In this study,we examined the effect of nanoparticles(Al2O3 and TiO2) on kinetics release,fractionation and speciation of phosphorus(P) in somecalcareous soils of western Iran.The maximum (average of five soils) (40.3 mgkg−1) and the minimum(10.5 mgkg−1) P were released by control soils and soils plus3% TiO2, respectively.Pseudosecond-ordermodeldescribedwellPrelease.Inordertopredictandmodel the effects of NPs on P release,surface complexation modelinPHREEQC program was used.The model could simulate the P release very well in allsoils.AfterPrelease,the percentage of organic matterand sulphide-P fraction increased markedly following NPs addition,while carbonated-P fraction remained the mostdominantfractioninallsoils.IntheinitialstageofPreleasethesolutionsamplesinallsoilsand treatments were saturated with respect to strengite,andunder saturated with respecttootherphosphate minerals. Attheend of P release,allsolutions were saturatedwithrespecttohydroxyapatiteandstrengite and undersaturatedwithrespecttootherphosphateminerals.TheseresultsreflectedthattheNPscaused immobilization of P in soils and reduced the bioavailable P,thus,reducing their environment risk.
