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Cold Shot: Blasting Frozen Soil Sample With Ultraviolet Laser Reveals Uranium

Date:
September 20, 2006
Source:
Pacific Northwest National Laboratory
Summary:
Scientists have long known that uranium salts under ultraviolet light will glow an eerie greenish-yellow. The resolution of the spectral fingerprint becomes sharper as the temperature falls. Researchers at the Pacific Northwest National Laboratory have now begun to exploit this quirk to hunt for previously hidden uranium in contaminated soils, they report at American Chemical Society national meeting.
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Cryogenic time-resolved laser fluorescence spectrometer.
Credit: Image courtesy of Pacific Northwest National Laboratory

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 liquid helium, Wang and colleagues at the PNNL-based W.R. Wiley Environmental Molecular Sciences Laboratory hit a sample with UV laser on a contaminated sample to coax a uranium fluorescence intensity of more than five times that at room temperature.

What is more, other spectra that were absent at room temperature popped out when frozen, enabling Wang and colleagues to distinguish different forms of uranium from one another, including uranium-carbonate that moves readily underground and is a threat to water supplies.


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The above post is reprinted from materials provided by Pacific Northwest National Laboratory. Note: Materials may be edited for content and length.


Cite This Page:

Pacific Northwest National Laboratory. "Cold Shot: Blasting Frozen Soil Sample With Ultraviolet Laser Reveals Uranium." ScienceDaily. ScienceDaily, 20 September 2006. <www.sciencedaily.com/releases/2006/09/060915203610.htm>.
Pacific Northwest National Laboratory. (2006, September 20). Cold Shot: Blasting Frozen Soil Sample With Ultraviolet Laser Reveals Uranium. ScienceDaily. Retrieved August 3, 2015 from www.sciencedaily.com/releases/2006/09/060915203610.htm
Pacific Northwest National Laboratory. "Cold Shot: Blasting Frozen Soil Sample With Ultraviolet Laser Reveals Uranium." ScienceDaily. www.sciencedaily.com/releases/2006/09/060915203610.htm (accessed August 3, 2015).

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