Dr. Drew Coleman, assistant professor of geologic sciences at the University of North Carolina at Chapel Hill, and his graduate student Michael Bulleri conducted the study. They presented their results today (Nov. 5) at a national meeting of the Geological Society of America in Boston.
"Based on work I did earlier, we set out to determine if we could monitor near-surface water contamination around a depleted uranium weapons manufacturing site outside Concord, Mass., by measuring uranium concentrations in the living parts of trees growing nearby," Coleman said.
Mikes results have been fantastic. By testing the sapwood the living parts of oak trees he cored close to the site -- he has found a definite bulls-eye pattern around the site where the concentration goes up the closer one gets to it.
Bulleri took all their samples on public and private lands surrounding the facility, which used to be owned by Nuclear Metals Inc. and has been owned by the Starmet Corp. since 1997.
The two tested samples using a thermal ionization mass spectrometer at UNC and a technique known as isotope dilution. They could distinguish between natural uranium from the soil and depleted uranium contamination by measuring the ratios of uranium 238 to uranium 235 in each sample.
Natural uranium has a ratio of 137.88 atoms of 238 for every one atom of 235, Coleman said. The depleted form what is left over after an enrichment process used for making nuclear fuels and bombs has a ratio of about 500 to one.
Trees suck up water beneath the ground and store the radioactivity it contains for many years, he said. Comparing isotopes allows researchers to pinpoint the radioactive contaminations source and level.