Wet-dry (W-D) cycles will cause the release of toxic Cr(VI) from stabilized/solidified soils, posing a threat to the surroundings. In this research, Cr(VI)-contaminated soil treated by alkali-activated granulated blast furnace slag (GGBS) was studied. Through accelerated leaching tests and Cr spatial distribution analysis, the effects of W-D cycle and rainfall pH on Cr mobility in the solidified soil were investigated. The mechanisms of Cr release were studied by chemical form analysis and a serious of micro analyses. The results showed that the leaching characteristics varied with W-D cycles and pH. Under a neutral pH, the cumulative leaching concentration of Cr decreased after 3 W-D cycles and then increased, and the leaching mechanism transitioned from surface wash-off to dissolution. Under acidic environments, the leaching concentration increased by 1-2 orders of magnitude along with the decomposition of hydration products. During the W-D cycles, Cr(VI) content in the solidified soil decreased from top to bottom, reflecting the top-down process of degradation, release, and migration. The W-D cycles had no obvious influence on valence state of Cr. After acidic W-D cycles, the fraction of soluble state Cr(VI) and adsorbed Cr(VI) increased significantly. The CrO4-jarosite phase exhibited good chemical stability in acidic conditions, indicating that chemical substitution is an important immobilization mechanism of Cr(VI). The microscopic morphology analysis showed that W-D cycle caused irreversible damage to the microstructure, and that in an acidic condition C-A-S-H gels were more stable than Aft and C-S-H gels. Along with the W-D cycles, the proportion of macropores increased and the interlayer/gel pores became larger, which significantly facilitated the release of Cr(VI).

来源平台：JOURNAL OF CLEANER PRODUCTION