Bonemeal additions as a remediation treatment for metal contaminated soil

Abstract

The ability of bonemeal additions (finely ground, poorly crystalline apatite, [Ca10(PO4)6OH2]) to immobilize pollutant metals in soils and reduce metal bioavailability through the formation of metal phosphates has been evaluated. Leaching column experiments were carried out on contaminated soils with pH varying between 2.7 and 7.1. Monitoring of leachates over a three month period indicated that bonemeal additions resulted in the immobilization of metals and an increase in the pH of the column leachate, the soil pore water and the soils themselves. Analytical scanning electron microscopy of the bonemeal treated soil at the end of the experiment revealed that Pb and Zn were associated with phosphorus. X-ray diffraction identified several newly formed phases in the bonemeal treated soil at the end of the experiments that had peaks of similar intensity and positions as reference Pb and Ca-Zn phosphates. Batch experiments and subsequent extraction of metals from controls and bonemeal amended soils using 0.01 M CaCl2 and DTPA indicated that bonemeal additions reduced the availability of the metals in the soils. Bonemeal amendments appear to have potential as a remediation treatment for metal contaminated soils.