REMEDIATION OF SOIL POLLUTED WITH INDUSTRIAL· WASTES USING AN IMMOBILIZATION TECHNIQUE. | ||||
| Journal of Soil Sciences and Agricultural Engineering | ||||
| Article 9, Volume 29, Issue 8, August 2004, Page 4833-4843 PDF (2.99 MB) | ||||
| Document Type: Original Article | ||||
| DOI: 10.21608/jssae.2004.242541 | ||||
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| Author | ||||
| S. A. Z. EI-Gendi | ||||
| Soils, water and Environment Research Institute, Agricultural Research Centre, Giza ,Egypt | ||||
| Abstract | ||||
| The current study was designed to test the potential of diammonium phosphate (DAP) in immobilizing Pb and Zn in an industrial contaminated soil. Four phosphate treatments including various ratios of added P to total heavy metals content corresponding to stoichiometric P to Pb ratio of chloropyromorphite mineral were tested. The obtained results revealed that the total contents of Pb and Zn in the topsoil were above the maximum acceptable concentrations (MAC) that reported by USEPA- 503 regulations. In the tested soils ,the data referred that the sequential extraction procedure employed in this study appeared to be useful for classifying Pb and Zn within six geochemical fractions. The fractionation studies indicated that Fe &Mn oxide fraction proved to be the most abundant for Pb (more than 41% of total Pb) , whereas the residual form was the dominant for Zn (37%) . The sum of the relative soluble pools implies that a great portion of these metals may be highly bioavailable . Amending the soil with DAP converted the relative soluble pools into more stable pools. Zn was distributed in the order; residual »oxide>carbonate>organic>exchangeable > water- soluble. While the order for Pb was residual = oxide >organic >carbonate > exchangeable >water -soluble. On an average basis, the mobility indexes of Pb and Zn decreased from 20.1 to 11.10 and from 28.2 to 15.44 in the untreated and phosphate- treated soil , respectively. The concentrations of the active portion of Pb and Zn ,expressed as minus logarithm of ML·1 (RC) sharply decreased as a result of soluble phosphorous amending. The pC of Pb2+ decreased from 10.23 to 11.23 and from 7.59 to 7.75 for Zn2+ , suggesting that DAP has potential to immobilize Pb and Zn in industrial contaminated soil. The results of solubility diagrams of lead-phosphate minerals suggested that choropyromorphite mineral in equilibrium with either DAP or DCPD has been recognized as a mineral controlling Pb solubility untreated (contaminated) and treated soil solutions, respectively. Also, the results of solubility diagrams of Zn suggested that Zn -soil regulate the solubility of Zn in all the tested soil solutions. | ||||
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