Flue-gas desulfurization gypsum effects on leaching of magnesium and potassium from a Candler fine sand

Sulfur dioxide scrubbing process in a coal-fired electric power generation plant results in production of a by-product called flue-gas desulfurization gypsum (FGDG), which contains abundance of calcium (Ca2+) and sulfate SO42-, and can be used as an amendment to agricultural soil. Effects of application of two rates FGDG (4.5 and 9.0 Mg ha(-1)) on leachate properties was compared with that of unamended Candler fine sand in leaching column experiment. The ionic strength of the leachate was five-fold greater in FGDG amended as compared to unamended treatment. The ionic strength decreased drastically after the fifth leaching. The pH of the leachate was significantly lower in FGDG amended as compared to unamended treatment. This was attributable to the "salt effect" of FGDG. The addition of FGDG significantly increased the concentrations of Ca2+ and SO42- in the leachate as compared to those from the unamended soil. The leaching of Mg2+ and K+ were also greater from FGDG amended as compared to the unamended soil. High loading of Ca2+ due to addition of FGDG appears to displace and leach other cations, such as K+ and or Mg2+, from the soil.