S. American Research Focuses on Impacts Of Ozone Depletion

OZONE has been receiving growing attention in this hemisphere in the last several months, as Brazil gears up to host the United Nations Conference on Environment and Development this June.

In this part of the world, the ozone gap in the stratosphere begins at the south pole and occupies a circle almost touching the tip of the South American continent, at about 60 degrees latitude.

"That makes people wonder when it's coming to 35 degrees [about where Buenos Aires lies] as well," says Volker Kirchhoff, general coordinator for space science at Brazil's Institute for Space Research (INPE).

Since 1988, radiation coming through the hole has intensified, and scientists in the region are studying the atmospheric and biological environments to learn about possible impacts.

In Ushuaia, Argentina, at one of the southernmost spots on the continent, the government's Austral Center for Scientific Research is working on two major projects. One of them, carried out with the United States National Aeronautics and Space Administration (NASA), has been measuring solar radiation coming in through the hole since 1988. Scientists so far have found very short periods of high ultraviolet radiation appearing every spring, and they think these are "pieces" of the hole coming north as it di sintegrates. During the dark winter, a vortex motion in the atmosphere above the pole keeps the hole in place, but this breaks down when the sun appears again and the hole mixes with air containing normal levels of ozone.

Argentine biologists and chemists also are experimenting with the effect of radiation on bacteria. So far, the center hasn't found any evidence that the radiation has mutated living creatures, according to Jorge Rabassa, former director of a government science foundation and a local legislator.

But Bedrick Magas, an electrical engineering professor at the University of Magallanes in Puntarenas, Chile, is concerned. "There is a 37 percent or more ozone decrease over our heads, which means that six or seven times more radiation [than normal] is coming to the planet," he says. "Not easily explainable," he adds, is the blindness in salmon, rabbits, sheep, cattle, and horses that has been observed in the area, as well as changes in the reproductive cycles of animals and blossoming periods of plants.

Dr. Rabassa says the animal blindness could be caused by several factors besides radiation, including a virus that was artificially introduced into the region some decades ago to reduce a rapidly growing rabbit population.

In Brazil, scientists are examining the link between human activity and atmospheric ozone. Over the equatorial city of Natal, they have found an ozone increase in the troposphere, the atmospheric layer just below the stratosphere, which is where the world's ozone holes are deepening. Dr. Kirchhoff says this is probably the effect of biomass burning in central Brazil, where farmers clear land by burning vegetation. INPE is also working with NASA to take air samples over the mid-Atlantic and over the Amazo n region. They have observed that the dense Amazon rain forest absorbs ozone produced by the burning.

Local scientists don't agree on how conclusive the evidence is that man is causing the chemical reactions that increase the size of the ozone hole. "Chemicals have a long lifetime in the atmosphere," says Kirchhoff. "What we produced 30 years ago may not have reached the upper stratosphere, so the measurements we take today may not reflect this until later. It's very difficult to prove [a connection] and show it to lay people."

For Rabassa, the evidence of a link is clear, and the blame lies with industrialized countries in the North, which, he says, must stop producing chlorofluorocarbons (CFCs). But he explains that ozone has regularly been coming and going over the earth for the last 600 million years. "If we stop CFC production now, [the atmosphere] will take several decades to recover, naturally."