This study investigated the feasibility of the use of iron phosphate(vivianite)nanoparticles for long term stabilization of heavy metals,in particular copper and zinc,in sediments.The vivianite nanoparticles were synthesized in the laboratory using carboxymethyl cellulose as a stabilizer and the size of the particles was characterized to be approximately 90 – 150 nm.The effectiveness of the treatment was verified by examining nanoparticle sequestered metal leachability,bioavailability and speciation in sediments using USEPA standard methods,Toxicity Characteristic Leaching Procedure,Physiologically Based Extraction Test and Sequential Extraction Procedures.Laboratory batch experiments demonstrated that the vivianite nanoparticles are effective in reducing metal mobility in sediments as the copper concentration in nanoparticle amended sediment leachate was lower,1.2 mg/l,than the non – amended sediment leachate,4.5 mg/l,i.e.a 73%reduction; likewise,the zinc concentration in leachate reduced from 5.4 mg/l to 2.5 mg/l,i.e.a 54%reduction.Moreover,total reduction of bioavailability was 87%for Cu and 97%for Zn after nanoparticle treatment.In sediments amended with the vivianite,the copper species moved from exchangeable(EX)and carbonate(CB)bound fractions to oxides(OX)bound,organic matter(OM)bound and residual(RS)fractions.Most significantly,the copper concentration in the RS sediment increased by almost 3 times possibly due to formation of irreversible primary or secondary minerals such as pseudomalachite.The zinc species shifted from the EX and CB fractions to the less mobile OX,OM and RS phases with zinc concentration in the RS sediment also increasing by more than 3 times,due to formation of primary and secondary minerals such as parahopeite and tarbuttite.The impact of the nanoparticles and nanoparticle sequestered metal on bioactivity of plants and microorganisms also were scrutinized and results suggest that nano size vivianite can promote metabolic activity of bacterial cells.A significant increase of CFU of bacteria was observed in nanoparticle amended sediments under both aerobic and anaerobic conditions.Furthermore,Helianthus annuus and Allium tuberosum species were found to be tolerant to metal at very high concentration(1000 ppm)during nanoparticle treatment thereby can be used in combination with the vivianite as phytoremediation tools as they can remain resistant to heavy metal toxication without showing severe signs of degradation in the presence of the vivianite.