Phosphate Treatment of Firing Range Soils: Lead Fixation or Phosphorus Release?
- 1 January 2008
- journal article
- Published by Wiley in Journal of Environmental Quality
- Vol. 37 (1), 47-56
- https://doi.org/10.2134/jeq2007.0151
Abstract
Phosphate treatment of lead (Pb)-contaminated soils relies on the premise that Pb converts to the thermodynamically stable, insoluble mineral class of pyromorphites. Recent research showed that treatment performance is kinetically controlled and strongly dependent on soil pH; this study employed an acidic phosphate (P) form, monobasic calcium phosphate (MCP), to investigate treatment performance of Pb occurring in an alkaline-buffered and an acidic firing range soil. The results of leaching, X-ray powder diffraction (XRPD), and modeling analyses showed that P and Pb dissolution in the alkaline soil and transformation reactions were kinetically controlled, so that: (i) TCLP (toxicity characteristic leaching procedure) and SPLP (synthetic precipitation leaching procedure) results were poor to marginal even at high MCP dosages; (ii) brushite (Ca(HPO4)·2H2O) and cerussite (PbCO3) persisted in XRPD patterns; and, (iii) geochemical modeling failed to predict leaching and phase assemblages. In the acidic soil, Pb-P reactions promoted further soil acidification, improved TCLP performance, and generated better agreement with the equilibrium-based model; however, SPLP and modeling results showed that Pb concentrations could not be reduced below 15 μg/L mainly due to the low soil pH. The marginal or inadequate Pb immobilization was observed in both soils despite the elevated MCP dosages, which were well in excess of the pyromorphite stoichiometric ratio (P/Pb = 0.6). Additionally, P leaching concentrations and rates were extremely high (>300 mg/L), under both SPLP and deionized (DI) water extraction conditions, and as predicted by thermodynamic equilibrium. The performance and sustainability of phosphate-based treatment therefore seem questionable. Copyright © 2008. American Society of Agronomy, Crop Science Society of America, Soil Science Society . American Society of Agronomy, Crop Science Society of America, and Soil Science Society of AmericaKeywords
Funding Information
- U.S. Army
This publication has 16 references indexed in Scilit:
- Phosphate application to firing range soils for Pb immobilization: The unclear role of phosphateJournal of Hazardous Materials, 2007
- Lead particle size and its association with firing conditions and range maintenance: implications for treatmentEnvironmental Geochemistry and Health, 2007
- An Apatite II permeable reactive barrier to remediate groundwater containing Zn, Pb and CdApplied Geochemistry, 2006
- Pb speciation versus TCLP release in army firing range soilsJournal of Hazardous Materials, 2006
- Stepwise Rock-Eval pyrolysis as a tool for typing heterogeneous organic matter in soilsJournal of Analytical and Applied Pyrolysis, 2005
- Qualitative and quantitative speciation analysis of water soluble selenium in three edible wild mushrooms species by liquid chromatography using post-column isotope dilution ICP–MSAnalytica Chimica Acta, 2005
- Evaluation of chemical immobilization treatments for reducing heavy metal transport in a smelter-contaminated soilEnvironmental Pollution, 2004
- Utilization of fly ash for stabilization/solidification of heavy metal contaminated soilsEngineering Geology, 2003
- Impacts of Phosphate Amendments on Lead Biogeochemistry at a Contaminated SiteEnvironmental Science & Technology, 2002
- Stabilization/Solidification (S/S) of Heavy Metal Contaminated Soils by Means of a Quicklime-Based Treatment ApproachPublished by ASTM International ,1996