From the early times through the Industrial revolution to the Space Age, humans have produced inventions that use many of the earth's varied energy resources to make living easier. In many cases the energy comes from burning fossil fuels such as coal, oil, and natural gas. Some of the inventions that make our lives easier are also causing pollution or the release of harmful substances into the environment. One form of pollution is acid rain, rain that is more acidic than normal. Acid rain can damage plants, animals, soil, water, building materials, and people.
Scientists have discovered that the major cause acid rain is air pollution from the burning of fossil fuels. The smoke and fumes from burning these fossil fuels rise into the atmosphere and combine with moisture in the air to form acid rain. The main chemicals in air pollution that create acid rain are sulfur dioxide and nitrogen oxides. Acid rain usually forms high in the clouds where sulfur dioxide and nitrogen oxides react with water, oxygen, and oxidants. This forms a mild solution of sulfuric acid and nitric acid. These chemical reactions that change air pollution into acid rain can take from several hours to several days. Sunlight increases the rate of these reactions. Rainwater, snow, fog, and other forms of precipitation containing these mild solutions of sulfuric and nitric acids fall to the ground as acid rain. Years ago, when smokestacks were only a few stories tall, pollution from the smokestacks usually stayed near the ground and settled on the land nearby. This only caused unhealthy conditions for plants and animals near the smokestacks. To reduce this pollution, the government passed laws permitting the construction of very tall smokestacks. At the time, people thought that if the pollution was sent high into the air it would no longer be a problem. Sending the pollution high into the sky increases the amount of time that the pollution stays in the air. The longer the pollution is in the air, the greater the chance that the pollutants will form acid rain. In addition, the wind can carry these pollutants for hundreds of miles before they become joined with water droplets to form acid rain. For that reason, acid rain can affect areas far from the polluting smokestacks.
One way acid rain is hurting people is by weakening trees, crops, and other plants that help to clean the air we breath and provide us with food. Scientists believe that acidic water dissolves the nutrients and helpful minerals in the soil before the trees and other plants can use them to grow. At the same time, the acid rain causes the release of toxic substances such as aluminum into the soil. These are very harmful to trees and plants, even if contact is limited. Even if the soil is well buffered, meaning it is resistant to pH change, there can be damage from acid rain. Forests in high mountain regions, the only place where the soil is naturally well buffered, receive additional acid from acidic clouds and fog that often surround them. These clouds and fog are often more acidic than rainfall. When leaves are frequently covered with acid fog, their protective waxy coating can wear away. The loss of this coating damages the leaves and creates brown spots. When the leaves are damaged, they cannot produce enough food energy for the tree to remain healthy. Once the trees ...