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Sometimes the process to clean up soil can be quite muddy.
Purdue University agronomists Darrell Schulze and Paul Schwab worked with Kathy Banks, head of the School of Civil Engineering, to try to remediate soils contaminated with heavy metals, such as arsenic, cadmium, chromium and lead. At another industrial site in northern Indiana, the researchers tested soil additives, such as phosphorus, organic matter and limestone, as a way to immobilize heavy metals and keep them from affecting the environment.
However, science can be tricky. With detailed analysis, the researchers found that the makeup of the ground was very complex, containing more mineral compounds than previously known.
“While phosphorus worked well for lead, the benefits did not extend to the other metals,” Schulze says. The group also learned that the metals behave differently, depending on which phases they are in. Soil depth was also a factor that affected the remediation process. “A substance may not be toxic beneath the surface, but when it comes in contact with oxygen at the surface, that can make the mineral unstable.”
The researchers are analyzing the data to see what applications do work and how new technologies may improve the remediation process. In the meantime, it may sometimes be better just to leave contaminated land alone.
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