Fig. 1. Observed (discrete points) N₂H⁺₅ and Ca²⁺ breakthrough curves (BTCs) in effluent from an Arredondo Ap soil column injected with a pulse of high hydrazinium concentration (22.15 mol_c m^-3). Simulated BTCs with (smooth lines) and without chemisorption (broken lines) of exchange-phase N₂H⁺₅ are given.