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Arsenic (As)-contaminated agricultural soils threaten crop yields and pose a human health risk. Augmentation of exogenous microorganisms exhibiting plant-growth promoting and As speciation changing shows potential to improve crop growth and change soil As availability. Trichoderma asperellum SM-12F1 exhibiting both traits was developed into chlamydospores to improve its persistence in contaminated soils. After inoculation, As availability and enzyme activity in two types of soils and the growth as well as As uptake of water spinach ( Ipomoea aquatic Forsk.) were investigated. The results indicated that inoculation significantly improved water spinach growth in both soils. Inoculating chlamydospores at 5% significantly increased As concentration (139%), bioconcentration factor (150%), and translocation factor (150%) in water spinach grown in Chenzhou (CZ) soils, while no significant change for these in Shimen (SM) soils. Inoculating chlamydospores at 5% caused a significant increase (16%) of available As content in CZ soils, while a significant decrease (13%) in SM soils. Inoculation significantly caused As methylation in both soils, while significant As reduction merely observed in CZ soils. The differential changes in available As contents in both soils were attributed to the soil pH, As fractionations and speciation characteristics. Furthermore, Inoculating chlamydospores at 5% significantly improved the activities of β-glucosidase (155%), chitinase (211%), and phosphatase (108%) in SM soils, while significant decreases in β-glucosidase (81%), phosphatase (54%), aminopeptidase (60%), and catalase (67%) in CZ soils. Bioaugmentation and As availability change were responsible for this result. These observations will be helpful for the application of fungal chlamydospores in the future bioremediation. [ABSTRACT FROM AUTHOR]

Microorganisms dominated speciation of arsenic (As) play an important role in the biogeochemical cycling of As. In the study, species transformation of arsenite [As(III)] and As(III) influx and efflux across the cell membranes of Trichoderma asperellum SM-12F1, Penicillium janthinellum SM-12F4, and Fusarium oxysporum CZ-8F1 cells were studied using a cellular lysis plus chromatographic separation method and further the in-situ X-ray absorption near edge structure (XANES) analysis. The results indicated that As(III) can enter into fungal cells and that a portion of the As(III) can be exuded out of cells. For both As sequestrated into fungal cytoplasm and As adsorbtion onto cell walls, As(III) was found to be the dominated form of As. XANES analysis showed that As(III) accounted for 58.4%, 59.5%, and 73.0% of the total As in the cells of T . asperellum SM-12F1, P . janthinellum SM-12F4, and F . oxysporum CZ-8F1, respectively. Among these fungal strains, however, there were obvious differences in the relative proportions of arsenate [As(V)], monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA). For T . asperellum SM-12F1, the proportion (%) of MMA was 31.1%, and no As(V) or DMA was detected. For F . oxysporum CZ-8F1, the proportions of As(V) and MMA were 15.8% and 8.8%, respectively, but no DMA was observed. As(V), MMA, and DMA accounted for 4.2%, 29.5%, and 8.1%, respectively, of the P . janthinellum SM-12F4 cells. Some of the intracellular As(III) can be oxidated and methylated by these fungal strains and yield As(V), MMA, and DMA as products. [ABSTRACT FROM AUTHOR]

The effect of pH on available Cd in calcareous soils and culture substrate was studied by adding exogenous Cd and artificially adjusting the pH to create different pH conditions. It is expected to provide reference for the control of Cd pollution by adjusting pH. The cadmium chloride was added to the calcareous soil and culture substrate to make the total cadmium content 1.0 mg kg–1. The pH of soil and substrate was adjusted, and then the available cadmium content in soil and cultivation substrate was detected under different pH conditions. The content of available Cd in calcareous soil decreased with increasing pH in the range of pH 3.40 to 8.97, showing a significant negative correlation. At a pH range of 3.03 to 4.37, the available Cd content in the culture substrate increased significantly with increasing pH, while the available Cd content in the culture substrate at a pH range of 4.37 to 9.47 was not significantly different. [ABSTRACT FROM AUTHOR]

Abstract: Bioremediation of arsenic (As)-contaminated soil using microorganisms has been a focus of research because it is environment friendly and cost-effective. The As-resistant fungi Trichoderma asperellum SM-12F1, Penicillium janthinellum SM-12F4, and Fusarium oxysporum CZ-8F1 were exposed to 50mgl−1 of As(V), and the biotransformation of As and the concomitant variance of Eh and pH in the media were studied. Fresh weights of all three isolates increased and then decreased depended on cultivation period. After cultivation for 2 or 3days, the As(V) added to the media had been completely changed into As(III), whilst As(V) was predominate in fungal cells with concomitantly little As(III) during cultivation. After 15days, little monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA) besides of As(V) and As(III) were found in the cells of T. asperellum SM-12F1, and the total As content was the highest in cells of P. janthinellum SM-12F4 (about 41.5μg) according to the quantitative analysis of As speciation in cultures. Moreover, when cultivation period reached 3days, the Eh and pH in the media of T. asperellum SM-12F1 (312.5mV and 4.8), P. janthinellum SM-12F4 (411.1mV and 4.2), and F. oxysporum CZ-8F1 (269.4mV and 4.8) might not responsible for the reduction of As(V) based on the previous study. Therefore, it is speculated that import/export, reduction, and methylation of As are conducted in fungal cells. Future studies investigating the biochemical behaviour of fungi responding to As are needed to gain a better understanding of bioremediation of As-contaminated soils. [Copyright &y& Elsevier]

Abstract: Watermelon is susceptible to Fusarium wilt in successively mono-cropped soil. Pot experiments were carried out to investigate the effect of intercropping with aerobic rice on Fusarium wilt in watermelon. The tested soil was classified as a loam soil, previously planted with watermelon and collected from Hexian county, Anhui province, China. The results obtained are listed as follows: (1) 66.7% of watermelon plants were infected with wilt disease and 44.4% died on 40 days after transplanting in mono-cropped soil, but plants were much less susceptible to infection when intercropped with rice; (2) the density of Fusarium oxysporum f. sp. niveum decreased by 91% in soil from the intercropped watermelon rhizosphere when compared with that from the mono-crop 40 days after transplanting; (3) densities of bacteria and actinomycetes increased, but fungal density decreased in rhizosphere soil from the intercrops in comparison with the mono-crop control; (4) compared to the control, the germinated Fusarium spores were decreased by 41.0% in the treatment with addition of 1.5ml rice root exudates. Adding 20ml of root exudates decreased Fusarium spore production by 76.4%; and (5) the activities of defense enzymes in the leaves and roots of watermelons in the intercropped system were significantly lower than those in the mono-cropped system. It is suggested that intercropping with aerobic rice alleviated Fusarium wilt in watermelon, by restraining the spore production of Fusarium and by changing the microbial communities in rhizosphere soil through the production of rice root exudates. [Copyright &y& Elsevier]

During the aging process, ferrihydrite was transformed into mineral mixtures composed of different proportions of ferrihydrite, goethite, lepidocrocite and hematite. Such a transformation may affect the fixed ability of arsenic. In this study, the stability of Fe-As composites formed with As(V) and the minerals aged for 0, 1, 4, 10 and 30 days of ferrihydrite were systematically examined, and the effects of molar of ratios Fe/As were also clarified using kinetic methods combined with multiple spectroscopic techniques. The results indicated that As(V) was rapidly adsorbed on minerals during the initial polymerization process, which delayed both the ferrihydrite conversion and the hematite formation. When the Fe/As molar ratio was 1.875 and 5.66, the As(V) adsorbed by ferrihydrite began to release after 6 hr and 12 hr, respectively. The corresponding release amounts of As(V) were 0.55 g/L and 0.07 g/L, and the adsorption rates were 92.43% and 97.50% at 60 days, respectively. However, the As(V) adsorbed by the transformation products aged for 30 days of ferrihydrite began to release after adsorbed 30 days. The corresponding release amounts of As(V) were 0.25 g/L and 0.03 g/L, and the adsorption rates were 84.23% and 92.18% after adsorbed 60 days, for the Fe/As=1.875 and 5.66, respectively. Overall, the combination of As(V) with ferrihydrite and aged products transformed from a thermodynamically metastable phase to a dynamically stable state within a certain duration. Moreover, the aging process of ferrihydrite reduced the sorption ability of arsenate by iron (hydr)oxide but enhanced the stability of the Fe-As composites. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Forward osmosis membrane has shown great potential in the fields of seawater desalination and sewage treatment. However, the concentration polarization phenomenon and membrane fouling in the water treatment process greatly reduce the water treatment performance and restrict its application. To address these challenges, we employed a pre-buried seed-in-situ growth method to facilitate the Zn–Al layered double hydroxide (Zn–Al LDH) growth on the thin nanofiber membrane, and use it as the support layer for the preparation of a Zn–Al LDH modified forward osmosis membrane. Studies have shown that the introduction of Zn–Al LDH significantly improves the water treatment efficiency of the forward osmosis membrane (In Al-DS mode, the water flux increased by 87.5 %, up to 50.50 LMH, with a low specific salt flux of 0.13 g L−1). It also exhibits exceptional antibacterial, anti-membrane fouling, and photocatalytic degradation properties. This research presents a novel approach for the development of advanced high-efficiency forward osmosis membranes. [Display omitted] • The in-situ growth of Zn–Al LDH on the nanofiber membrane was realized. • FOMs have ultra-high water flux and low reverse salt flux. • FOMs has excellent antibacterial, Anti-membrane fouling and photocatalytic ability. [ABSTRACT FROM AUTHOR]

The composition of organic carbon molecules (OCMs) impacts microbial diversity and in turn regulates the microbial transformation of elements in soils. However, the potential association of OCMs characteristics with arsenic methylation mediated by arsenite S-adenosylmethionine (SAM) methyltransferase gene (arsM)-harboring microbes in paddy soils remains unclear. Here, we investigated the impacts of OCMs on microbial methylators and arsenic methylation by identifying OCMs with Fourier transform ion cyclotron resonance mass spectrometry. The results showed that arsenic methylation efficiency increased by 57.4–260.1% in pig manure- or rice straw-treated paddy soils compared to the control. Molecules containing carbon, hydrogen, oxygen, and nitrogen (CHONs) with the atomic oxygen to carbon ratio (O/C) ranging from 0.5 to 0.8 had a more significant correlation (p < 0.01) with the abundance of the arsM gene than with that of 16S rRNA. This was confirmed by a significant positive correlation (p < 0.001) between consumed CHONs with O/C of 0.5–0.8 and increased methylated arsenic. CHONs (with O/C of 0.5–0.8) increased the intracellular SAM concentration and methyltransferase activity, stimulating arsenic methylation in vivo. The specialization of arsM -harboring taxa in CHONs with different O/C were identified. These observations provide a basis for predicting the risk of straight-head disease in paddy soils. [Display omitted] • Microbial arsenic methylation in paddy soils is regulated by OCMs. • Priming effects of CHONs with O/C of 0.5–0.8 on arsenic methylation was found. • Increased SAM concentration and ArsM activity in methylators stimulate arsenic methylation. • Specialization of arsM -harboring taxa in CHONs with different O/C were identified. [ABSTRACT FROM AUTHOR]

Due to high ionic conductivity and low cost, Li1.4Al0.4Ti1.6(PO4)3 (LATP) has emerged as a promising solid‐state electrolyte for next‐generation lithium (Li) metal solid‐state batterie with high safety performance and energy density. However, the extremely high impedance and surface instability of LATP with Li metal retard its practical application. Herein, a novel method is proposed to construct an ultrathin ZnO layer that is tightly coated on the LATP pellets, surface (ZnO@LATP) via magnetron sputtering, which in situ reacts with Li to form a low electronic conductivity and multifunctional solid electrolyte interphase (SEI). The formed SEI can not only effectively lower the interfacial resistance, but also overcome the side reactions of LATP with the Li metal anode and suppress the Li dendrite growth. Specifically, the interface resistance decreases from 80 554 to 353 Ω and the overpotential reduces from 1 V to 20 mV. As a result, the Li/ZnO@LATP@ZnO/Li symmetric batteries can stably cycle for more than 2000 h without short circuit at 0.05 mA cm−2 and Li/ZnO@LATP/LiFePO4 batteries show excellent cycle stability for 200 cycles at 0.1 C. This work highlights the significance of multifunctional interphase between LATP and Li metal for improvement of interfacial impedance and instability. [ABSTRACT FROM AUTHOR]

The garnet electrolyte presents poor wettability with Li metal, resulting in an extremely large interfacial impedance and drastic growth of Li dendrites. Herein, a novel ultra‐stable conductive composite interface (CCI) consisting of LiySn alloy and Li3N is constructed in situ between Li6.4La3Zr1.4Ta0.6O12 (LLZTO) pellet and Li metal by a conversion reaction of SnNx with Li metal at 300 °C. The LiySn alloy as a continuous and robust bridge between LLZTO and Li metal can effectively reduce the LLZTO/Li interfacial resistance from 4468.0 Ω to 164.8 Ω. Meanwhile, the Li3N as a fast Li‐ion channel can efficiently transfer Li ions and give their uniform distribution at the LLZTO/Li interface. Therefore, the Li/LLZTO@CCI/Li symmetric battery stably cycles for 1200 h without short circuit, and the all‐solid‐state high‐voltage Li/LLZTO@CCI/LiNi0.5Co0.2Mn0.3O2 battery achieves a specific capacity of 161.4 mAh g−1 at 0.25 C with a capacity retention rate of 92.6 % and coulombic efficiency of 100.0 % after 200 cycles at 25 °C. [ABSTRACT FROM AUTHOR]

The garnet electrolyte presents poor wettability with Li metal, resulting in an extremely large interfacial impedance and drastic growth of Li dendrites. Herein, a novel ultra‐stable conductive composite interface (CCI) consisting of LiySn alloy and Li3N is constructed in situ between Li6.4La3Zr1.4Ta0.6O12 (LLZTO) pellet and Li metal by a conversion reaction of SnNx with Li metal at 300 °C. The LiySn alloy as a continuous and robust bridge between LLZTO and Li metal can effectively reduce the LLZTO/Li interfacial resistance from 4468.0 Ω to 164.8 Ω. Meanwhile, the Li3N as a fast Li‐ion channel can efficiently transfer Li ions and give their uniform distribution at the LLZTO/Li interface. Therefore, the Li/LLZTO@CCI/Li symmetric battery stably cycles for 1200 h without short circuit, and the all‐solid‐state high‐voltage Li/LLZTO@CCI/LiNi0.5Co0.2Mn0.3O2 battery achieves a specific capacity of 161.4 mAh g−1 at 0.25 C with a capacity retention rate of 92.6 % and coulombic efficiency of 100.0 % after 200 cycles at 25 °C. [ABSTRACT FROM AUTHOR]

Ferrihydrite has been prevalently used in soil remediation as an effective amendment for in situ immobilization of arsenic (As). However, its poorly crystalline structure is unstable and can pose the risk of re-releasing As into soil. In this study, sequential extraction was coupled with a newly-established method, chelex-metsorb diffusive gradient in thin films (DGT), to study the ferrihydrite transformation/dissolution process and its effect on the mobility of arsenic in soil. Experiments in this work found that high soil moisture (70% SWHC) with a low soil redox potential (Eh) can significantly increase the rate of the ferrihydrite transformation/dissolution process compared to 30% SWHC. Soils with low pH and high available iron (Fe) content may also accelerate ferrihydrite transformation/dissolution, while soils with high clay fraction and high soil total organic matter (STOM) may inhibit the process. The amount of arsenic adsorption can also affect ferrihydrite transformation, even exceeding the effect of soil pH and dissolved Fe. Arsenic release was clearly observed in all three soils across all treatments, and it was also affected by changes in soil redox potential. More arsenic was released at high soil moisture (70% SWHC) roughly 7–15 d after the release of Fe. In addition, a partial arsenic fraction was transformed, along with ferrihydrite, from a combined As (F1 As) amorphous phase to combined As (F2 As) well-crystallized phase. These results suggested that ferrihydrite transformation/dissolution can affect the mobility of arsenic and that this phenomenon is more extreme at higher soil moisture levels. Unlabelled Image • Soil redox condition significantly regulated the ferrihydrite transformation/dissolution process. • Ferrihydrite transformation rate in soils was also controlled by the soil properties and amount of arsenic adsorption. • Ferrihydrite transformation/dissolution may lead to a short time release of the labile As. • Labile As release had a strong correlation with Fe(II) release. • Arsenic fractionation was also transformed with transformation of ferrihydite. [ABSTRACT FROM AUTHOR]

Despite low fertility and content of organic carbon in albic black soil, grains are grown in this type of soil in the northeast plain of China in order to find ways to improve the soil's fertility and crop production. We carried out pot experiments of maize applied with one of three different treatments of fulvic acids (FA) derived from different parent materials: Plant-derived solid (PDSF), mineral-derived liquid (MDLF), and plant-derived liquid (PDLF) applied at respective rates of 2.5, 5, and 5 g kg−1 as well as a control applied at 0 g kg−1. The results showed that soil organic carbon and light fraction C was greater by 29% to 21% and 38% to 21%, respectively, among the treatments compared to that of the control. Similarly, available N content was significantly greater in the PDLF treatment, and P content was also significantly greater in the PDSF treatment. In contrast, available K and extractable Mg contents were lower, as well as organic–inorganic degree complexes and organic–inorganic composites in the PDSF, MDLF, and PDLF treatments compared with those of the control. Further results showed that MDLF and PDLF Fulvic acids (FA) accelerated plant growth, while PDSF limited plant growth. Our study provides empirical evidence that addition of fulvic acid from MDLF and PDLF had more positive effects on soil properties and plant growth than fulvic acid from PDSF. This investigation suggests that application of fulvic acid in liquid form can improve nutrient availability and affect other important chemical, biological, and physical properties of soils. [ABSTRACT FROM AUTHOR]

Abstract Soil samples from the Hexi Corridor located in the arid regions of Northwestern China were collected from a 24–year–old field experiment. The distribution of organic carbon (OC) in the different size water stable aggregate (WSA) fractions and the stability mechanism of OC in WSA size fractions were studied. The results showed that long-term application of solo organic manures or in combination with inorganic N fertilizer significantly increased the OC concentrations of different size WSA fractions compared to the CK, while long-term application of solo N fertilizer had no significant effect. After fertilization for 24 years, the OC concentrations of 0.25–2 mm WSA fraction was significantly positively correlated with the percentages of this WSA fraction, while the OC concentrations of >2 mm, 0.053–0.25 mm and <0.053 mm were not significantly correlated with their corresponding percentages of WSA fractions (P > 0.05). In addition, the OC concentrations of loosely, stably and tightly bound humus in 0.25–2 mm WSA fraction were significantly higher than those in other size WSA fractions, which were also significantly correlated with the corresponding chemical components, e.g. different forms of calcium, in 0.25–2 mm WSA fraction (P < 0.05). It could be explained that affinities of OC to chemical components in 0.25–2 mm WSA fraction were stronger than those in other size WSA fractions. The results of NMR analysis also showed that the aromaticity and alkyl/O-alkyl ratio for the 0.25–2 mm WSA fractions were significantly lower than those for other size WSA fractions (P < 0.05). These results demonstrated that the 0.25–2 mm WSA fraction played an important role in stabilizing soil OC and protecting OC from degradation in the irrigated desert soil. Highlights • The affinity of OC to chemical components in 0.25–2 mm WSA fraction was stronger. • 13C NMR spectra were used to estimate the OC stability in WSA size fractions. • 0.25–2 mm WSA fraction plays an important role in stabilizing soil OC. • The results could be valuable for protecting irrigated desert soil from erosion. [ABSTRACT FROM AUTHOR]

Ferrihydrite is commonly used as an amendment to remove or stabilize arsenic (As) in water, soils, and sediments due to its high specific surface area (>200 m 2 /g). However, its instability under oxic or anoxic conditions sometimes limits its efficiency for arsenic adsorption. This study employed a two-step sequential extraction method and the diffusive gradients in thin films (DGT) technique to investigate the effect of soil properties and water management on ferrihydrite transformation in soils. The results of sequential extraction and DGT indicated that ferrihydrite transformation and dissolution occurred within all treatments in three red soils derived from plate shale (PS), sandstone (SS) and quaternary red clay (QR). Ferrihydrite transformation and dissolution rate under 30% soil water holding capacity (SWHC) treatments were the fastest in PS followed by SS and QR, while in 70% SWHC treatments the order was SS > PS > QR. Ferrihydrite in 70% SWHC was transformed about 2–7 times faster than in 30% SWHC for the various treatments. The soil pH may be the main factor controlling ferrihydrite transformation in 30% SHWC, and in 70% SHWC it may work synergistically with Fe(II) as a result of continuous, partial anaerobic conditions formed after about 22 days. Variation among the three soils was controlled by different amounts of soil total organic matter, pH, available Fe, and the content of clay fraction (particulate size <0.02 mm). In the present study, SWHC was expected to be the direct factor controlling ferrihydrite transformation and dissolution process. However, the factor controlling these processes was actually variation in soil moisture, which promotes the dissolution of H + solutes and formation of Fe(II) in partial anaerobic conditions. The results obtained in this study have demonstrated the potential of using ferrihydrite on contaminated farmland as an amendment for arsenic stabilization. [ABSTRACT FROM AUTHOR]

The effect of exogenous phosphate (P, 200 mg⋅kg −1 soil) on the lability and phytoavailability of arsenic (As) was studied using the diffusive gradients in thin films (DGT) technique. Lettuce were grown on the As-amended soils following the stabilization of soil labile As after 90 days incubation. Phosphate (P) application generally facilitated plant growth except one grown on P-sufficient soil. Soil labile As concentration increased in all the soils after P application due to a competition effect. Plant As concentration increased in red soils collected from Hunan Province, while decreases were observed in the other soils. Even though, an overall trend of decrease was obtained in As phytoavailability along with the increase of DGT-measured soil labile P/As molar ratio. The functional equation between P/As and As phytoavailability provided a critical value of 1.7, which could be used as a guidance for rational P fertilization, thus avoiding overfertilization. [ABSTRACT FROM AUTHOR]

Although specific soil properties controlling the arsenic (As) aging process have been studied extensively, few investigations have attempted to determine how soil types influence As bioavailability and fractionations in soils. Nine types of soil were selected from typical grain producing areas in China, and the bioavailability and fractionations of As during aging were measured. Results showed that available As in all soils rapidly decreased in the first 30 days and slowly declined thereafter. In spiked soils, As easily became less available and less toxic in low pH soils compared to high pH soils, demonstrating the importance of soil pH on As availability. Results from fitting kinetic equations revealed that the pseudo-second-order model described the As aging processes well in all soils ( R 2 = 0.945–0.999, P < 0.01, SE = 0.09–4.25), implying that the mechanism for As aging combined adsorption, external diffusion, and internal diffusion. Fe oxides were more important than Al oxides for determining the As aging rate (| k |). Based on these results, we are the first to propose the approximate aging equilibrium time ( T ) for As, which was mainly influenced by soil clay content. The shortest time for approximate stabilization of As aging was 28 d in latosol soils (LS), while the longest approximate equilibrium time was 169 d in cinnamon soils (CS). Individual soil properties controlling the variation in different As fractionations further confirmed that the influences of soil types on As aging were the result of the combined effects of soil properties and a time-consuming redistribution process. [ABSTRACT FROM AUTHOR]

Bacteria capable of arsenate [As(V)] reduction can be used for remediation of As-contaminated soils via bio-extraction. In this study, As-resistant bacteria were isolated and their abilities to resist and reduce As(V) as well as As bio-extracted from soils naturally contaminated with As were studied. The results indicated that three isolates (2-2, 4-3, and 8-5) showed greater abilities to resist As(V) than other isolates. When the isolates were exposed to 10 mg L As(V), As(V) contents decreased, while arsenite [As(III)] increased over time. In comparison, isolates 2-2 and 4-3 completely reduced As(V) into As(III) within 6 h. According to phylogenetic analysis of the 16S rRNA gene, isolates 2-2, 4-3, and 8-5 were most closely related to Pseudomonas taiwanensis, P. monteilii, and Pseudomonas sp., respectively. Total As contents in soils significantly ( P < 0.05) decreased after bacterial extraction. The maximum As removal of 21.6% was observed following inoculation of isolate 2-2 into soil-1. Bacterial extraction weakened the binding between As and the soil solid phase, resulting in As removal from the soil. [ABSTRACT FROM AUTHOR]

Hydrous ferric oxide (HFO) is most effective with high treatment capacity on arsenate [As(V)] sorption although its transformation and aggregation nature need further improvement. Here, HFO nanoparticles with carboxymethyl cellulose (CMC) or starch as modifier was synthesized for the purpose of stability improvement and As(V) removal from water. Comparatively, CMC might be the optimum stabilizer for HFO nanoparticles because of more effective physical and chemical stability. The large-pore structure, high surface specific area, and the non-aggregated nature of CMC-HFO lead to increased adsorption sites, and thus high adsorption capacities of As(V) without pre-treatment (355 mg·g−1), which is much greater than those reported in previous studies. Second-order equation and dual-mode isotherm model could be successfully used to interpret the sorption kinetics and isotherms of As(V), respectively. FTIR, XPS and XRD analyses suggested that precipitation and surface complexation were primary mechanisms for As(V) removal by CMC modified HFO nanoparticles. A surface complexation model (SCM) was used to simulate As adsorption over pH 2.5-10.4. The predominant adsorbed arsenate species were modeled as bidentate binuclear surface complexes at low pH and as monodentate complexes at high pH. The immobilized arsenic remained stable when aging for 270 d at room temperature. [ABSTRACT FROM AUTHOR]

The co-existence of antibiotics and heavy metals in soil with manure application poses high risk to both environment and human health, and thus effective remediation methods are in urgent need. This study investigated the synergistic effects of electrokinetic remediation (EKR) on antibiotic resistance and arsenic (As) in co-contaminated paddy soils. EKR treatments in soil amended with pig manure (EKR-PD) showed better remediation efficiency compared with that without pig manure. In detail, the content of available As and the abundance of antibiotic-resistant bacteria (ARB) decreased by 25.2 %−41.4 % and 9.5 %−21.1 % after 7-d remediation, respectively, due to a relatively higher current density for EKR-PD. The role of the electric field contributed to 33.9 % of antibiotic degradation. Antibiotic resistance genes (ARGs) with ribosomal-protection and enzymatic-deactivation types were easier to remove, with the removal ratio of 37.8 %−41.6 % in EKR-PD. Brevundimonas was the most significantly different species during remediation. Bacillus and Clostridium_ sensu_stricto_1 were potential host bacteria of ARGs in the electric field. Membrane transport might be an effective strategy for microorganisms to respond to the stress of both electric field and co-contaminated environments. This study supports the potential role of EKR in the co-contamination of heavy metals and antibiotic resistance under manure application. [Display omitted] • Manure application enhanced the resistance of soil microbes to the electric field. • Higher removal of antibiotics-arsenic occurred in manure-applied EKR. • Brevundimonas was the most significantly different species among treatments. • Potential ARGs host bacteria were judged in the OTC-As soil during EKR. • Membrane transport related with resistance to OTC-As and electric field. [ABSTRACT FROM AUTHOR]

Arsenic (As) and cadmium (Cd) are two highly toxic elements. In recent years, many newly synthesized chemical materials have been used widely for treatments of As- and Cd-contaminated effluents. However, most materials do not exhibit high efficiencies for simultaneous removal of As and Cd from water systems. Our study established a simple scheme for synthesizing a sepiolite (SEP)-modified nanoscale zero-valent iron (S-nZVI) for simultaneous removal of coexisting As and Cd from water and illuminated a possible underlying mechanism. Batch experiments showed that the maximum capacities for adsorption of As(III) and Cd(II) by S-nZVI were 230.29 mg/g and 11.37 mg/g, respectively, which represented better effects than those of other materials, as reported previously. Removal of Cd(II) depended on pH, but As(III) removal showed little dependence on pH. Coexisting ions such as phosphate (PO 4 3−) and the conjugate base of humic acid (HA) significantly inhibited simultaneous removal of As(III) and Cd(II). In the mixed As(III)–Cd(II) system, the presence of As(III)-pretreated S-nZVI significantly enhanced Cd(II) adsorption by a factor of four over that seen for aqueous solution without As(III). XRD and XPS results showed that CdFe 2 O 4 (Fe–O–Cd), Fe 2 As 2 O 14 or FeAsO 4 (Fe–O–As) were formed after As(III) and Cd(II) were captured by S-nZVI. However, a further zeta (ζ) potential analysis showed that the mechanism for As(III) and Cd(II) adsorption by S-nZVI is not just simple formation of the above chemicals, since the adsorbed As(III) increased the negative charge of S-nZVI; this suggested an electrostatic attraction between S-nZVI and Cd(II) and indicated that adsorbed As(III) created new sorption sites for Cd(II), which enhanced Cd(II) sorption via formation of ternary complexes (Fe–As–Cd). These results suggested that S-nZVI is a promising material for in situ remediation of heavy metal-contaminated groundwaters or paddy soils. • A newly sepiolite modified nZVI was synthesized for co removal of As(III) and Cd(II). • S-nZVI has high sorption efficiency of As(III) and Cd(II). • Pre-treatment with As(III) can significantly promote Cd(II) adsorption by S-nZVI. • The mechanism of As–Cd co-removal is suggested by forming a ternary complex Fe–As–Cd. [ABSTRACT FROM AUTHOR]

Soil samples from the Hexi Corridor located at the arid regions of NW China were collected from a 23-y-old field experiment. Effects of fertilization on soil organic C (SOC) fractions and the distribution of added OC in the different SOC fractions were studied. The results showed that the long-term applications of sole organic manures or in combination with inorganic N fertilizer significantly ( P < 0.05) increased the OC stocks in the particulate organic matter (POM), light fraction organic matter (LFOM), and heavy fraction organic matter (HFOM) by 24.8-159.6%, 55.2-224.4%, and 6.2-57.8%, respectively, compared to the non-fertilized treatment (CK). The average OC stock in the HFOM was higher than those of the POM and LFOM, and the conversion rate of the added OC to the OC stock of the HFOM was also higher than those of the POM and the LFOM, showing that SOC was mainly sequestrated in the HFOM. The increase of OC stock in the HFOM resulted in the increase of OC stocks in the loosely bound humus, stably bound humus, and tightly bound humus. The OC stocks in the loosely, stably, and tightly bound humus accounted averagely for 16, 19, and 65% of the OC stock in the HFOM. Furthermore, the conversion rates of the added OC to the OC stocks of loosely, stably and tightly bound humus were 2.3%, 1.5%, and 5.5%, respectively. Additionally, a significant ( P < 0.01) positive linear correlation was found between the annually added OC amounts and the C sequestration rate. These results indicated that tightly bound humus was the most important component for OC sequestration in the irrigated desert soils of the Hexi Corridor and that SOC is not saturated in this region. [ABSTRACT FROM AUTHOR]

The performances of passivation materials mitigating Cadmium (Cd) bioavailability considerably vary with the pH condition of Cd-contaminated soils. However, less information was available for the method of improving Cd passivation efficiency taking into account the pH of the targeted soil. Furthermore, the underlying mechanism of Cd availability mitigation in soils with different pH has not been clearly explored. In this study, cotton straw biochar (CSB) and its modified products using NaOH (CSB–NaOH) were prepared and applied in two kinds of Cd-contaminated soils with different pH. It was found that CSB-NaOH was more effective than CSB in regulating the Cd bioavailability in the acid soil, while the opposite tendency was observed in alkaline soil. The difference of the Cd passivation efficiency is correlated with contributions of various Cd-biochar binding mechanisms, which cation exchange mechanism is largely eliminated for CSB-NaOH. The interaction of Cd with CSB/CSB-NaOH was further evidenced through characterization results of Scan Electron Microscopy (SEM), X-Ray Diffraction (XRD), Fourier-transformed infrared spectroscopy (FTIR) and X-ray Photoelectron spectroscopy (XPS). Characterization results proved that carboxyl, hydroxyl and ethyl groups were the key functional groups involved in Cd passivation. XPS results showed that Cd binding methods varied between CSB and CSB-NaOH, which Cd2+ and Cd–O were the main form of Cd binding to CSB while Cd–O was the main form on CSB-NaOH. In this work, it was demonstrated that in acid soil, pH change caused by biochar plays a more significant role in controlling the Cd bioavailability, while in alkaline soil, the strength of the Cd-biochar interaction is more decisive for the Cd passivation efficiency. This work provides information on how to select the suitable passivator to decrease the Cd bioavailability in terms of different soil pH and property. [Display omitted] • CSB and CSB-NaOH demonstrated different effects on available Cd mitigation. • Contribution of ion exchange reduced from 68.1% for CSB to 25.4% for CSB-NaOH. • pH raising accounted for 37–56% and 13–15% of DGT-Cd lowering in acid/basic soil. • CSB-NaOH led to 0.6 units of pH raising and 49.7% of DGT-Cd reducing in basic soil. • Contributions of Cd binding mechanisms differ with CSB and CSB-NaOH.". [ABSTRACT FROM AUTHOR]

The simultaneous mitigation of toxic arsenic (As) and cadmium (Cd) in rice grain remains a global challenge. The over-accumulation of husk dimethylarsinic acid (DMAs) induces the rice straight-head disease, which threatens rice production worldwide. In this study, we investigated various soil ridge height treatments with Eh ranging from − 225–87 mV and pH ranging from 6.3 to 4.1. Soil ridge cultivation can maintain grain As and Cd at low levels for slightly co-contaminated paddy soils, especially when the ridge height is 11 cm (Eh of 43 mV and pH of 4.6), where grain inorganic As decreased—at maximum—by 48% and DMAs by 55%. Grain Cd (0.14 mg kg−1) increased but was still below the limit (0.2 mg kg−1) in China, and the cost of ridging is acceptable. There were definite correlations among porewater As, Cd, Fe, S, and Mn contents across various Eh and pH values. Soil ridge cultivation significantly (P < 0.05) diminished the copy number of As-reducing (harboring arsC and arrA), As-methylating (harboring arsM), and sulfate-reducing (harboring dsrA) bacteria. Moreover, soil ridge cultivation shifted the arsM -harboring microbiota. In response to ridge height increase, the abundance of the bacterial biomarker phylum Euryachaeota declined and the families Halorubrum and Planctomyces were gradually replaced by Sandaracinus in paddy soil. [Display omitted] • Soil ridge cultivation as an old agronomic measure practiced 2000 years ago. • Soil Eh and pH varying in a large range was set up by various ridge heights. • 11 cm ridge height helps to simultaneously control grain As and Cd at a low level. • Soil ridge cultivation reduced grain DMAs by inhibiting soil As methylation. • The abundance and composition of arsM -harboring microbiota shifted after ridging. [ABSTRACT FROM AUTHOR]

The strong ability of ferrihydrite and its aged minerals for fixing arsenate is a key factor in remediating arsenate-polluted environments. It is therefore crucial to clarify the stability of Fe–As complexes and the release conditions for As(V). The As(V) release amount was evaluated and compared in the presence of six representative anions, namely, phosphate, silicate, sulfate, inositol hexaphosphate, citrate, and oxalate. It was found that the As(V) release amount changed with the aging time of ferrihydrite and that this tendency generally followed two rules. These are, longer aging time leads to lower As(V) release (Rule 1), and longer aging time leads to higher As(V) release (Rule 2). Whether Rule 1 or Rule 2 dominated As release depended on the number of surface groups, size of competing anions, and contribution of As(V) re-adsorption. Characterization results using X-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) provided evidence for the predicted mechanisms of As(V) release under various circumstances. In this work, it was demonstrated that when inorganic anions such as sulfate and silicate are present, ferrihydrite with longer aging time led to decreased As(V) release. When organic anions are present, ferrihydrite with less aging time results in reduced As(V) leaching. For anions such as phosphate, the As(V) release amount in relation to the ferrihydrite aging time depends on the concentration of phosphate ions. Nevertheless, the ligand concentration and As(V) loading rate on ferrihydrite should be simultaneously considered for the rule governing As(V) releasing. [Display omitted] • 2 rules were indicated for As release amount changing with ferrihydrite aging time. • As leaching was evaluated with influence of an entire range of representative ions. • Factors such as ion concentration and As loading rate affect As release tendency. • Optimal pre-aging time of ferrihydrite was suggested for As(V) fixation. [ABSTRACT FROM AUTHOR]

• Long-term manure application improved soil fertility and Ca/Mg availability. • SOC is mainly stored in large aggregates and microaggregates. • Aromatic alcohols are mainly enriched in silt–clay minerals. • Manure application enhances the stability of aggregates and associated carbon. • High pH limits the stability of aggregates and aggregate-associated carbon. The response to climate change through soil organic carbon sequestration has received increased interest. While soil organic carbon sequestration is related to the stability of aggregates and aggregate-associated carbon and varies among fertilization practices, little information is available on how fertilization practices impact the stability of aggregates and aggregate-associated carbon in alkaline soil. Using a 13-year field experiment with three replicate plots of four fertilization practices (only chemical fertilizer application, only manure application, 50% chemical fertilizer and 50% manure application, and 100% chemical fertilizer and 100% manure application) and one control treatment (nonfertilization), we investigated the correlations between 20 soil physicochemical factors and stability indices of aggregates and aggregate-associated carbon under the influence of long-term fertilization. Fertilization with manure not only significantly improved soil physicochemical characteristics, such as increasing conductivity, the cation exchange capacity, organic carbon, and the availability of nutrients and calcium/magnesium, but also enhanced mean weight diameter, geometric mean diameter and large aggregate- and microaggregate-associated carbon. Soil organic carbon was more abundant in large aggregates and microaggregates than in other fractions, and the carbonyl group bands in large aggregates were wider than those in other fractions. Mean weight diameter, geometric mean diameter and large aggregate- and microaggregate-associated carbon were positively correlated with the total amounts and availabilities of soil nutrients and free and exchangeable calcium/magnesium and were negatively correlated with soil pH, likely because fertilization with manure enhanced the stability of aggregates and aggregate-associated carbon by increasing the availability of soil nutrients and calcium/magnesium ions, while high pH limited the stability of aggregates and aggregate-associated carbon. Strategies aiming to improve alkaline soil and increase soil C stocks may thus focus on manure or fertilizer application with the ability to reduce soil acidity. [ABSTRACT FROM AUTHOR]

Agricultural planning via substitution with crops of low arsenic (As) accumulation can efficiently reduce the dietary exposure from As to human health through food chain. In this study, in total 157 crop cultivars, including rice, vegetable and maize, were used and their risk of As accumulation in edible parts was studied via pot and field experiments. When soil As level was 56.7 mg kg−1, equivalent to a level of slight contamination, inorganic As (iAs) in rice grain ranged from 0.44 to 0.61 mg kg−1 Fresh weight (FW), which was 2.2–3.0 times higher than its limit in China (0.2 mg kg−1). When soil As enhanced to 156.2 mg kg−1 (moderate contamination), mater convolvulus and crown daisy had the over-limit risk of As accumulation in their edible parts. Green tender, pakchoi cabbage, rape and amaranth emerged with the over-limit risk of As, when soil As reached 238.3 mg kg−1 (severe contamination). Comparatively, maize and tuber or fruit vegetables had the lower levels of As in their edible parts and sweet potato, peanut, pepper and potato had less variation of As accumulation among cultivars of the same crop. A recommended list was provided for preferable food crops under different contamination level of As in soils. Switching paddy soil into upland soils and planting in priority with tuber or fruit vegetables and maize are encouraged. Agricultural planning resulted in significant decreases for the target hazard quotient (THQ) and target cancer risk (TCR) of iAs via dietary exposure to the residents near the realgar mine in Shimen County of China. [Display omitted] • 7-year field experiments were conducted by employing 157 cultivars or varieties of food crops. • Arsenic accumulation in food crops under different degree of soil contamination was investigated. • Food crops in priority with tuber or fruit vegetables and maize was strongly suggested. • Agricultural planning resulted in significant decrease in human dietary exposure to As. [ABSTRACT FROM AUTHOR]

Soil management and cultivar selection are two strategies to reduce the accumulation risk of heavy metals in crops. However, it is still an open question which of these two strategies is more efficient for the safe utilization of contaminated soil. In this study, the available bio-concentration factors (aBCF) of arsenic (As) and cadmium (Cd) among 39 maize cultivars were determined through a field experiment. The effect of soil management was mimicked by choosing diverse sampling sites having different soil available contents of As and Cd. The aBCF of As and Cd in grain ranged from 0.02 to 0.13 and 1.17 to 42.2, respectively. The accumulation ability of As and Cd was classified among different maize cultivars. Soil pH and total As controlled the level of available As in soils, while soil pH dominated available Cd in soil. A soil pH of 6.5 was recommended to simultaneously minimize soil available As and Cd by managing soil conditions. The quantitative effects of cultivar and soil management on grain As and Cd were expressed as Q [Grain As] = 0.746 Q [Cultivar]-0.126 Q [pH]+0.276 Q [As available ] (R2 = 0.648, P = 1.00 × 10−37) and Q [Grain Cd] = 0.913 Q [Cultivar]-0.192 Q [pH]+0.071 Q [SOC] (R2 = 0.782, P = 1.00 × 10−37), respectively. Cultivar selection contributed stronger than soil management to decrease the As and Cd levels in maize grains. A feasible method to seek for a more efficient strategy was proposed for the safe utilization of contaminated soil. [Display omitted] • 39 maize cultivars used to reflect the effects of cultivar on As/Cd accumulation. • Difference in soil available As/Cd well mimicked the effect of soil management. • Maize cultivars were classified based on their accumulation abilities of As/Cd. • Maize cultivar contributes stronger than soil management in this case study. • A method seeking for a more efficient strategy for safe utilization of contaminated soil was proposed. [ABSTRACT FROM AUTHOR]

[Display omitted] • Investigate soil properties in paddy soils for different fertilization treatments. • DIN leaching positively correlate with soil-surface electrochemical properties. • Continuous organic fertilization may decrease early DIN leaching in paddy soils. • Soil-surface electrochemical properties may predict soil ion migration. Dissolved inorganic nitrogen (DIN) adsorbed onto soil colloids plays an important role in soil N leaching, but previous studies have not clearly defined the mechanisms of this process in paddy soils under organic fertilization. In this study, we investigated how ongoing fertilization can change soil DIN leaching via affects on soil-surface electrochemical properties and physical properties, and the main influences of soil properties on DIN leaching were characterized. Five fertilization regimes applied during a 5-year field experiment were employed to study this mechanism, i.e., no fertilizer, chemical fertilizer, chemical fertilizer plus hog manure, hog manure, and chemical fertilizer plus oil cake. Increasing levels of applied manure decreased DIN leaching from the soil profile, especially for NH 4 +, the main form of DIN in the leachate and soil. Compared to chemical fertilizer, organic fertilization changed the surface electrochemical and physical properties more effectively with regards to decreased soil bulk density (9.84–20.49 %, P < 0.05) and specific surface area (26.38–44.88 %, P < 0.05), as well as enhanced water-holding capacity (19.05–42.86 %, P < 0.05) and the number and density of soil-surface charges (7.97.55–98.44 %, P < 0.05). Furthermore, organic fertilization significantly increased the NH 4 + adsorbed by soil. Structural equation modeling showed that soil-surface electrochemical properties had the greatest impact (β = –0.88, P < 0.05) on the NH 4 + content of the leachate when compared with the soil NH 4 + adsorption capacity and physical properties. The increase in the soil-surface charge, surface charge density, surface potential, and surface electric field strength under organic fertilization increased soil NH 4 + retention in soil (P < 0.001), and thus, these changes decreased the risk of NH 4 + leaching. Our results suggest that continuous substantial organic fertilization may mainly decrease early DIN leaching from cultivated paddy soils in the Dongting Lake area by altering soil-surface electrochemical properties, where soil-surface electrochemical properties can be set as an internal factor to predict soil ion migration in agriculture systems, such as the Dongting Lake area or other similar regions. [ABSTRACT FROM AUTHOR]

• Extracellular bonding and intracellular detainment confer As resistance of fungi. • Fungal cell wall contributed average 80 % of the total immobilized As by fungi. • The vacuole As accounted for average 55 % of the protoplast As in fungal cells. • Fungal septa is newly found to compartmentise or immobilize As. • GSH content is a reasonable indicator for As tolerance in fungal protoplast. Microbes play a crucial role in arsenic (As) biogeochemical cycling and show great potential for environmental detoxification and bioremediation. Efflux, transformation, and compartmentalization are key processes in microbial As resistance. However, organelle specific As detoxification and fate during intracellular transfer and compartmentalization is not well understood. We conducted a time course experiment (2–5 days) of the organelle separation for fungal strains to explore subcellular As distributions. After exposure to 10 mg L−1 of arsenate (As(V)), the As accumulation among fungal organelles was generally in the order of extracellular (65 %) > cell wall (15 %) > vacuole (10 %) > other organelles (8 %). The vacuole As accounted for 55 % of the protoplast As. Extracellular bonding and vacuole compartmentalization were the main mechanisms of As resistance in the fungal strains tested. Glutathione (GSH) increases in fungal protoplast in response to As toxicity, acting as a reasonable indicator of As tolerance. Fourier transform infrared (FT-IR) spectroscopy indicated that carboxyl and amines groups within fungal cell walls potentially bind with As preventing As influx. Further analysis using scanning transmission X-ray microscopy (STXM) identified that fungal septa besides vacuole could also immobilize As. [ABSTRACT FROM AUTHOR]

• DOM characteristics influence As methylation and biovolatilization in paddy soils. • Arsine production is markedly enhanced following pig manure DOM application. • Among DOMs, Pig manure DOM addition yields much higher As-methylation in paddy soil. • Pig manure DOM addition increases the OTU number of arsM -carrying bacteria. • High labile C amount is responsible for the enhanced As-methylation in paddy soils. The effect of dissolved organic matter (DOM), derived from composted pig manure or rice straw, on arsenic methylation and subsequent biovolatilization in paddy soils was investigated. Arsine production following pig manure DOM application was 2.7- and 9.6-fold higher than that of soils treated with rice straw DOM and the control, respectively. Trimethylarsine was the dominant arsine at 54 %, followed by dimethylarsine at 22 %, arsine at 21 %, and monomethylarsine at 3 %. The copy numbers of the total and As-methylating bacteria were significantly enhanced in paddy soils treated with DOM. Pig manure DOM altered soil bacterial profile by increasing the OTU number of As methylation-inducing bacteria, such as Proteobacteria, Bacteroidetes, Geobacter , Sphingomonas , Streptomyces , and Rhodopseudomonas , thereby promoting As volatilization and methylation in paddy soils. The higher relative content of alkyl-C, N-alkyl C, and carboxyl-C in pig manure DOM was responsible for the increase in total and arsM -carrying bacteria in paddy soils, leading to enhanced As methylation. These observations will promote a better understanding of the role of DOM in mediating As methylation and volatilization, along with how organic fertilization affects straighthead disorder of rice, a condition caused by methylated arsenic species. [ABSTRACT FROM AUTHOR]

• Arsenic is electrochemically adsorbed by birnessite from mining wastewater. • Electrochemical redox reactions of birnessite contribute to arsenic adsorption. • H 2 O 2 formation and high potential of birnessite anode facilitate As(III) oxidation. • Mn2+ in wastewater can also be effectively removed during arsenic adsorption. • Cell voltage reversal facilitates the continuous use of birnessite electrode. Manganese oxides have been extensively investigated for arsenic (As) adsorption from aqueous solution. However, the effect of electrochemical redox reactions on the adsorption performance and underlying mechanism remain elusive. Herein, birnessite was used for electrochemical adsorption of As from mining wastewater at a constant cell voltage, and the effect of cell voltage and the continuous use (without desorption) performance of birnessite electrode were also evaluated. At 1.2 V for 24 h, the concentrations of total As (As(T)) and As(III) in wastewater decreased from 3808.7 to 73.7 μg L−1 and 682.8 to 21.4 μg L−1, respectively. The As(T) removal ratio increased with increasing cell voltage and reached 98.1% at 1.2 V, which was higher than that at open circuit (84.1%). The Mn2+ concentration also significantly decreased in wastewater during As adsorption. The high potential of birnessite anode and the generation of H 2 O 2 on cathode facilitated As(III) oxidation, and the electrochemical redox reactions of birnessite contributed to the enhancement of As(T) removal. The application of cell voltage reversal could improve the utilization rate of birnessite electrodes by dissolution-recrystallization during continuous use, and the As(T) removal ratio was increased from 73.5% to 85.1% after five cycles of voltage alteration. The present work indicates that birnessite is a promising absorbent for the electrochemical adsorption of As from real wastewaters. [ABSTRACT FROM AUTHOR]