3种金属氧化物纳米材料在不同土壤中运移行为研究

采用实验室柱淋溶方法,考察了纳米CeO2、纳米TiO2和纳米Al2O3材料在不同土壤中的运移行为,分析了纳米材料在土壤中运移能力与土壤性质的相关性,并采用胶体运移动力学模型估算了纳米材料在土壤中的最远运移距离.结果表明,纳米CeO2和纳米TiO2在试验的大部分土壤中有很强的运移能力,而纳米Al2O3仅在试验的酸性土壤中有较强的运移能力,在其他土壤中几乎被全部截留.纳米材料在土壤中运移的机制非常复杂,静电作用、土壤表面电荷异质性、团聚作用、张力作用(straining)以及过滤熟化作用(ripening)均对纳米材料的运移有着重要的影响.纳米CeO2的运移能力与土壤Zeta电位显著负相关;纳米TiO2的运移能力与土壤黏粒含量显著负相关,与土柱渗透系数显著正相关;纳米Al2O3的运移能力与土壤pH显著负相关,与土柱渗透系数显著正相关.模型估算的纳米CeO2、纳米TiO2和纳米Al2O3在试验土壤中的最远运移距离分别为52~69 043、31~332和<10~5 722 cm.纳米材料在一些土壤中的最远运移距离远远大于30 cm表层土壤的深度,意味着纳米材料在这些土壤中有向深层土壤运移的可能.

Transport Behaviors of Metal Oxide Nanomaterials in Various Soils

Transport behaviors of nano-CeO₂, nano-TiO₂ and nano-Al₂O₃ materials in various soils were investigated by column leaching experiment. The relationship between transportability of nanomaterials and soil properties was analyzed and potential transport distances of nanomaterials in soils were estimated by applying the colloid migration dynamic model. The result shows that both nano-CeO₂ and nano-TiO₂ have strong mobility in most of tested soils. While nano-Al₂O₃ is almost completely retained in most of tested soils except acidic soil, in which nano-Al₂O₃ shows relatively strong transportability. The transport mechanisms of nanomaterials in soils are very complicated. Among electrostatic interaction, soil surface charge heterogeneities, aggregation, straining and ripening, each of them plays an important role in the transport of nanomaterials. The transportability of nano-CeO₂ is negatively correlated with soil Zeta potential, while that of nano-TiO₂ is negatively correlated with soil clay content, and positively correlated with soil permeability coefficients. The transportability of nano-Al₂O₃ is negatively correlated with soil pH, and positively correlated with soil permeability coefficients. The estimated maximum transport distances of nano-CeO₂, nano-TiO₂ and nano-Al₂O₃ materials in soils were 52-69043 cm,31-332 cm and <10-5722 cm, respectively. The estimated potential transport distances of nanomaterials in some soils are far more than the surface soil depth of 30 cm, indicating severe risks to deeper soil layers would potentially occur in these soils.