Stabilization of Heavy Metal-Contaminated Sediment with a Chelator and Humic Acid Mixture

A chelator, potassium dipropyl dithiophosphate, and humic acid were combined and used as a stabilizing agent to study the stabilization effect of the mixture on heavy metals in a contaminated sediment. The results indicated that the stabilization efficiencies for Cu, Zn, Pb, and Cd in the sediment were up to 99.98, 90.66, 99.38, and 92.83%, respectively, and the unstable Cu, Zn, Pb, and Cd fractions fell by 57.11, 54.74, 56.41, and 89.14%, respectively, when 5% potassium dipropyl dithiophosphate and 7% humic acid were added. This significantly reduced the bioavailability of the heavy metals. Under leaching caused by simulated acid rain (pH 3 and pH 5), the heavy metals mainly migrated from the solid phase to the liquid phase during the initial leaching period, and the Pb, Cu, Zn, and Cd leaching rates in the sediment after stabilization fell by 55–99%. Cu showed the greatest reduction. When the results for the sediment after stabilization were compared with the sediment before stabilization, the wheat stem height had increased by 53.62%, the dry weights of the leaves and roots increased by 86.25 and 34.85%, respectively, and Cu, Zn, Pb, and Cd enrichment in the wheat roots and leaves fell by 40–88 and 73–95%, respectively.