Impact of ZnO nanoparticles on Cd toxicity and bioaccumulation in rice (Oryza sativa L.)
2019
Zhang, Wei | Long, Jinghua | Li, Jie | Zhang, Meng | Xiao, Guoliang | Ye, Xingyin | Chang, Wenjing | Zeng, Hui
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.
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