玉米对纳米TiO_2的吸收和累积

THE UPTAKE AND ACCUMULATIN OF TiO_2 NANOPARTICLES BY MAIZE PLANTS

研究了玉米对不同浓度及粒径纳米TiO2的吸收和累积,并应用同步辐射微束X射线荧光分析(μ-XRF)在微观尺度表征了玉米根中纳米TiO2的分布.结果表明,纳米TiO2主要累积在玉米根部,且在根部的累积量随暴露浓度的增加而增加;茎叶中TiO2累积很少,其在玉米体内的传输因子小于0.01.根中纳米TiO2的累积与其在溶液中的分散稳定性及表面电荷密切相关,团聚和沉降明显降低玉米根对纳米颗粒的吸收和累积.粒径较大的纳米TiO2在玉米根中的累积量较少,天然有机质胡敏酸(HA)的存在显著降低玉米根对纳米TiO2的吸收(p<0.05).同步辐射μ-XRF分析为植物体内纳米TiO2颗粒的分布提供了直接证据,纳米TiO2主要分布在根表皮层,木质部中含量极少,因而限制了纳米TiO2在植物体内的迁移.

The uptake and accumulation of TiO2 nanoparticles in maize were investigated in this study.Synchrotron microbeam X-ray fluorescence（μ-XRF） analysis was used to directly visualize distribution of nano-TiO2 in maize roots.The result showed that nano-TiO2 accumulated mainly in maize roots,and TiO2 accumulation in roots increased with increasing concentration of TiO2 nanoparticles suspended in solution.However,the contents of TiO2 in maize shoots were very low,and the root-to-shoot translocation factor of nano-TiO2 was lower than 0.01.The accumulation of nano-TiO2 in maize roots was closely related to its surface charge and suspension stability.Aggregation and sedimentation obviously reduced the uptake and accumulation of nano-TiO2 in maize roots.Nano-TiO2 contents in maize roots were lower when exposed to nano-TiO2 in bigger size.Humic acid（HA） in suspension significantly（p〈0.05） reduced the uptake of nano-TiO2 by maize roots.Observation with μ-XRF provides some insight into the characteristic of nano-TiO2 accumulation in maize roots.Nano-TiO2 mainly accumulated in the epidermal cells of roots with very limited transportation into the root interior,limiting its translocation from roots to shoots.