Environmental Impact of Acid Rain
Introduction
Acid rain is a broad term referring to a mixture of wet and dry deposition (deposited material) from the atmosphere containing higher than normal amounts of nitric and sulfuric acids. The precursors, or chemical forerunners, of acid rain are emitted by natural sources such as volcanoes and decaying vegetation, and also from man-made sources, primarily emissions of sulfur dioxide (SO2) and nitrogen oxides (NOx) resulting from fossil fuel combustion. In the United States, roughly 2/3 of all SO2 and 1/4 of all NOx come 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. The result is a mild solution of sulfuric acid and nitric acid. When sulfur dioxide and nitrogen oxides are released from power plants and other sources, prevailing winds blow these compounds across state and national borders, sometimes over hundreds of miles.
Effects on Soil and Plant Life
Acid rain has many ecological effects, but none is greater than its impact on lakes, streams, wetlands, and other aquatic environments. Acid rain makes waters acidic, and causes them to absorb the aluminum that makes its way from soil into lakes and streams. This combination makes waters toxic to crayfish, clams, fish, and other aquatic animals. Some species can tolerate acidic waters better than others. However, in an acidic environment, both the number of species that can survive and the overall population numbers of these species decline. As lakes and streams become more acidic biodiversity is reduced. Acid rain has eliminated insect life and some fish species, including the brook trout in some lakes, streams, and creeks in geographically sensitive areas, such as the Adirondack Mountains of the United States.
In addition to aquatic bodies, acid rain negatively affects the soil. Acid rain leaches away vital nutrients such as calcium and magnesium that trees need to grow, and it releases aluminum in the soil, which makes it hard for trees to take up water. Trees' leaves and needles are also harmed by acid rain, reducing the trees' ability to photosynthesize.
Effects on Human Health
The human health effects of acid rain are indirect. By damaging these environmental areas, the sulfur dioxide and nitrogen oxides that cause acid rain—SO2 and NOx, respectively—are also changing the makeup of the air we breathe, thereby affecting human health. These gases interact in the atmosphere to form fine sulfate and nitrate particles that can be transported long distances by winds and inhaled deep into people's lungs. Fine particles can also penetrate indoors. Many scientific studies have identified a relationship between elevated levels of fine particles and increased illness and premature death from heart and lung disorders, such as asthma and bronchitis.
Effects on Infrastructure
Acid rain also affects man-made materials and structures. The corrosive effects of acidic water on stone and metal can be seen on old gravestones and metal outdoor sculptures, but it can also affect infrastructure, including buildings and transportation systems. The corrosive nature of acid rain causes paint to peel, corrosion of steel structures such as bridges, and weathering of stone buildings and monuments.
Prevention and Mitigation
The most basic solution for air pollution is to end its root causes: quit coal and move to 100% clean, renewable energy. Accomplishing this requires a multi-pronged approach that involves reducing our dependence on fossil fuels and improving our energy efficiency. Another part of the solution is to plant trees, as they absorb CO2, one of the main contributors to global warming. Governments also play a crucial role in reducing acid rain. They can regulate the amount of CO2 that factories or power plants emit, or they can invest in renewable sources of energy, such as wind and solar power.