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Acid rain is formed by fusion between atmospheric water with contaminated air. Although with naked eyes you can’t see a difference between normal and acid rain, the effects of rainfalls are deadly even for big forest areas. The term of acid rain should be understood not only as rainfall but also as a toxic fog or even snow.

What causes the acid rain?

First of all let’s answer a question: what the acidity is. From Chemistry lessons you might remember the term of pH scale. It takes values between 0 to 14, where pH smaller than 7 is acid, bigger than 7 – alkaline and equal 7 – neutral. Natural rainwater is always a bit acidic (about 5.6), because rain water reacts with carbon dioxide from air, which results in carbonic acid. However, it is not a problem for environment. Problems start when rainwater is getting mixed with atmospheric gases, such as:

  • sulfur dioxide
  • nitric oxides (NOx)
  • hydrogen sulfide
  • hydrogen chloride

These gases are formed and emitted to the atmosphere as a result of fuel combustion (i.e. petroleum, gas, carbon), industrial production, evaporation of nitric fertilizers but also - volcanic activity. Reaction between water (water vapor) and mentioned above compounds results in acid rain.

Why acid rain is dangerous for environment?

Acids contained in rainfalls damage leaf wax. Wax protects leaf peel from uncontrolled vaporization. Water loss and diffusion of acids to the leaf interior causes disintegration of green pigment - chlorophyll, which leads to disorder in the photosynthesis process. It brings leaf discoloration and loss, and in effect, the plant can’t continue to produce an energy. Additionally, in case of greater amounts of acid rain, plants are also attacked from the bottom. Acidified soil transmits these chemical compounds into roots, which results in decay of plants. It also happens that there is a destruction of entire forests resulting in a characteristic landscape of the broken, discolored and stripped trees. With the death of plants in a given area  the entire forest life is also void since vegetation is the basis of animal food chain.

An equally important problem is the acidity of the water reservoirs, where stagnant waters are particularly exposed. Fishes cease to proliferate even at water pH of 5.4 and it should be noted that the process is usually followed by excessive growth of algae. Oxygen is displaced from reservoir and it is replaced by different gases and chemical elements - also the heavy metals washed out of the soil. Gradually the destruction of life occurs in lakes. Sometimes this problem also applies to rivers.

In addition to the negative impact on the environment, acid rain also inflicts a lot of damage to buildings (especially the older ones) and metal constructions. This leads to erosion and to corrosion, and hence, to a significant material and financial losses, as well as a danger to humans, associated with the weakening of the structure elements. For example, in Cracow – a city with a frequent smog – there has been damaged many monuments including the famous Sukiennice - just because of the deteriorating effects of acid rain on limestone roughcasts.

What steps have been taken to reduce the problem?

The problem has been recognized by the civilized world since the 1970's. A number of international conventions have been accepted, then the government have ratified the protocols intended to the reduction of toxic gases emission. One of the most important inventions was wide use of catalytic converters in cars and other vehicles, which helped to reduce the quantity of sulfur and nitric oxides in engine exhausts. The emission coming from power stations and industry is currently reduced by special installations of capture and neutralization. Some harmful gases may be also combusted in dedicated adiabatic systems. Many scientists and engineers are constantly working on more efficient technological solutions in this matter.

However, the problem still exists

All things consider, the problem of acid rain still remains serious and it seems to be unresolved in the near future. It is impossible to completely reject the conventional energy, replace all fuel engines in vehicles to electric ones, and discontinue use of nitric fertilizers. Organic farming is too expensive and inefficient to become a  standard. Even if it would be possible in Europe and North America, there is still a huge part of the world which runs with less control, e.g. Asia, Africa and some parts of Latin America. It must be realized that the acid rainfall can be present even thousands kilometers from the emission spot due to migration of atmospheric acids with air currents. To finalize and conclude we should comprehend that human activity during last 50 years produced more acid rain that during the previous 30 centuries.

Dominik Sosnowski

Environment Protection student at the Warsaw University of Technology. An engineer fascinated by literature and writing; a blogger who loves close contact with nature, macro photography as well as biking in the woods.


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