How to Measure for Acidic Deposition

You can measure acid deposition by testing the pH of rainwater.

Rainwater is typically a little acidic, because atmospheric carbon dioxide dissolves in the water to form carbonic acid. According to the EPA, a normal pH for rainwater is about ~5.6 or so. In many areas, however, the presence of pollutants like nitrogen dioxide acidifies rainwater so it has a much lower pH -- sometimes as low as 4.3. This phenomenon is called acid deposition or acid rain. You can measure the pH of rainwater in your area by collecting a sample and testing its acidity with a pH meter.

Things You'll Need

• Clean dry plastic bucket
• Calibrated pH meter

Instructions

1. Keep your bucket covered until the rain starts, then take it outside.

2. Bring the bucket back inside once it's half-full or just before the rain stops -- whichever happens first.

3. Remove the pH meter from the buffer storage solution and insert the tip into the water sample. Record the pH reading. This will give you a sense of the acidity of your rainwater.

Tips & Warnings

• Dry deposition is another component of acid deposition that does not involve rain or snow. Unfortunately, according to the EPA, it's very difficult to measure directly and is generally calculated based on atmospheric data instead.

References

• EPA: Measuring Acid Rain
• EPA Region 1: Acid Rain Measurement