Acid Rain Tim Novak

What is Acid Rain? Acid Rain is also know as acid deposition Acid deposition is the sum total of wet and dry atmospheric deposits that lead to excess loading of hydrogen ions within a geographic region Wet deposition refers to acidic rain, fog, and snow; while dry deposition refers to acidic gases and particles The deposited hydrogen ions are usually associated with sulfate and nitrate ions which are produced from a variety of atmospheric reactions involving water, oxygen, light, and two general classes of compounds: nitric and sulfuric acids Has a pH < 5.6

Causes Sulfur dioxide and nitrogen oxides are released into the atmosphere These compounds come from both natural and anthropogenic causes Anthropogenic sources include: emissions from transportation, electric power plants, industry and fuel burning Natural sources include volcanos and decaying vegetation

Impacts on the Environment Decreased pH increases metal solubility and can increase metal release from sediments and soils The strength of the effects depend on several factors, including how acidic the water is, the chemistry, and the buffering capacity of the soils involved Acid rain accelerates the normal, natural rate of stone deterioration, so that we may prematurely lose buildings and sculptures, etc

More Impacts on the Environment Acid rain gases are carried many miles to rural areas harming forests and lakes by weakening natural defenses Acid rain is absorbed into the soil making it virtually impossible for these trees to survive. As a result of this, trees are more susceptible to viruses, fungi and insect pests Poisonous metals such as aluminum, cadmium and mercury, are leached from soils through reacting with acids.

What effect does the soil and underlying bedrock have on acid rain? Some rocks can reduce (neutralize) the acidity of the rain, whereas other rocks have no effect Calcite, magnesium, and dolomite are some minerals that greatly mitigate the effects of acid rain. Calcite and dolomite are the principle minerals that make up the rocks limestone, dolomite, and marble. These rocks do not withstand acid rain weathering well. Granite is fairly resistant to acid rain due to its combination of silicate minerals such as feldspar and quartz

What controls the pH of precipitation? At the global scale, natural sulfur production is probably greater than anthropogenic production Production is greatest in the northern hemisphere Most of the sulfur that is released to the atmosphere by humans is from fossil fuel burning and metal smelting Nitrogen oxides are mainly produced from automobile exhaust One sixth of all anthropogenic sulfur produced in the world comes from an area in the NE US that constitutes 0.6% of global land

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