by Vladimir SIROTKIN, Cand.Sc.(Geol. & Mineral.). Lomonosov Moscow State University
OZONE UNDER THREAT
Beginning in the mid-1980s, the ozone layer was discovered to be thinning out rapidly. Its decay has been tracked reliably by ground stations and satellites. It showed holes, or local patches measuring hundreds of thousands to millions of square kilometers, short-lived (from days to weeks), and yet biting deep into the ozone blanket and reducing the ozone (OCO) density by dozens of percentage points. More worrying still is the global depletion of this gas in the stratosphere. Scientists are facing a really tough challenge establishing just how extensive the depletion is. Most researchers, however, lean to the view that the Earth has lost a few percent of its total ozone mass over the recent decades, and that the depletion rate is rising alarmingly. To answer why the concentration of stratospheric ozone should change at all, we first have to look at factors promoting its formation.
First comes solar activity According to modem concepts, ozone (03) is formed by the action of ultraviolet radiation at wavelengths under 240 nm on atmospheric oxygen molecules, followed by atomic oxygen combining with other oxygen molecules (0 + 0 = 03). It would only be natural to expect rising solar activity to increase 03 concentration in the stratosphere. According to a model developed by German scientist Paul Krutzen, however, the number of N0 catalyzing ozone- ruining reactions grows as well. The combined effect of these two opposite processes is not fully understood as yet.
The Earth's magnetic field is another powerful factor controlling ozone concentration in the stratosphere. Evidence of its effect is provided by positive OCO anomalies associated with the Canadian and Siberian planetary magnetic anomalies. Much like a runnel, they suck in, along the lines of the terrestrial magnetic field force, charged particles arriving from the cosmos. On entering the stratosphere, the particles get closely involved in splitting molecular oxygen and forming ozone. The role of the magnetic factor has not, however, received wide recognition, even after it was thoroughly explored in one of the last studies by the late Alexander Khrgian (1910-1992), an ozone pundit in Russia.
As a result of these processes, ozone is concentrated in the stratosphere, mostly at an altitude of 25 to 30 km, where as much as 90 percent of its planetary stores are amassed. This region is what is commonly called the ozone layer. Ozone, however, is spread far from evenly across and in depth of this layer, causing the atmosphere to behave as it does and anomalies to form in the ozone layer. In particular, most Russian researchers put the negative OCO anomalies in the Northern Hemisphere to the meridianal transfer of low-latitude air, essentially lean on ozone, in a process that has intensified in recent decades. Its effect is exemplified by the so-called Azorean event. Russian scholar Valentin Bekoryukov, Dr. Sc. (Phys. & Math.) and his colleagues have established a correlation between the OCO decrease in the North Atlantic and the synchronous northward shift of the Azorean anticyclone center.
Chemical factors, too, play a part of their own. Ozone-killing compounds reaching the stratosphere or forming in it reduce the OCO concentration, too. Today, three groups of compounds, formed around hydrogen, nitrogen, and chlorine, are known to be capable of effectively reacting, in a type of chain reaction (or cycles), with ozone. Moreover, ozone-destroying reactions are stimulated by such powerful catalysts as activated carbon, variable-valence metals (Mn, Co, and Fe), and phosphoric anhydride (P205). In origin, these compounds can be techno-genic, biogenic and endogenic.
Halogenhydrocarbons, or freons, used extensively in various industries and home appliances, are major technogenic ozonosphere killers. In the estimates of my team and myself, this source generates from 0.5 to 0.7 million tons of chlorine a year. The mass consciousness today is obsessed with the leading role offreon chlorine in damaging the ozone layer.
American researchers held at one time that the ozone layer was threatened, among its other killers, by nitrogen oxides exhausted by high-flying supersonic aircraft. Suspicions about the nitrogen hazard first arose in the mid-1970s, after French and Soviet aircraft makers had outdone their US rivals in building airliners of this class. American aircraft companies soon caught up with them, and more research conducted overseas dispelled all suspicions.
Methane is a significant factor adding to the risks to which the ozone layer is exposed. By various estimates, its annual contribution is between 554 and 1,225 million tons (in our own judgment, it does not exceed 500 million tons). Methane tends to form mostly in areas abounding in rice paddies, bogs, and termite anthills.
Endogenic sources, however, are chiefly responsible for ozone layer destruction. Most ozone-killing compounds escape from the Earth's interior where degassing processes are going on. Degassing takes two extreme forms - hot (volcanism) and cold, with numberless intermediate manifestations in between in Nature. Transition from violent volcanic eruption, always attended by ejection of vast amounts of gas, to lazy gas bubbling witnessed on the surface of many bodies of water may be illustrated by several examples.
As the French scientist, F.A. Perret, who watched the Vesuvius eruption in 1906, wrote, "gas explosions were growing more frequent, until they merged into a single uninterrupted gas jet ejected from a crater 500 m wide that reached an altitude of 18 km. The gas streams shot out of the crater at an estimated 500 km per second, and the eruption went on for 18 hours."
According to Harun Taziev, a famous volcanologist, English explorers trekking toward the pass between mounts Erebus and Bird in Antarctica, watched, in September
Articles in this rubric reflect the opinion of the author. -Ed.
1908, "a colossal jet of gas shooting up from there to an altitude twice the height of the Erebus. Despite the heavy snowstorm at the time, the jet was so strong and tense that it stood almost upright." This vapor and gas outburst shot to an altitude of approximately 8 km above the sea level, high enough to penetrate into the stratosphere.
People working in geothermal areas are well familiar with gas jets shooting out of numerous geysers and boiling mud caldera up from several to hundreds of meters.
Ozone-damaging gases break out of the planet's interior on the bottom of seas and oceans as well.
ECHOES OF EXPLOSIVE VOLCANISM
The two sharply different types of volcanism, alkaline-lime and tholeitic, have different effects on the ozone layer. Alkaline-lime type comes first by more than accident. Its mechanism
has been studied exhaustively enough. It occurs mostly at the fringes of the Pacific Ocean. Here, the predominant geodynamic compression conditions cause numberless foci to develop in the terrestrial crust, where the initially reduced fluids (hydrogen and methane) accompanying magma are oxidized to water and carbon dioxide. They play an insignificant, secondary role within gas emanations, without appreciably affecting the ozone layers. In the subsurface foci, however, evolution of basaltic magma in the mantle stimulates the development of acidic rocks that can, because of their high viscosity, form bottlenecks in volcano vents. The bottlenecks are cleared by terrific explosions, which eject large masses of dispersed material as high as the stratosphere, severely damaging the ozone layer.
Drops in ozone concentrations were registered in the wake of explosive eruptions of the Saint Helens in the Cascade Range, western USA, in
1980, El Chichon in Mexico in 1982, and Mount Pinatubo in the Philippines, 1991. Reduced OCO concentration after, for example, the El Chichon eruption (at 17N) held for a year in a strip running north up to 30 N, the affected area spreading up to 60 N in wintertime, driven by meridianal transfer forces.
So far, it is not clear, just for the record, which component of explosive eruption products affects the ozonos-phere the strongest. Its identity is not as important, after all. At explosive eruption time, tens of millions of tons of volcanic dust and millions of tons of gases, including assorted compounds ofsulfur, chlorine, fluorine, and nitrogen, invade the stratosphere at a time. Finally, alkaline-lime volcanoes produce Freons 11 and 12, the selfsame halofluorocarbons, whose industrial counterparts bear the full blame for the destruction of the ozone layer.
...Today, explosive volcanic eruptions are the single, and undisputed,
mechanism of ozone layer destruction. In no way does this help, however, explain, for example, the local anomalies, or holes, including the famous hole over the Antarctica, appearing periodically in the ozone layer.
HYDROGEN: ENEMY NUMBER ONE
1 referred above to tholeitic volcan-ism that may have a damaging effect on the ozonosphere as well. It develops in tensile geodynamic conditions, mostly in mid-oceanic rift systems, and is attended by flows of reduced gases (hydrogen, methane, and nitrogen) that reach the original ground unoxidized, ready to make a decisive contribution to ozone layer destruction. A research team under Valentin Bekoryukov of the Central Aerological Observatory (CAO), the Russian Hydrometeorological Center, have analyzed a series of observation records kept by all ozonometric stations in the Northern Hemisphere over the years of their existence. And they found that minimum ozone concentrations have been registered unmistakably over Iceland, the Red Sea, and the Hawaiian Islands in October. Actually, these places are centers of active tholeitic volcanism. Powerful hydrogen sources have been discovered in Iceland and on the Red Sea bottom, and abnormally high ratios of helium isotopes e/He in escaping gas streams, evidence of their deep-lying origins, have been established for all the three areas.
As I have found, enormous volumes of hydrogen are fed annually from the Earth's interior into the atmosphere as low-temperature gas streams and emissions (cold degassing). In the extent of its effect on the ozone layer, hydrogen is at least a match to chlorine. For want of more facts in hydrogen studies, it is difficult today to estimate the magnitude of hydrogen flows.
Estimates are to start off with methane, the faithful companion of hydrogen in gas emanations. The figure I cited earlier in this article, 500 million tons produced in biogenic processes, is a thousand times larger than the quantity of chlorine released by man-made Freons. Besides, chlorine is unable to destroy ozone in the presence of methane, for it combines with hydrogen, to be removed from the system as hydrochloric acid.
And more. Add another 4,500 million tons of methane of endogenic nature to the 500 million tons of that gas. This large figure derives from the isotopic characteristics of carbon in atmospheric, biogenic, and endogenic methane. This gives us a total annual flow of methane of as much as 10,000 times more (and at least as much hydrogen) than the amount of chlorine released from industrial Freons. This means that Freons cannot trigger a process on a global geo-chemical scale. Moreover, a paradoxical conclusion follows from the above figures: if any Freons do reach the stratosphere, they will protect the ozone layer by weakening the hydrogen cycle.
THE JOURNEY FROM INSIDE THE EARTH TO THE ATMOSPHERE
The question now is: Can methane, chlorine, and hydrogen rise to the stratosphere from the Earth's surface? In modem-day meteorological models, an effective mass transfer between the troposphere and the stratosphere can only occur over the equator where the overheated surface air produces powerful ascending currents that breach the tropopause, the boundary between these two regions.
Our next question is: Can hydrogen rise all the way up across the tropopause without mixing with atmospheric gases, until it is diluted to background concentrations, and enter the stratosphere over a degassing zone? A very convincing answer, 1 believe, is provided by the studies I have done jointly with a research team at Moscow University. We proceeded from an assumption that the centers of more significant ozone anomalies always lie over hydrogen degassing centers. What configuration are then they to have? That would, of course, depend on the weather patterns, or atmosphere dynamics, in a particular region. This is really what we are witnessing. Gases escaping from the Earth's interior are blown away from their vents by the wind, with hydrogen concentration decreasing and that of ozone rising with distance from the
vents. In this situation specifically, small-scale, almost vertical convention plays a leading role in transporting the gases. And, lastly, in an ozone anomaly developing according to our scenario the vertically ascending air current must be gaining in intensity.
To support this general line of reasoning, Nikita Sadovsky and Oleg Kutsenok, researchers at the Molecular Kinetics Chair of Moscow University's Chemistry Department, have, at our request, constructed a mathematical model of a process transferring impurity gases into the stratosphere. They chose turbulent diffusion for the transporting mechanism within the troposphere, assigning the transporting role to molecular diffusion in the tropopause, and came up with the following results: lighter than air gases (hydrogen) released from a point source at ground level can reach the stratosphere at concentrations differing from the background, while heavier than air gases (Freons) do not rise above the tropopause.
We were satisfied with the results obtained for a calm release of hydrogen from a point source. In reality, however, vast quantities of in-depth gases can emanate in spontaneous outbursts within a brief time span and over extensive fractured areas. In these conditions then, gas would rise in water and in the atmosphere in a dynamic pattern of a floating gas bubble. This transportation mechanism is much more efficient than the single-point scenario.
Interestingly, advocates of the technogenic hypothesis about ozone layer destruction do not address the transfer of Freons into the stratosphere at all. They only postulate that Freons are stable and will always get in quantity into the stratosphere. Their first postulate about Freon stability is, however, questioned by German researchers who suggest the possibility of Freons being destroyed at ground level. Their decomposition is catalyzed by quartz particles and some soil types. The planetary desert belt stretching at about 30 N offers a powerful geo-chemical barrier to man-made Freons on their way into the stratosphere. Strong winds whip up millions of tons of small soil particles and sand, and the frequent sandstorms and tornadoes generate violent electrical discharges. Even if some Freons survive in this inferno and reach the equator to be caught in the ascending warm air current, the bulk of them would, together with the desiccated cold and heavy air, slide back in a descending path, to the very same desert belt.
Simple experiments simulating the behavior of Freons in extremely adverse desert conditions could clear up the question of how stable they are at ground level. In any event, if it is established that as little as only a small
percentage of the Freons is destroyed in the troposphere, the models of the technogenic ozone layer destruction hypothesis could be proved wrong.
APROPOS OF CORRELATION
Destruction of the ozonosphere by ascending hydrogen and methane flows is persuasively supported by spatial correlation of deep-lying degassing centers and the more resistant ozone anomalies. It is very simple to explain the Antarctic hole from this perspective. Mid-oceanic rifts provide main escape routes for gases (accounting, in general, for three-quarters of the planetary flows of reduced gases). They converge toward the Antarctica, so methane and hydrogen emanating from them mix together in the atmosphere over the continent and, as is natural to expect, bore the Earth's biggest ozone hole there. We have spoken already about the association of the more enduring anomalies in the Northern Hemisphere with active tholeitic volcanism and hydrogen-methane degassing centers.
Centers of ozone anomalies over Russian territory also tend to coincide with hydrogen degassing centers. Such gaseous flows have been detected by instruments over various fractured zones of the LJrals, the Caspian coast, and the Pamirs. Hydrogen-methane sources have been discovered on the Ustyurt Plateau on the eastern shores of the Caspian, around Lake Baikal, in kimberlite pipes in Yakutia, and on the
Kola Peninsula. The majority of areas overshadowed by occasional ozone anomalies are typically zones of increased seismicity There is a curious temporal correlation between endo-genic activism in Scandinavia and the White Sea area and ruination of the ozone layer over them. In fact, these places are frequented by seismic tremors, up to 7 point quakes recorded several times in the Kandalaksha Bay To remind, this is an area of evolving kimberlite pipes that can, as in Yakutia, function as a powerful source of hydrogen.
In 1996, 1 made a map of ozone anomaly centers over Russia. New ones that emerged in the intervening years coincided with those registered on my map. For example, the center of the largest anomaly (existing between March and May 1997), with OCO concentration reduced by 40 percent, was registered over the Tixi Bay, exactly where another anomaly had been observed two years before. Repeated appearances give us reasons to regard our map as a sort of forecast - in all probability, any ozone anomalies likely to appear over Russia in future will be centered on mapped areas.
HYDROGEN PURGE MODEL
We have constructed a quality model to illustrate the interaction of degassing centers with the ozone layer above them. With reference to the ocean floor in the rift valley of the East Pacific uplift, it is essentially as follows:
Hydrogen and methane rise from the rift into the atmosphere and, reaching an altitude of 20 to 25 km, where the ozone concentration is at its maximum, enter into a chain of reactions with ozone. The complete hydrogen cycle comprises almost 40 reactions, with water as their end result. Water freezes into ice at low temperatures, forming peculiar clouds first spotted under the ozone holes in the Antarctica and termed polar stratospheric clouds. True enough, "polar" is out of place now that similar clouds have been registered later under ozone holes in other latitudes as well, including the Hawaii.
Some solar radiation in the ultraviolet and infrared ranges previously blocked by the ozone layer and heating up the stratosphere could now pour down through the ozone hole and warm up ground air. Meanwhile, the stratosphere looses heat, as the temperature dipole is turned around.
As ground air heats up over a degassing center, atmospheric pressure drops, warm air being lighter than cold air, turning the area into a potential cyclone birthplace. Inevitably the low-pressure area attracts air masses from a high- pressure zone. Classic examples illustrating this scenario are provided by El Niho off the shores of South America and the Azorean phenomenon, of which we spoke above. Iceland is a powerful planetary degassing center and the home of cyclones. South of it an anticyclone is normally centered on the Azores. When gases are ejected and ozone concentration is reduced over the North Atlantic, the center of the Azorean anticyclone starts, in our model, to shift northward...
Significantly, the processes involved in the model add up to produce a synergistic effect. Temperature inversion generates ascending air currents (which are, incidentally, actually registered in and around ozone holes). Pressure falling over a degassing zone stimulates the degassing process (to draw a parallel, reduced pressure in the center of full-force typhoons raises oceanic surface by several meters).
I must say in conclusion that the hypothesis about hydrogen purging the ozone layer offers an advantage of forecasting powers over all other theories. Indeed, once we know the position of a degassing center, it is a sure bet that we can expect ozone anomalies to develop over the area. A few years ago, I published three territorial forecasts, over the Urals, Tixi, and the Indigirka River, which all were fulfilled a year or two on. My latest forecast for the eastern part of the equatorial Pacific was sustained in January 1998, when an anomaly was discovered there by CAO researchers processing satellite data. Early warning was given by
data about powerful hydrothermal systems and hydrogen sources on the ocean floor in that area. In particular, the data pointed to the arched region of the East Pacific uplift 10 to 20 south of the equator. This is one of the Earth's geologically most active regions, where the highest ocean floor spreading rate, an extremely high heat current, and increasing seismicity have been registered.
The discovery of ozone anomalies above the equator has cornered the champions of the Freon hypothesis we dealt with above, for their theory is tied to the parameters of the Antarctic atmosphere. Their position is compounded by the fact that the phenomena examined in this paper are developing in synchronism over the Antarctica and the equator. The hydrogen purge hypothesis attributes this synchronism to intensified indepth degassing at the time when the Earth crosses the perihelion on its circumsolar orbit. This point occurs at the onset of calendar winter and is associated with the Sun's rising gravitational pull on the Earth's molten core containing the planet's largest stock of hydrogen.
This hypothesis can be tested instrumentally without much difficulty It is enough to set up gas meters at hydrogen degassing centers and collate their readings with observation series of nearest ozonometric stations. If temporal correlation is established between gas outbursts and ozone concentration falls, the hypothesis will become a theory and the gas metering stations already in place will turn into facilities to forecast short-term destruction of the ozone layer and its related adverse effects.