Acid Rain Conditions Research Articles

Surface tension of atmospheric humic‐like substances in connection with relaxation, dilution, and solution pH

Humic‐like substances (HULIS) were isolated by a solid‐phase extraction procedure from PM2.5 fraction urban‐type atmospheric aerosol samples collected in downtown Budapest, Hungary, in the nonheating season. Their amount was derived, and the surface tension properties of their pure solutions were investigated. Carbon content of HULIS accounted for 54% of the water‐soluble organic carbon and for 19% of organic carbon in the aerosol. Solution of pure HULIS in concentrations corresponding to real incipient cloud droplets decreased the surface tension of water by about 30%, and the major decrease occurred within several tens of seconds. In diluted solutions, however, the thermodynamic equilibrium in surface tension was only reached after several hours, but the equilibrium depression value was still remarkable, about 18%. Detailed analysis of the relaxation curves implied that the kinetics of the surface tension depression should be regarded as and described by a diffusion‐controlled process. The surface tension curves as a function of the HULIS concentration after an elapsed time of up to about 100 s resembled the curves observed earlier, but the shape of and tendency in the equilibrium curve (the isotherm) was rather different. The deviations were linked to physicochemical properties of certain classes of compounds within the HULIS. The surface tension depended on the solution pH as well; the smallest depression was observed at about pH = 5, and it was increased by an additional 13% for strong acidic or basic conditions; hence the role of surface tension in cloud droplet formation under acid rain conditions is further amplified.

Acid deposition in the eastern United States and neural network predictions for the future

Back-propagation type neural networks were trained on total sulphur dioxide emissions from power plants and measured field data on precipitation chemistry. These trained networks were then able to predict seasonal changes in sulphate, hydrogen, nitrate, and ammonium ion concentrations caused by projected decreases in sulphur dioxide emissions from power plants in the eastern United States. Results showed that by 2010 the proposed reductions in sulphur dioxide emissions by the U.S. electric power utilities would just be sufficient to reduce acid rain conditions to the levels where human health problems are avoided. However, pollution from acid rain would still be impacting considerable regions of the north-eastern United States and south-eastern Canada causing other environmental damage such as loss of fish in acidic lakes. Key words: acid rain, desulphurization, modelling, neural networks, pollution.

A LONG-TERM MONITORING OF ACID RAIN AT YOKOSUKA CITY

In Japan, the natural environment has been harmed by air pollution such as acid rain. In recent years, the problem has become more and more serious as the acidities of rainfall and snowfall decrease. Acid rain is generally defined as rain, snow and fog with a concentration of hydrogen ions (pH) less than 5. 6. The large causes for acid rain are the pollutants of NOx and Sox generated from waste gas and factory exhausts due to the human activities. Both pollutants are converted into the ions of NO3- and SO42- in the atmosphere, and these ions are dissolved in rainfall as HNO3 and H2SO4, respectively. That is, the acid rain is rainfall with very high concentrations of HNO3 and H2SO4. In this investigation, based on the measurement of pH value and the results of chemical microanalyses, some conclusions are formed about the real condition and ion-composition of acid rain at Yokosuka city, Kanagawa. The authors have carried out the monitoring on rainfalls since May 1991 at Yokosuka city near the Tokyo Bay. It has been observed that the rainfalls at this city have very high concentrations of NO3- and SO42-

Trace metal leaching behavior studied through the use of parametric modeling of water borne soil particles fractionated with a split-flow thin cell.

Leaching of particle-bound metals affects the ability of settling ponds and other engineered structures to remove metallic pollutants, and leaching behavior is related to particle size. In this investigation, water borne soil particles were leached and fractionated with a split-flow thin cell, and the metal loadings were quantified as a function of particle size. For comparison of the metal-loading curves, different empirical modeling procedures were investigated to convert the data to a precise functional form suitable for quantitative comparison of changes in differential loading as a function of particle size. Results of this investigation are presented for a soil sample before and after leaching caused by simulated acid rain conditions. Following simulated acid rain leaching, the shape of the differential distribution curves change, and these changes reflect the particle size mediated leaching behavior. For the soil used in this demonstration, simulated acid rain leaching shifted the differential loading toward larger particle sizes, and the magnitude of the shift varied significantly among the metals. Because settling rate decreases as the square of particle size, this could potentially affect management decisions for settling ponds receiving these particles. The high precision afforded by the analysis allows the development of insight into the leaching mechanisms through comparing "partial" acid rain leaching with "total recoverable" leaching by EPA Method 3050.

Erosion by acid rain, accelerating the tracking of polystyrene insulating material

Because outdoor insulating materials in service are subjected to numerous wet and dry cycles, it is necessary to establish their performance in acid rain. The erosion effect of acid rain on atactic polystyrene insulating material is investigated using accelerated ageing by artificial acid rain. The degradation mechanisms of material structure and tracking resistance are discussed. The experimental results reported here show that the erosion of acid rain causes the degradation of the surface chemical and physical structures of polystyrene (PS) material so that the surface conductivity of aged material increases. Under electrical stress, the surface discharge current increases, and the local surface is deteriorated so that the tracking is initiated earlier and the material rapidly fails. The degradation rate of PS material in acid rain varies as function of the ion concentration, pH and conductivity of acid rain. Only the severe acid rain of high acidity and conductivity can exert an influence on PS insulating material. The concentration of actual rainwater is insufficient to lead to obvious erosion on PS insulation. PS insulation could resist on the erosion of normal acid rainwater. Even though clear degradation occurs with strong acid rain, PS could behave quite well in mild acid rain conditions.

What is wrong with aluminium? : The J.D. Birchall memorial lecture

Aluminium chemistry has features in common with two other groups of elements: (1) divalent magnesium and calcium, and (2) trivalent chromium and iron. The essential differences between the first group and aluminium are explored and it is shown that the much higher acidity of aluminium makes it such a powerful competitor for oxygen-donor ligands, opposite functions of both magnesium and calcium, in cells that its presence is damaging. By way of contrast aluminium is a weaker acid than ferric ions but it is more available. It was necessary for iron to be utilised in the presence of aluminium so special methods had to be devised to distinguish between them. In essence aluminium has always, throughout evolution, been a threat to the biological chemistry of all these three elements. We shall examine this chemistry and then explore the relationship of calcium and aluminium under acid rain conditions.

Modelling leaching of inorganic Hg(II) in a Scandinavian iron-humus podzol — validation and long-term leaching under various deposition rates

Increasing mercury contents are reported from freshwater systems and fish in northern Europe and North America. Mercury input from soils is a major source with the leaching being affected by increased atmospheric mercury deposition compared to pre-industrial times and by other environmental conditions such as acid rain. The results of a mathematical model-calculation of vertical inorganic Hg(II) leaching in a Scandinavian iron-humus podzol under different atmospheric input rates of mercury are presented. Leaching under background rain conditions was calculated to be considerably stronger than under acid rain conditions. Increasing fractions of deposited soluble or solute atmospheric mercury were leached from the Of(h)-horizon with decreasing soil content of soluble mercury under acid rain conditions; this effect was less pronounced under background rain conditions. The steady state concentrations of soluble mercury of the upper soil horizons were calculated and compared with the actual concentrations of total (= soluble + insoluble mercury) and extractable (= estimate of soluble) mercury measured in these horizons. The results indicate that even if the deposition of airborne mercury to soil is strongly reduced, the total mercury content of the soil decreases only slowly. It may take decades or even centuries before a new steady state concentration of total mercury is established in the soil. The decrease of the mercury concentration in the Of(h)-horizon is probably largely dependent on the turnover of organic matter, binding most of the deposited airborne mercury in an insoluble form. Hence, present day mercury leaching is likely to be dominated by mercury deposited during former times and temporarily retained in an insoluble form in the organic matter.

Modeling Cretaceous‐Tertiary boundary events with extant photosynthetic plankton: effects of impact‐related acid rain

Griffis, K. & Chapman, D. J. 1990 10 15: Modeling Cretaceous-Tertiary boundary events with extant photosynthetic plankton: effects of impact-related acid rain. Lethaia, Vol. 23, pp. 379–383. OSIO. ISSN 0024–1164. An acid rain phenomenon has previously been proposed as one of the consequences of a bolide impact contributing to the extinctions at the Cretaceous-Tertiary boundary. This hypothesis has been tested by observing the growth responses of four organisms under simulated acid rain conditions. Two of these phytoplankton, Ditylum (a diatom) and Thoracosphaera (a dinoflagellate). are genera that persisted through the boundary, while the other two, Coccolithus (a coccolithophorid) and Gonyaulax (a dinoflagellate), are post-boundary genera. Ditylum and Coccolithus survive the acid rain simulation. but with the loss of scales in Coccolithus. The two dinoflagellate are sensitive to acid rain simulations. with Gonyaulax unable to survive beyond seven days. The results indicate that acid rain may have contributed to the Cretaceous-Tertiary boundary extinctions. but that the changes resulting from the acid rain were not as severe as postulated or were short-lived and quickly dissipated. ▭Acid rain, coccolithophorids. Cretaceous/Tertiary extinctions, diatons, dinoflagellates, phytoplankton.