Smog is characterized by a thick and hazy air pollution mixture that is often observed in densely populated urban areas and industrial regions. Smog is a combination of smoke and fog. In this article, you will learn about definition, types, and how smog formation takes place, etc.
This article will provide key insights for GS Paper-3 Environment & Ecology of UPSC IAS Exam.
Table of Contents
- What is Smog?
- Different types of smog
- Smog formation takes place due to chemicals
- How is smog formed?
- Smog effects
- Government initiatives to control smog
- How can photochemical smog be controlled?
- Conclusion
- Frequently Asked Questions
What is Smog?
- Smog refers to a dirty brown haze created due to air pollution, majorly in cities.
- Causes of smog: Smog is a mixture of smoke and fog and hence its name.
- Smog was prevalent in urban areas during the early 20th century.
- Difference between fog and smog: fog is harmless water droplets present in the lower troposphere, whereas smog is an air pollutant that combines fog and smoke.
Different types of smog:
- Photochemical smog: are smog that are formed when sunlight interacts with certain pollutantatmosphericgases in order to form smog.
- The majority of smog is caused due to photochemical processes.
- Photochemical smog is called ‘ground level ozone’.
- Photochemical smog is also known as Los Angeles smog as photochemical smog was first observed in Los Angeles.
- Photochemical smog does not require either smoke or fog to occur.
- Components of photochemical smog: photochemical smog always contains- nitrogen dioxide (NO2), ozone (O3), peroxyacetyl nitrate (PAN), and compounds that contains aldehydes.
- The major photochemical smog is formed by Chlorofluorocarbons.
- Majority of photochemical smog is formed in dry and sunny climate.
- London smog: is formed due to high concentration of sulphur oxides in the air mainly produced through burning of fossil fuels like Coal.
- It is also known as the Classical smog.
- London smog is found in winter during morning time.
- London smog is also known as Sulfurous smog.
- Delhi smog in winter is caused by this type of smog.
Smog formation takes place due to chemicals:
- Tropospheric ozone (O3): created by chemical reactions between oxides of nitrogen oxides (NOx) and Volatile Organic Compound (VOC).
- Primary particulate matter such as pollen and dust
- Secondaryparticulate matter such as sulphur oxides, VOC, NOx and ammonia gas.
- Nitrogen oxides sources: vehicle exhausts, coal factories, and industrial facilities.
- VOC sources: gasoline, aerosol sprays, paints and household cleaners.
- Ammonia gas sources: is a by-product of agriculture majorly fertilizers and livestock waste management.
How is smog formed?
Nitrogen dioxide (NO2) from pollutants is broken down by sunlight to form nitric oxide (NO) and an oxygen radical (O):
NO2 + sunlight NO + O
Oxygen radicals then reacts with atmospheric oxygen (O2) to form tropospheric ozone (O3):
O + O2 O3
Ozone reacts with nitric oxide to produce nitrogen dioxide and oxygen:
O3 + NO NO2 + O2
The nitrogen dioxide then reacts with various hydrocarbons (compounds made from carbon, hydrogen) and other substances:
NO2 + hydrocarbons Harmful products such as peroxyacetyl nitrate (PAN)
Smog effects:
- Photochemical smog effects: reduces visibility leading to major accidents including irritation in eyes.
- This adversely affects transportation sector of the economy.
- Diseases caused by smog includes asthma, coughing, fatigue, shortness of breath.
- Surface-level ozone layer concentrations are considered unhealthy if they exceed 70 parts per billion for 8 hours or longer.
- It erodes away the surrounding buildings due to its chemical reactions with its material, including monuments of national importance.
- Thus, it affects tourism sector and national heritage and culture adversely.
- It inhibits the plant growth by reducing the amount of photoperiod required by it for photosynthesis.
- Result: it affects the overall food production of the country and affects agriculture sector.
Government initiatives to control smog:
- The National Clean Air Programme (NCAP): It is a Central Sector Scheme to achieve 20% to 30 % reduction in PM10 and PM2.5concentrations by 2024 where 2017 will be the base year.
- It is a programme under the “Control of Pollution” scheme.
- Comprehensive Action Plan (CAP): aims to mitigate and control air pollution in Delhi and National Capital Region (NCR) by defining timelines and implementing agencies.
- Graded Response Action Plan (GRAP): identifies measures and implementing agencies for response to 4 AQI categories in Delhi and NCR.
- SAMEER app: It provides vital information of air quality and provisions to register complaints against air polluting activities.
How can photochemical smog be controlled?
- Smog Tower: Theyare air purifiers that works on the principle of air ionisation technology to remove PM2.5 particles.
- Example: Smog tower Delhi
- Catalytic reduction: It is method of lowering the levels of nitrogen oxides.
- Renewable sources: Such as electric vehicles will help reduction on hydrocarbon-based fuel that are heavily responsible for London smog.
- Stubble burning: As it is a major source of air pollution in northern India during winter season, convert stubbleinto manure can help reduce such air pollution.
- Anti-smog gun: It is a device that sprays finer water droplets into the atmosphere which then absorbs the smallestdust and other particulate matter of range PM2.5 and PM10.
- Example: It is used in Delhi during winter season.
- Scrubbers: Using scrubbers in industry that absorbs major pollutants like sulphur dioxides or hydrogen sulphide etc.
- Low-Emitting Stoves: They are produced by equipping Biomass stoves with insulated combustion chambers, which burns off unused fuel and removes out the remaining pollutants.
Conclusion
As the urban cities of India are amongst the most populated in the world and agriculture being the highest employing sector, it becomes important to take relevant measures in reducing smog as envisaged by the Article 21 of the constitution (right to life and livelihood). The government should reduce polluting industries in majorly polluted areas with proper compensation to such industries in order to achieve its Sustainable Development Goal (SDG) 11. SDG 11 aims to renew and plan cities in a way that offers opportunities for all, with access to basic services while reducing resource use and environmental impact.
| Other Articles in Environment & Disaster Management | |
| Central Pollution Control Board (CPCB) | National Green Tribunal |
| Carbon Foot Print | Black Carbon |
| World Meteorological Organization | Kyoto protocol |
FAQs (Frequently Asked Questions)
What is London smog?
It is another name for sulfurous smog which is formed due to high concentration of sulphur oxides in the air.
Why did the great smog of London occurred?
The great smog of London occurred in 1952 due to cold weather, high-pressure weather system and calm winds that led to the build-up of air pollutants, mainly sourcing from coal usage. This resulted in the formation of a dense smog layer that covered the city.
Which disaster is related to smog?
The Great London Smog 1952 and Donora Air Pollution Disaster of 1948 are disasters related to smog.
What is photochemical smog?
The photochemical smog is a smog that forms when sunlight interacts with certain pollutant atmospheric gases in order to form smog.
What does photochemical smog consists of?
Thephotochemical smog consists of nitrogen dioxide (NO2), ozone (O3), peroxyacetyl nitrate (PAN), and compounds that contains aldehydes.
How is smog produced?
The smogis produced when the pollutants from industries such as coal industries (major source of sulphur-based smog) reacts with the fog present in the atmosphere.