Acid Rain Lab – Rain pH, Materials, Lakes, Forests and Seeds

What it shows

Burning fuel releases SO₂ and NOₓ, which form sulfuric and nitric acids in clouds and lower the pH of rain below the 5.6 of clean rain. This lab calculates rain pH from emissions and lets you measure what that rain does: marble, iron, copper and granite in a drip test; a lake and forest over 60 years on limestone, basalt or granite; and cress or radish seeds watered at different pH. Bedrock and soil buffering decide how quickly a lake acidifies and which animals survive. The rates are typical teaching values.

How to use

Set the SO₂ and NOₓ emissions and press Collect rain to record a pH sample. On Materials, choose a material, rain pH and days, then press Start drip. On Lake and forest, pick a bedrock and press Run; use Record sample or Add lime at any time. On Germination, pick a seed and pH set and press Germinate. Compare the tables and graphs, then answer the self-check questions.

Parameters you can change

• Experiment Rain, Materials, Lake and forest, Germination
• SO₂ emissions 0–10 t/km²/yr
• NOₓ emissions 0–6 t/km²/yr
• Material Marble, Limestone, Iron, Copper, Granite
• Rain pH in the drip test 3–5.6
• Length of the drip test 10–120 days
• Bedrock Limestone, Basalt, Granite
• Seeds Cress, Radish
• pH of the dishes pH 2–7, pH 3–5
• Seeds per dish 10–50

Questions to explore

1. Which lowers rain pH more, 1 t/km²/yr of SO₂ or 1 t/km²/yr of NOₓ, and why?
2. After 60 years at the same emissions, how do lake pH and surviving animals differ on limestone and granite?
3. As the pH of the water falls, which suffers first, germination or root length?