Alterations of lead speciation by sulfate from addition of flue gas desulfurization gypsum (FGDG) in two contaminated soils
Citation:
Koralegedara, N., S. Al-Abed, S. Rodrigo, R. Karna, K. Scheckel, AND D. Dionysiou. Alterations of lead speciation by sulfate from addition of flue gas desulfurization gypsum (FGDG) in two contaminated soils. SCIENCE OF THE TOTAL ENVIRONMENT. Elsevier BV, AMSTERDAM, Netherlands, 575:1522-1529, (2017). https://doi.org/10.1016/j.scitotenv.2016.10.027
Impact/Purpose:
Different soil amendments had been used to treat the Pb contaminated soil in the past. However, the desire for effective and inexpensive Pb remediation methods is still exists. The flue gas desulfurization gypsum (FGDG) is an industrial by-product, which is readily available and inexpensive. Due to high SO4/2- and Ca2+ content and the presence of CO3 and OH-, the FGDG can be used to form stable metal precipitates. In evaluating FGDG treatment of different Pb contaminated soils, we observed reduction in Pb leaching from two different soils with different composition. Interactions between FGDG and major soil components such as humic acid and ferrihydrite related to Pb adsorption were also discussed in this study. This is the first study that used FGDG to treat Pb contaminated soil and explained the prevailing mechanisms and effect of FGDG amendments on Pb sorption characteristics of humic acid and ferrihydrite in soil. This study relates to the government agencies examining lead contaminated soil remediation options and the FGDG industry.
Description:
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 65,123 mg/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 1532 mg/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 lowered compared to those of non-amended soil. The linear combination fitting analysis of XAS confirmed the formation of anglesite and leadhillite in FGDG amended in 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.
URLs/Downloads:
DOI: Alterations of lead speciation by sulfate from addition of flue gas desulfurization gypsum (FGDG) in two contaminated soils
http://dx.doi.org/10.1016/j.scitotenv.2016.10.027
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