Wang, Xiaoxuan (2018-05). Elucidating the Effects of Cerium Oxide Nanoparticles and Zinc Oxide Nanoparticles on Arsenic Uptake by Rice (Oryza sativa) in a Hydroponic System. Master's Thesis.
Thesis
Arsenic (As) is a toxic element widely encountered in the environment and a food safety concern. The use of engineered nanoparticles (ENPs) has grown rapidly due to the unique properties that make them beneficial in a wide range of technologies. Studies abound concerning the phytotoxicity of ENPs and their accumulation in plant tissues. However, investigations on ENPs interactions with co-existing contaminants in a plant system, especially with redox sensitive heavy metals, are rare. Two ENPs of interest are cerium oxide nanoparticles (CeO2 NPs) and zinc oxide nanoparticles (ZnO NPs). The goals of this study were to: (1) determine the impact of CeO2 NPs and ZnO NPs on the As accumulation in rice, and (2) evaluate whether inorganic As species including both As(III) and As (V) may modify the plant uptake and accumulation of the metal elements of co-present CeO2 NPs and ZnO NPs. This was done by administering either 1 mg/L of As(III) or As(V), or 100 mg/L of CeO2 NPs or ZnO NPs or Zn2+, or different combinations of As and ENPs or ions at the same concentrations to rice plants. Rice (Oryza sativa) was utilized in this study as a model plant duo to its high propensity for As uptake, and its widespread consumption as a staple food around the world. A hydroponic system was used to avoid the compounding effects of soil and the microorganisms in soil. The results indicated that CeO2NPs did not show significant effect on total As plant accumulation. The presence of ZnO NPs and Zn2+ significantly reduced total As in rice seedlings, except for the concentration of total As in rice shoots with the co-presence of ZnO NPs and As(III). The co-presence of As significantly increased Ce in rice shoots in the CeO2 NPs + As(III) treatment but did not affect the plant uptake of Zn from ZnO NPs or Zn2+. The results confirmed the active interactions between ENPs and co-existing inorganic As species and the extent to which their interactions depend on the properties of ENPs as well as the initial oxidation state of As.
