3.3. Pb/Cd extractability and bioavailability
Metal mobility was closely associated with their water solubility; and metals with higher water
solubility would pose higher risk of leaching into water, then threat the organism’s health. As Table. 4
showed, the application of nHA had significantly reduced water soluble Pb with 72% reduction and Cd
with 90% reduction in contaminated soil. Reduction of water soluble Pb and Cd in the nHA treatment was
attributed to transformation of Pb/Cd from soluble Pb/Cd to insoluble.
Bioaccessible Pb/Cd in soil was determined using the PBET method (Table. 4). In the control soil,
52.4% of Pb and 69.33% of Cd on average were bioaccessible, respectively. The nHA significantly
reduced bioaccessible Pb with a reduction of 12.5-27.5% and Cd with a reduction of 17.66-34.64%,
respectively. Reduction of bioaccessible Pb/Cd may be attributed to high acidity (pH=2) in the PBET
solution which would increase further dissolution of soil heavy metals and nHA to lead more calcium
lead phosphate hydroxide formation