Download air pollution due to photochemical smog

AIR POLLUTION DUE TO PHOTOCHEMICAL SMOG
Explain in brief Air pollution due to photochemical smog. (8)
It is chemical reaction of sunlight. Nitrogen oxides and volatile compounds in the
atmosphere which leaves airborne particles and ground level ozone. This noxious
mixture of air pollutants can include the following.
Aldehy des, Nitrogen Oxides, peroxyacyl nitrates Tropospheric Ozone, Volatile
organic Compounds. In the presence of certain hydrocarbons, other reactions take
place. Some of the atomic Oxygen, Ozone, and nitric Oxide react with hydrocarbons
to form a variety of products and intermediates with which even further reaction can
probably take place. Some of the Products formed are aldehydes like formaldehyde
and acrolein, peroxides, and proxy acetyl nitrate (PAN).
Parameters1) Sunlight,
2) Nitrogen oxide,
3) Volatile components in atmosphere.
4) Nox,
5) Tropospheric zone.
6) Vehicle smoke,
7) Industrial smoke,
If Nitric Oxide is also present in the air, following reaction can take place
NO + O3
NO2 + O2
(12.5)
If Ozone is present in excess, then
2NO2 + O3
N2O5 + O2
(12.6)
In presence of water Vapor, the following reaction can take place
N2O5 + H2O
2 HNO3
(12.7)
Thus nitric acid may be formed.
12.2.2 Sulphur Dioxide Photochemical Reaction
Ozone may be formed in the atmosphere as a byproduct during the
photochemical oxidation of sulphur dioxide to sulphuric acid. The reaction takes
place as follows :
SO2 + hv
SO2
(12.8)
SO2 + O2
SO4
(12.9)
SO4 + O2
SO3 + O3
(12.10)
SO3 + H2O
H2SO4
(12.11)
The quantum efficiency for this process is low.
12.2.3 Aldehydes Photochemical Reactions
The photochemical Oxidation of aldehydes can be represented as follows
R CHO + hv
R CHO*
(12.12)
R CHO* + O2
R CO3H
(12.13)
R CO3H + O2
R COOH + O3
(12.14)
The primary photochemical decomposition of aldehydes produces organic free
radicals. For example, acetaldehyde decomposes into methyl and formal radicals.
It present in all modern cities, but it is more common in cities, with sunny,
warm, dry climates and a large number of motor vehicles. Because it travels with the
wind, it can affect sparsely populated areas as well.
Air pollution is occurs mainly caused by nitrogen oxides come from the
engines of cars and trucks. The pollutants released through acidity in this situation
are known as primary pollutants”, and they include sulfur dioxide, carbon monoxide,
and other volatile organic compounds. When these compounds in tract with the sun,
they form ‘Secondary pollutants’ like Ozone and additional hydrocarbons.
Areas Affected:London, Atlanta, New York, Delhi etc.
What are the Health effects of Air pollution due photochemical
smog. -
4
1)Smog is serious problem in many cities and continues to harm human health.
2)Ground-level Ozone, Sulfur Dioxide, Nitrogen Oxide and Carbon Monoxide are
especially harmful for senior citizens, children, and people with heart and lung
conditions such as emphysema, bronchitis, it can inflame breathing passages,
decrease the lungs working capacity cause shortness breath, pain when in-haling
deeply, wheezing and coughing.
3) It can cause eye and nose irritation and it dries out the protective members of the
nose and throat and interferes with the body’s ability to infection, increasing
susceptibility to illness.