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The use of high-sulfur coal for power generation in the United States requires the removal of sulfur dioxide (SO2) produced during burning in order to meet clean air regulations. If SO2 is removed from the flue gas using a wet scrubber without forced air oxidation, much of the S product created will be sulfite (SO3 2- ). Plants only take up S in the form of sulfate (SO4 2- ), and SO3 2- is toxic to plants and may cause damage to plant roots. For agricultural uses, SO3 2- in flue gas desulfurization (FGD) products must oxidize to SO4 2- in soils before crops are planted. However, there is little information about the oxidation of SO3 2- in FGD product to SO4 2- under field conditions. An FGDCaSO3 obtained from American Electric Power Company was applied at rates of 0, 1.12 and 3.36 Mg ha -1 to the surface of an agricultural soil (Wooster silt loam, Oxyaquic Fragiudalf). The SO4 2- in the surface soil (0-10 cm) was analyzed on days 3, 7, 17, 45, and 61. The distribution of SO4 2- and Ca in the 0-90 cm soil layer was also determined on day 61. Results indicated that SO3 2- in the FGD-CaSO3 rapidly oxidized to SO4 2- on the field surface during the first week and much of SO4 2- and Ca moved downward into the 0-50 cm soil layer during the experimental period of two months. It is safe for plants if FGD-CaSO3 is applied to the field surface one month before planting. However, application too long before planting might cause some of the S and Ca for plant uptake to be lost due to leaching or other soil processes. |
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