Biogeochemical transformations

The annual primary production of organic carbon through photosynthesis is on the order of 70 Pg/yr. The major part of this carbon is decomposed or respired in a process that also involves the biogeochemical transformation of nitrogen, sulfur, and many other elements. Only a small part of the annual primary production of organic carbon escapes decomposition and is buried in marine sediments. On average. 

Export coefficients per unit area of the catchment and per unit time characterize the mass flow (load) of a river water constituent at the outlet of the catchment. For conservative constituents, that is for which no relevant biogeochemical transformation processes are occurring in the river water, the export at the outlet is equal to the sum of all inputs into the river coming from the various point and diffuse sources. This assumption can be regarded as a valuable approximation in alpine rivers for most of the chemical parameters discussed. Export coefficients allow comparing different catchments in size, land use, or other characters describing a basin. 

Nicholas, D.R., Ramamoorthy, S., Palace, V. et al. (2003) Biogeochemical transformations of arsenic in circumneutral freshwater sediments. Biodegradation, 14(2), 123-37. 

Figure 13 Schematic representation of an MOR hydrothermal system and its effects on the overlying water column. Circulation of seawater occurs within the oceanic crust, and so far three types of fluids have been identified and are illustrated here high-temperature vent fluids that have likely reacted at >400 °C high-temperature fluids that have then mixed with seawater close to the seafloor fluids that have reacted at intermediate temperatures, perhaps 150 °C. When the fluids exit the seafloor, either as diffuse flow (where animal communities may live) or as black smokers, the water they emit rises and the hydrothermal plume then spreads out at its appropriate density level. Within the plume, sorption of aqueous oxyanions may occur onto the vent-derived particles (e.g., phosphate, vanadium, arsenic) making the plumes a sink for these elements biogeochemical transformations also occur. These particles eventually rain-out, forming metalliferous sediments on the seafloor. While hydrothermal circulation is known to occur far out onto the flanks of the ridges, little is known about the depth to which it extends or its overall chemical composition because few sites of active ridge-flank venting have yet been identified and sampled (Von Damm, unpublished).

Oremland R. S. (1994) Biogeochemical transformations of selenium in anoxic environments. In Selenium in the Environment (eds. W. T. Frankenberger and S. Benson). Dekker, New York, chap. 16, pp. 389-419. 

Figure 15.2 gives a very simplified picture of some of the more important global biogeochemical transformations. Metaphorically, there are a multitude... 

Tuhela L, Carlson L, Tuovinen OH (1997) Biogeochemical transformations of Fe and Mn in oxic groundwater and well water environments. J Environ Sci Health, A. Environ Sci Engin Toxic Hazardous Substance Control 32 407-426... 

Sulfur can form a number of Inorganic and organic species with oxidation states varying from -2 to +6 and as a result undergoes a variety of biogeochemical transformations In the estuarine environment. Target compounds or Ions for study In the dissolved phase... 

Biogeochemical transformation of organic matter in the soil is not related only to the formation of humus. By the action of microbes the process continues to the... 

Fig. 5.3 Processes governing production, biogeochemical transformations, and fluxes of organic matter on the shelves and slopes of the Arctic Ocean. MIZ = Marginal ice zone. Modified from Anderson and Dyrssen (1989) and Grebmeier etal. (1998).

Biogeochemical Transformation of Oil Compounds in Marine Water Various biogeochemical and physical-chemical processes act within hours of an oil spill on the sea surface to alter its composition and toxicity, most importantly evaporation, dissolution, photochemical oxidation, advection and dispersion, emulsification, and sedimentation (Figure 7). 

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