Increasing Al Concentrations Research Articles

Facile synthesis and characterization of PbS thin films doped with various aluminum concentrations for photovoltaic applications

In this study, aluminum doped lead sulfide (PbS:Al) thin films were deposited on soda lime glass substrates using chemical bath deposition (CBD) technique. The structural, morphological, optical and electrical properties of as-deposited PbS thin films were studied as a function of Al concentration (0, 2, 4, 6, 8 at. %). The deposited films can be analyzed using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), x-ray diffraction (XRD), UV-Vis-NIR spectroscopy and Hall measurement. From SEM, it was evident that the thickness of the films decreased from 750 nm (0 at. %) to 280 nm (8 at. %) with increased Al concentration. XRD analysis revealed that the prepared films exhibited face centered cubic structure without any other binary phases. The average crystallite size of the films decreased from 33.71 to 20.45 nm. The direct optical band gap values were increased from 0.90 to 1.29 eV. The optical parameters such as refractive index (n), extinction coefficient (k), real (ɛ 1) and imaginary (ɛ 2) parts of the dielectric constant were 1.51–2.04, 0.0035–0.0075, 2.50–6.20 and 0.005–0.16 respectively. The absorption coefficient (α) of all the deposited films was in the range of ≈105 cm−1. The electrical resistivity of the deposited films was found in the range of 102–103 Ω·cm. The overall analysis indicate that the deposited PbS:Al thin film shows promise as an absorbing layer for heterojunction solar cell devices.

External aluminium supply regulates photosynthesis and carbon partitioning in the Al-accumulating tropical shrub Melastoma malabathricum.

Aluminium (Al) is toxic to most plants, but recent research has suggested that Al addition may stimulate growth and nutrient uptake in some species capable of accumulating high tissue Al concentrations. The physiological basis of this growth response is unknown, but it may be associated with processes linked to the regulation of carbon assimilation and partitioning by Al supply. To test alternative hypotheses for the physiological mechanism explaining this response, we examined the effects of increasing Al concentrations in the growth medium on tissue nutrient concentrations and carbon assimilation in two populations of the Al-accumulator Melastoma malabathricum. Compared to seedlings grown in a control nutrient solution containing no Al, mean rates of photosynthesis and respiration increased by 46% and 27%, respectively, total non-structural carbohydrate concentrations increased by 45%, and lignin concentration in roots decreased by 26% when seedlings were grown in a nutrient solution containing 2.0 mM Al. The concentrations of P, Ca and Mg in leaves and stems increased by 31%, 22%, and 26%, respectively, in response to an increase in nutrient solution Al concentration from 0 to 2.0 mM. Elemental concentrations in roots increased for P (114%), Mg (61%) and K (5%) in response to this increase in Al concentration in the nutrient solution. Plants derived from an inherently faster-growing population had a greater relative increase in final dry mass, net photosynthetic and respiration rates and total non-structural carbohydrate concentrations in response to higher external Al supply. We conclude that growth stimulation by Al supply is associated with increases in photosynthetic and respiration rates and enhanced production of non-structural carbohydrates that are differentially allocated to roots, as well as stimulation of nutrient uptake. These responses suggest that internal carbon assimilation is up-regulated to provide the necessary resources of non-structural carbohydrates for uptake, transport and storage of Al in Melastoma malabathricum. This physiological mechanism has only been recorded previously in one other plant species, Camellia sinensis, which last shared a common ancestor with M. malabathricum more than 120 million years ago.

New insight into the strengthening mechanism of AlCoCrFeNi2.1 eutectic high-entropy alloy with dual-phase nanolamellar structures achieved via laser powder bed fusion

Recently, the AlCoCrFeNi2.1 eutectic high-entropy alloy (EHEA) prepared by laser powder bed fusion (LPBF) could reach a good balance of strength and ductility. The strengthening effect was only qualitatively clarified, however, quantitative analysis remained unclear. In this study, the quantitative analysis of strengthening mechanisms and the relationship between microstructural characteristics and tensile properties were revealed in depth. The AlCoCrFeNi2.1 EHEA with FCC and BCC dual-phase nanolamellar structures (interlamellar spacings of 200–300 nm) fabricated by LPBF achieved an excellent combination of high yield strength (1116 MPa) and fracture elongation (20.3 %). Compared with as-cast EHEA samples, the FCC/BCC nanolamellar interfaces in the LPBF-printed AlCoCrFeNi2.1 EHEA were still semi-coherent but with a higher degree of coherency, and the Al concentration in the FCC phase increased. Post-deformation analysis showed that there were high-density dislocation pile-up and slip, stacking faults (SFs), and Lomer-Cottrell (L-C) locks in the FCC phase, and there were deformation nano-twins and SFs in the BCC phase. The back stress generated in FCC/BCC phases during tensile deformation could maintain the plastic co-deformation of the two phases. The theoretical calculation revealed that the strengthening mechanisms mainly stemmed from the nanolamellar structures, dislocation strengthening, and the solution strengthening induced by the increased Al concentration in the FCC phase. The calculated result (1096.3 MPa) was consistent with the experimental value, and the nanolamellar structures strengthening (∼720.7 MPa) was the main contributor. This work provides a theoretical quantitative understanding of the strengthening mechanism of the AlCoCrFeNi2.1 EHEA fabricated by LPBF and references for the strengthening mechanism of additively manufactured EHEAs.

Dendrochemical indicators of tree rings reveal historical soil acidification in Swiss forest stands

The deposition of acidifying nitrogen and sulphur compounds from agriculture and fossil fuel combustion has drastically altered the chemical balance of forest soils in many regions of the world, leading to soil acidification with negative impacts on nutrient availability and thus also on tree vitality. The change of nutrient concentrations in the soil solution can be assessed by long-term investigations, however meaningful indicators, reflecting environmental changes, are needed to compare the current nutrient status with past values. We used dendrochemical indicators in stem wood of different tree species to access the impact of acidifying depositions on soil quality and tree nutrition. We selected 328 stem wood samples from 96 trees of Norway spruce (Picea abies), European beech (Fagus sylvatica), Sessile oak (Quercus petrea) and English oak (Quercus robur) from 22 forest sites, which are part of the long-term Intercantonal Forest Observation Program in Switzerland. Four time periods of 20 years were defined according to the emissions of air pollutants between 1910 and 2017. Our results showed a trend of increasing Al concentrations in tree rings of spruce peaking in the most recent time period (2000–2017). Mn and Ca concentrations in spruce and beech wood have decreased significantly throughout the time period 1910–2017. These dendrochemical indicators depended on the soil pH, with higher Al and lower Mn and Ca concentrations for soils with a low pH (pH<4.2). In oak trees the observed dendrochemical changes are confounded with dendrochemical differences between heartwood and sapwood. K and Mg showed inconsistent patterns in all three tree species, which are probably caused by translocation within the stem discs. With the use of piecewise structural equation models (SEM) we highlighted the direct and indirect influences of N deposition on element concentrations in stem wood. The data suggest a relation between increased N deposition and lower base saturation values in the forest soils for all three tree species, which were linked to higher Al concentrations in spruce and lower Mn concentrations in spruce and beech. The relation between Al concentrations in tree rings of Norway spruce and measured base saturation was used to reconstruct past soil base saturation values. It revealed a progressive soil acidification in the long-term forest observation sites. These reconstructed base saturation values were further used to validate modelled values from dynamic biogeochemical models such as SAFE/ForSAFE. This comparison pointed out possible shortcomings such as the lack of organic complexation in those models. Taken together, our analyses showed that element concentrations of Al, Mn, Ca in Norway spruce and European beech stem wood were suitable dendrochemical indicators of environmental change due to soil acidification, as they reflect both direct and indirect effects of air pollutants and chemical soil properties.

Effect of Al concentration on Fe-17Cr alloy during steam oxidation at 400 °C

Accident tolerant cladding materials should have improved properties under the LOCA conditions. FeCrAl alloys are promising materials with high-temperature steam oxidation resistance. Little efforts have been put into understanding the compositional effects on the performance of FeCrAl at operating conditions. This work focuses on understanding the effect of Al concentration in three Fe-17Cr-xAl alloys on oxidation resistance at 400 °C in steam environment. This study shows that increased Al concentration reduces the total oxide thickness, enhances the formation of a uniform Cr-oxide layer. and with sufficient Al concentration allows for the formation of a Cr-oxide, Al-oxide bilayer.

Hatchability and Survival of Lamproglena clariae Fryer, 1956 Exposed to Increasing Concentrations of Aqueous Aluminium

The effect of increased aluminium concentration on the hatchability and survival of Lamproglena clariae is unknown. During October 2019 and October 2020, infected C. gariepinus were collected from the Vaal River and transferred to a controlled aquarium room. Parasite infection was established on acclimated C. gariepinus. Adult female parasites (F2 and F3 generation) on live fish were inspected for egg strings. Viable egg strings were removed, leaving females attached to produce more eggs. Bioassays were performed in varying concentrations of Al (control, 5 µg/L, 30 µg/L, 60 µg/L, and 120 µg/L). Egg development was monitored. In situ physical and chemical water quality parameters were measured, and water samples were collected every 24 h for metal analysis using inductively coupled mass spectrometry. The experiment terminated when all juveniles perished. Five percent of exposed eggs did not hatch in the control solution, compared to 26% in 120 µg/L Al. Hatchability and survival of L. clariae were negatively affected by increased Al concentrations. By removing this ectoparasite from living fish, the need to euthanise the host organism is eliminated, emphasising the usefulness of L. clariae as a bioindicator for metal pollution.

Enhanced alite dissolution by CAH10 addition

The influence of varying Al addition in the form of CAH10 on the hydration of alite was studied to gain further insights into the alite hydration mechanisms in the presence of increased Al concentration in pore solution. Therefore, pure alite and mixtures of alite and CAH10 were investigated by means of isothermal heat flow calorimetry, XRD and pore solution chemistry analysis. The two occurring hydration events can be attributed to the precipitation of two different silicate-bearing hydrate phases, C2ASH8 and C-(A)-S-H. In this case, the consumption and removal of Al in pore solution initiated the change to C-(A)-S-H-forming hydration. Furthermore, the formation of C2ASH8 and the alite reaction rate and reaction were directly influenced by the amount of Al provided by CAH10 addition, leading to an alite reaction turnover of up to 68–86 % within 48 h.

Effect of elevated Al concentration on early-age hydration of Portland cement

To understand the effect of elevated Al concentration on early hydration in Portland cement, hydration heat, the evolution of solid and aqueous composition in paste blended with reactive alumina were investigated in this study. The increase of Al concentration depletes gypsum rapidly with massive precipitation of ettringite during the pre-induction period, resulting in decreased Ca and S concentration in pore solution. The elevated Al concentration passivated the active sites on C3S surface, and the decreased Ca concentration inhibited the nucleation of C–S–H and precipitation of portlandite, hence prolonging the induction period. Meanwhile, the reaction of C3A has not been accelerated even after the complete depletion of gypsum, which is associated with the lowered undersaturation degree caused by the increased Al concentration. Additionally, the precipitation of large amounts of ettringite and foil-shaped C–S–H reduced available nucleation sites, thus hindering the reaction of both C3S and C3A during the acceleration period.

Bromelain Modulates Liver Injury, Hematological, Molecular, and Biochemical Perturbations Induced by Aluminum via Oxidative Stress Inhibition.

Aluminum (Al) is an important factor in the environment as it is used in agriculture and several industries leading to hazardous effects via oxidative stress. Bromelain is a cheap extract from the byproduct waste of Ananas comosus stem. It has been used in several biological and therapeutic applications. So, this study was undertaken to assess the hepatoprotective potential of bromelain versus oxidative stress induced by aluminum chloride in rats. Results revealed that administration of AlCl3 reduced the body and liver weights and increased Al concentration in the blood and liver tissue. Also, AlCl3 caused valuable changes in hematological parameters and increased TBARS and H2O2 concentrations in rat liver. Enzymatic (SOD, CAT, GPx, GR, and GST) and nonenzymatic (GSH) antioxidants and protein content were significantly decreased. Furthermore, alterations in liver biomarkers such as bilirubin level and enzyme activities in both serum and liver homogenate (LDH, ALP, AST, and ALT) were detected. AlCl3 also caused inflammation as indicated by upregulation of the inflammation-related genes [interleukin 1 beta (IL-1β)], tumor necrosis factor-alpha (TNF-α), as well as matrix metalloproteinase (MMP9), and downregulation of nuclear factor erythroid 2 (Nrf2) expression. In addition, histopathological examination showed significant variations in the liver that confirms the biochemical results. Otherwise, bromelain intake alone slumped lipid peroxidation and gotten better antioxidant status significantly. Moreover, supplementation with bromelain before AlCl3 intoxication restores enzymatic and nonenzymatic antioxidants as well as biochemical indices and tissue architecture with respect to the AlCl3 group. In conclusion, bromelain proved its remarkable protective power to abolish AlCl3 toxicity. So, it might represent a new strategy in the therapy of metal toxicity by its antioxidant capacity.

Determination of optical properties of quantum wells with a structure of AlGaN/GaN resonant tunneling diodes (RTDs)

Two-dimensional multiple quantum well (MQW) and modified symmetric quantum well (MSQW) carrier confinement play an important role in AlGaN/GaN resonant tunneling diodes (RTDs) efficiency improvement. Therefore, AlGaN-based materials are suitable for development of ultraviolet-light sources. Hence, an attempt is made to investigate the optical properties of AlGaN/GaN. Asymmetric quantum well structure consisting of N-doped AlGaN wells, GaN steps, and undoped AlGaAs barriers is developed. The significant absorption is observed due to the strong coupling effect of the electronic state wave functions. Asymmetric potential well proposed for AlGaN/GaN/AlGaN RTDs. The barriers and the thin layer in the quantum well are theoretically determined. For GaN/AlGaN QW of width L, the frequencies of the symmetric interface modes satisfy the condition. The increase in well width increases the full-width at half maxima (FWHM) from 0 to 100 nm, while increased Al concentration decreases FWHM from 6 to 1 nm.

Impact of polyaluminum chloride on the bioaccumulation of selected elements in the tissues of invasive spiny-cheek crayfish (Faxonius limosus) – Potential risks to consumers

The effect of coagulants used in lake reclamation on crayfish is poorly understood. Therefore, the aim of this study was to evaluate changes in the bioaccumulation of Al, Ca, Cu, Fe, K, Mg, Na and Zn in the gills, exoskeleton, muscle and hepatopancreas of spiny-cheek crayfish (Faxonius limosus) as a result of exposure to PAX®18 coagulant, containing polyaluminum chloride. The study also evaluated the risk to human health from the consumption of crayfish muscle. Metal levels, determined using atomic absorption spectrometry, differed between metals (the highest concentrations for Ca, K, Na, Mg) and the body part. Calcium was most abundant in the exoskeleton, K in the muscles, while Cu and Al in the hepatopancreas. The bioaccumulation of metals was affected by exposure to the coagulant, with a statistically significant (p < 0.05) increase in muscle concentration of Al and Na and a decrease in Ca and Fe. The concentrations of elements (in μg g−1) in the muscle of the control group crayfish and those in contact with the coagulant were, respectively: K (2150; 2090), Na (1540; 2020), Ca (749; 602), Mg (207; 174), Al (103; 164), Zn (21.1; 19.1), Fe (7.6; 3.8) and Cu (8.4; 7.6). Most elements were below 12% of the Dietary Reference Values (DRV). The Al concentration in the muscle exceeded the tolerable weekly intake (TWI) (maximum 164% TWI for muscle of crayfish exposed to polyaluminum chloride). In conclusion, the studied F. limosus had typical elemental bioaccumulation for a crayfish, but the contact with the coagulant increased Al concentration and decreased Fe, Ca, Mg, Zn and Cu concentrations. The muscle of crayfish can be used as a supplementary source of essential elements in the human diet, but it seems necessary to introduce obligatory control of Al levels due to the use of polyaluminum chloride in lake restoration.

Formulating Portland cement–reactive alumina blend through thermodynamic modeling to prevent the alkali–silica reaction

AbstractThis study aims to formulate solid and aqueous compositions of hydrated Portland cement incorporated with reactive alumina (RA) via thermodynamic modeling, with the goal to prevent alkali–silica reaction (ASR). Based on SEM/EDS point analysis, the uptake of Al into C–S–H was corrected in the thermodynamic modeling to improve the accuracy. The predicted solid and aqueous compositions were validated by means of XRD, TGA, and ICP. An accelerated mortar bar test was also carried out to confirm the ASR mitigating efficiency, and a preliminary relationship among the ASR expansion, solid assemblage, and aqueous species was established. The critical content for RA is around 5.75% in the studied systems, above which katoite precipitates, resulting in increased Al concentration in the pore solution (∼0.8 mmol/L); hence, ASR can be effectively inhibited.

Biochemical, histological, and neuro-physiological effects of long-term aluminum chloride exposure in rats.

This study aimed to evaluate the effect of daily sublethal doses of aluminum (Al) on hematological, physiological, biochemical, and behavioral changes in male albino Wistar rats. In addition, Al tissue accumulation and histopathological changes in the cerebral cortex, liver, and kidney were examined. The rats were randomly separated into three groups. Group 1 included rats who received the median deadly dose (LD50) of aluminum chloride (AlCl3), group 2 served as the control, and group 3 was treated with a non-lethal dose of AlCl3 (1.5mg/kg) intraperitoneally for 45days. At defined time intervals, hepatic and renal specific enzymes and biochemical activity were measured. In addition, we examined Al accumulation, the condition of the liver via histological methods, and the impact on the cerebral cortex. In comparison to the controls, rats treated with AlCl3 exhibited a rise in AST, ALT, and ALP enzyme activity. We also saw a significant decrease in body weight and a decrease in total protein, lipids, cholesterol, acetylcholinesterase (AChE), RBCs, and Hb levels compared to the control group. Histopathological examination suggested severe changes in the liver, kidney, and cerebral cortex of the rats. The current study indicates that sublethal daily exposure to AlCl3 causes hazardous effects, as increased Al concentration in the body is shown to induce detrimental biochemical and histological changes as well as decreased body weight. Therefore, careful attention should be given to treatments requiring long exposure in patients and the potential for accumulation via food and drinking.

Genotypic variation among chickpea and wild Cicer spp. in nutrient uptake with increasing concentration of solution Al at low pH

In many acidic soils, high concentrations of toxic Al3+ hamper plant growth by restricting root growth which in turn restricts water and nutrient absorption. Previous research showed variation among chickpea (Cicer arietinum L.) and wild Cicer species in root elongation at 15 μM Al or more, but effects on nutrient absorption have not been examined. The variation in nutrient uptake of two chickpea varieties (PBA HatTrick and PBA Striker) and two wild Cicer species (C. echinospermum (C. echi) and C. reticulatum (C. reti)) was determined in low pH (4.2) nutrient solution with increasing Al concentrations (0, 7.5, 15, 30 μM Al). While C. echi, PBA HatTrick and PBA Striker had thicker roots and more lateral roots compared to C. reti, C. reti had greater aluminium tolerance index (AlTI) at 15 and 30 μM Al. The C. echi had higher uptake of root and shoot Al (7.5, 15 and 30 μM Al), P and S (15 and 30 μM Al) while its uptake was marginally lower for Mg, Ca (all Al treatments) and K (15 and 30 μM Al). By contrast, C. reti contained higher shoot Ca concentration at 15 and 30 μM Al and it had lower root Al uptake. Manganese uptake by C. reti roots and shoots were high enough to induce moderate Mn toxicity at 0 and 7.5 μM Al. Therefore, in response to Al toxicity, C. reti maintained greater AlTI and restricted Al uptake while increasing Ca uptake.

Effects of the aluminum concentration on twin boundary motion in pre-strained magnesium alloys

We investigated the effects of Al concentration on the reciprocated motion of twin boundaries in pre-strained Mg-Al-Zn alloys through a combination of applied compression and tension, in-situ electron-backscattering diffraction observations, and high-angle annular dark-field scanning transmission electron microscopy observations. The twin growth was restricted by increased Al concentration, which resulted in the occurrence of smaller-sized twins. The reverse motion of twin boundaries was also restricted, resulting in the formation of higher fractions of secondary twins and 2–5° boundaries during reverse tension. The secondary twins and 2–5° boundaries mainly contributed to the increased ultimate tensile strength of the pre-strained Mg alloys. This effect is more significant in Mg alloys with larger pre-compression. Moreover, the increased amount of the Al solute atoms, rather than the precipitates, mainly contributed to the increased strengthening effect on the twin boundary motion. Our research contributes to development of high-strength Mg alloys by stabilizing twin boundaries.

Impacts of the Samarco Tailing Dam Collapse on Metals and Arsenic Concentration in Freshwater Fish Muscle from Doce River, Southeastern Brazil.

On November 2015, Samarco tailings dam in Mariana, Minas Gerais, Brazil, collapsed, releasing 62 million tons of tailings that advanced through 668 km of the Doce River and adjacent floodplain. Although the collapse was the worst environmental disaster in Brazil, little is known about its consequences to aquatic biota. Here we evaluate the effects of the tailings mudflow on metal and As concentration in fish and how concentration correlates with water and fish characteristics. We quantified semitotal amounts of Ag, Al, As, Cd, Cr, Cu, Fe, Hg, Mn, Ni, Pb, and Zn in fish muscle tissue using inductively coupled plasma mass spectrometry (ICP-MS) in 255 individuals (34 species) sampled in unaffected and affected areas along the Doce River basin. Arsenic and Hg were higher in fish from affected sites, likely due to turbulent mixing of previously sedimented material by the giant tailings wave. Silver and Zn concentrations were higher in unaffected sites. Arsenic concentration in Geophagus brasiliensis decreased with increasing fish weight. Copper and Zn decreased with increasing fish weight considering the whole assembly of fish. The tailings mudflow increased water conductivity, and conductivity increased Al concentration in fish, so we expected a larger Al concentration in fishes from affected sites. However, the observed Al concentration in fishes from affected sites was lower than expected by water conductivity. Thus, the tailings mudflow reduced Al uptake or accumulation in fishes. Mercury decreased with increasing water conductivity in both unaffected and affected sites considering all species and in G. brasiliensis alone. Despite the relatively low concentration range of metals and As found in fish, fishes from sites affected by the Fe ore tailings mudflow showed higher As and Hg concentration, compared to fishes from unaffected sites. The higher As and Hg in affected sites require further detailed monitoring to ensure safeguards of human health by fishing activity along the Doce River. Integr Environ Assess Manag 2020;16:622-630. © 2020 SETAC.

Occurrence of endogenous hormones in the roots of Masson pine (Pinus massoniana Lamb.) seedlings subjected to aluminum stress under the influence of acid deposition

Aluminum (Al) toxicity is perceived as a potential threat to the integrity of forest ecosystems. The detrimental effects of acidic deposition on trees are caused by mobilization of Al in soils. To better understand how roots adapt to acidic deposition releasing toxic Al including the endogenous hormones {{abscisic acid (ABA), gibberellic acid (GA3), indole-3-acetic acid (IAA) and zeatin riboside (ZR)}}, chemistry {{Ca/Al ratio, and base saturation (BS)}}, and growth rate, with the 100-day-old Masson pine (Pinus massoniana Lamb.) seedlings as research target, we studied the responses of the hormones to rhizospheric Al concentrations and their relationships between pine growth rates and Ca/Al ratios in the simulated soil solutions and forested soils differing in BS. In a hydroponic culture, after the seedlings were exposed to the simulated soil solutions containing 0 (control), 50, 100, 150, 200 µM Al at pH 4.0, ABA formed in the roots increased significantly with the time and intensity of Al exposure. ABA concentrations were positively correlated with rhizospheric Al concentrations (r = 0.92), whereas the opposite trend was seen for GA3 (r = −0.77). Simultaneously, IAA and ZR did not change with the increasing Al concentrations. Increasing of either Al concentration or exposure time caused an inhibition of root elongation and seedling growth. Moreover, in a field soil culture, the seedlings were grown for 60 days (d) in either A horizon soils with a BS above 17% or B horizon soils with a BS below 7%. Evident regional variation of ABA concentrations was observed in the pine roots, which declined in the order: Jin Yun Shan > Nan Shan > Tie Shan Ping, as well as B horizon soil > A horizon soil. Also, ABA concentrations were negatively correlated with soil Ca/Al ratios (r = −0.67). The opposite trends were simultaneously observed for GA3, IAA and ZR (r = 0.45, 0.25 and 0.18, respectively). Based on the laboratory and field results, under the influence of acid deposition, ABA, and GA3 may play an important synergic role in regulating Al resistance of Masson pine as an Al-stress signal.

Effects of aluminium on Clarias gariepinus physiology, gills histology and cholinesterase in vivo and in vitro

The gill is the site of acid-base balance, ionic regulation, gas exchange, and nitrogenous waste excretion by fish. The physiological, histopathological and enzymatic alterations from Clarias gariepinus gills were examined to assess the effects induced in gill tissues within 96 h exposure to waterborne Al 2 (SO 4 ) 3 with different concentrations (25 to 300 mg/L). The exposure of C. gariepinus to aluminium showed deleterious effects to normal fish behaviours and varying degrees of gill damage when visualised under inverted light microscopy (stained with haematoxylin-eosin), scanning electron microscopy and transmission electron microscopy. The mortality rate was observed increasing with increased Al concentration showing noticeably disrupted lamellae, irregular nucleus shape and increasing area of vacuolation in treated fish gills associated with Al 2 (SO 4 ) 3 exposure concentration. Furthermore, electron microscopic X-ray microanalysis of fish gills exposed to sublethal Al revealed Al accumulated on the surface of the gill lamella. Al toxicity also gave inhibitory effects on cholinesterase (ChE) extracted from the fish gills with 90.0% inhibition at 300 mg/L Al highest concentration exposure (in vivo), whereas the Al metal ion inhibited 50% of ChE activity at 4.12 mg/L (IC 50 ).

Depicting the physiological and ultrastructural responses of soybean plants to Al stress conditions

Aluminium (Al) is a toxic element for plants living in soils with acidic pH values, and it causes reductions in the roots and shoots development. High Al concentrations can cause physiological and structural changes, leading to symptoms of toxicity in plant tissue. The aim of this study was to describe the Al toxicity in soybean plants through physiological, nutritional, and ultrastructure analyses. Plants were grown in nutrient solution containing increasing Al concentrations (0; 0.05; 0.1; 1.0, 2.0 and 4.0 mmol L−1). The Al toxicity in the soybean plants was characterized by nutritional, anatomical, physiological, and biochemical analyses. The carbon dioxide assimilation rates and stomatal conductance were not affected by the Al. However, the capacity for internal carbon use decreased, and the transpiration rate increased, resulting in increased root biomass at the lowest Al concentration in the nutrient solution. The soybean plants exposed to the highest Al concentration exhibited lower root and shoot biomass. The nitrate reductase and urease activities decreased with the increasing Al concentration, indicating that nitrogen metabolism was halted. The superoxide dismutase and peroxidase activities increased with the increasing Al availability in the nutrient solution, and they were higher in the roots, showing their role in Al detoxification. Despite presenting external lesions characterized by a damaged root cap, the root xylem and phloem diameters were not affected by the Al. However, the leaf xylem diameter showed ultrastructural alterations under higher Al concentrations in nutrient solution. These results have contributed to our understanding of several physiological, biochemical and histological mechanisms of Al toxicity in soybean plants.

Aluminum-induced stress differently modifies Urochloa genotypes responses on growth and regrowth: root-to-shoot Al-translocation and oxidative stress

Forage grasses belonging to the Urochloa (Brachiaria) genus present tolerance to Al toxicity, however there are intra- and interspecific differences among the species, which in turn should be better depicted. Here we evaluate genotypic differences in Al tolerance in four Urochloa (U. decumbens cultivar Basilisk; U. brizantha cultivar Marandu; U. brizantha cultivar Piata and U. brizantha cultivar Xaraes) cultivated in nutrient solution, during growth and regrowth. We analyzed the effect of Al uptake on epidermal and cell membrane damage, and lipid peroxidation in shoots and roots. Exposure of genotypes to Al concentration up to 1.33 mmol L−1 led to different degrees of shoot yield, mainly during the growth period. Increased Al concentration decreased dry matter production in shoots and roots, reduced leaf area (LA), relative root growth, increased Al accumulation in the roots and root-to-shoot Al translocation, notably during the first growth period. However, Al translocation from roots to shoots augmented massively in all genotypes, during the regrowth. Plant roots exposed to Al were damaged, exhibiting ruptures in the epidermis and reduced number of root hairs. Lipid peroxidation in shoots ranged in all genotypes exposed to Al, however, the oxidative stress was 2–5 times higher in shoots than in roots, notably in Marandu that accumulated 95% more Al than U. decumbens. This suggests that in the genotypes that are more tolerant to Al there is maintenance of metabolic activities, including upregulated and efficient antioxidant activity, root growth, LA growth and biomass yield.