But did you know that plants can clean the ground as well? The process is called phytoremediation.

Scientists discovered that certain plants use their roots to pull potentially toxic contaminants from the soil. The plants then trap and store the toxins in their cells, or convert them into less harmful chemicals. For example, poplar trees and mustard plants have been used to remove petroleum contaminants and lead from polluted soil. In Chernobyl, Ukraine, scientists planted sunflowers to remove uranium, which is radioactive, from the ground and water.

After the plants have accumulated the pollutants around them, they are harvested and disposed of safely. Scientists are discovering more and more species that can help clean soil, and these plants are being used to draw out mercury, cadmium, nickel, lead, arsenic, and other toxins.

Phytoremediation has several advantages. Plants can clean large areas more cheaply than other methods. And because the process uses natural organisms, it does not introduce new chemicals into a contaminated site.

But phytoremediation also has its limitations. Cleanup is restricted to the area reached by a plant's roots and to the specific pollutants the plant can uptake. The process can be a long one, especially when the cleaning plants grow slowly, like trees. Finally, wildlife may be at risk if the toxins accumulated in the plants enter the food chain.

So, while some plants may help us clean up the messes we've already made, it's far better to avoid dumping toxins in the first place.  

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A Moment of Science®