Jennifer Phelan at RTI Inc., a research institute in Raleigh, N.C., is using the dirt to study acid rain's harm to forests, starting in Pennsylvania.
Cornell University professor Johannes Lehmann is leading a group of graduate students sifting through soil data for evidence of black carbon, a byproduct of forest fires and industrial smokestacks. The research may increase understanding of global warming.
"Without this sampling effort, we couldn't do this type of research," Lehmann said.
Dirt under the fingernails of a murder victim could help detectives figure out if the body was dumped there but killed elsewhere, said Sarah Jantzi, whose 2013 doctoral dissertation at Florida International University in the field of forensic science drew upon the government work.
A government scientist for 38 years, Smith said those after him can use this soil analysis as a starting point for decades of research. His data is available to anyone who thinks it will advance his or her project.
"The opportunities for further research are almost limitless," he said.
Contact David Smith of the U.S. Geological Survey at firstname.lastname@example.org, or access his soil survey at http://pubs.usgs.gov/ds/801/.
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