Acid rain

Giuseppe Tripoli

Class 9B

Mr. Youell

March 20, 2015

One of the environmental problems that the world is facing today is acid rain. Acid rain, or acid deposition, is a rain, or any kind of precipitation, that contains high levels of nitric and sulfuric acids, caused by the atmospheric pollution.

Acid deposition can occur in the form of wet deposition or dry deposition (Fig. 1). Wet deposition is acidic rain, fog, sleet or snow. The acid from the atmosphere gets removed by the rain or other kind of precipitation and gets deposited on the surface. Dry deposition refers to particles and gases from dust and smoke that remain on the ground without precipitation.

Fig. 1   Formation of acid deposition

Acidity of the rain is based on the PH level. PH scale defines a solution’s acidity, neutrality or alkalinity. It ranges from 0 to 14 - 7 is neutral, lower PH is more acidic, and higher PH is alkaline (Fig. 2). Normal rain has a PH range from 5.3 to 6, therefore anything below this level is considered acid rain.

Fig. 2   PH scale

Acid deposition is mainly caused by the gases released during fossil fuel combustion during industrial processes, and by power plants, factories, cars, etc. These gases, sulfur dioxide (SO2) and nitrogen oxides (NOx), react with the water, oxygen and other chemicals present in the atmosphere, and form various acidic compounds (sulfuric acid, nitric acid and ammonium nitrate). It can result also from natural sources, such as volcanoes and decaying vegetation, because of the chemicals that are being released in the process.

This problem occurs especially in the Northern hemisphere because it is more industrialized and dirtier. The country most affected by acid deposition is currently China, due to their widespread use of high-sulfur coal throughout the country.

We can see the effects of this environmental problem everywhere we go, for example on car roofs, metal railings, steel bridges, pipes, statues, buildings, because it can eat even through stone and metal, the most durable of materials (Fig. 3). 

Fig. 3   The effects of acid deposition on a statue

Acid rain is really harmful, it causes damage to forests, lakes, rivers, streams, and other aquatic environments, and to all plants and animals that live in these ecosystems. Acid rain dissolves helpful nutrients before trees can absorb them, and acidic waters draw out soil toxins which trees take in. As a consequence, trees lose their leaves, become more vulnerable and they stop growing (Fig. 4). For example, in Germany and Poland half of the forests are damaged. Human health is also at risk. Sulfate and nitrate particulates can cause heart problems, bronchitis and asthma.

Fig. 4   Dead spruce

Acid rain primarily affects sensitive bodies of water, whose soils have a limited buffering capacity, that is a limited ability to neutralize acidic compounds. Some plants and animals can tolerate acidic waters better than others. However, many of them are sensitive, especially the young of most species, so fish population numbers decrease because the eggs cannot hatch. Obviously, not all species react in the same way. The chart below (Fig. 5) shows the amount of acid that some species can tolerate. However, the ecosystem is interconnected, therefore what impacts some species eventually impacts many more throughout the food chain.

Fig. 5   The amount of acidity that species can tolerate

There are several ways in which we can address this problem. Acid deposition needs to be reduced throughout the world and both society and individuals need to participate, make some effort and help. We can use alternative energy sources that do not use fossil fuels, such as nuclear, solar or hydro power, clean up industry smokestacks, restore a damaged environment, and as individuals we can conserve energy by decreasing our usage of electric appliances, whenever possible forget about our cars and walk, or buy vehicles with low nitrogen oxides emissions, etc. Even if we could stop the acid rain today, it would take many years for its harmful effects to disappear.

Sources:

http://enviroliteracy.org/article.php/2.html

http://www.epa.gov/acidrain/

http://environment.nationalgeographic.com/environment/global-warming/acid-rain-overview/

http://geography.about.com/od/globalproblemsandissues/a/acidrain.htm

http://science.howstuffworks.com/nature/climate-weather/atmospheric/acid-rain.htm