damage to the cells, leading to cell leakage. Furthermore, AHL inhibition appears to be the mechanism behind their anti-biofilm action. All these observations can be correlated to rhamnolipids' antibacterial effect against A. baumannii.

Meta-Analysis and Machine Learning Models for Anaerobic Biodegradation Rates of Organic Contaminants in Sediments and Sludge

Anaerobic biodegradation rates (half-lives) of organic chemicals are pivotal for environmental risk assessment and remediation. Traditional experimental evaluation, constrained by prolonged, oxygen-free conditions, struggles to keep pace with emerging contaminants. Data-driven machine learning (ML) models serve as promising complements. However, reported quantitative structure-biodegradation relationships or ML models on anaerobic biodegradation are mostly based on small data sets (<100 records) and neglect experimental conditions, usually achieving compromised predictions. This work aimed to develop ML models for predicting the biodegradation half-lives of organic pollutants in anaerobic environments (i.e., sediment/soil and sludge). Focusing on important features of both chemicals and experimental conditions, we first curated two data sets, one for sediment/soil (SED) and the other for sludge (SLD), covering 978 records for 206 chemicals from the literature, and then conducted a meta-analysis. Next, we built a binary classification (half-life of 30 days as the cutoff) model with an accuracy of 81% and a regression model with R2 of 0.56 for SED based on LightGBM (80% and 0.31 for SLD based on Extra tree, respectively). The model interpretations underscored the significance of experimental conditions (e.g., temperature and inoculum dosage), as evidenced by their high feature importance, and the models were found to correctly capture the effects of chemical substructures, for example, branched structures and aromatic rings prolonged half-lives while methyl group and ortho-substitution on rings shortened half-lives. The applicability domains of the models were also defined, resulting in reasonable prediction for the half-lives of 41% (SED) or 67% (SLD) of over 4000 persistent, bioaccumulative, and toxic chemicals. Overall, this study pioneers ML models for predicting the anaerobic degradation half-lives, offering valuable support for future evaluation and implementation of chemical anaerobic biodegradation.

Chemical inertness conversion of carbon fraction in coal gangue via N-doping for efficient benzo(a)pyrene degradation

Efficient degradation of organic pollutants in complex media via advanced oxidation processes (AOPs) is still critical and challenging. Herein, nitrogen (N)-doped coal gangue (CG) catalysts (N-CG) with economic competitiveness and environmental friendliness were successfully synthesized to activate peroxymonosulfate (PMS), exhibiting ultrafast degradation performance toward benzo(a)pyrene (BaP) with 100.00 % and 93.21 % in contaminated solution and soil under optimized condition, respectively. In addition, 0.4 N-CG possessed excellent reusability toward BaP degradation with over 80.00 % after five cycles. However, BaP removal efficiency was significantly affected by some co-existing anions (HCO3- and SO42-) and humic acid (HA) in solution and soil, as well as inhibited under alkaline conditions, especially pH ≥ 9. According to the characterizations, N-doping could promote the generation of pyridinic N and graphitic N in N-CG via high-temperature calcination, which was conducive to produce hydroxyl radical (•OH), sulfate radical (SO4•-), superoxide radical (•O2-) and single oxygen (1O2). In 0.4 N-CG/PMS system, 1O2 and •O2- were proved to be the predominant reactive oxygen species (ROSs) in BaP degradation, as well as •OH and SO4•- made certain contributions. To sum up, this work provided a promising strategy for synthesis of CG-based catalysts by chemical inertness conversion of carbon fracture via N-doping for PMS activation and opened a novel perspective for environmental remediation of hydrophobic and hydrophilic contaminants pollution.

Interfacial interactions between minerals and organic matter: Mechanisms and characterizations

Minerals and organic matter are essential components of soil, with minerals acting as the "bone" and organic matter as the "skin". The interfacial interactions between minerals and organic matter result in changes in their chemical composition, structure, functional groups, and physical properties, possessing a significant impact on soil properties, functions, and biogeochemical cycles. Understanding the interfacial interactions of minerals and organic matter is imperative to advance soil remediation technologies and carbon targets. Consequently, there is a growing interest in the physicochemical identification of the interfacial interactions between minerals and organic matter in the academic community. This review provides an overview of the mechanisms underlying these interactions, including adsorption, co-precipitation, occlusion, redox, catalysis and dissolution. Moreover, it surveys various methods and techniques employed to characterize the mineral-organic matter interactions. Specifically, the up-to-date spectroscopic techniques for chemical information and advanced microscopy techniques for physical information are highlighted. The advantages and limitations of each method are also discussed. Finally, we outline future research directions for interfacial interactions and suggests areas for improvement and development of characterization techniques to better understand the mechanisms of mineral-organic matter interactions.

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.

Historical sedimentary and evolutionary characteristics of POPs and EDCs in typical regions of the three Gorges reservoir, China

The historical sedimentary and evolutionary characteristics of persistent organic pollutants and endocrine disruptors in typical regions of the Three Gorges Reservoir are scarcely studied. Herein, the 96-year data on contaminated sediment history were reconstructed using Caesium 137 isotope dating. Polychlorinated biphenyl concentrations in the involved sediment cores ranged from non-detected (ND) to 11.39 ng/g. The concentrations of polycyclic aromatic hydrocarbons ranged from ND to 2075.20 ng/g and peaked in the 1970s owing to natural, agricultural and human activities. Further, phthalate esters (PAEs) and heavy metals (HMs) were detected at concentrations ranging from ND to 589.2 ng/g and 12.10-93.67 μg/g, respectively, with highest values recorded in the 1980s owing to rapid industrialisation and insufficient management during China's early reform and development stages. PAE and HM concentrations have increased in recent years, suggesting the need to focus on industrial and agricultural activities that have caused this impact. Although current pollutant concentrations in sediments do not pose a risk to the aquatic ecosystem, they should be continuously monitored.

Nonionic surfactant Tween 80-facilitated bacterial transport in porous media: A nonmonotonic concentration-dependent performance, mechanism, and machine learning prediction

The surfactant-enhanced bioremediation (SEBR) of organic-contaminated soil is a promising soil remediation technology, in which surfactants not only mobilize pollutants, but also alter the mobility of bacteria. However, the bacterial response and underlying mechanisms remain unclear. In this study, the effects and mechanisms of action of a selected nonionic surfactant (Tween 80) on Pseudomonas aeruginosa transport in soil and quartz sand were investigated. The results showed that bacterial migration in both quartz sand and soil was significantly enhanced with increasing Tween 80 concentration, and the greatest migration occurred at a critical micelle concentration (CMC) of 4 for quartz sand and 30 for soil, with increases of 185.2% and 27.3%, respectively. The experimental results and theoretical analysis indicated that Tween 80-facilitated bacterial migration could be mainly attributed to competition for soil/sand surface sorption sites between Tween 80 and bacteria. The prior sorption of Tween 80 onto sand/soil could diminish the available sorption sites for P. aeruginosa, resulting in significant decreases in deposition parameters (70.8% and 33.3% decrease in KD in sand and soil systems, respectively), thereby increasing bacterial transport. In the bacterial post-sorption scenario, the subsequent injection of Tween 80 washed out 69.8% of the bacteria retained in the quartz sand owing to the competition of Tween 80 with pre-sorbed bacteria, as compared with almost no bacteria being eluted by NaCl solution. Several machine learning models have been employed to predict Tween 80-faciliated bacterial transport. The results showed that back-propagation neural network (BPNN)-based machine learning could predict the transport of P. aeruginosa through quartz sand with Tween 80 in-sample (2 CMC) and out-of-sample (10 CMC) with errors of 0.79% and 3.77%, respectively. This study sheds light on the full understanding of SEBR from the viewpoint of degrader facilitation.

The unexpected effect of the compound microbial agent NP-M2 on microbial community dynamics in a nonylphenol-contaminated soil: the self-stability of soil ecosystem

Background

Nonylphenol (NP) is widely recognized as a crucial environmental endocrine-disrupting chemical and persistent toxic substance. The remediation of NP-contaminated sites primarily relies on biological degradation. Compound microbial products, as opposed to pure strains, possess a greater variety of metabolic pathways and can thrive in a wider range of environmental conditions. This characteristic is believed to facilitate the synergistic degradation of pollutants. Limited research has been conducted to thoroughly examine the potential compatibility of compound microbial agents with indigenous microflora, their ability to function effectively in practical environments, their capacity to enhance the dissipation of NP, and their potential to improve soil physicochemical and biological characteristics.

Methods

In order to efficiently eliminate NP in contaminated soil in an eco-friendly manner, a simulation study was conducted to investigate the impact of bioaugmentation using the functional compound microbial agent NP-M2 at varying concentrations (50 and 200 mg/L) on the dynamics of the soil microbial community. The treatments were set as follows: sterilized soil with 50 mg/kg NP (CK50) or 200 mg/kg NP (CK200); non-sterilized soil with 50 mg/kg NP (TU50) or 200 mg/kg NP (TU200); non-sterilized soil with the compound microbial agent NP-M2 at 50 mg/kg NP (J50) or 200 mg/kg NP (J200). Full-length 16S rRNA analysis was performed using the PacBio Sequel II platform.

Results

Both the indigenous microbes (TU50 and TU200 treatments) and the application of NP-M2 (J50 and J200 treatments) exhibited rapid NP removal, with removal rates ranging from 93% to 99%. The application of NP-M2 further accelerated the degradation rate of NP for a subtle lag period. Although the different treatments had minimal impacts on the soil bacterial α-diversity, they significantly altered the β-diversity and composition of the bacterial community. The dominant phyla were Proteobacteria (35.54%-44.14%), Acidobacteria (13.55%-17.07%), Planctomycetes (10.78%-11.42%), Bacteroidetes (5.60%-10.74%), and Actinobacteria (6.44%-8.68%). The core species were Luteitalea_pratensis, Pyrinomonas_methylaliphatogenes, Fimbriiglobus_ruber, Longimicrobium_terrae, and Massilia_sp003590855. The bacterial community structure and taxon distribution in polluted soils were significantly influenced by the activities of soil catalase, sucrase, and polyphenol oxidase, which were identified as the major environmental factors. Notably, the concentration of NP and, to a lesser extent, the compound microbial agent NP-M2 were found to cause major shifts in the bacterial community. This study highlights the importance of conducting bioremediation experiments in conjunction with microbiome assessment to better understand the impact of bioaugmentation/biostimulation on the potential functions of complex microbial communities present in contaminated soils, which is essential for bioremediation success.

Shifts in structure and dynamics of the soil microbiome in biofuel/fuel blend-affected areas triggered by different bioremediation treatments

The use of biofuels has grown in the last decades as a consequence of the direct environmental impacts of fossil fuel use. Elucidating structure, diversity, species interactions, and assembly mechanisms of microbiomes is crucial for understanding the influence of environmental disturbances. However, little is known about how contamination with biofuel/petrofuel blends alters the soil microbiome. Here, we studied the dynamics in the soil microbiome structure and composition of four field areas under long-term contamination with biofuel/fossil fuel blends (ethanol 10% and gasoline 90%-E10; ethanol 25% and gasoline 75%-E25; soybean biodiesel 20% and diesel 80%-B20) submitted to different bioremediation treatments along a temporal gradient. Soil microbiomes from biodiesel-polluted areas exhibited higher richness and diversity index values and more complex microbial communities than ethanol-polluted areas. Additionally, monitored natural attenuation B20-polluted areas were less affected by perturbations caused by bioremediation treatments. As a consequence, once biostimulation was applied, the degradation was slower compared with areas previously actively treated. In soils with low diversity and richness, the impact of bioremediation treatments on the microbiomes was greater, and as a result, the hydrocarbon degradation extent was higher. The network analysis showed that all abundant keystone taxa corresponded to well-known degraders, suggesting that the abundant species are core targets for biostimulation in soil remediation processes. Altogether, these findings showed that the knowledge gained through the study of microbiomes in contaminated areas may help design and conduct optimized bioremediation approaches, paving the way for future rationalized and efficient pollutant mitigation strategies.

Generic methodology to prevent food contamination by soil born legacy POPs in free range livestock

Government monitoring commonly includes regulating POPs in animal feed and products of animal origin, with many countries setting Maximum Residue Levels (MRLs) to ensure safe tolerable concentrations. However, these MRLs do not address the presence of most POP families in soil, where concentrations can be much higher due to the contaminants' strong affinity and persistence in comparison to other environmental matrices. Extensive damage to food and production systems during a pollution incident causing soil contamination by POPs lead to severe economic and social consequences for the affected area. To mitigate these effects, it is crucial to implement necessary measures for consumer protection while also focusing on rehabilitating conditions for food production, tailored to both commercial farms and private holders. In this context, the present work aims to develop and test a methodology for assessing the tolerable concentration of the most cancerogenic legacy POPs in soil for various livestock animals in diverse rearing systems ensuring the safety of food of animal origin. Therefore, we summarize existing knowledge about the risk of POP transfer in different livestock breeding systems via soil exposure, and modeling via a backward calculation from the MRLs the corresponding tolerable quantity of POPs that may be ingested by animals in the considered rearing system. Results of these simulations showed that soil ingestion is a predominant contamination pathway, which is a central factor in the risk assessment of POP exposure on livestock farms, especially in free-range systems. In field conditions of POP exposure, low productive animals may be more susceptible to uptake through soil than high-yielding animals, even if the feed respected MRLs. Results show that PCDD/Fs revealed the lowest security ratio for low productive dairy cows (1.5) compared to high productive ones (52). Laying hens with a productivity of 45% show also as a high sensitivity to POPs exposure via soil ingestion. Indeed, their security ratio for PCDD/Fs, lindane and DDT were 3, 2 and 1, respectively. In perspective, proposed methodology can be adapted for assessing the risk of industrial POPs newly listed in the Stockholm Convention. In practice, it could be useful for food producers to apprehend their own risk of chemical contamination.

Mechanisms of biochar assisted di-2-ethylhexyl phthalate (DEHP) biodegradation in tomato rhizosphere by metabolic and metagenomic analysis

The intensive accumulation of di-2-ethylhexyl phthalate (DEHP) in agricultural soils has resulted in severe environmental pollution that endangers ecosystem and human health. Biochar is an eco-friendly material that can help in accelerating organic pollutant degradation; nevertheless, its roles in enhancing DEHP removal in rhizosphere remain unclear. This work investigated the impacts of biochar dosage (0%-2.0%) on DEHP degradation performance in tomato rhizosphere by comprehensively exploring the change in DEHP metabolites, bacterial communities and DEHP-degrading genes. Our results showed a significant increase of rhizosphere pH, organic matter and humus by biochar amendment, which achieved a satisfactorily higher DEHP removal efficiency, maximally 77.53% in treatments with 1.0% of biochar. Biochar addition also remarkably changed rhizosphere bacterial communities by enriching some potential DEHP degraders of Nocardioides, Sphingomonas, Bradyrhizobium and Rhodanobacter. The abundance of genes encoding key enzymes (hydrolase, esterase and cytochrome P450) and DEHP-degrading genes (pht3, pht4, pht5, benC-xylZ and benD-xylL) were increased after biochar amendment, leading to the change in DEHP degradation metabolism, primarily from benzoic acid pathway to protocatechuic acid pathway. Our findings evidenced that biochar amendment could accelerate DEHP degradation by altering rhizosphere soil physicochemical variables, bacterial community composition and metabolic genes, providing clues for the mechanisms of biochar-assisted DEHP degradation in organic contaminated farmland soils.

Tackling municipal solid waste crisis in India: Insights into cutting-edge technologies and risk assessment

Municipal Solid Waste (MSW) management is a pressing global concern, with increasing interest in Waste-to-Energy Technologies (WTE-T) to divert waste from landfills. However, WTE-T adoption is hindered by financial uncertainties. The economic benefits of MSW treatment and energy generation must be balanced against environmental impact. Integrating cutting-edge technologies like Artificial Intelligence (AI) can enhance MSW management strategies and facilitate WTE-T adoption. This review paper explores waste classification, generation, and disposal methods, emphasizing public awareness to reduce waste. It discusses AI's role in waste management, including route optimization, waste composition forecasting, and process parameter optimization for energy generation. Various energy production techniques from MSW, such as high-solids anaerobic digestion, torrefaction, plasma pyrolysis, incineration, gasification, biodegradation, and hydrothermal carbonization, are examined for their advantages and challenges. The paper emphasizes risk assessment in MSW management, covering chemical, mechanical, biological, and health-related risks, aiming to identify and mitigate potential adverse effects. Electronic waste (E-waste) impact on human health and the environment is thoroughly discussed, highlighting the release of hazardous substances and their contribution to air, soil, and water pollution. The paper advocates for circular economy (CE) principles and waste-to-energy solutions to achieve sustainable waste management. It also addresses complexities and constraints faced by developing nations and proposes strategies to overcome them. In conclusion, this comprehensive review underscores the importance of risk assessment, the potential of AI and waste-to-energy solutions, and the need for sustainable waste management to safeguard public health and the environment.

Pre-emergence herbicides widely used in urban and farmland soils: fate, and potential human and environmental health risks

We determined the distribution, fate, and health hazards of dimethenamid-P, metazachlor, and pyroxasulfone, the effective pre-emergence herbicides widely used both in urban and agricultural settings globally. The rate-determining phase of sorption kinetics of these herbicides in five soils followed a pseudo-second-order model. Freundlich isotherm model indicated that the herbicides primarily partition into heterogeneous surface sites on clay minerals and organic matter (OM) and diffuse into soil micropores. Principal component analysis revealed that soil OM (R2, 0.47), sand (R2, 0.56), and Al oxides (R2, 0.33) positively correlated with the herbicide distribution coefficient (Kd), whereas clay (R2, ‒ 0.43), silt (R2, ‒ 0.51), Fe oxides (R2, ‒ 0.02), alkaline pH (R2, ‒ 0.57), and EC (R2, ‒ 0.03) showed a negative correlation with the Kd values. Decomposed OM rich in C=O and C-H functional groups enhanced herbicide sorption, while undecomposed/partially-decomposed OM facilitated desorption process. Also, the absence of hysteresis (H, 0.27‒0.88) indicated the enhanced propensity of herbicide desorption in soils. Leachability index (LIX, < 0.02-0.64) and groundwater ubiquity score (GUS, 0.02‒3.59) for the soils suggested low to moderate leaching potential of the herbicides to waterbodies, indicating their impact on water quality, nontarget organisms, and food safety. Hazard quotient and hazard index data for human adults and adolescents suggested that exposure to soils contaminated with herbicides via dermal contact, ingestion, and inhalation poses minimal to no non-carcinogenic risks. These insights can assist farmers in judicious use of herbicides and help the concerned regulatory authorities in monitoring the safety of human and environmental health.

Agroecological transition: towards a better understanding of the impact of ecology-based farming practices on soil microbial ecotoxicology

Alternative farming systems have developed since the beginning of industrial agriculture. Organic, biodynamic, conservation farming, agroecology and permaculture, all share a grounding in ecological concepts and a belief that farmers should work with nature rather than damage it. As ecology-based agricultures rely greatly on soil organisms to perform the functions necessary for agricultural production, it is thus important to evaluate the performance of these systems through the lens of soil organisms, especially soil microbes. They provide numerous services to plants, including growth promotion, nutrient supply, tolerance to environmental stresses and protection against pathogens. An overwhelming majority of studies confirm that ecology-based agricultures are beneficial for soil microorganisms. However, three practices were identified as posing potential ecotoxicological risks: the recycling of organic waste products, plastic mulching, and pest and disease management with biopesticides. The first two because they can be a source of contaminants; the third because of potential impacts on non-target microorganisms. Consequently, developing strategies to allow a safe recycling of the increasingly growing organic matter stocks produced in cities and factories, and the assessment of the ecotoxicological impact of biopesticides on non-target soil microorganisms, represent two challenges that ecology-based agricultural systems will have to face in the future.

An evaluation model for in-situ bioremediation technology of petroleum hydrocarbon contaminated soil

Considering the interference of the complexity of underground environment to the bioremediation scheme, an evaluation model for bioremediation technology in the soil source area of oil contaminated sites was established. On the basis of traditional CDE model, a compartment model was coupled to express the adsorption and degradation process, and the spatial expression of biodegradation was enriched through environment-dependent factors. The visualization of the model was achieved based on COMSOL Multiphysics software platform. Two sets of indoor sandbox experiments on natural attenuation and bioaugmentation were carried out for 120 days to verify the prediction function of the model. The results showed that bioaugmentation greatly improved the remediation effect. Petroleum hydrocarbons with different occurrence states exhibited different spatial distributions under the influence of environmental factors. The prediction accuracy evaluation results of total petroleum hydrocarbons, bio available hydrocarbons and non extractable hydrocarbons showed excellent fitting degree, and the model had a good prediction function for petroleum hydrocarbon in soil under different bioremediation scenarios. This model can be used to screen bioremediation technical schemes, prevent pollution and assess risk of petroleum hydrocarbon contaminated sites.

Using NH2-MIL-125(Ti) for efficient removal of Cr(VI) and RhB from aqueous solutions: Competitive and cooperative behavior in the binary system

The coexistence of inorganic and organic contaminants is a challenge for real-life water treatment applications. Therefore, in this research, we used NH2-MIL-125(Ti) to evaluate the single adsorption of hexavalent chromium (Cr(VI)) or Rhodamine B (RhB) in an aqueous solution and further investigate simultaneous adsorption experiments to compare the adsorption behavior changes. The main influencing factors, for example, reaction time, initial concentration, reaction temperature, and pH were studied in detail. In all reaction systems, the pseudo-second-order kinetic and Langmuir isotherm models were well illuminated the adsorption progress of Cr(VI) and RhB. Thermodynamic studies showed that the adsorption process was spontaneous and endothermic. As compared to the single system, the adsorption capacity of Cr(VI) in the binary system gradually decreased as the additive amount of RhB increased, whereas the adsorption capacity of RhB in the binary system was expanded brilliantly. When the binary reaction system contained 100 mg/L Cr(VI), the removal rate of RhB increased to 97.58%. The formation of Cr(VI)-RhB and Cr(III)-RhB complexes was the cause that provided facilitation for the adsorption of RhB. These findings prove that the interactions during the water treatment process between contaminants may obtain additional benefits, contributing to a better adsorption capacity of co-existing contaminant.

Hydrophobic organogel sorbent and its coated porous substrates for efficient oil/water emulsion separation and effective spilled oil remediation

Frequent offshore oil leakage accidents and large quantities of oily-wastewater produced in industry and daily life bring huge challenges to global water purification. The adaptability and stability of organogels as adsorbent materials have shown wide application prospects in the field of oil-water separation. Herein, the organogels displayed stable hydrophobic/lipophilic properties with high absorption ability (1200 wt./wt%), efficient sorption of multiple emulsions (>99.0%), and good reusability. More importantly, the organogels were successfully assembled with 2D/3D substrates to achieve excellent sorption capacity (102.5 g/g) and recycling performance (50 cycles). The gel-carbon black assembled on MS (GCB-MS) sorbent with excellent photothermal conversion performance, and can rapidly heat the surface to 70.4 °C under 1.0 sunlight radiation (1.0 kW/m2) and achieved an ultra-high sorption capacity of about 103 g/g for viscous crude oil. Meanwhile, the GCB-MS was combined with a pump to build continuous oil spill cleaning equipment to achieve a super-fast cleanup rate of 6.83 g/min. The developed hydrophobic organogels had been expanded unprecedentedly to realize the comprehensive treatment of oily-wastewater in complex environments, including layered oils, emulsions, and viscous crude oil spill, which provided an effective path for the comprehensive treatment of oily wastewater in complex environments.

Fate and transformation of uniformly 14C-ring-labeled bisphenol S in different aerobic soils

Bisphenol S (BPS), being structurally similar to bisphenol A (BPA), has been widely used as an alternative to BPA in industrial applications. However, in-depth studies on the environmental behavior and fate of BPS in various soils have been rarely reported. Here, 14C-labeled BPS was used to investigate its mineralization, bound residues (BRs) formation and extractable residues (ERs) in three soils for 64 days. Significant differences were found in the dissipation rates of BPS in three soils with different pH values. The dissipation of BPS followed pseudo first-order kinetics with half-lives (T1/2) of 15.2 ± 0.1 d, 27.0 ± 0.2 d, 180.4 ± 5.3 d, and 280.5 ± 3.3 d in the alkaline soil (fluvo-aquic soil, FS), the neutral soil (cinnamon soil, CS), the acidic soil (red soil, RS), and sterilized cinnamon soil (CS-S), respectively. The mineralization and BRs formation contributed the most to the dissipation of BPS in soil. BPS was persistent in acidic soil, and may pose a significant threat to plants grown in acidic soils. Additionally, soil microorganisms played a key role in BPS degradation, and the organic matter content might be a major factor that promotes the adsorption and degradation of BPS in soils. Two transformed products, P-hydroxybenzenesulfonic acid and methylated BPS were identified in soils. This study provides new insights into the fate of BPS in various soils, which will be useful for risk assessments of BPS in soil.

Alkali-thermal activated persulfate treatment of tetrabromobisphenol A in soil: Parameter optimization, mechanism, degradation pathway and toxicity evaluation

The continued accumulation of halogenated organic pollutants in soil posed a potential threat to ecosystems and human health. In this study, tetrabromobisphenol A (TBBPA) was used as a typical representative of halogenated organic pollutants in soil, for alkali-thermal activated persulfate (PS) treatment. The results of response surface methodology (RSM) showed a optimal debromination efficiency of TBBPA was 88.99 % under the optimum reaction conditions. Quenching experiments and electron paramagnetic resonance (EPR) confirmed that SO4-•, HO•, O2-• and 1O2 existed simultaneously in the oxidation process. SO4-• played a major role in the initial stage of the reaction, and O2-• played a major role in the the last stage. Based on density functional theory (DFT) and intermediate products, two degradation pathways were proposed, including debromination reaction and β bond scission. Moreover, the basic physical and chemical properties of the soil were affected to a certain extent, while the soil surface structure, elements and functional group composition rarely changed. In addition, the T.E.S.T. analysis and biotoxicity tests proved that alkali-thermal activated PS can effectively reduce the toxicity of TBBPA-contaminated soil, which is conducive to the subsequent safe secondary utilization of soil.

Features of the polycyclic aromatic hydrocarbon's spatial distribution in the soils of the Don River delta

PAHs are one of the most toxic organic compounds classes which is obligatory controlled all over the world. There is a luck of studies devoted to the PAHs levels and sources identification in the south of Russia. The features of the PAHs accumulation and spatial distribution in hydromorphic soils (Fluvisol) were studied on the example of the soils of the Don River delta floodplain landscapes. It has been shown that changes in the PAHs content in soils depended on the type and intensity of the emission source. A factor analysis and multivariate linear regression analysis were carried out to determine the features of the spatial distribution for individual PAH compounds, considering the properties of soils and typical differences in the emission source. The most polluted areas in the studied area located along the transit line of the long-distance tankers, where the content of the most toxic high molecular PAHs compounds reached 8862 ng g-1. As a result of regression analysis, a relationship was established between the PAHs accumulation rate with the content of silt (particles less than 0.001 mm in size) and Ca2+ and Mg2+ exchangeable cations in the soil (at p-level < 0.0001). Differences in individual PAH content for medium and heavy loamy Fluvisol and depend on the influence of different types of pollution sources.

The bioaccumulation and biotransformation of tetrabromobisphenol A bis (allyl ether) in common carp (Cyprinus carpio)

Tetrabromobisphenol A bis (allyl ether) (TBBPA-BAE) is an extensively used brominated flame retardant, which has raised considerable concern because of its neurotoxic and endocrine disruption effects on aquatic organisms. However, previous studies mainly focused on the parent compound before modification, tetrabromobisphenol A (TBBPA), and little information is available about the bioconcentration and biotransformation of TBBPA derivatives in fish. In this study, we investigated the tissue-specific uptake, elimination kinetic, and biotransformation of TBBPA-BAE in common carp (Cyprinus carpio). The fish were exposed to TBBPA-BAE at environmentally relevant concentrations (20 μg·L-1) for 28 days, followed by 14 days of depuration. The results showed TBBPA-BAE could rapidly accumulate in common carp. Among the seven tissues studied, the highest concentrations of TBBPA-BAE were observed in the liver (6.00 μg·g-1 wet weight [ww]) on day 24, while the longest residence time was observed in the kidney (t1/2 values of 18.7 days). Biotransformation of TBBPA-BAE was documented in the in vivo experiments, and 14 different phase I and phase II metabolites were identified in the liver. These findings suggest the biotransformation products of TBBPA-BAE should be considered for a comprehensive risk evaluation.

Techno-economic analysis of phytoremediation: A strategic rethinking

Phytoremediation is a cost-effective and environmentally sound approach, which uses plants to immobilize/stabilize, extract, decay, or lessen toxicity and contaminants. Despite successful evidence of field application, such as natural attenuations, and self-purification, the main barriers remain from a "promising" to a "commercial" approach. Therefore, the ultimate goal of this paper is to examine factors that contribute to phytoremediation's underutilization and discuss the real costs of phytoremediation when the time and land values are considered. We revisit mechanisms and processes of phytoremediation. We synthesize existing information and understanding based on previous works done on phytoremediation and its applications to provide the technical assessment and perspective views in the commercial acceptance of phytoremediation. The results show that phytoremediation is the most suitable for remote regions with low land values. Since these regions allow a longer period to be restored, land vegetation covers can be established in more or less time like natural attenuation. Since the length of phytoremediation is an inherent limitation, this inherent disadvantage limits its adoption in developed business regions, such as growing urban areas. Because high land values could not be recovered in the short term, phytoremediation is not cost-effective in those regions. We examine the potential measures that can enhance the performance of phytoremediation, such as soil amendments, and agricultural practices. The results obtained through review can clarify where/what conditions phytoremediation can provide the most suitable solutions at a large scale. Finally, we identify the main barriers and knowledge gaps to establishing a vegetation cover in large-scale applications and highlight the research priorities for increased acceptance of phytoremediation.

Effect of electric fields strength on soil factors and microorganisms during electro-bioremediation of benzo[a]pyrene-contaminated soil

Electro-bioremediation is a promising technology for remediating soils contaminated with polycyclic aromatic hydrocarbons (PAHs). However, the resulting electrokinetic effects and electrochemical reactions may inevitably cause changes in soil factors and microorganism, thereby reducing the remediation efficiency. To avoid negative effect of electric field on soil and microbes and maximize microbial degradability, it is necessary to select a suitable electric field. In this study, artificial benzo [a]pyrene (BaP)-contaminated soil was selected as the object of remediation. Changes in soil factors and microorganisms were investigated under the voltage of 1.0, 2.0, and 2.5 V cm-1 using chemical analysis, real-time PCR, and high-throughput sequencing. The results revealed noticeable changes in soil factors (pH, moisture, electrical conductivity [EC], and BaP concentration) and microbes (PAHs ring-hydroxylating dioxygenase [PAHs-RHDα] gene and bacterial community) after the application of electric field. The degree of change was related to the electric field strength, with a suitable strength being more conducive to BaP removal. At 70 d, the highest mean extent of BaP removal and PAHs-RHDα gene copies were observed in EK2.0 + BIO, reaching 3.37 and 109.62 times those in BIO, respectively, indicating that the voltage of 2.0 V cm-1 was the most suitable for soil microbial growth and metabolism. Changes in soil factors caused by electric fields can affect microbial activity and community composition. Redundancy analysis revealed that soil pH and moisture had the most significant effects on microbial community composition (P < 0.05). The purpose of this study was to determine the appropriate electric field that could be used for electro-bioremediation of PAH-contaminated soil by evaluating the effects of electric fields on soil factors and microbial communities. This study also provides a reference for efficiency enhancement and successful application of electro-bioremediation of soil contaminated with PAHs.

Improved sea rice yield and accelerated di-2-ethylhexyl phthalate (DEHP) degradation by straw carbonization returning in coastal saline soils

Di-2-ethylhexyl phthalate, a persistent organic contaminant, is widely distributed in the environment and poses substantial threats to human health; however, there have been few investigations regarding the risks and remediation of DEHP in coastal saline soils. In this work, we studied the influences of straw carbonization returning on sea rice yield and DEHP degradation. Straw carbonization returning significantly increased soil nutrients and reduced salt stress to improve sea rice yield. DEHP degradation efficiency was enhanced to a maximum of 78.27% in straw carbonized return with 60% sea rice, mainly attributed to the high pH value, high soil organic matter and enriched potential DEHP degraders of Nocardioides, Mycobacterium and Bradyrhizobium. Some key genes related to metabolism (esterase and cytochrome P450) and DEHP-degradation (pht4, pht5, pcaG, dmpB, catA and fadA) were elevated and explained the accelerated DEHP degradation, shifting from the benzoic acid pathway to the protocatechuate pathway in straw carbonization returning. The results obtained in this study provide a deep and comprehensive understanding of sea rice yield improvement and DEHP degradation mechanisms in coastal paddy soil by a straw carbonization returning strategy.

Linking drivers of plant per- and polyfluoroalkyl substance (PFAS) uptake to agricultural land management decisions

Widespread contamination of the per- and polyfluoroalkyl substance (PFAS) in agricultural areas is largely attributed to the application of sewage sludge in which the PFAS can be concentrated. This creates a pathway for these contaminants to enter the food chain and, by extension, causes human health and economic concerns. One barrier to managing land with PFAS contamination is the variation in reported plant uptake levels across studies. A review of the literature suggests that the variation in plant uptake is influenced by a host of factors including the composition of PFAS chemicals, soil conditions, and plant physiology. Factors include (1) the chemical components of the PFAS such as the end group and chain length; (2) drivers of soil sorption such as the presence of soil organic matter (SOM), multivalent cation concentration, pH, soil type, and micropore volume; and (3) crop physiological features such as fine root area, percentage of mature roots, and leaf blade area. The wide range of driving factors highlights a need for research to elucidate these mechanisms through additional experiments as well as collect more data to support refined models capable of predicting PFAS uptake in a range of cropping systems. A conceptual framework presented here links drivers of plant PFAS uptake found in the literature to phytomanagement approaches such as modified agriculture or phytoremediation to provide decision support to land managers.

Aging affects isomer-specific occurrence of dechlorane plus in soil profiles: A case study in a geographically isolated landfill from the Tibetan Plateau

Two major structural isomers in commercial dechlorane plus (DP) mixtures, anti-DP and syn-DP, generally displayed varied desorption and partitioning efficiencies in soils, which may be linked to their different aging rates. However, the molecular parameters that govern the degree of aging and its associated effects on the occurrence of DP isomers have not been comprehensively investigated. In this study, the relative abundance of rapid desorption concentration (R_rapid) was measured for anti-DP, syn-DP, anti-Cl₁₁-DP, anti-Cl₁₀-DP, Dechlorane-604 (Dec-604), and Dechlorane-602 (Dec-602) at a geographically isolated landfill area in the Tibetan Plateau. The R_rapid values were used as an indicator of aging degree, exhibiting a close correlation with the three-dimension conformation of the molecules for the dechlorane series compounds. This observation suggested that planar molecules may have a greater tendency to accumulate in the condensed phase of organic matter and undergo more rapid aging. The fractional abundances and dechlorinated products of anti-DP were found to be predominantly controlled by the aging degree of DP isomers. The multiple nonlinear regression model indicated that differences in aging between anti-CP and syn-DP were primarily driven by the total desorption concentration and soil organic matter content. Aging plays a significant role in both the transport processes and metabolism of DP isomers and should be taken into account to refine the assessment of their environmental behaviors.