Nonlinearly coupled electro-osmotic flow in variable charge soils.

Electro-osmosis has been valued as a promising technology to enhance the dewatering of waste sludge, stabilization and environmental remediation of soils with low permeability. However, the coefficient of electro-osmotic permeability (keo) is commonly taken as constant value which is particularly not the case in variable charge soil. As a result, the nonlinearity of the electro-osmotic flow (EOF) and the direction reverse could not be interpreted. Herein, the electro-chemical parameters were monitored in electro-osmotic experiment with natural variable charge soil. It was observed that the evolutions showed significant nonlinear behavior and were correlated. The comprehensive Zeta potential model proposed by the authors was applied to simulate the nonlinear keo induced by the variable pH and electrolyte concentration. The agreement between tested and simulated flow rate variation and excess pore water pressure distribution demonstrated the reliability of the theory. The error rate of the simulations through coupling nonlinear keo and voltage gradient Ex was reduced to 29.4% from 381.9% of calculations with constant parameters. The direction reverse of EOF was innovatively interpreted. Hence, the numerical model would act as a useful tool to connect these electro-chemical parameters and provide guidance to evaluate contributions of commonly used pH conditioning measurements.

Transition in electronic and magnetic properties of transition metal embedded semimetallic B-graphyne.

Spintronics is extremely important in the future development of information technology. Notably, two-dimensional carbon materials with atomically thick and p-electron systems have great potential for application in ultrathin spintronic devices. B-graphyne (B-GY) is a recently proposed two-dimensional carbon allotrope with double Dirac cones. It is a promising nanomaterial for high-speed spintronic devices due to its ultra-high Fermi velocity and thermodynamic stability. We tune the electronic and magnetic properties of B-GY by doping 3d transition metals (TM) (Cr, Mn, Fe, Co, Ni) based on first-principles calculations. After doping, TM forms strong covalent bonds (Fe, Co, Ni) and ionic bonds (Cr, Mn) with adjacent C atoms. The system of TM-doped B-GY (TM@B-GY) is transformed from a semimetal for B-GY to a metal (Cr, Mn, Fe, Co), but Ni@B-GY is still semimetal. Among them, Co@B-GY is approximately a half-metal. Moreover, TM (except Ni) can induce the magnetism of B-GY to undergo spin splitting. The TM d-orbitals are strongly coupled to the C p-orbitals, which play an important role in inducing magnetism. The results show that the tunable electronic and magnetic properties of TM@B-GY are promising as a high-speed spintronic device. Our research helps advance the study of semimetallic carbon allotropes in the field of spintronics.

Mechanism of nitro-byproducts formation during persulfate-based electrokinetic in situ oxidation for remediation of anthracene contaminated soil.

Persulfate-based electrokinetic (EK) chemical oxidation appears to be a novel and viable strategy for the in situ remediation of polycyclic aromatic hydrocarbons (PAHs) polluted soil; however, the possible toxic byproducts of PAHs have been overlooked. In this study, we systematically investigated the formation mechanism of the nitro-byproducts of anthracene (ANT) during the EK process. Electrochemical experiments revealed that NH4+ and NO2- originating from nitrate electrolyte or soil substrates were oxidized to NO2• and NO• in the presence of SO4•-. Liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS/MS) analysis with 15N labeling revealed the formation of nitro-byproducts (14 kinds), including 1-hydroxy-4-nitro-anthraquinone and its similar derivatives, 4-nitrophenol, and 2,4-dinitrophenol. The nitration pathways of ANT have been proposed and described, mainly including the formation of hydroxyl-anthraquinone-oxygen and phenoxy radicals and the subsequent addition of NO2• and NO•. ANT-based formation of nitro-byproducts during EK, which is usually underestimated, should be further investigated due to their enhanced acute toxicity, mutagenic effects, and potential threat to the ecosystem.

Roles of oxidant, activator, and surfactant on enhanced electrokinetic remediation of PAHs historically contaminated soil.

Electrokinetic (EK) remediation technology can enhance the migration of reagents to soil and is especially suitable for in situ remediation of low permeability contaminated soil. Due to the long aging time and strong hydrophobicity of polycyclic aromatic hydrocarbons (PAHs) from historically polluted soil, some enhanced reagents (oxidant, activator, and surfactant) were used to increase the mobility of PAHs, and remove and degrade PAHs in soil. However, under the electrical field, there are few reports on the roles and combined effect of oxidant, activator, and surfactant for remediation of PAHs historically contaminated soil. In the present study, sodium persulfate (PS, oxidant, 100 g L-1) or/and Tween 80 (TW80, surfactant, 50 g L-1) were added to the anolyte, and citric acid chelated iron(II) (CA-Fe(II), activator, 0.10 mol L-1) was added to catholyte to explore the roles and contribution of enhanced reagents and combined effect on PAHs removal in soil. A constant voltage of 20 V was applied and the total experiment duration was 10 days. The results showed that the removal rate of PAHs in each treatment was PS + CA-Fe(II) (21.3%) > PS + TW80 + CA-Fe(II) (19.9%) > PS (17.4%) > PS + TW80 (11.4%) > TW80 (8.1%) > CK (7.5%). The combination of PS and CA-Fe(II) had the highest removal efficiency of PAHs, and CA-Fe(II) in the catholyte could be transported toward anode via electromigration. The addition of TW80 reduced the electroosmotic flow and inhibited the transport of PS from anolyte to the soil, which decreased the removal of PAHs (from 17.4 to 11.4% with PS, from 21.3 to 19.9% with PS+CA-Fe(II)). The calculation of contribution rates showed that PS was the strongest enhancer (3.3~9.9%), followed by CA-Fe(II) (3.9~8.5%) (with PS), and the contribution of TW80 was small and even negative (-1.4~0.6%). The above results indicated that the combined application of oxidant and activator was conducive to the removal of PAHs, while the addition of surfactant reduced the EOF and the migration of oxidant and further reduced the PAHs removal efficiency. The present study will help to further understand the role of enhanced reagents (especially surfactant) during enhanced EK remediation of PAHs historically contaminated soil.

Reagent-free electrokinetic remediation coupled with anode oxidation for the treatment of phenanthrene polluted soil.

Electrokinetic in-situ chemical oxidation (EK-ISCO) has attracted much attention during remediation of organic contaminated soil. Oxidants in EK-ISCO brings high cost and negative effects on soil physicochemical properties. In this study, a novel approach of combined electrokinetic treatment and anode oxidation was investigated to remediate phenanthrene polluted soils without adding oxidants. The fabricated Ti4O7 acted as anode, and could generate •OH at the rate of 9.31 × 10-7 mol h-1 at current 5.10 mA cm-2 through direct H2O electrolysis. Electro-osmotic flow (EOF) was used to transport phenanthrene to anode for the subsequent degradation. Sandy soil, fluvo-aquic soil and red soil were selected as typical soil samples, because pH and buffer capacity were two important factors affecting the direction of EOF. Strategies were developed to regulate the direction of EOF, including adding CEM membrane, maintaining soil pH at 3.5-4.0 and mixing solution from anode and cathode chambers. After treatment, more than 81.9% of phenanthrene was removed without adding any oxidants, and the remediated soil had low toxicity for Lolium perenne growth based on 3-d cultivation results. The results indicated that EK-AO had the advantage of less energy consumption and superior environmental friendliness than traditional EK-ISCO.

A novel electrokinetic remediation with in-situ generation of H2O2 for soil PAHs removal.

Electrokinetic-Fenton (EK-Fenton) technology requires a high dose of H2O2 to produce •OH radicals, which adds a high cost to the remediation process and raises safety concerns during transportation and storage of H2O2. Moreover, the remediation efficiency of the conventional EK-Fenton process is low due to the meaningless consumption of H2O2 on the electrodes and the alkaline environment near the cathode. In this work, a modified CMK3-gas diffusion electrode (CMK3-GDE) is fabricated. This cathode can continuously generate H2O2, and the cumulative H2O2 concentration can reach 0.23 M during 10 days of the test. The utilization of cation exchange membranes (CEMs) efficiently restricts the decomposition of H2O2 on the electrodes and prevents the alkalization of the soil near the cathode, resulting in a 13.7-43.2% increase of the removal efficiency of polycyclic aromatic hydrocarbons (PAHs). In this new treatment process, PAHs are mainly oxidized into quinones, ketones, alcohols, and small molecule acids, and all these products have lower toxicities than PAHs. The EK-Fenton/CMK3-GDE-CEM system exhibits excellent remediation efficiency for treating PAHs polluted soil, which could be a sustainable, eco-friendly, and low-cost strategy for soil remediation.

Electrokinetic combined peroxymonosulfate (PMS) remediation of PAH contaminated soil under different enhance methods.

Because of the high hydrophobicity, low volatility, and high sorption capacity of PAHs, their remediation in contaminated soil is challenging. Electrokinetic (EK) enhanced chemical remediation is an emerging dual technology employed in this study, using a new oxidant peroxymonosulfate (PMS) to remediate PAHs contaminated soil. Here, PMS migration under electric field and the remediation efficiency for the PAHs polluted soil were assessed. We observed that the PMS removal efficiencies (59.7%-82.8%) were higher than those with persulfate (PS) (53.9%-78.5%), indicating PMS's superior oxidation capacity for PAHs. Although oxidant PMS can decontaminate PAHs in polluted soils, its removal of PAHs was only 11.0% without the enhanced methods. The enhancements increased the removal efficiency for PAHs from 0.33 to 2.10 times. At fixed catholyte pH of 4, the highest removal efficiency (34.1%) was achieved because it enhanced PMS migration from cathode to anode. These findings suggested that PMS was a potential oxidant for EK remediation, and some enhancements must be applied in EK combined PMS remediation PAHs polluted soil.

Electrokinetical enhanced delivery of acidic potassium permanganate and removal of copper-pyrene compound pollution in a red soil.

Soil contaminated by combinations of heavy metals and organic pollutants has become an increasingly prominent environmental issue. Developing efficient technologies to synchronously decontaminate such co-contaminated sites is challenging and imperative. In our previous study for the treatment of Copper (Cu) and pyrene contaminated soil, electrokinetics (EK) coupled acidic permanganate (PM) performed best for degradation of pyrene near the injection spot, but it unfortunately prevented the migration of Cu. In order to further enhance the removal efficiency of these contaminants, in this study, batch experiments were conducted to investigate the feasibility of delivering PM by EK under regular refreshment of acidoxidant along with amplification of voltage gradient. The results showed that PM can be transported from cathode to anode to S2 section (near the anode) with a slow mass transfer rate via electromigration and reversed electroosmotic flow, and further delivery was achieved when Cu and pyrene were coexisted. The reaction of pyrene with PM produced a lower soil pH condition, which was conductive to the transport of Cu, and the existence of Cu promoted the migration of PM. The coexistence of Cu and pyrene favored the removal efficiency of the pollutants, and 92.8% of Cu and 70.7% of pyrene were removed after 15 d EK treatment. Thus, EK + acidic PM with regularly supplement of oxidant is appropriate to achieve complete mass depletion of heavy metals and PAHs, especially in low buffered soils.

Clinical Application of a New Assessment Tool for Myelopathy Hand Using Virtual Reality.

STUDY DESIGN: A cross-sectional study. OBJECTIVE: To assess the effectiveness of a new assessment tool, myelopathy-hand functional evaluation system (MFES), in evaluating the hand dysfunction of patients with cervical myelopathy in the 10-second grip-and-release test (10 second G-R test). SUMMARY OF BACKGROUND DATA: Clumsy fingers movement is a common symptom of myelopathy patients. Evaluating the impaired hand function can provide a strong basis in assessing the severity of myelopathy. Currently, no objective and effective evaluation method is widely accepted in clinical practice. METHODS: MFES mainly consists of a pair of wise-gloves and a computer with software. One hundred and ninety-eight consecutive participants were asked to wear the wise-gloves and then perform 10 seconds G-R test. The movements of each finger were recorded by MFES and converted into waveforms. Relevant waveform parameters were measured and analyzed. The Japanese Orthopedics Association (JOA) scores of each patient were marked and the maximum spinal cord compression (MSCC) was measured on midsagittal T2-weighted magnetic resonance imaging (MRI). RESULTS: Myelopathy patients had a lower number of G-R cycles and a longer time per cycle than healthy subjects. There were significant differences in adduction and abduction time in patients with JOA scores greater than 6, but not in healthy subjects and patients with JOA scores less than 6. The waveforms of ulnar three fingers in myelopathy patients were lower and wider than those in healthy individuals. The average ratio value of wave height to wave width (a/b) could quantitatively reflect such differences of waveforms. According to receiver operating characteristic (ROC) curve analysis, the optimal threshold value of the normal average ratio was more than 1.92. The average a/b value was correlated with the JOA scores of the motor function in the upper extremities (r = 0.842). CONCLUSION: MFES appears to be an objective and quantitative assessment tool for patients with cervical myelopathy. LEVEL OF EVIDENCE: 3.

Influence of electrode configuration on electrokinetic-enhanced persulfate oxidation remediation of PAH-contaminated soil.

Electrokinetic (EK) remediation combined with in situ chemical oxidation (ISCO) can be applied to low permeability organic contaminated soil. However, the effects of electrode configuration on EK-oxidation remediation remain unclear. In this study, EK-ISCO remediation of real polycyclic aromatic hydrocarbon (PAH)-contaminated soil under different electrode configurations was conducted. The results showed that increasing the number of anodes and electrode pairs in one-dimensional (1D) and two-dimensional (2D) electrode configuration was conducive to migration of oxidants into the system. The change in soil pH after remediation in 2D electrode configuration was not obvious, but the increase of soil electrical conductivity (EC) was higher than that of the 1D electrode configuration. The removal rates of PAHs in 2D electrode configurations (35.9-40.9%) were relatively higher than those of the 1D electrode configurations (0.54-31.6%), and the hexagonal electrode configuration yielded the highest pollutant removal efficiency, reaching 40.9%. The energy consumption under 2D electrode configuration was smaller than that under 1D electrode configuration, and the energy consumption of per gram removed PAHs in the hexagon configuration (66.74 kWh (g PAHs)-1) was lowest in all electrode configurations. Overall, the results of this study suggest that 2D electrode configuration is better than 1D and hexagonal electrode configuration is an optimal electrode configuration.

Upregulation of cGMP-dependent Protein Kinase (PRKG1) in the Development of Adolescent Idiopathic Scoliosis.

OBJECTIVE: To explore the molecular regulatory mechanisms underlying fibroblast differentiation and dysfunction in the development of adolescent idiopathic scoliosis (AIS) in an effort to identify candidate therapeutic targets for AIS. METHODS: The GSE110359 dataset, obtained from the bone marrow stromal cells of 12 AIS patients and five healthy controls, was retrieved from the GEO database. The data were preprocessed and differentially expressed genes (DEGs) were identified. KEGG pathway and Gene Ontology (GO)-Biological Process (BP) enrichment analyses were performed to identify the function of the DEGs. A protein-protein interaction (PPI) and a microRNA-transcription factor (TF)-target co-regulatory network were constructed to identify hub genes in the development of AIS. In addition, hub DEGs were evaluated by quantitative PCR (qPCR) and immunohistochemical staining. RESULTS: A total of 188 DEGs including 100 up-regulated and 88 down-regulated genes were obtained. The up-regulated DEGs were related to "p53 signaling pathway", "FoxO signaling pathway", and "cGMP-PKG signaling pathway" terms, while the down-regulated DEGs were significantly enriched in seven terms including "protein processing in endoplasmic reticulum". The key up-regulated genes, PRKG1, CCNG2, and KAT2B, and the key down-regulated genes, MAP2K1 and DUSP6, were identified by the PPI and miRNA-TF-Target regulatory network analyses. mRNA expression patterns for PRKG1, DUSP6, and KAT2B were successfully verified by qPCR. In addition, PRKG1 protein levels were found to be elevated during the immunohistochemical analysis. CONCLUSION: Increased expression of PRKG1 in AIS patients might be an attractive therapeutic target for AIS. However, further gain or loss-of-function studies should be conducted.

Effects of different water management strategies on the stability of cadmium and copper immobilization by biochar in rice-wheat rotation system.

Chemical immobilization of heavy metals is a simple, low-cost, and environment-friendly technology for remediation of heavy metals contaminated soils. However, changes in environmental conditions, such as water management, acid deposition, temperature fluctuation, etc., might result in release of metal ions from the fixation sites, and the long-term stability of immobilization remediation is unclear. This study attempted to investigate the impact of water management strategies (wetting-drying cycle and dry cycle) on the stability of heavy metal immobilization by one-time application of biochar during 3 consecutive years of rice-wheat crop in Cu/Cd-contaminated soil. The transformation and accumulation of Cd and Cu in soil-crop system and the morphololgy and composition of biochar were analyzed. The results revealed that wetting-drying cycle and drying treatments reduced the contents of available Cd and Cu in soil by 15.9%-17.7% and 23.9%-31.5% and by 19.8%-62.7% and 16.1%-65.0%, as well as increased soil pH by 0.11-0.31 and 0.17-0.56, respectively. In the wetting-drying cycle treatment, biochar was more favorable for decrease in Cd and Cu accumulation in crop, when compared with that in dry treatment; however, the differences were insignificant in the subsequent years. Although the different water management strategies had no obvious effect on the soil total C, physicochemical analysis of the biochar collected after pot experiments indicated that the obvious structural decomposition of biochar in the drying treatment may have resulted in the release of heavy metals immobilized in biochar. These findings help in better understanding of the long-term immobilization mechanism of biochar in soil-plant system.

EDTA-enhanced electrokinetic remediation of aged electroplating contaminated soil assisted by combining dual cation-exchange membranes and circulation methods.

This paper introduces a novel method for ethylenediaminetetraacetic acid (EDTA)-enhanced electrokinetic (EK) remediation by combining dual cation-exchange membranes and circulation methods for an aged electroplating soil contaminated by chrome (Cr), copper (Cu), and nickel (Ni). Three laboratory-scale EK experiments were carried out, including T1, the traditional EK process; T2, the traditional EDTA-enhanced EK process; and T3, the assisted EDTA-enhanced EK process. The results obtained show that removal of Cu and Ni in T3 was 3-10 times higher than after T1 and T2. However, the removal of Cr (total) was small in all experiments because of the high content of Cr(III). T3 eliminated the metal accumulation problem that existed for T1 and T2. Simultaneously, the highly acidified area (pH < 4) was reduced from 80% in T1 and T2 to only 20% in T3. The results obtained in T3 indicate that the chelating effect of EDTA has a greater ability to dissolve oxidizable Cu and Ni in the soil than the acidification effect. Toxicity evaluation confirmed that the soil treated by T3 presented a lower effect on a luminescent bacterium (Photobacterium phosphoreum T3) because soil pH tended to be more neutral after this treatment. This research provides a novel method for removing heavy metals from soil in a more environmentally friendly way and clarifies the cause of the existing problems of low removal efficiency and high accumulation in the traditional EK process.

Ion exchange membranes enhance the electrokinetic in situ chemical oxidation of PAH-contaminated soil.

Electrokinetic in situ chemical oxidation (EK-ISCO) could be used to remediate inorganic/organic-contaminated soil. Oxidizing agents were effectively delivered to the contaminated zones through electromigration and the electroosmosis. However, the cathode may react with oxidants, which would reduce the oxidative effect and lead to low contaminant removal rates. In this study, ion-exchange membranes (IEMs) enhanced EK-ISCO was used to remediate polycyclic aromatic hydrocarbons (PAHs) in contaminated soil. IEMs were installed between the electrode compartment and the soil compartment. The results showed that the IEMs could effectively control pH and the oxidation-reduction potential (ORP) changes in the soil column. Placing a cation-exchange membrane (CEM) at the cathode prevented the S2O82- from contacting the cathode and reduced the oxidative loss effect, which meant that PAH removal efficiency significantly improved (from 33.1% to 87.1%). Furthermore, there were minimal changes to the soil properties. Maintaining the soil at a low pH also improved the PAH removal efficiency (93.1%), but the physicochemical properties of the soil significantly changed and a large amount of power was consumed (2015 kWh t-1). This study indicated that placing a CEM at the cathode improved remediation efficiency, and reduced power consumption and the adverse effects on soil properties during EK-ISCO.

Effects of soil properties, nitrogen application, plant phenology, and their interactions on plant uptake of cadmium in wheat.

Appraising cadmium (Cd) phytoavailability and transfer in soil-plant system is imperative and it requires timely and accurate monitoring of Cd to ensure food safety. However, ambiguities regarding the factors regulating Cd mobility and transfer in soil-plant system makes understanding of Cd accumulation mechanism in wheat grain challenging. In present study, we attempted to explore the interrelationship among soil-plant-N management factors governing Cd transfer from soil-to-wheat grain and to provide a novel and alternative approach for grain Cd prediction. For this purpose, we established the allometric relationships of wheat phenology (plant dry matter at different growth stages and grain yield) with grain Cd concentration and soil properties (pH, EC, Eh, and CEC) under varied N rates experiment and investigated the interactions among aforementioned factors. The newly established allometric relationships demonstrated that plant phenology and yield were positively correlated with grain Cd concentration (R2 = 0.86-0.95) and soil properties (R2 = 0.84-0.97). Robust interrelationship among soil-plant-N management factors indicated that Cd transfer from soil-to-wheat grain was potentially co-regulated by their interactive effect. Findings will assist to strategize crop productivity and soil sustainability without compromising food safety. Further studies are imperative to better understand the Cd uptake mechanism in different wheat cultivars and management practices.

Effects of soil environmental factors and UV aging on Cu2+ adsorption on microplastics.

Microplastics (MPs) in natural environments have attracted lots of attention. Although the quantity of MPs present in terrene is much higher than that in aquatic environment, few studies have investigated the chemical behavior of MPs in terrestrial environment. This study investigate the Cu2+ (as a model heavy metal) adsorption capacity of six kinds of MPs (polyamide-6 (PA), polyethylene (PE), polystyrene (PS), polyethylene terephthalate (PET), polyvinyl chloride (PVC), polymethyl methacrylate (PMMA)) in batch adsorption experiments and the effects of different soil environmental factors, including pH and the presence of cations and low-molecular-weight organic acids (LMWOAs), as well as ultraviolet (UV) aging. The Cu2+ adsorption capacities of PA and PMMA were higher than those of other MPs and their maximum equilibrium adsorption capacities (estimated by the Langmuir adsorption equation) were 323.6 µg/g ± 38.2 and 41.03 ± 1.78 µg/g, respectively. The Cu2+ adsorption on MPs was affected by pH, and the greatest amount of Cu2+ adsorbed on PA and PMMA was observed at pH = 6 and pH = 7, respectively. The presence of Ca2+ or Mg2+ inhibited Cu2+ adsorption by MPs, due to competition for the adsorption sites. Moreover, Cu2+ adsorption by MPs was affected by various types of LMWOAs. The Cu2+ adsorption on PA was significantly reduced by citric acid, followed by oxalic acid, and oxalic acid was particularly evident for Cu2+ adsorption on PMMA. UV aging (200 h) had different effect on Cu2+ adsorption on MPs and it depends on the change of carbonyl index. Results demonstrate that soil environmental factors can change the ability of different MPs to adsorb Cu2+ and affect the transport of pollutants as carriers.

Migration and decomplexation of metal-chelate complexes causing metal accumulation phenomenon after chelate-enhanced electrokinetic remediation.

This study investigates the migration and decomplexation effects of metal-ethylenediaminetetraacetic acid (EDTA) complexes during an electrokinetic (EK) remediation process and the resulting metal accumulation phenomena. Six EK tests with control of the electrolyte pH and using ion-exchange membranes were performed to treat Pb-EDTA and Cd-EDTA co-contaminated red soil. The obtained results showed that a portion of free metal cations could be decomplexed from the metal-EDTA complexes due to the low pH and electrochemical degradation at the anode. These cations went back into the soil by electromigration and accumulated in separate locations according to their hydrolysis ability and the distribution of soil pH in different sections. Totals of 61% Cd and 83% Pb were removed from the soil after a 7-day treatment under the condition of controlling the electrolyte pH at 10. The removal efficiencies of metals under the anion-exchange membrane-assisted treatment were higher than those of the cation-exchange membrane-assisted treatment. Based on the mechanisms of metal accumulation phenomena, the migration of decomplexed free metal cations back to the soil is limited by using an anion-exchange membrane or pre-precipitation with alkaline conditions was confirmed to effectively reduce the effect of metal accumulation.

Effects of various warming patterns on Cd transfer in soil-rice systems under Free Air Temperature Increase (FATI) conditions.

Global warming has become an important research topic in different disciplines around the world, especially in the fields of environment quality and food security. As a potential problem in soil environments, cadmium (Cd) contamination of rice under global warming conditions has not been thoroughly investigated. In this study, the fate of Cd in soil-rice systems under various warming patterns was studied via pot experiments under Free Air Temperature Increase (FATI) conditions. The patterns of warming included different temperatures (0.5 °C and 0.8 °C), different day-night durations (nighttime, daytime, and the whole day), and different warming stages (WSx) (including WS1 (seedling to tillering), WS2 (jointing to booting), WS3 (heading), WS4 (grain filling to milk ripening)). At harvest, samples of different rice tissues were collected and the Cd concentrations were measured. The results showed that warming significantly increased Cd concentrations in grain by 1.45 and 2.31 times, which was positively correlated with the two temperature increases (0.5 °C and 0.8 °C), respectively. Both daytime and nighttime warming significantly increased the Cd concentration in grain, and the daytime dominated Cd translocation from roots to shoots. In addition, warming in individual growth stages contributed to increases in Cd accumulation in grain by 31.6% (WS1), 15.0% (WS2), 20.6% (WS3), and 32.8% (WS4), respectively. Specifically, warming during the vegetative phase boosted Cd translocation from roots to shoots, while warming during maturation further increased Cd uptake and remobilization into grain. The projected results could provide a new and in-depth understanding of the fate of Cd in soil-rice systems under global warming conditions in Cd contaminated areas.

Deciphering biodegradable chelant-enhanced phytoremediation through microbes and nitrogen transformation in contaminated soils.

Biodegradable chelant-enhanced phytoremediation offers an alternative treatment technique for metal contaminated soils, but most studies to date have addressed on phytoextraction efficiency rather than comprehensive understanding of the interactions among plant, soil microbes, and biodegradable chelants. In the present study, we investigated the impacts of biodegradable chelants, including nitrilotriacetate, S,S-ethylenediaminedisuccinic acid (EDDS), and citric acid on soil microbes, nitrogen transformation, and metal removal from contaminated soils. The EDDS addition to soil showed the strongest ability to promote the nitrogen cycling in soil, ryegrass tissue, and microbial metabolism in comparison with other chelants. Both bacterial community-level physiological profiles and soil mass specific heat rates demonstrated that soil microbial activity was inhibited after the EDDS application (between day 2 and 10), but this effect completely vanished on day 30, indicating the revitalization of microbial activity and community structure in the soil system. The results of quantitative real-time PCR revealed that the EDDS application stimulated denitrification in soil by increasing nitrite reductase genes, especially nirS. These new findings demonstrated that the nitrogen release capacity of biodegradable chelants plays an important role in accelerating nitrogen transformation, enhancing soil microbial structure and activity, and improving phytoextraction efficiency in contaminated soil.

Effects of root morphology and leaf transpiration on Cd uptake and translocation in rice under different growth temperature.

With growing concerns on cadmium (Cd) contamination of rice grain from the public, the mechanism about the uptake and translocation of Cd in rice plant has been widely studied in recent years. However, the study about the effects of future warming on rice Cd accumulation was almost neglected. In the paper, hydroponic experiments of Cd exposure in growth chambers under different growth temperature (asymmetric and symmetric warming) were conducted to investigate how warming influenced Cd uptake and translocation in rice seedlings (6 liangyou 9368). The results showed that warming significantly increased Cd accumulation in shoot and root by 62.7 to 122 % and 65.5 to 73.9 %, respectively. Moreover, symmetric warming boosted Cd translocation from root to shoot, while antitranspirant treatment inhibited it significantly. The possible mechanisms may be that warming increased the fine root (diameter ≤ 0.5 mm) surface area and enlarged the active sites on root surface by influencing root morphology growth, thus promoted Cd uptake by root. Meanwhile, warming increased leaf transpiration and boosted the xylem stream from nutrient solution to above organs, thus enhanced Cd translocation. This study may provide new understanding and possible explanations about Cd uptake and translocation in rice plant under future warming.