Effect Of Aging Time Of TiO₂and CeO₂Engineered Nanoparticles In Soil On Growth Of High Plant

Engineered nanoparticles (ENPs) have many unique physicochemicalcharacteristics, such as surface effect, optical property, quantum size effect,macroscopic quantum tunneling effect and catalytic performance and so on. TheENPs are widely used in electronics, cosmetics, biological medicine, catalyst, materialscience and environmental remediation, which induce inevitably the release of ENPsinto the environment, especially into soil through many different pathways, thuscausing phytotoxicity to high plants in soil. As the primary producer in terrestrialecosystem and one of the most important agricultural and industrial crops, maize is ofthe vital importance to stability of the whole terrestrial ecosystem and food safety ofthe human world. Engineered titanium oxide and cerium oxdie nanoparticles (TiO2ENPs, CeO2ENPs) have been extensively used in cosmetics, food, catalyst andsemiconductor. Their toxicity research has caused much attention and been one of themain research targets of ENPs toxicity. This study used maize (Zea mays L.) as thetested high plant and compared the effect of aging time of TiO2ENPs and CeO2ENPsin soil on growth of maize seedlings. The results are summarized as followings:(1) Effect of TiO2ENPs on maize seedlings height, shoot and root fresh and dryweight, root length and root surface have basicly the same regularity at differenttime. TiO2ENPs was more toxic than TiO2BPs and1000mg/kg concentration ofTiO2ENPs was more toxic than2000mg/kg concentration of TiO2ENPs. TiO2ENPs could induce the generation of H2O2and cause oxidative stress to maizeseedlings. Toxicity of TiO2ENPs was higher before60d and lower after60d.(2) TiO2ENPs could be taken in maize seedlings and transport from root to shoot.The bioaccumulation coefficient of1000mg/kg concentration of TiO2ENPs inmaize seedling root was35.4%and13.6%in shoot. The transfer coefficient inmaize seedlings was0.38.(3) Ti concentration in rhizosphere and non-rhizosphere of maize seedlings was basically the same at aging0d and120d. However, Ti concentration was higher inrhizosphere than in non-rhizosphere at aging30d,60d and90d, which meansmaize seedlings rhizosphere could affect the bioavailability of TiO2ENPs.(4) Effect of CeO2ENPs on maize seedlings height, shoot and root fresh and dryweight, root length and root surface are has basicly the same regularity atdifferent time. CeO2ENPs have more toxicity than CeO2BPs and500mg/kgconcentration of CeO2ENPs have more toxicity than1000mg/kg concentration ofCeO2ENPs. CeO2ENPs could induce the generation of H2O2and cause oxidativestress to inhibit growth of maize seedlings. Toxicity of CeO2ENPs was higherduring aging time and lower after60d.(5) CeO2ENPs could be uptaken in maiz seedlings as well and transport from root toshoot. The bioaccumulation coefficient of500mg/kg concentration of CeO2ENPsin maize seedling root was57.1%and14.4%in shoot. The transfer coefficientwas0.24.(6) Ce concentration in in rhizosphere and non-rhizosphere of maize seedlings wasbasically the same at aging0d and120d. However, Ce concentration was higherin rhizosphere than in non-rhizosphere at aging30d,60d and90d, which meansmaize seedlings rhizosphere could affect the bioavailability of CeO2ENPs asTiO2ENPs.(7) The morphological structure of maize seedling root has changed after exposed toTiO2ENPs and CeO2ENPs. The root cap has been longer and the elongzationzone cells have elongated. After observed by TEM, the TiO2ENPs and CeO2ENPs could exist in cytoplasm and cell nucleus of root cells and vacuoles and cellnucleus of leaf cells, which also need to be verified by EDS in the further study.