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THE CLINCH RIVER supplies the city of Oak Ridge with its drinking Water. The yellow arrow points to the monitoring station at Oak Ridge National Laboratory.
OAK RIDGE NATIONAL LABORATORY

World events of the past two years have brought with them a number of new worries for the average American. The safety of the water supply, the risk of highjackers, and the threat of chemical and biological weapons being used on our shores have moved to the front of the country's collective consciousness. At the 225th national meeting of the American Chemical Society last month in New Orleans, presentations focusing on domestic security concerns were a noticeable addition to the program, with scientists outlining new ways to detect dangerous chemicals and describing novel applications of time-proven techniques.

RECRUITING NATURE

The nation's water reservoirs are a potential target for future terror attacks. In recognition of that, the Bioterrorism Act of 2002 authorized the use of $160 million in federal funds for vulnerability assessments of drinking water systems. In New Orleans, Elias Greenbaum of Oak Ridge National Laboratory outlined a unique approach to screening water reservoirs. Instead of spending a lot of time and energy designing and manufacturing a complicated sensor, his team recruited some of nature's own workers for the task: algae.

"If you look at any river, lake, reservoir, stream, pond--any surface water--even if it looks pretty clean, there will be algae growing in the water, " Greenbaum notes. He should know: his primary focus in the laboratory is studying the organisms' photosynthetic mechanisms. Because algae are sensitive to even the slightest change in their environment, they are suitable for monitoring for potential pathogens. The idea to put algae to work as aquatic sentinels started nearly two years before the 9-11 attacks with a routine call for proposals from the Defense Advanced Research Projects Agency (DARPA), the research and development arm of the Department of Defense. "The connection between using certain physiological parameters of algae and other photosynthetic organisms to try and detect either deliberate or unintentional toxins seemed like a reasonable thing to do," Greenbaum recalls.

During photosynthesis, green plants convert light energy into chemical energy, but like most such processes, this one is not 100 percent efficient. The lost energy leaks back out of the plant as it fluoresces, or emits radiation of a different wavelength than the incident light almost immediately after absorbing it. Different plants show varying patterns of fluorescence over time. The team at ORNL uses these so-called fluorescence induction curves--which are a measure of the algae's health--to monitor for toxins. Real-time, continuous measurements of the fluorescence from algae in surface waters, the researchers have found, can effectively reveal the presence of dangerous chemicals through their effects on the organisms. "In the last couple of years modern fluorometric instrumentation has advanced to the point where one can detect the fluorescence from algae in as-is, untreated water," Greenbaum says. "That is, you don't have to concentrate the sample in order to improve the signal."

So far, laboratory tests have shown that algae are reliable indicators of hazardous substances such as cyanide and the herbicides Paraquat, which destroys mucous membranes, and DCMU, which was often used in conjunction with Agent Orange. Greenbaum and his colleagues also monitored algae from the Clinch River near ORNL, which supplies Oak Ridge with its drinking water, and proved that their technique will work, in principle. Recently the laboratory joined with United Defense to manufacture a prototype system, dubbed AquaSentinel^SM, that can be deployed in the field.

SHRINKING BENCHTOP INSTRUMENTATION

The key piece of ORNL's novel detection method may not even be visible to the naked eye. Robert J. Cotter and Ben D. Gardner of Johns Hopkins University described the progress being made toward shrinking what has typically been a laboratory behemoth, the mass spectrometer, in order to use the instrument for homeland defense. Mass spectrometry, in which compounds are ionized and then identified based on how the charged particles behave, is a good candidate for rapidly detecting and identifying biological agents. "Everything has a mass," Cotter points out, "so everything is up for grabs in a mass spectrometer."