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Gas stations not only serve as sites for oil storage and refueling but also as locations where vehicles frequently brake, significantly enriching the surrounding soil with potentially toxic elements (PTEs). Herein, 117 topsoil samples from gas stations were collected in Beijing to explore the impact of gas stations on PTE accumulation. The analysis revealed that the average Pollution Index (PI) values for Cd, Hg, Pb, Cu, and Zn in the soil samples all exceeded 1. The random forest (RF) model, achieving an AUC score of 0.95, was employed to predict PTE pollution at 372 unsampled gas stations. Additionally, a Positive Matrix Factorization (PMF) model indicated that gas station operations and vehicle emissions were responsible for 70 % of the lead (Pb) enrichment. Probabilistic health risk assessments showed that the carcinogenic risk (CR) and noncarcinogenic risk (NCR) for PTE pollution to adult females were the highest, at 0.451 and 1.61E-05 respectively, but still within acceptable levels. For adult males at contaminated sites, the Pb-associated CR and NCR were approximately twice as high as those at uncontaminated sites, with increases of 107 % and 81 %, respectively. This study provides new insights for managing pollution caused by gas stations. [Display omitted] • Cd, Pb, Hg, Cu and Zn were significantly enriched in gas station soils. • RF model performs well in predicting PTE pollution at unsampled gas stations. • High Pb enrichment originates from refueling activities and traffic emissions. • Health risks associated with PTEs can be precisely assessed using 2-D MCS. [ABSTRACT FROM AUTHOR]

Organophosphate esters (OPEs) pose hazards to both humans and the environment. This study applied target screening to analyze the concentrations and detection frequencies of OPEs in the soil and groundwater of representative contaminated sites in the Pearl River Delta. The clusters and correlation characteristics of OPEs in soil and groundwater were calculated by self-organizing map (SOM). The risk assessment and partitions of OPEs in industrial park soil and groundwater were conducted. The results revealed that 14 out of 23 types of OPEs were detected. The total concentrations (Σ 23 OPEs) ranged from 1.931 to 743.571 ng/L in the groundwater, and 0.218 to 79.578 ng/g in the soil, the former showed highly soluble OPEs with high detection frequencies and concentrations, whereas the latter exhibited the opposite trend. SOM analysis revealed that the distribution of OPEs in the soil differed significantly from that in the groundwater. In the industrial park, OPEs posed acceptable risks in both the soil and groundwater. The soil could be categorized into Zone I and II, and the groundwater into Zone I, II, and III, with corresponding management recommendations. Applying SOM to analyze the characteristics and partitions of OPEs may provide references for other new pollutants and contaminated sites. [Display omitted] • OPEs' partitions and correlation of soil and groundwater explored by machine learning. • OPEs' properties mainly cause their different characteristics in soil and groundwater. • Differentiated management for soil and groundwater was devised by machine learning. • The partition ideas may provide references for other new pollutants and sites. [ABSTRACT FROM AUTHOR]

The coupling of thermal remediation with microbial reductive dechlorination (MRD) has shown promising potential for the cleanup of chlorinated solvent contaminated sites. In this study, thermal treatment and bioaugmentation were applied in series, where prior higher thermal remediation temperature led to improved TCE dechlorination performance with both better organohalide-respiring bacteria (OHRB) colonization and electron donor availability. The 60 °C was found to be a key temperature point where the promotion effect became obvious. Amplicon sequencing and co-occurrence network analysis demonstrated that temperature was a more dominating factor than bioaugmentation that impacted microbial community structure. Higher temperature of prior thermal treatment resulted in the decrease of richness, diversity of indigenous microbial communities, and simplified the network structure, which benefited the build-up of newcoming microorganisms during bioaugmentation. Thus, the abundance of Desulfitobacterium increased from 0.11 % (25 °C) to 3.10 % (90 °C). Meanwhile, released volatile fatty acids (VFAs) during thermal remediation functioned as electron donors and boosted MRD. Our results provided temperature-specific information on synergistic effect of sequential thermal remediation and bioaugmentation, which contributed to better implementation of the coupled technologies in chloroethene-impacted sites. [Display omitted] • Microbial reductive dechlorination (MRD) benefited from prior thermal treatment. • Higher temperature promoted following bioaugmented MRD performance. • Desulfitobacterium abundance increased from 0.11 % (25 °C) to 3.10 % (90 °C). • Higher temperature facilitated positive interspecies interactions. • Indigenous released VFAs at 90 °C was 7.70 times of that at 75 °C after heating. [ABSTRACT FROM AUTHOR]

Bioremediation of cadmium (Cd) pollution, a recognized low-carbon green environmental protection technology, is significantly enhanced by the discovery of Cd-tolerant microorganisms and their underlying tolerance mechanisms. This study presents Colpoda sp., a soil ciliate with widespread distribution, as a novel bioindicator and bioremediator for Cd contamination. With a 24 h- LC 50 of 5.39 mg l−1 and an IC 50 of 24.85 μg l−1 in Cd-contaminated water, Colpoda sp. achieves a maximum bioaccumulation factor (BAF) of 3.58 and a Cd removal rate of 32.98 ± 0.74 % within 96 h. The toxic responses of Colpoda sp. to Cd stress were assessed through cytological observation with transmission electron microscopy (TEM), oxidative stress kinase activity, and analysis of Cd-metallothionein (Cd-MTs) and the cd-mt gene via qRT-PCR. The integrated biomarker response index version 2 (IBRv2) and structural equation models (SEM) were utilized to analyze key factors and mechanisms, revealing that the up-regulation of Cd-MTs and cd-mt expression, rather than the oxidative stress system, is the primary determinant of Cd accumulation and tolerance in Colpoda sp. The ciliate's ability to maintain growth under 24.85 μg l−1 Cd stress and its capacity to absorb and accumulate Cd particles from water into cells are pivotal for bioremediation. A new mathematical formula and regression equations based on Colpoda sp.'s response parameters have been established to evaluate environmental Cd removal levels and design remediation schemes for contaminated sites. These findings provide a novel bioremediation and monitoring pathway for Cd remobilization and accumulation in soil and water, potentially revolutionizing the governance of Cd pollution. [Display omitted] • Colpoda sp. becomes a new bioindicator and bioremediator for Cd pollution. • Accumulation and tolerance in Colpoda sp. depend on Cd-MTs and cd-mt. • A mathematic model is supplied for Cd assessment and removal based on Colpoda sp. [ABSTRACT FROM AUTHOR]

1,2-Dichloroethane (1,2-DCA), a widely utilized chemical intermediate and organic solvent in industry, frequently enters the environment due to accidental leaks and mishandling during application processes. Thus, the in-situ remediation of contaminated sites has become increasingly urgent. However, traditional remediation methods are inefficient and costly, while bioremediation presents a green, efficient, and non-secondary polluting alternative. In this study, an engineered strain capable of completely degrading 1,2-DCA was constructed. We introduced six exogenous genes of the 1,2-DCA degradation pathway into E. coli and confirmed their normal transcription and efficient expression in this engineered strain through qRT-PCR and proteomics. The degradation experiments showed that the strain completely degraded 2 mM 1,2-DCA within 12 h. Furthermore, the results of isotope tracing verified that the final degradation product, malic acid, entered the tricarboxylic acid cycle (TCA) of E. coli and was ultimately fully metabolized. Also, morphological changes in the engineered strain and control strain exposed to 1,2-DCA were observed under SEM, and the results revealed that the engineered strain is more tolerant to 1,2-DCA than the control strain. In conclusion, this study paved a new way for humanity to deal with the increasingly complex environmental challenges. [Display omitted] • The complete 1,2-dichloroethane degradation pathway was assembled into one vector. • The vector was introduced into the model strain of Escherichia coli. • Engineered bacteria could completely degrade 1,2-dichloroethane. • The integrity of the degradation pathway was verified by isotope tracing method. [ABSTRACT FROM AUTHOR]

The membrane interface probe (MIP) is an efficient and economical in-situ tool for chlorinated hydrocarbon (CH) contaminated site investigation. Given that the interpretation of MIP test is currently limited to a qualitative level, a theoretical model considering multiphase flow and multifield coupling is firstly proposed to simulate MIP test process. This model can consider phase change, membrane effect, adsorption and dissolution of the CH liquid, gas diffusion, and evaporation. Then, the model is used to study the changes in soil temperature and soil CH concentration during MIP test, as well as the influences of soil CH concentration and soil properties (initial water saturation, soil intrinsic permeability, and thermal properties) on MIP response. Finally, a simplified MIP interpretation model is developed based on parametric analysis results and verified against field and laboratory test data. It is found that the soil CH concentration, rather than soil properties, dominates the MIP response. The simplified interpretation model can deliver practical prediction of the CH concentration through the detected results by MIP, which may improve the applicability of MIP. [Display omitted] • A theoretical model is developed to reveal the MIP test mechanism. • MIP test process can be effectively divided into three stages. • Soil CH concentration, rather than soil properties, dominates the MIP response. • A simplified model is proposed to predict CH concentration directly by MIP. • The simplified model may improve the applicability of MIP. [ABSTRACT FROM AUTHOR]

Several studies conducted at industrial sites have documented the infiltration of dense non-aqueous phase liquids (DNAPLs) into clay layers, a phenomenon potentially influenced by the coexistence of chemicals like surfactants in some common pollutants. Bentonite (Ben), monochlorobenzene (MCB), and Tween 80 (T80) were selected as reference components to investigate the influences of nonionic surfactants on DNAPLs migration in clays. Results showed that T80 promotes MCB dissolution and encourages MCB adsorption on Ben. This process reduces the hydrophilicity of Ben, resulting in water loss and shrinkage, which creates cracks and facilitates the migration of MCB within the clay. Tw80 notably enhances MCB solubility, as indicated by a molar solubilization ratio of 7.80. The MCB adsorption on Ben (Q MCB) displays a linear increase with raising the T80 adsorption on Ben (Q T80), especially when Q T80 are below the thresholds, e.g., 408.4 mg/g at pH 3 and 339.3 mg/g at pH 7; however, Q MCB is decreased with increasing adsorbed T80 further. The average fracture ratio, crack length, and crack width of cracked samples in the cracking experiments were 0.794%, 11.29 mm, and 0.209 mm, respectively. The findings here contribute to understanding the role of surfactants in VOC transport in contaminated sites. [Display omitted] • Tween 80 and MCB mutually enhance their adsorption onto bentonite. • Dissolved and adsorbed T80 has a competitive effect on MCB adsorption. • Upon Tween 80 or MCB adsorption, the hydrophilicity of bentonite is reduced. • Tween 80 induce cracks in bentonite to facilitate the migration of MCB. [ABSTRACT FROM AUTHOR]

Rania-Khan Chandpur site, (Kanpur Dehat, Uttar Pradesh, India), one of the highly Chromium (Cr) contaminated sites in India due to Chromite Ore Processing Residue (COPR), has been investigated at the field-scale. We found that the area around the COPR dumps was hazardously contaminated with the Cr where its concentrations in the surface water and groundwater were > 40 mgL-1, its maximum contents in the COPRs and in the soils of the adjoining lands were 9.6 wt% and 3.83 wt%, respectively. By exploring the vegetation and microbial distribution across the site, we advocate the appropriateness of Cynodon dactylon , Chrysopogon zizanioides , Cyperus sp., and Typha angustifolia as the most suitable phytoremediation agent because their association with Cr remediating bacterial species (Pseudomonas sp. , Clostridium sp. and Bacillus sp.) was strong. Using this remarkable information for the bioremediation projects, this site can be re-vegetated and bioaugmented to remediate Cr in soils, waterlogged ditches, surface water, and in groundwater systems. [Display omitted] • A globally known COPR contaminated site was investigated at the field-scale. • Soil-water systems impacted by the hazardous chromium have been studied. • Only a few plant species can grow in Cr contaminated zone or near COPR sites. • Cr content (up to 9.6 wt%) in soils was one of the key drivers of microbiome. • Selected native plants and microbes can improve soil-water quality at COPR sites. [ABSTRACT FROM AUTHOR]

Nitrogen fertilizer supports global food production, but its manufacturing results in substantial ammonia nitrogen (AN) contaminated sites which remain largely unexplored. In this study, ten representative AN contaminated sites were investigated, covering a wide range of subsurface pH, temperature, and AN concentration. A total of 7232 soil samples and 392 groundwater samples were collected to determine the concentration levels, migration patterns, and accurate health risks of AN. The results indicated that AN concentrations in soil and groundwater reached 12700 mg/kg and 12600 mg/L, respectively. AN concentrations were higher in production areas than in non-production areas, and tended to migrate downward from surface to deeper soil. Conventional risk assessment based on AN concentration identified seven out of the ten sites presenting unacceptable risks, with remediation costs and CO 2 emissions amounting to $1.67 million and 17553.7 tons, respectively. A novel risk assessment model was developed, which calculated risks based on multiplying AN concentration by a coefficient f NH3 (the ratio of NH 3 to AN concentration). The mean f NH3 values, primarily affected by subsurface pH, varied between 0.02 and 0.25 across the ten sites. This new model suggested all investigated sites posed acceptable health risks related to AN exposure, leading to their redevelopment without AN-specific remediation. This research offers a thorough insight into AN contaminated site, holds great realistic significance in alleviating global economic and climate pressures, and highlights the need for future research on refined health risk assessments for more contaminants. [Display omitted] • Ammonia nitrogen (AN) contaminated sites were comprehensively investigated. • AN accumulate in historical production area and transport downward. • A refined risk assessment for AN contaminated sites were developed. • Simply measuring subsurface pH reduce considerable cost and CO2 emission. • The ten sites can be redeveloped without remediation in terms of AN health risk. [ABSTRACT FROM AUTHOR]

Microbe-mediated anaerobic degradation is a practical method for remediation of the hazardous monoaromatic hydrocarbons (BTEX, including benzene, toluene, ethylbenzene and xylenes) under electron-deficient contaminated sites. However, how do the anaerobic functional microbes adapt to oxygen exposure and flexibly catabolize BTEX remain poorly understood. We investigated the switches of substrate spectrum and bacterial community upon oxygen perturbation in a nitrate-amended anaerobic toluene-degrading microbiota which was dominated by Aromatoleum species. DNA-stable isotope probing demonstrated that Aromatoleum species was involved in anaerobic mineralization of toluene. Metagenome-assembled genome of Aromatoleum species harbored both the nirBD -type genes for nitrate reduction to ammonium coupled with toluene oxidation and the additional meta- cleavage pathway for aerobic benzene catabolism. Once the anaerobic microbiota was fully exposed to oxygen and benzene, 1.05 ± 0.06% of Diaphorobacter species rapidly replaced Aromatoleum species and flourished to 96.72 ± 0.01%. Diaphorobacter sp. ZM was isolated, which was not only able to utilize benzene as the sole carbon source for aerobic growth and but also innovatively reduce nitrate to ammonium with citrate/lactate/glucose as the carbon source under anaerobic conditions. This study expands our understanding of the adaptive mechanism of microbiota for environmental redox disturbance and provides theoretical guidance for the bioremediation of BTEX-contaminated sites. [Display omitted] • A microbiota flexible for monoaromatic hydrocarbons degradation was obtained. • Aromatoleum sp. MAG1 was identified as the anaerobic toluene degrader. • Genus Aromatoleum harbored nirBD -type gene for nitrate reduction to ammonium. • Diaphorobacter sp. ZM was isolated as an aerobic benzene degrader. • Diaphorobacter sp. ZM reduced nitrate under anaerobic conditions via DNRA. [ABSTRACT FROM AUTHOR]

A novel soil-bentonite backfill is proposed for use in vertical cutoff walls to contain phenol in groundwater at contaminated sites. The backfill consists of sand and bentonite modified with tetramethylammonium and carboxymethylcellulose, labeled as STCMB backfill. Flexible-wall permeability and double-reservoir diffusion tests were conducted to investigate the impact of phenol solution on hydraulic conductivity (k), effective diffusion coefficient (D *) and partition coefficient (K p) of the backfill, respectively. The permeability results showed k of the STCMB backfill decreased by 0.91 times when the permeating liquid was changed from tap water to phenol solution. The diffusion testing results showed that D * values for the STCMB and conventional backfill (labeled as SCB backfill) were 4.0 × 10−10 m2/s and 3.0 × 10−10 m2/s, respectively, whereas K p values for the STCMB and SCB backfills were 2.0 mL/g and 0.75 mL/g, respectively. The octanol-water partition coefficient model is suitable for estimating K p for nonpolar organics. Furthermore, a series of solute transport simulations using Pollute V7 program was performed to evaluate the performance of vertical cutoff walls comprising STCMB and SCB backfills in containing phenol in lateral flowing groundwater. Overall, the STCMB backfill has demonstrated superior effectiveness in containing phenol in groundwater. [Display omitted] • We first time propose a newly modified bentonite and backfill for containing phenol. • New backfill exhibits satisfactory hydraulic conductivity to phenol solution. • K P of proposed backfill increases by 2.7 times as compared to conventional backfill. • K ow is more suitable for estimating K p with respect to nonpolar organics. • New backfill cutoff wall is very effective in containing phenol in groundwater. [ABSTRACT FROM AUTHOR]

Under the background of the Coronavirus Disease 2019 (COVID-19) pandemic, research on pathogens deserves greater attention in the natural environment, especially in the widely distributed contaminated sites with complicated and severe organic pollution. In this study, the community composition and assembly of soil pathogens identified by the newly-developed 16S-based pipeline of multiple bacterial pathogen detection (MBPD) have been investigated on spatiotemporal scales in the selected organic polluted site. We demonstrated that the richness and diversity of the pathogenic communities were primarily controlled by soil depth, while the structure and composition of pathogenic communities varied pronouncedly with seasonal changes, which were driven by the alterations in both physiochemical parameters and organic contaminants over time. Network analysis revealed that the overwhelmingly positive interactions, identified multiple keystone species, and a well-organized modular structure maintained the stability and functionality of the pathogenic communities under environmental pressures. Additionally, the null-model analysis showed that deterministic processes dominated the pathogenic community assembly across soil profiles. In three seasons, stochasticity-dominated processes in spring and summer changed into determinism-dominated processes in winter. These findings extend our knowledge of the response of the bacterial pathogenic community to environmental disruptions brought on by organic contaminated sites. [Display omitted] • Bacterial pathogenic communities were investigated in the organic polluted site. • α- and β-diversities were mainly impacted by soil depths and seasons, respectively. • Taxa partnerships and a high modularity kept structural and functional stability. • Deterministic processes dominated the community assembly across soil profiles. • Stochasticity-driven shifted to determinism-driven processes with seasonal changes. [ABSTRACT FROM AUTHOR]

Many non-ferrous metal mining and smelting activities have caused severe metal(loid) contamination in the local soil environment. The metabolic activity of soil microorganisms in four areas affected by different metallurgical activities (production vs. waste disposal) was characterized using a contamination gradient from the contaminated site to the surrounding soils. Results indicated that the soil microcalorimetric and enzyme activities were correlated with the fractionated metal(loid) properties (p < 0.05). All four areas had high total As, Cd, Pb, Sb, and Zn concentrations, of which mobile As, Cu, Ni, Pb, Sb, and Zn were higher in the contaminated sites than the surrounding sites, reflecting an elevated environmental risk. Three contaminated site areas had lower microbial activities than their surrounding sites suggesting that high metal(loid) concentrations inhibited soil microbial communities. Interestingly, the fourth area (tailing pond) showed an opposite trend (i.e., increased microbial activity in contaminated vs. surrounding areas). The microbial thermodynamic parameters of this contaminated site were higher than its surrounding sites, suggesting that the selected microbial communities can develop a functional resistance to metal(loid)s stress. This study provides a theoretical basis for ecological prevention and control of metal-polluted areas. [Display omitted] • Soils impacted by nonferrous metal production were barren and heterogeneous. • Polluted areas had higher levels of bioavailable metal(loid)s than surroundings. • Microbial enzyme activities were lower in source soils compared to surroundings. • Microbial metabolic activity was correlated to metal(loid) concentrations. • Enzyme activities and thermodynamic parameters are sensitive microbial indicators. [ABSTRACT FROM AUTHOR]

• Sulfolane degrading aerobic granules were successfully developed. • Coaggregation prevailed acclimatization in forming target-specific aerobic granules. • Diverse bacterial families can co-exist in the developed aerobic granules. • Aerobic granules showed strong stability in various environmental conditions. Aerobic granulation is regarded as the future technology for wastewater treatment that can replace conventional activated sludge. In this study, two approaches of forming sulfolane degrading aerobic granules (SDAG) were successfully developed and evaluated. These include adaptation of pre-grown granules to sulfolane environment and coaggregation of pre-grown granules with bacterial culture native to sulfolane contaminated site. The adaption method required a longer period to form robust SDAG compared to coaggregation method where degradation of sulfolane was observed within 24 h. Electronic images revealed dominant filamentous bacteria on the surface of granules while DNA analysis unveiled the complexity of the dynamic change of microbial community during aerobic granule formation. The rate of sulfolane degradation by coaggregated granules reduced as the concentration of carbon source increased, nevertheless, the rate increased with increased biomass. In addition, the presence of co-contaminants can slightly impact the ability of newly cultivated granules to degrade sulfolane. Finally, the stability and settleability of the new aerobic granules was investigated under different environmental conditions. About 30% of the aerobic granules were lost after 14 d of operation without any continuous supply of carbon sources. The surviving SDAGs continued to display an intact structure coupled with good settleability. [ABSTRACT FROM AUTHOR]

• legacy mercury in upper Berry's Creek has a δ202Hg value of −0.29‰. • organic matter content was used to identify a low δ202Hg pool of mercury that dilutes legacy contaminant mercury. • upper Berry's Creek contributes 21%–82% of mercury to the Hackensack River estuary. • legacy mercury may affect marsh habitats far from sites of primary contamination. Spatial redistribution of legacy mercury (Hg) contamination in the Hackensack River estuary (New Jersey, USA) was evaluated using mercury stable isotopes. Total Hg varied from 0.06 to 3.8 μg g−1 in sediment from the tidal Hackensack River and from 15 to 154 μg g−1 near historically contaminated sites in upper Berry's Creek, a tributary of the Hackensack River. δ202Hg values for total Hg from Berry's Creek and Hackensack River estuaries varied over a fairly narrow range (−0.44‰ to −0.21‰), but were highest for sediment from upper Berry's Creek. Isotope mixing plots show that residual legacy mercury from upper Berry's Creek is partially diluted by a low concentration and low δ202Hg pool of mercury associated with low organic matter content sediments similar to those in Newark Bay. Based on an isotope mixing model, we estimate that upper Berry's Creek contributes 21%–82% of the mercury in sediments in the Hackensack River estuary and its tidal tributaries, including upstream marsh habitats far from the primary source. Our results show that mercury stable isotopes can be used to track the redistribution of mercury in tidal ecosystems and highlight the potentially large areas which may be affected by legacy mercury contamination in estuaries. [ABSTRACT FROM AUTHOR]

Chlorinated aliphatic hydrocarbons (CAHs) are potentially toxic substances that have been detected in various contaminated environments. Biological elimination is the main technique of detoxifying CAHs in the contaminated sites, but the soil bacterial community at CAH-contaminated sites have been little investigated. Here, high-throughput sequencing analysis of soil samples from different depths (to 6 m depth) at an aged CAH-contaminated site has been conducted to investigate the community composition, function, and assembly of soil bacteria. The alpha diversity of the bacterial community significantly increased with increasing depth and bacterial community also became more convergent with increasing depth. Organohalide-respiring bacteria (OHRB) is considered keystone taxa to reduce the environmental stress of CAHs by reductive dechlorinate CAHs into nontoxic products, increases the alpha diversity of bacterial community and improves the stability of bacterial co-occurrence network. The high concentration of CAHs in deep soil and the stable anaerobic environment make deterministic processes dominate bacterial community assembly, while the topsoil is dominated by dispersal limitation. In general, CAHs at contaminated sites have a great impact on bacterial community, but the CAHs metabolic community acclimated in deep soil can reduce the environmental stress of CAHs, which provides foundation for the monitored natural attenuation technology in CAHs-contaminated sites. [Display omitted] • Alpha-diversity increased with increasing depth at aged CAHs-contaminated site. • Obligate organohalide respiration played a vital role in bacterial community function. • The complexity and stability of bacterial co-occurrence network increased with increasing depth. • Deterministic processes gradually dominated bacterial community assembly with increasing depth. [ABSTRACT FROM AUTHOR]

Despite recent attention being paid to the biodegradation of petroleum hydrocarbons in cold environments, scale-up studies of biodegradation are lacking. Herein, the effect of scale-up on the enzymatic biodegradation of highly contaminated soil at low temperatures was studied. A novel cold-adapted bacteria (Arthrobacter sp. S2TR-06) was isolated that could produce cold-active degradative enzymes (xylene monooxygenase (XMO) and catechol 2,3-dioxygenase (C2,3D)). Enzyme production was investigated on 4 different scales (lab to pilot scale). The results showed a shorter fermentation time, and the highest production of enzymes and biomass (107 g/L for biomass, 109 U/mL, and 203 U/mL for XMO and C2,3D after 24 h) was achieved in the 150-L bioreactor due to enhanced oxygenation. Multi-pulse injection of p-xylene into the production medium was needed every 6 h. The stability of membrane-bound enzymes can be increased up to 3-fold by adding FeSO 4 at 0.1% (w/v) before extraction. Soil tests also showed that biodegradation is scale-dependent. The maximum biodegradation rate decreased from 100% at lab-scale to 36% in the 300-L sand tank tests due to limited access of enzymes to trapped p-xylene in soil pores, low dissolved oxygen in the water-saturated zone, soil heterogeneity, and the presence of the free phase of p-xylene. The result demonstrated that formulation of enzyme mixture with FeSO 4 and direct injection of enzyme mixture (third scenario) can increase the efficiency of bioremediation in heterogeneous soil. In this study, it was demonstrated that cold-active degradative enzyme production can be scaled up to an industrial scale and enzymatic treatment can be used to effectively bioremediate p-xylene contaminated sites. This study could provide key scale-up guidance for the enzymatic bioremediation of mono-aromatic pollutants in water-saturated soil under cold conditions. [Display omitted] • Arthrobacter sp. produces cold-active oxidative enzymes for p-xylene biodegradation. • Multi-pulse addition of p-xylene is needed for the higher enzymes production. • Pilot scale fermenters increase fermentation efficiency under optimal conditions. • 3D soil tank helps understand the factors involved in contaminated sites. • Enzymatic biodegradation is potentially a viable and cost-effective remedial option. [ABSTRACT FROM AUTHOR]

Accurate quantification of arsenic migration and accumulation in brownfield site is critical for environmental management and soil remediation. However, the researches simulating arsenic in brownfield site in China are limited due to sparse data and complex migration behaviors. In this study, we simulated historic arsenic contamination using Hydrus-3D in an abandoned brownfield site in Hebei, China, from 1972 to 2019. Atmospheric discharge, wastewater leakage, solid waste discharge and tank leakage were calculated according to the factory processes for model simulation. Based on the results of Hydrus-3D, we assessed health risk of arsenic in this site. The results showed that total arsenic input to the soil surface from 4 pathways was 24.6 tons, the solid waste discharge was the highest contributor. The accumulation process mainly occurred in the unsaturated zone due to clay and silty clay absorbed arsenic and thus slow down the migration process. While in the saturation zone, abundant groundwater promoted migration of arsenic, resulting in widespread distribution of contaminated area. The model results represented good performance between simulated and measured values. Sensitivity analysis indicated that adsorption constant and water conductivity were the most influential parameters. Heath risk assessment showed that arsenic contamination continues to threaten resident health. [Display omitted] • 58-years migration and accumulation of arsenic in site was simulated by Hydrus-3D. • Solid waste emission pathway contributed most arsenic in studied brownfield site. • Clay absorption and waterflow were the main factors affecting arsenic migration. • Risk assessment indicated that arsenic continues to threaten human health. • Our study provides a scope for contaminated site assessment and soil remediation. [ABSTRACT FROM AUTHOR]

Submarine Groundwater Discharge (SGD) is recognized as a relevant source of pollutants to the sea, but little is known about its relevance as a source of chemicals of emerging concern (CECs). Here, both the presence and distribution of a wide range of CECs have been evaluated in the most comprehensive manner to date, in a well-characterized Mediterranean coastal aquifer near Barcelona (Spain). Samples from coastal groundwater and seawater allowed for the unique spatial characterization of the pollutants present in the land-ocean interface, an outstanding research gap that required attention. The main goals were (1) to determine CECs in the aquifer, so as to evaluate the SGD as a relevant source of marine pollution, and (2) to identify new tracers to improve our understanding of SGD dynamics. To this end, 92 CECs were located in the aquifer by using wide-scope analytical target methodologies (>2000 chemicals). Among them, the perfluoroalkyl and polyfluoroalkyl substances (PFAS), along with the pharmaceuticals carbamazepine and topiramate, were revealed to be good markers for tracing anthropogenic contamination in ground- and seawater, in concrete situations (e.g., highly contaminated sites). Additionally, non-target analysis expanded the number of potential tracers, making it a promising tool for identifying both the source and the fate of pollutants. [Display omitted] • Submarine groundwater discharge was evaluated as a source of sea contamination. • 92 chemicals of emerging concern (CECs) were detected in coastal aquifer. • Unique spatial characterization of the CECs present in the land-ocean interface. • 6 PFAS and 2 pharmaceuticals revealed to be tracers of contamination in groundwater. • A PFAS, non-previously detected in environmental waters, was tentatively identified. [ABSTRACT FROM AUTHOR]

Leakage of light non-aqueous phase liquid (LNAPL) into soil can cause serious environmental issues. In this study, a two-dimensional device with adjustable dip angles was designed to investigate the migration and redistribution of LNAPL in natural inclined stratified soil media by the light transmission visualization (LTV) technology. The captured experimental images were processed to obtain the diesel distribution based on gray value which could represent the LNAPL saturation distribution. LNAPL may not be able to penetrate through the fine-coarse interface due to the capillary barrier effects. In this case, the vertical and horizontal migration distances (V and H), contaminated area (S), as well as deviation angle (γ) of centroid increased with the dip angle. Increasing the leakage amount to more than 30 mL would result in LNAPL breakthrough at the 10°-inclined interface, leading to much larger V , H , S , and γ than those at 10 mL, while 20-mL LNAPL failed to break through. In the latter case, a lower leakage rate than 10 mL/min would cause larger H and γ but similar V or S in the long term. This study could enrich the understanding of LNAPL contamination in vadose zone, providing reference for the prediction and treatment in realistic inclined contaminated sites. [Display omitted] • Effect of dip angle on LNAPL flow in the inclined stratified layers is studied. • The fine-coarse interface acts as a capillary barrier to the migration of LNAPL. • The dip angle in the inclined layers promotes the LNAPL flow along the interface. • Increasing the leakage amount of LNAPL is likely to break through the interface. • The leakage rate has a stronger effect on the horizontal migration distance. [ABSTRACT FROM AUTHOR]

Organohalide respiring bacteria (OHRB) are the mainstay for bioremediation of organohalide contaminated sites. Enrichment screening of OHRB is prerequisite for the development of high performance dehalogenating bacterial agents. Herein, different domestication strategies were formulated for the main factors (nutrients and inocula) affecting the enrichment of OHRB, and the dehalogenation effect was verified with 2-chlorophenol and per/polyfluoroalkyl substances. The nutrients had a greater impact on the dehalogenation of the systems relative to the inocula, where the combination of glucose and anaerobic sludge (Glu-AS) had a faster degradation rate (26 ± 2.5 µmol L−1 d−1) and more complete dechlorination effectiveness. Meanwhile, the dehalogenation results for perfluorooctanoic acid and trifluoroacetic acid showed the biological defluorination was closely related to the position of fluoride. Further, the microbial community structure profiled the resource competition, metabolic cross-feeding and nutrient dynamic exchange among fermenting bacteria, OHRB and methanogenic bacteria under different domestication strategies as endogenous factors affecting the dehalogenation performance, and speculated a hypothetical model for the interaction of different functional bacteria. Our research contributed guidelines and references for the development of efficient dehalogenating bacterial agents, and provided scientific theoretical and technical support for promoting the maximum efficiency of bioremediation of organohalogenated sites. [Display omitted] • Enrichment strategies are essential for the domestication of highly active OHRB. • The strong influence of nutrients on the dehalogenation efficiency of the system. • Biological defluorination is closely related to the position of the fluoride. • Different functional bacteria interactions determine the dehalogenation performance. [ABSTRACT FROM AUTHOR]

In-situ thermal desorption (ISTD) has attracted increasing attention owing to the efficient removal of organic contaminants from contaminated sites. However, it is poorly understood that whether and to what extent contamination degradation occurs upon oxygenation of reduced Fe-bearing clay minerals (RFC) in the subsurface during ISTD. In this study, we evaluated the mechanism of contaminant degradation upon oxygenation of reduced clay minerals during the ISTD. Reduced nontronite (rNAu-2) and montmorillonite (rSWy-3) were selected as RFC models. Results showed that thermal treatment during ISTD could significantly enhance phenol degradation, which increased from 25.8 % at 10 °C to 74.4 % at 70 °C in rNAu-2 and from 17.7 % at 10 °C to 49.8 % at 70 °C in rSWy-3. Correspondingly, the cumulative •OH at steady-state ([•OH] ss) increased by 3.7 and 1.5 times, respectively. The acceleration of Fe(II) oxidation with increasing temperature could be mainly responsible for [•OH] ss generation, which degrades phenol. Moreover, thermal treatment improved the fast oxidation of trioctahedral entities Fe(II)Fe(II)Fe(II) (TOF) and the slow oxidation of dioctahedral entities Fe(II)Fe(II) (DTF 1), AlFe(II) (DAF 1), and Fe(II)Fe(III) (DTF 2). Our study suggests that the overlooked degradation progress of phenol by oxygenation of RFC during ISTD, and it could be favorable for contaminant degradation during remediation. [Display omitted] • Phenol degradation upon RFC oxygenation was enhanced by 2.9-fold during the ISTD. • The acceleration of [•OH] ss increased phenol degradation with temperature. • The oxidation of structural Fe(Ⅱ) was accelerated by thermal treatment. • Thermal treatment enhanced [•OH] ss generation via one-electron transfer. [ABSTRACT FROM AUTHOR]

Perchlorate is a known endocrine-disrupting micropollutant. The efficiency of a low-cost in-situ bio-remediation process for perchlorate-contaminated aqueous phase was evaluated in a bench-scale unit in this study. The two-stage process unit comprises an anaerobic leach bed unit (5.3 L) for generating leachate and an anaerobic filter bed unit (10 L) inoculated with an isolated perchlorate reducing Serratia marcescens (GenBank Accession No. JQ807993). Organic leachate produced from anaerobic digestion of vegetable waste served as a sole substrate for the perchlorate reduction, and needle-felt natural fibre was used as a filter bed medium. The filter bed unit removed 98.5% of perchlorate at 10 mg/L initial concentration (volumetric loading, 39 mg/L/day) at an optimal soluble COD concentration of 40 mg/L in the leachate and a hydraulic retention time of 6.15 h. Controlled leachate delivery results in an effluent COD < 20 mg/L, reducing the risk of residual organic contamination in the treated water. Considering the many advantages, this approach would be more feasible for treating perchlorate-contaminated aquifers, streams, and surface canals. [Display omitted] • Cost-effective process for in-situ bioremediation of perchlorate. • Vegetable waste-derived leachate used as the sole substrate. • Needle-felt natural fibre used as a biofilm support medium. • Controlled delivery of substrate prevented residual organics. • Better substitute for in-situ remediation at contaminated sites. [ABSTRACT FROM AUTHOR]

Cadmium (Cd) and lead (Pb) are two of the most common elements found in contaminated sites. The behavior of specific metals in the soil may be affected by other metals because of the competition for adsorption sites. In this study, adsorption experiments after chemical extraction, multi-surface models, and advanced spectroscopy technology were jointly used to explain the adsorption mechanism of Cd and Pb and to determine the contribution of each component in the competitive system. The results show that pH is the key factor in determining the contribution of soil components to metal adsorption. Soil organic matter (SOM) is the dominant adsorbent for both Cd and Pb. Clay minerals play an adsorption role at low pH, whereas Fe/Al oxides adsorb metals primarily in the high pH range. Further, the competitive effect of Pb on Cd occurred primarily on SOM rather than on clay minerals. When the Pb concentration increased from 0 to 500 mg/L, the adsorption of Cd on SOM decreased by 132.0 mg/kg, whereas it decreased only by 1.9 mg/kg on clay minerals. Therefore, the competitive effect of Pb on Cd cannot be ignored in soils with high organic matter content. [Display omitted] • Metal adsorption is largely determined by soil pH. • Pb competes with Cd mostly at the SOM site rather than clay minerals. • The competitive effect of Pb on Cd cannot be ignored in high SOM soil. • Application of the MSMs enabled prediction of Cd and Pb adsorption on soils. [ABSTRACT FROM AUTHOR]

This paper provides physical and chemical performances of mass stabilised organic and inorganic contaminated site soils using a new group of MgO-bearing binders over 3 years and evaluated the time-dependent performance during the 3 years. This study took place at a contaminated site in Castleford, UK in 2011, where MgO, ground granulated blastfurnace slag (GGBS) and Portland cement (PC) were mixed with the contaminated soils in a dry form using the ALLU mass mixing equipment. Soil cores were retrieved 40-day, 1-year and 3-year after the treatment. The core quality, strength, and the leaching properties were determined via physical observation, unconfined compressive strength (UCS) and batch leaching tests. After 3-year treatment, the UCS values of ALLU mixes were in the range of 50–250 kPa; the leachate concentrations of Cd, Pb, Cu and Zn (except Ni) in all mixes were lower than their drinking water standards; and the leachability of total organics was in the range of 10–105 mg/L. No apparent degradation of the mass stabilised materials after 3 years’ exposure to the field conditions was found. MgO-GGBS blends were found able to provide higher strength and less leachability of contaminants compared to PC and MgO-only mixes in mass stabilised soils. [ABSTRACT FROM AUTHOR]

Better decisions are made using risk assessment models when uncertainty and variability are explicitly acknowledged. Uncertainty caused by a lack of uniform and scientifically supported environmental quality guidelines and variability in the degree of exposure of environmental systems to contaminants are here incorporated in a stochastic fuzzy environmental risk characterization (SFERC) approach. The approach is based on quotient probability distribution and environmental risk level fuzzy membership function methods. The SFERC framework was used to characterize the environmental risks posed by 16 priority polycyclic aromatic hydrocarbons (PAHs) in soil at a typical petroleum-contaminated site in China. This relied on integrating data from the literature and field and laboratory experiments. The environmental risk levels posed by the PAHs under four risk scenarios were determined using the SFERC approach, using “residential land” and “industrial land” environmental quality guidelines under “loose” and “strict” strictness parameters. The results showed that environmental risks posed by PAHs in soil are primarily caused by oil exploitation, traffic emissions, and coal combustion. The SFERC approach is an effective tool for characterizing uncertainty and variability in environmental risk assessments and for managing contaminated sites. [ABSTRACT FROM AUTHOR]

Natural attenuation of contaminants has been increasingly applied as a strategy to manage the retired pesticide manufacturing sites due to the increasing restrictions on the reuse of contaminated sites in China. However, the influencing factors to enhance natural attenuation for chlorinated hydrocarbons in retired pesticide sites were not well studied. In this paper, monitoring of pollutants, environmental factors and microbial community was conducted from 2016 to 2021 in a retired pesticide site in Jiangsu Province undergoing natural attenuation, where the groundwater was severely contaminated with chlorinated hydrocarbons. The spatial variation of main pollutants, including chlorinated ethenes and ethanes, indicated that the site could be divided into the source area, diffusion area, and the end of diffusion area, where organohalide-respiring bacteria (OHRB) were detected. Pollutants and environmental factors influenced the OHRB community structure, which explained 7.6% and 33.2% of the variation, respectively. The abundances of obligate and facultative OHRB were affected in opposite ways by pollutants and environmental factors. Dehalococcoides and Dehalogenimonas in obligate OHRB were significantly inhibited by sulfate (r = −0.448, p < 0.05). The spatial-temporal characteristics of pollutants and the reveal of microbial community structure and its restricting factors in different areas make the foundation for strengthening the implementation of natural attenuation. [Display omitted] • Natural attenuation of the chlorinated hydrocarbons contaminated site was studied. • The contaminated site was divided into three regions. • Organohalide-respiring bacteria (OHRB) were all detected in three regions. • The microbial community structure varied with pollutants and environmental factors. [ABSTRACT FROM AUTHOR]

Compound-specific isotopic analysis of multiple elements (C, Cl, H) was tested to better assess the effect of a zero-valent iron-permeable reactive barrier (ZVI-PRB) installation at a site contaminated with tetrachloroethene (PCE) and trichloroethene (TCE). The focus was on (1) using 13 C to evaluate natural chlorinated ethene biodegradation and the ZVI-PRB efficiency; (2) using dual element 13 C- 37 Cl isotopic analysis to distinguish biotic from abiotic degradation of cis -dichloroethene ( cis -DCE); and (3) using 13 C- 37 Cl- 2 H isotopic analysis of cis -DCE and TCE to elucidate different contaminant sources. Both biodegradation and degradation by ZVI-PRB were indicated by the metabolites that were detected and the 13 C data, with a quantitative estimate of the ZVI-PRB efficiency of less than 10% for PCE. Dual element 13 C- 37 Cl isotopic plots confirmed that biodegradation was the main process at the site including the ZVI-PRB area. Based on the carbon isotope data, approximately 45% and 71% of PCE and TCE, respectively, were estimated to be removed by biodegradation. 2 H combined with 13 C and 37 Cl seems to have identified two discrete sources contributing to the contaminant plume, indicating the potential of δ 2 H to discriminate whether a compound is of industrial origin, or whether a compound is formed as a daughter product during degradation. [ABSTRACT FROM AUTHOR]

Organic polluted sites have become a global concern of soil contamination, yet little is known about microbial vertical distribution and community assembly in organic polluted sites. Here, high-throughput sequencing technology was employed to investigate prokaryotic microbial diversity and community assembly along soil profile in an abandoned chemical organic contaminated site. Results showed that there was no significant difference (P > 0.05) observed in microbial alpha diversity among different soil layers, whereas the structure of microbial communities presented significantly different (P < 0.05) in the superficial layer (0–0.5 m) compared with intermediate (1–1.5 m) and bottom (2.5–3 m) layers. Soil prokaryotic microbial community evolved to possess the potential of degrading organic pollutants under long-term organic pollution stress. A relatively homogeneous environment created by the organic polluted site mainly induced the ecological process of homogeneous selection driving community assembly, while dispersal limitation gained importance with the increase of soil depth. Organic contaminants were identified as the key driver of destabilizing co-occurrence networks, while the frequent cooperative behaviors among species could combat organic pollution stress and sustain prokaryotic community stability. Collectively, pollution pressure and soil depth jointly affected prokaryotic microbial assemblage and co-occurrence that underpinned the spatial scaling patterns of organic contaminated sites microbiota. [Display omitted] • Homogeneous niches in organic polluted sites impelled the convergence of community. • Microbial degrading potential was positively linked to organic pollutants level. • Homogeneous selection and dispersal limitation jointly drove community assembly. • Taxa partnerships guaranteed the community stability under organic polluted stress. [ABSTRACT FROM AUTHOR]

It is important to identify key performance and core progress features of soil contamination management practices. Traditional research currently focuses on numerical statistics of contaminated sites but exhibits structural limitations regarding cross-assessment and in-depth analysis of published findings. Herein, we report a multidimensional perspective to assess the environmental management performance of soil contamination via systematic and historical development of construction land risk control and remediation lists (RCRLs). The considered contaminated sites are mainly concentrated in Northern China, Yangtze River Delta, Pearl River Delta, and Sichuan-Chongqing regions. Monthly historical overviews indicate that most lists are updated 4–5 times within 32 months. Direct chemical-related industrial production results in the largest number of contaminated sites. Arsenic and lead are the most common heavy metals of concern in soil contamination. The fiscal revenue index exhibits the best positive performance in terms of the number of contaminated sites. By employing the site number, update frequency, and published contents of different calculation proportions, ten types of integrated assessment indicators (IAIs) are established to evaluate the environmental achievements in various provincial regions in regard to soil contamination protection. This multifaceted strategy can provide advanced guidance for Chinese environmental management and expand the application of soil pollution risk control and remediation in a wide range of countries. [Display omitted] • IAI is fabricated by the site number, update time, and content information of RCRLs. • Chemical-related and metalworks factories are the main contaminated site sources. • Fiscal revenue displays a positive performance in favor of the number of sites. [ABSTRACT FROM AUTHOR]

In this work, the effect of different desorbents (low molecular weight organic acids (LMWOAs), surfactants, and inorganic salts) on naphthalene (NAP) desorption in soil was investigated, and the results showed that NAP desorption pattern fitted the pseudo-second-order kinetics. The addition of LMWOAs, especially citric acid (CA), could stimulate the reactive oxygen species (ROS) generation and NAP degradation in Fe(II) activated persulfate (PS) system, while the presence of surfactants and CaCl 2 could inhibit the NAP removal due to the competitive consumption of ROS. The maximum removal of NAP was 97.5% within 120 min at the PS/Fe(II)/CA/NAP molar ratio of 15/5/1/1, and the pseudo-first-order kinetic constant of NAP removal increased from 0.0110 min−1 to 0.0783 min−1 with the addition of CA. Compared with surfactants and inorganic salts, LMWOAs, especially CA, were more suitable as desorbent in soil washing coupled with in situ chemical oxidation technique. Moreover, 1.86 mg L−1 desorbed amount and 36.1% removal of NAP from soil could be obtained with the presence of 1 mM CA. Finally, the significant removal of NAP and other contaminants (phenanthrene, fluoranthene, and benzene series) in actual groundwater could provide theoretical basis and technical support for the remediation of organic contaminated sites with desorbents. [Display omitted] This study systematically reported the performance and mechanisms of NAP desorption and degradation in the presence of three different kinds of desorbents. The kinetics of NAP desorption and degradation with desorbents were elucidated. The effect of different desorbents on NAP removal was compared and LMWOAs, especially CA, were evaluated to be the optimal desorbents in the soil washing coupled with ISCO process. The enhancement of LMWOAs for NAP degradation was further illuminated. The significant removal of NAP in actual groundwater and other contaminants (PHE, FLT, and BTEX) could provide technical support for the remediation of organic contaminated sites with desorbents. • Effect of different desorbents on NAP desorption and degradation was investigated. • The kinetics of NAP desorption and degradation with desorbents was elucidated. • SO 4 −• and HO• contributed to NAP degradation in PS/Fe(II) system with desorbents. • Effective removal of NAP in actual groundwater containing desorbents was achieved. [ABSTRACT FROM AUTHOR]

Bioaugmentation is considered as a promising technology for cleanup of polycyclic aromatic hydrocarbons (PAHs) from contaminated site soil, however, available high-efficiency microbial agents remain very limited. Herein, we explored graphene oxide (GO)-immobilized bacterial pellets (JGOLB) by embedding high-efficiency degrading bacteria Paracoccus aminovorans HPD-2 in alginate-GO-Luria-Bertani medium (LB) composites. Microcosm culture experiments were performed with contaminated site soil to assess the effect of JGOLB on the removal of PAHs. The results showed that JGOLB exhibited greatly improved mechanical strength, larger specific surface area and more enriched mesopores, compared with traditional immobilized bacterial pellets. They significantly increased the removal rate of PAHs by 18.51% compared with traditional bacterial pellets, reaching the removal rate at 62.86% over 35 days of incubation. Moreover, the increase mainly focused on high-molecular-weight PAHs. JGOLB not only greatly increased the abundance of embedded degrading bacteria in soil, but also significantly enhanced the enrichment of potential indigenous degrading bacteria (Pseudarthrobacter and Arthrobacter), the functional genes involved in PAHs degradation and a number of ATP transport genes in the soil. Overall, such nanocomposite bacterial pellets provide a novel microbial immobilization option for remediating organic pollutants in harsh soil environment. [Display omitted] • Graphene oxide-immobilized bacterial pellets (GOBP) was explored. • GOBP exhibited greatly improved mechanical and structural properties. • GOBP significantly promoted the removal of PAHs in site soil. • GOBP greatly increased the abundance of embedded degrading bacterial in soil. • GOBP obviously enhanced the enrichment of potential indigenous degrading bacteria. [ABSTRACT FROM AUTHOR]

Contaminated sites pose a significant risk to human health and the regional environment. A comprehensive study was dedicated to improving the understanding of the contamination condition of a smelting site by integrating multi-source information through 3D visualization techniques. The results showed that 3D visualization reveals excellent potential for application in the environmental studies to finely depict contamination in soils and establish relationships with geological features, hydrological conditions, and sources of contamination. The contamination plume model revealed that the soil environment at the site was seriously threatened by toxic metals, and dominated by multi-metal contamination, with contamination soil volume ranked as Cd > As > Pb> Zn > Hg. The stratigraphic model revealed the heterogeneous geological conditions of the site and identified the mixed fill layer as the primary remediation soil layer. The permeability model revealed that soil permeability significantly influenced contamination dispersion and contributed to delineate the contamination boundary accurately. The ecological hazard model targeted the high ecological hazard area and determined the high hazard contribution of Cd and Hg in the site soil. The outcomes can be directly applied to actual site remediation and provide a reference for the contaminated sites evaluation and restoration in the future. [Display omitted] • Multi-source model establishes relationships between influences on site pollution. • 3D visualization holds great potential for finely delineating soil pollution. • 3D visualization of multi-metal composite pollution plumes was realized. [ABSTRACT FROM AUTHOR]

Lead exposure via ingestion of soil and dust generally occurs at lead-acid battery manufacturing and recycling sites. Screening solidification/stabilization (S/S) amendments suitable for lead contaminated soil in an abandoned lead-acid battery factory site was conducted based on its chemical forms and environmental risks. Twelve amendments were used to immobilize the Pb in soil and assess the solidification/stabilization efficiency by toxicity leaching tests. The results indicated that three amendments, KH 2 PO 4 (KP), KH 2 PO 4 :oyster shell power = 1:1 (by mass ratio; SPP), and KH 2 PO 4 :sintered magnesia = 1:1 (by mass ratio; KPM) had higher remediation efficiencies that led to a 92% reduction in leachable Pb with the addition of 5% amendments, while the acid soluble fraction of Pb (AS-Pb) decreased by 41–46% and the residual fraction (RS-Pb) increased by 16–25%. The S/S costs of the three selected amendments KP, SPP, and KPM could be controlled to $22.3 per ton of soil when the Pb concentration in soil ranged from 2000 to 3000 mg/kg. The results of this study demonstrated that KP, SPP, and KPM can effectively decrease bioavailability of Pb. These findings could provide basis for decision-making of S/S remediation of lead-acid battery contaminated sites. [ABSTRACT FROM AUTHOR]

Co-existence of polycyclic aromatic hydrocarbons (PAHs) and multi-metals challenges the decontamination of large-scale contaminated sites. This study aims to comprehensively evaluate the remediation potential of intensified phytoremediation in coping with complex co-contaminated soils. Results showed that the removal of PAHs and heavy metals is time-dependent, pollution-relevant, and plant-specific. Removal of sixteen PAHs by Medicago sativa L. (37.3%) was significantly higher than that of Solanum nigrum L. (20.7%) after 30 days. S. nigrum L. removed higher amounts of Cd than Zn and Pb, while M. sativa L. uptake more Zn. Nevertheless, amendments and microbial agents significantly increased the phytoremediation efficiency of pollutants and shortened the gap between plants. Cd removal and PAHs dissipation reached up to 80% and 90% after 90 days for both plants. Heavy metal stability in soil was promoted after the intensified phytoremediation. Plant lipid peroxidation was alleviated, regulated by changed antioxidant defense systems (superoxide dismutase, peroxidase, catalase). Soil enzyme activities including dehydrogenase, urease, and catalase increased up to 5-fold. Soil bacterial diversity and structure were changed, being largely composed of Proteobacteria, Actinobacteria, Patescibacteria, Bacteroidetes, and Firmicutes. These findings provide a green and sustainable approach to decontaminating complex-polluted environments with comprehensive improvement of soil health. [Display omitted] • Amendments and microbes significantly improved PAHs dissipation and metal removal. • Additions reduced Cd, Pb, Zn availability, shortened plant gap for phytoremediation. • Additions relieved plant oxidative stress to elevate tolerance to co-contamination. • Soil micro-ecology was promoted physichemically, biochemically and genetically. • Soil bacterial community diversity was dramatically increased. [ABSTRACT FROM AUTHOR]

The extractive industry is increasingly faced with problems of managing contaminated sites. The red gypsum landfill at the Ochsenfeld site is representative of the typology byproduct storage of the Ti-extraction activity. The management of the elemental content and the water body are the issues at this site. The aim of this study was to evaluate the canopy conductance (g cmax) of various tree species and the content of elements in the leaves, utilizing the opportunity of a demonstration plantation setup in 2014 with sixteen tree species, combined with a growth chamber experiment. We combined the gas exchange measurements with the data from two multispectral cameras with RGB and NIR bands embarked on an unmanned aerial vehicle (UAV). In the field, Ostrya carpinifolia, Maclura pomifera, and Rhus copallina had the highest g cmax of all planted tree species, and the high transpiration rate in O. carpinifolia was confirmed in a pot-based controlled experiment. Except R. copallina , the species with a high Mn content (O. carpinifolia , Betula pendula , and Salix aquatica grandis) had high stomatal conductance. O. carpinifolia could therefore be a species to exploit in the management of landfill leachates, especially in the context of climate change since this species is well adapted to dry environments. [Display omitted] • Management of landfills utilizing trees for water evaporation and element uptake was tested. • A method to calculate LAI in landfills by UAV 3D imaging was proposed. • The maximal canopy conductance of 16 tree species was derived from g smax and LAI. • Ostrya carpinifolia combined the highest growth, canopy conductance, and Mn uptake. [ABSTRACT FROM AUTHOR]

Toxic metal(loid) (TM) soil pollution at large-scale non-ferrous metal smelting contaminated sites is of great concern in China, but there are no detailed reports relating to them. A comprehensive study was conducted to determine contamination characteristics and horizontal and vertical spatial distribution patterns of soils at an abandoned zinc smelting site in Southern China. The spatial distribution of TMs revealed that soil environmental quality was seriously threatened, with Cd, Zn, As, Pb and Hg being the main contaminants present. The distribution of all TMs showed strong spatial heterogeneity and were expressed as a "patchy aggregation" pattern due to strong anthropogenic and production activities. Vertical migration of TMs indicated that the pollutants were mainly concentrated in the fill layers. Different contaminants had various migration depths, with migration occurring as: Cd > Hg > As > Zn > Pb> Cu> Mn> Sb. Analysis of their spatial variability showed that As, Pb, Cd and Hg had strong regional spatial variability. This research provides a new approach to comprehensively analyze TM pollution characteristics of non-ferrous smelting sites. It provides valuable information for guiding post-remediation strategies at abandoned non-ferrous metal smelting sites. [Display omitted] • Multidimensional distribution pattern of TMs at smelting sites is described. • Variability of TM pollution is determined both horizontally and vertically. • TM distribution revealed "patchy aggregation" due to production activities. • TMs revealed varying migration depths, expressed as: Cd > Hg > As > Zn > Pb> Cu > Mn > Sb. [ABSTRACT FROM AUTHOR]

Rhizodegradation using submersed macrophytes Vallisneria natans (V. natans) is a promising biotechnology with the potential to restore polycyclic aromatic hydrocarbon (PAH)-contaminated sediments. However, how different sediment types influence the rhizoremediation outcome and the characterization of microbial community along the sediment- V. natans continuum is poorly understood. Here, we collect V. natans , sediments and overlying water from two types of vegetation zones with different levels of PAHs pollutions and set up sediment microcosms for phytoremediation tests. V. natans presence was particularly useful for PAHs remediation in the highly contaminated sites and had a significant effect on PAHs rhizodegradation and microbial communities, especially rhizosphere sediments. The structural composition of microbial communities along the sediment-plant continuum was shaped predominantly by compartment niche of V. natans. Moreover, selective enrichment of specific microbial taxa like Herbaspirillum (relative abundance = 94.80%) in endosphere of V. natans was observed. Herbaspirillum could use PAH as carbon source and promote the growth of plants. In the highly contaminated sediment, V. natans could recruit these bacteria for toxicant degradation into the root interior. Thus, understanding the complex V. natans -microbe interactions could help set up novel decontamination strategies based on the rhizosphere and root interior interactions between plants and their microbial associates. [Display omitted] • V.natans was particularly useful for rhizoremediation of PAH-contaminated sediment. • V.natans had a significant effect on rhizosphere sediment microbial communities. • Specific microbial taxa like Herbaspirillum was enriched in endosphere of V.natans. • Microbiome along sediment-plant continuum was shaped by compartment niche of V.natans. [ABSTRACT FROM AUTHOR]

Heterogeneity in sediment and aquifer is universal, resulting in preferential flows of injected materials in the high permeability regions and forming flow by-passed zones in the low permeability regions during in-situ subsurface remediation. This adverse effect can considerably delay the completion of remedial operations and significantly increase the cost. Column experiments were designed and conducted to study the transport of starch- and starch-xanthan gum modified Fe-Mn binary oxide particles (SFM and SXFM) in saturated heterogeneous porous media and to reveal the particles' arsenic (As) stabilization performance. Fine-in-Coarse (FIC) and Coarse-in-Fine (CIF) patterns of heterogeneous packings were set up in the columns. Testing results demonstrated that starch-xanthan gum dual treatment on Fe-Mn binary oxides successfully improved the particles' migration capability in heterogeneous porous media and their distribution uniformity attributed to the profound shear thinning behavior of xanthan gum solution. The addition of xanthan gum to the system increased the viscosity and shear thinning property of the SXFM suspension, making it a better candidate for delivery. Both SFM and SXFM stabilized As in heterogeneously packed sediment collected from a contaminated site, with SXFM showing better stabilization performance than SFM. The stabilization effects of SXFM were 90.7–97.0%, compared to 82.0–95.2% of SFM. [Display omitted] • Shear thinning Fe-Mn fluids (SFM, SXFM) were designed for remediating As. • SXFM showed a better sweeping over the heterogenous systems than SFM. • Xanthan gum increased the viscosity of the amendments, enabling them penetrable. • The rheological behavior of SXFM revealed its usability in subsurface remediation. • Delivery of amendment to low permeability zones dictated As stabilization efficiency. [ABSTRACT FROM AUTHOR]

We used the Soil Water Assessment Tool (SWAT) as a framework to develop an empirical Hg flux model for Upper East Fork Poplar Creek (UEFPC), a Hg-contaminated watershed in Oak Ridge, Tennessee. By integrating long-term Hg monitoring data with simulated flow and suspended solid loads in a site-specific empirical Hg transport model, we (1) quantified the spatial, temporal, and flow regime controls on daily Hg flux (adjusted R2 = 0.82) and (2) made predictions about Hg flux under future climate, land use, and management scenarios. We found that 62.79% of the average daily Hg flux in the watershed is currently driven by base flow, whereas variability in Hg flux is driven by storm and extreme flow. We estimate an average annual Hg flux of 28.82 g day-1 leaving the watershed under baseline precipitation, with an estimated 43.73% reduction in daily Hg flux under drought conditions and a 296% increase in daily Hg flux in extreme precipitation scenarios. We estimated that a new mercury treatment facility would result in a 24.7% reduction in Hg flux under baseline conditions and a 33.4% reduction under extreme precipitation scenarios. The study demonstrated the merit of this approach, which can be replicated for sites where information on flow, suspended solids, and Hg concentrations is available. [Display omitted] • Watershed and empirical Hg transport models were linked to quantify Hg flux. • The models demonstrated high skill for predicting flow, sediment load, and Hg flux. • Baseflow controls 63% of the daily Hg flux in the Upper East Fork Poplar Creek watershed. • Scenario analysis showed that a new Treatment Facility will reduce Hg flux 24–33%. • Drought would decrease Hg flux by 44% and flooding would increase Hg flux by 296%. [ABSTRACT FROM AUTHOR]

BTEX and chlorinated aliphatic hydrocarbons (CAHs) are the common pollutants found at contaminated sites, and natural attenuation (NA) of CAHs was widely observed where they coexist. In this work, the groundwater in a site co-contaminated with BTEX and CAHs was monitored for 1 year. The compositions and activities of the microfloras, especially dechlorinators and their relationships with the contaminants, geochemical properties, seasons and depth were evaluated. The results are consistent with the well-known NA conceptual model where CAHs are not able to stimulate the enrichment of dechlorinators alone, but BTEX does promote dechlorination. The higher temperature, rather than ORP in the deeper groundwater of the wet season became a key factor to promote the abundance of dechlorinators, but only when BTEX was available, indicating that the substrates from the BTEX biodegradation played an important role in the dechlorinator enrichment. The elevated ORP in the shallower groundwater exceeded the optimum conditions for reductive dechlorination and no significant seasonal variation of dechlorinators was found. The co-occurrence network revealed the cooperative interactions among the functional microfloras in which dechlorinators, BTEX degraders, and fermentative bacteria jointly promoted the dechlorination. These findings provided us a further understanding of the NA processes in a commingled plume. [Display omitted] • BTEX probably promoted the dechlorinator enrichment, but CAHs did not. • The seasonally changed temperature was more crucial than ORP for dechlorinators. • The co-occurrence and interactions of the functional microfloras were proposed. [ABSTRACT FROM AUTHOR]

The historic usage and discharge of per- and polyfluoroalkyl substances (PFAS) containing chemicals have produced many contaminated sites and PFAS contamination has become a global concern due to their persistence, widespread distribution, and potential adverse impacts for human and environmental health. However, there have been limited investigations on the specific behavior of bacterial communities in PFAS contaminated soils. In this study, a quantitative PCR assay and Illumina MiSeq sequencing were used to investigate the variations of bacterial communities in a regional Australian airport contaminated with PFAS. The dominate PFAS detected in soil samples was Perfluorooctanesulfonic acid (PFOS), which accounted for 82% of total PFAS and the maximum PFOS level was noted (20,947±1824 ng.PFOS/mg.Soil) at the top soil. Irrespective of the degree of PFAS contamination at different depths, the comparable percentile contribution of each PFAS was observed in soil samples. Significantly higher bacteria amplicon sequence variant (ASV) and diversity were noted in uncontaminated soil than PFAS contaminated soil. Bacterial genera Rhodanobacter and Chujaibacter were dominant in the PFAS contaminated soil. Three different bacterial genera of Alphaproteobacteria , Ambiguous taxa of Acidobacteriia , and genus Chujaibacter of Gammaproteobacteria showed a significant positive correlation and RB41, Gaiella showed a significant negative correlation with 11 different PFAS concentrations. Overall, the results presented in this study suggest that the counts and species diversity of soil microorganisms are adversely influenced by PFAS contamination. [Display omitted] • This study investigates the behavior of bacterial communities that inhabit PFAS rich soil. • PFAS and organic carbon select different groups of bacteria. • 11 genera show significant correlations (P<0.05) with soil PFAS levels. • Diversity and population of soil bacteria are adversely influenced by PFAS. [ABSTRACT FROM AUTHOR]

Thermal desorption is one of the methods commonly used for the remediation of contaminated soil. However, its suitability for the treatment of widespread Cd-contaminated soil was seldom investigated, because the desorption of Cd was found to be difficult, even at a high heating temperature. In the present study, a biomass co-pyrolysis (BCP) method is proposed for the thermal treatment of Cd-contaminated soil. The results showed that, when the mixture of biomass and contaminated soil was pyrolyzed at ~550 oC, the gaseous pyrolytic products (such as CO and hydrocarbon gases) from the biomass could chemically reduce the Cd(II) into volatile Cd0, thereby allowing the evaporation of vaporized Cd0 from the soil within a short operating time. The BCP method can achieve a highly efficient removal of Cd from the soil samples spiked with a large amount of Cd(II). The remediated soil, containing the remaining biochars, showed a good regreening potential and a significant decrease in Cd bioavailability. It also showed a good performance for the remediation of field soils from four contaminated sites (>92% removal efficiencies), and one of the treated soils could even meet the Cd screening level of agricultural land of China. [Display omitted] • A biomass co-pyrolysis (BCP) method is proposed for treating Cd-contaminated soil. • Removal of Cd from the soil is achieved by a thermal reduction-desorption mechanism. • Reducing gases from the biomass pyrolysis could chemically reduce Cd(II) into Cd0. • Remediated soil containing remaining biochars showed a good regreening potential. • Validity of BCP method was verified by treating the co-contaminated soils from sites. [ABSTRACT FROM AUTHOR]

Abstract: In the present work the pollutant content of diverse building materials was evaluated by the combination of spectrometric and chromatographic techniques. A first non-destructive analysis carried out by μ-XRF and Raman spectroscopy revealed a high impact of pollutants, which reached depths higher than 6mm. The quantitative analyses pointed out that black crust as accumulation nucleus where concentration values up to 3408mg/kg of lead, 752mg/kg of chromium or 220mg/kg of arsenic, high amounts of diverse sulphates and nitrates as well as substantial amounts of polycyclic aromatic hydrocarbons (PAHs) of a clear pyrolytic source were determined. On the other hand, samples without black crust showed also a surprising soluble salt content up to 5%. Polychlorinated biphenyls (PCB) were found to be absent in all material types. The chemometric analysis of the quantitative results revealed that the accumulation capacity and the subsequent pollutant content depends on the type of construction materials, being mortars the most susceptible. [Copyright &y& Elsevier]

Abstract: Mass transport of chlorinated benzenes as found at the Petro-Processors of Louisiana, Inc. (PPI) Superfund site was characterized for a range of flow rates in small streams. At this site hazardous waste was historically disposed of in unengineered pits. Hexachlorobenzene and lesser chlorinated degradation products were found among other compounds. As waste was being disposed into unengineered pits, it seeped to lagoons and sediments of Baton Rouge Bayou (BRB), which flows through and nearby the former disposal areas. Characterization of the transport and fate of chlorobenzenes at PPI is an integral part of the Monitored Natural Attenuation (MNA) remedy currently underway. Laboratory experimental results and mathematical model predictions of the flux of 1,3-dichlorobenzene (1,3-DCB) from sediments into water are presented. 1,3-DCB was studied as individually and as part of a mixture of four contaminants with 1,2-DCB, chlorobenzene (MCB) and trichlorobenzene (TCB). Surficial sediments were collected, spiked with contaminants and leached to determine flux over time. Two advection–dispersion models were tested and the effect of low, cycling and fast stream flow on the contaminant flux was assessed. Model results suggest that tortuosity and effective diffusivity are related effective system predictors and descriptors. Statistical analysis supports the models’ predictive capabilities. [Copyright &y& Elsevier]

Abstract: In connection with installation of two natural gas pipelines through the Baltic Sea between Russia and Germany, there has been concern regarding potential re-suspension of historically dumped chemical warfare agents (CWA) in a nearby dump site and the potential environmental risks associated. 192 sediment and 11 porewater samples were analyzed for CWA residues, both parent and metabolites in 2008 and 2010 along the pipeline corridor next to the dump site. Macrozoobenthos and background variables were also collected and compared to the observed CWA levels and predicted potential risks. Detection frequencies and levels of intact CWA found were low, whereas CWA metabolites were more frequently found. Re-suspension of CWA residue-containing sediment from installation of the pipelines contributes marginally to the overall background CWA residue exposure and risk along the pipeline route. The multivariate weight-of-evidence analysis showed that physical and background parameters of the sediment were of higher importance for the biota than observed CWA levels. [Copyright &y& Elsevier]

Abstract: A simulation-based fuzzy multi-criteria decision analysis (SFMCDA) method is developed for supporting the selection of remediation strategies for petroleum contaminated sites. SFMCDA integrates process modeling (using BIOPLUME III) and fuzzy ranking (based on fuzzy TOPSIS) into a general management framework, and can compare various remediation alternatives, in light of both cost-risk tradeoffs and uncertainty impacts. The proposed method is applied to a hypothetical contaminated site suffering from a benzene leakage problem. Six remediation alternatives are taken into consideration, including natural attenuation (NA), pump-and-treat (PAT), enhanced natural attenuation (ENA), and a number of their combinations. Six fuzzy criteria, including both cost and risk information, are used to compare different alternatives through fuzzy TOPSIS. The results demonstrates that the proposed method can help systematically analyze fuzzy inputs from contaminant transport modeling, cost implications and stakeholders’ preferences, and provide useful ranking information covering a variety of decision-relevant remediation options for decision makers. [Copyright &y& Elsevier]

Abstract: A two-scale evaluation concept of remediation technologies for a contaminated site was expanded by introducing life cycle costing (LCC) and economic input–output life cycle assessment (EIO-LCA). The expanded evaluation index, the rescue number for soil (RN SOIL ) with LCC and EIO-LCA, comprises two scales, such as risk–cost, risk–energy consumption or risk–CO2 emission of a remediation. The effectiveness of RN SOIL with LCC and EIO-LCA was examined in a typical contamination and remediation scenario in which dieldrin contaminated an agricultural field. Remediation was simulated using four technologies: disposal, high temperature thermal desorption, biopile and landfarming. Energy consumption and CO2 emission were determined from a life cycle inventory analysis using monetary-based intensity based on an input–output table. The values of RN SOIL based on risk–cost, risk–energy consumption and risk–CO2 emission were calculated, and then rankings of the candidates were compiled according to RN SOIL values. A comparison between three rankings showed the different ranking orders. The existence of differences in ranking order indicates that the scales would not have reciprocal compatibility for two-scale evaluation and that each scale should be used independently. The RN SOIL with LCA will be helpful in selecting a technology, provided an appropriate scale is determined. [Copyright &y& Elsevier]

Abstract: A hydrophobic magnetic room temperature ionic liquid (MRTIL), trihexyltetradecylphosphonium tetrachloroferrate(III) ([3C6PC14][FeCl4]), was synthesized from trihexyltetradecylphosphonium chloride and FeCl3·6H2O. This MRTIL was investigated as a possible separation agent for solvent extraction of phenolic compounds from aqueous solution. Due to its strong paramagnetism, [3C6PC14][FeCl4] responds to an external neodymium magnet, which was employed in the design of a novel magnetic extraction technique. The conditions for extraction, including extraction time, volume ratio between MRTIL and aqueous phase, pH of aqueous solution, and structures of phenolic compounds were investigated and optimized. The magnetic extraction of phenols achieved equilibrium in 20min and the phenolic compounds were found to have higher distribution ratios under acidic conditions. In addition, it was observed that phenols containing a greater number of chlorine or nitro substituents exhibited higher distribution ratios. For example, the distribution ratio of phenol (D Ph) was 107. In contrast, 3,5-dichlorophenol distribution ratio (D 3,5-DCP) had a much higher value of 6372 under identical extraction conditions. When compared with four selected traditional non-magnetic room temperature ionic liquids, our [3C6PC14][FeCl4] exhibited significantly higher extraction efficiency under the same experimental conditions used in this work. Pentachlorophenol, a major component in the contaminated soil sample obtained from a superfund site, was successfully extracted and removed by use of [3C6PC14][FeCl4] with high extraction efficiency. Pentachlorophenol concentration was dramatically reduced from 7.8μgmL−1 to 0.2μgmL−1 after the magnetic extraction by use of [3C6PC14][FeCl4]. [Copyright &y& Elsevier]