Leaching of metals from soils amended with fly ash and organic byproducts

Fly Ash (FA) is a major component of coal combustion by-products in the process of producing electricity, Increased demand for power generation caused an increase in production of FA. Most of the FA is currently land filled due to limited alternate beneficial uses. Since the cost of the landfill is increasing recently, alternate approaches for the use of Fn has received considerable attention. Fly Ash contains several nutrient elements, therefore, its application at low rates has shown benefits for various crops. There is also an interest in application of FA at high rates (disposal rates) to agricultural land, provided no negative effects on either the crop, soil or water quality call be assured. The potential benefits of FA application to agricultural soils call be further enhanced by mixing it with another by-product which can supplement some of the plant essential nutrients which are not present in the FA. Extremely sandy soils and erratically distributed high. annual rainfall in Florida contribute to leaching losses of nutrients and heavy metals from fertilizers and other soil amendments applied to agricultural soils. Leaching column (soil column of 30 cm long, 7.5 cm diameter) experiments were conducted to evaluate the leaching of metals from a fine sandy soil (Candler fine sand; sandy, hyperthermic, uncoated, Typic Quartzipsamments) amended with two sources of FA, i.e., referred to as FA-1 and FA-2, at three rates, i.e., 0.3, and 6 g FA per column, equivalent to 0, 8, and 1GMgFA ha(-1) (on area basis). Furthermore, leaching of metals through 30 cm long soil column was also evaluated when FA at 16 Mg ha(-1) rate was mixed with organic amendments such as either orange peel or compost at rate equivalent to 50 Mg ha(-1) Application of FA at 6g per column resulted inn greater concentrations of Ca, Fe, Mn, Se, Zn, and Pb ill the leachate compared to control or soil amended with 3g FA. Overall, the leachate concentrations of Fe, Cu, Se, Cr, and Pb were greater for the soil amended with FA-2 than that of FA-1. The concentrations of metals in the leachate were well below the recommended maximum contaminant levels (MCL), as per drinking water quality standards. Therefore, application of those FA sources at rates up to 16 Mgha(-1) did not appear to cause ally environmental concerns. Since most I;A contain very low levels of nitrogen (N) and phosphorus (P), supplemental application of an organic by-product with FA call be beneficial to provide most of the essential plant nutrients. Application of 50 Mg ha(-1) orange peel or compost with Fh had marginal effects on the leachability of the metals. The chelation effect of the organic amendment is beneficial to improve the plant availability of the metals and minimize leaching losses.