Tuesday, November 6, 2007
227-3

Phosphorus-Induced Lead Immobilization in a Shooting Range Soil Using Poorly-Crystalline Hydroxyapatite and Incinerated Poultry Waste.

Yohey Hashimoto, Takatoshi Yoshida, and Takeshi Sato. Department of Civil Engineering, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan

Chemical immobilization of Pb contaminated soils using P-containing amendments is a promising technology to reduce contaminant solubility. The objectives of this study were to assess immobilization effects of various P-containing amendments on Pb in a contaminated soil, and to determine possible mineralogical Pb species. A Pb-contaminated soil (18000 mg kg-1) collected from a shooting range in central Japan was amended with different P materials including hydroxyapatite (HA), laboratory synthesized poorly-crystalline hydroxyapatite (CHA), incinerated poultry waste (PW), and calcium phosphate (CP). The amount of amendments added in the soil was determined based on the molar ratio of P/Pb at a 6/5 ratio, which corresponds to 2 times the amount of soil Pb to form pyromorphite. Soils were incubated for up to 12 weeks at 50% of saturation level. After 12-week incubation, water extractable Pb was most reduced by CHA to below 0.01 mg L-1, followed by PW, CP, HA and control treatments. Concentration of soil Pb extracted by Toxicity Characteristics Leaching Procedure (TCLP) was the smallest in the PW and CP treatments (< 100 mg L-1), followed by CHA, HA and control treatments. The XRD analysis detected that the CHA and PW treatments had smaller peaks of cerussite (PbCO3) and pyromorphite peaks were exhibited, indicating that soil Pb may be transformed into less soluble Pb species.

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