Phosphorus fluxes

Table 5. Air-Blowing of Fluxes With and Without Ferric Chloride and Phosphorus Pentoxide Catalysts...

The destiny of most biological material produced in lakes is the permanent sediment. The question is how often its components can be re-used in new biomass formation before it becomes eventually buried in the deep sediments. Interestingly, much of the flux of phosphorus is held in iron(lll) hydroxide matrices and its re-use depends upon reduction of the metal to the iron(ll) form. The released phosphate is indeed biologically available to the organisms which make contact with it, so the significance attributed to solution events is understandable. It is not clear, however, just how well this phosphorus is used, for it generally remains isolated from the production sites in surface waters. Moreover, subsequent oxidation of the iron causes re-precipitation of the iron(lll) hydroxide floes, simultaneously scavenging much of the free phosphate. Curiously, deep lakes show almost no tendency to recycle phosphorus, whereas shallow... 

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. 

Table 4-1 Response of phosphorus cycle to mining output. Phosphorus amounts are given in TgP (1 Tg = 10 g). Initial contents and fluxes as in Fig. 4-7 (system at steady state). In addition, a perturbation is introduced by the flux from reservoir 7 (mineable phosphorus) to reservoir 2 (land phosphorus), which is given by 12 exp(0.07t) in units of Tg P/yr...

It has been argued that phosphorus limits oceanic productivity on the million year time scale (Broecker, 1971). The reason is that essentially all phosphorus in the ocean is introduced by rivers and thus ultimately from the weathering of continental rocks. This flux is, in effect. 

Fig. 14-7 The global phosphorus cycle. Values shown are Tmol and Tmol/yr for reservoirs and fluxes, respectively. (T = 10 ).

Coleman, A. S. and Holland, H. D. (in press, January 2000). The global diagenetic flux of phosphorus from marine sediments to the oceans redox sensitivity and the control of atmospheric oxygen levels. In "Marine Authigenesis from Microbial to Global" (C. R. Glenn, L. Prevot-Lucas and J. Lucas, eds), SEPM Publication No. 66. 

Figure 6 Sensitivity analysis of maize seedlings to some model parameter values during the first 10 days of uptake. The curves show how phosphorus flux (F) into the roots responds to differential perturbation to the parameters, a (i.e., 5F/8a). (Model parameters are given in Table 1.)...

Fig. 3-2. I assume that 95 percent of the phosphorus supplied to the surface sea is incorporated into organic matter and returned to the deep sea in particulate form. One percent of the total survives to be buried in sediments. The rest is restored to the deep sea as dissolved phosphorus. The loss to sediments is balanced for the whole ocean by supply by the rivers. The fluxes here are in relative units.

The problem is to calculate the steady-state concentration of dissolved phosphate in the five oceanic reservoirs, assuming that 95 percent of all the phosphate carried into each surface reservoir is consumed by plankton and carried downward in particulate form into the underlying deep reservoir (Figure 3-2). The remaining 5 percent of the incoming phosphate is carried out of the surface reservoir still in solution. Nearly all of the phosphorus carried into the deep sea in particles is restored to dissolved form by consumer organisms. A small fraction—equal to 1 percent of the original flux of dissolved phosphate into the surface reservoir—escapes dissolution and is removed from the ocean into seafloor sediments. This permanent removal of phosphorus is balanced by a flux of dissolved phosphate in river water, with a concentration of 10 3 mole P/m3. 

The first step in solving this problem is to write down a series of equations, one for each reservoir, that expresses the balance between the phosphorus supplied to each reservoir (the source) and the phosphorus removed from each reservoir (the sink). Corresponding to each of the arrows in Figure 3-1 is a flux of phosphorus equal to the water flux multiplied by the concentration of phosphorus in the reservoir from which the water is flowing. Let sat be the concentration of phosphate in the surface Atlantic, sind in the surface Indo-Pacific, dind in the deep Indo-Pacific, ant in the Antarctic, and dat in the deep Atlantic. Express all concentrations in units of 10 3 mole P/m3. 

Consider the balance in the shallow Atlantic reservoir. The flux of phosphorus is... 

The phosphate content of each reservoir is the volume of that reservoir multiplied by the concentration of phosphate in that reservoir. Volumes are constant, so the rate of change of the content is the volume multiplied by the rate of change of the concentration. But for each reservoir, the rate of change of the content is the sum of all the fluxes of phosphorus in (the sources) minus the sum of all the fluxes of phosphorus out (the sinks). Thus, the content of the first reservoir, Atlantic surface, changes at the rate... 

The excessive amounts of nitrogen and phosphorus as well as heavy metals migrate with water fluxes and enter into surface waters. This is accompanied by eutrophication of surface water bodies. 

Human activity has an enormous influence on the global cycling of nutrients, especially on the movement of nutrients to estuaries and other coastal waters. For phosphorus, global fluxes are dominated by the essentially one way flow of phosphorus carried in eroded materials and wastewater from the land to the oceans, where it is ultimately buried in ocean sediments. The size of this flux is currently estimated at 22 x 106 tons per year. Prior to increased human agricultural and industrial activity,... 

Riber, H. H. and Wetzel, R. G. (1987). Boundary layer and internal diffusion effects on phosphorus fluxes in lake periphyton, Limnol. Oceanogr., 32, 1181-1194. 

The global phosphate system is described in Figure 7.10 (Lasaga, 1980). Table 7.1 gives the amounts held by each reservoir, and Table 7.2 the fluxes between reservoirs. Assuming steady-state, calculate the evolution of the world phosphate system if 10000 x 109 kg of phosphorus from fertilizer (mined from an isolated reservoir) were dumped on land in a short period of time. 

For phosphorus,/ 0.01. This means that only 1% of the particle flux that enters the deep-water box during any given mixing cycle survives to become buried in the sediments. Ninety-nine percent is remineralized in the deepwater. 

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