This study’s aim was to evaluate whether cerium oxide (CeO2) nanoparticles (NPs), present in the environment as contaminants, pose a risk to agricultural crops. It has been estimated that, as of 2017, CeO2 concentrations soils globally can be as high as 0.062 mg kg-1 for agricultural soils, and 0.93 mg kg-1 for sludge treated soils. This study this investigated the effects of such concentrations, as a worst-case scenario, on the development and grain yield of soybean plants. A hydroponic system was used, and it was assumed that all NPs (25 nm) at these concentrations are available for plant uptake. A soluble source of cerium (Ce(NO3)3.6H2O) was also tested for comparison. Two advanced techniques, namely single-particle inductively coupled plasma mass spectrometry (SP-ICP-MS) and microprobe X-ray fluorescence spectroscopy (μ-XRF), were used to quantitatively track cerium uptake by the plants, from roots to shoots and to grain. It was thus possible to verify the translocation of cerium of both soluble and nanoparticulate forms, and determine cerium chemical speciation. In both scenarios, appreciable amounts of cerium were detected in the soybean roots epidermis and cortex, leaves, and grains. At the measured concentrations of uptake, cerium did not impair the plant’s development (height, number of leaves, chlorophyll content) nor its grain yield (number of pods and seeds, and seed dry mass). Given that the cerium concentration in biomass remained approximately constant during the four-week plant growth cycle (0.13 to 0.17 mg kg-1 in leaves) when exposing plants to NPs, it was concluded that NP uptake occurs at the same rate as biomass growth, and thus is carried into the plants via water uptake. This is in contrast to the increasing cerium concentration in biomass over time (0.39 to 3.60 mg kg-1 in leaves) for plants exposed to soluble cerium. Clusters of CeO2 NPs were detected by SP-ICP-MS analysis in leaves of plants exposed to the NPs, most ranging from 30 to 45 nm in size, while reprecipitation of soluble cerium as NPs within the plants was not observed. As some bioconcentration factors calculated for the various trials were above one, and since soybean is commonly used as livestock feed, it is important to evaluate the possibility for cerium biomagnification in the food chain.

Uptake and accumulation of cerium oxide nanoparticles, as environmental contaminants, by soybean plants

ACS Spring Meeting 2021

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