THE EFFECTS OF MICRO- AND NANOHYDROXYAPATITE APPLICATION IN METAL CONTAMINATED SOIL ON METAL ACCCUMULATION IN IPOMOEA AQUATICA AND SOIL METAL BIOAVAILABILITY

The potential of microhydroxyapatite (MHA) and nanohydroxyapatite (NHA) to immobilise heavy metals in a 25-year old active firing range soil was investigated. The effects of immobilisation were evaluated in terms of metal accumulation in water spinach (Ipomoea aquatica) and soil metal bioavailability. A pot trial was conducted by amending firing range soil with MHA and NHA at application rates of 0%, 1% and 3% (w/w). Both amendments increased biomass yield and reduced plant metal uptake. The bioconcentration factor (BCF) values of the metals were in the order of Zn > Cu > Pb. The bioavailable fraction of Cu, Pb and Zn in firing range soil decreased significantly (p < 0.05) following MHA and NHA treatments. No toxicity symptoms were observed in water spinach over the pot trial. Therefore, MHA and NHA are two promising immobilising agents for the remediation of metal contaminated land