Acid rains broadly speaking is a term used to describe the several ways the acids fall out of the atmosphere or rather precipitate acid deposition. Acid rain has two parts. It could be either dry or wet. Dry deposition usually refers to the acidic gases and particles which fall back on Earth through dry deposition and comprise almost half of the acidity in atmosphere. Whereas, wet deposition refers to the various forms of wet precipitation like fog, snow and rain.
The effects of such precipitation is all around and effects water bodies, vegetation, animal life as well as has a huge impact on human life.
The effects of acid rain on lakes and streams, vegetation and animal life is well known but the effect it has on stones, sand layers and especially building structures is even more stark and the decay process that follows on building materials, paints, heritage structures are irreparable and irreplaceable.
The oxides of sulphur and nitrogen gases along with their particulate matter derivatives degrades the visibility range as well as have harmful effects on public health before these comes down along with rain water. Once they precipitate along with rain water and snow then the deterioration process begins.
Acid rains and the dry depositions of these acidic particles increase and contribute hugely to the corrosion of building materials, building paints, building stones like marble and various forms of granites and lime stones. These acid rains aggravate and reduce the life values of buildings, bridge structures, cultural heritage buildings, monuments, memorials etc.
Apart from these effects the aggravation could also include dirtying of buildings, various structures, stains on monuments leading to inflated maintenance costs, replacement of paints on a regular basis, cracks on structures and degradation in building strengths.
The effects of acid rain on building structures are multiple. The buildings outer coverings of whether it’s made up of marble or limestone cover gets worn out due to chemical action of acids on both marble and limestone.
Moreover, the long term effects of these acid action leads to cracks and fissures which opens up the building to water seepage and damage to concrete and steel.
The effects of acids on marble are as follows:
Marble is calcareous and hence is very sensitive to the action of acids which slowly degrades it. The marble although is not soluble in normal water reacts adversely with acid rain water. The action of acid rains forms soluble salts which get washed away. This irreplaceable action on a long term leads to fissures and cracks in the outer cover of the building walls.
The acid rain usually contains the dissolution of oxides of carbon, nitrogen and sulphur in water to form carbonic acid, nitric acid and sulphuric acid which reacts adversely with the calcium carbonates of marble.
CaCO3 + H2SO4 $\rightarrow$ CaSO4 + H2O + CO2
The normal rain having weak acids could take hundreds of years to degrade a monument but the human intervention and release of heavy amount of toxic fumes caused the acids rain to become more acidic and regular which is effecting the damages all around.
The effects of Acid Rain are as follows:
- The effects of acid rain is all around and could affect terrestrial animals and plants , aquatic life, rock structures, modern man-made structures and heritage buildings.
- The acid rain causes soil pH to change as well. Soil has this natural way of neutralizing the acidic effect but is not always uniform and hence we could see the same amount acid rain in some areas has less tell-tale effect on soil crusts while others in a very aggravated condition.
- The acid rain could damage the leaves and weaken the trees in a forest system and limit the nutrient content of the surrounding soil.
- The acid rain could cause the oxygen holding capacity of a water body to change affecting the aquatic life. Many of the species will either die or migrate to other water bodies due to the change in pH of water.
- Terrestrial life forms might have various skin related diseases, may lose their fur cover, and also the loss of vegetation indirectly affects their feeding style.
- The acid rain on marble could result in black crusts which are nothing but crystals of calcium salts of nitrates, carbonates and sulphates.
The acid rains causes buildings to react adversely with their limestone cover or marble layers and degrade the look, strength as well as increase the maintenance costs of structures.
Acid rain reacts with limestone cover of buildings by making washable salts, black crusts, deep stains, and open up the exterior of a building to water seepage, concrete degradation and steel rusting making the overall building weaker.
Acid rain causes wide form of damages to buildings. Mainly the exteriors but if the effect is severe then the water seepage which follows the cracks appearance in exterior walls leads to water marks, paint peeling and in some cases damages to electrical gadgets as well due to short circuiting.
- Damages to exterior walls
- Degradation of paints and limestone coverings
- Degradation to marble structures of buildings
- Appearance of black crusts
- Cracks and fissures in exterior walls
- Damages to exterior paints and peeling
- Water seepage and subsequent damages to concrete structures as well as electrical linings
- Long term effects on building strength which progressively weakens with each acid rain attack
- Acid rains are the water dissolution of the oxides of mainly carbon, nitrogen and sulphur.
- The gaseous Carbon di oxide combines with rain water and forms the dilute carbonic acids (H2CO3).
- The gaseous nitrogen di oxide combines with water and forms dilute nitric acids (HNO3).
- The gaseous sulphur di oxide combines with water and forms the dilute sulphuric acids (H2SO4).