New Perspective to Evaluate the Carbon Offsetting by Urban Blue-Green Infrastructure: Direct Carbon Sequestration and Indirect Carbon Reduction.

Urban blue-green infrastructure (BGI) offers a multitude of ecological advantages to residents, thereby playing a pivotal role in fortifying urban resilience and fostering the development of climate-resilient cities. Nonetheless, current research falls short of a comprehensive analysis of BGI's overall potential for carbon reduction and its indirect carbon reduction impact. To fill this research gap, we utilized the integrated valuation of ecosystem services and trade-offs model and remote sensing estimation algorithm to quantify the direct carbon sequestration and resultant indirect carbon reduction facilitated by the BGI within the Guangdong-Hong Kong-Macao Greater Bay Area (GBA) (China). To identify the regions that made noteworthy contributions to carbon offsets and outliers, spatial autocorrelation analysis was also employed. The findings of this study reveal that in 2019, the BGI within the study area contributed an overall carbon offset of 1.5 × 108 t·C/yr, of which 3.5 × 107 and 11.0 × 107 t·C/yr were the result of direct carbon sequestration and indirect carbon reduction, respectively. The GBA's total CO2 emissions were 1.1 × 108 t in 2019. While the direct carbon sequestration offset 32.0% of carbon emissions, the indirect carbon reduction mitigated 49.9% of potential carbon emissions. These results highlight the critical importance of evaluating BGI's indirect contribution to carbon reduction. The findings of this study provide a valuable reference for shaping management policies that prioritize the protection and restoration of specific areas, thereby facilitating the harmonized development of carbon offset capabilities within urban agglomerations.

Tessaracoccus lacteus sp. nov., Isolated from the Sludge of a Wastewater Treatment Plant.

A bacterium, designated strain T21T, that is non-motile, rod-shaped, and formed pale white colonies, was isolated from the sludge of a wastewater treatment plant's secondary sedimentation tank in China. Strain T21T could grow at 20-40 °C (optimum growth at 30 °C), pH 3.0-10.0 (optimum growth at pH 5.0) and in the presence of 0-8.0% (w/v) NaCl (optimum growth at 2.0%). Based on phylogenetic analysis of 16S rRNA gene sequences and genome sequences, the isolate belongs to the genus Tessaracoccus in the phylum Actinomycetota. It exhibited a close relationship with Tessaracoccus palaemonis J1M15T, Tessaracoccus defluvii LNB-140T, Tessaracoccus flavescens SST-39T, and Tessaracoccus coleopterorum HDW20T. The 16S rRNA gene sequence similarities are 99.8%, 97.9%, 97.9%, and 97.8%, respectively. The major cellular fatty acids were anteiso-C15:0 and C16:0. The main respiratory quinone was MK-9(H4). The polar lipids included phosphatidylglycerol, diphosphatidylglycerol, glycolipid, and phospholipid. Genome annotation of strain T21T predicted the presence of 2829 genes, of which 2754 are coding proteins and 59 are RNA genes. The genomic DNA G+C content was 69.2%. Based on the results of phylogenetic, phenotypic, chemotaxonomic, and genotypic analyses, we propose the name Tessaracoccus lacteus sp. nov. for this novel species within the genus Tessaracoccus. The type strain is T21T (=CCTCC AB 2023031T = KCTC 49936T).

Description and Genomic Characteristics of Diaphorobacter limosus sp. nov., Isolated from a Sewage-Treatment Plant.

A Gram-stain-negative, rod-shaped, non-motile, catalase-positive, denitrifying bacterium, designated strain Y-1T, was isolated from an aeration tank of a sewage treatment plant in China and characterized using polyphasic taxonomic approaches. Strain Y-1T could grow at 10-37 °C (optimum 25 °C), at pH 5.0-10.0 (optimum 7.0) and in the presence of 0-3.0% (w/v) NaCl (optimum 0.5%). The phylogenetic tree based on the 16S rRNA gene sequences revealed that strain Y-1T was a member of genus Diaphorobacter, and showed the highest sequence similarities with Diaphorobacter oryzae RF3T (97.50%), Diaphorobacter nitroreducens NA10BT (97.38%) and Diaphorobacter aerolatus 8604S-37T (96.56%). In terms of carbon source utilization and enzyme activities, strain Y-1T was significantly different from its similar strains. The major respiratory quinone was Q-8, and the main polar lipid was phosphatidylethanolamine. Comparative genomic analysis of strain Y-1T and other Diaphorobacter species was conducted to explore the mechanisms underlying the differences among these strains. Strain Y-1T encoded 3957 genes, consisting of 3813 protein-coding genes and 144 RNA coding genes, and encoded 652 enzymes with 31 unique enzymes compared with other related species. The DNA G + C content was 69.95 mol%. Strain Y-1T exhibited 41.71% DNA-DNA relatedness and 95% ANIb with the most related type strains.On the basis of the evidence presented from polyphasic analysis, strain Y-1T was suggested as a novel species within the genus Diaphorobacter, for which the name Diaphorobacter limosus sp. nov. is proposed, with the type strain Y-1T (= KCTC 92852T = CCTCC AB 2023032T).

Electroreductive Defluorination of Unsaturated PFAS by a Quaternary Ammonium Surfactant-Modified Cathode via Direct Cathodic Reduction.

Remediation of per- and polyfluoroalkyl substances (PFAS) in groundwater remains a technological challenge due to the trace concentrations of PFAS and the strength of their C-F bonds. This study investigated an electroreductive system with a quaternary ammonium surfactant-modified cathode for degrading (E)-perfluoro(4-methylpent-2-enoic acid) (PFMeUPA) at a low cathodic potential. A removal efficiency of 99.81% and defluorination efficiency of 78.67% were achieved under -1.6 V (vs Ag/AgCl) at the cathode modified by octadecyltrimethylammonium bromide (OTAB). The overall degradation procedure started with the adsorption of PFMeUPA onto the modified cathode. This adsorption process was promoted by hydrophobic and electrostatic interactions between the surfactants and PFMeUPA, of which the binding percentage, binding mode, and binding energy were determined via molecular dynamics (MD) simulations and density functional theory (DFT) calculations. The step-wise degradation pathway of PFMeUPA, including reductive defluorination and hydrogenation, was derived. Meanwhile, C-F bond breaking with direct electron transfer only was achieved for the first time in this study, which also showed that the C═C bond structure of PFAS facilitates the C-F cleavage. Overall, this study highlights the crucial role of quaternary ammonium surfactants in electron transfer and electrocatalytic activities in the electroreductive system and provides insights into novel remediation approaches on PFAS-contaminated groundwater.

New Insights into the Accumulation, Transport, and Distribution Mechanisms of Hexafluoropropylene Oxide Homologues, Important Alternatives to Perfluorooctanoic Acid, in Lettuce (Lactuca sativa L.).

Hexafluoropropylene oxide (HFPO) homologues, which are important alternatives to perfluorooctanoic acid, have been frequently identified in crops. Although exposure to HFPO homologues via crops may pose non-negligible threats to humans, their impact on crops is still unknown. In this study, the accumulation, transport, and distribution mechanisms of three HFPO homologues in lettuce were investigated at the plant, tissue, and cell levels. More specifically, HFPO trimer acid and HFPO tetramer acid were primarily fixed in roots and hardly transported to shoots (TF, 0.06-0.63). Conversely, HFPO dimer acid (HFPO-DA) tended to accumulate in lettuce shoots 2-264 times more than the other two homologues, thus resulting in higher estimated daily intake values. Furthermore, the dissolved organic matter derived from root exudate enhanced HFPO-DA uptake by increasing its desorption fractions in the rhizosphere. The transmembrane uptake of HFPO homologues was controlled by means of a transporter-mediated active process involving anion channels, with the uptake of HFPO-DA being additionally facilitated by aquaporins. The higher accumulation of HFPO-DA in shoots was attributed to the larger proportions of HFPO-DA in the soluble fraction (55-74%) and its higher abundance in both vascular tissues and xylem sap. Our findings expand the understanding of the fate of HFPO homologues in soil-crop systems and reveal the underlying mechanisms of the potential exposure risk to HFPO-DA.

Comparative Life-Cycle Assessment of Aquifer Thermal Energy Storage Integrated with in Situ Bioremediation of Chlorinated Volatile Organic Compounds.

Due to the increasing need for sustainable energy and environmental quality in urban areas, the combination of aquifer thermal energy storage (ATES) and in situ bioremediation (ISB) has drawn much attention as it can deliver an integrated contribution to fulfill both demands. Yet, little is known about the overall environmental impacts of ATES-ISB. Hence, we applied a life-cycle assessment (LCA) to evaluate the environmental performance of ATES-ISB, which is also compared with the conventional heating and cooling system plus ISB alone (CHC + ISB). Energy supply via electricity is revealed as the primary cause of the environmental impacts, contributing 61.26% impacts of ATES-ISB and 72.91% impacts of CHC + ISB. Specifically, electricity is responsible for over 95% of water use, global warming potential, acidification potential, and respiratory inorganics, whereas the production of the biological medium for bioremediation causes more than 85% of the eco- and human toxicity impacts in both cases. The overall environmental impact of ATES-ISB is two times smaller than that of CHC + ISB. Sensitivity analysis confirms the importance of electricity consumption and electron donor production to the environmental impacts in both energy supply and bioremediation. Thus, future studies and practical applications seeking possible optimization of the environmental performances of ATES-ISB are recommended to focus more on these two essential elements, e.g., electricity and electron donor, and their related parameters. With the comprehensive LCA, insight is obtained for better characterizing the crucial factors as well as the relevant direction for future optimization research of the ATES-ISB system.

Combination of aquifer thermal energy storage and enhanced bioremediation: resilience of reductive dechlorination to redox changes.

To meet the demand for sustainable energy, aquifer thermal energy storage (ATES) is widely used in the subsurface in urban areas. However, contamination of groundwater, especially with chlorinated volatile organic compounds (CVOCs), is often being encountered. This is commonly seen as an impediment to ATES implementation, although more recently, combining ATES and enhanced bioremediation of CVOCs has been proposed. Issues to be addressed are the high water flow velocities and potential periodic redox fluctuation that accompany ATES. A column study was performed, at a high water flow velocity of 2 m/h, simulating possible changes in subsurface redox conditions due to ATES operation by serial additions of lactate and nitrate. The impacts of redox changes on reductive dechlorination as well as the microbial response of Dehalococcoides (DHC) were evaluated. The results showed that, upon lactate addition, reductive dechlorination proceeded well and complete dechlorination from cis-DCE to ethene was achieved. Upon subsequent nitrate addition, reductive dechlorination immediately ceased. Disruption of microorganisms' retention was also immediate and possibly detached DHC which preferred attaching to the soil matrix under biostimulation conditions. Initially, recovery of dechlorination was possible but required bioaugmentation and nutrient amendment in addition to lactate dosing. Repeated interruption of dechlorination and DHC activity by nitrate dosing appeared to be less easily reversible requiring more efforts for regenerating dechlorination. Overall, our results indicate that the microbial resilience of DHC in biosimulated ATES conditions is sensitive to redox fluctuations. Hence, combining ATES with bioremediation requires dedicated operation and monitoring on the aquifer geochemical conditions.

Biodegradation of cis-1,2-Dichloroethene in Simulated Underground Thermal Energy Storage Systems.

Underground thermal energy storage (UTES) use has showed a sharp rise in numbers in the last decades, with aquifer thermal energy storage (ATES) and borehole thermal energy storage (BTES) most widely used. In many urban areas with contaminated aquifers, there exists a desire for sustainable heating and cooling with UTES and a need for remediation. We investigated the potential synergy between UTES and bioremediation with batch experiments to simulate the effects of changing temperature and liquid exchange that occur in ATES systems, and of only temperature change occurring in BTES systems on cis-DCE reductive dechlorination. Compared to the natural situation (NS) at a constant temperature of 10 °C, both UTES systems with 25/5 °C for warm and cold well performed significantly better in cis-DCE (cis-1,2-dichloroethene) removal. The overall removal efficiency under mimicked ATES and BTES conditions were respectively 13 and 8.6 times higher than in NS. Inoculation with Dehalococcoides revealed that their initial presence is a determining factor for the dechlorination process. Temperature was the dominating factor when Dehalococcoides abundance was sufficient. Stimulated biodegradation was shown to be most effective in the mimicked ATES warm well because of the combined effect of suitable temperature, sustaining biomass growth, and regular cis-DCE supply.

Unveiling activation mechanism of persulfate by homologous hemp-derived biochar catalysts for enhanced tetracycline wastewater remediation.

Advancements in biochar activating persulfate advanced oxidation processes (PS-AOP), have gained significant attention. However, the understanding of biochar-based catalysts in activating PS remains limited. Herein, biochar (BC) and N-doped biochar (NBC) were synthesized from hemp for activating PS to treat tetracycline (TC) wastewater and analyzed their mechanisms separately. Surprisingly, N-doped in biochar leads to a change in the activation mechanism of PS. The BC-PS system operates mainly through a radical pathway, advantageous for treating soil organic pollution (68%) with pH adaptability (less than 10% variation). Nevertheless, the NBC-PS system primarily employs an electron transfer non-radical pathway, demonstrating stability (only 7% performance degradation over four cycles) and enhanced resistance to anionic interference (less than 10% variation) in organic wastewater treatment. This study provides a technical reference and theoretical foundation for enhancing biochar activation of PS in the removal of organic pollutants from aquatic and terrestrial environments.

Modified nano zero-valent iron coupling microorganisms to degrade BDE-209: Degradation pathways and microbial responses.

Polybrominated diphenyl ethers (PBDEs) in soil and groundwater have garnered considerable attention owing to the significant bioaccumulation potential and toxicity. Currently, the coupling treatment method of nano zero-valent iron (nZVI) with dehalogenation microorganisms is a research hotspot in the field of PBDE degradation. In this study, various systems were established within anaerobic environments, including the nZVI-only system, microorganism-only system, and the nZVI + microorganisms system. The aim was to investigate the degradation pathway of BDE-209 and elucidate the degradation mechanism within the coupled system. The results indicated that the degradation efficiency of the coupled system was better than that of the nZVI-only or microorganism-only system. Two modified nZVI (carboxymethyl cellulose and polyacrylamide) were prepared to improve the coupling degradation efficiency. CMC-nZVI showed the highest stability, and the coupled system consisting of microorganisms and CMC-nZVI showed the best degradation effect among all of the systems in this study, reaching 89.53% within 30 days. Furthermore, 22 intermediate products were detected in the coupling systems. Notably, changing the inoculation time did not significantly improve the degradation effect. The expression changes of the two reductive dehalogenase genes, e.g. TceA and Vcr, reflected the stress response and self-recovery ability of the dehalogenating bacteria, indicating such genes can be used as biomarker for evaluating the degradation performance of the coupling system. These findings provide a better understanding about the mechanism of coupling debromination process and the direction for the optimization and on-site repair of coupled systems.

Novel heterogeneous Fenton catalysts for promoting carbon iron electron transfer by one-step hydrothermal synthesization.

Carbon materials play a crucial role in promoting the Fe(III)/Fe(II) redox cycle in heterogeneous Fenton reactions. However, the electron transfer efficiency between carbon and iron is typically low. In this study, we prepared a novel heterogeneous Fenton catalyst, humboldtine/hydrothermal carbon (Hum/HTC), using a one-step hydrothermal method and achieved about 100 % reduction in Fe(III) during synthesis. Moreover, the HTC continuously provided electrons to promote Fe(II) regeneration during the Fenton reaction. Electron paramagnetic resonance (EPR) and quenching experiments showed that Hum/HTC completely oxidized As(III) to As(V) via free radical and non-free radical pathways. Attenuated total reflectance Fourier-transform infrared (ATR-FTIR) and two-dimensional correlation spectroscopy (2D-COS) analyses revealed that monodentate mononuclear (MM) and bidentate binuclear (BB) structures were the dominant bonding methods for As(V) immobilization. 40 %Hum/HTC exhibited a maximum As(III) adsorption capacity of 167 mg/g, which was higher than that of most reported adsorbents. This study provides a novel strategy for the efficient reduction of Fe(III) during catalyst synthesis and demonstrates that HTC can continuously accelerate Fe(II) regeneration in heterogeneous Fenton reactions.

Crop Contamination and Human Exposure to Per- and Polyfluoroalkyl Substances around a Fluorochemical Industrial Park in China.

Due to their significant environmental impact, there has been a gradual restriction of the production and utilization of legacy per- and polyfluoroalkyl substances (PFAS), leading to continuous development and adoption of novel alternatives. To effectively identify the potential environmental risks from crop consumption, the levels of 25 PFAS, including fourteen perfluoroalkyl acids (PFAAs), two precursor substances and nine novel alternatives, in agricultural soils and edible parts of various crops around a fluoride industrial park (FIP) in Changshu city, China, were measured. The concentration of ΣPFAS in the edible parts of all crops ranged from 11.64 to 299.5 ng/g, with perfluorobutanoic acid (PFBA) being the dominant compound, accounting for an average of 71% of ΣPFAS. The precursor substance, N-methylperfluoro-octanesulfonamidoacetic acid (N-MeFOSAA), was detected in all crop samples. Different types of crops showed distinguishing accumulation profiles for the PFAS. Solanaceae and leafy vegetables showed higher levels of PFAS contamination, with the highest ΣPFAS concentrations reaching 190.91 and 175.29 ng/g, respectively. The highest ΣAlternative was detected in leafy vegetables at 15.21 ng/g. The levels of human exposure to PFAS through crop consumption for various aged groups were also evaluated. The maximum exposure to PFOA for urban toddlers reached 109.8% of the standard value set by the European Food Safety Authority (EFSA). In addition, short-chained PFAAs and novel alternatives may pose potential risks to human health via crop consumption.

Enhanced trichloroethylene biodegradation: The mechanism and influencing factors of combining microorganism and carbon­iron materials.

Trichloroethylene (TCE) is one of the most prevalent contaminants with long-term persistence and a strong carcinogenic risk. Biological dechlorination has gradually become the mainstream method due to its advantages of low treatment cost and high environmental friendliness. However, microorganisms are easily restricted by environmental factors, such as an insufficient energy supply and a slow biological dechlorination process. This study focused on the coupled degradation of TCE with the combination of microorganisms and assistant materials (biochar, nZVI, nZVI modified biochar, HPO3 modified biochar), and set up microorganisms (alone) and materials (alone) as separate controls. Biochar provided nutrients, increased contact with pollutants, and promoted electron transfer to improve TCE degradation, although it did not change the pathway of degradation. The coupled treatment with anaerobic microorganisms (Micro) and 1 g/L unmodified biochar (BC) had the strongest degradation capacity. Compared with microorganisms alone, the addition of biochar resulted in the complete removal of TCE within 4 days. The influence of ambient temperature was mainly related to microbial activity, and 35 °C showed better degradation than 20 °C. Under 20 °C, 1 g/L of nZVI significantly promoted microbial dechlorination. As the dosage increased to 2 g/L and 4 g/L, nZVI showed a strong toxic effect. After 16 days, TCE was completely converted to ethylene by Micro-BC with C3H5O3Na, while 4.40 µmol dichloroethane (DCE) and 1.48 µmol vinyl chloride (VC) remained in the treatment with Micro-BC alone. As an electron acceptor, NaNO3 directly competed with TCE in the reduction process, which decreased the reduction efficiency of TCE. These findings provide a better understanding of the mechanism of the chemical materials coupling microbial dechlorination process and an optimal treatment method for trichloroethylene degradation.

Water Management Impacts on Chromium Behavior and Uptake by Rice in Paddy Soil with High Geological Background Values.

Chromium (Cr) is an expression toxic metal and is seriously released into the soil environment due to its extensive use and mining. Basalt is an important Cr reservoir in the terrestrial environment. Cr in paddy soil can be enriched by chemical weathering. Therefore, basalt-derived paddy soils contain extremely high concentrations of Cr and can enter the human body through the food chain. However, the water management conditions' effect on the transformation of Cr in basalt-derived paddy soil with high geological background values was less recognized. In this study, a pot experiment was conducted to investigate the effects of different water management treatments on the migration and transformation of Cr in a soil-rice system at different rice growth stages. Two water management treatments of continuous flooding (CF) and alternative wet and dry (AWD) and four different rice growth stages were set up. The results showed that AWD treatment significantly reduced the biomass of rice and promoted the absorption of Cr in rice plants. During the four growth periods, the root, stem and leaf of rice increased from 11.24-16.11 mg kg-1, 0.66-1.56 mg kg-1 and 0.48-2.29 mg kg-1 to 12.43-22.60 mg kg-1, 0.98-3.31 mg kg-1 and 0.58-2.86 mg kg-1, respectively. The Cr concentration in roots, stems and leaves of AWD treatment was 40%, 89% and 25% higher than CF treatment in the filling stage, respectively. The AWD treatment also facilitated the potential bioactive fractions conversion to the bioavailable fraction, compared with the CF treatment. In addition, the enrichment of iron-reducing bacteria and sulfate-reducing bacteria with AWD treatment also provided electron iron for the mobilization of Cr, thus affecting the migration and transformation of Cr in the soil. We speculated that the reason for this phenomenon may be the bioavailability of Cr was affected by the biogeochemical cycle of iron under the influence of alternating redox. This indicates that AWD treatment may bring certain environmental risks in contaminated paddy soil with high geological background, and it is necessary to be aware of this risk when using water-saving irrigation to plant rice.

Nano zero-valent iron enhances the absorption and transport of chromium in rice (Oryza sativa L.): Implication for Cr risks management in paddy fields.

Chromium (Cr) accumulating in soil caused serious pollution to cultivated land. At present, nano zero-valent iron (nZVI) is considered to be a promising remediation material for Cr-contaminated soil. However, the nZVI impact on the behavior of Cr in the soil-rice system under high natural geological background value remains unknown. We studied the effects of nZVI on the migration and transformation of Cr in paddy soil-rice by pot experiment. Three different doses of nZVI (0, 0.001 % and 0.1 % (w/w)) treatments and one dose of 0.1 % (w/w) nZVI treatment without plant rice were set up. Under continuous flooding conditions, nZVI significantly increased rice biomass compared with the control. At the same time, nZVI significantly promoted the reduction of Fe in the soil, increased the concentration of oxalate Fe and bioavailable Cr, then facilitated the absorption of Cr in rice roots and the transportation to the aboveground part. In addition, the enrichment of Fe(III)-reducing bacteria and sulfate-reducing bacteria in soil provided electron donors for Cr oxidation, which helps to form bioavailable Cr that is easily absorbed by plants. The results of this study can provide scientific basis and technical support for the remediation of Cr -polluted paddy soil with high geological background.

Co-transport of biochar nanoparticles (BC NPs) and rare earth elements (REEs) in water-saturated porous media: New insights into REE fractionation.

The present study investigated the co-transport behavior of three REEs3+ (La3+, Gd3+, and Yb3+) with and without biochar nanoparticles (BC NPs) in water-saturated porous media. The presence of REEs3+ enhanced the retention of BC NPs in quartz sand (QS) due to decreased electrostatic repulsion between BC NPs and QS, enhanced aggregation of BC NPs, and the contribution of straining. The distribution coefficients (KD) in packed columns in the co-transport of BC NPs and three REEs3+ were much smaller than in batch experiments due to the different hydrodynamic conditions. In addition, we, for the first time, found that REE fractionation in the solid-liquid phase occurred during the co-transport of REEs3+ in the presence and absence of BC NPs. Note that the REE fractionation during the co-transport, which is helpful for the tracing application during earth surface processes, was driven by the interaction of REEs3+ with QS and BC NPs. This study elucidates novel insights into the fate of BC NPs and REEs3+ in porous media and indicates that (i) mutual effects between BC NPs and REE3+ should be considered when BC was applied to REE contaminated aquatic and soil systems; and (ii) REE fractionation provides a useful tool for identifying the sources of coexisting substances.

Ecological influences of the migration of micro resin particles from crushed waste printed circuit boards on the dumping soil.

About 0.8 million tons of resin particles, which were generated from the recovery of waste printed circuit boards, were dumped on soil at Qingyuan city of China. Resin particles not only belong to micro plastic but also contain brominated flame retardants and heavy metals. There is little information about soil pollution caused by the dumped resin particles. This study found resin particles would transfer from soil surface into soil at least 10 mm downward for six months. Average content of bromine in soil within 10 cm exceeded 2500 mg/kg. The highest content of Pb, Zn, and Cu was 3450, 1143 and 1450 mg/kg, which were approximately 6.9, 2.3 and 3.6 times as much as Grade Ⅲ soil standard of China. Micro plastic, brominated flame retardants, and heavy metals made significant effects on soil bacterial community. Bacterial diversity was destroyed and the number of resistant bacteria increased obviously such as Acinetobacter, Pseudomonas and Paracoccus. This paper presented the ecological destroy of soil when the resin particles were deposited on soil surface. It also suggested the government to urgently manage the resin particles produced in the recovery of waste printed circuit boards.

Mechanisms of Pb and/or Zn adsorption by different biochars: Biochar characteristics, stability, and binding energies.

Biochar has been widely studied as an amendment for use in remediation of water and soil contaminated with heavy metals such as Pb2+ and Zn2+, but the effects of biochar characteristics, including stability, on the competitive adsorption of Pb2+ and Zn2+ by biochars from various sources are incompletely understood. In this work, biochars from three different feedstocks, including rice straw (RS), chicken manure (CM), and sewage sludge (SS), were prepared at two pyrolysis temperatures, 550 and 350 °C, and tested to investigate the influence of their stabilities and other characteristics on their adsorption of Pb2+ and Zn2+ in both single- and binary-metal systems. RS biochar had the highest carbon and hydrogen contents, greatest number of functional groups (e.g., OH and C=C/C=O), highest pH, most negative surface charge, and highest physical stability, and thus the highest adsorption capacity for Pb2+ and Zn2+. Pyrolysis at the higher temperature resulted in a slight decrease in aromatic functional groups on biochar surfaces but higher adsorption capacities for Pb2+ and Zn2+ due to the decreased biochar particle size and increased specific surface area. FTIR, XRD, and XPS analyses indicated that Pb2+ and Zn2+ were absorbed on the biochars primarily via chemical complexation with aromatic functional groups. Quantum chemistry calculations confirmed that these functional groups (e.g., -OH and-COOH) tended to bind more strongly with Pb2+ than with Zn2+ due to the former's lower binding energies, which also accounted for the notable decrease in adsorption of Zn2+ in the presence of Pb2+. In addition, compared to carboxyl groups, hydroxyl groups had smaller binding energies and stronger metal complexation. These findings provide a theoretical basis for improved understanding of potential applications of biochars in environmental remediation.

Fractionation of mono- and divalent ions by capacitive deionization with nanofiltration membrane.

In this study, we demonstrated the influence of adding nanofiltration membranes to a CDI cell, when desalinating mono- and divalent salt solutions both theoretically and experimentally, and proposed a new procedure for the separation of mono- and divalent ions. It is revealed that the distinction of the diffusion coefficient between mono- and divalent ions is the key to the effective separation. Combined with the appropriate time of adsorption (1.5 h), the concentration ratio of NaCl to MgSO4 can be increased by a factor of 3, from a mixture with equal amount of NaCl and MgSO4.

Potential impact of hydrodynamic shear force in aquifer thermal energy storage on dissolved organic matter releasement: A vigorous shaking batch study.

The combination of bioremediation and aquifer thermal energy storage (ATES) has become attractive because of the possibility of solving environmental and energy problems simultaneously. While the impact of ATES on groundwater quality due to temperature change has received ample attention in literature, the effect of the greatly enhanced groundwater flow velocity on groundwater quality has not yet received sufficient scientific attention. To fill this gap in understanding, we conducted a simple yet straightforward experiment to illustrate the impact of hydrodynamic shear force due to the water flow by ATES on the release of dissolved organic matter, which can potentially be advantageous to bioremediation. Vigorous shaking conditions were applied to simulate the enhanced dynamics at the ATES well center and nearby. As the indicators of dissolved organic matter, COD and TOC concentrations were significantly impacted by shaking. COD increased from 5.4 mgO2/L to 36.3 mgO2/L during horizontal shaking. The maximum COD level was determined as 33.8 mgO2/L during orbital shaking, while the TOC level was growing from 6.7 to 28.7 mg C/L. Meanwhile, redox potential (with initial level -100 mV) was decreasing to -450 mV synchronously with the elevating COD and TOC level. Temperature was also revealed as a significant factor in the organic matter releasement. Microbial iron reduction was deemed to occur, yet sulfate reduction was not initiated during the whole experiment. Eventually, the structure of the soil-water matrix has been changed due to the extensive hydraulic and particle collisions, resulting in blackish appearance and thicker layer of fine particles. Overall, the findings advance our understanding of the role of the ATES-induced water flow in the subsurface biogeochemistry and give insight into the perspective of the combination of bioremediation and ATES. In general, an increase in dissolved organic matter can be expected due to the increased shear force at high flow conditions in the ATES system.