Wet/dry cycling effects on soil contaminant stabilization with apatite and Fe(0)

Efficacy of stabilizing Ce, Co, and Pb by adding apatite and zero-valent Fe(Fe(0)) to contaminated wetland sediments was quantified under oxidizing and reducing conditions. The redox status and the general water chemistry of the oxidized and reduced treatments differed greatly, yet the influences of the amendments on contaminant stabilization were quite similar; both amendments significantly (p <= 0.05) reduced aqueous contaminant concentrations. Based on resin sorption studies and thermodynamic calculations, Ce is believed to exist primarily as cationic species and Co as cationic, neutral, and organically complexed species. Based on a series of selective extractions. almost 50% by weight of the Co and Pb were already strongly bound to the sediment, thereby limiting the potential (and need) of affecting additional immobilization through the use of amendments. Fe(0) and combined Fe(0) and apatite additions tended to increase the in situ desorption K-d values more than apatite-only additions.