Colorful sunsets and rich scientific harvest; El Chichon: eruption of the century

Eruption of Mexico's El Chichon volcano last April is turning out to be one of the most significant volcanic events of modern times as far as the atmosphere is concerned.

Its Earth-enveloping dust veil is higher and probably more massive than any other yet produced in this century. Moreover, new indications of its extent continue to be found.

Thus David J. Hofmann and James M. Rosen of the University of Wyoming recently reported a new layer of El Chichon particles around 30 kilometers (about 100,000 feet) high. Situated at northern latitudes, it extends at least 8 ,000 km (5,000 miles) laterally, although the exact extent is unknown. This cloud joins the previously known thin dust layer at 20 km, which covers Earth, and the main layer at 26 km, which is spreading over the planet.

El Chichon was not exceptionally dirty. But it produced masses of sulfurous gases. Once in the stratosphere, these yield droplets of sulfuric acid. Unlike ash, which falls out fairly quickly, this acid ''dust'' persists. Hence the massive dust veil. In terms of acid pollution, El Chichon's impact on the stratosphere is at least 40 times that of Mt. St. Helens, according to Hofmann.

The droplets can affect weather in at least two ways. By absorbing solar energy they can warm their region of the stratosphere. And by scattering sunshine back into space, they can cool the surface. There already seems to be some stratospheric warming. It is too early to predict what cooling there may be. But several experts tentatively forecast a drop of about 0.5 degree C. on average over the Northern Hemisphere by late 1983 or in '84. This would probably not have a noticeable weather effect.

El Chichon first erupted last March 29. That eruption probably sent a small cloud to 20 km. Then, after two minor eruptions April 3, the major eruption April 4 sent up a massive cloud to form the layer that now is most dense at 26 km altitude.

This is the most intensely monitored volcanic dust veil in history. Scientists are probing it with ground-based lidar (light radar) and satellite-borne instruments. They are sampling it with aircraft and, as do Hofmann and Rosen, with balloons. Yet they still don't know its full extent. It takes time for acid drops to form.

For example, Hofmann and Rosen say their newly found cloud probably formed recently. They suggest that sulfur dioxide from El Chichon drifted to the north polar region last fall. Then, in chemical reactions enhanced by winter cold, the acid droplets formed.

Whatever its ultimate extent and whatever its climatic effect, El Chichon's dust veil should be around for several years. It will continue to produce colorful sunsets and give a dusty cast to cloudless skies. Also, as the most studied dust veil ever, it should yield a rich scientific harvest. A new kind of 'energy crisis'

The United States faces a new kind of energy challenge. This time it's not energy sources that are lacking, but experts whose specialty is crucial to finding fossil fuels.

They're palynologists - students of spores and pollen. Since certain types of ancient spores and pollen are indicators of coal, oil, and gas, they are important guides to efficient energy exploration. A palynologist can, for example, tell where there is a potential for oil and how deep a drilling crew should go.

''Without palynology the science of energy exploration would be severely limited,'' says Prof. Vaughn Bryant of Texas A & M University. He warns that more than 400 palynologists are due to retire in this decade, with few replacements in sight. US universities are now turning out fewer than a dozen PhD palynologists a year.

''Where are the replacements coming from?'' he asks, adding, ''I do not know of a single recent graduate who has not been offered at least three jobs.'' 'Hot' jewelry

Cloisonne-type jewelry is a popular consumer item based on an ancient art form. It is also mildly radioactive - a characteristic that has led the US Nuclear Regulatory Commission (NRC) to reconsider its safety.

Cloisonne features enamelwork set in hollows formed by a wire frame bonded to a metal backing. The jewelry in question is painted with a glaze containing small amounts of uranium.

In January, the New York State Department of Health reported that some pieces of this jewelry were mildly radioactive. These are yellow-orange or off-white (beige) in color. The commission has now made a preliminary safety evaluation and is considering whether to place restrictions on the sale of such jewelry.

Uranium-containing pigments are used under a specified exemption from NRC regulation. The commission says its preliminary study indicates the jewelry glazes are within the provisions of this exemption.

Jewelry is worn on the person, however, enhancing the radiation exposure, slight though that may be. Thus the NRC says, ''The staff believes . . . that use of the slightly radioactive jewelry does constitute an unnecessary exposure to radiation.''

A commission information officer said this is not to say that people should shun cloisonne. But they should use judgment in wearing it. NRC calculations indicate that continued use of a large piece, say a pendant, with the painted surface in direct contact with the skin for 50 hours a week for a year would result in a radiation dose about one-quarter of that allowed for the skin of workers in the nuclear industry under current NRC regulations. Icy comet

Ask an astronomer what a comet is made of and you are likely to be told, ''dust plus frozen water, frozen ammonia, frozen hydrogen sulfide, frozen methane, and other things icy.'' The so-called ''ice model'' is the leading theory of cometary composition. But until now, astronomers have been unable to confirm directly that comets are, in fact, ''dirty snowballs,'' as proposed by Fred Whipple, emeritus professor at Harvard University.

In a recent letter in Nature, H. Campins, M. J. Lebofsky, and G. H. Rieke of the University of Arizona report what they call ''the first direct evidence for the presence of . . . (water) ice in a comet.'' They have found that Comet Bowell absorbs infrared (heat) radiation in a manner characteristic of water ice.

This evidence, they say, ''provides one of the strongest possible confirmations of Whipple's ice conglomerate model of cometary nuclei.'' They add that it also supports the theory that ''water should be the dominant parent molecule for some of the gases . . . of comets.''

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