Fig. 2. PAM sorption isotherms by the six test soils under various salt concentrations. PAM solutions were prepared in: (i) • DI (deionized) water; (ii) 0.002 M NaCl; (iii) 0.010 M NaCl; (iv) 0.001 M CaCl₂; and (v) 0.005 M CaCl₂. Each data point is the mean of two replicates and error bar is its average deviation. Solid line is fitted Langmuir sorption isotherm.