Content Number: 09
Author Name: Attia Khan
Author I’d: SBPWNC – A09
Educational Institution: Govt. Post Graduate Islamia College, Gujranwala, Pakistan
Content Title: Photochemical Smog; Major Environmental Issue
Introduction:
God has created the universe in a balanced way. Atmosphere was consisted of about 0.03 percent carbon dioxide but uncontrolled increase in population and human activities have disrupted this balance. Unbalanced amount of gases in atmosphere leads to many problems. One of these is photochemical smog.
smog = smoke + fog
It is a type of pollution produced as a result of chemical reaction VOC’s, nitrogen oxides, sunlight. It reduces visibility. Smog is basically of two types:
- Classical smog (reducing in nature)
- Photochemical smog(oxidizing in nature)
In this article we will discuss photochemical smog. Photochemical smog is also called as Los Angeles smog because it was discovered in 1950 in city of Los Angeles in America and summer smog because it requires sunlight that is most available in summer. It is very prominent in morning as the number of vehicles emitting pollutants is more.
Causes:
Photochemical smog is caused by tropospheric ozone. It is a secondary pollutant.It does not occur in atmosphere directly however two primary pollutants are responsible for for tropospheric ozone :
1. VOC’s
- Nitrogen oxide
VOC’s are carbon compounds which can easily be converted into gas as they have low boiling point . Both of these are produced from household, commercial, industrial, agriculture and energy production sites.
Major reactions involved in the formation of photochemical smog:
- First NO2 will breakdown into NO and O in the presence of sunlight
NO2+sunlight➡NO+O
2. This Oxygen atom then reacts with oxygen molecule to give ozone
O2 +O ➡ O3
- Now O3 and NO will react with each other to give oxygen molecule and nitrogen dioxide.
NO+O3➡NO2+O2
This has shown that what is used is returned back to atmosphere so it is in the form of cycle and it maintains ozone balance but in the presence of VOC NO will react with VOC rather than ozone.This will stop the reaction responsible for destruction of ozone formed and this will increase the concentration of ozone.
Reaction of nitrogen oxides with VOC will produce
- PAN
- Aldehydes
- Hydrocarbon free radicals
All of these pollutants inturn leads to photochemical smog .
Factors Affecting Photochemical Smog:
- Topography: an area having high mountains it would become difficult for smog to escape .It causes persistent smog
- Temperature inversion: If air on upper atmosphere is hot than lower region this will also cause prolonged photochemical smog.
Hazards:
- It causes respiratory disorders.i-e coughing, difficulty in breathing, chronic bronchitis, asthma, inflammation of airways.
- It also causes severe eye irritation.
- It also effects plants by reducing their growth as well as photosynthesis.
Solution
- Platinum and rhodium catalytic converters can covert dangerous gases CO and NO into less effective pollutants.
- Public transportation can also be helpful
- Usage of good quality fuel
- Create engine designs which releases less pollution.
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I’m not a chemist but Nitrogen dioxide (NO2) is not a volatile organic compound (VOC) (reference to Section 1.0, while only one section is mentioned in this post, where are other section numbers??).
Nitrogen dioxide (NO2) is a nitrogen oxide (NOx), which is a different class of air pollutants. NOx includes nitrogen oxides such as nitrogen dioxide (NO2), nitric oxide (NO), and nitrogen monoxide (N2O).
Volatile organic compounds (VOCs), on the other hand, are organic chemicals that have a high vapor pressure at ordinary room temperature.
Nitrogen dioxide (NO2) is an air pollutant, but it is not classified as a volatile organic compound (VOC).