Metals dissolved organic matter interactions

Finally, the concentration of dissolved organic matter and amount of humic acids are required in order to take into account the interaction of free metallic ions with the dissolved organic matter, especially humic substances. This part of the model has not been fully validated for natural conditions (high diversity and complexity of natural organic matter). Furthermore, dissolved organic matter may interact directly with biological material. 

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. 

Coagulation processes in estuaries are affected by other factors such as clay composition, particle size, and concentration of dissolved organic matter, to mention a few. For example, early work has shown that metal hydroxides can flocculate from dis-solved/colloidal organic matter during the mixing of river-derived iron and seawater in the mixing zone of estuaries (Sholkovitz, 1976, 1978 Boyle et al, 1977 Mayer, 1982) (more details are provided on metal colloidal interactions in chapter 14). Surface sediments in... 

The extrapolation of experimental studies on trace-metal adsorption to natural waters is difficult a particular problem is the formation of both ternary surface complexes involving dissolved organic matter and the aqueous complexation of trace elements by dissolved organic matter. The number of studies trying to shed light on the complexity of these interactions by combined studies of organic matter in the suspended phase and the dissolved phase is incredibly low. 

Yamashita, Y. and Jaffe, R. (2008). Characterizing the interactions between trace metals and dissolved organic matter using excitation-emission matrix and parallel factor analysis. Environ. Sci. TechnoL, 42, 7374-7379. 

In addition to the interactions discussed above, which all depend in part on the ioniz-ability, or at least polarizability, of the surface and the adsorbates, hydrophobic parts of ligands may bind to corresponding parts of surfaces. Thus, if a metal ion is complexed or irreversibly bonded to a hydrophobic molecule, the metal may be incorporated into the bulk or surface of a particle via hydrophobic interaction between the molecule and the solid phase. Such interactions may be quantitatively significant in systems with high concentrations of dissolved and particulate organic matter. 

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