SAN FRANCISCO – If you want to ferret out uranium's hiding place
in contaminated soil, freeze the dirt and zap it with a black
light, an environmental scientist reported Tuesday at the
American Chemical Society national meeting. Scientists have long
known that uranium salts under ultraviolet light will glow an
eerie greenish-yellow in the dark. This phenomenon sent Henri
Bequerel down the path that led to his discovery of
radioactivity a century ago. Others since noted a peculiar
feature about the UV glow, or fluorescence spectra, of uranium
salts: The resolution of the spectral fingerprint becomes
sharper as the temperature falls. Zheming Wang, a staff
scientist at the Department of Energy's Pacific Northwest
National Laboratory in Richland, Wash., has now dusted the frost
off the files, applying a technique called cryogenic
fluorescence spectroscopy to uranium in contaminated soil at a
former nuclear fuel manufacturing site. By cooling the sediments
to minus 267 degrees Celsius, near the temperature of liqu