Fig. 5. Total and dissolved CN, SO₄, Ca, pH, and pe in the effluent from a soil column leached with a sequence of influent solutions: (i) 100 mM CaCl₂ solution at 1 mL min^–1, (ii) 0.1 mM CaCl₂ solution at 0.2 mL min^–1, and (iii) 0.1 mM CaCl₂ solution containing 10 mM citric acid at 0.2 mL min^–1. After 187 and 236 pore volumes, the flow was interrupted for 24 h and then resumed using the same influent and flow rate.