SO2 | Sulphur Dioxide | Sources and health impacts| OIZOM Academy
Channel: Oizom
Date: 2021-01-06

SO2 monitoring is an efficient way to detect and reduce exposure to sulfur oxides which further benefits in reducing the formation of particulate sulfur pollutants like fine sulfate particles, acid rain, and smog.  This article covers information on sulfur oxides, its sources, permissible levels in the ambient air, health and environmental impact, possible corrective measures, need for sulfur dioxide monitors as well as different methods of SO2 monitoring.

Sulphur oxides in the Atmosphere
SOx is naturally present in the atmosphere at very low concentrations. About 99% of SO2 is released into the atmosphere through human activities. High levels of SO2 are often found at industrial sites or in densely populated urban areas. The lifetime of SO2 in the atmosphere is about a few days and is removed by reacting with various other compounds.

Sources of SO2
Sulfur oxides are released into the atmosphere naturally from volcanic eruptions. SOx, especially SO2, are emitted by the burning of fossil fuels such as coal, oil, and diesel or any other materials that contain sulfur.  Emissions that lead to high concentrations of SO2 generally also lead to the formation of other sulfur oxides. 


Health impact
SO2 is soluble in aqueous media and hence when inhaled, it affects the mucous membranes of the nose and upper respiratory tract. The short-term effects of SO2 exposure are felt very quickly. Most people feel symptoms within minutes of breathing it in. Moreover, the long-term effects are quite severe, sometimes resulting in decreased lung capacity. It irritates the respiratory system and causes inflammation and tightening of airways leading to difficulty in breathing. Longer exposures can aggravate existing heart and lung conditions. People with asthma, the elderly, and children are even more sensitive to SO2 exposures. 

Environmental Impact
SO2 has a direct negative impact on the natural environment. At high concentrations, SOx can harm trees and plants by damaging foliage and limiting plant growth. When deposited, SO2 turns on the leaves of the trees and plants yellow.


Electrochemical method for SO2 monitoring
SO2 monitors working on the electrochemical principle are operated based on the diffusion of sulphur dioxide gas into the respective sensor which results in the production of electrical signals proportional to the SO2 concentration. It allows accurate measurement of even low concentrations of SOx, which is essential in SO2 monitoring for the ambient air. 


[Source: https://docs.smartcitizen.me/Components/sensors/Electrochemical%20Sensors/]
Among all the above principles of SOx monitoring, applications like ambient air monitoring prefer sulphur di oxide monitors based on electrochemistry. This is because they yield more accurate SOx concentrations and are inexpensive in comparison with the others.

7. Oizom’s working principle for SO2 monitoring
Oizom’s POLLUDRONE measures more than 30 parameters including gaseous pollutants like carbon monoxide, sulfur dioxide, nitrogen dioxide, nitric oxide; dust particulates like PM2.5, PM10, noise and weather parameters like rainfall, wind speed, and wind direction. Most of the sensors measuring gases including SO2 work on the principle of electrochemical sensing. Several cities, campuses and universities have deployed the active sampling powered sensor-based air quality monitor POLLUDRONE for drawing actionable insights to tackle the rise in ambient nitrogen oxide concentrations. 

5 Reasons why SO2 monitoring is important
Sulfur dioxide is one of the critical air pollutants produced from the combustion of sulfur-containing fuels, majorly emitted from coal-based energy production resulting in poor air quality.
SO2 is a precursor of other sulfur oxides such as SO3 and many secondary air pollutants including particulate matter, smog, acid rain, etc. which have their negative impact on human health and the environment.
Exposure to high levels of SO2 can lead to long term effects on the respiratory system, especially children, the elderly, and people already suffering from respiratory issues.  
SO2 monitoring is an efficient way to detect and reduce exposure to sulfur oxides which further benefits in reducing the formation of particulate sulfur pollutants like fine sulfate particles, acid rain, and smog. 
Real-time monitoring of SO2 levels helps in calculating air quality index to deliver health advisories as well as formulating an action plan to meet standards.