Parameterization of coagulation processes in the formation of transparent exopolymer particles (TEP)


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Silke.Thoms [ at ] awi.de

Abstract

Two different mechanisms have been proposed for the TEP formation, spontaneous self-assembly and particle coagulation. The term "self-assembly" is rather broad and applies to spontaneous aggregation and formation of ordered structures when pre-existing components (separate or distinct parts of a disordered structure) are mixed in correct proportions. The process is reversible and involves systems that are at global or local thermodynamic equilibrium. "Self-assembly" is thus not synonymous with "formation" of structures during an irreversible growth process in a steady state out of the thermodynamic equilibrium. For a kinetic growth process such as coagulation, the components must be able to move with respect to one another. If the components stick together irreversible when they collide, they form fractal-like aggregates rather than micelles, bilayers or other regular structures usually formed by self-assembly. A coagulation of complex pre-existing components can involve self-assembling processes if the components are able to equilibrate between aggregated and non-aggregated states, or to adjust their positions relative to one another in the space of an aggregate. Chin et al. (1998) demonstrated the formation of self-assembled nano-aggregates under laboratory conditions. However, the particle size spectra and the fractal geometry of TEP observed in more natural environment suggest a kinetic growth process, where TEP is formed via coagulation of either individual acidic polysaccharides (PCHO) or self-assembled precursors. In a recent study, the cascade from the exudation of PCHO by algal cells to the formation of TEP was successfully described with a simple two-size-class model for PCHO coagulation. This simple parameterization of the complex coagulation process is useful to take into account PCHO-TEP dynamics into higher scale ecosystem models. In this study, the parameterization of PCHO-TEP dynamics is derived on the basis of the analytical solution of a forced Smoluchowski equation for particle coagulation.



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Conference (Invited talk)
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Not peer-reviewed
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Published
Event Details
International Workshop on Marine Aggregates (IWOMA), 11+12 Dec. 2006, MPI Bremen, Germany...
Eprint ID
16139
Cite as
Thoms, S. (2006): Parameterization of coagulation processes in the formation of transparent exopolymer particles (TEP) , International Workshop on Marine Aggregates (IWOMA), 11+12 Dec. 2006, MPI Bremen, Germany.. .


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