Nikolai YASAMANOV, Dr. Sc. (Geol. & Mineral.), Lomonosov Moscow State University
Speaking of the natural environment, we use the term ecology. This word was introduced in 1869 by the German biologist Ernst Haeckel (1834-1919) for the science studying the relationship of organisms with their environment. For a long time ecological problems were considered in the context of biology and subsequently, of paleontology. But from the mid-20th century on the ecological approach invaded virtually all disciplines, the hard and the soft sciences alike. Today we are dealing with the ecology of the World Ocean, of organic communities and of conurbations. And so forth. We are witnessing the development of technological, engineering, landscape and medical ecologies, and ecoactivities in other fields as well...
A NEW TREND
Such kind of proliferation of sundry ecologies became a nuisance already in the 1980s, hence the need to bring them into some common denominator of sorts. Four major areas were identified in the long run-namely, the biological, geological, social and applied ecology.
Ecological problems have always been a major concern during geological surveying and prospecting, especially in hydraulic and in engineering geology At first the ecological aspects of such work were designated as geoecology or else geology of the environment; lately, however such notions as ecogeology, ecohydrogeology, and ecogeophysics entered the stage. This ushers in a new trend within the earth sciences. Now all of them - geodynamics, geotectonics, the geology of useful minerals and ore mining-are oriented towards environmental protection. All that has given birth to an intermedia science, the ecological geology (or ecogeology for short). But in what particular does it differ from geology proper and disciplines related to engineering geology?
Each science has its subject-matter and methods. As Professor Viktor Trofimov (Eomonosov Moscow State University) sees it, ecological geography is concerned with the lithosphere, or to be more exact, with its subsurface region subjected to active technogenic effects. Well and good, but the lithosphere is also the object of geology, is it not? Yes, of course. However, ecogeology is involved not only with the specific features of the lithosphere-its range of interests takes in related processes in the biosphere, the atmosphere and the hydrosphere impacting geological processes (which every now and then entail disastrous consequence for the human community as well). That is why the lithosphere, or the earth's shell, is likewise the object of ecological geography.
ECOLOGICAL SPECIFICS OF THE LITHOSPHERE
Thus far only the uppermost part of the earth's shell has been studied well enough. It supplies us with minerals and carries all the various civil- engineering facilities-industrial enterprises, transportation, communications and all. Before determining the extent of environmental modification and the damage that goes with it, we should have a clear idea of corresponding functions of the lithosphere. According to Professor Trofimov, these are the resource-related, geodynamic and geophysical-geo-chemical functions. Partway the latter two affect the atmosphere, the hydrosphere and the biosphere which are in contact with the lithosphere and interact with it.
Now, the lithosphere supplies biota, a totality of living organisms (man including), with vital mineral substances and diverse chemical compounds and elements (in solid, liquid and gaseous form). This is the resource function. The lithosphere is not only a depositary of useful minerals that originated dozens and hundreds of million years ago, it is also a producer of mineral substances consumed by the plant and animal kingdoms. The lithosphere's resource function likewise encompasses what is known as the geological space in which biota exists.
As to the geodynamic functions of the shell, the ongoing processes there are acting, directly or indirectly, on the living world-either by stepping up or by slowing down the vital activity of organisms; this action may be even the cause of their death. For instance, volcanic eruptions that spew forth a large amount of carbon dioxide, steam and vapors, sulfur compounds and other harmful substances. Disastrous earthquakes can
even modify the climate on our planet and trigger huge natural calamities which I will be dealing with below.
Natural and technogenic processes are responsible for geochemical and geophysical anomalies in the lithosphere that may vary in their intensity. Such anomalies affect living organisms via the sanitary-hygienic and medico- biological condition of territories. Thereby the lithosphere has a direct bearing on human health.
LITHOSPHERE'S RESOURCE FUNCTION
A variety of exogenous factors are acting on the terrestrial surface and its rock. These are the circadian and seasonal temperature changes, the atmospheric moisture and the surface waters, particularly if they contain organic and inorganic acids. The temperature differentials erode solid rock and cause cracks and fissures in it; water seeps in and washes out readily soluble compounds and minerals.
Insoluble ore elements are concentrated on the earth surface as a result of rock erosion and denudation and come to be deposited in magmatic, metamorphic rocks transformed by erosion. It is under such conditions that commercial bodies of cobalt and nickel are formed, as well as kaolin (porcelain clay) and bauxites from which aluminum is mined.
We know of deposits formed by sediments accumulated in the water medium. These are rock and potash salts, phosphorites, manganese ores, combustible shales, along with limestone, marl and sand which are used as building materials.
Extant deposits are often acted upon by high temperature and pressure. Then rock and substances they contain undergo significant modifications: quartz sand and sandstone turn into hard quartzites, limestone becomes marble, and granite, acquiring a striated structure, transforms into gneiss. And so some ore bodies vanish without a trace, while others are modified, and still others are enriched. The metamorphic mountain rocks thus formed become ore- bearing.
Conversely, native material on the surface of our planet is subject to degradation too as a result of water erosion. Water washes off various substances from the terrestrial surface and takes them away, either dissolved or suspended. The newly formed
minerals often have a negative effect on the environment, as in the case of weathering and wind erosion: gaseous and readily soluble compounds, once they get into the hydrosphere and the atmosphere, do harm to living organisms. Furthermore, carbon dioxide as well as compounds ofsulfur, methane and ammonia affect the climate on a local and global scale. Soil, and surface and subsurface water are contaminated with toxic oxides and complex compounds which have a dire action on the environment and, penetrating trophic (food) chains, ultimately get into the human organism.
Consequently, weathering and erosion processes are playing a dual role. On the one hand, they are involved in the formation of useful deposits and, on the other, they have a negative effect on the vital activity of organisms. Both effects have manifested themselves throughout the geological history of our planet. And what concerns biota: erosion, while impairing some groups of organisms, is helpful for the development of others. All that is in the scheme of things.
Human civilization has brought about dramatic changes in the situation on the earth's surface. The period of accumulation of lithospheric resources, which took nearly 4 billion years, gave way to open-ended consumption which has been on for several thousand years now. Humankind has been actively transforming the lithospheric surface.
GEODYNAMIC FUNCTION OF THE LITHOSPHERE
Destructive natural processes may be sluggish and imperceptible in their course; but now and then they may come like a bolt from the blue and wreak havoc.
The slow course of geological changes in the lithosphere and surrounding mantles can be broken both by natural and by anthropogenic factors; both have internal (endogenic) and external (exogenic) causes. Say, disastrous events like volcanic eruptions, earthquakes and emanation of gases from the earth's interior are caused by planetary and cosmic factors, that is they are due to inherent, endogenic causes. Now we know it for certain: regions of eruptive and seismic activity are confined to lithospheric plate interfaces. The extension and the convergence or collision of plates interfere with the shell integrity. The faults thus formed are an opportune escape route for plutonic magmaits
flows force their way up to the surface in the form of lava. As to elastic deformations accumulated at the sites of plate collisions or extensions, they are ultimately released in earthquakes which, among other things, may also be triggered by cosmic factors, e.g. planetary gravitation changes, celestial bodies, and meteorites. These, hitting the earth, give off a huge amount of energy that modifies its surface.
And more: the mass extinctions of certain plant and animal species in the last billion years, as some scientists believe, exhibited a definite periodic pattern and - what is most surprising indeed - concurred with the collisions of our planet with the heavenly bodies, the asteroids. A similar event took place 65 million years ago when many species disappeared from the face of the earth, among them, dinosaurs, cephalopod mollusks, plankton foraminifera, the absolute majority of bivalved and gastropod mollusks, and so forth. Such wholesale extinctions occurred between the Paleozoic and the Mesozoic, and the end of the Devonian, between the Proterozoic and Paleozoic, and in other periods.
Some natural processes touch man and his living conditions, though the effect is not as immediate. These are regional and global desert encroachments, soil erosion, karst formation processes, changes in the level of the World Ocean and the like.
NATURAL MEDIUM UNDER PRESSURE
Today the anthropogenic (maninduced) effect on the lithosphere, the atmosphere and the hydrosphere, large-scale and pervasive as it is, is fraught with dire consequences. For one, it results in global changes of the climate and rapid desert encroachment. The combustion of vast amounts of mineral fuel fills the atmosphere with carbon dioxide, sulfur compounds and water vapor; all that intensifies the hothouse effect. In a follow-up of this global process, the surface air temperature has been increasing fast in the past 20- 25 years. The rate of this increase is much above the temperature rises of the Quaternary and even those that took place in the distant geological past.
Global warming is increasingly impacting the natural landscapes: warmer climatic zones are encroaching on polar regions. Consequently, tundra and forest-tundra landscapes are deteriorating fast, and the ice-belts of northern seas are shrinking. The rapid thawing of ice covers in both hemispheres as a result of higher temperatures may cause a significant rise in the level of the World Ocean whose swelling waters would flood vast tracts of lowlands.
There are changes in the location of humid and arid zones. Belts of steppes and forest-steppes are
expanding northwards, with deserts and semideserts moving next. Simultaneously, arid zones are contracting because of the intensive evaporation process touched off by global warming. Permafrost areas are shrinking too.
This notion is still ambivalent. Some experts attribute geopathogenic zones to the heterogeneity of so far unknown fields; but others think they are engendered by deep-seated geophysical and geochemical anomalies which, directly or indirectly, act upon biota's condition. Most likely, geopathogenic zones are an area where the atmosphere, the hydrosphere, the lithosphere as well as the upper and lower mantle of the earth-and possibly its core-display their characteristics in an unorthodox fashion. In turn, geophysical anomalies are thought to be the specific characteristics of corresponding fields- characteristics conditioned by geothermal effects, gravitation, magnetic and electric fields as well as by vibration and acoustic effects of the lithosphere.
Geochemical anomalies, the enhanced radiation background among them, are often of focal occurrence. Such anomalies arise in situ at shallow mineral deposits exhibiting relatively high radioactivity. This concerns not only respective ore bodies but also rock with the enhanced concentration of boron, barium, beryllium, chromium, nickel, lead and other elements whose isotopes are unstable. Also in this category are anomalies caused by anthropogenic pollution in the process of ore enrichment and commercial utilization. Geopathogenic zones occur not only at deposits of high-toxicity compounds but also in the vicinity of mines-say, in dumps and spoil heaps, in purification (sewage) works, and in aeration ponds.
Geochemical factors are capable of inducing various pathologies. Some chemical elements and compounds may be in excess, while others-all too scarce in the natural environment; in either case the effect may be harmful. Some elements are highly toxic, especially beryllium, the main component of beryl. Its bright-green transparent varieties are known as emerald - a precious stone dazzling in its beauty; and another beryl variety is aquamarine, a transparent stone having a pale blue or bluish-green color, also used as a gem. Beryllium is employed in the production of superhard alloys for the atomic industry and aerospace technology. Unfortunately, those who work with beryllium or live near beryllium-producing mills are exposed to a higher risk of lung cancer.
Chromium and arsenic are also a health hazard: chromium causes bronchial cancer, and arsenic compounds induce locomotor diseases and lung cancer. High toxicity is exhibited by cadmium, mercury, thallium and lead. An excess of cadmium provokes atherosclerosis, hypertension, prostatic cancer and decay of bone tissue. Mercury, being a potent mutagen, has an adverse effect on heredity.
Even taken at low concentrations, thallium affects the cardiovascular system; it causes pathologies of joints as well as baldness. Its high concentrations interfere with the function of the gastrointestinal tract, result in hallucinations, convulsions and even death from respiratory paralysis. An excess of lead intoxicates the organisms and may be responsible for malfunctions of the central nervous system, liver, kidneys and the sex organs; lead is also a mutagen and destroys red blood cells.
Besides native elements and compounds, we are now having quite an array of artificially synthesized organic compounds like benzene that causes leukemia as well as vinyl, chloride and bitumens that induce leukemias and liver malignancy. Proceeding from the great variety of pathogenic geochemical accumulations, many experts propose to divide them into two groups: geopathogenic geochemical anomalies related to natural processes, and technopathogenic ones, i.e. those produced by technogenesis. Both kinds of anomalies merit special attention from experts in ecological geology and from geoecologists and medics.
ECOLOGICAL GEOLOGY: WHAT NOW?
Now geology is ecologically oriented too. Its hands-on fields take in every line of vital activity. But let me stress this point: ecogeology has gained recognition only with the progress of technogenesis when the further deterioration of the human environment has made it imperative to study and prognosticate the aftermath of geological and technogenic activities.
Ecological geology has developed scientific methods of its own in the cognition of the world we live in. Like biology and ecology proper, ecogeology proceeds from theoretical concepts on trends in the evolution of material and nonmaterial world. As a science ecological geology must draw upon research methods of kindred sciences, such as physics, chemistry, biology, geography, mathematics and the soil science. Systems analysis is an integral part of this discipline, for its object is a single complex system endowed with a wide variety of characteristics and functions. Today this ecoscience can forecast the ecogeological condition of the natural environment, which is an essential part of new long-term development programs and managerial decision making.
Опубликовано 15 ноября 2022 года
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