Distribution of exchangeable cations and trace elements in the profiles ofsoils amended with coal combustion by-products

The flue gas desulfurization process employing forced oxidation technology generates an almost pure gypsum (FGD), which may substitute for mined gypsu m used as a soil amendment in the southeastern United States. Under specifi c conditions, a mixture of FGD and fly ash (FA) may be produced by an elect ric power plant. A field experiment was conducted to study the effect of FG D applied both singly and as a 1:1 mixture with fly ash (AFGD) on the distr ibution of the exchangeable cations Ca, Mg, K, and Al and the trace element s B, As, and Pb in the profiles of soils having various textures. Lime was not applied in this study. The experiment was conducted at three different locations near Tifton, Athens, and Calhoun, Georgia. The total amount of ra infall plus irrigation at these locations during the experimental period wa s 1385, 1419, and 1406 mm, respectively. Soil cores were collected to a dep th of 70 or 80 cm about 13 months after by-product application. FGD applica tion increased exchangeable Ca levels in the subsoil. Exchangeable K levels were significantly decreased by FGD application only in a sandy soil. FGD promoted release of Mg from the soil sorptive complex and increased leachin g of this element. Cations were transported most effectively in the profile s of a sandy soil. FA application increased plant avails able As in the sur face layer of a sandy soil and plant available B in the zone of incorporati on in the soils containing more clay, but it only partially alleviated defi ciencies of this element. FA did not sufficiently supplement K and Mg losse s induced by FGD application. The results of this study demonstrate that th e FGD material had greater agronomic value than the mixed AFGD by-product.