Stabilization of lead as affected by various amendments and incubation time in a calcareous soil

The effect of different kinds of amendments including coal fly ash (CFA), municipal solid waste compost (MSWC), rice husk biochars prepared at 300 degrees C (B300) and 600 degrees C (B600), zero valent iron (Fe degrees) and zero valent manganese (Mn degrees) were evaluated to determine their ability to stabilize lead (Pb) in Pb-spiked soil. The Pb-spiked soils were separately incubated with amendments at the rates of 2 and 5% (W/W) for 45 and 90days at 25 degrees C. The efficacy of amendments treatment was evaluated by desorption kinetic experiment and sequential extraction producer. According to the results, with increasing time, considerable changes in distribution of chemical forms of Pb occurred and carbonate-bound fraction significantly decreased, while amorphous Fe-bound fraction significantly increased. The applied treatments efficiently decreased the mobility factor of Pb compared to control treatment. Application of Mn degrees, Fe degrees, CFA, MSWC, and B600 in soils significantly decreased Pb desorption rate with respect to control treatment. Biphasic pattern of Pb desorption kinetic was fitted well by the model of two first-order reactions. In general, present study showed that from the practical point of view, all applied amendments (except for B300) were effective in Pb immobilization; however, application of Mn degrees at 5% (W/W) rate was the best treatment to immobilize Pb, so it can be recommended for the immobilization of Pb in calcareous polluted soil.