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Soil Pollution Science Fair Project

Decaying Plants and Groundwater Acidity

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Decaying Plants and Groundwater Acidity | Science Fair Projects | STEM Projects
Does rotting plant matter make groundwater more acidic? Dead leaves and stems release chemicals as they break down. Those chemicals seep through the soil and mix with the water below. You set up four large coffee cans in two pairs. One top can holds plain soil. The other holds soil mixed with dead plant material. Both have holes punched in the bottom. Each drains into a lower can filled with pure water. Every two weeks you pour water through the top cans to simulate rain. Then you measure the pH of the water in the bottom cans. Over several readings, you compare how the two water samples change in acidity.

Hypothesis

The hypothesis is that the acids caused by the decaying vegetation will cause an extreme jump in the acidity of the water.

Method & Materials

You will use four large coffee cans to simulate the levels of soil and ground water. You will measure the pH of the water every two weeks and add more water to the top cans.
You will need four large coffee cans, soil, dead plant material, and pure water.

Results

The results showed that the water with soil containing plant matter had a lower pH than the water with plain soil. The pH of the water with plant matter increased over time, while the pH of the water with plain soil stayed relatively constant.

Why do this project?

This science project is interesting because it shows how the decay of plant matter can affect the acidity of ground water.

Also Consider

Variations to consider include testing different types of soil and plant matter, or testing the effects of different amounts of water.

Full project details

Additional information and source material for this project are available below.

Related videos

These videos explain the science behind this project and demonstrate key concepts used in the experiment.
Decaying plant material is organic matter, a basic building block of soil. See how it affects soil in this one minute video!!
The Food and Agriculture Organization of the United Nations presents the importance of healthy soils for healthy lives.
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