Geochemistry and the Biosphere. Vladimir I. Vernadsky
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role in all the chemical reactions of the Earth’s surface. We can even say that its presence changes the course of these reactions. The quantity of perpetually existing O2 molecules in the Earth’s crust is enormous. It can be determined with sufficient precision. In the atmosphere (the troposphere and the lower stratosphere), the weight of free oxygen or O2 molecules amounts (according to S. Arrhenius) to a minimum of 1.2 × 1015 t and a maximum of 2.1 × 1015 t. This mass exceeds that of many chemical elements in the Earth’s crust by hundreds of thousands of times.
The atmosphere does not contain all the free oxygen; a considerable part is dissolved in waters and mainly in salty water, which makes up the world’s ocean. This amount hardly exceeds 1.5 × 1013 t. Free oxygen is also dissolved in the fresh water on land and dissolved or occluded in snow and ice. But this quantity is much smaller than that of the marine part of the hydrosphere, because according to W. Halbfass, the volume of fresh water makes up only 3.6 × 10-10 % of the volume of ocean water, even when it includes snow and ice, which present the dominating part of the weight of terrestrial water. So, according to W. Halbfass, the volume of ice corresponds to 3.5–4 × 106 km3, the volume of ocean water to 1.3 × 109 km3 (O. Kruemmel), and the volume of the lake, swamp, river, and surface waters maximumly to 7.5 × 105 km3. Furthermore, the whole amount of free oxygen included into sedimentary rocks slightly exceeds 1.5 × 105 t and comprises approximately 1/105 of all the oxygen of the Earth’s surface.
We know that free oxygen exists only on the Earth’s surface. The water of deep springs does not contain it, as was proven in the late eighteenth century by the English physician D. Pearson (1751–1828). The gases of volcanic and metamorphic rocks are almost devoid of it too. The quantity of free oxygen in the biosphere is undoubtedly one of the most precisely estimated physical constants of our planet. It determines the geochemical work of living organisms and allows us to understand the significance of free oxygen in the history of chemical elements. Free oxygen is the most powerful agent among all known chemical bodies of the Earth’s crust; it changes, or oxidizes, a great quantity of chemical compounds, it is in constant motion, and it constantly forms compounds. We know thousands of chemical reactions by which it is captured, and during which it enters the compounds. The most significant ones among these compounds are the oxidized forms of metalloids such as sulfur and carbon (including the compounds of organisms) and the compounds of metals such as iron or manganese.
The history of all cyclic elements of the Earth’s crust is determined by their relation to free oxygen. Recent investigations have even pointed out its major influence in volcanic phenomena. The atmospheric oxygen captured by burning lava yields oxidized products (such as waters, sulfur oxides, etc), and the heat liberated by these reactions plays a most significant role in the thermal effects of lavas. The temperature of lava rising from the entrails of the crust, which has not yet contacted the oxygen of the air, is often hundreds of degrees lower.
In spite of the significance of these reactions for numerous terrestrial processes of this kind, the overall amount of free oxygen on the planet seems constant or almost constant. Evidently, some reverse processes must exist, which liberate free oxygen into the surroundings. We know only one reaction of this kind in the biosphere, if we consider large-scale reactions. This reaction is biochemical; it is the release of oxygen by chlorophyll plastids of terrestrial organisms. This reaction was discovered in the late eighteenth century by J. Priestley, subsequently deepened by the works of outstanding scientists of that time, and presented in all its significance, its general character and its main features, by the scientist T. de Saussure of Geneva at the beginning of the last century.
This reaction of forming free oxygen in the Earth’s crust is undoubtedly not the only one, but as far as we can judge, it is the only one releasing considerable masses of free oxygen to the structure of the atmosphere that envelopes our planet. The excretion of free oxygen outside the influence of life is proved to be, or most probably, due to the processes of radioactive dissociation, decomposition of gases by ultraviolet radiations, and metamorphism. Oxygen must be isolated in the depths of the Earth’s crust, since the compounds rich in oxygen appearing on the surface, such as sulfates and bodies containing ferric oxides, turn into compounds that are poorer in oxygen, or which do not contain it at all, upon reaching the deep layers of the crust. But this free oxygen must immediately enter compounds, for we fail to see its manifestations anywhere.
Even if from time to time and at some places free oxygen rises from the depths of the Earth’s crust, its mass in the biosphere is insignificant in comparison to the amount of oxygen produced in a biogenic way. The isolation of free oxygen in the stratosphere under the influence of ultraviolet radiation and in connection with decomposition of water vapor and perhaps carbon dioxide, might prove to be much more important. This field of phenomena is still less studied and recorded than the isolation of oxygen in the metamorphic envelope. But two circumstances that greatly diminish the geological significance of this phenomenon should be taken into consideration:
1 The small mass of the rarefied gases in the stratosphere and higher.
2 Their slow exchange with the troposphere.
Finally, there is a third factor to be considered: the dissociation of water molecules under the influence of alpha- and partly beta-radiation of the ubiquitous atoms of radioactive elements. The existence of these phenomena is certain, but nowhere do the concentrations of such atoms seem large enough to be taken into account within the limits of the biosphere. Unfortunately, this phenomenon is not sufficiently studied either through experiment or natural observation.
In view of all this, we can assert now that the free oxygen of the troposphere and the surface waters (gases dissolved in natural waters; i.e., more than one-fifth of the troposphere) is created by life. Furthermore, a quite similar phenomenon is observed for the free nitrogen of the troposphere, and it will be correct to conclude, and to take into account from now on, that the terrestrial gaseous envelope – our air – is created by life. Thus, the history of free oxygen turns out to be a clear measure of the geological and geochemical significance of life.
6 living matter
Life manifests itself in the Earth’s crust in a way that is different from the phenomena studied by biologists. Here we notice two new features of its structure. We see that life acts only by means of the energy, quantity, and composition of the matter inherent to it. Secondly, we see that individual organisms move to the background in regard to the greatness of the observed phenomena; we notice only the general, total effects of their activity.
The geochemical manifestations of life present a picture quite opposite to that imagined by biologists and clearly expressed in Cuvier’s definition of life more than 100 years ago. The effect of organisms on the migrations of elements of the Earth’s crust has almost completely moved to the background, but the matter of the organisms, the motion of its molecules and its energy, manifest themselves in all the observed phenomena. Such a manifestation of life is as real as the richness and complexity of morphological and physiological processes that are studied by biologists as the only reality. Suggesting a new standard of studying life that is completely different from the usual one, we approach unprecedented phenomena and prospects. The complex effects of minute phenomena, which have not attracted the biologists’ attention up till now, reveal an unexpected scope.
In geochemistry, life manifests itself through the joint activities of myriads of living organisms. In this totality the statistical laws and generalizations connected with life are studied. Only some separate properties of life attract the mind. In order to be able to study life in geochemistry, it is necessary to present it in the same terms, with the same logical parameters, as other forms of existence of chemical elements to which we are comparing it here; that is, minerals, rocks, magmas, water solutions, and dispersions. In other words, the totality of organisms must be expressed only from the standpoint of their mass, their chemical composition, their energy, their volume, and the character of the space corresponding to them.
Expressing the totality of organisms in these parameters, we should introduce new concepts, new terms for denoting life. I will refer to the totality of living matter expressed in mass, chemical composition, units of energy, and