Our Acid Earth

The Earth’s oceans, soils, and freshwater bodies are acidifying. Acid rain was in the media a lot in the 80’s and 90’s but has been forgotten as of late. This ignored menace is having many negative effects on the environment. Fossil fuel combustion, transportation emissions, deforestation, and the mining of coal and metal ores are just some of the human activities that are contributing to the acidification of the Earth.

What is acidification and what effect is it having on the environment?

Acidification is a complex process but can be loosely defined as a lowering of pH due to the input of acidic substances. The pH of soils is important because it affects nutrient availability. Many plants cannot grow in nutrient-poor acidic soils and acid rain is causing a decline in the health of vegetation. Increased acidity in the oceans is having a detrimental effect on marine organisms that have calcite body parts such as corals, crustaceans and plankton. The increased acidity literally dissolves these body parts away. Corals have other problems too, including bleaching and being blown up for use in concrete production. Plankton are an important part of the marine food chain and their decline may lead to the loss of other marine species that rely on them for food. Runoff from highly acidified soils and acid mine drainage makes its way into freshwater lakes and streams where it can be extremely toxic to fish. Unusually low pH waters are associated with human activities far more than with natural acidification processes.  The primary agent of acidification is acid rain. Acid rain is caused by the emissions of  pollutants to the atmosphere such as carbon dioxide, sulfur dioxide and nitrogen oxides. The three acids of major concern to the Earth are sulfuric acid, nitric acid and carbonic acid.

Waldschaeden_Erzgebirge_3
Damaged vegetation

Both sulfuric and nitric acids are acidifying soils and freshwater bodies on Earth while carbonic acid is acidifying the oceans. The main source of sulfur dioxide and carbon dioxide emissions is coal-fired power plants that generate electricity for the energy hungry human population. Vehicle exhausts, aircraft and other forms of transportation are the main source of nitrogen oxides to the atmosphere, while the intensive use of nitrogen fertiliser adds additional nitrogen gases to the mix. All of these gaseous pollutants get washed out of the atmosphere as acid rain and deposited at the Earth’s surface.

The Earth system has some mechanisms that act to ‘buffer’ or neutralise some of the acidity being unleashed on it, principally from the weathering of rocks that brings neutralising nutrients like calcium and magnesium into contact with the acids. However, these mechanisms are being overwhelmed by the sheer rate of acid production and are inadequate to offset much of the damage.

What are the current global trends in the emissions of these pollutants?

Global fuel consumption continues to rise (BP, 2012).  The carbon dioxide concentration in the atmosphere carries on climbing upwards and is contributing to global warming and ocean acidification. Sulfur dioxide emissions have been decreasing in the Western hemisphere thanks to the Clean Air Act (Wikipedia, 2013) but have been increasing rapidly in developing countries like China and India. Global deforestation is increasing and adding further carbon dioxide to the atmosphere. Global food production and an increasing transportation sector (Vestreng et al., 2009) in many parts of the world are leading to the production of more nitrogenous pollutants that make their way into the atmosphere.

As the Earth’s human population continues to grow explosively, the demand for food, fuel and electricity will grow with it. Acid rain will continue to affect the Earth until fossil fuel reserves run out or alternative means of energy are used.

However this global experiment on the environment turns out,  what we know is the increasing dependence on fossil fuels is contributing to more extreme weather events, global temperature rise, the melting of glaciers and ice caps and the acidification of the Earth’s oceans, soils and freshwater bodies.

There must be a global shift to reduced energy consumption and alternative energy methods. As individuals we can also play a part. Reducing one’s carbon footprint through personal choices can have a significant accumulative effect on per capita greenhouse gas emissions. Using less electricity and unplugging unused appliances, walking and using alternative transport more often, buying locally produced organic food that doesn’t require the intensive use of fertilisers and pesticides, having meat-free days, and educating friends and family on environmental issues are all ways that each individual can do their bit to ensure that the environment we have today is one that can be passed on to future generations.

References:

BP (2012) Statistical Review of World Energy June 2012, [Online], Available at http://www.bp.com/content/dam/bp/pdf/Statistical-Review-2012/statistical_review_of_world_energy_2012.pdf (Accessed 23 July 2013).

Rice, K.C., Herman, J.S. Acidification of Earth: An assessment across mechanisms and scales. Appl. Geochem. (2011),
doi:10.1016/j.apgeochem.2011.09.001

Vestreng, V., Ntziachristos, L., Semb, A., Reis, S., Isaksen, I.S.A., Tarrason, L., (2009) Evolution of NOx emissions in Europe with focus on road transport control measures, Atmos. Chem.Phys. 9, 1503 – 1520.

Wikipedia (2013) Clean Air Act [Online], Wikipedia, Available at http://en.wikipedia.org/wiki/Clean_Air_Act_(United_States) (Accessed 22 July 2013).

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