Surface waters acid rain

Acid rain control will produce significant benefits in terms of lowered surface water acidity. If acidic deposition levels were to remain constant over the next 50 years (tlie time frame used for projection models), the acidification rate of lakes in the Adirondacks that are larger than 10 acres would rise by 50 percent or more. Scientists predict, however, that the decrease in SO emissions required by the Acid Rain Program will significantly reduce acidification due to atmospheric sulfui Without the reductions in SO2 emissions, the proportions of aquatic systems in sensitive ecosystems that are acidic would remain high or dramatically worsen. 

For more than a century, a number of different aluminum alloys have been commonly used in the aircraft industry These substrates mainly contain several alloying elements, such as copper, chromium, iron, nickel, cobalt, magnesium, manganese, silicon, titanium and zinc. It is known that these metals and alloys can be dissolved as oxides or other compounds in an aqueous medium due to the chemical or electrochemical reactions between their metal surfaces and the environment (solution). The rate of the dissolution from anode to cathode phases at the metal surfaces can be influenced by the electrical conductivity of electrolytic solutions. Thus, anodic and cathodic electron transfer reactions readily exist with bulk electrolytes in water and, hence, produce corrosive products and ions. It is known that pure water has poor electrical conductivity, which in turn lowers the corrosion rate of materials however, natural environmental solutions (e g. sea water, acid rains, emissions or pollutants, chemical products and industrial waste) are highly corrosive and the environment s temperature, humidity, UV light and pressure continuously vary depending on time and the type of process involved. ... 

Even rain is not pure water. Reports from the U.S. Geological Survey show that it contains 2.3—4.6 ppm of soflds, or a yearly precipitation of 2.5—5 t/km. Recently (ca 1997), work conducted ia the United States and Europe has underscored the rather dangerous results of iacreased use of fossil fuels, where the SO and NO emissions that end up ia the rain lower its pH from 5.6 (slightly acidic) for uncontaminated rain, to acid rains. Such acid rain has serious effects on surface waters (1). About 40 x 10 t of SO and 25 x 10 t of NO were emitted ia the United States ia 1980. There are, however, encouragiag trends the 1970 Clean Air Act has led to a gradual reduction ia these emissions, bringing the SO emissions down from the previous levels cited by 10% by 1990, and the NO emissions down by 6%, with a consequent slight decrease ia rain acidity. A part of the Clean Air Act is also iatended to cap SO emissions from major poiat sources at 13.5 x 10 t (2). Between 1994 and 1995, total SO emissions ia the U.S. decreased remarkably by 13% and total NO emissions by 8%. 

Acid deposition refers to the transport of acid constituents from the atmosphere to the earth s surface. This process includes dry deposition of SO2, NO2, HNO3, and particulate sulfate matter and wet deposition ("acid rain") to surfaces. This process is widespread and alters distribution of plant and aquatic species, soil composition, pH of water, and nutrient content, depending on the circumstances. 

High concentrations of SO, can produce tempo-rai y breathing difficulties in asthmatic children and in adults who are active outdoors. Sulfur dioxide also can directly damage plants and has been shown to decrease crop yields. In addition, sulfur oxides can be converted to sulfuric acid and lead to acid rain. Acid rain can harm ecosystems by increasing the acidity of soils as well as surface waters such as rivers, lakes, and streams. Sulfur dioxide levels fell, on average, by 39 percent between 1989 and 1998. 

Many details in building construction may permit rain water to enter and this may be retained in crevices in metal surfaces, or between a metallic and some other surface. Water may drip on to metal surfaces. These conditions, which can involve a greater risk of corrosion than exists where a metal is exposed to the normal action of the weather, are more severe when the water contains dissolved acids, alkalis or salts derived from the atmosphere or from materials with which the water comes into contact. Normal supply waters can also cause corrosion. 

One reason that the term acid deposition is preferred to the term acid rain is that sulfuric and nitric acid formed by the processes described may return to Earth s surface in either a wet or a dry form. Wet deposition consists of acids dissolved in water, as occurs in acid rain or acid snow. Dry deposition occurs when acids or nonme-tallic oxides remain in gaseous form or adhere to solid particles, on which they are carried to the ground. About half of the components of acid deposition fall back to Earth in each of these two forms, wet and dry. 

SO Bronchoconstriction. cough. Cellular injury, chlorosis, withering of leaves and abscission. Precursor to acid rain acidification of surface waters with community shifts and mortality of some aquatic organisms. Possible effect on uptake of Al and other toxic metals by plant roots. Weathering and corrosion. Defacing of monuments... 

This salt was discovered by J. R. Glauber 1 in 1659 he prepared it by the action of nitric acid on volatile alkali—ammonium carbonate—and called it nitrum jlammans. Ammonium nitrate is an artificial product, its occurrence in nature is quite exceptional. Ammonium nitrate, sulphate, and carbonate occur in small quantities in the atm. from which they are carried by rain and snow to the surface waters of the earth. A. Bobierre 2 measured the amount, month by month, in the air of Nantes R. A. Smith determined the amount in the air of towns, etc., in Great Britain C. Ochsenius, in the air of Paris and A. Levy, and F. Fischer,... 

Acid rain primarily affects sensitive bodies of water, that is, those that rest atop soil with a limited ability to neutralize acidic compounds (called buffering capacity ). Many lakes and streams examined in a National Surface Water Survey (NSWS) suffer from chronic acidity, a condition m which water lias a constant low (acidic) pH level. The survey investigated tlie effects of acidic deposition in over 1,000 lakes larger than 10 acres and in thousands of miles of streams believed to be sensitive to acidification. Of the lakes and streams surveyed in the NSWS, arid rain has been determined to cause acidity in 75 percent of the acidic lakes and about 50 percent of tlie acidic streams. Several regions in the U.S. were identified as containing many of the surface waters sensitive to acidification. They include, but are not limited to, the Adirondacks. the mid-Appalachian highlands, the upper Midwest, and the high elevation West. 

With few exceptions, air pollutants ultimately fall by gravity to the surface of die earth. On land, pollution of the soil and freshwater lakes and rivers and ultimately the groundwater occurs, Fallout on the seas and oceans also occurs, but unless radioactive, the effects are less easy to discern except on die long term. It is indeed difficult to separate air and water pollution. The relationship is explored in the article on Wastes and Pollution. The winds contribute both to the spread and, in some instances, to the contribution of air pollutants. Frequently, as in the case of acid rain, the precipitation of water (an excellent solvent) in the fonn of rain, snow, sleet, ice pellets, etc. causes entrainment of pollutants (gases, mists, particles, etc.). Thus the soils, rocks, lakes, and rivers are subject to the corrosive and biodestructive processes brought about by the presence of alien substances. Acid rain is described later in this article. 

It is interesting to note how interrelated the topics of water, air, and solids (soil) pollution are. Acid rain, for example, commences as an air pollutant and ends up as a soil and water pollutant. See also Pollution (Air). Thus, water pollution may be direct or indirect. Because they have a mass, air pollutants ultimately fall to Earth s surface and thus pollute the oceans, bodies of freshwater, and the land. 

It should be kept in mind that, in spite of these major variations in the CO2-carbonic acid system, virtually all surface seawater is supersaturated with respect to calcite and aragonite. However, variations in the composition of surface waters can have a major influence on the depth at which deep seawater becomes undersaturated with respect to these minerals. The CO2 content of the water is the primary factor controlling its initial saturation state. The productivity and temperature of surface seawater also play major roles, in determining the types and amounts of biogenic carbonates that are produced. Later it will be shown that there is a definite relation between the saturation state of deep seawater, the rain rate of biogenic material and the accumulation of calcium carbonate in deep sea sediments. 

Acid rain can vary from pH 1 to 5, normal rain is in the pH 5 to 6.5 range, and normal surface water (streams, lakes, etc.) falls between pH 5 and 8. Most living cells have an internal pH of 7. 

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