Impact of nanoparticle surface charge and phosphate on the uptake of coexisting cerium oxide nanoparticles and cadmium by soybean (Glycine max. (L.) merr.)

Engineered nanoparticles (ENPs) often interact closely with coexisting environmental pollutants; however, the effect of their surface properties on such interactions in a plant system has not been examined. This study investigated the roles of ENP surface charge and growth media chemistry on the mutual effects of cerium oxide nanoparticles (CeO2NPs) and cadmium (Cd) on their plant uptake and accumulation in a hydroponic system. Soybean seedlings were exposed to five nanoparticle/Cd treatments including: 100 mg L−1 CeO2NPs(+); 100 mg L−1 CeO2NPs(−); 100 mg L−1 CeO2NPs(+) + 1 mg L−1 Cd; 100 mg L−1 CeO2NPs(−) + 1 mg L−1 Cd; and 1 mg L−1 Cd only, in the presence or absence of 15 mg L−1 phosphorous in the form of phosphate. After 4 days of exposure, concentrations of Cd and Ce in plant tissues were quantified by inductively coupled plasma-mass spectrometry. Roots exposed to CeO2NPs(+) contained 87% higher Ce than plants exposed to CeO2NPs(−). Phosphate significantly increased the root concentration of Ce by 61% and 66% exposed to CeO2NPs(+) and CeO2NPs(−), respectively. The mutual effect of CeO2NPs and Cd was also affected by phosphate, and the net effect of phosphate depended upon the surface charge of CeO2NPs.