The EAS is divided into four subsystems: atmosphere (A), hydrosphere (H), pedosphere (P), and biota (B). The atmosphere is a mixture of different gases: mainly nitrogen and oxygen; in lesser concentrations, carbon dioxide, water vapour, argon, etc., which determine the thermal regime of our planet. The hydrosphere's mass is a mass of all water (including salt dilutions and excluding polar ice and glaciers). The pedosphere is soils. All these are exchanging energy and matter with each other, and in turn the EAS is exchanging, however, only energy with space. In particular, the matter exchange is realized by means of the global biogeochemical cycles (see also Matter and Matter Flows in the Biosphere).
The atmosphere, hydrosphere, and pedosphere have stored gigantic amounts of entropy. For instance, the entropy storage of atmosphere is 3.5 x 1022JK—1 that in general is close to the global entropy balance; the storages of other subsystems are significantly larger. The exchange entropy flows that bound them with the biota are relatively weak with respect to their entropy storages, and do not really change their state, but they are able to change the state of biota. Thus, the latter is important for us.
Since the atmospheric CO2 is one of the 'life-forming' gases, it is interesting to estimate its entropy, which is equal to 1 x 1019JK—1.
The biota is defined as all of the Earth's living matter. Apparently, this is one of the reasons why the term 'biosphere' is often used (especially in Anglo-Saxon literature) in the sense of 'biota'. The present bulk of living organisms are confined to land, and their mass (on dry basis) amounts to 1.88 x 10 g. For instance, the oceanic biomass is about 0.5% of that in land. Since the terrestrial vegetation constitutes the most part of biota, mainly contributing to its dynamics, the biota is identified with the terrestrial vegetation.
So, biota is the terrestrial phytomass, put into a thermostat with the mean annual temperature of the Earth's surface, Tb = 15 °C. The total phytomass is known; hence, if only the specific entropy of living matter is also known, there is no problem in calculating the total entropy of biota. However, here we deal with a strongly nonequilibrium system, and it is unknown how to define the entropy in this case. What can be done here is to calculate the entropy of dead organic matter (DOM; in dry weight), j(DOM) = ¿(DOM)/TB, where ¿(DOM) = (16.4-18.4) kJg—1 is its specific enthalpy. Therefore, j(DOM) = 60.4JKT1g~1, and the total entropy of'dead biota' is S(DOM) « 1.1 x 1020JK—1 which is less by two orders of magnitude than the atmosphere entropy.
account that specific entropy of H2O is 3.89J K 1 g \ the total entropy flow SPB = -(60.4 x 1.4 + 3.89 x 2.6) x 1017 = -0.947 x 1019J K-1 yr-1.
There is also a reversible flow of minerals (the nutrients: nitrogen, phosphorus, potassium, etc.), which are used in the process of creation of new biomass. All these substances come into the biota in the form of water solutions, entropy of which is the sum of the water entropy and exactly these elements. Note that their contribution constitutes less than 1% of the contribution of water.
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