Phosphorus total fluxes

Figure 6. Phosphorus flux to the sediment surface. The total flux over study period was 185 mg/m2.

Table 11.2 Summary of phosphorus reservoir amounts, total fluxes, and residence time.

Experimental approaches have been reported by two groups. The group at Gunma University (25) synthesized a prototype of ladder polymers, poly(bicyclosilane)s. Polymers with three, four, and five ladder steps were synthesized, and the bathochromic shifts were measured, Ikehata et al, (26) attempted substitutional doping by thermal neutron irradiation of (SiH) ladder polymers synthesized through the reduction of trichlorosilane with lithium in THE (tetrahydrofuran). Thermal neutron capture by Si will yield P in this process for total flux amounts of up to 10 /cm. The concentration of phosphorus impurity is 0.1 ppm. No serious deterioration was caused by strong neutron irradiation. However, in this study, the detailed properties... 

Howarth et al. (1995) also estimate the total flux of riverine particulate phosphorus to the oceans at 0.23x10 moles P yr , an estimate likely too low because it uses the suspended sediment flux from MilUman and... 

As noted in Table 2, between 40% and 75% of phosphorus buried in continental margin sediments is potentially reactive, and 90% to 100% of phosphorus buried in abyssal sediments is potentially reactive. The reactive phosphorus fraction of the total sedimentary phosphorus reservoir represents that which may have passed through the dissolved state in oceanic waters, and thus represents a true phosphorus sink from the ocean. The minimum reactive phosphorus burial flux was calculated as the sum of 0.4(sFjs) -I- 0.9 (sF ) the maximum reactive phosphorus burial flux was calculated as the sum of 0.75(sFes) -i- 1(sF ). Both the flux estimates and the % reactive phosphorus estimates have large uncertainties associated with them. 

Early approaches to lake eutrophication modelling did not distinguish between inorganic, organic, particulate or dissolved phosphorus (Vollenweider, 1975, 1976). These models consist of a mass balance for total phosphorus in the lake by considering inflow, outflow and sedimentation. They are usually combined with a hydraulic model representing the lake as a well-mixed compartment and, despite their simplicity, are able to describe the major phosphorus mass fluxes in lakes. 

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.

Figure 10. Phosphorus settling rates in 1982, calculated as the sediment-trap-measured depositional flux divided by the total particulate P concentration...

Carbon and Phosphorus Burial Efficiencies. The estimate of diatom carbon demand (12-15 g/m2 per year) is consistent with the flux of carbon to the sediment surface. With sediment-trap fluxes corrected for resuspension, we measured a total annual deposition flux of 12.5 g of C/m2. In comparison, Eadie et al. (24) obtained 23 g of C/m2 for a 100-m station, based on three midsummer metalimnion deployments. Of our total, 83% of the carbon was associated with diatoms, and the primary diatom carbon flux was 10.3 g of C/m2. Thus, about 15-30% of the diatom carbon was regenerated in the water column during sedimentation. Approximately 10% of the diatom flux reached the sediment surface encapsulated in copepod fecal pellets the remaining 90% was unpackaged. 

Total river + Eolian phosphorus flux Total prehuman potentially reactive 10.8-17.8... 

Mobilization of sedimentary phosphorus by microbial activity during diagenesis causes dissolved phosphate buildup in sediment pore waters, promoting benthic efflux of phosphate to bottom waters or incorporation in secondary authigenic minerals. The combined benthic flux from coastal (sFcbf) and abyssal (sFabf) sediments is estimated to exceed the total riverine-P flux (F24(d+p>) to the ocean. Reprecipitation of diagenetically mobilized phosphorus in secondary phases significantly enhances phosphorus burial efficiency, impeding return of phosphate to the water column (see Section 8.13.3.3.2). Both processes impact the... 

Another factor to consider is that the ratio of nitrogen to phosphorus in nutrient inputs from land will tend to reflect the extent of human activity in the landscape. As the landscape changes from one dominated by forests to one dominated by agriculture and then industry, total nutrient fluxes from land increase for both nitrogen and phosphorus, but the change is often greater for phosphorus and so the... 

The CENTURY model simulates losses of nitrogen via gas fluxes (N2, N2O and NOJ, dissolved organic loss, and nitrate leaching loss, while phosphorus is lost via dissolved organic and inorganic phosphorus. Model results (Eig. 15.5b) show that total phosphorus loss is quite high during the first... 

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