Fig. 3. Effect of immobilization treatments on Zn extractability in Blackwell (BW), Henryetta (H12), and Bartlesville (B4) contaminated soils as determined by the PBASE sequential extraction. Immobilization treatment abbreviations are the same as listed in Fig. 2. Zn x 5 designation indicates the E1 values have been multiplied by 5. Treatments with the same letter are not different at P < 0.05 within each soil–extract combination.