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This article in JEQ

  1. Vol. 36 No. 2, p. 373-378
     
    Received: Aug 11, 2006
    Published: Mar, 2007


    * Corresponding author(s): lqma@ufl.edu
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doi:10.2134/jeq2006.0316

Application Methods Affect Phosphorus-Induced Lead Immobilization from a Contaminated Soil

  1. Joon Ki Yoon,
  2. Xinde Cao and
  3. Lena Q. Ma *
  1. Soil and Water Science Dep., Univ. of Florida, Gainesville, FL 32611-0290

Abstract

Phosphate rock (PR) and phosphoric acid (PA) are an effective combination of P sources for immobilizing Pb in contaminated soils. This column experiment examined the effectiveness of different application methods on Pb immobilization in a contaminated soil. Phosphate was applied at a P/Pb molar ratio of 4 with half as PR and half PA. While PR was mixed with the soil or placed as a layer, aqueous PA was applied from the top of the column as one or two applications. After 4 wk of incubation, total and soluble Pb and P, TCLP-Pb (toxicity characteristic leaching procedure) and PBET-Pb (physiologically-based extraction test) in the P-treated soil were determined. Phosphate addition effectively reduced leachable Pb to below the EPA drinking water standard of 15 μg L−1 in all treatments. Mixing both PA and PR with the soil was the most effective method in Pb immobilization, reducing TCLP-Pb by up to 95% and PBET-Pb by 25 to 42%. Application of PR as a layer in the soil column was the most effective in reducing Pb migration (by 73–79%) and minimizing soil acidification and P entrophication, potential drawbacks of PA. Applying PA in two applications was less effective than one application. Mixing PR and PA with the soil plus placing PR as a layer can be employed for effective remediation of Pb-contaminated soils, reducing Pb leachability, bioavailability, and mobility while minimizing soil acidification and P entrophication.

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