Precipitation acid deposition

Committee on Atmospheric Transport and Chemical Transformation in Acid Precipitation, "Acid Deposition Atmospheric Processes in Eastern North America" National Academy Press Washington, D. C., 1983. 

The very first speaker at this Study Week, Professor Phillips, mentioned the goal of a government-sponsored study in the U.K., explicitly leaving out — saying these goals were specifically left out — some of the more interesting (to chemists and physicists) aspects of the problem and those include those phenomena which can be referred to as the source-receptive relationship in acid precipitation, acid deposition. Specifically I think it is important to... 

Amino-3 5-diiodobenzoic acid. In a 2 litre beaker, provided with a mechanical stirrer, dissolve 10 g. of pure p-aminobenzoic acid, m.p. 192° (Section IX,5) in 450 ml. of warm (75°) 12 -5 per cent, hydrochloric acid. Add a solution of 48 g. of iodine monochloride (1) in 40 ml. of 25 per cent, hydrochloric acid and stir the mixture for one minute during this time a yellow precipitate commences to appear. Dilute the reaction mixtiue with 1 litre of water whereupon a copious precipitate is deposited. Raise the temperature of the well-stirred mixture gradually and maintain it at 90° for 15 minutes. Allow to cool to room tempera-tiue, filter, wash thoroughly with water and dry in the air the yield of crude acid is 24 g. Purify the product by dissolving it in dilute sodium hydroxide solution and precipitate with dilute hydrochloric acid the yield of air-dried 4-amino-3 5-diiodobenzoic acid, m.p. >350°, is 23 g. 

J. S. Chang and co-workers. The Regional Acid Deposition Model and Engineering Model, State-of-Science—Technology Report 4, National Acid Precipitation Assessment Program, Washington, D.C., 1989. 

Calcium carbonate makes up the largest amount of deposit in many cooling water systems (Fig. 4.16) and can be easily detected by effervescence when exposed to acid. Deposits are usually heavily stratified, reflecting changes in water chemistry, heat transfer, and flow. Corrosion may be slight beneath heavy accumulations of fairly pure calcium carbonate, as such layers can inhibit some forms of corrosion. When nearly pure, calcium carbonate is white. However, calcium carbonates are often intermixed with silt, metal oxides, and precipitates, leading to severe underdeposit attack. 

One of the major effects of acidic deposition is felt by aquatic ecosystems in mountainous terrain, where considerable precipitation occurs due to orographic lifting. The maximum effect is felt where there is little buffering of the acid by soil or rock structures and where steep lakeshore slopes allow little time for precipitation to remain on the ground surface before entering the lake. Maximum fish kills occur in the early spring due to the "acid shock" of the first meltwater, which releases the pollution accumulated in the winter snowpack. This first melt may be 5-10 times more acidic than rainfall. 

The extent and severity of the damage attributable to acid depositions are difficult to estimate, since impacts vary according to soil type, plant species, atmospheric conditions, insect populations, and other factors that are not well understood. Nitrates in precipitation may actually increase forest growth in areas with nitrogen-deficient soils. 

Stensland, Gary . Whelpdale, D.M. Oehlert,G. Precipitation Chemistry, In ACID DEPOSITION LONG TERM TRENDS, National Academy of Sciences Press, Washington, DC, 1986, pp 128-199. 

Irving, P. Ed. Acidic deposition State of science and technology. National Acid Precipitation Assessment Program, Washington, DC, 1990. Clark, T.L., Denise, R.L., Seilhop, S.K., Voldner, E.C., Olson, M.P., and Alvo, M. International sulfur desposition model evaluation. Atmospheric Environment Service, Publication No. ARD-87-1, 1987, Downsview, Ontario, Canada. 

Cowell. D.W. Lucas, A.E. Potential of soils and bedrock to reduce acidity of incoming acidic deposition in Ontario, In Assessment of Aquatic and Terrestrial Acid Precipitation Sensitivities for Ontario, Ontario Ministry of... 

Cronan, C. S. (1984). Biogeochemical responses of forest canopies to acid precipitation. In "Direct and Indirect Effects of Acidic Deposition on Vegetation" (R. A. Linthurst, ed.), pp. 65-79. Butterworth, Boston, MA. 

The inventory made by Buijsman in the Netherlands should be caracterised as a quite rough estimate. This is demonstrated by the assumptions on which he based his calculations. For instance he neglected the emission from stables for laek of reliable data. If the Government wants to reduce the acid precipitation, there will be paid attention to ammonia. As it is released from ground level sources reduction of ammonia emission has more effect on acid deposition in the region than in the case with S02 and NOx. 

Acid rain the precipitation phenomenon that incorporates anthropogenic acids and other acidic chemicals from the atmosphere to the land and water (see also Acid deposition). 

In spite of the occurrence of natural events such as the eruption of Krakatoa, scientists are now well aware that human activities can have serious long-term effects on the Earth s atmosphere. The hrst such effect to be noticed historically was the increase in acid precipitation resulting from the combustion of fossil fuels. Acid precipitation is also known as acid rain or acid deposition. The second, discovered in the mid-20th century, was the depletion of stratospheric ozone. More recently, atmospheric scientists established a link between so-called greenhouse gases and global climate change. 

Nitric acid is very soluble in water, so it dissolves in rain and other forms of precipitation and is carried to Earth s surface in the form of acid deposition. 

Acid rain arises from the oxidation of S02 and N02 in the troposphere to form sulfuric and nitric acids, as well as other species, which are subsequently deposited at the earth s surface, either in precipitation (wet deposition) or in dry form (dry deposition). The contribution of organic acids has also been recognized recently (see Chapter 8). These oxidation and deposition processes can occur over relatively short distances from the primary pollutant sources or at distances of a fOOO km or more. Thus both short-range and long-range transport must be considered. 

It is evident that other methods end reagents may be adopted. For example, the original solution In aqua regia may be concentrated by evaporation, until it is very much reduced in quentlty then add about throe-fourths of its bulk of spirit of wine, and, lastly, a saturated solution of chloride of ammonium. By these reagents the platinum will be thrown down as a yellow Crystalline precipitate, while the solution filtered from this, and treated with sulphate of iron or boiled with oxalic acid, deposits geld. 

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