Synchronous stabilization of multi-metal in Pb/Zn smelter-contaminated soil by dithiocarbamate

The escalating severity of soil heavy metals (HMs) pollution from ongoing Pb/Zn smelting presents significant challenges. Compared with traditional stabilizers, dithiocarbamate (DTC) has been proven to have unique advantages for multi-metal stabilization in municipal solid waste incineration fly ash. In this study, we evaluated the feasibility of applying DTC for multi-metal synchronous stabilization in Pb/Zn smelter-contaminated soil, and utilized a machine learning (ML) approach to identify the dominant factors affecting the stabilization of Cd, Pb and Zn. After stabilization, the bioavailability of Cd, Pb and Zn decreased over 49.94 %. For the leaching toxicity, it was under 57.04 %. In terms of bioavailability stabilization efficiency, the order is Pb (91.68 %) > Cd (67.06 %) > Zn (49.94 %); for leaching toxicity stabilization efficiency, it is Cd (57.04 %) > Pb (52.51 %) > Zn (16.99 %). The ions of the HMs bind with the ionized organic ions (such as CH3+) of the DTC, resulting in the formation of chelate precipitates that pose less risk to the environment. The contribution rates of influence factors are as followed: stabilizer application rate (SAR) > soil moisture (SM) > types of stabilizers > soil particle size, while SAR has the strongest interaction with SM.