Friday, October 3, 2008: 10:00 a.m.
Reclaimed soils may be a source of metals into groundwater due to unweathered spoil material or biosolid application, while mobile colloids within soil systems can be carriers of these contaminants. A recently reclaimed site following coal mining in eastern Kentucky was chosen to observe mobilization and transport of Zn associated with colloidal material. Monoliths representing recent reclamation were packed in the lab from materials retrieved on site, using both soil and spoil materials. Monoliths representing undisturbed (natural) forest soils were also sampled for comparison. Biosolids were added to an additional reclaimed monolith treatment at a rate of 20 T/Acre. Leaching experiments with de-ionized water at a rate of 1.0 cm/h involved 6 cycles of 8 hours each, giving each monolith at least 2 pore volumes of leaching. Colloid elution was highest in natural monoliths, followed by reclaimed monoliths, and reclaimed monoliths receiving biosolid application. Reclaimed monoliths with unweathered spoil material eluted no detectable colloids due to high ionic strength and low clay content. Following oven drying at 60ºC, both natural and reclaimed monoliths eluted additional colloids, although they had lower total colloid mass following the drying period. Water retention was lower in the disturbed reclaimed monoliths versus the natural forest soils, due to the disturbance in pore structure. Both Zn and Cu were mobile in solution and colloid phases, with colloid transport increasing the mobility of Zn by 1 to 12% and Cu by 8 to 81%.