Detoxifying Sediments With Electrons and UV Light

The concentration of certain toxic organic chemicals in waterway sediments can be reduced by 83 percent using electron beams—the same technology already used to decontaminate mail—scientists from the National Institute of Standards and Technology (NIST) and the University of Maryland will report in the Sept. 1 issue of Environmental Science & Technology. In an additional series of laboratory experiments, the team found that ultraviolet light also can substantially reduce the concentration of these chemicals.

The results are significant because sediments, soupy mixtures of water and particles of various sizes, arenotoriously difficult and expensive to decontaminate. Further, electron beams and ultraviolet light effectively detoxified the banned chemicals known collectively as polychlorinated biphenyls, or PCBs, which can get into the food chain and increase the risk of cancer in humans. Waterways such as the Hudson River have bottom sediments heavily contaminated with PCBs. However, whether electron beams and ultraviolet light are practical decontamination techniques will depend on cost-effectiveness comparisons to existing methods, such as chemical treatment and incineration. In addition, issues such as availability of electron beams will need to be resolved. The scientists used a beam at the University of Maryland for the recent studies.

Electron beams and ultraviolet light remove chlorine ions (charged atoms) from PCBs, which reduces toxic-ity and enhances prospects for biodegradation of the remaining material by living organisms. The scientists evaluated the effectiveness of the treatment methods in removing PCBs from a NIST Standard Reference Material containing sediments with carefully measured amounts of contaminants. Research continues on additives and conditions that might enhance the decontamination processes. The research is funded by NIST, the university, and the Maryland Water Resources Center.