FIGURE 7.5 Tapping mode atomic force microscopy (TM-AFM) images and disaggregation rates (rate of decrease of an equivalent spherical aggregate) of the U.K. Geological Survey peat humic acid (PHA). (A) TM-AFM of a 10 mg l-1 PHA solution adsorbed on mica at pH 3.2, 5 mM NaCl. Scan size is 2 jm x 2 jm. (B) TM-AFM of a 10 mgl-1 solution adsorbed on mica atpH 6.8,5 mMNaCl. (C) Disaggregation rates of the PHA as a function of pH. (C) shows that the aggregates observed in (A) were not at equilibrium (at this concentration, equilibrium corresponds to complete disaggregation, a process that will take months). (The figures were taken from [A, B] Balnois, E., et al. Environmental Science and Technology, 1999. 33(21): p. 3911-17; [C] Avena, M.J. and K.J. Wilkinson, Environmental Science and Technology, 2002. 36(23): p. 5100-05 with permission from the American Chemical Society.)

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