Fig. 2. Langmuir sorption isotherms (solid lines) for NH₄⁺ in the Kennebec and Haynie soils exposed to the liquid swine waste (solid symbols) and the (NH₄)₂SO₄ solutions (open symbols). The dashed lines indicate a different stage of sorption. The initial NH₄⁺ concentrations in both solutions varied from 75 to 2085 mg NH₄⁺–N L^–1. C_e and q_e are the equilibrium concentrations of NH₄⁺ in the supernatant (mg NH₄⁺–N L^–1) and sorbed in the soils (mg NH₄⁺–N kg^–1), respectively.