Acid Rain

Acid rain affects many regions in the US and Canada and poses a dire threat to forests and wildlife. "Acid rain" refers to many ways that acid may come out of the atmosphere in the form of rain, fog, or snow or in dry particles and gases. Its effects exacerbate deforestation, and causes acidification of lakes and streams. It also breaks down building materials and paints.

When acid comes out of the atmosphere as rain, fog, or snow it may enter the ground or surface water as with any other precipitation. The harm comes from the acidity of the rain, which varies from location to location and it's affects vary based on the buffering capacity and the soil, and the tolerance of local plant and animal life. Acid is deposited in the soil and affects the growth and survival of plants and animals in the area. Acid in lakes and streams may cause decreases in fish populations. Acid may also be deposited as dry particles or gases that may be deposited on building or plant life and may be later washed away by precipitation, thereby entering the ground. This combination adds to the acid already in the precipitation. Atmospheric winds may move the rain hundreds of miles from its originating location, as shown in this diagram.

"Scientists discovered, and have confirmed, that sulfur dioxide (SO2) and nitrogen oxides (NOx) are the primary causes of acid rain. In the US, About 2/3 of all SO2 and 1/4 of all NOx comes from electric power generation that relies on burning fossil fuels like coal. Acid rain occurs when these gases react in the atmosphere with water, oxygen, and other chemicals to form various acidic compounds. Sunlight increases the rate of most of these reactions. The result is a mild solution of sulfuric acid and nitric acid." -EPA

The effects are acid rain are varied, but always detrimental. The effects on lakes and streams are particularly bad because of the plant and animal life's sensitivity to acidification. Regions affected include: Adirondacks and Catskill Mountains in New York state, the mid-Appalachian highlands along the east coast, the upper Midwest, and mountainous areas of the Western United States. Some of these areas have pH values as low as 5. Little Echo Pond in Franklin, New York has been recorded with a pH of 4.2. Streams assist in the distribution of acid to soils farther away from the directly affected area. Runoff from melting snow and heavy rains may temporarily increase acidity in many areas, and may lead to fish kills.

Acid rain in water environments may cause cascade effects that harm and kill fish. When acid flows through the soils in a watershed aluminum is released and the pH is decreased, both of these conditions are toxic to fish. This may not always kill fish, but the increased stress from these toxins reduces body weight and size, reducing their ability to compete for food and habitat. At a pH of 5 most fish eggs are unable to hatch and the adult population is the last in that area. Some of the fish's prey may be less tolerant to acid than the fish themselves and this contributes to a further decrease in fish populations. The increase in acid and aluminium levels causes decay in an ecosystem. The stresses on plants and animals and the affects on predator prey relations cause decreases in biodiversity which also decreases the survivability of the ecosystem in further stresses.

Acid rain also affects both the forest floor and the trees themselves. When, acid rain enters the ground and water sources in a forest, some of the acidity may be neutralized by the soil. Differences in soil buffering capacity are the reason for diversity in the damage caused by the acid. The buffering capacity varies based on