Unit 3- Air

Sulfur Dioxide


Sulfur dioxide (also sulphur dioxide) is the chemical compound with the formula SO2. It is a poisonous gas that is released by volcanoes and in various industrial processes. Since coal and petroleum often contain sulfur compounds, their combustion generates sulfur dioxide unless the sulfur compounds are removed before burning the fuel. Further oxidation of SO2, usually in the presence of a catalyst such as NO2, forms H2SO4, and thus acid rain.[2] Sulfur dioxide emissions are also a precursor to particulates in the atmosphere. Both of these impacts are cause for concern over the environmental impact of these fuels.

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Current scientific evidence links short-term exposures to SO2, ranging from 5 minutes to 24 hours, with an array of adverse respiratory effects including bronchoconstriction and increased asthma symptoms.  These effects are particularly important for asthmatics at elevated ventilation rates (e.g., while exercising or playing.)  

Studies also show a connection between short-term exposure and increased visits to emergency departments and hospital admissions for respiratory illnesses, particularly in at-risk populations including children, the elderly, and asthmatics.

EPA’s National Ambient Air Quality Standard for SO2 is designed to protect against exposure to the entire group of sulfur oxides (SOx).  SO2 is the component of greatest concern and is used as the indicator for the larger group of gaseous sulfur oxides (SOx).  Other gaseous sulfur oxides (e.g. SO3) are found in the atmosphere at concentrations much lower than SO2.      

Emissions that lead to high concentrations of SO2 generally also lead to the formation of other SOx.  Control measures that reduce SO2 can generally be expected to reduce people’s exposures to all gaseous SOx.  This may have the important co-benefit of reducing the formation of fine sulfate particles, which pose significant public health threats.

SOx can react with other compounds in the atmosphere to form small particles. These particles penetrate deeply into sensitive parts of the lungs and can cause or worsen respiratory disease, such as emphysema and bronchitis, and can aggravate existing heart disease, leading to increased hospital admissions and premature death.  EPA’s NAAQS for particulate matter (PM) are designed to provide protection against these health effects.


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Acid rain from sulfur dioxide can damage statues.

Sulfur Dioxide

  • Description: Raspberry bushes are among the many plants vulnerable to the effects of sulfur dioxide.Raspberry bushes are among the many plants vulnerable to the effects of sulfur dioxide.

Sulfur dioxide is a major component in acid rain. One of the byproducts of sulfur dioxide is sulfuric acid, and both can be extremely damaging to plants that are exposed to these chemicals. Exposed leaves can begin to lose their color in irregular, blotchy white spots. Some leaves can develop red, brown or black spots. When the pigments in enough tissue are damaged or killed, plants can begin to lose their leaves. Crop output is greatly reduced and growth can be stunted. This is especially noticeable in young plants.

Sulfur dioxide is typically released into the atmosphere by the burning of fossil fuels and other industrial and manufacturing processes. Plants damaged by sulfur dioxide can be as far as 30 miles from its source, but the most severe damage, defoliation and discoloring is typically found within five miles. For some plants, it can take exposure of only four hours to suffer damage. A wide variety of plants are vulnerable, from alfalfa and carrots to crab apple and fir trees.


Tyndall Effect




The 19th Century Irish scientist John Tyndall was born on August 2, 1820 in Leighlinbridge, Ireland. He studied the Tyndall Effect in 1869.


The Tyndall Effect is the effect of light scattering in many directions in colloidal dispersion, while showing no light in a true solution. This effect is used to determine whether a mixture is a true solution or a colloid. "To be classified colloidal, a material must have one or more of its dimensions (length, width, or thickness) in the approximate range of 1-1000nm."

Because a colloidal solution or substance (like fog) is made up of scattered particles (like dust and water in air), light cannot travel straight through. Rather, it collides with these micro-particles and scatters causing the effect of a visible light beam. This effect was observed and described by John Tyndall as the Tyndall Effect.

Why is the Sky is Blue?

We know that blue light has the shortest wavelength in the visible light spectrum, while red has one of the longest. We also know that light with shorter wavelengths scatters more so than longer wavelengths. Thus, the sky looks blue when viewed away from the sun: the blue light is scattered more and is visible to a greater extent.


Let’s test different solutions for the Tyndall Effect. Pollution, ash, and other particles in the air can cause the Tyndall Effect.



1.     Fill two beakers ¾ full with water.

2.     Measure out 5 grams of each power or soil and put on of them into the beaker.

3.     Stir vigorously.

4.     Shine the laser through the water. What do you see?

5.     Shine the laser through the solution. What do you see?


Record here which solutions exhibited the Tyndall Effect.


This unit will focus on the composition of the atmosphere, chemical reactions, weather patterns, and the build up of greenhouse gases. Experiments will include materials from chemistry, mathematics and meteorology, as well as basic climatology.

Nancy Hamil,
Mar 22, 2012, 8:02 PM
Nancy Hamil,
Mar 22, 2012, 8:01 PM