Sulphur Dioxide (SO2) Gas and its impact on the Environment

Sulphur Dioxide (SO2) gas and its impact on the Environment

What is Sulphur Dioxide (SO2)?

• SO2 is a toxic gas. Naturally. It is released by volcanic activity.
• Other sources include coal-fired power stations, Diesel vehicles, oil refineries, and shipping etc.
• It is produced as a by-product of copper extraction and the burning of fuels contaminated with sulphur compounds.
• SO2 has a pungent smell and is responsible for the smell of burnet matches.
• In the atmosphere, it is found in traces of about 1ppm. SO2 is a potent air pollutant.
• Sulphur dioxide (SO2) reacts with water to form sulphuric acid (H2SO4), resulting in rainfall.
• SO2 condenses from clouds and is a key component of chemical reactions in the Earth’s atmosphere. It also contributes to global warming.

About the La Soufriere volcanic eruption

• La Soufrière volcano on St Vincent Island (in the West Indies) started erupting on April 9, 2021 (after spewing out lava into a dome and threatening to erupt since December 2020). 
• La Soufrière volcano had erupted in 1979, the last time.

• Ash and gas hang over the Caribbean island of St. Vincent. 
• The volcanic eruption has left the entire population of the main island without clean water and electricity.

Note: Of the 45 currently erupting volcanoes on Earth, La Soufriere is among those that worry volcanologists the most. Among the 45, some of the active volcanoes in and around India are Barren Island, India, and many in Indonesia, including Raung, Merapi, Lewotolok, Sinabung, Karangetang, Semeru, etc.

• As per the Multi-Angle Imaging SpectroRadiometer instrument on NASA’s Terra satellite, the volcanic eruptions on April 10 were energetic enough for the plumes to be recorded at the height of 20 km above the Earth’s surface.
• Scientists have found evidence for the entry of sulphate aerosol particles (precursors for sulphuric acid) in the stratosphere (the second layer of the Earth’s atmosphere).

Impact of So2 reaching the stratosphere

• The SO2 emissions, when they reach the stratosphere, can have a cooling effect on global temperatures. 
• The most significant climate impacts from volcanic injections into the stratosphere come from converting sulphur dioxide (SO2) to sulphuric acid (H2SO4), which condenses rapidly in the stratosphere to form fine sulphate aerosols.
• The aerosols increase the reflection of radiation from the Sun back into space. This leads to cooling the Earth’s lower atmosphere or troposphere.
• To have measurable climate impacts, a volcano needs to inject at least 5 teragrams of SO2 into the stratosphere.
• Around 0.4-0.6 teragram of SO2 were released into the upper atmosphere in the La Soufrière volcanic eruption.
• Note: This is the highest-ever recorded after satellites started observing the Earth’s atmosphere in the mid-20th century. 
• The volcanic “plumes” can cause air quality and aviation hazards. 

Note: Some of the bigger eruptions recorded during the past century have caused a decrease in temperature of 0.27 degree Celsius or more on the Earth’s surface for up to three years.

Other harmful effects of SO2 on the environment

• Gaseous SO2, at high concentrations, can harm trees and plants by damaging foliage and decreasing growth. 
• SO2 and other sulphur oxides’ presence (more than 1 ppm) in the atmosphere contribute to acid rain, which can harm sensitive ecosystems. 

Applications of Sulphur dioxide (SO2)

• SO2 is widely used in the food and drinks industries as it acts as a preservative and antioxidant in trace quantities. 
• These are predominantly dried fruits and vegetables, alcoholic beverages and soft drinks. 

Adverse effects of SO2 on human health

• Short-term exposures to sulphur dioxide (SO2) can harm the human respiratory system and make breathing difficult. 
• Note: People with asthma, particularly children, are sensitive to these effects of SO2.
• Some of the symptoms include shortness of breath, wheezing, and coughing. 

• SO₂ emissions that lead to high concentrations of SO₂ in the air generally also lead to the formation of other sulphur oxides (SO_x). 
• SO_x can react with other compounds in the atmosphere to form small particles.
• These particles contribute to particulate matter (PM) pollution and the small particles sometimes penetrate deeply into the lungs and in sufficient quantity can contribute to health problems.

How does the Indian Govt tackle air pollution?

Govt has two ways to control the outcome of any situation:

1. By giving incentive: Govt uses this method to encourage certain things
2. By putting fines and penalties: Govt uses this method to discourage certain activities.

Similarly, to control air pollution, recently the govt of India has allocated Rs. 2.217 crores. Although using the money has not been defined and shared by the govt, the broader understanding leads to knowing that the govt mainly uses four types of policies.

1. Adds a tax to raise the price of any commodity or activity to discourage more people from buying or doing that.
2. It gives a subsidy to the alternative activity or product, which the govt thinks is the second-best option.
3. Bans certain products or activities that can increase pollutants.
4. Govt introduces permits so that it can regulate and keep track.