'Old Air'--Sealed Against Time--Sought for Analysis

Times Science Writer

Scientists at Los Alamos National Laboratory are searching the country for old telescopes and other sealed items that might contain "old air" that could help determine whether the world really is experiencing the "greenhouse effect," a warming trend brought on by increased carbon dioxide in the atmosphere.

The scientists are intrigued with the idea that some items have been sealed for many years, and if they could be opened under laboratory conditions, the air inside them should tell how much carbon dioxide was in the air when they were first sealed. If the items can be dated precisely, the results could provide a record of the changes in the level of carbon dioxide.

Fossil Fuel Effect

Many scientists believe the burning of fossil fuels is raising the level of carbon dioxide in the air. Carbon dioxide traps solar radiation in the earth's atmosphere--almost like a glass shield--thus causing the so-called "greenhouse effect." That could lead to rising worldwide temperatures, possibly as much as several degrees over the next century, the Environmental Protection Agency estimates.

The presence of carbon dioxide in the air has been measured in some areas as high as 330 parts per million, believed by some scientists to be substantially higher than the level before the start of the Industrial Revolution. However some scientists disagree whether a greenhouse effect is actually occurring.

The search for "historical air," which is just getting under way, has been concentrated so far in museums, where the records needed to date the items should be most complete, said Allen Ogard of the New Mexico lab, which is operated by the University of California for the federal Department of Energy.

Finding the right items "doesn't look like it's going to be easy," Ogard said in a telephone interview. "We are finding that most things that can be opened, have been," he said.

Problem in Laboratory

It is also proving difficult to extract the air from sealed items without tainting it, he said.

Those problems notwithstanding, Ogard and a co-researcher, Jane Poths, have asked museums across the country to try to locate items that could yield air samples for the study. He said such things as hollow buttons from military uniforms, which can be dated precisely, and hollow decorative hardware are among the artifacts they are seeking.

However, possibly the most promising items are old nautical instruments that had to be sealed against salty air. Those items can be dated reliably, and service records should indicate if and when they have been opened.

The search so far has turned up "some drug bottles in Maine" that were sealed "close to 100 years ago," and a lot of instruments and hollow buttons, Ogard said.

Equipment Developed

The trick, he added, will be to extract the air without destroying the instrument or contaminating the sample. Equipment, frequently consisting of needles that can be inserted into the items, is now being fabricated, but each item will probably call for a different piece of equipment, he added.

In addition, some way must be found to prove that the air contained in the item is as old as the records indicate.

"We're finding it very difficult to do that," Ogard said. One possibility would be simply to sample so many items of the same type that the numbers will yield some degree of confidence.

It will be equally important to be sure that the carbon dioxide was in the air when the item was sealed and did not result from later activity. The item, for instance, must not have been sealed by flame because "burning produces carbon dioxide," Ogard said.

Encouraging Response

In some cases the analysis will have to be done at the museum where the item is housed because it may be too rare to be removed from the area, but museum directors have been encouraging, Ogard said. Ogard is also looking at a sunken river boat in the Mississippi River, which he believes could have many items that contain old air.

But he fears that one recent experience may turn out to be typical as the search moves on in the next six months. Ogard had hoped that cremation urns in a Buddhist temple in Hawaii would yield good samples.

"But they weren't sealed tight enough," he said.

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