A field‐based experiment was set up to evaluate the effectiveness of a single application
of marble waste sludge (MWS) on chemical immobilization of potentially hazardous trace elements
(PHE) within the soil profile of a mine Technosol under natural assisted remediation for 12 years.
Results showed that MWS amendment significantly reduced soil acidity and PHE mobility com‐
pared to unamended soil, thus improving soil health and plant growth. The amendment applica‐
tion had a sustained acid‐neutralizing action, as soil pH remains relatively constant at between 5.8
and 6.4 throughout the entire profile (70 cm depth). In addition to diluting pollutants, the treat‐
ment triggered a redistribution of trace elements among the various operationally defined geo‐
chemical pools, shifting the PHE speciation from water‐soluble forms to fractions associated with
carbonates (29% Cd), metal oxides (40–48% Zn, Cd, Cu, and Ni), organic matter (22% Cu and Ni),
and insoluble secondary oxidation minerals and residual phases (80–99% As, Cr, Sb, Tl, and Pb),
thereby effectively limiting its potential environmental significance. MWS treatment to immobilize
PHE in the contaminated mine Technosol was effective and persistent while in the untreated soil
metal release is continuing over time