Band application of flue gas desulfurization gypsum improves sodic soils
Blending FGD gypsum with surface sodic soil is a universally recognized
method for the rapid amelioration of sodic soils; however, there are few
reports on whether other application methods (band application) will
reclaim sodic soil. Three FGD gypsum application methods, single-band
application, dual-band application and blending, were carried out using
sodic soil in soil bins to investigate the effects of application method
on the wetting front, major cation concentrations and ESP during the
process of water infiltration and in the soil profile after
infiltration. The results showed that the wetting fronts in the band
treatments were denser in the horizontal direction than in the vertical
direction, but the blend treatment only had vertical migration. There
was an exponential relationship between time and depth of penetration.
The orders of desalting capacity were blend treatment, dual-band
treatment and single-band treatment for the same volume of outlet water.
Na+ was the primary ion in the leachate. The main channel in the band
treatments was concentrated below the application site of FGD gypsum.
The dual-band treatment significantly decreased the soil ESP of the
whole soil bin, while the single-band treatment only effectively
reclaimed half of the soil. In the blend treatment, the ESP was 21.32%
and 34.66% at depths of 30–35 cm and 35–40 cm and was close to zero
at a depth of 0–30 cm. Compared with blend treatment, band treatments
have the advantage of long-term amelioration of local sodic soil, and
the performance is mainly affected by the Ca2+ pathway.