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New Mexico State University

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Fishing for lead: using fish bones to clean soils at firing range sites

Judith Wright does not throw away fish bones.

s them to remove lead, uranium, TNT and heavy metals during environmental remediation.

Wright, a researcher with Phosphate-Induced Metal Stabilization or PIMS NW Inc., a company working with NMSU, and James Conca, director of the Carlsbad Environmental Monitoring and Research Center (CEMRC), have developed an efficient method of using processed fish bones, called Apatite II, to remove these contaminants from water and soil.

The CEMRC is a unit of New Mexico State University's College of Engineering.

Five pounds of fish bones will remove up to a pound of contaminants, according to Conca. The technology is inexpensive, too. Forty dollars' worth of fish bones will clean more than a million gallons of water contaminated with lead and more than a ton of contaminated soil.

Lead poisoning is the most serious metal problem we face as a nation, particularly in children. It can cause death in severe cases, but even a small concentration of lead in a person's bloodstream can cause loss of mental abilities.

Although lead has been banned from gasoline and paint for many years, the residual effects are still a problem. About one quarter of all children in the United States, especially in urban areas, have clinical levels of lead poisoning.

Teeth and bones are made up of the mineral apatite or calcium hydroxy-phosphate. Apatite has the ability to fit different elements into its structure by replacing one of its components with another element, said Conca. Lead, uranium, manganese, plutonium and strontium can replace calcium; carbonate can replace phosphate; and fluorine and chlorine can replace hydroxyl.

That's why fluoride is added to toothpaste; the fluorine substitutes for hydroxyl and hardens teeth so they do not dissolve as easily when coming into contact with organic acids produced by bacteria in our mouths.

Wright discovered the fishbone possibility as a graduate student in geology at Oregon State University, Conca said. She examined the fossils of tiny animals that first used apatite in the Cambrian period, more than 500 million years ago. These animals, called conodonts, were small creatures with tooth-like hard parts the size of a grain of sand that they used to eat their way into their prey.

The conodonts were successful and flourished for 300 million years, to the end of the Triassic period, Conca said. By studying their chemistry and those of more recent fish, Wright discovered that the fossils were full of heavy metals that had been taken up by their teeth and bones after death when they lay on the ocean bottom. She determined that once they were incorporated into teeth and bones, these metals were stable for millions of years.

Conca said when Wright began working in the field of environmental remediation, cleaning up areas contaminated by various industrial and government practices over the last century, she realized that fish bones could be an ideal material for removing metals from contaminated water and soil. Also, the bones' ability to buffer the acidity or alkalinity of water makes them ideal for ecological applications.

Working with Conca at NMSU over a period of years, Wright has implemented this technology to clean up lead and copper at Camp Stanley, a military firing range in Boerne, Texas, and lead, cadmium and zinc in acid mine drainage at the Success Mine and Mill site in northern Idaho. Together, they obtained a patent on this technology.

Recently, Geof Smith of NMSU's biology department and one of his students, Marissa Martinez, have been successful in working with Wright to use the fish bones to clean up TNT and perchlorate in contaminated military soils.