Biogeochemical processes

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. 

Once the particle-reactive species have been scavenged, subsequent packaging and/or aggregation can result in the flux of particles and particle-reactive species from the water column. Thorium provides a unique way to study the environmental pathways and the biogeochemical processes that affect particle-reactive species. The four useful thorium isotopes are Th = A x yx), °Th... 

The prevalence of sulfur s second most abundant isotope, S, along with the fractionation known to occur in many biogeochemical processes, make isotopic studies of sulfur a potentially fruitful method of unraveling its sources and sinks within a given reservoir. 

Effects of Temporality on In-Stream Biogeochemical Processes and the Structure of Freshwater Communities... 

Farrington JW. 1991. Biogeochemical processes governing exposure and uptake of organic pollutant compounds in aquatic organisms. Environ Health Perspect 90 75-84. 

Gamo, T. (1995) Wide variation of chemical characteristic of submarine hydrothermal fluids due to secondary modification processes after high temperature water-rock interaction, a review. In Sakai, H. and Nozaki, Y. (eds.), Biogeochemical Processes and Ocean Flux in the Western Pacific, Terra Sci. Publ., pp. 425-451. 

Hayes, J. M., Freeman, K. H., Popp, B. N. and Hoham, C. (1990) Compound specific isotopic analyses a novel tool for the reconstruction of ancient biogeochemical processes. In Advances in Organic Geochemistry 1989 (Eds Durand, B. and Behar, F.), Pergamon Press, Oxford, pp. 1115 1128. 

Both ratio of base cations to aluminum, and the aluminum concentrations, are used as indicators for steady-state geochemical and biogeochemical processes. By assigning established critical loads to these indicators (for example, the concentrations of aluminum in soil solution should not exceed 0.2 meq/L and the base cations to aluminum ratio should not be less than 1), it is possible to compute the allowable acidification for each ecosystem. An extensive overview of critical values for the ratio of base cations to aluminum for a large variety of plants and trees can be found in Prof. Sverdrup s papers (for example, Sverdrup et al., 1995 Warfvinge et al., 1992, 1993). 

PROFILE is a biogeochemical model developed specially to calculate the influence of acid depositions on soil as a part of an ecosystem. The sets of chemical and biogeochemical reactions implemented in this model are (1) soil solution equilibrium, (2) mineral weathering, (3) nitrification and (4) nutrient uptake. Other biogeochemical processes affect soil chemistry via boundary conditions. However, there are many important physical soil processes and site conditions such as convective transport of solutes through the soil profile, the almost total absence of radial water flux (down through the soil profile) in mountain soils, the absence of radial runoff from the profile in soils with permafrost, etc., which are not implemented in the model and have to be taken into account in other ways. 

Critical loads of sulfur and nitrogen, as well as their exceedances are derived with a set of simple steady-state mass balance (SSMB) equations. The first word indicates that the description of the biogeochemical processes involved is simplified, which is necessary when considering the large-scale application (the whole of Europe or even large individual countries like Russia, Poland or Ukraine) and the lack of adequate input data. The second word of the SSMB acronym indicates that only steady-state conditions are taken into account, and this leads to considerable simplification. These models include the following equations. 

In accordance with the local maximum of precipitation and the relative low winter temperatures, the most favorable climate conditions for biogeochemical processes and pollutant exposure are in the western part of Spitzbergen Island. Three types of landscapes with corresponding ecosystems are widespread (Dobrovolsky, 1994). 

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