Students Test Soil Around Power Plants

Physics students have analyzed soil samples collected over the past two summers from 18 sites in Marquette County to determine if they contain elevated levels of radioactive contaminants from sources such as power plants. Initial results show a slight elevation in the regions of interest, but researchers classify it as “definitely not approaching dangerous levels.” According to Will Tireman (Physics), the dose level detected is about a million times less than a standard chest



Tireman said there are naturally occurring radioactive materials, or NORMS, in soil and rocks. These materials also can be found in coal. When coal is burning, the NORMS are left behind in the solid waste and a portion of this is pushed up the smokestacks in what is called fly ash.


“I remember photos taken in the '40s and '50s in my college history books that showed massive amounts of pollution around factories and power plants and snow that had turned gray from the ash,” Tireman said. “Now the power plants use electrostatic precipitators. They operate on a similar principle as an Ionic Breeze. They snag particles with a charge out of the air. This catches 95 to 99 percent of contaminants. Some do escape and we were looking to see if there are increased levels of one specific NORM in local soils around the power plant.


“There was a little more activity to the south, which follows the hypothesis, given the prevalence of north/northwest winds that tend to carry it in that direction. And there is a falling off of activity the farther the distance from the power plants. But at this point we can’t definitively say it’s because of the coal-fired power plants. The level of NORMS varies widely from region to region, so we need a baseline of what’s normal in the Upper Peninsula.”


For the next phase, Tireman said students will collect samples from more sites in closer proximity to one another, or about one mile apart. The process involves students digging down 18-24 inches to gather samples from the top three layers of soil. They obtain a specific profile for each layer in an NMU laboratory by transferring the soil to a Marinelli beaker and placing it over a sodium iodide crystal housed in a lead-lined box (Tireman, left, and senior Torrey Dupras are pictured by the detector).  


Dupras said the crystal can detect gamma rays, which are high-energy electromagnetic waves given off during the decay of radioactive elements.


“The crystal emits a faint burst of light, which is then converted into an electrical signal whenever it absorbs a gamma ray," Dupras said. "The data are transmitted to a computer and that displays counts of radioactivity at various energies. The levels were so faint that we ran each sample in the gamma-ray detector for 24 hours to get a reading.”


Dupras presented the research project’s preliminary findings at the 18th annual Argonne Symposium for Undergraduates in Science, Engineering and Mathematics held last month at the Argonne National Laboratory in Illinois.


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Updated: December 14, 2007

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