Nitrogen oxide is the other primarily source that is responsible for the formation of acid rain nitrogen oxides is a compound that has an amount of oxygen in it The only oxides of nitrogen are nitrogen monoxide and nitrogen dioxide. These gases are produced by firing processes at very high temperatures (vehicle) and chemical industries. There are natural processes such as forest fires, volcanoes and bacterial action in soil that also emit nitrogen oxides. Transportation and industrial combustion also contribute to the emissions of nitrogen oxides.
The acidity of acid rain does not only depend on the release levels of these gases but also on the chemical combination sulphur dioxide and nitrogen oxides interrelate in the atmosphere. Both gases undergo a few chemical reactions before they become the acids present in acid rain. The two main phases are the gas phase and the aqueous phase.
As far as sulphur dioxide is concerned there is a range of possible reactions that may lead to the oxidation of the gas in the atmosphere each having a different degree of success. One option is the photo oxidation of the gas by ultraviolet light. This reaction has been found to be an unimportant supplier to the creation of sulphuric acid.
Another route that is more common is the one where sulphur dioxide is oxidized to form a sulphite ion.
SO2 (g) + o2 (g) à SO32-
After this the sulphite ion forms sulphuric acid when it comes into contact with the moisture in the atmosphere.
SO32- +H2O (l)à H2SO4 (aq)
This reaction takes place quickly therefore the construction sulphur dioxide in the atmosphere is thought to lead to this kind of oxidation and form sulphuric acid. The photo oxidation method is much slower due to the absence of a catalyst.
A third reaction for sulphur dioxide to become sulphuric acid is by the oxidation by ozone. All the reactions mentioned to this point are gas state reactions. In the aqueous phase sulphur dioxide exists as three kinds:
[S(IV)]à[SO2(aq)] + [HSO32]+[SO32]
There is a dissociation that consists of two parts:
SO2 (aq)à H++HSO3-
HSO3- (aq)àH+ + SO32-
The oxidation of aqueous sulphur dioxide depends on catalysts like iron and manganese.
The oxidation of sulphur dioxide is most widespread in clouds and particularly in greatly polluted air where there are abundant amounts of ammonia and ozone, which act as catalysts in the formation of sulphuric acid from sulphur dioxide. However, not all the sulphur dioxide becomes sulphuric acid, as a lot of it floats up into the atmosphere and is transported to other areas and returns to earth unchanged.
Nitrogen oxides like sulphur dioxide rise into the atmosphere and are oxidized in clouds to form nitric acid. Very polluted clouds where traces of manganese, hydrogen peroxide and iron are present provide catalysts for theses reactions. Nitrogen oxides are mainly emitted into the atmosphere by vehicle exhausts. They react with water to form nitric acid in the atmosphere.
NO2 (g)+H2O (l)àHNO3 (aq)+HNO2(aq) [gas phase]
In the aqueous phase there are three equilibrium that have to be considered for the oxidation of nitrogen oxide:
* 2NO2(g)+H2O(l) 2H++NO3- +NO2-
* NO (g)+NO2(g)+H2O (l) 2H+ +2NO2-
* 3NO2(g)+H2O(l) 2H+ +2NO3-+2NO(g)
The limited pressures of nitrogen oxides present in the low atmosphere, and the low solubility of nitrogen oxides limit the above reactions. There is an increase in the rate of the reactions only with the use of metal catalysts like in the case of the aqueous oxidation of sulphur dioxide.
This is a basic diagram showing how acid rain works
Task 3 - What are the effects of acid rain?
Scientists have noticed that over the years some forests seem to be growing more and more slowly for no obvious reason. After the collection of information on the chemistry and the biology of the forests it has been proved that this is due to acid rain.
When acid rain falls, the acidic rainwater dissolves the nutrients and helpful materials from the soil. These minerals are then washed away before trees other plants can use them to grow. The acid rain also helps release toxic substances such as aluminium into the soil. This is o due to the fact that metals like this are bound to the soil under normal conditions, but the added dissolving act of hydrogen ions causes rocks and small bound soil particles to break down. When acid precipitation is regular leaves are likely to lose their waxy protective coat. This loss makes the plant open to any disease. When the leaves are damaged the plant cannot produce adequate food energy for it to survive. When the plant is weak it is defenceless to disease, insects that may kill it.
Acid rain also affects aquatic organisms. It enters lakes in several ways but the most common route is when it is drained through sewage systems that lead to lakes. The euphoric acid present in acid rain interferes with the fish’s’ ability to take in oxygen, salts and nutrients. Acid molecules cause the formation of mucus to form in their gills not allowing them to absorb oxygen well. Additionally the low pH level does not allow the calcium levels of the fish to be maintained causing the eggs during reproduction to be weak and brittle. Sometimes when acid rain runs off the land it carries some fertilizers along into the lakes .The fertilizers encourage the growth of sea plants causing eutrophication.
Apart from natural eco systems, acid rain also affects man-made materials and buildings. Limestone, marble and sandstone are all very easily dissolved by acid rain. Textiles, paints, metals and ceramics can readily be decayed. Man-made materials are slowly depreciated with normal rainfall but acid rain speeds up this process.
However, most importantly acid rain can affect the health of human beings. It harms us via the atmosphere or through the soil from where we get our food. Acid rain causes the release of toxic metals that may be absorbed by drinking water, crops or animals that may later consumed by humans. These could cause nerve damage to children or acute brain damage or even death.
Acid precipitation is very harmful to the respiratory system. Sulphur dioxide and nitrogen oxide secretion may lead to dry coughs, asthma, headaches, eye, and nose and throat irritation. It has the ability of making breathing very difficult and may give rise to diseases, which could possibly lead to death.
Task 4 - How acid rain can be prevented
Since we know the effects of acid rain now the only thing that matters is how to enforce solutions to stop acid rain, the causes of this situation must be made aware of to the people all around the world and they should also be educated about it thoroughly . The ways to stop acid rain can only be successful through mutual cooperation. Given below are FIVE different acid rain solutions, which can reduce the occurrence of acid rain, if strictly followed by a large number of people.
- As quick as industrial power plants are worried, the most excellent solution is to connect devices known as 'scrubbers' in the chimneys of these plants. These scrubbers reduce the amount of sulfur produced in the smoke by 90 - 95%.
- Vehicles and cars must be set required to fulfill with very tight efficient emission standards. Fitting catalytic converters into the exhaust pipes of vehicles also reduces the quantity of sulfur dioxide created by the vehicle.
This is a basic picture showing a catalytic converter
- We can make many changes on a personal level as well, in order to fight acid rain. We should limit the use of our cars and vehicles and use other modes of transportation on a more everyday basis. We should also remember to turn off all our lights and electrical devices in case we are not using them. £140 million a year is wasted through leaving lights on in unused rooms, so always turn off the lights when you leave a room. You can save up to 6 liters per minute by turning off the tap when brushing our teeth shaving and when washing up. And we should replace dripping taps that can save up to 15 liters of water a day, or almost 5,500 liters per year. If you're on a water meter, that could save you over £18 a year.
- For industrial power plants, there are many more acid rain solutions that must be enforced, as they are clearly the biggest contributors to the formation of acidified water droplets in the atmosphere. Industries must regularly inspect and clean all their emission equipment and chimneys and pipes.
- All these acid rain solutions are pointless unless people are notified and educated about the effects and harms of acid rain. An extensive and nationwide effort must be made to make people aware. Only after that is done will all the acid rain solutions actually make a difference
Conclusion
Overall, acid rain is a big problem that should not know to every one because of its major effects. This occurrence ruins anything it comes into contact with. By affecting the environment acid rain affects humans on the long run as well. What we can do, to reduce the emission of gases that cause acid rain is to reduce the use of fossil fuels. Walking and public transportation can reduce tons of nitrogen oxide emissions. The use of less energy is beneficial to the atmosphere as energy comes from fossil fuels, which may lead to acid rain. But on the other hand I think all the solutions should be followed thoroughly because so then the occurrence of acid rain can decrease dramatically.
Reference
The picture of the ph scale
From-(http://www.epa.gov/acidrain/education/site_students/images/phscale.gif)
The picture of the damaged statue
From ()
The picture of fish affected by acid rain
From (http://economicobjectorvism.wordpress.com/2007/07/19/china-wakes-up-to-the-dangers-of-pollution/)
The picture of damaged trees
From (http://www.tropical-rainforest-animals.com/air-pollution-effects.html)
The picture of acid rain diagram
From ()
The picture of catalytic converter
From ()
MOHAMMED ABDUL KALIK SHAHEEN
