Acid rain

Origin of acid rain

Acid rain, as the name suggests, is precipitation characterised by a low pH. When we refer to acid rain, we mean that its pH value oscillates below 5. What makes precipitation acidic? All this is due to airborne pollutants and their transformation products, mainly oxides. Prominent among these are carbon dioxide, sulphur trioxide or nitrogen oxides. One should also mention halogens which are released into the atmosphere. All these chemicals come into contact with water vapour and oxygen contained in the air. This results in the formation of acids from the corresponding acid anhydrides. Even though they are relatively diluted, they still reduce the pH of rain as precipitation and negatively affect the environment.

Is mankind alone responsible for the formation of acid rain?

No! Some sulphur or nitrogen oxides are released into the atmosphere as a result of natural processes, such as volcanic eruptions. Other natural factors leading to acid rain are lightning discharges or forest fires. However, it is important to remember that humans are responsible for the scale of acid rain events. One anthropogenic source of pollution is the burning of fossil fuels which are insufficiently purified and contain, for example, small amounts of sulphur. Their processing results in the formation of sulphur oxides, for example. The vast majority of pollutants in the atmosphere are the consequence of burning unsuitable raw materials in boilers, furnaces, vehicle engines or machines. Pollution is also generated by the combustion of other materials, including, for example, plastics. The introduction of nitrogen oxides into the environment also results from combustion processes, with about a third coming from the combustion of petrol and diesel fuels. A big problem in terms of acid rain formation is traffic. The use of cars, especially older ones, which often do not have adequate catalytic converters, places a heavy burden on the environment. Factories and production facilities are also other emitters of pollution. A number of laws and regulations force them to be environmentally friendly, but this is not 100% achievable in every situation.

What are the effects of acid rain?

Acid rain is undoubtedly a negative phenomenon, affecting not only the environment but also human health.

The most important effects caused by acid rain include:

• Acidification of natural water bodies, such as lakes and rivers. The carbonate balance is disturbed, resulting in, among other things, the loss of numerous species of aquatic insects, crustaceans, fish, as well as aquatic vegetation.
• Soil erosion. Acid rain contributes to the mobility of cations and various metals, including lead, cadmium or copper. In addition, soil acidification causes a change in the speciation of certain elements, i.e. in the chemical form in which they are present in the soil. For example, some of them change from an undissolved to a dissolved form and easily penetrate the water contained in the soil layer. This has further consequences, as run-off from contaminated land ends up in water bodies and negatively affects not only animals and plants, but also humans.
• Destruction of the protective layer on the needles and leaves of plants. This disrupts the photosynthetic process and, in addition, damages the root system. As a result, both plant growth and resistance are impaired, and this often leads to plant death or a significant reduction in yield (in the case of crops).
• Deterioration of architectural elements due to accelerated corrosion. This is particularly dangerous for buildings constructed of sandstone, limestone and marble. The most severe losses are in the case of cultural properties. Importantly, the effects of acid rain on buildings are often not immediately visible. They usually become noticeable after some years.
• Human respiratory diseases. In addition, acid rain can contribute to cancer and chronic diseases.

How can acid rain be prevented?

Acid rain occurs primarily where there are long-term emissions of harmful substances into the environment. But this does not mean that other areas are safe. Unfortunately, moving air masses transfer these pollutants.

For many years, numerous efforts have been made globally to reduce acid rain as much as possible. First of all, new or modified industrial technologies are being introduced to reduce the emissions of harmful substances into the atmosphere as much as possible. These measures include reducing burning of fuels that contain sulphur and sulphur compounds, for example, using more efficient solutions to capture sulphur and nitrogen from exhaust gases, or developing more efficient catalytic converters for the automotive industry. The search for alternative fuels to move away from coal or crude oil is also constantly being pursued. International cooperation is important in preventing acid rain, as the problem is global. Globally introduced environmental restrictions are helping to combat this phenomenon.

Among the measures that each of us can take to reduce the formation of acid rain is, first and foremost, saving energy. Even the smallest actions like turning off lights, switching off unused appliances or using heating thermostats are meaningful. It is also important to look for other modes of transport than a private car. If possible, it is advisable to switch to a bicycle or cover small distances on foot. In addition, the level of public awareness of the subject of acid rain is important. Collective responsibility and knowledge of how to protect the environment are fundamental in an effective fight for a clean environment.