Giving contaminants the tree treatment

Detecting the presence of contaminants in soil or groundwater is now as simple as tapping a tree, thanks to technology invented at Missouri S&T.


Joel Burken, a civil and environmental engineering professor at S&T, says his process of coring tree trunks to gather small samples takes less time and costs much less than traditional methods for detecting contamination. In recent years, Burken and his colleagues have tested this method — called “phytoforensics” — at more than 30 sites in five countries and eight states.
In past tests, Burken and his students collected coring samples in vials to take back to a laboratory at Missouri S&T for analysis. Now they use a specially designed, less intrusive approach that uses a thin filament called a solid-phase microextraction fiber, or SPME, to detect traces of chemicals at minute levels, down to parts per trillion or parts per quadrillion.
“The process of core-sampling plants has been around for a while,” Burken says, “but we’re taking a new approach that will improve the process on multiple levels. Sampling is easy, fast and inexpensive for quickly identifying polluted areas or contamination patterns.”
Trees act as nature’s solar-driven sump pumps, soaking up water from the ground by using the energy of the sun and the air around them, Burken says. Through a process known as “evaportranspiration,” a tree’s extensive root system absorbs all the water it needs. At the same time, the tree absorbs trace amounts of chemicals in that water and transports it above the ground.
Tapping into several trees in an area suspected of contamination can help engineers more rapidly delineate contaminants in the subsurface. “The only damage to the site is taking a piece of the tree about the size of a pencil and just an inch long,” Burken says.
The conventional approach to testing for groundwater contamination is much more expensive, time-consuming, invasive and arduous, requiring the use of heavy equipment to drill in the ground and the creation of sampling wells to draw water from those sites, Burken says.

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