In the last decade or so the acid deposition phenomenon has taken prominence in all kinds of scientific discussions and seminars. The gradual acidification of water bodies and terrestrial zones has taken precedence over all other changes that are taking place around us. The effect is catastrophic in some levels and irreversible in others.
The limits of ecology are under threat and have taken a big role in identifying the atmospheric chemistry around us as well as methods of controlling them. In this article we will discuss about the immediate causes, long term effects and controlling.
The fossil fuel burning and the amount of pollutants it has spewed from the time human population has gone for industrialization is phenomenal. Once these pollutants are airborne the acidic compounds travel far and wide with wind and fall back on earth along with fog, snow, mist and rain. In some places where neither of these precipitations occurs it comes down in dry forms.
Almost all kinds of precipitation and not just rain could be considered as acidic. The acidity and alkalinity of any solution is based typically on the percentage of hydrogen ions that any water solution would contain and measured on the logarithmic potential of hydrogen scale or pH. Whenever or wherever the pH level of the precipitation is higher than the normal level and is considered to be hazardous to all forms of life we consider them as acid rains.
The industrial pollutants like carbon di oxide, nitrogen di oxide, and sulphur di oxides that either come out of industries or vehicle fumes goes up in the atmosphere and float around with the wind patterns. These gases gradually react with the atmospheric oxygen, water and other chemicals available and form the acidic compounds. The presence of sunlight enhances the rate of such reactions substantially which finally results in the formation of mild sulphuric acid as well as nitric acids. These acids precipitate in regions which are directly in the mapping zones of pollution or hinterlands.
The main causes are the pollutants factories, big industries and vehicles spew out in form of gases into atmosphere. These are the gases which go up in atmosphere and mix with the moisture laden clouds, the freely available oxygen and form the dilute form of acids. The energy from sunlight helps in increasing the rate of reaction.
Once these dilute forms of acids are formed they tend to come down with various forms of precipitation like rain, fog, and snow. The oxidation of carbon monoxide into carbon di oxide (CO + O2 $\rightarrow$ CO2) followed by CO2 + H2O $\rightarrow$ H2CO3 finally into carbonic acid.
The causes of acid rain and dry depositions are mainly the pollutants that are released by the organic fuel run vehicles, industries which release their gaseous extracts directly without filtering and reduction in green vegetation which usually helps in absorbing some of these gases.
The cycle continues and as human population keeps clearing forest area for habitation, set up industries and ply vehicles, the accumulation of these acid rain causing gases keeps building up and since gases like carbon di oxides are not reabsorbed by the green plants, they get into the moisture in atmosphere, react, and form dilute acid forms before falling back on Earth with various forms of precipitation.
Acid deposition whether wet or dry could cause effects on a short term or long term depending upon the severity of precipitation.
- Acidification effects begins with water bodies, like lakes and streams, top soil, green vegetation, aquatic lives, terrestrial animals, human population, modern day building structures and heritage monuments.
- The all-around effects damage the building exteriors and increase the limits of maintenance, periodical exchange of vital parts in bridges and other important structures.
- The severity of acid effect is more on slow moving streams or stagnant water bodies or lakes where water exchange or outlets are minimal and there is not much of buffering of water.
- The aquatic animals find it difficult to thrive in water bodies with higher concentration of acid or low pH which lowers the oxygen capacity and thus either die or look for other water bodies for survival.
- Effects of acid rain on auto vehicles is also severe as the paint cover gets damaged progressively and begins to peel off.
- Effects of acid rain on top soil results in loss of nutrients which gets washed away after turning into soluble salts.
The effects of acid rain are all across the system and not only affect the living world but also the abiotic part as well. The effect on biotic part is quick and severe, whereas the effect on abiotic part takes time, long term and irreversible.
Severity of acid rain effects might vary from one area to another depending upon the limit of buffering and how versatile the system is. The change in pH of soil could alter vegetation patterns, colors of flower, crop yield and many other things related to plant metabolism.
The human aspect of acid rain cause is ultimate and covers almost all kinds of interventions that lead to accumulation of these acidic gases in atmosphere. The natural causes of acid rains were prevalent even before industrialization but it never caused or increased the severity of acid precipitation. Whatever acid precipitation used to happen before industrial revolution was buffered and managed well by the ecosystem.
It’s only after the industrial revolution and increased interventions by humans the ecosystem is not able to absorb or buffer the acidic gases present in excess in atmosphere. The cascading effect that these acidic precipitation has, down the line is causing alarming changes not only to our immediate surroundings but also to the future aspects.
The consequences of acid rain are both long term and short term.
- Irreversible damages to heritage monuments, buildings, strategic structures,
- Irreparable damages to water bodies, loss of aquatic life and in some cases total extinction,
- Loss of top soil due to change in pH and washing away of soluble salts,
- Loss of vegetation,
- Severe effects on animal lives,
- Change in food habit and forced migration.