Environmental effects of aluminium

Aluminium (Al), when present in high concentrations, has for long been recognised as a toxic agent to aquatic freshwater organisms,i.e. downstream industrial point sources of Al-rich process water. Today the environmental effects of aluminium are mainly a result of acidic precipitation; acidification of catchments leads to increased Al- concentrations in soil solution and freshwaters. Large parts of both the aquatic and terrestrial ecosystems are affected.In the aquatic environment, aluminium acts as a toxic agent on gill-breathing animals such as fish and invertebrates, by causing loss of plasma- and haemolymph ions leading to osmoregulatory failure. In fish, the inorganic (labile) monomeric species of aluminium reduce the activities of gill enzymes important in the active uptake of ions. Aluminium seems also to accumulate in freshwater invertebrates. Dietary organically complexed aluminium, maybe in synergistic effects with other contaminants, may easily be absorbed and interfere with important metabolic processes in mammals and birds.The mycorrhiza and fine root systems of terrestrial plants are adversely affected by high levels of inorganic monomeric aluminium. As in the animals, aluminium seems to have its primary effect on enzyme systems important for the uptake of nutrients. Aluminium can accumulate in plants. Aluminium contaminated invertebrates and plants might thus be a link for aluminium to enter into terrestrial food chains.     

Simple assessment of the reactive aluminium in sediments

The mobility of aluminium in sediments was evaluated through a one-step extraction with a strong chelating agent. Single and sequential extraction procedures for the extraction of Al were applied to four sediments from a polluted region. A single-step extraction with 0.05 mol L⁻¹ ethylenediaminetetraacetic acid (EDTA) was used, and compared with a standardized SEP as reference. The Al contents extracted into Na₂EDTA were in good agreement with the sequential extraction that yeilds mobile and potentially mobile portion of Al. Extracted EDTA contents make up more than 70% of the first-three-step sum of the five-step extraction procedure. Thus, Na₂EDTA extraction of Al could be applied to assess aluminium mobility changes in sediments and soils.     

Unusual sources of aluminium and heavy metals in potable waters

Aluminium in water supplies derives from natural sources and from the use of Al₂(SO₄)₃ in water treatment. Heavy metals such as Pb, Cu, Zn and Cd can be added to water from pipework and solder. However, it is apparent that AI and other metals in potable waters can derive from deposits on pipe walls which can be subsequently mobilised when the supply and/or treatment process is changed. Concentrations of Al in domestic supply water of the Llanbrynmair area have been shown to increase from 1 g to 50 g L^–1 during its 18 km journey along the water main. Similarly, Pb concentrations in a public building in the Aberystwyth area are found to be extremely elevated due to the metal's mobilisation from encrustations occurring on the copper pipework.     

Leaching of aluminium from cookwares -- a review

Concern over the possible relation between environmental aluminium exposure and Alzheimer's disease has prompted studies of all forms of human intake of this element including that from foods. Aluminium cookware, apart from other sources of dietary aluminium, is considered to be a potential source of this metal to human beings. Various research groups have carried out aluminium leaching experiments with food, beverages and water under different experimental conditions modified by varying the level of pH, chloride, fluoride, citrate, acetate etc. The results reported by different workers show marked discrepancies in levels of leached aluminum. The apparent reason for such discrepancy in levels of aluminum leached can be attributed to factors such as non-systematic and non-uniform experimental designs, non-standard conditions maintained during the experiments and choice of method for aluminium analysis. In order to assess accurately the contribution of aluminium ingestion by human beings through aluminium cookware, the present review emphasises the need of i) standard size aluminium plates obtained from the same lot for one set of experimentations; ii) real life cooking conditions to highlight the role of various complexing species present in food e.g. citrate, oxalate, acetate, tartrate etc.; iii) role of chemistry of aluminium in presence of acidic, basic and neutral cooking medium and iv) strict analytical control in the estimation of aluminium. Results of a systematic study by the authors conducted on the abovementioned lines are also described.     

Influence of soil-extractable aluminium and pH on the uptake of aluminium from soil into the soybean plant (Glycine max)

The effects of soil pH and other soil properties on the uptake of AI by soybean plants have been investigated in a greenhouse experiment. Six soils were compared that were developed over six contrasting bedrock types ranging widely in their AI content and other chemical and physical characteristics, namely Oxford Clay, Chalk, Lower Lias Clay, Devonian Shale, Granite and Lower Greensand. Soil pH varied naturally between soil types and each soil was also amended to give two other pH levels using elemental sulphur and/or calcium carbonate. AI concentrations in various parts of the soybean plants were determined by ICP-AES after acid digestion. The AI solubility in the soils and hence its availability to the plants was estimated using a number of different reagents designed to extract different forms of AI. The AI concentration measured in the soybean leaves was found to be predicted most accurately by the ‘available’ AI extracted from soils by 0.02 M CaCl₂. The relationship appears to the linear, with a correlation coefficient of 0.97 (p <0.01). The AI content of the leaves increases with decreasing soil pH. The relationship is non-linear with a marked increase in leaf AI for soils with pH <4.4. The amounts of ‘plant-available’ AI in the soils extracted with 0.02 M CaCl₂ was much less than that extracted with 0.05 M EDTA, although both increased markedly with decreasing soil pH. The amount of AI measured in the soybean plants was directly related to both the ‘available’ forms of AI in the soils, and also to the pH of the soils. Soil pH was identified as a major factor that controls the uptake of Al from soil into the soybean plant.     

Aluminium levels in the blood plasma of persons working in the aluminium industry

Due to the exposure to alumina in the air, workers in the primary aluminium industry are expected to exhibit a higher aluminium exposure than the general population. The additional daily intake will be less than 20 mg. The determination of aluminium in blood plasma of electrolysis-workers by flameless atomic absorption spectrometry revealed levels before shift in the range of 20–30 g/L compared to levels of less than 3 g/L in a non-occupationally exposed group. These levels refer to work in old plants with unhooded pots. The plasma levels can rise up to 60 g/L during the shift. A similar rapid change of the levels during work is seen in the urine values. Due to the delay in excretion the maximal values in the range of 5 g/h are found four hours after cessation of work. It seems therefore that only preshift samples give a reliable measure of the body burden. Compared to the much higher levels in dialysis patients the observed values in aluminium workers are not considered to be of relevance to health.     

Review of epidemiologic studies of aluminium and neurological disorders

The epidemiological study of neurological disorders is just beginning and should he continued because of the potential public health impact of these diseases on society. The most important contribution of epidemiological research is the identification of risk factors, and specific disease entities, such as Alzheimer's disease, should be studied.Ecological analysis of geographical data have associated a small increase in mortality from Alzheimer's disease and dementia with the aluminium content of drinking water. These results must necessarily be interpreted with caution because serious errors may result from inferences based on ecological analysis,e.g. the ecologic fallacy.Potential risk factors for Alzheimer's disease have been studied in case-comparison epidemiology studies conducted in Italy, Massachusetts, Colorado, Minnesota and North Carolina, but only two studies have considered aluminium exposure, through the use of antacids. Although no increased risk was found to be associated with aluminium exposure, only a small number of individuals in the studies reported antacid use, and the studies had an extremely limited statistical power to detect an association.Additional analytical epidemiology studies, either cohort or case-comparison, are required to better describe the possible relationship between aluminium and Alzheimer's disease. These studies should be designed according to well-established epidemiological principles, be conducted with no selection bias and minimum observation bias, consider potential confounding and modifying factors, and have sufficient statistical power to enable detection of low relative risks.     

Environmental and economic analysis of aluminium recycling through life cycle assessment

Aluminium is the most-used metal in the world after steel, with a wide range of applications in the industrial field owing to its physical and mechanical properties. The aim of this study was environmental and economic analysis of secondary aluminium. In particular, this study demonstrated that aluminium recycling offers many advantages to both consumers and industry:

• Increased energy savings compared to primary aluminium production;

• Recovery and reuse of raw materials for future production avoids consumption of non-renewable resources;

• Reduction in landfill waste and consequent environmental damage;

• Reduction in bauxite mining which, in turn, will reduce the socio-economic impact on populations of those countries, mainly underdeveloped, that contain mines;

• Economic advantages for Italy, the first European producer of secondary aluminium, which lacks bauxite mines and has high energy costs.

This study used the Life Cycle Assessment (LCA) method, the modified Eco-indicator 99 method for damage calculation, and the SimaPro calculation code. The study examined secondary aluminium production by ICMET, based in Reggio Emilia, Italy. The economic and environmental evaluation utilised environmental information supplied by the company.     

铝胁迫下大豆根系分泌有机酸和氨基酸的特性

采用水培法,以2个大豆(Glycine max)品种(浙春2号和浙春3号)为材料,研究铝胁迫下大豆根系分泌有机酸和氨基酸的特征.大豆根系分泌大量柠檬酸呈现低铝促进高铝抑制的现象,同时还分泌少量草酸和琥珀酸,表明大豆根系分泌有机酸与其耐铝机制有关.氨基酸分泌总量随着铝质量浓度的增大而增加.中低铝质量浓度下,大豆根系分泌的氨基酸随铝质量浓度的增大而增加.高铝浓度下,氨基酸的种类减少,各种氨基酸分泌量变化不一致.实验结果还显示,随着铝处理时间延长,铝毒害作用明显.     

Responses of the earthworm Eisenia andrei exposed to sublethal aluminium levels in an artificial soil substrate

Industrial discharges of Al are increasingly common. In this study, the activities of three antioxidases, malondialdehyde (MDA) content and changes in coelomocytes were investigated in earthworms (Eisenia andrei) exposed to different concentrations of aluminium chloride (range 0–200 mg Al kg^?1 dry soil) in artificial soils for 32 days. Within the first 16 days of Al exposure, catalase activity was elevated in most treatments, while the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) were inhibited in all treatments. After 16 days exposure, SOD and GSH-Px activities returned to normal at lower Al concentrations, but were still inhibited at higher concentrations, hence the inhibition of SOD and GSH-Px showed some exposure-level dependence during the late exposure phase. MDA content was significantly elevated from 16 days after initial exposure. Neutral Red retention time of coelomocytes decreased at the highest exposure concentrations after 32 days, and an increased proportion of cells showing membrane damage was also observed at this time using flow cytometry. We conclude that excessive Al in soils can cause oxidative stress and cell damage in earthworms. Hence, Al accumulation in the environment may present an ecological hazard through suppression of the important functions of earthworms in soil ecosystems.     

聚合氯化铝与黏土的改性对富营养水体磷和蓝藻的同步去除

为了解决富营养化水体原位除藻、除磷同步安全进行的问题,采用黏土(凹凸棒土,AT)与聚合氯化铝(PAC)的复合改性,研究了原料本身(AT、PAC)、原料直接复配(AT+PAC)与复配后再改性处理(PHAT)之间的除磷与除藻效果、铝离子与氯离子的残留风险,并对其中的机理进行了初步探讨.结果表明,改性的PHAT和PAC除磷效率高,总磷去除率可达99.14%±0.31%,显著优于AT+PAC,但PHAT的成本仅为PAC的71.10%.PAC去除无机磷(IP)和可溶性总磷(DTP)的效果更优,PHAT去除有机磷(OP)和颗粒态磷(PP)的效果更优.投加PHAT后水体Al3+和Cl-残留量均符合国家饮用水标准.PHAT对蓝藻的去除率显著高于PAC和AT+PAC,去除率可达97.15%±1.35%,且对低密度蓝藻和高密度蓝藻的去除率差异不显著.比表面积测定结果显示,来源于PHAT中的AT比来源于AT+PAC中的AT单点比表面积提高了19.10%,孔表面积提高了11.13%.且来源于PHAT中的AT在处理富营养化水体前、后的Al含量明显减少.这些结果表明,由黏土结构的优化与络合沉淀的协同所增强的架桥网捕作用可能是PHAT更高效除磷、除藻的原因.     

Reactions between aqueous zinc,aluminium and iron with increasing solutionpH

Solutions of zinc, aluminium and/or iron, as chlorides in NaCl of ionic strength 0.13 mol/l atpH 3, were mixed to give initial concentrations of 0–5, 5–50 and 10–100 g/ml, respectively. Sodium hydroxide was then added to increase thepH in a range up to 7. Turbidity was measured and equilibrium concentrations were determined after filtration (< 0.1 m). Decrease inpH on mixing suggested an immediate reaction, with the release of protons. At allpH values Zn concentration decreased with increasing initiai concentrations of Fe and Al. Adsorption and/or nucleation of Zn with Fe and Al was highlypH dependent and increased markediy with increasingpH. The particle size of the products increased with increasingpH and initial concentration of the elements. Increasing Al concentration decreased the size of Fe nucleates at a given Fe concentration. The results suggest that co-precipitation may be involved as well as adsorption. This has important consequences for the availability of Zn to plants, especially in Zn-deficient soils, and is of relevance to the products of mixing acid drainage waters with streams and lakes.     

Cu and Cd removal from wastewater by a microalloyed aluminium composite

We studied the removal of cadmium and copper from industrial wastewaters by a microalloyed aluminium composite. The composite was highly efficient, resulting in water concentrations of cadmium and copper below the maximal allowed concentrations for drinking water. Moreover, our results show that the removal mechanism is mainly based on reduction and coprecipitation, since Cd and Cu were removed from the wastewater in reduced forms as metals and hydroxides.Selected article from the Regional Symposium on Chemistry and Environment, Krusevac, Serbia, June 2003, organised by Dr. Branimir Jovancicevic     

Studies on phytotoxic effect of aluminium on growth and some morphological parameters of Vigna radiata L. Wilczek

Aluminium toxicity is a major deterrent for plant growth in acid soils below pH 5.0. This study deals with effect of aluminium toxicity on growth of mungbean (Vigna radiata L. Wilczek) seedlings. Seed germination (in %) declined with increased content of Al2(SO4)3, while promotive effect was observed at very low dosage. Different concentrations of aluminum sulphate salt were applied to mungbean seeds. Measurement of aluminium content in mungbean leaves was done through atomic absorption spectrophotometer. Root length (root and hypocotyl length) and shoot length (shoot and epicotyl length) was measured at seven days old seedling stage. Different concentrations of Al2(SO4)3 were found to have significant effect both on shoot and root length. Leaf area, fresh and dry weight was significantly reduced. Increased stomatal frequency and trichome density with an increase in concentrations of Al2(S04)3 was observed through scanning electron microscope.     

Assessing human exposure to aluminium,chromium and vanadium through outdoor dust ingestion in the Bassin Minier de Provence,France

The Western part of the “Bassin Minier de Provence”, a former coal mining area, is still occupied by old polluting industries such as a coal-fired power plant and an alumina factory. The identified pollution sources that raise more concern in the population are the emission of gases and dusts, as well as the storage of raw and transformed materials. In 2011, a preliminary survey was carried out in the area as the first step to an exposure and health risk-assessment study. This first survey intends to assess human exposure through ingestion and health risk associated with potentially harmful elements (PHEs) in ground-level dusts collected in recreational areas used by children. Dust samples were taken at 19 sites distributed across the study area, depending on the location of public parks, public gardens, playgrounds and schools. Pseudo-total concentrations of 53 elements were determined by ICP-MS. Bioaccessible concentrations were estimated using the unified bioaccessibility method. This study presents the results obtained for Al, V and Cr, which seem to be related with industry and show similar distribution patterns. PHEs presumably related to traffic or other urban pollution sources are not discussed in this study. The highest total concentrations occur in dusts near the alumina plant that have significant amounts of Al mineral phases (gibbsite and alumina). However, in these dusts only small fractions of the elements under study are in bioaccessible forms. The highest bioaccessible fractions occur in dusts collected near the coal-fired power plant. Further investigation is required to assess potential pathways of exposure and health risk in this area.     

Detection of lipid peroxidation and cytotoxicity induced by aluminium (Al) and cobalt (Co) ions in barbunia root tip cells

The aim of this study was to investigate the cytotoxic effects of different concentrations of Aluminium (Al) and Cobalt (Co) heavy metal ions on Phaseolus vulgaris L. cv Barbunia (Fabaceae) root tips. We used the germination percentage (GP), root length (RL), weight gain (WG) and micronucleus (MN) frequency as indicators of cytotoxicity and correlated these data with statistical parameters. Additionally to the cytogenetic analysis, lipid peroxidation and DNA analyses were performed in root tips of barbunia seeds treated with Al and Co metals. The seeds were divided into five groups as control, Al and Co treatment groups. They were treated with 25 and 50 ppm doses of Al and Co during 7 days. The results indicated that there was an alteration in the GP, RL, WG and MN frequency depending on the treatment dose in the seeds exposed to Al and Co metal ions when compared with the controls. Al and Co metal ions at both the doses significantly reduced the GP, RL and WG in seeds of all the treatment groups. The highest GP was observed in seeds of the control group (in proportion as 96%). 25 and 50 ppm doses of Co and Al caused 30, 50 and 42, 64% decrease of seed germination, respectively. In the control group, the final weights of all the seeds increased about 1.31 g when compared to initial weight. The mean RL of control seeds were measured as 3.71 cm at the end of experimental period. In Co andAl groups, the final weights of seeds increased about 0.34 g and 0.19 g according to initial weight at 50 ppm dose, respectively But, Al and Co ions caused a dose-dependent increase in the frequency of MN. The highest frequency of MN was observed at 50 ppm dose of Al and least frequency of MN was observed at 25 ppm dose of Co. Besides, 25 and 50 ppm concentrations of Al and Co significantly enhanced the lipid peroxidation and caused an increase in malondialdehyde (MDA) levels at both the doses. In roots treated with 25 and 50 ppm doses of Al, the increase of MDA was about 62 and 136% according to control, respectively In Co-treated roots, the increase of MDA was about 31 and 91% according to the control at 25 and 50 ppm doses, respectively The investigated parameters (except MN and MDA) were higher in the seeds exposed to Co than the seeds treated with Al. Moreover, it was observed that the yields of DNA in the seeds treated with Al andCo metals were lower than recorded in the controls. Hence, DNA yields exposed to Al and Co were run ahead on agarose gel according to the control group. The results of the present study indicate that Al and Co metal ions have toxic effects on barbunia root tip cells, and the selected parameters such as the GP, RL, WG, MN and MDA are very sensitive and useful biomarkers for biomonitoring these effects.     

Geographical associations between aluminium in drinking water and death rates with dementia (including Alzheimer's disease), Parkinson's disease and amyotrophic lateral sclerosis in Norway

Comparisons of maps and correlation and regression analysis indicate a geographical association between aluminium (Al) in drinking water and registered death rates with dementia (coded from death certificates as the underlying or a contributory cause of death) in Norway. High levels of Al in drinking water are in most cases related to acid precipitation. In general, correlations between aggregate environmental measurements and mortality are a weak source of evidence for risk factors for disease, however, and interpretations regarding cause-and-effect relationships should therefore be made with great care. The major uncertainty probably relates to the use of registered death rates with dementia as a measure of incidence rates of Alzheimer's disease. The dementia rates are correlated with population density, and it is possible that the association between AI and dementia might be due to differences in diagnosis and reporting of dementia. Thus, the present study can only be regarded as introductory, and further epidemiological studies are needed to help elucidate the role of AI in Alzheimer's disease. The results provide little evidence of an association between AI in drinking water and Parkinson's disease or amyotrophic lateral sclerosis.     

Gypsum addition to soils contaminated by red mud: implications for aluminium, arsenic, molybdenum and vanadium solubility

Red mud is highly alkaline (pH 13), saline and can contain elevated concentrations of several potentially toxic elements (e.g. Al, As, Mo and V). Release of up to 1 million m³ of bauxite residue (red mud) suspension from the Ajka repository, western Hungary, caused large-scale contamination of downstream rivers and floodplains. There is now concern about the potential leaching of toxic metal(loid)s from the red mud as some have enhanced solubility at high pH. This study investigated the impact of red mud addition to three different Hungarian soils with respect to trace element solubility and soil geochemistry. The effectiveness of gypsum amendment for the rehabilitation of red mud-contaminated soils was also examined. Red mud addition to soils caused a pH increase, proportional to red mud addition, of up to 4 pH units (e.g. pH 7 → 11). Increasing red mud addition also led to significant increases in salinity, dissolved organic carbon and aqueous trace element concentrations. However, the response was highly soil specific and one of the soils tested buffered pH to around pH 8.5 even with the highest red mud loading tested (33 % w/w); experiments using this soil also had much lower aqueous Al, As and V concentrations. Gypsum addition to soil/red mud mixtures, even at relatively low concentrations (1 % w/w), was sufficient to buffer experimental pH to 7.5–8.5. This effect was attributed to the reaction of Ca²⁺ supplied by the gypsum with OH^? and carbonate from the red mud to precipitate calcite. The lowered pH enhanced trace element sorption and largely inhibited the release of Al, As and V. Mo concentrations, however, were largely unaffected by gypsum induced pH buffering due to the greater solubility of Mo (as molybdate) at circumneutral pH. Gypsum addition also leads to significantly higher porewater salinities, and column experiments demonstrated that this increase in total dissolved solids persisted even after 25 pore volume replacements. Gypsum addition could therefore provide a cheaper alternative to recovery (dig and dump) for the treatment of red mud-affected soils. The observed inhibition of trace metal release within red mud-affected soils was relatively insensitive to either the percentage of red mud or gypsum present, making the treatment easy to apply. However, there is risk that over-application of gypsum could lead to detrimental long-term increases in soil salinity.