Influence of Surface Charge on the Phytotoxicity, Transformation, and Translocation of CeO 2 Nanoparticles in Cucumber Plants

Mengyao Liu, Sheng Feng, Yuhui Ma, Changjian Xie, Xiao He, Yayun Ding, Junzhe Zhang, Wenhe Luo, Lirong Zheng, Dongliang Chen, Fang Yang, Zhifang Chai, Yuliang Zhao, Zhiyong Zhang

Research output: Contribution to journalArticle

4 Scopus citations

Abstract

The physiochemical properties of nanoparticles (NPs), including surface charge, will affect their uptake, transformation, translocation, and final fate in the environment. In this study, we compared the phytoxoxicity and transport behaviors of nano CeO 2 (nCeO 2 ) functionalized with positively charged (Cs-nCeO 2 ) and negatively charged (PAA-nCeO 2 ) coatings. Cucumber seedlings were hydroponically exposed to 0-1000 mg/L of Cs-nCeO 2 and PAA-nCeO 2 for 14 days and the contents, distribution, translocation, and transformation of Ce in plants were analyzed using inductively coupled plasma mass spectrometry, micro X-ray fluorescence (μ-XRF), and X-ray absorption near-edge spectroscopy (XANES), respectively. Results showed that the seedling growth and Ce contents in plant tissues were functions of exposure concentrations and surface charge. Cs-nCeO 2 was adsorbed strongly on a negatively charged root surface, which led to significantly higher Ce contents in the roots and lower translocation factors of Ce from the roots to shoots in Cs-nCeO 2 group than in PAA-nCeO 2 group. The results of μ-XRF showed that Ce elements were mainly accumulated at the root tips and lateral roots, as well as in the veins and at the edge of leaves. XANES results revealed that the proportion of Ce(III) was comparable in the plant tissues of the two groups. We speculated that Cs-nCeO 2 and PAA-nCeO 2 were partially dissolved under the effect of root exudates, releasing Ce 3+ ions as a result. Then, the Ce 3+ ions were transported upward in the form of Ce(III) complexes along the vascular bundles and eventually accumulated in the veins. The other portion of Cs-nCeO 2 and PAA-nCeO 2 entered the roots through the gap of a Casparian strip at root tips/lateral roots and was transported upward as intact NPs and finally accumulated at the edge of the blade. This study will greatly advance our information on how the properties of NPs influence their phytotoxicity, uptake, and subsequent trophic transfer in terrestrial food webs.

Original languageEnglish (US)
Pages (from-to)16905-16913
Number of pages9
JournalACS Applied Materials and Interfaces
Volume11
Issue number18
DOIs
StatePublished - May 8 2019

Keywords

  • cucumber
  • nCeO
  • phytotoxicity
  • surface charge
  • transformation
  • translocation

ASJC Scopus subject areas

  • Materials Science(all)

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