Biogeochemical cycling of elements

As we have seen in Chapter 2, the evolutionary development of the Earth during its geological history was accompanied by the biogeochemical development of the biosphere. The major process at the initial development stages was the planetary differentiation of chemical elements between solid, liquid and gaseous forms with consequent development of biogeochemical cycles of elements in the biosphere. 

The corresponding example of reservoirs is depicted in Table 1. This Table shows current estimates of the most important carbon reservoirs and averaged residence times for carbon in these pools. The lithosphere is the reservoir for the bulk of global carbon, with about 20% of this being in the form of fossil organic fuels. 

Thus to give an idea of the biogeochemical cycling of elements in various media, the examples will be given below for different biosphere compartments like air, terrestrial and aquatic ecosystems. 

We are familiar with the definitions of these reservoirs, but for the aims of this chapter the biosphere includes living organisms and their environments. In addition, the hydrosphere is defined as inclusive of all surface and marine waters and terrestrial ground waters physically isolated soil water is considered as a component of soil/lithosphere. Analogously, soil gas phases are physically isolated from the atmosphere and also will be treated as a component of the solid sphere. 

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Why do continental margins play a dominant role on the biogeochemical cycling of elements ... 

Mason, R. P., Fitzgerald, W. F. and Morel, F. M. M. (1994). The biogeochemical cycling of elemental mercury Anthropogeruc influences. Geochim. Cosmochim. Acta 58, 3191-3198. 

Mason RP, Fitzgerald WF, Morel FMM (1994) The Biogeochemical Cycling of Elemental Mercury - Anthropogenic Influences. Geochim Cosmochim Acta 58 3191-3198... 

BIOGEOCHEMICAL CYCLING OF ELEMENTS AND POLLUTANTS EXPOSURE IN FOREST ECOSYSTEMS... 

Thus, one should mention that the quantitative estimates of various links of biogeochemical cycles of elements and their interactions are of crucial importance for environmental risk assessment for the given ecosystems under anthropogenic pressure. 

Biogeochemical cycling of elements and pollutants exposure pathways in the tropical ecosystems, which occur between 30°N and 30°S, are both intensive and at high probability of risk for human and ecosystem health. The tropical belt receives about 60% of solar radiation inputting on the Earth s surface. The total area of tropical ecosystems is about 40 x 106 km2, with exception of the High Mountain and Extra-Dry Sandy Deserts with strongly depressed life processes. 

In the ecosystems of the Asian part of Russia the values of critical loads for N, CL(N), and S, CL(S), compounds are shown to be less than in Europe due to many peculiarities of climate regime (long winter with accumulation of pollutants in snow cover) and depressed biogeochemical cycling of elements (see section 1). The minimum values of both CL(N) and CL(S) are <50 eq/ha/yr and the maximum ones are >300 eq/ha/yr (Figures 15 and 16). 

By focusing on a molecular elucidation of key biochemical processes in the marine biogeochemical cycles of elements, marine bioinorganic chemistry should help us understand the subtle and complex interdependence of marine life and ocean geochemistry, and how they have evolved together over the history of the Earth. 

Chapter 1. Biogeochemical cycling of elements — General considerations (P.A. Trudinger, D.J. Swaine, G.W. Skyring).. 1... 

In this model, the biogeochemical cycles of elements are coupled to one another through vegetation and soil microbial processes that serve to maintain elemental ratios in biomass within an approximate, nutritionally balanced range (Figure 15). 

Biogeochemical cycling of elements in Forest ecosystems The plant species biomass of Boreal and Sub-Boreal Forest ecosystems accumulates a significant part of living matter of the whole planet. This value is about 700 x 10 tons of dry weight. The biomass per unit area of different Forest ecosystems varies from 100 to 300 ton/ha and even 400 ton/ha in the Eastern European Oak Forest ecosystems. The annual net primary productivity, NPP, varies from 4.5 to 9.0 ton/ha (Table 9). 

If we take any part of the Alps the successive change in soil belt will be as follows the foothills lie in the zone of Broad-Leafed Forest ecosystems with Cb about 2.0 to an altitude of 600-700 m, in the south up to 800-900 m. Above them is the zone of Coniferous Forest ecosystems on mountain Podzols with moderate-to-depressed biogeochemical cycles of elements. The altitude limits are 1,400 in the north and 2,300 m in the south. Above these ecosystems is the zone of Sub-Alpine and Alpine Meadow ecosystems with depressed type of biogeochemical turnover. 

The biogeochemical cycling of elements in these ecosystems can be characterized as moderate in depressions and as semi-intensive in high mountain forest ecosystems with Cambisols the average Cb is equal to 2 and Ct is equal to 0.42. 

Lein, A. Yu., Ivanov, M. V. (1988). The global biogeochemical cycles of elements and human productive activity. Geochemistry, No. 2, 280-291. 

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