Coronel Bogado SO₂ (so2) Levels

🔬What is SO₂?

Sulphur dioxide is a colourless gas with a pungent smell, produced primarily from burning fossil fuels containing sulphur. It is a major precursor to acid rain and secondary particulate matter.

🏭How is SO₂ Produced?

Sulphur dioxide is produced when sulphur-containing fuels are burned. Coal-fired power plants are the single largest global source, as coal contains 0.5–5% sulphur by weight. Petroleum refineries, metal smelters (especially copper and nickel), and industrial boilers burning heavy fuel oil are other major emitters. Shipping used to be a major source, but the IMO 2020 regulation cut marine fuel sulphur limits from 3.5% to 0.5%. Natural sources include volcanic eruptions — a single large eruption can emit more SO₂ in days than human activity produces in a year — and hot springs. In the atmosphere, SO₂ oxidises to form sulphate aerosols (a component of PM2.5) and sulphuric acid, the main cause of acid rain.

🫁Health Effects

SO₂ is a highly reactive gas that constricts the airways on contact.

Short-term exposure (minutes to hours): bronchoconstriction, wheezing, chest tightness, and shortness of breath. Asthmatics are extremely sensitive — even 5–10 minute exposures at 400 µg/m³ during exercise can provoke severe attacks.

Long-term exposure: chronic bronchitis, increased frequency of respiratory infections, and aggravation of cardiovascular disease. SO₂ also acts synergistically with particulate matter — breathing PM2.5 that carries adsorbed SO₂ increases the harm from both pollutants.

Most vulnerable: people with asthma (SO₂ is one of the strongest asthma triggers among criteria pollutants), children, the elderly, and outdoor workers in industrial areas.

🌍Environmental Impact

SO₂ is the primary cause of acid rain, which acidifies lakes and streams (killing fish and aquatic organisms), damages forests (leaching calcium and magnesium from soil), and corrodes buildings, monuments, and metal structures. The Taj Mahal's yellowing is partly attributed to SO₂-driven acid deposition. Sulphate aerosols formed from SO₂ scatter sunlight and have a cooling effect on climate — paradoxically, reducing SO₂ (for health reasons) has a slight warming effect. SO₂ also inhibits plant growth and reduces crop yields, particularly in leafy vegetables.

🛡️How to Protect Yourself

Check AQI for SO₂ if you live near power plants or industrial areas. If you have asthma, carry your reliever inhaler at all times in high-SO₂ areas. Stay indoors with windows closed during industrial emission episodes or volcanic activity. N95 masks provide some protection against SO₂-laden particulate matter, but gas-phase SO₂ requires activated carbon filters for effective removal. Avoid exercising outdoors in areas with strong sulphurous odours.

📏Safe Levels & Guidelines

WHO (2021): 40 µg/m³ 24-hour mean (no annual guideline — effects are primarily short-term).

US EPA NAAQS: 196 µg/m³ (75 ppb) 1-hour (99th percentile).

EU Directive: 125 µg/m³ 24-hour (max 3 exceedances/year), 350 µg/m³ 1-hour (max 24 exceedances/year).

India NAAQS (CPCB): 50 µg/m³ annual mean, 80 µg/m³ 24-hour mean.

Thanks to desulphurisation technologies in power plants, SO₂ levels have dropped dramatically in Europe and North America since the 1980s, but remain high in parts of South and East Asia.

📡How is SO₂ Measured?

SO₂ is measured using ultraviolet fluorescence analysers (reference method), which excite SO₂ molecules with UV light and measure the emitted fluorescence. Wet chemistry methods (pararosaniline/West-Gaeke) are used as reference but are slow (24-hour samples). Differential Optical Absorption Spectroscopy (DOAS) measures SO₂ remotely by analysing UV absorption spectra. Satellite instruments (OMI, TROPOMI) track SO₂ plumes from volcanoes, power plants, and smelters globally.

💡Key Facts

The 'Great Smog of London' in 1952 killed an estimated 12,000 people — SO₂ from coal burning was a primary ingredient.

A single large volcanic eruption (e.g., Mount Pinatubo, 1991) can inject 15–20 million tonnes of SO₂ into the stratosphere, temporarily cooling the planet by 0.5°C.

SO₂ can be detected by smell at concentrations as low as 1,000 µg/m³ — it has a characteristic sharp, 'struck match' odour.

China reduced SO₂ emissions by 75% between 2006 and 2019 through mandatory flue-gas desulphurisation in power plants.