Models organic matter interaction

In conclusions, many schemes have been developed for metal ion — phosphate — organic matter interactions in biomineralization. A variety of organic compounds of the kind present in mineralized tissues were found to coordinate calcium ions at neutral or functional sites and in many instances metal ion coordination was accompanied by the binding of phosphate. Although a wealth of information exists on the organic-inorganic interplay, data could not be reduced to a point where a simple model on biological mineralization could be formulated. 

Pullin, M. J. 1999. The thermodynamics and kinetics of iron-dissolved organic matter interactions in model fresh waters. Ph.D. Dissertation, Kent State University. 

Kubicki, J.D. and Apitz, S.E., Models of natural organic matter interactions with organic contaminants, Org. Geochem., 30, 911, 1999. 

Biomass and substrate must be separately described to establish a concept for classification of wastewater directed toward a description of the microbial processes. For several reasons, e.g., to allow widespread application and to observe a basic mass balance, the organic matter expressed in terms of COD is a central parameter for wastewater quality. According to the concepts used in the active sludge models, the classification of wastewater in a sewer network can also be subdivided as outlined in Figure 3.1 (Henze et al., 1987, 1995a, 2000). A direct interaction between sewer and treatment plant processes is therefore within reach. 

Abdul-Talib, S., T. H vitved-Jacobsen, J. Vollertsen, and Z. Ujang (2001), Anoxic transformations of wastewater organic matter in sewers — process kinetics, model concept and wastewater treatment potential, Proceedings from the 2nd International Conference on Interactions between Sewers, Treatment Plants and Receiving Waters in Urban Areas (INTERURBAII), Lisbon, Portugal, February 19-22, 2001, pp. 53-60. 

Parent, L., Twiss, M. R. and Campbell, P. G. C. (1996). Influences of natural dissolved organic matter on the interaction of aluminum with the microalga Chlorella a test of the free-ion model of trace metal toxicity, Environ. Sci. Technol., 30, 1713-1720. 

These types of models, while incomplete, are steps toward the formulation of composite models, which depend on future availability of compositional data. Moreover, these structural models are an important aid in understanding the interactions between anthropogenic chemicals and terrestrial organic matter. However, due to the heterogeneity of humic substances in the environment, provision of an exact, general structure does not seem feasible. 

It would lie far beyond the aim of this chapter to introduce the state-of-the art concepts that have been developed to quantify the influence of colloids on transport and reaction of chemicals in an aquifer. Instead, a few effects will be discussed on a purely qualitative level. In general, the presence of colloidal particles, like dissolved organic matter (DOM), enhances the transport of chemicals in groundwater. Figure 25.8 gives a conceptual view of the relevant interaction mechanisms of colloids in saturated porous media. A simple model consists of just three phases, the dissolved (aqueous) phase, the colloid (carrier) phase, and the solid matrix (stationary) phase. The distribution of a chemical between the phases can be, as first step, described by an equilibrium relation as introduced in Section 23.2 to discuss the effect of colloids on the fate of polychlorinated biphenyls (PCBs) in Lake Superior (see Table 23.5). 

One limitation of the one-solubility parameter model is that it assumes that the solute can only interact with the organic matter through London forces. Although this assumption may be reasonable for SOM, DOM is typically more polar and can participate in other types of van der Waals interactions. These include permanent dipole-induced dipole (Debye) and permanent dipole-permanent dipole (Keesom) interactions in which the degree of binding that occurs depends on the polarizability of the DOM (Gauthier et al., 1987 Uhle et al., 1999). To account for these types of interactions Chin and Weber (1989) segregated the solubility parameter terms into three components to account for all these different types of molecular interactions to... 

Liu, H., and G. Amy. 1993. Modeling partition and transport interactions between natural organic matter and PAHs in groundwater. Environmental Science and Technology 27 1553. 

Thingstad, T. F., H. Havskum, H. Kaas, D. Lefevre, T. G. Nielsen, B. Riemann, and P. J. LeB. Williams. 1999a. Bacteria-protist interactions and organic matter degradation under P-limited conditions. Comparison between an enclosure experiment and a simple model. 

Merdy, R, Hutzlier, S., and Koopal, L. K. (2006). Modeling metal-particle interactions with an emphasis on natural organic matter. Environ. Sci. Technol. 40,7459-7466. 

Figure 6.7. A model for the interaction of organic matter (OM) with calcium carbonate. Variables are total organic carbon (TOC), dissolved oxygen, and composition of organic matter. (After Mitterer et al 1985.)...

Multidisciplinary analytical and numerical models require development. These models should involve considerations of equilibrium and irreversible thermodynamics and kinetics of carbonate mineral-organic matter-water interactions within a sound hydrodynamic and basin evolution framework. 

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