title: Application methods affect phosphorus-induced lead immobilization from a contaminated soil.
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 microg 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.
authors.affiliation: Soil and Water Science Department, University of Florida, Gainesville, FL 32611-0290, USA.
authors.forename: Joon Ki
authors.initials: JK
authors.lastname: Yoon
authors.forename: Xinde
authors.initials: X
authors.lastname: Cao
authors.forename: Lena Q
authors.initials: LQ
authors.lastname: Ma
mesh_terms: D007854:Lead / Q000737:chemistry*; D010710:Phosphates / Q000737:chemistry*; D010756:Phosphoric Acids / Q000737:chemistry*; D010758:Phosphorus / Q000737:chemistry; D012989:Soil Pollutants / Q000737:chemistry*; D018505:Waste Management / Q000379:methods*; D014876:Water Pollution / Q000517:prevention & control
chemical_list: D010710:Phosphates; D010756:Phosphoric Acids; D012989:Soil Pollutants; D010758:Phosphorus; D007854:Lead; C030242:phosphoric acid