Fig. 4. The amount of 2,4-D adsorbed on untreated UG5 soil (•), UG5-SOM (
), UG5-SOM-AM (
), and UG5-SOM-FM (
) in the presence of 0.01 M CaCl2 as a function of equilibrium pH. Reaction time, 4 h; initial 2,4-D concentration, 22.6 µM (5.0 mg L–1); the amount of soil, 50 g L–1 (oven-dried and untreated soil basis). Had the soil adsorbed all 2,4-D in this experiment, the amount of 2,4-D adsorption would have reached 0.452 mmol kg–1.