Phosphorus gaseous loss

Wetlands and aquatic systems are recipients of phosphorus loads from upland systems. Increased loading of phosphorus to a system can cause nitrogen limitations. The phosphorus enrichment of P-limited systems leads to eutrophication and ecosystem stress. The phosphorus cycle does not have a significant gaseous loss mechanism. Thus, most of the added P accumulates in the systems. 

Tricresylphosphate can also be obtained by the continuous technique. In this case etherification is carried out in a cascade of consequtive reactors operating at increasing temperatures the maximum temperature can reach 200 °C if the reaction is catalysed with metal halogenides. To reduce the losses of phosphorus chlorooxide with gaseous hydrogen chloride, the process should be carried out at reduced pressure. 

Plant species differ widely in the extent of phosphorus absorption by their roots. Forest trees take up P from insoluble compounds with the help of mycorrhizas, whereas phosphorus is removed from soils by harvested crops ( 6 kg ha in agriculture), erosion and to a small extent by leaching (-0.1 kg ha ) and volatilization as phosphine PH3. In the case of erosion, colloids with their surface-bound P are transported into surface waters, and this leads to the eutrophication of aquatic ecosystems, for example in lakes. Leaching losses occur only in sand and peat soils, and in the case of organic phosphates. Under extreme redox situations - as in some paddy soils - phosphate is reduced to PH3 as a gaseous product. 

Fig. 15.6. CENTURY model-simulated results for soil phosphorus loss (organic and inorganic phosphorus) total nitrogen loss (nitrate, gaseous nitrogen and dissolved organic nitrogen) and nitrate loss (a) and change in live leaf carbon-to-nitrogen and carbon-to-phosphorus ratios (b) for the Hawaiian 4.1 million year soil chronosequence.

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