The limitation of the toxicity characteristic leaching procedure for evaluating cement-based stabilised/solidified waste forms

Lead leachability in stabilized/solidified soil samples evaluated with different leaching tests

“…Both S/S-treated samples and untreated soil have a similar "U" shape concentration versus pH curve, which represents the amphoteric property of Pb solubility over a wide pH range. This observation is in agreement with previously reported results [3,6,[9][10][11][12][13]. Based on the equilibrium leachate pH, the S/S-treated material underwent three leaching stages when it contacted water: first, the high alkalinity leaching stage occurred at pH > 12, where highly alkaline materials in the treated solids increased the equilibrium pH to an extremely high level and lead was released as soluble hydroxide anion complexes.…”

“…When the concentration is below the solubility of lead oxides, Pb is directly linked to C-S-H [8]. Previous studies show that leachate pH is the major factor in controlling Pb leachability [3,6,[9][10][11]. Low Pb concentrations are observed in the neutral and basic pH range.…”

Environmental behaviour of stabilised foundry sludge

“…However, the substitution of 10% cement for foundry sand fines originates a reduction of the buffering capacity, 3.46-3.82 mequiv./g of nitric acid are necessary in all samples with FSF. In the literature it has been shown that pozzolanic agents of the cement have a negative effect on the acid neutralisation capacity with nitric acid due to the substitution of basic reagents by acidic oxides [56], in good agreement with these results. The pozzolanic behaviour of foundry sand fines has been tested in previous studies [37].…”

Preservative leaching from weathered CCA-treated wood

“…The results thus indicate that weathered CCAtreated wood might result in elevated pollutant concentrations in landfill leachates (and possible groundwater impact at unlined sites). It is important to recognize that the TCLP may be limited with respect to assessing actual leaching of wastes in operating landfills (US EPA, 1991;Cernuschi et al, 1990;Poon and Lio, 1997). Lead leaching, for example, was found to be much lower in the presence of actual landfill leachates compared to TCLP (Jang and Townsend, 2003).…”