Assessment of immobilisation and biological availability of iron phosphate nanoparticle-treated metals in wetland sediments

A study was carried out to investigate the feasibility of use of iron phosphate (vivianite) nanoparticles for long-term stabilisation of heavy metals, in particular copper and zinc, in wetland sediments. The effectiveness of the treatment was examined by assessing nanoparticle sequestered metal leachability, bioavailability and speciation in sediments using USEPA standard methods: a toxicity characteristic leaching procedure (TCLP), a physiologically based extraction test (PBET) and a sequential extraction procedure (SEP). The impact of the nanoparticles and nanoparticle sequestered metal on bioactivity of plants and bacterial growth was also investigated. Inhibition of microbial growth was reduced in sediments treated with the nanoparticle preparation, and a bioaccumulating capacity was found for selected plants at high concentrations (1,000 ppm) of Cu and Zn, in the presence of nanoparticles. This finding suggests that metal bioavailability may have been reduced for microbial populations in nanoparticle-treated microcosms; however, the bioaccumulation finding suggests that select plant species could be used in combination with the vivianite as phytoremediation tools.