Citation:

Rico, C., Mark G Johnson, AND M. Marcus. Cerium oxide nanoparticles transformation at the root-soil interface of barley (Hordeum vulgare L.). Environmental Science: Nano. RSC Publishing, Cambridge, Uk, 5:1807-1812, (2018). https://doi.org/10.1039/C8EN00316E

Impact/Purpose:

Engineered nanoparticles (NPs) are being used in an increasing number of products that could lead to NPs entry into the food chain and subsequent human exposure. For example, cerium oxide nanoparticles (CeO2-NPs) are a beneficial diesel fuel additive that improves fuel combustion and reduces gaseous tailpipe emissions, but the CeO2-NPs come out of the tailpipe in aerosol form that could lead to direct crop plant exposure or deposition on crop producing soils and subsequent uptake by crop plants. The concern is that this could lead to a contaminated food supply and consequent human exposure. The transformation of cerium oxide nanoparticles (CeO2-NPs) in soil and its role in plant uptake is a critical knowledge gap in the literature. This study investigated the chemical fate of CeO2-NPs in the rhizosphere of barley (Hordeum vulgare L.) and its possible role on Ce accumulation inside the roots. Since Ce was detected in the aerial parts of barley, it was hypothesized that the behavior (i.e. speciation, transformation) of CeO2-NPs in the rhizosphere influenced the uptake of Ce in roots. Thus, this study focused on the speciation of CeO2-NPs in root-soil interface using synchrotron spectroscopy. Barley plants were cultivated in soil amended with 250 mg CeO2-NPs kg-1 soil. Synchrotron micro-X-ray fluorescence (µXRF) was used for spatial localization and speciation of CeO2-NPs in thin sections of intact barley roots at the soil-root interface. Our results showed that Ce was largely localized in soil and at the root surface in nanoparticulate form (84-89%). However, a few hot spots on root surfaces revealed highly significant chemical reduction (55-98%) of CeO2-NPs from Ce(IV) to Ce(III) species. Interestingly, only roots in close proximity to hot spots showed Ce uptake which was largely CeO2 (89-91%) with very little amount Ce(III) (9-10%). These results suggest that the reduction of CeO2-NPs to Ce(III) is needed to facilitate uptake of Ce, and that mechanism could lead to CeO2-NPs being present in food crops. This Article contributes to CSS 18.02.

Description:

The transformation of cerium oxide nanoparticles (CeO2-NPs) in soil and its role in plant uptake is a critical knowledge gap in the literature. This study investigated the reduction and speciation of CeO2-NPs in barley (Hordeum vulgare L.) cultivated in soil amended with 250 mg CeO2-NPs kg-1 soil. Synchrotron micro-X-ray fluorescence (µXRF) was employed for spatial localization and speciation of CeO2-NPs in thin sections of intact roots at the soil-root interface. Results revealed that Ce was largely localized in soil and at the root surface in nanoparticulate form (84-89%). However, a few hot spots on root surfaces revealed highly significant reduction (55-98%) of CeO2-NPs [Ce(IV)] to Ce(III) species. Interestingly, only roots in close proximity to hot spots showed Ce uptake which was largely CeO2 (89-91%) with very little amount Ce(III) (9-10%). These results suggest that the reduction of CeO2-NPs to Ce(III) is needed to facilitate uptake of Ce.

URLs/Downloads:

Record Details: