In simple words, it can be defined as; ” Rainwater with less than pH 5.6. ”It includes the precipitation of water droplets in the environment with the air particles having sulfuric or nitric acid which then deposits in the wet or dry form on the surface ground.
The main idea of this illusive destruction was given by John Evelyn in 17th century, when he observed the drastic effects on Arundel Marbles by this acidic deposition. In 1852, Robert Angus Smith reported the relationship between acid rain and pollution in the atmosphere found in Manchester, England. He was the first person who named this rain, acidic rain.
In the late 1960s, its phenomenon was under observation by various scientists among which Canadian Harold Harvey research a lake named, ‘Dead’ lake. In 1970s this rain was introduced to public by the newspaper, The New York Times. They reported that they saw a dramatic effect on Hubbard Brook Experimental Forest in New Hampshire.
As human innovation increases with time same as the drastic effects on the atmosphere were increasing which was resulting in a tremendous increase in the deposition of many atmospheric gases among which carbon dioxide, nitric, nitrous, and sulphuric acid gases are one them. These gases then started to reside in the atmosphere which then combined with the air particles like water droplets(raindrops). This resulted in the low pH of the rainwater which then started deposition on the lakes, mountains, and marbles all around. Like reported in low pH of rain which falls in Scandinavia.
Further elaboration of this effect was from the Hubbard Brook Valley in 1972 when many scientists along with Gene Likens discovered white mountains in New Hampshire covered with acidic rain whose pH when analyzed was 4.03. Then he started searching about the main reason for this deposition when he found that there was a chemical reaction between acid rain and aluminum in the air covered by increasing level of the soil weathering. This then increased in the community dominants and reducing the level of the species variation diversity and food chains leading to the complexity of the food web.
To let this pollution overcome, in 1991, NAPAP (National Acid Precipitation Assessment Program) was the first who reported the link between the U.S and Canada when they showed how tremendously this acid rain from the Clean Air Act of 1970 and its foundations in 1990. The resulting reports were given in the form of the graphical representation as follows;
• First emission was reported in 1995, mainly by the regulation of coal-fired power plant emissions from SO2 decline between 1990 and 2017.
• By the control of the automobile gases in the environment there was a decline in the SOx gases from 1980.
• There was a tremendous increase in the area having higher livestock and agriculture production toxified by the ammonia (NH3) and ammonium deposition.
Measurement of Acid Rain
The acidity and basicity of any matter are measured with the help of a scale, named as pH scale. The pH of acid rain mainly resides between 4.2 to 4.4. The extraction of results of the wet deposition is done from more than 90 locations by NADP (National Atmospheric Deposition Program’s) and NTN (National Trends Network). While for the dry deposition it was a difficult task being done by CASTNET (Clean Air Status and Trends Network).
The LTM (Long-Term Monitoring) reported valuable information on how water bodies respond towards the acid deposition over 280 sites as the acid deposition is washed into lakes and streams.
Types of acid rain
There are two main forms of acid rain resulting from the deposition of this kind of droplet.
These are as follows;
1. Wet Deposition
2. Dry Deposition
1 Wet Deposition:
This type of deposition includes the form in which there is mixing of the rain droplets with the toxic particles which sometimes is also named as the Acid Rain on behalf of the mixing with moisture. This includes the following features;
i. It affects living matter like animals and plants as the deposition is on the ground level on which these are residing.
ii. It is the mixture of sulfuric and nitric acids found in the environment mixed with rain, snow, hail, or fog.
iii. It is the result of the rainfall that is usually in the form of gases.
2 Dry deposition:
This is the result of the simple deposition of the dry particles from the atmosphere to the ground without mixing with the moisture and is deposited directly on the ground. As
i. It results from the dust foil.
ii. It is empowered to the ecosystem from the industrial area and the eroded mining nutrients deposition.