This study evaluated the effectiveness of eggshell and calcined eggshell on lead (Pb) immobilization in a shooting range soil. Destructive and non-destructive analytical techniques were employed to determine the mechanism of Pb immobilization. The 5% additions of eggshell and calcined eggshell significantly decreased the TCLP-Pb concentration by 68.8% due mainly to increasing soil pH. Eggshell and calcined-eggshell amendments decreased the exchangeable Pb fraction to ~1% of the total Pb in the soil, while the carbonate-associated Pb fraction was increased to 40.0-47.1% at >15% application rates. The thermodynamic modeling on Pb speciation in the soil solution predicted the precipitation of Pb-hydroxide [Pb(OH) 2] in soils amended with eggshell and calcined eggshell. The SEM-EDS, XAFS and elemental dot mapping revealed that Pb in soil amended with calcined eggshell was associated with Si and Ca, and may be immobilized by entrapping into calcium-silicate-hydrate. Comparatively, in the soil amended with eggshell, Pb was immobilized via formation of Pb-hydroxide or lanarkite [Pb 2O(SO 4)]. Applications of amendments increased activities of alkaline phosphatase up to 3.7 times greater than in the control soil. The use of eggshell amendments may have potential as an integrated remediation strategy that enables Pb immobilization and soil biological restoration in shooting range soils.
Bibliographical noteFunding Information:
This study was supported by a National Research Foundation of Korea Grant funded by the Korean government (Project number: 2009-0071439). The authors thank the members of the Pohang Accelerator Laboratory (PAL), Korea and SPring-8, Japan for providing synchrotron user facilities for X-ray Absorption Fine Structure (XAFS) spectroscopy experimentation. Data of several XAFS standard spectra were provided by Dr. Masaki Takaoka (Kyoto University, Japan). The XAFS spectroscopy experimentation was conducted using a Beamline BL01B1 at the SPring-8, Hyogo, Japan, supported by the Japan Synchrotron Radiation Research Institute (JASRI) (proposal nos. 2007B1315, 2008A1265, and 2009A1255).
- Shooting range soil
- X-ray absorption fine structure
ASJC Scopus subject areas
- Environmental Engineering
- Environmental Chemistry
- Waste Management and Disposal
- Health, Toxicology and Mutagenesis