Impact of ZnO nanoparticles on Cd toxicity and bioaccumulation in rice (Oryza sativa L.)
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With the widespread use of metal oxide nanoparticles (MNPs), agricultural soil is gradually becoming a primary sink for MNPs. The effect of these nanoparticles on the fate and the toxicity of co-existing heavy metals is largely unknown. In this paper, pot experiments were conducted to evaluate the impact of ZnO nanoparticles (ZnO-NPs) on Cd toxicity and bioaccumulation in a soil-rice system. Different amounts of ZnO-NPs were added to three different levels of Cd-contaminated paddy soil (L-Cd, 1.0 mg kg−1; M-Cd, 2.5 mg kg−1; H-Cd, 5.0 mg kg−1). The results showed that the addition of ZnO-NPs significantly increased the soil pH value, and the soil pH value increased with the increase in ZnO-NP concentration. Reductions in plant height and biomass under Cd stress were recovered and increased after the addition of ZnO-NPs; the addition of ZnO-NP promoted rice biomass increased by 13~22% and 25~43% in the M-Cd and H-Cd groups, respectively, compared with that of the respective control treatment. A high concentration of ZnO-NPs could increase the concentration of bioavailable Cd in rhizosphere soil. In the L-Cd group, the Cd concentration of the rice in the L-Z500 treatment increased to 0.51 mg kg−1, exceeding the limit for acceptable Cd concentrations in rice of China (0.2 mg kg−1). This work revealed that ZnO-NPs could improve plant growth, especially in the early-growth stage, and alleviate the toxic effects of Cd. However, the addition of high-concentration (500 mg kg−1) ZnO-NPs in the lower Cd pollution soil could significantly facilitate the accumulation of Cd by Oryza sativa L.
KeywordsZnO nanoparticles Cd Bioaccumulation Migration Bioavailability
This study is financially supported by the Foundation for Innovative Research Groups of the National Natural Science Foundation of China (31621091) and the General Financial Grant from the China Postdoctoral Science Foundation (2017M620504).
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Conflict of interest
The authors declare that they have no conflict of interest.
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