Sulfur dioxide (SO2) is a chemical compound composed of sulfur and oxygen. SO2 emissions are from fossil fuel combustion at power plants (73%) and other industrial facilities (20%). When SO2 combines with other pollutants to generate sulphate particles, it increases the amount of delicate particulate matter (PM2.5) due to its unfavourable and inhumane effects from direct exposure. Power plants and commercial boilers are significant sources of SO2 emissions. This article will explain to you about Sulphur dioxide (SO2 ) which will be helpful in preparing the Environment subject for the UPSC Civil service exam.

What is Sulphur Dioxide?

• Sulphur dioxide (SO2) is a colourless, reactive gas produced by burning of sulphur-containing fuels such as coal and oil.
• SO2 air concentrations are highest in close proximity to major industrial sites that burn fuel.
• sulphur dioxide has been a significant cause of atmospheric corrosion in urban and industrial areas.

What are the Sources of sulphur dioxide?

• The burning of fossil fuels by power plants and other industrial facilities is the main contributor to SO2 in the atmosphere.
• Industrial procedures like mining for metal, volcanic eruptions, and other heavy machinery and vehicles that burn fuel with a high sulphur content are some of the smaller sources of SO2 emissions.

How does SO2 cause Air pollution?

• Air pollution is largely caused by SO2 emissions. Sulphur Oxides typically occur when there are high levels of SO2 in the air (SOx).
• Human health is impacted by both direct exposure to it and exposure to PM2.5 (fine particulate matter), which is created when SO2 combines with other air pollutants to form sulphate particles.
• The burning of fossil fuels in power plants and other industrial facilities is the main contributor to SO2 in the atmosphere.
• Other sources include industrial procedures like the extraction of metal from ore, natural sources like volcanoes, and heavy machinery like trains and ships that operate on gasoline with a high sulphide content.
• Particulate Matter can be created by SOx in response to various climatic conditions. Particulate Matter (PM) pollution is increased by these particles.
• Particulate matter may penetrate the lungs deeply, and too little of it might exacerbate existing health problems.
• With 91 percent of the population living in areas where open-air pollution exceeds WHO standards, air pollution is now a major concern for overall health (WHO). 4.2 million people pass away annually as a result.
• The consumption of petroleum derivatives in power plants and other contemporary offices is the best generator of SO2 in the atmosphere.
• Different sources include industrial operations like mining for metal, natural sources like volcanoes, railways, ships, heavy machinery, and vehicles that use gasoline with a high sulphur content.

How is SO2 measured in the Atmosphere?

• The SO2 is measured using a vacuum pump, the sample is sucked into the analyzer and sent through a scrubber to remove interfering gases such hydrocarbons before being passed through a filter to remove particles.
• After being cleaned, the sample enters a reaction chamber where it is exposed to ultraviolet (UV) radiation at a wavelength of 214 nm, which is produced by a zinc discharge lamp and a UV bandpass filter.
• UV rays with wavelengths between 200 and 240 nm are absorbed by sulphur dioxide. Following this absorption of UV light by the molecule, fluorescence (light-producing) photons at higher wavelengths (about 350 nm) are released.
• Using a photomultiplier (PM) tube, the fluorescence is measured perpendicular to the beam, and the signal is then translated into a concentration value.
• The amount of sulphur dioxide in the sample directly relates to the fluorescence that was detected.

What are the Impacts of SO2?

Health

• Breathing can become difficult and the human respiratory system can be damaged by brief exposures to SO2.
• Children in particular are sensitive to these effects of SO2, as are people with asthma.
• High SO2 airborne concentrations caused by SO2 emissions typically also result in the creation of additional sulphur oxides (SOx).
• Small particles can be created by the reaction of SOx with other atmospheric substances.
• Particulate matter (PM) pollution is a result of these particles. If there are enough little particles, they can enter the lungs profoundly and cause health issues.

Environment

• Gaseous SOx can injure trees and plants at high concentrations by destroying the foliage and slowing growth.
• Acid rain, which can affect delicate ecosystems, can be caused by SO2 and other sulphur oxides.
• As a result of atmospheric reactions, SO2 and other Sulphur Oxides can produce small particles that decrease visibility.
• Particle deposition can also discolour and harm stone and other materials, especially historically significant items like sculptures and monuments.

India - Sulphur Dioxide pollution

• According to a report by Greenpeace India and the Centre for Research on Energy and Clean Air, India's sulphur dioxide (SO2) emissions saw a substantial fall of about 6 percent in 2019 compared to 2018.
• Five of the top 10 SO2 emission hotspots from the coal/power generation business are located in India, according to the report.
• According to the NASA OMI (Ozone Monitoring Instrument) satellite, the major SO2 emission hotspots in India are Singrauli in Madhya Pradesh, Neyveli and Chennai in Tamil Nadu, Talcher and Jharsuguda in Odisha, Korba in Chhattisgarh, Kutch in Gujarat, Ramagundam in Telangana, and Chandrapur and Koradi in Maharashtra.
• Sulphur dioxide (SO2) emission caps for coal power plants were introduced in 2015 by the Ministry of Environment, Forests, and Climate Change (MoEF&CC).
• For eight pollutants (PM10, PM2.5, NO2, SO2, CO, O3, NH3, and Pb) for which short-term (up to 24-hours) National Ambient Air Quality Standards are prescribed, an air quality sub-index has been developed.
• SO2 emissions in India have increased at hotspots where they already exist, and new locations that produce emissions are popping up all over the place.
• The deadline for installing Flue-Gas Desulfurization (FGD) technology in power plants was changed by a Supreme Court judgement from 2017 to December 2019 in Delhi-NCR and until 2022 in other regions of the nation.
• Since it is unclear whether power plants would fulfil even the extended deadlines to comply with pollution limits, both in Delhi and across the country.
• Environmental experts have advocated for strong action against coal power plants.

SO2 Emission Across the World

• The countries with the highest concentrations of Sulphur Dioxide emissions are Serbia, Russia, South Africa, Iran, Saudi Arabia, India, Mexico, the United Arab Emirates, and Saudi Arabia.
• In India, Saudi Arabia, and Iran, air pollution emissions from factories and other businesses are still rising.
• Emissions are not now rising in Russia, South Africa, Mexico, or Turkey, but there hasn't been much progress made in reducing them either.
• China and the United States, two of the world's largest emitters, have reduced emissions significantly by transitioning to clean energy sources.
• China in particular has succeeded by significantly enhancing emission rules and sulphur dioxide control enforcement.
• Global Hotspots: The Norilsk smelting site in Russia continues to be the greatest source of human SO2 emissions worldwide. The fifth-ranked city is Singrauli in Madhya Pradesh.

Conclusion

Sulphur dioxide directly affects human health and causes a number of respiratory issues. Sulphur dioxide, like the majority of air pollutants, is more dangerous to vulnerable populations like the elderly, people with asthma, and small children. Sulphur dioxide can have a substantial influence on plants, surface waterways, and buildings by contributing to acid rain.

FAQs

MCQs

1. What is the main source of Sulphur Dioxide (SO2) emissions?

A) Volcanic eruptions
B) Industrial processes and burning of fossil fuels
C) Transportation emissions
D) Agricultural activities

2. How does SO2 contribute to air pollution?

A) By causing the formation of ozone
B) By forming fine particulate matter (PM2.5) and contributing to smog
C) By increasing the greenhouse effect
D) By reducing visibility in the atmosphere

3. Which of the following is a major consequence of SO2-induced acid rain?

A) Damage to ozone layer
B) Loss of biodiversity in aquatic and terrestrial ecosystems
C) Increase in crop yields
D) Improvement in soil fertility

4. What technology is commonly used to reduce SO2 emissions from industrial processes?

A) Carbon capture and storage (CCS)
B) Flue-gas desulfurization (FGD)
C) Electrostatic precipitation
D) Activated carbon adsorption

5. What health issue is commonly linked to SO2 exposure?

A) Skin rashes
B) Respiratory problems, especially in individuals with asthma
C) Increased risk of cancer
D) Liver damage

GS Mains Questions and Model Answers

Q1: Explain the environmental and health impacts of Sulphur Dioxide (SO2) pollution.

Answer: Sulphur Dioxide (SO2) is a significant air pollutant with detrimental effects on both the environment and human health. Environmentally, SO2 contributes to the formation of acid rain, which can damage soil, water bodies, and plant life, leading to the degradation of ecosystems. It also reacts with other atmospheric pollutants to form fine particulate matter (PM2.5), which further exacerbates air pollution. Health-wise, SO2 exposure can cause respiratory problems, including asthma and bronchitis, and worsen cardiovascular conditions. Long-term exposure can lead to reduced lung function and increase susceptibility to respiratory infections, especially in vulnerable groups such as children and the elderly.

Q2: Discuss the methods employed to control SO2 emissions and their effectiveness.

Answer: There are several methods to control SO2 emissions, primarily targeting industrial processes. Flue-gas desulfurization (FGD) is one of the most common technologies, which uses chemical processes to remove sulfur from exhaust gases before they are released into the atmosphere. This method has been highly effective in reducing SO2 emissions from power plants and industrial facilities. Additionally, switching to cleaner fuels such as natural gas and adopting renewable energy sources can significantly reduce SO2 emissions. The implementation of stricter emission standards and regulatory measures is also crucial in controlling SO2 levels and mitigating its environmental and health impacts.

Q3: Analyze the role of SO2 in climate change and the strategies to mitigate its impact.

Answer: SO2 plays a complex role in climate change. While it is a major air pollutant that contributes to acid rain and poor air quality, it also has a cooling effect on the climate. SO2 particles, when released into the atmosphere, reflect sunlight and have a temporary cooling effect. However, the negative environmental and health impacts far outweigh this cooling effect. To mitigate its impact, strategies include reducing the use of fossil fuels, adopting cleaner energy technologies, and using SO2 capture technologies like flue-gas desulfurization (FGD). International agreements such as the Paris Agreement also play a role in reducing emissions of harmful pollutants, including SO2.

Previous Year Questions on SO2

1. UPSC CSE Prelims 2017:

Question: Which of the following is a consequence of sulfur dioxide (SO2) pollution?

A) Global warming
B) Acid rain formation
C) Ozone depletion
D) Loss of biodiversity

Answer: (B)

Explanation: Sulfur dioxide (SO2) primarily contributes to the formation of acid rain, which harms the environment by acidifying soil and water bodies, thus negatively affecting plant life and aquatic organisms.

2. UPSC CSE Mains 2019 (GS Paper 3):

Question: Discuss the effects of SO2 on human health and the environment, and explain the methods to reduce its emissions.

Answer: SO2 pollution can cause severe respiratory issues, especially for vulnerable groups such as children and the elderly. It also contributes to environmental problems such as acid rain and the formation of particulate matter. To reduce its emissions, industries must adopt cleaner technologies like flue-gas desulfurization (FGD) and transition to renewable energy sources. Stricter regulations on industrial emissions and cleaner fuel options are also essential to control SO2 levels.