6.4 Buffering Capacity of Soils

Acid Deposition and Buffering Capacity of Soils

The impact of acidic deposition can depend very much on the soil type of the area. Acidic soils are affected much more quickly than a soil with a higher pH. A student of mine investigated this for her Extended Essay, collecting soils from different areas in her home country of Sweden, performing this simple experiment, and relating it to the abundant secondary data available for Sweden.

Another student took a slightly different approach and simply looked at the impact of liming (by adding calcium carbonate) on the pH of one type of soil.

This strategy can also be used to compare the soil underneath coniferous and deciduous forests.

Measuring the soil buffering capacity of soil

1. In a cylinder, place a funnel with a coffee filter inside.
2. Pour 40ml of soil into it.
3. Measure up 100ml of vinegar and measure its pH using a pH-meter.
4. Pour the vinegar onto the soil.
5. Let the vinegar run through for 3 min.
6. Measure the pH of the vinegar at the bottom of the cylinder with the pHmeter.
7. Record your data.
8. Repeat steps 1-7 for all the soil samples.

 Measuring the utility of liming to ameliorate acid deposition

Use the methodology for soil buffering capacity but add different amounts of calcium carbonate to one soil type.

Tip: Ensure that repeats are made 5 times and either 5 soil types or 5 amounts of calcium carbonate are tested.

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