Fig. 8. Simulated exchange isotherms (solid circles; upper line) for N₂H⁺₅ for Arredondo Ap soil calculated from binary exchange selectivity coefficients used in transport simulations. A sorption isotherm (open circles; lower line) that includes both ion exchange and N₂H⁺₅ chemisorption was obtained by dividing the sorbed phase concentration by S_T rather than S_Tef. The terms C_o and C_e represent initial and final N₂H⁺₅ concentrations in the solution phase.