Phytoremediation
Phytoremediation is when plants pull harmful stuff out of dirty soil to help clean it up.
A kitchen sponge sitting in a tray of dirty water slowly soaks up the grime. The sponge draws the mess up into itself, leaving the water in the tray cleaner. Plants work the same way in dirty soil. Their roots pull in harmful things and store them inside, leaving the soil cleaner.
Explaining phytoremediation by grade level
Some plants can clean up dirty ground. Their roots suck up bad stuff from the soil. The bad stuff goes into the stems and leaves. The plant holds it so the dirt gets cleaner over time.
Projects that explore phytoremediation
Phytoremediation puts living plants to work pulling harmful metals out of dirty soil. In this project, plants absorb copper through their roots, and a copper test kit tracks how much copper remains in the soil after the plants grow.
Phytoremediation can work over repeated planting cycles. Thlaspi plants pull zinc from contaminated soil, and four rounds of growth bring the level from 598 ppm down to 565 ppm.