3.2. Changes in Fe/Al oxides and SOC after chemical dispersion
The removal efficiency of Fe/Al oxides after the water, oxalate, DCB,
and H2O2 treatmentswas greater in the YPF soil than that in the OPF soil
(Fig. 3). The oxalate solution removed 87.3% Feo and 73.3% Alo for the
YPF soil, and 85.3% Feo and 70.2% Alo for the OPF soil. The DCB treatment
removed 91.5% Fed and 84.7% Ald, and 85.6% Fed and 58.4% Ald for
the YPF soil and the OPF soil, respectively. A large proportion of Feo
(85.6–93.1%) and Alo (50.7–76.4%) were also removed by the DCB
for both the soils. The water and H2O2 treatments removed only 18.0–
26.2% Fe/Al for the YPF soil and 3.04–14.9% for the OPF soil. As expected,
the removal efficiency of Fe/Al oxides by water and H2O2 treatments
was significantly lower than that by oxalate and DCB treatments.
The four treatments removed SOC more efficiently in the YPF soil
than that in the OPF soil (p b 0.05). The H2O2 oxidization removed
72.1% and 61.0% of total SOC for the YPF soil and the OPF soil, respectively,
while the water, oxalate, DCB treatments removed 25.1–30% and
6.0–10.1% of total SOC for the YPF soil and the OPF soil, respectively
(Fig. 4).