Effects of Two Metal Oxide Nanoparticles on Soil Cultivated Soybean (Glycine max)

Orateur : Jose Angel HERNANDEZ-VIEZCAS (University of Texas at el Paso)

Due to the increased production and use of manufactured nanomaterials (MNM) there is concern about their unavoidable release into the environment. MNM environmental buildup could profoundly alter soil-based food crop quality and yield. Few reports thus far have addressed the entire life cycle of plants grown in MNM-contaminated soil. Soybean (Glycine max) seeds were germinated and grown to full maturity in organic farm soil amended with either of two high-production metal oxide MNMs (ZnO or CeO2). At harvest, synchrotron microXRF and microXANES analyses were performed on soybean tissues, including pods, to determine the forms of Ce and Zn in MNM-treated plants. The X-ray absorption spectroscopy studies showed no presence of ZnO within tissues. However, microXANES data showed O-bound Zn, in a form resembling Zn-citrate, which could be an important Zn complex in the soybean grains. On the other hand, the synchrotron microXANES results showed that Ce remained mostly as CeO2 within the plant. The data also showed that a small percentage of Ce (IV), the oxidation state of Ce in CeO2 MNM, was biotransformed to Ce(III). Plant growth and yield diminished, but also nitrogen fixation, a major ecosystem service of leguminous crops, was shut down at high CeO2 MNM concentration. Juxtaposed against widespread land application of wastewater treatment biosolids to food crops, these findings forewarn of agriculturally associated human and environmental risks from the accelerating use of MNMs.

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