Toxicity and biotransformation of nanoparticles on Terrestial plants: The case of Ni(OH)2 , ZnO and CeO2 Nanoparticles

Nanomaterials are of particular interest in environmental chemistry due to their unknown toxicity to living organisms. Reports indicate that nanoparticles (NPs) affect seed germination, but the uptake and biotransformation of metal nanoparticles is not well understood. This study investigated the toxicity and biotransformation of Ni(OH)2 NPs by mesquite plants (Prosopis sp.). Three sets of plants were treated for four weeks with 0.01, 0.05 or 0.10 g of either uncoated or sodium citrate coated NPs before and after production. Nickel concentrations in plants were determined by inductively coupled plasma-optical emission spectroscopy (ICP-OES) and the form and oxidation 99099had an average size of 8.7 nm; while coated NPs before and after production had an average 2.5 and 0.9 nm, respectively. The ICP-OES results showed that plants treated with 0.10 g of uncoated and coated NPs before and after production had 803, 764, and 400 mg Ni kg d wt, in leaves, respectively. The XAS analyses showed Ni NPs in roots and shoots of plants treated with uncoated NPs, while leaves showed a Ni(II)-organic acid type complex. However, plants treated with coated NPs before or after production showed Ni NPs only in roots and a Ni(II)-organic acid complex in stems and leaves. Results also showed that none of the treatments reduced plant size or chlorophyll production. To the authors' knowledge, this is the first time that the biotransformation of nanoparticles by a plant system is reported. We will also show some preliminary results on the biotransformation of ZnO and CeO2 nanoparticles on soybean plants.