Acid Rain Lab: Smoke, pH and the Taj Mahal
Link emissions to chemistry to damage: sulphur dioxide and nitrogen oxides become acids in clouds, each pH unit is ten times more acid, and marble, lakes and forests suffer as pH falls; scrubbers and converters reverse it.
Before you try
What if a coal plant had no scrubbers for fifty years? What would the statue downwind look like?
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What happened?
Move a control to see what changes and why.
A simple acid-load-to-pH curve and illustrative damage rates; real rain chemistry depends on wind, distance and the soil’s alkalinity.
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Try these ideas
- Load the 1980s smokestacks preset and run 50 years of rain on the statue.
- Add scrubbers step by step and watch the pH climb.
- Find the pH at which the lake’s fish start to fail.
Why it works
Burning coal releases sulphur dioxide and engines release nitrogen oxides. In clouds these dissolve and react into sulphuric and nitric acid, which fall as rain, snow or fog, often hundreds of kilometres downwind. Clean rain is already slightly acidic, pH 5.6, because of carbon dioxide; pollution can push it to pH 4 or lower, and each drop of one unit means ten times more acid.
Acid rain dissolves limestone and marble, which is why the Taj Mahal’s marble yellows and pits near the Mathura refinery. It strips nutrients from soil so trees yellow and weaken, and it acidifies lakes until fish eggs fail. The cure is at the chimney: scrubbers remove most sulphur dioxide and catalytic converters cut nitrogen oxides; both have cleaned up rain in Europe and North America since the 1990s. In this lab you set the sources and the controls, read the pH and let the years of rain wear the statue.
Check your understanding
Question 1 of 4
The main gases behind acid rain are
Rain at pH 4.6 compared with clean rain at 5.6 is
Acid rain damages the Taj Mahal because
Scrubbers on a chimney
Explain it in your own words
What changed? Why did it happen? Where might you notice this in everyday life?
For parents & teachers
- Put a piece of chalk in vinegar and another in water and compare after an hour.
- Ask: why did the Taj Mahal need a mud-pack treatment?
- Look up the pH of rain in your city if it is measured.