Learning to Extract Arsenic from Plants and Soil

Arsenic is a poison that is a common ingredient in pesticides and herbicides. It is also a common pollutant which has infested some of America’s soil and drinking water. Long term exposure to arsenic can cause various forms of cancer, according to medical experts. Unfortunately, conventional methods of removing arsenic from water and soil are expensive. As a result, many sites contaminated with arsenic are not being cleaned up. There is even a political controversy about what constitutes “safe” levels of arsenic in soil and water.

One technique that looks promising for arsenic cleanup is the introduction of certain plants that extract arsenic naturally, through their root systems. Unfortunately most natural plants with this ability keep the arsenic in their roots, rendering extraction difficult.

Researchers at the University of Georgia have genetically modified an Arabidopsis, a small member of the mustard family, to be resistant to the poisoning effects of arsenic and to move the extracted arsenic through its root system, to its shoots, and eventually to its leaves. In this way, the plants having done their work can be harvested and incinerated, destroying the arsenic and leaving the formerly contaminated site cleansed. It is truly a “green” method of cleaning up arsenic contaminated sites.

Experiments have proven promising. Genetically modified Arabidopsis plants have extracted sixteen times more arsenic than the natural version in tests, Researchers hope that they can create versions of the plant that will extract up to thirty five to fifty times more arsenic than the natural version.

Could this process of using plants to extract materials from soil have other applications? That would depend on whether plants can be genetically engineered to extract other materials besides arsenic – say trace elements of useful metals. Thomas James, a blogger who discusses space exploration issues, suggests that process might work on processing lunar regolith for trace metals, such as iron or titanium. The same green house that could grow food for astronauts on a lunar base could also use genetically engineered plants to extract useful materials from lunar soil, which would be hard and expensive to get to using other mining techniques.

Of course such techniques may not be technically feasible, or economical. Genetically tailored bacteria tailored to “eat” certain metals may be a more viable technique. Still, it would be fascinating if agriculture and mining could be combined in such a fashion.