Alterations of lead speciation by sulfate from addition of flue gas desulfurization gypsum (FGDG) in two contaminated soils

• Published in: The Science of the total environment 2017-01, Vol.575, p.1522-1529
• Main Authors: Koralegedara, Nadeesha H., Al-Abed, Souhail R., Rodrigo, Sanjeewa K., Karna, Ranju R., Scheckel, Kirk G., Dionysiou, Dionysios D.
• Format: Article
• Language: English
• Subjects: Anglesite; Ferrihydrite bound Pb; Flue gas desulfurization gypsum; Humic acid bound Pb leadhillite; Leaching test
• ISSN: 0048-9697; 1879-1026; 1879-1026
• DOI: 10.1016/j.scitotenv.2016.10.027

This is the first study to evaluate the potential application of FGDG as an in situ Pb stabilizer in contaminated soils with two different compositions and to explain the underlying mechanisms. A smelter Pb contaminated soil (SM-soil), rich in ferrihydrite bound Pb (FH-Pb), cerussite and litharge with a total Pb content of 65,123mg/kg and an organic matter rich orchard soil (BO-soil), rich in FH-Pb and humic acid bound Pb with a total Pb content of 1532mg/kg were amended with 5% FGDG (w/w). We subjected the two soils to three leaching tests; toxicity characteristic leaching protocol (TCLP), synthetic precipitation leaching protocol (SPLP), kinetic batch leaching test (KBLT) and in-vitro bioaccessibility assay (IVBA) in order to evaluate the FGDG amendment on Pb stabilization. Solid residues of original and FGDG amended soil were analyzed using X-ray absorption spectroscopy (XAS) to identify changes in Pb speciation after each leaching test. The leachate Pb concentrations of FGDG amended soil were lower compared to those of in non-amended soil. The linear combination fitting analysis of XAS confirmed the formation of anglesite and leadhillite in FGDG amended soil. FGDG reduced the Pb desorption from ferrihydrite (FH), by forming FH-Pb-SO4 ternary complexes. FGDG decreased the Pb adsorption onto humic acid (HA) possibly due to the release of divalent cations such as Ca and Mg, which can compete with Pb to get adsorbed onto HA. The FGDG can successfully be used to remediate Pb contaminated soil. The efficiency of the treatment highly depends on the soil composition. [Display omitted] •Flue gas desulfurization gypsum (FGDG) can effectively reduce lead leaching in soil.•Anglesite and leadhillite formed in FGDG amended lead contaminated soil.•FGDG enhanced lead adsorption onto ferrihydrite.•Soil composition and leaching conditions affect the effectiveness of FGDG amendment.