Biogeochemical effects

The chemical composition of soils is the result of a series of processes that ultimately link the soil to the history of the universe (Volume 1), with the principal processes of chemical differentiation being (i) chemical evolution of universe/solar system (ii) chemical differentiation of Earth from the solar system components and (iii) the biogeochemical effects of soil formation on cmstal chemistry. 

The biogeochemical processes that generally describe the interaction of elements with particles are quite well known dissolution, flocculation, ion exchange, sorption, (co)precipitation, electron transfer, and biological uptake. In aquatic environments these reactions often occur simultaneously and competitively. In order to utilize marine tracers effectively, we must understand how elements are associated with particles and sediments. 

Feedbacks may be affected directly by atmospheric CO2, as in the case of possible CO2 fertilization of terrestrial production, or indirectly through the effects of atmospheric CO2 on climate. Furthermore, feedbacks between the carbon cycle and other anthropogenically altered biogeochemical cycles (e.g., nitrogen, phosphorus, and sulfur) may affect atmospheric CO2. If the creation or alteration of feedbacks have strong effects on the magnitudes of carbon cycle fluxes, then projections, made without consideration of these feedbacks and their potential for changing carbon cycle processes, will produce incorrect estimates of future concentrations of atmospheric CO2. 

Woodmansee, R.G. Wallach, L.S. Effects of fire regimes on biogeochemical cycles In Fire Regimes and Ecosystem Properties, Proceedings. USDA, U.S. Forest Service, GTR-WO-26, 1981,... 

An important example of non-linearity in a biogeochemical cycle is the exchange of carbon dioxide between the ocean surface water and the atmosphere and between the atmosphere and the terrestrial system. To illustrate some effects of these non-linearities, let us consider the simplified model of the carbon cycle shown in Fig. 4-12. Ms represents the sum of all forms of dissolved carbon (CO2, H2CO3, HCOi" and... 

Although it is one of the smallest reservoirs in terms of water storage, the atmosphere is probably the second most important reservoir in the hydrosphere (after the oceans). The atmosphere has direct connections with all other reservoirs and the largest overall volume of fluxes. Water is present in the atmosphere in solid, liquid, and vapor forms, all of which are important components of the Earth s natural greenhouse effect. Cycling of water within the atmosphere, both physically (e.g. cloud formation) and chemically, is also integral to other biogeochemical cycles and climate. Consult Chapter 17 for more details. 

Cronan, C. S. (1984). Biogeochemical responses of forest canopies to acid precipitation. In "Direct and Indirect Effects of Acidic Deposition on Vegetation" (R. A. Linthurst, ed.), pp. 65-79. Butterworth, Boston, MA. 

Aber, J. D. and Driscoll, C. T. (1997). Effects of land use, climate variation, and N deposition on N cycling and C storage in northern hardwood forests, Global Biogeochem. Cycles 11, 639-648. 

Mercury provides an excellent example of the importance of metal speciation in understanding biogeochemical cycling and the impact of human activities on these cycles. Mercury exists in solid, aqueous, and gaseous phases, and is transported among reservoirs in all these forms. It undergoes precipitation-dissolution, volatilization, complexation, sorption, and biological reactions, all of which alter its mobility and its effect on exposed populations. The effect of all... 

---