High Al Levels Research Articles

Hot ductility of TWIP steels

The hot ductility of twin induced plasticity (TWIP), 0·6 wt-%C steels containing 18–22 wt-%Mn with N levels in the range 0·005–0·023 wt-% and the Al additions either low (<0·05 wt-%) or high (1·5 wt-%) has been examined. Little change in ductility occurred in the temperature range 1100–650°C as the structure was always fully austenitic. Ductility was generally poor (<40%), reduction of area values, the best ductility at the higher Al level being given by the steel with the lowest N and S levels. Because the steel is fully austenitic, the ductility is solely dependent on that for unrecrystallised austenite. Therefore, to avoid transverse cracking the volume of second phase particles should be kept to a minimum, i.e. the N should be low to reduce the amount of AlN that can be precipitated out and the S level should be as low as possible to limit the amount of MnS inclusions. Metallographic and TEM studies were carried out and the poor ductility was found to be due to extensive precipitation of AlN at the austenite grain boundaries. Increasing the cooling rate from the melting point to the test temperature from 60 to 180°C min−1 or introducing an undercooling step both led to even worse ductility.

An Experimental Study of the Liquid Domain of the Zn-Fe-Al-Mn Quaternary System at 460 °C

The liquid domain of the Zn-Fe-Al-Mn quaternary system at 460 °C was experimentally investigated. The nature of relevant intermetallic compounds was studied using scanning electron microscopy-energy dispersive x-ray spectroscopy (SEM-EDS). A total of 12 Fe-oversaturated baths with various Mn additions was prepared for the study. When the Al addition was fixed at 0.14 wt.%, δ-FeZn10 and δ-MnZn9 were found to co-exist with the liquid phase at low Mn additions. Increasing Mn additions above 1.3 wt.% greatly stabilized δ-MnZn9 so that it became the sole compound existing in the liquid phase. When the Al addition was fixed at either 0.16 or 0.27 wt.%, η-Fe2Al5 was found at low Mn additions but ceased to exist as Mn additions increased above 0.8 wt.%. The current study indicates that the addition of Mn to the bath promotes the formation of δ phases, thus shifting the invariant point of δ/η in the Zn-Fe-Al ternary system to a higher Al level. Based on experimental results, the liquidus surfaces in the Zn-rich corner of the quaternary system at 460 °C were schematically constructed, and implications for practical galvanizing operations were suggested.

Hot ductility of steels and its relationship to the problem of transverse cracking in continuous casting

<title/>The influence of composition and cooling rate on the hot ductility of steels has been reviewed. Models to predict hot ductility behaviour have been discussed and the parts of the trough which can be used to predict the likelihood of cracking occurring are highlighted. On tensile testing both deformation induced ferrite in sufficient quantity to improve ductility and dynamic recrystallisation occur but not when straightening during continuous casting; the strain being too low. This limits the use of the hot ductility curve in predicting cracking behaviour. The temperature range in which straightening of the continuously cast strand should be carried out is either 30°C below the Ar3 when there is a large amount of ferrite (∼40%) present before deformation or above the Td, the temperature at which dynamic recrystallisation starts to take place in a tensile test; this being when the ferrite film no longer forms and precipitates are sufficiently coarse and few in number to influence the ductility. The influence of C,Mn,N, Nb,V,B,Ti,Al and the residuals Cu and Sn on hot ductility are examined and recommendations made with regard to the amounts and cooling conditions required to give freedom from transverse and edge cracks. The hot ductility of the new transformation induced plasticity (TRIP) and twin induced plasticity (TWIP) steels has also been reviewed. P has been shown to have little influence on the hot ductility, but for Al based TRIP and TWIP steels, Al levels need to be closely controlled and high Al levels, (1·5 to 2%Al) are favoured.

Evaluation of the protective role of melatonin on the behavioral effects of aluminum in a mouse model of Alzheimer's disease

In this study, five months old female transgenic (Tg2576) and wild-type mice were exposed for 6 months to aluminum (1 mg Al/g diet), melatonin (10 mg/kg/day), Al plus melatonin, or vehicle only (control group). General motor activity was evaluated using an open-field, whereas spatial learning and memory were assessed in a water maze. Aluminum levels in hippocampus, cortex and cerebellum were determined. Aluminum-treated Tg2576 mice showed higher Al levels in hippocampus than non-Al treated animals. No Al effects on general motor activity were found, while the open-field test showed an increased number of rearings in Tg2576 mice. A lower habituation pattern was observed in melatonin-treated animals. Differences in learning were noted in the water maze acquisition test, in which Al-treated Tg2576 mice showed more difficulties in learning the task than Al-exposed wild mice. No significant effects of melatonin in the acquisition task were observed. The present results indicate that Tg2576 mice are sensitive to high dietary Al levels. A significant protector role of melatonin on Al-induced behavioral effects was not observed.

SCREENING OF SESBANIA FOR TOLERANCE TO ALUMINUM TOXICITY AND SYMBIOTIC EFFECTIVENESS WITH ACID TOLERANT RHIZOBIA STRAINS IN ACID SOIL IN WESTERN KENYA

SUMMARYNitrogen fixation by leguminous trees such as sesbania (Sesbania sesban) in acid soils is limited by aluminium (Al) toxicity and phosphorus (P) deficiency. We screened 214 East African sesbania accessions for Al toxicity tolerance, P use efficiency and sesbania–rhizobia symbiosis. Aluminium toxicity tolerance or sensitivity was measured by the relative root elongation index. Highly Al tolerant and sensitive accessions were screened for P use efficiency. Highly P use efficient and Al sensitive accessions were assessed for symbiotic effectiveness with acid tolerant rhizobia. Eighty-eight per cent of the accessions were Al toxicity tolerant. High Al levels reduced shoot P content by 88% and total dry matter (TDM) by 83%. P addition increased shoot P content and TDM. Rhizobia inoculation increased nodulation by 28–82%, shoot N content by 28–45% and TDM by 15–34% in the low rhizobia density acid soil of Bumala, Kenya. P use efficient accessions had higher nodulation, shoot N content and TDM in the ranges 32–70, 20–52 and 22–36%, respectively, compared to sensitive genotypes. The combination of sesbania accession (SSUG10) and rhizobia strain ASs48 was superior in shoot N accumulation. Inoculation of P use efficient germplasm with acid tolerant rhizobia can improve N-rich biomass accumulation suitable for N replenishment in acid soils.

Genetic adaptation to soil acidification: experimental evidence from four grass species

Anthropogenic acidification has reduced soil pH and released potentially toxic aluminium (Al) ions in many regions. This investigation examines whether increased acidity has caused genetic adaptation to acidic conditions within the grass species Elymus caninus, Poa nemoralis, Deschampsia cespitosa and D. flexuosa. We sampled tussocks (genets) of each species in two regions of southern Sweden, differing in their exposure to acidifying deposition. The tolerance of the genets was tested in a solution experiment with different pH and Al concentrations. Our data suggest that species found at lower pH field locations have a greater tolerance to low pH and high Al levels than species found on less acidic soils. Analysis of variance showed a significant average effect of population and (or) genet in most species; however, we found little evidence of genetic adaptation to acidic conditions at the regional, population and micro-site level. In fact, there was no consistent change in the ranking of populations or genets with varying pH or Al concentration. Based on these results, we hypothesize that phenotypic plasticity rather than genetic adaptation has been favoured as the predominant mechanism to cope with soil acidity in the four grass species.

Stream sediment geochemistry of the Upper Mahaweli River Basin of Sri Lanka—Geological and environmental significance

Stream sediment geochemical maps serve as a tool for mineral exploration, identifying pollutant sources and providing information on weathering and transport processes. This paper presents geochemical maps of the upper catchment of the Mahaweli River of Sri Lanka, with interpretations based on geochemistry, geology and environmental conditions. For the construction of these maps, stream sediment geochemical data of 1585 samples, collected from 05 main tributaries of the Mahaweli River, was used. Elemental concentrations of 19 major and trace elements were determined by X-ray fluorescence spectrometry. Geochemical maps were prepared and existing geological maps, discriminant analysis, factor analysis, and correlation coefficients were used to recognize the relationship between spatial distribution patterns and the geological and environmental factors. These maps and statistical analysis clearly show the identical geochemical behavior of K, Rb, Ba and Sr. Even Mg and Ca show a similar distribution in different basins, the lack of correlation with metacarbonates probably being due to dissolution of Ca–Mg bearing minerals. The anomalous concentrations of these elements observed in the Anda Oya of Belihul Oya basin may indicate the existence of a Fe–Cu ore body and a Ni–Cr deposit in the upstream tributary of Badulu Oya. This however needs further detailed geological investigations. High Al levels in some streams seem to be controlled by high silt and clay contents released due to agricultural soil erosion in the upstream areas. Similarly, Pb enrichment in the vicinity of some cities may also be anthropogenic. Na, Mn, Ti, Nb, Y, Zn, Zr distribution in the stream sediment shows a relationship with the underlying lithologies of the area.

Major and trace elements in plants and soils in Horton Plains National Park, Sri Lanka: an approach to explain forest die back

Forest die back has been observed from 1980s in the montane moist forest of Horton Plains in the Central Sri Lanka for which the aetiology appears to be uncertain. The concentration levels of Na, K, Ca, Mg, Fe, Mn, Cu, Ni, Zn and Pb in canopy leaves, bark and roots, which were collected from dying and healthy plants of three different endemic species, Calophyllum walkeri, Syzygium rotundifolium and Cinnamomum ovalifolium, from three different die back sites were studied. Soils underlying the plants were also analyzed for their extractable trace metals and total contents of major oxides. Analysis of dead and healthy plants does not show any remarkable differences in the concentrations of studied trace elements. The results show that there is a low status of pollution based on the concentrations of chemical elements of environmental concern. Extractable and total trace element analysis indicates a low content of Ca in soils due to high soil acidity that probably leads to Mg and Al toxicity to certain plants. Relatively high Al levels in the soil would affect the root system and hamper the uptake and transport of essential cations to the plant. It therefore seems that the forest declining appears to be a natural phenomenon, which occurs due to the imbalance of macro and micronutrients in the natural forest due to excessive weathering and the continuous leaching of essential elements.

Influence of Al and P additions on hot ductility of steels

The hot ductility curves of a series of P containing, TRIP type steels (0·08–0·1%P) with Al levels from 0·03 to 0·87% have been determined. The tensile specimens were cast in situ, cooled at 60°C min−1 to the test temperature in the range of 1200–700°C and strained at 3 × 10−3 s−1 to failure. The reduction of area (R of A) was taken as the measure of ductility. Whereas the high P addition was found to have little influence on the hot ductility behaviour, the high Al additions resulted in a widening of the trough to higher temperatures. Thin films of deformation induced ferrite were observed throughout the wide temperature range from the Ae3 to the Ar3. Ductility did not fully recover at the high temperature end of the trough until the temperature was high enough for there to be little precipitation of AlN particles and to when ferrite films can no longer form making it easy for the austenite grains to dynamically recrystallise. Which of these possibilities is responsible for this extension of the trough at the high temperature end is not clear, although there is some evidence suggesting it may be the ferrite film forming at temperatures above the Ae3, due to segregation of Al to the γ grain boundaries. Steels with 0·2–0·4%Al also gave R of A values <40% in the temperature range of 900–750°C indicating that they may be susceptible to transverse cracking during continuous casting. Nevertheless, the steel with the highest Al content (0·87%) gave R of A values comfortably in excess of 40%. This is due to the AlN precipitates being so coarse as to not have any significant influence on ductility. The troughs for these steels are also extended at the low temperature end, ductility only recovering when the temperature falls below the Ar3 temperature. This extension of the trough at the low temperature end is probably a consequence of the high Mn level (1·5%) and high Al levels, preventing growth of the deformation induced ferrite films. The Al containing steels generally had very low N levels (0·002%) and higher N levels would be expected to extend the troughs to even higher temperatures, because the increased volume fraction of AlN may lead to deeper troughs.

Ti/Al Interaction and Austenite Grain Control in Crankshaft Manufacturing with 38MnSiVS5 Steel

38MnSiVS5 steel is similar to 38MnVS6 steel (EN), the difference being the addition of a small Ti content. Typical Ti and Al contents in the chemical composition of 38MnSiVS5 steel are Ti=0.020 and Al=0.035 mass%. Both elements combine easily with nitrogen, especially Ti, and it has been observed that relatively high Al levels are harmful for austenite grain size control at reheating temperatures. In this work 38MnSiVS5 steel is used to manufacture a large number of castings, varying only the Ti and Al contents and obtaining ingots with a different Ti/Al ratio in each case. The results show that abnormal growth of the austenitic grain occurs irrespective of the Ti and Al contents, due fundamentally to the partial dissolution and coarsening of TiN precipitates. However, the steels with high Al contents present worse behaviour due to the formation of a second type of precipitates, namely AIN, which quickly dissolve between 1000 and 1100°C, causing a drastic decline in local pinning forces that gives rise to more pronounced abnormal growth of the affected grains.

Aluminium-phosphorus interactions on growth and some physiological traits of carrot and radish plants

aluminium treatment caused a significant decrease in root length and dry matter yield in the shoots and roots of carrot (Daucus carotaL.) and radish (Raphanus sativusL.) plants. this reduction was concomitant with a decrease in the accumulation of soluble sugars and total amino acids, whereas a significant increase in the proline content of the shoots and roots was detected. Soluble protein remained more or less unchanged when Al was applied at low and moderate levels. However, at higher Al levels, the losses in soluble sugars were accompanied by increases in soluble protein in radish, whereas in carrot the opposite effect was observed. The application of phosphorus fertilizer to al-treated plants counteracted the toxic effect of aluminium by increasing root elongation and dry matter production. This was associated with high contents of soluble sugars and soluble protein as well as ca, mg and p, especially at low and moderate levels of aluminium

High Aluminum Levels Accompanied by Near-Neutral pH in Outflow from a Forest Watershed in Aichi Prefecture, Japan

We found a high concentration of dissolved aluminum accompanied by almost neutral pH in stream water within a suburban secondary forest underlain by granite bedrock. We aimed to clarify the characteristics of the high Al levels in runoff by observing the chemical properties of spring water, stream water and surface soils. The mean pH values of spring water and stream water were 6.09 and 6.44, and the mean concentrations of dissolved Al of each after filtration with 0.45 μm membrane were 66 μmol/L and 41 μmol/L, respectively. The concentrations of dissolved Al in these waters were extremely high for such pH levels. There was no relationship between dissolved Al concentration and dissolved organic carbon (DOC), which, if it did exist, would be considered an indicator of organic species of Al in the stream water. The concentration of dissolved Al was highly correlated with Fe concentration but not with Si. The total concentration of water-soluble Al in soil extracts from the surface soils around the stream was extremely high, and the concentrations of dissolved Al, Fe and Si were highly correlated. These results suggest that the high concentration of Al in the spring water and stream water are derived from weathering of aluminosilicates and that Al might be dissolving in water as inorganic colloidal species.

The beneficial effect of aluminium and the role of citrate in Al accumulation in Melastoma malabathricum

* Here we investigated the beneficial effect of aluminium (Al) on the development of the Al accumulating plant Melastoma malabathricum. * Seedlings of M. malabathricum were cultivated in a nutrient solution containing 0.5 mM Al and compared with barley (Hordeum vulgare). In addition, roots of M. malabathricum were divided into one part growing in a nutrient solution, and the other part growing in a calcium solution. Al (0.5 mM) was applied to either solution. * Al-induced improvements of the root activity contributed to a growth enhancement in M. malabathricum. Al exposure without nutrients did not increase root growth and Al accumulation in the leaves. The beneficial effect, however, was induced by the combination of Al and nutrients. * We suggest that without nutrients roots are not able to synthesize an adequate amount of citrate that is required for transporting Al to the leaves. High Al levels in the plant tissues and/or an interaction of Al with particular nutrient elements in the apoplast of root cells appear to be essential to exert the beneficial effect of Al.

The distribution and phylogeny of aluminium accumulating plants in the Ericales.

The distribution of aluminium (Al) accumulation in the Ericales is surveyed, based on semi-quantitative tests of 114 species and literature data. Al accumulation mainly characterises the families Diapensiaceae, Pentaphylacaceae, Symplocaceae, Ternstroemiaceae, and Theaceae. Al accumulation is consistently present or absent in most families examined, but the character appears to be more variable in a few taxa (e.g., Lecythidaceae, Myrsinaceae). Although the interfamilial relationships within the Ericales require further research, the ability to accumulate high levels of Al appears to show considerable taxonomic significance. While the majority of Al accumulating Ericales includes woody, tropical plants, the feature is remarkably present in several herbaceous Diapensiaceae, which have a distribution in cold to temperate areas. The association of different mycorrhizae types with plant roots is suggested to play a role in the exclusion of high Al levels from the shoot.

Aluminium accumulation in leaves of 127 species in Melastomataceae, with comments on the order Myrtales.

The distribution and systematic significance of aluminium accumulation is surveyed based on semi-quantitative tests of 166 species, representing all tribes and subfamilies of the Melastomataceae as well as a few members of related families within the Myrtales. The character is strongly present in nearly all members of the Memecylaceae and in most primitive taxa of the Melastomataceae, while non-accumulating taxa are widespread in the more derived tribes of the Melastomataceae. The variable distribution of Al accumulation in advanced clades of the latter family is probably associated with the tendency to herbaceousness, although it is unclear whether the more herbaceous representatives have developed more specialized Al-response mechanisms that may exclude high Al levels from the shoot. It is hypothesized that Al accumulation is symplesiomorphic for Melastomataceae and Memecylaceae, and that the feature characterizes the most primitive families in the Myrtales. Indeed, Al accumulation is also characteristic of Crypteroniaceae, Rhynchocalycaceae and Vochysiaceae. Crypteroniaceae and Rhynchocalycaceae probably take a basal position in a sister clade of the Memecylaceae and Melastomataceae, while Al accumulation suggests a basal position for Vochysiaceae in the Myrtaceae clade.

Ethylene Polymerization Behavior of Tris(pyrazolyl)borate Titanium(IV) Complexes

A set of Tp‘TiCl3 and Tp‘TiCl2(OR) complexes containing tris(pyrazolyl)borate ligands with diverse steric properties has been evaluated for ethylene polymerization under MAO activation conditions (Tp‘ = HB(3-mesitylpyrazolyl)2(5-mesitylpyrazolyl)- (TpMs*), HB(3-mesitylpyrazolyl)3 - (TpMs), HB(3,5-Me2-pyrazolyl)3 - (Τp*), HB(pyrazolyl)3 - (Tp), BuB(pyrazolyl)3 - (BuTp)). The activity of Tp‘TiX3/MAO varies in the order TpMs*TiCl3 (10c) > TpMsTiCl3 ≫ Τp*TiCl3, TpTiCl3, BuTpTiCl3, Tp*TiCl2(OtBu), Tp*TiCl2(O-2-tBu-C6H4). The activity of 10c/MAO is similar to that of Cp2ZrCl2/MAO. High MAO levels or addition of AlMe3 decrease the activity of 10c/MAO, probably due to coordination of AlMe3 to the active Ti species. The predominant chain transfer mechanism for 10c/MAO is chain transfer to AlMe3, which results in broad molecular weight distributions at low Al/Ti ratios (Al/Ti = 200−1000). At very high Al levels (10c/5000 MAO or 10c/1000 MAO/4000 AlMe3) bimodal molecular weight distributions comprising a major low molecular weight fraction (M w/M n ca. 3) and a minor high molecular weight fraction are observed, which suggests that several active species are present, only one of which undergoes efficient chain transfer to Al.

A Dendrochemical Survey of Sugar Maple ( Acer saccharum Marsh) in South-Central Ontario, Canada

A dendrochemical survey of sugar maple (Acer saccharum Marsh) was conducted insouth-central Ontario, which encompassed twenty-two sites in areas that both exceeded orwere below the published Critical Loads with respect to acid deposition. Areas thatexceeded the Critical Load were located remote from point emission sources, but were alsocharacterized by thin, nutrient-poor soils overlying the Precambrian Shield. ThepHaq of surface soils (A-horizon) was lower at sites on the Precambrian Shield andwater-extractable concentrations of Ca decreased exponentially with decreasing soil pH. Significant polynomial relationships between soil pH and soil Ca and sugar maple growth,assessed as cumulative tree-ring growth between 1949 and 1998, explained 40% and 37% ofthe variation in sugar maple growth respectively, with lowest growth associated with lowsoil pH and low soil Ca. Furthermore, there was a significant linearrelationship between wood Ca concentrations (averaged between 1949 and 1998) and soil pHand concentrations of several trace elements in wood (Mn, Pb, Zn, Cd, Sr and Rb) were greater atlow soil pH. Poor sugar maple growth was associated with low wood Ca concentrations andhigh wood Al levels, which together accounted for 43% of the variation in sugar maplegrowth in a multiple regression model. None of the other wood chemistry variablescontributed significantly to the model. These data suggest that sugar maple grows poorlyon acidic soils with low Ca and high Al levels. Although such acidic podzols occurnaturally in some areas overlying the Precambrian Shield, if Ca losses due to aciddeposition and/or harvesting exceed inputs through weathering and deposition(i.e. exceed Critical Load), sugar maple growth may be adversely affected and ultimately lead toincreased incidence of sugar maple decline.

MINERAL COMPOSITION OF FORAGE LEGUMES AS INFLUENCED BY ALUMINUM

The nutritional quality of plants is primarily controlled by concentrations of essential nutrients and potentially detrimental substances, and these are influenced to a great extent by phytotoxic aluminum (Al). Alfalfa (Medicago sativa L.), red clover (Trifolium pratense L.), and birdsfoot trefoil (Lotus corniculatus L.), cultivars were grown in nutrient solution culture under controlled conditions and the effects of Al on growth and mineral composition of plants were evaluated. With a few exceptions, Al significantly reduced shoot and root dry weights, and generally increased the concentrations of elements in shoots. Further increases in Al tended to reduce mineral concentrations in each species and cultivar. This was probably related to root injury, reduced dry matter accumulation at higher Al, and reduced nutrient demand at higher Al levels. In alfalfa and red clover cultivars, elemental equivalency ratios for K/Mg and K/(Ca + Mg) increased, and ratios for Ca/P decreased in plants grown with Al. Forage with low Ca/P indicates poor quality, and high K/Mg and K/(Ca + Mg) ratios indicates higher grass tetany hazard to animals. Most of the elemental concentrations and nutrient ratios were similar for Al-sensitive and Al-tolerant cultivars of alfalfa and red clover. The species and cultivars used in this study had inter- and intraspecific differences in growth and nutrient concentrations, both in the presence and absence of phytotoxic levels of Al.

STUDIES IN MONODOMINANT FORESTS IN EASTERN MATO GROSSO, BRAZIL: I. A FOREST OF BROSIMUM RUBESCENS TAUB

The occurrence of a monodominant tropical forest dominated by the tree species Brosimum rubescens Taub. (Moraceae) in the transition zone between the cerrado region and the Amazonian rain forests along the Araguaia valley in the state of Mato Grosso in Brazil is reported. A 6000m2 (40×150m) area located in the central portion of a forest (14°50′47″S, 52°08′37″W) on the Eldorado Farm in Nova Xavantina was sampled to determine the structure, phytosociology and soil properties. A total of 44 tree species was found in the forest, with a Shannon diversity index (H′) of 2.37 and the Pielou evenness index (J′) of 0.63. These values were similar to those reported by other workers in an Amazonian monodominant forest dominated by Peltogyne gracilipes. Average tree density equal or greater than (≥) 5cm dbh was 1066ha−1 and basal area 37.46m2 ha−1. Dead standing individuals represented 7.03% of the total density and lianas 8.12%. The main families were Moraceae, Rubiaceae, Burseraceae, Hippocrateaceae and Leguminosae–Caesalpinioideae. The species with the highest importance value indices were B. rubescens (124.55), Amaioua intermedia var. brasiliana (32.97), Cheiloclinium cognatum (22.41), Tetragastris balsamifera (19.58) and Protium pilosissimum (16.64). Brosimum rubescens alone accounted for 85.5% of the individuals ≥30cm dbh, 80.35% of those ≥20cm dbh, 57.33% of those ≥10cm dbh, and 35.85% of those ≥5cm dbh. The forest was composed of upper, middle and lower storeys. Diameter distribution was unbalanced for the community and for the main species, suggesting that establishment has been episodic. The surface soil was acid, with high exchangeable Al levels and low fertility, as is the case for most cerrados and Amazonian forests. The availability of K was in the range of adequacy, as compared with most native soils. However, concentrations of available Mg in the soil was higher than that of available Ca, with Mg/Ca ratios above three, unlike most cerrados and Amazonian forests, but similar to the soils of many monodominant tropical forests reported in the literature. Soils were characterized by high concentrations of available Fe. Besides the high Mg/Ca ratios, a high proportion of K as compared with the bivalent cations Ca and Mg, and toxicities of Fe and Mn due to strong acidity could be factors influencing the occurrence of species in this forest.

Effects of oral aluminum on essential trace elements metabolism during pregnancy.

The present study was conducted to assess in rats the effects of oral aluminum (Al) exposure on calcium (Ca), magnesium (Mg), manganese (Mn), copper (Cu), zinc (Zn), and iron (Fe) accumulation and urinary excretion. Three groups of plug-positive Sprague-Dawley (SD) rats were given by gavage 0, 200, and 400 mg/kg/d of Al(OH)3 on gestational days 1-20. Three groups of nonpregnant female SD rats of the same age received Al(OH)3 by gavage at the same doses for 20 consecutive days. At the end of the treatment period, 24-h urine samples were collected for analysis of Al and essential elements. Subsequently, all animals were sacrificed and samples of liver, bone, spleen, kidneys, and brain were removed for metal analyses. With some exceptions, the urinary amounts of Al, Mn, and Cu excreted by pregnant animals as well as the urinary levels of Al excreted by nonpregnant rats were higher in the Al-treated groups than in the respective control groups. Although higher Al levels were found in the liver of pregnant rats, the concentrations of Al in the brain of these animals were lower than those found in the same tissues of nonpregnant rats. With regard to the essential elements, tissue accumulation was most affected in pregnant than in nonpregnant animals. In pregnant rats, the hepatic and renal concentrations of Ca, Mg, Mn, Cu, Zn, and Fe, as well as the levels of Ca in bone, and the concentrations of Cu in brain were significantly higher in the Al-exposed groups than in the control group. According to the current results, oral Al exposure during pregnancy can produce significant changes in the tissue distribution of a number of essential elements.