Fig. 5. Dissolved organic carbon (DOC) adsorption edges on ferrihydrite (Fe₅OH₈·4H₂O) in the presence and absence of As(III): (a) humic acid (peat), (b) Suwannee River fulvic acid, (c) citric acid. Ferrihydrite suspension concentration = 1.00 g L^-1, As(III) = 1.0 mM, DOC = 1.0 mM C, background electrolyte = 0.01 M NaNO₃.