Notes

pg1atmospheric pollution:

As different gases are released into the air through man-made or natural sources, they sometimes are not supposed to be in the open atmosphere, or too much or too little of it enters the atmosphere. This either poisons the air, causes too much of something or destroys something which was important for the existence of living beings. Such scenarios lead to pollution.

Polluting something, means dirtying it or organizing it in such a way that it hurts its environment. The type of pollution this project is about to talk about, is atmospheric pollution, which is also known as air pollution. The medium which pollutes the air or anything else, is known as a pollutant.
some pollutants which pollute the air are:

-particulates such as mist, smoke, fumes, dust
-oxides of sulphur such as SO² and SO³
-oxides of nitrogen such as NO, NO², N²O
-oxides of carbon such as CO and CO²
-Hydrogen sulphide (H²S)

these pollutants, mixing with the air causes phenomenon's which end up ruining the environment. Some of these phenomenon, the phenomenons which will be discussed in this project, are: acid rain, greenhouse gas effects, global warming and ozone layer depletion. pg1



pg2acid rain:

Acid rain is the result of the oxides of sulphur and nitrogen when, as pollutants, pollute the atmosphere. These oxides, mainly including SO² and NO², in the atmosphere, react with water vapour in the presence of sunlight and form sulphuric acid[H²SO⁴] and nitric acid[HNO³] mists. These mists remain as vapours at high temperatures and condenses at low temperatures. The acids fall down on the earth in a form resulting in acid rain.

Deposits are the form in which this acid reaches earth. Two forms of deposition for acid rain are: 1> wet deposits- such as rain, snow, fog or dew containing sulphates and nitrates. 2> dry deposits- such as particles containing sulphates and nitrates.

Causes:
As discussed before, acid rain is formed when the water vapour present in the atmosphere reacts with SO² and NO², but how do large amounts of SO² and NO² enter the atmosphere?

1>Burning of fossil fuels: Fossil fuels such as coal, petroleum and natural gas, are derived from the remain of plants and animals. Burning these fuels leads to formation of SO² due to the sulphur impurities in them. Electrical power stations burn coal for their uses, hence releasing large amounts of SO² gas.
2>Bacterial decomposition of organic matter releases H²S which is oxidized into water and SO².
3>Smelting plants produce SO² when metallic sulphides are roasted in air. Eg: 2ZnS + 3O² -> 2ZnO + 2SO²
4>Internal combustion engines: it is an engine in which combustion of a fossil fuel occurs with an oxidizer{air} in a combustion chamber. The air drawn from the atmosphere contains about 80% nitrogen. The nitrogen combines with oxygen at high temperatures producing oxides of nitrogen. Thus exhuast gases of all internal combustion engines release oxides of nitrogen.pg2




pg3composition and formation of acid rain:
Compared to normal rain water, acid rain, as said in its name, has much more acidity. In normal rain water which is formed in unpolluted air, appears to range 5 to 6 in a pH scale, which is close to the neutral range of 7. But acid rain measures from 5.6 to 3.5 which can be dangerous to the environment. The reason why normal rain water is slightly acidic is because of the CO^2 present in traces in the air dissolves in the rain water forming wear carbonic acid.

Acid rain is abundantly composed of sulphuric acid and nitric acid. Other than these, it also includes sulphurous and nitrous acids. These acids end up in the atmosphere when gases[SO^2 and NO^2] are released in the air. The sources of these gases have been discussed, but how are they formed?

Formation of sulphuric acid and sulphurous acid

scenario: Electric power stations burn coal[fossil fuel] for power generation.
sulphur impurities from the coal reacts with O^2 and form sulphur dioxide[SO^2]. Sulphur dioxide reacts with water vapour to form sulphurous acid. SO^2 can also be oxidized to sulphur trioxide[SO^3] and then react with water vapour to form sulphuric acid[H^2SO^4]

Formation of nitric acid and nitrous acid

Scenario: High temperatures in furnaces and internal combustion engines
Nitrogen in air at temperatures above 1300degrees^C combines with oxygen to form NO. Nitric oxide is oxidized to form nitrogen dioxide[NO^2]. Nitrogen dioxide reacts with water vapour to form nitrous acid[HNO^2] and nitric acid[HNO^3].
Hence, the acidity in rain is due to the reaction of oxides of nitrogen and oxides of sulphur with water vapour forming dilute acids.pg3


pg4impact:(later)
pg4

pg5Greenhouse effect and global warming:

Green house effect is the warming up of the earth's surface due to the concentration or blanketing effect of the greenhouse gases. Greenhouse gases are those gases that contribute effectively in retaining heat in the atmosphere. Major greenhouse gases include carbon dioxide, methane, water vapour, oxides of nitrogen, chlorofluorocarbons. The greenhouse effect leads to global warming, having a global impact where the earths surface heats up more than its previous temperatures.

Contribution
tablepg5

pg6sources:
yaadadadadadada(tb)
pg6

pg7impact + reduction(tb)pg7

pg8reductionpg8

pg9 ozone depletion:

Ozone gas[O^3] is a natural constituent of the atmosphere. It is a bluish, ezplosive gas with a pronounced odour. The ozone gas makes up the ozone layer, present within the known boundary of the stratosphere, roughly 20-30 kms above the earth. The ozone layer protects life on earth by blocking and absorbing 97-99% of the sun's high frequency U.V. light.

The ozone layer was discovered in 1913 by A pair of French scientists named Charles Fabry and Henri Buisson. Using an interferometer to make the most accurate measurements ever of ozone in the atmosphere. Later on, G. M. B. Dobson, a researcher at the University of Oxford, made significant contributions to the study of the ozone layer. In the 1930s, Dobson built the first Dobson spectrophotometer, which allowed for reliable measurements of the ozone layer. The Dobson unit (DU) is the unit used to measure the amount of ozone in the air above a specific point on Earth. The DU is named after Dobson. The Dobson spectrophotometer was used to discover the Antarctic ozone hole in 1984.pg9

pg10formation of ozone layer:
t y p e o n e .
In the stratosphere, highly energetic ultraviolet radiations from the sun breaks an oxygen molecule[O^2] into two oxygen atoms. This process is called photodissociation or photolysis. These O atoms are highly reactive and reacts with another oxygen molecule to form ozone[O^3].
t y p e t w o .
In unpolluted air, containing minimum chemical compounds, an unstable ozone molecule may split into molecular oxygen[O^2] and an atom of atomic oxygen[O] due to being in the presence of solar radiations. The atomic oxygen then combines