Humic acid binding

We have made quantitative measurements of the binding of organic compounds to dissolved humic and fulvic acids. The extent of binding increases as a compounds octanol/water partition coefficient increases or as its water solubility decreases. Humic acids bind compounds to a greater extend than fulvic acids, but there are large differences between different humic and fulvic acids. 

Trtic-Petrovic T and Jonsson JA. Application of SLM extraction for investigation of metal-humic acid bindings. Desalination 2002 148 247-251. 

Bidoglio, G., D. Ferrari, E. SeUi, F. Sena, and G. Tamborini. 1997. Humic acid binding of tri-valent T1 and Cr studied by synchronous and time-resolved fluorescence. Environmental Science Technology 31, no. 12 3536-3543. doi 10.1021/es970294x. 

Thorn K A, KR Kennedy (2002) N NMR investigation of the covalent binding of reduced TNT amines to soil humic acid, model compounds, and lignocellulose. Environ Sci Technol 36 3787-3796. 

Figures 1 and 2 show the effect of temperature on the extent of binding of DDT to both Pakim Pond Humic Acid and Boonton Humic Acid. The Y axis in these figures is the amount of DDT bound to the humic acid in nanograms of DDT per gram of humic acid. The X axis is the free, truly dissolved DDT in nanograms per liter. This is similar to the presentation of an adsorption isotherm. If the slope of the lines is multiplied by 1000 it becomes analogous to a weight-weight partition coefficient ([g DDT/g D0C]/[g DDT/g water]). This will be referred to as the binding constant.

Binding of Various Compounds Bv Pakim Pond Humic Acid... 

Unfortunately there is also some bad news for modelers. Different humic materials bind compounds to dramatically different extents, and the reasons for this are unclear. Figure 6 shows the binding constants of DDT to seven different humic materials. Some of this data is from a factorial experiment which has been published elsewhere.7 Inspection of this data shows that the humic acids and the... 

Davies G., Ghabbour E.A., Cherkasskiy A. Tight metal binding by solid phase peat and soil humic acids. In Humic Substances and Chemical Contaminants, C.E. Clapp, M.H.B. Hayes, N. Senesi, P.R. Bloom, and P.M. Jardine, eds. Madison, WI Soil Science Society of America, Inc., 2001. 

Landrum, R.F., Nihart, S.R., Edie, B J., Gardner, W.S. (1984) Reverse-phase separation method for determining pollutant binding to Aldrich humic acid and dissolved organic carbon of natural waters. Environ. Sci. Technol. 18, 187-192. 

Conditional stability constants have been determined for cadmium binding to humic acid in freshwater, log Kk 6.5 [27], which may be comparable to binding to humic acid coated particles. The experiments demonstrated the importance of cadmium uptake from particles rather than from the dissolved phase. The authors recognised that the overall conclusion was similar to previous studies [28], but there remain inconsistencies in the uptake levels which may be related to the heterogeneity of the systems. Uptake from the intestine into the mucosal cells was not investigated. It was presumed that the material was digested extracellularly by hydrolytic enzymes and the released metal was taken up by facilitated diffusion. 

Cleven, R. F. M. J. (1984). Heavy Metal/PolyacidInteraction. An Electrochemical Study of the Binding of Cd(II), Pb(II) and Zn(II) to Poly carboxylic and Humic Acids. Ph.D. Thesis, Wageningen Agricultural University, Netherlands. 

Beller and Simoneit [20] studied the occurrence of hexachlorophene in extracts of estuarine sediments taken from the Hudson River. Hexachlorophene was detected only in the humic acid fractions of the samples, indicating that it could bind strongly to organic matter and was highly resistant to degradation in that form. 

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