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[en] Highlights: • Wear rate of nitrided HEAs was lower than that of as-cast HEAs in the same condition. • The wear mechanism of as-cast alloys in air was abrasive wear of oxide particles. • The wear mechanism of the nitrided HEAs in air was adhesive wear and abrasive wear. • The wear mechanism of HEAs in acid rain was abrasive, oxidative and corrosive wear. • The lubrication action of deionized water and acid rain led to the lower wear rate.
[en] The effect of air pollution is felt world wide. Acid rain brings havoc to all forms of life on this planet. One of the many consequences of acid rain is the release of luminum (III) from the soil. Tea is the plant which selectively accumulates soluble aluminium from the soil. The short article is to alert heavy tea drinkers as aluminium is a neuro-toxic metal. (author)
[en] Although acid rain and its harmful environmental consequences have been recognised and documented in the industrialised countries of Europe and North America there have been few studies of this phenomenon in other regions of the globe. Recent measurements in some tropical countries have demonstrated the occurrence of acid rain. It was therefore considered necessary to set up a routine rainwater acidity monitoring programme in Brunei Darussalam in order to provide a database which would be of use in assessing any potential environmental impacts in the country. This paper describes the rainwater acidity monitoring programme that was initiated in 1995 by the Brunei Meteorological Service as part of the World Meteorological Organisation (WMO) Global Atmosphere Watch (GAW). Wet-only deposition samples were collected using an automatic precipitation collector. Rainwater pH was determined in an on-site laboratory immediately upon sample collection. The pH of 185 samples collected so far varied between 4.27 and 6.27. 91% of the samples had pH below 5.6 indicating the occurrence of acid rain in Brunei Darussalam
[en] In most urban areas in Europe and Northern American serious corrosion impacts on buildings and cultural monuments have been caused by emissions of pollutants. The rapidly increasing pollution levels in many of the developing countries also exert a serious threat to materials. Beside the very important role of SO2 also the direct or synergistic effect of NO2 and O3, the particulates and rain acidity may contribute in an important way to materials degradation. Results from extensive international field exposure programmes i. e. within the UN/ECE have enabled development of dose-response relations which describe the effect of dry and wet deposition of pollutants on corrosion of different material groups. In most of the industrialized countries decreasing trends of sulphur and nitrogen pollutants and of acidity of precipitation have resulted in decreased corrosion rates. The concept of acceptable levels of pollutants is a useful tool in planning of abatement strategies and for defining of conditions for a suitable development in the field of corrosion of construction in the atmosphere. (Author) 12 refs
[en] Degradation mechanisms of unglazed solar absorber surfaces based on aluminium substrate were studied. Rough graphite-aluminium surfaces were total-immersion subjected to aerated and de-aerated simulated neutral and acid rain. Test conditions were based on calculated absorber stagnation temperature and global rain acidity measurements. Changes in optical properties, elemental composition and sample mass were examined by spectrometry, energy dispersive X-ray spectrometry and thermogravimetry, respectively. The absorbers exhibited almost no degradation at pH value of 3.5. At pH 5.5 alumina on the surface hydrated significantly degrading the optical properties of the surfaces severely in most cases. Therefore these absorber surfaces can not be recommended to be used in non-glazed applications if they are exposed to rain with pH exceeding ∼ 3.5-4.5. The total-immersion test needs to be developed further as the test results exhibited poor temperature and time dependency thus preventing accurate service lifetime estimates. Still, these tests were useful in determining favourable and non-favourable operating conditions for the absorber surfaces based on aluminium substrate. (author)
[en] In large urban centers, the toxicity of metal mixtures may be enhanced by physicochemical factors and environmental variables, including pH. Rio Grande, a municipality located in the extreme south of Brazil, has soils with high levels of contamination due to urban and industrial activities and a high prevalence of acid rain events. Previous studies have shown that contact with elutriate of these soils can cause physiological and reproductive changes. Thus, the objective of the present study was to evaluate, through animal experimentation, the effects of a metal-contaminated soil, acidified by hydrofluoric acid at two different pH values (5.2 and 3.6), on the health of offspring of rats exposed during gestation and lactation. Female Wistar rats were gavaged daily for 42 days (gestation and breastfeeding) with soil elutriate contaminated with metals, using solvent with different pH values (6.0, 5.2, and 3.6). The following parameters were evaluated in their offspring: body and organ weight, length, appearance of developmental characteristics, and swimming. Experimental groups in which the progenitors were exposed to the solution at pH 3.6 exhibited a delayed increase in weight as well as motor deficit, with a decreased weight (onset) and length (beginning and end), while exposure in association with soil was an aggravating factor for the damages to the body. Exposure to the solution at pH 5.2 decreased the initial weight of the animals, impaired some parameters of weight development, and caused motor deficit on the 14th day. These novel findings reveal that the exposure of progenitors to environmental stressors can compromise the health of the offspring. Special attention should be given to populations living in areas with high prevalence of acid rain.
[en] Retention of SO42- was investigated in Galician soils throughout an intense regime of acidification. Experiments consisted of the addition of an H2SO4 solution (pH 2.7) to columns of 6 soils of contrasting properties over 1,2 or 5 months. Leachates were obtained continuously throughout the experiment for analysis, and analysis made of the solid fractions after 1, 2 or 5 months. The greatest capacities for retention of SO42- were found in soil developed from serpentine and micaschist; the lowest in soils from granite, slate and sandy sediments. The surface horizons, especially those rich in organic matter, displayed low retention of SO42-. The amount of SO42- adsorbed throughout the experiment depended on the content of crystalline forms of Fe and with the Fe and Al extracted with dithionite-citrate. The low retention of SO42- in the organic horizons and the slightly negative relation with the organic matter suggest an inhibitory effect of the organic matter on the SO42- retention process. Results of the study show that, under conditions of moderate acidity, SO42- retention occurs in the form of adsorption; in strongly acidic conditions, the precipitation of aluminium-sulphate minerals may provide an additional retention mechanism. 41 refs., 3 figs., 4 tabs
[en] The effects of rain acidity on field-grown Summered apple trees (Malus domestica Borkh) under natural conditions were investigated. One group of four trees was exposed to ambient rainfall. Four other groups were covered with rainshields and received water, pH 5.6, 4, and 3, respectively, as simulated rain. Simulated acid rain, particularly at pH 3, adversely affected fruit production in terms of individual fruit weight, fruit set, fruit appearance (necrosis and russetting of the peel) and dry weight. Ambient rain was not found to cause significant reductions in apple weight. Ambient rain was not found to cause significant reductions in apple fruit production in this study
[en] Two integrated assessment models, one for climate change on a global scale (IMAGE 2) and another for the regional analysis of the impacts of acidifying deposition (RAINS), have been linked to assess the impacts of reducing sulphur emission on ecosystems in Asia and Europe. While such reductions have the beneficial effect of reducing the deposition of acidifying compounds and thus the excedance of critical loads of ecosystems, they also reduce the global level of sulphate aerosols and thus enhance the impact of increased emissions of greenhouse gases, and consequently increase the risk of potential vegetation changes. The calculations indicate that about 70% of the ecosystems in Asia would be affected by either acid deposition or climate change in the year 2100 (up from 20% in 1990) for both sulphur emission scenarios (controlled and uncontrolled), whereas in Europe the impacted area would remain at a level of about 50%, with a dip early next century. (author)
[en] There are many environmental benefits arising from the generation of electricity from nuclear power. These are accompanied by a minimal detrimental environmental impact, which is strictly regulated and monitored to a far greater degree than any other comparable industry. Because it does not produce greenhouse gases or acid rain emissions, the generation of electricity from nuclear energy is a vital component of a sustainable energy future for our planet. (Author)