Al Transport Research Articles

Identification of Key Candidate Genes Involved in Aluminum Accumulation in the Sepals of Hydrangea macrophylla

Hydrangea macrophylla (H. macrophylla), a species in the genus Hydrangea in the family Hydrangeaceae, is widely valued for its ornamental qualities in both domestic and international markets. Notably, H. macrophylla is known for its ability to accumulate aluminum (Al). Moreover, aluminum ions (Al3+) participate in sepal bluing. However, the underlying mechanisms of Al accumulation in the sepals remain unclear. In this study, we utilized transcriptome data from two cultivars to identify genes associated with Al accumulation. In total, 154 differentially expressed isoforms between the CK and Tr groups in the sepals of both cultivars were screened. Through gene enrichment analysis and similarity identification in the CDS (coding sequence) region, 43 differentially expressed genes were identified, including 30 upregulated and 13 downregulated genes, in the sepals of the Al treatment group. Further analysis revealed that seven of these upregulated genes are related to Al accumulation in sepals. Among the seven, the gene HmALS3.1 was identified as a potential key player in Al transport within the sepals of H. macrophylla. This study lays the groundwork for further exploration into the mechanisms by which HmALS3.1 regulates Al accumulation in H. macrophylla.

Genome wide analysis of HMA gene family in Hydrangea macrophylla and characterization of HmHMA2 in response to aluminum stress

Aluminum toxicity poses a significant threat to plant growth, especially in acidic soils. Heavy metal ATPases (HMAs) are crucial for transporting heavy metal ions across plant cell membranes, yet their role in Al3+ transport remains unexplored. This study identified eight HmHMA genes in the genome of Hydrangea macrophylla, categorizing them into two major clades based on phylogenetic relationships. These genes were found unevenly distributed across six chromosomes. Detailed analysis of their physicochemical properties, collinearity, and gene structure was conducted. RNA-seq and qRT-PCR analyses revealed that specific HmHMA genes, notably HmHMA2, were predominantly expressed in roots and flowers under Al3+ stress, indicating their potential role in Al3+ tolerance. HmHMA2 showed significant expression in roots, especially under Al3+ stress conditions, and when expressed in yeast cells, it conferred resistance to aluminum and zinc but increased sensitivity to cadmium. Overexpression of HmHMA2 in hydrangea leaf discs significantly improved Al3+ tolerance, reduced oxidative stress markers like hydrogen peroxide and malondialdehyde, and enhanced antioxidant enzyme activity such as SOD, POD and CAT compared to controls. These findings shed lights on the potential role of HmHMAs in Al transport and tolerance in H. macrophylla.

Pt Effect on the Bond-Coating/Superalloy Interdiffusion: Case of a Pt-Modified NiCoCrAlYTa Coating

Heat treatments and oxidation tests were performed on systems composed of a single-crystal AM3 superalloy with a NiCoCrAlYTa+Pt coating to investigate the effect of Pt on Ta and Ti diffusion at high temperature. Experimental results were compared to an AM3 superalloy directly coated with Pt. For all the studied systems, the effect of Pt on elemental activities was evaluated through thermodynamic calculations. Pt diffusion was found to be faster in the NiCoCrAlYTa coating than in AM3. High Ta contents were measured in the Pt-rich γ′ phase below the surface and significant Al and Cr transport toward the surface was observed, in agreement with thermodynamic calculations which predicted an important decrease in their activities in the presence of Pt. An outward diffusion of Ti was also noticed, whereas calculations did not show a decrease in Ti activity due to Pt. Other discrepancies between experiments and thermodynamic calculations were noted and are discussed in this work.

Strigolactones alleviate AlCl3 stress by vacuolar compartmentalization and cell wall blocking in apple.

Poor management and excess fertilization of apple (Malus domestica Borkh.) orchards are causing increasingly serious soil acidification, resulting in Al toxicity and direct poisoning of roots. Strigolactones (SLs) are reported to be involved in plant responses to abiotic stress, but their role and mechanism under AlCl3 stress remain unknown. Here, we found that applying 1 μm GR24 (an SL analoge) significantly alleviated AlCl3 stress of M26 apple rootstock, mainly by blocking the movement of Al through cell wall and by vacuolar compartmentalization of Al. RNA-seq analysis identified the core transcription factor gene MdWRKY53, and overexpressing MdWRKY53 enhanced AlCl3 tolerance in transgenic apple plants through the same mechanism as GR24. Subsequently, we identified MdPMEI45 (encoding pectin methylesterase inhibitor) and MdALS3 (encoding an Al transporter) as downstream target genes of MdWRKY53 using chromatin immunoprecipitation followed by sequencing (ChIP-seq). GR24 enhanced the interaction between MdWRKY53 and the transcription factor MdTCP15, further increasing the binding of MdWRKY53 to the MdPMEI45 promoter and inducing MdPMEI45 expression to prevent Al from crossing cell wall. MdWRKY53 also bound to the promoter of MdALS3 and enhanced its transcription to compartmentalize Al in vacuoles under AlCl3 stress. We therefore identified two modules involved in alleviating AlCl3 stress in woody plant apple: the SL-WRKY+TCP-PMEI module required for excluding external Al by blocking the entry of Al3+ into cells and the SL-WRKY-ALS module allowing internal detoxification of Al through vacuolar compartmentalization. These findings lay a foundation for the practical application of SLs in agriculture.

Silicon attenuates aluminum toxicity in sugarcane plants by modifying growth, roots morphoanatomy, photosynthetic pigments, and gas exchange parameters.

Aluminum (Al) inhibits growth and limits plant productivity in acidic soils. An important strategy to increase Al tolerance is the use of silicon (Si) nutrition. Thus, the aim of this study was to evaluate the interactive role of Si in increasing the growth, physiological and morphoanatomy responses of sugarcane plants under Al toxicity. A 4 × 2 factorial scheme in a completely randomized design was used to study the impact of Si (2mM) on attenuating Al toxicity (0, 10, 15 and 20mgL-1, as Al2(SO4)3·18H2O) in sugarcane seedlings. After 45days, Al toxicity affected sugarcane growth by increasing Al uptake and accumulation, modifying root growth, thickness, and morphoanatomy, and decreasing pigment content, gas exchange parameters, and the number of adaxial and abaxial stomata. However, Si attenuated Al toxicity in the sugarcane seedlings by limiting Al uptake and transport to the shoots, causing positive changes in root morphoanatomy, higher pigment content, improving gas exchange parameters, thereby increased growth. Furthermore, cultivar 'CTC9003' showed beneficial impacts from Si supplementation than 'CTC9002', especially under Al toxicity. The findings of this study suggest that Si plays a notable role in improving anatomical and physiological aspects, particularly the growth of sugarcane seedlings under Al toxicity.

The fate of kyanite in ultrahigh-pressure metasedimentary rocks, southwestern Tianshan, NW China

Kyanite, an aluminous phase common in high- to medium-pressure metapelitic rocks, is critical in revealing complex tectonometamorphic histories of orogenic belts. So far it has not been documented in the well-established low-temperature – ultrahigh-pressure (LT-UHP) metamorphic belt of Chinese southwestern Tianshan. By detailed petrographic investigations, kyanite is recognized as minute inclusions or porphyroblasts in two different types of metasedimentary rocks. In omphacite-garnet phengite schists of the Habutengsu area, kyanite only forms needles associated with acicular phengite and lawsonite (pseudomorphed by paragonite and clinozoisite), and coesite (or its pseudomorph) in the extremely low-Ca core domain of well-zoned garnet. The acicular inclusion assemblage in garnet cores probably witnessed large overstepping of peak-stage reactions in metapelitic rocks in a cold subduction zone. The absence of matrix kyanite in this rock type may be ascribed to elevated Na and Ca activities during the growth of high-Ca garnet rim. This is supported by the common presence of sodic and calcic phases (e.g., paragonite and omphacite) in the matrix or the garnet rim domain, with absence in garnet core. In a suite of calcschists of the Muzhaerte area, kyanite occurs as a matrix and/or inclusion phase. In relatively fresh, less foliated chloritoid-ankerite calcschists, kyanite is a major matrix phase with coesite inclusions and locally surrounded by prophyroblasts or fine-grained aggregates of both paragonite and phengite. In altered chlorite-white mica calcschists, kyanite is rarely embedded in white mica aggregates but commonly enclosed in Fe-rich chloritoid porphyroblasts. The mantling of ankerite by acicular to prismatic Fe-rich chloritoid suggests locally increased Fe2+ activity and Al transport by fluids along grain boundaries. The common white mica corona around kyanite in the calcschists suggests elevated Na and/or K activities postdating kyanite formation. Outcrop-scale variations of kyanite textures and whole-rock alkali element contents support the infiltration of Na- and/or K-bearing fluids, probably a dominant mechanism responsible for the lack of kyanite in the Tianshan UHP metasedimentary rocks. P-T estimates suggest the kyanite corrosion took place at 15–21 kbar and 530–610 °C, corresponding to the early exhumation stage. This study suggests that kyanite may be a major peak phase of the Tianshan UHP metasedimentary rocks, and the complete understanding of its prograde evolution is a prerequisite to unravel the fate of subducted sediments and their chemical geodynamics in cold subduction zones.

Advanced Interventions During Prehospital Transport of Patients with Chest Pain and Suspected Acute Coronary Syndrome

Objective: The aim of this study is to describe the frequency and type of advanced (ALS) interventions performed by emergency medical services (EMS) providers while caring for undifferentiated chest pain patients. Methods: This pilot study is a retrospective review of advanced interventions performed on consecutive adult patients transported by EMS with a provider impression of non-traumatic chest pain and treated under the suspected acute coronary syndrome statewide protocol from July 2013 through January 2022. The EMS system studied is a hospital-based agency which serves a large suburban to rural population in central Pennsylvania. Advanced interventions were defined a priori and included STEMI activation. Results: During the study period, there were 2 456 EMS transports out of 97 877 which met study inclusion criteria. A total of 121 advanced interventions were performed on 101 (4.1%) of these patients, the majority 79 (3.2%) of which were prehospital notification of STEMI activations. Intravenous medications were administered 25 times to 22 (0.9%) patients and advanced procedures were performed 17 times on 7 (0.3%) patients. Several patients received more than one intervention and/or medication. Patients between 60 and 65 years of age accounted for the highest number of activations (283, 11.5%) and received the largest number of interventions (28, 9.9%). Only eight patients were below the age of 45 and all were STEMI activations only. Conclusion: We found that less than 5% of included patients transported by EMS required advanced interventions with the majority of these being STEMI activations not requiring any additional interventions. Further investigation is required to determine if certain characteristics or risk-factors predict the need for out-of-hospital advanced interventions and ALS transport.

High resolution modeling of aluminium transport in a fjord estuary with focus on mean circulation and irregular flow events

Environmental impact assessments of trace metals and radionuclides in estuarine waters will benefit from numerical transport models that can provide detailed and accurate predictions of concentrations of harmful physico-chemical forms of contaminants at adequate spatial and temporal resolution. Aiming to study the potential of aluminium (Al) exposure to biota, a transport model (OpenDrift) including dynamic speciation and transformation processes was improved and applied, using three-dimensional hydrodynamic flow fields from a numerical ocean model (ROMS) at high horizontal resolution (32 m). Al transport and concentration was computed along the Sandnesfjorden Fjord, south-eastern Norway, from river outlet to open coastal waters. Validation of the circulation model with 29 hydrographic profiles from Sandnesfjorden showed substantial improvements compared to previous studies due to optimized model configuration (salinity overestimation decreased from >7 psu to <4 psu). Modeled Al data compared well with observed surface Al concentration from 12 locations and the along-fjord decreasing trend in Al-concentration was well reproduced (error ratios were <2 in Sandnesfjorden). Except in the channel area, both salinity and Al concentration estimates lie well within the expected variability. However, the transport modeling gave a more detailed site-specific picture of the Al concentration, suggesting more scattered and variable fields than indicated by observational data (variations of a factor 3–4 over short spatiotemporal scales). Reversed flow events (surface flow into the fjord) caused considerable mixing and redistribution of water masses, affecting both horizontal mixing of river discharges with coastal water as well as vertically as surface water mixed with deeper water masses. These blocking events strongly changed properties and distribution of the water masses giving rise to local and short-term high Al-exposure episodes (variations of a factor of 10 over a 12 h period) in the fjord that may pose risks to biota and therefore should be taken into account in impact and risk assessments.

Subcellular compartmentalization of aluminum reduced its hazardous impact on rye photosynthesis

Aluminum (Al) toxicity limits crops growth and production in acidic soils. Compared to roots, less is known about the toxic effects of Al in leaves. Al subcellular compartmentalization is also largely unknown. Using rye (Secale cereale L.) Beira (more tolerant) and RioDeva (more sensitive to Al) genotypes, we evaluated the patterns of Al accumulation in leaf cell organelles and the photosynthetic and metabolic changes to cope with Al toxicity. The tolerant genotype accumulated less Al in all organelles, except the vacuoles. This suggests that Al compartmentalization plays a role in Al tolerance of Beira genotype. PSII efficiency, stomatal conductance, pigment biosynthesis, and photosynthesis metabolism were less affected in the tolerant genotype. In the Calvin cycle, carboxylation was compromised by Al exposure in the tolerant genotype. Other Calvin cycle-related enzymes, phoshoglycerate kinase (PGK), glyceraldehyde 3-phosphate dehydrogenase (GAPDH), triose-phosphate isomerase (TPI), and fructose 1,6-bisphosphatase (FBPase) activities decreased in the sensitive line after 48 h of Al exposure. Consequentially, carbohydrate and organic acid metabolism were affected in a genotype-specific manner, where sugar levels increased only in the tolerant genotype. In conclusion, Al transport to the leaf and compartmentalization in the vacuoles tolerant genotype's leaf cells provide complementary mechanisms of Al tolerance, protecting the photosynthetic apparatus and thereby sustaining growth.

The aluminum distribution and translocation in two citrus species differing in aluminum tolerance

BackgroundMany citrus orchards of south China suffer from soil acidification, which induces aluminum (Al) toxicity. The Al-immobilization in vivo is crucial for Al detoxification. However, the distribution and translocation of excess Al in citrus species are not well understood.ResultsThe seedlings of ‘Xuegan’ [Citrus sinensis (L.) Osbeck] and ‘Shatianyou’ [Citrus grandis (L.) Osbeck], that differ in Al tolerance, were hydroponically treated with a nutrient solution (Control) or supplemented by 1.0 mM Al3+ (Al toxicity) for 21 days after three months of pre-culture. The Al distribution at the tissue level of citrus species followed the order: lateral roots > primary roots > leaves > stems. The concentration of Al extracted from the cell wall (CW) of lateral roots was found to be about 8 to 10 times higher than in the lateral roots under Al toxicity, suggesting that the CW was the primary Al-binding site at the subcellular level. Furthermore, the Al distribution in CW components of the lateral roots showed that pectin had the highest affinity for binding Al. The relative expression level of genes directly relevant to Al transport indicated a dominant role of Cs6g03670.1 and Cg1g021320.1 in the Al distribution of two citrus species. Compared to C. grandis, C. sinensis had a significantly higher Al concentration on the CW of lateral roots, whereas remarkably lower Al levels in the leaves and stems. Furthermore, Al translocation revealed by the absorption kinetics of the CW demonstrated that C. sinensis had a higher Al retention and stronger Al affinity on the root CW than C. grandis. According to the FTIR (Fourier transform infrared spectroscopy) analysis, the Al distribution and translocation might be affected by a modification in the structure and components of the citrus lateral root CW.ConclusionsA higher Al-retention, mainly attributable to pectin of the root CW, and a lower Al translocation efficiency from roots to shoots contributed to a higher Al tolerance of C. sinensis than C. grandis. The aluminum distribution and translocation of two citrus species differing in aluminum tolerance were associated with the transcriptional regulation of genes related to Al transport and the structural modification of root CW.

Factors associated with destination of pediatric EMS transports.

Pediatric patients comprise 13% of emergency medical services (EMS) transports, and most are transported to general emergency departments (ED). EMS transport destination policies may guide when to transport patients to a children's hospital, especially for medical complaints. Factors that influence EMS providers 'decisions about where to transport children are unknown. Our objective was to evaluate the factors associated with pediatric EMS transports to children's hospitals for medical complaints. We performed a cross-sectional study of a large, urban EMS system over a 12-month period for all transports of patients 0-17years old. We electronically queried the EMS database for demographic data, medical presentation and management, comorbidities, and documented reasons for choosing destination. Distances to the destination hospital and nearest children's and community hospital (if not the transport destination) were calculated. Univariate and multiple logistic regression analyses were conducted to determine the association between independent variables and the transport destination. We identified 10,065 patients, of which 6982 (69%) were for medical complaints. Of these medical complaints, 3518 (50.4%) were transported to a children's hospital ED. Factors associated with transport to a children's hospital include ALS transport, greater transport distance, protocol determination, developmental delay, or altered consciousness. Factors associated with transport to general EDs were older age, unknown insurance status, lower income, greater distance to children's or community hospital, destination determined by closest facility or diversion, abnormal respiratory rate or blood glucose, psychiatric primary impression, or communication barriers present. We found that younger patient age, EMS protocol requirements, and paramedic scene response may influence pediatric patient transport to both children's and community hospitals. Socioeconomic factors, ED proximity, diversion status, respiratory rate, chief complaints, and communication barriers may also be contributing factors. Further studies are needed to determine the generalizability of these findings to other EMS systems.

Silicon Application Induced Alleviation of Aluminum Toxicity in Xaraés Palisadegrass

Aluminum (Al) toxicity is a major abiotic constraint for agricultural production in acidic soils that needs a sustainable solution to deal with plant tolerance. Silicon (Si) plays important roles in alleviating the harmful effects of Al in plants. The genus Urochloa includes most important grasses and hybrids, and it is currently used as pastures in the tropical regions. Xaraés palisadegrass (Urochloa brizantha cv. Xaraés) is a forage that is relatively tolerant to Al toxicity under field-grown conditions, which might be explained by the great uptake and accumulation of Si. However, studies are needed to access the benefits of Si application to alleviate Al toxicity on Xaraés palisadegrass nutritional status, production, and chemical–bromatological composition. The study was conducted under greenhouse conditions with the effect of five Si concentrations evaluated (0, 0.3, 0.6, 1.2, and 2.4 mM) as well as with nutrient solutions containing 1 mM Al in two sampling dates (two forage cuts). The following evaluations were performed: number of tillers and leaves, shoot biomass, N, P, K, Ca, Mg, S, B, Cu, Fe, Mn, Zn, Al, and Si concentration in leaf tissue, Al and Si concentration in root tissue, neutral detergent fiber (NDF), and acid detergent fiber (ADF) content in Xaraés palisadegrass shoot. Silicon supply affected the relation between Si and Al uptake by increasing root Al concentration in detriment to Al transport to the leaves, thereby alleviating Al toxicity in Xaraés palisadegrass. The concentrations between 1.4 and 1.6 mM Si in solution decreased roots to shoots Al translocation by 259% (from 3.26 to 1.26%), which contributed to a higher number of leaves per plot and led to a greater shoot dry mass without affecting tillering. Xaraés palisadegrass could be considered one of the greatest Si accumulator plants with Si content in leaves above 4.7% of dry mass. In addition, Si supply may benefit nutrient-use efficiency with enhanced plant growth and without compromising the chemical–bromatological content of Xaraés palisadegrass.

Low-Temperature Exothermic Reactions in Al/CuO Nanothermites Producing Copper Nanodots and Accelerating Combustion

Several Al/CuO nanocomposite reactive materials, prepared recently by arrested reactive milling, were found to exhibit a distinct low-temperature exothermic peak around 600 K seen by differential scanning calorimetry. This work is an experimental study aimed to establish whether this low-temperature reaction affects combustion and why it is observed in some but not all materials with identical compositions. The peak is only observed when aluminum is initially separately milled in acetonitrile. Electron microscopy showed resulting composite powders to be porous, unlike fully dense powders obtained without premilling aluminum. The as-prepared and partially reacted powders recovered after heating just past the peak to 650 K were examined using high-angle annular dark-field scanning transmission electron microscopy and electron energy loss spectroscopy. Additionally, X-ray diffraction measurements were performed for all materials. Finally, the reactive powders were ignited using plasma and shock generated by an electrostatic discharge. Results show that the low-temperature exothermic peak is associated with a redox reaction pathway involving release of oxygen by CuO that is not in direct contact with Al and free-molecular transport of that oxygen to the nearby surface of Al. This reaction pathway inhibits the formation of Al/Cu intermetallic phases. Instead, nanometer-scale metallic Cu particles are formed due to CuO reduction. It is also found that this reaction pathway accelerates ignition of reactive powders, which in turn leads to a higher burn rate of aerosolized powder.

Negative charged functional groups play important role in Al transport from environment to plant root outer layer cells

Aluminium in acid soils is highly toxic to plants and expresses negative impact on environment and agricultural production. Understanding its distribution and transport from environment to plant cells especially root cell walls is significant in reducing its phytotoxicity. In the present study, two varieties of wheats (Triticum aestivum L.) ES8 and ET8 with different Al tolerance were examined using fourier transform infrared spectroscopy (FTIR). The spectra results showed that the negative charged functional groups polysaccharide and carboxyl were observed at the wheat roots outer cellular layers. These charged functional groups provided binding sites for free Al3+ ions from the environment. And the supply of negative charges by these groups is probably one of the important reasons of high Al accumulation at plant root cell walls.

Oxalate‐fluoride anion exchange in alpine tundra soil: Impact on aluminium transport

AbstractAnion exchange between ubiquitous low‐molecular‐weight organic acids (LMWOA), such as oxalate, and surface‐retained inorganic anions, such as F−, SO42− and OH−, can play a critical role in Al bioavailability and transport in acidic alpine tundra soil. A series of batch equilibration and composite soil column leaching studies were conducted to examine anion exchange reactions between F−, oxalate and OH−, and the impact of increased soil solution F− concentration on Al transport. The addition of either F− or oxalate to soil suspensions resulted in significantly higher solution pH, suggesting F− and oxalate exchange with surface –OH groups. Distinct stages of OH− release were observed for all soil horizons leached with 1.32 × 10−3 mol l−1 F−, with OH− release decreasing in the order O/A1 ~ A2&gt; &gt; Bw. A similar OH− release pattern was observed in the O/A1 horizon for the 7.81 × 10−4 mol l−1 oxalate treatment, suggesting that both F− and oxalate may be competing for common exchange sites in the O/A1 horizon. Fluoride displacement by oxalate, in batch equilibration experiments, was observed for both the 2.84 × 10−4 mol l−1 and 7.81 × 10−4 mol l−1 oxalate treatment. Individual soil horizons leached with 7.81 × 10−4 mol l−1 oxalate exhibited increased F− leaching in the order O/A1 &gt; A2 ~ Bw, with pulsed F− movement being observed in the O/A1 horizon. Soil columns eluted with 1.32 × 10−3 mol l−1 F− exhibited increased Al solubilization and transport, with Al leaching increasing in the order Bw &gt; A2 &gt; O/A1. Sequential leaching of soil columns in the order D. I. H2O → 1.32 × 10−3 mol l−1 F− → D.I. H2O → 7.81 × 10−4 mol l−1 oxalate indicated that previously adsorbed F− was displaced by oxalate. Displacement of F− by oxalate increased in the order O/A1 &gt; A2 &gt; Bw. Hydroxyl displacement by both F− and oxalate may be an important source of acid neutralization in a soil wetting front, affecting Al speciation and transport.Highlights Oxalate and F− compete for similar OH− exchange sites, increasing soil pH. Adsorbed F− can be displaced by oxalate anions. Al solubilization increases with F− adsorption in alpine tundra soil. Aluminium fluoride speciation changes rapidly within the soil wetting front. Anion exchange reactions should be considered in assessing soil ANC.

Dependence of the impurity transport on the dominant turbulent regime in ELM-y H-mode discharges on the DIII-D tokamak

Laser blow-off injections of aluminum and tungsten have been performed on the DIII-D tokamak to investigate the variation of impurity transport in a set of dedicated ion and electron heating scans with a fixed value of the external torque. The particle transport is quantified via the Bayesian inference method, which, constrained by a combination of a charge exchange recombination spectroscopy, soft x-ray measurements, and vacuum ultraviolet spectroscopy provides a detailed uncertainty quantification of transport coefficients. Contrasting discharge phases with a dominant electron and ion heating reveal a threefold drop in the impurity confinement time and order of magnitude increase in midradius impurity diffusion, when additional electron heating is applied. Furthermore, the calculated stationary aluminum density profiles reverse from peaked in electron heated to hollow in the ion heated case, following a similar trend to electron and carbon density. Comparable values of a core diffusion have been observed for W and Al ions, while differences in the propagation dynamics of these impurities are attributed to pedestal and edge transport. Modeling of the core transport with non-linear gyrokinetics code CGYRO [J. Candy and E. Belly, J. Comput. Phys. 324, 73 (2016)], significantly underpredicts the magnitude of the variation in Al transport. Diffusion increases three-times steeper with additional electron heat flux, and 10-times lower diffusion is observed in ion heated case than predicted by the modeling. The CGYRO model quantitatively matches the increase in the Al diffusion when approaching the linear threshold for the transition from the ion temperature gradient to trapped electron mode.

Boron reduces aluminum deposition in alkali-soluble pectin and cytoplasm to release aluminum toxicity

Boron (B) is indispensable for plant growth and has been reported in the mitigation of aluminum (Al) toxicity in different plants. This study focused on the efficacy of B in reducing Al toxicity to trifoliate orange seedlings in a hydroponic experiment. Boron supply had a positive effect on root length and plant growth-related parameters and attenuated Al-induced inhibition of plasma membrane H+-ATPase activity. X-ray photoelectron spectroscopy (XPS) in conjunction with scanning electron microscope-energy dispersive x-ray spectrometer (SEM-EDS) revealed that B reduced Al accumulation in root cell wall, especially on pectin fractions (alkali-soluble pectin), accompanied by suppressing pectin synthesis, pectin methylesterase (PME) activity and PME expression. Furthermore, B application inhibited NRAT1 expression while increased ALS1 expression, indicating restraining Al transport from external cells to cytoplasm and accelerating accelerating vacuolar sequestration. The results were further demonstrated by transmission electron microscope-energy dispersive x-ray spectrometer (TEM-EDS) analysis. Taken together, our results indicated that B mainly promoted the efflux of H+ by regulating the plasma membrane H+-ATPase activity, and reduced the demethylation of pectin to weaken Al binding to carboxyl. More importantly, B alleviated some of the toxic effects of Al by compartmentalizing Al into vacuoles and decreasing the deposition of Al in cytoplasm.

Ion Exchange Dialysis for Aluminium Transport through a Face-Centred Central Composite Design Approach

An ion exchange dialysis (IED) is used in the recovery of aluminium from residue. In this paper, the face-centred central composite design (FC-CCD) of the response surface methodology (RSM) and desirability approach is used for experimental design, modelling and process optimization of a counter flow IED system. The feed concentration, feed flowrate, sweep flowrate and sweep concentration were selected as the process variables, with the Al transport across a Nafion 117 membrane as the target response. A total of 30 experimental runs were conducted with six centre points. The response obtained was analysed by analysis of variance (ANOVA) and fitted to a second-order polynomial model using multiple regression analysis. The actual R2 and standard deviation of the model are 0.9548 and 0.2932, respectively. Depending on the time zone of reference (24 h or 32 h), the highest enrichment of &gt;1.50 was achieved. The designed variables were numerically optimized by applying the desirability function to achieve the maximum Al transport. The optimised condition values were found to be a feed concentration of 1600 ppm, feed flowrate of 61.76%, sweep flowrate of 37.50% and sweep concentration of 0.75 N for the 80% target response at 32 h. Overall, the model can be used to effectively predict Al recovery using the designed system.

Modeling key processes affecting Al speciation and transport in estuaries

Assessments of the impacts of aluminium (Al) to aquatic organisms in estuarine waters have suffered from the lack of available models that can accurately predict the presence of toxic physico-chemical forms (species) of Al at adequate spatial and temporal resolution. In the present work, transport and distribution of river-discharged Al species through changing environmental conditions in the Sandnesfjorden estuary, South-Eastern Norway, was predicted using a numerical model system at relatively high spatial (32 m × 32 m in horizontal) and temporal (1 h) resolution. New model code was implemented, including dynamic, salinity-dependent speciation and transformation processes, based on in situ measurements from several Norwegian estuaries as well as experimental data. This is the first time such elemental speciation code including LMM, colloidal, particle and sediment species is utilized in an estuary case in combination with high resolution hydrodynamics and compared to an extensive observational dataset. Good agreement was obtained between modeled and observed total and fractionated Al concentration at several stations along the fjord transect. Without including background contribution of Al from the coastal water, the model predicted too low Al concentrations (by up to approximately a factor 4) near the fjord mouth. The surface Al concentrations were also underestimated due to overestimated near-surface vertical mixing in the hydrodynamic model. The observed correlation between salinity and total Al concentration was well reproduced by the model in situations with low upper layer volume flux, typical under low river flow conditions. In contrast, the predicted surface salinity and total Al concentration were less correlated under high-flux conditions. As the general trends of Al concentrations and speciation were well reproduced, this study demonstrated that by including carefully chosen transfer rates, the model can be used to predict spatio-temporal distribution of total contamination as well as concentration levels of the elemental species.

Aluminum mobility in mildly acidic mine drainage: Interactions between hydrobasaluminite, silica and trace metals from the nano to the meso-scale

Aluminum precipitates control the hydrochemistry and mineralogy of a broad variety of environments on Earth (e.g., acid mine drainage, AMD, coastal wetlands, boreal and alpine streams, tropical acid sulfate soils, laterites and bauxites, …). However, the geochemical and mineralogical processes controlling Al (and other associated metals and metalloids) transport and removal in those environments are not fully understood. The geochemical system of Paradise Portal (Colorado, USA) comprises sulfate-rich mildly acidic waters, the hydrochemistry of which is directly controlled by the massive precipitation of hydrobasaluminite Al4(SO4)(OH)10·12-36H2O. Three connected but discernible aluminum precipitation stages were identified and described: 1) nanoparticle formation and size decrease along the creek, 2) hydrobasaluminite neoformation on the riverbed, and 3) precipitate accretion and accumulation on the riverbed leading to Al and Fe banded formations. The co-occurrence of Al and Si in the system was observed, recording significant amounts of Si accompanying the three different components of the system (i.e., nanoparticles and fresh and aged Al-precipitates). Also, abrupt and minor changes in the sedimentary record were described and proposed to be the response of the system to seasonal and interannual changes in AMD chemistry. Concerning the mobility of other metals and metalloids, P, Th, V, W, Ti and B showed a tendency to be preferentially incorporated into hydrobasaluminite, while others like Be, As, Se or Ba tend to remain dissolved in the water.