Acidic fallout has become one of the damaging and controversial forms of air pollution in the industrialized world. Acid deposition are sulfur and nitrogen oxides released from electrical power plants, industrial boilers, mineral smelting plants, and motor vehicles that burn fossil fuels. Sulfur and nitrogen oxides combine with moisture in the atmosphere and return to earth as sulfuric and nitric acids.
A good example is the result of the Persian Gulf War. More than 500 Kuwait oil wells were on fire, spreading sulfureous gases and toxic particles over a vast region extending from Turkey in the north to Iran in the east. The air pollution has produced black rain, a vile greasy precipitation laden with sulfuric acid and petroleum compounds. Black rain has been reported in Adana, Turkey; in Baghdad, Iraq; and in Busheler, Iran. Environmentalists fear that the black rain could fall, affecting millions of people dependent on that food.
The effects of acid fallout can be seen throughout ecosystems. Acid deposition damages leaf surfaces, preventing some tree species from retaining water. Acidic water can leach minerals such as calcium, magnesium, and potassium from leaves and from the soil, which can damage tree roots, block nutrient absorption and impair water transport making trees more susceptible to drought, insects and other sources of stress.
Acidified water itself can kill many of the fresh water fingerlings and larvae. That disrupts the food chain. In saltwater, nitrates from acid deposition can boost the nitrogen content of coastal estuaries, creating algae blooms that cause oxygen depletion and the suffocation of fish and other aquatic plants.
We are learning that pollutants in the atmosphere can be very damaging. Soot and smoke particles washed from the air by rain may blacken and discolor buildings. Sulfur oxides from the combustion of coal combine with rainwater to make sulfuric acid, which can peel paint, rust bridges, and slowly eat away stone monuments and stone buildings. Atmospheric pollutants can also harm crops and people.
Certain weather conditions can bottle up pollutants in a small area, with disastrous effects. In 1948 an atmospheric condition called a “temperature inversion” caused tragedy to Donora, Pennsylvania. The first air pollution episode in the United States. A layer of warm air slid into the valley between the cool air on the ground and the cold air above. Cooler air above, could not rise into the layer of warm air, but instead was trapped into the valley. Exhaust fumes, smoke and gases from autos, trains, steel mills, and other industries poured into the trapped air until they shut out the sun. People with respiratory diseases were struck down by the burning atmosphere. Before a wind blew away the inversion layer and cleared the air four days later, over one-third of the population became seriously ill, and twenty people died.