Phosphorus models

Enfield, C. G. (1978). Evaluation of phosphorus models for prediction of percolate water quality in land treatment. In State of the Knowledge in Land Treatment of Wastewater (H. L. McKim, ed.), Vol. 1, pp. 153-162. U.S. Army Cold Reg. Res. Eng. Lab.) Hanover, New Hampshire. 

The present paper reports on the catalytic properties of selected aluminophosphate molecular sieves in model hydrocarbon reactions. The molecular sieves were selected to represent large and medium pore sizes with a variety of framework elements including transition metals, in addition to aluminum and phosphorus. Model reactions were chosen to explore catalytic performance in paraffin, olefin and aromatic rearrangement reactions to probe molecular sieve character, shape selectivity and catalytic activity, particularly for reactions involving olefins or olefin reaction intermediates. 

The review of phosphorus models by Lewis and McCechan (2002) showed that one of the major differences in phosphorus cycling models is the number of inorganic and organic phosphorus pools and the ability to measure them in the laboratory. Models such as CENTURY have included phosphorus pools that are conceptually important for the model structure, but are difficult to measure. For example, the CENTURY model includes separate pools for parent phosphorus, strongly sorbed phosphate and occluded phosphorus, while... 

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... 

A further limitation of the CENTURY phosphorus model is the lack of an explicit representation of the impact of soil enzymes on the mineralization of organic phosphorus compounds. The results presented in this book indicate that there is limited data with which to quantify the relative importance of enzymatic hydrolysis of organic phosphorus [biochemical mineralization) vs. organic phosphorus mineralization associated with the decomposition of organic compounds [biological mineralization). It is very difficult to develop models that include enzymatic mineralization of organic phosphorus without data to quantify the relative importance of this process. 

Jones, C.A., Cole, C.V., Sharpley, A.N. and Williams, J.R. (1 984) A simplified soil and plant phosphorus model. 1. Documentation. Soil Science Society of America Journal 48, 800-805. 

Embedding Organic Phosphorus Models in Biogeochemical Models of Aquatic... 

Chaubey, L, K. W. Migliaccio, C. H. Green, J. G. Arnold, and R. Srinivasan. 2007. Phosphorus modeling in Soil and Water Assessment Tool (SWAT) model. In D. E. Radcliffe and M. L. Cabrera (eds.) Modeling Phosphorus in the Environment. CRC Press, New York. pp. 161-189. 

The determination of TP, condensed and organic phosphorus all require predigestion and/or hydrolysis of the water sample prior to detection of the orthophosphate produced. Complete conversion of particulate and filterable components requires conditions that are conducive to dissolution of phosphate mineral phases, hydrolysis of condensed phosphates, and oxidation of organic phosphorus species. Niunerous methods have been proposed, but whichever procedure is selected for the determination of TP or FTP, the digestion efficiency should be assessed using appropriate certified reference materials and a range of organic or condensed phosphorus model compounds. The latter should include compoiuids such as tripolyphosphate, inositol hexakisphosphate, and 2-aminoethylphosphonic acid that contain P-O-P, C-O-P, or C-P chemical bonds, respectively, and that are known to be more refractory. 

In this way, the near-linear chlorophyll-phosphorus relationship in lakes depends upon the outcome of a large number of interactive processes occurring in each one of the component systems in the model. One of the most intriguing aspects of those components is that the chlorophyll models do not need to take account of the species composition of the phytoplankton in which chlorophyll is a constituent. The development of blooms of potentially toxic cyanobacteria is associated with eutrophication and phosphorus concentration, yet it is not apparent that the yield of cyanobacterial biomass requires any more mass-specific contribution from phosphorus. The explanation for this paradox is not well understood, but it is extremely important to understand that it is a matter of dynamics. The bloom-forming cyanobacteria are among the slowest-growing and most light-sensitive members of the phytoplankton. ... 

A transition structure model was proposed which accounts for the high selectiv-ities obtained for some of the substrates [80]. In the structure shown in Scheme 6.37 the two phosphorus atoms of the Tol-BINAP ligand and the two car-... 

So far, we have not considered whether terminal atoms, such as the Cl atoms in PC15, are hybridized. Because they are bonded to only one other atom, we cannot use bond angles to predict a hybridization scheme. However, spectroscopic data and calculation suggest that both s- and p-orbitals of terminal atoms take part in bond formation, and so it is reasonable to suppose that their orbitals are hybridized. The simplest model is to suppose that the three lone pairs and the bonding pair are arranged tetrahedrally and therefore that the chlorine atoms bond to the phosphorus atom by using sp hybrid orbitals. 

Van Cappellen, P. and Ingall, E. D. (1994). Benthic phosphorus regeneration, net primary production, and ocean anoxia A model of the coupled marine biogeochemical cycles of carbon and phosphoms. Paleoceanography 9,677-692. 

Reckhow KH (1979) Empirical lake models for phosphorus development, applications, limitations and uncertainty. In Scavia D, Robertson A (eds) Perspectives on lake ecosystem modeling. Ann Arbor Science, Ann Arbor, Michigan... 

One key point to note is that many of the representations used in chemistry teaching are a combination of symbols and models that is they involve both purely symbolic features and other forms of representation that involve less arbitrary features. For example, a figure such as Fig. 4.2 is a representation of one molecule (i.e. at the sub-microscopic level) of an allotrope of phosphorus. 

As just mentioned, phosphorus porphyrins have unique photochemical properties. Their photophysics is also interesting. Emitter-quencher assemblies based on porphyrin building blocks have attracted attention due to their potential to serve as models in photosynthetic research (see [90] for an example) or for the development of photoswitches that could be used for the fabrication of molecular electronic/optical devices. In this context, Maiya and coworkers constructed a P(VI) porphyrin system 59b with two switchable azobenzene groups positioned in the apical positions of the pseudo-octahedral phosphorus atom [92]. Photoswitch ability (luminescence on/off) was demonstrated as... 

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