二氧化钛纳米颗粒对铜在土壤中运移的影响

摘要

采用柱淋溶实验方法研究了二氧化钛纳米颗粒对铜在不同士壤中运移的影响.结果表明,在有机质含量较低的灰褐土和潮土中,二氧化钛纳米颗粒的存在使铜在这两种土壤中迁移能力分别增强了8432倍和32倍,二氧化钛纳米颗粒结合态铜是铜在土壤中运移的主要形态.然而这一现象在具有较高有机质含量的褐土和黑土中变得不明显.在褐土中只有1.35%的铜以二氧化钛纳米颗粒结合态运移;而在黑土中,几乎没有二氧化钛纳米颗粒结合态运移的铜,二氧化钛纳米颗粒不作为铜离子运移的载体.在运移过程中,铜能部分或完全地从二氧化钛纳米颗粒上解吸下来.土壤有机质是引起二氧化钛纳米颗粒吸附态铜解吸的重要因素,铜从二氧化钛纳米颗粒上解吸比率随着土壤有机质含量的增加而增加.土壤有机质对铜离子具有强烈的络合作用,土壤有机质越高,越容易从二氧化钛纳米颗粒上竞争吸附铜离子,从而增加铜的解吸比率.%Effect of TiO2 nanoparticles on transport of Cu in various soils was studied in a leaching experiment. It was found that TiO2-nanoparticle-colloids-associated Cu was the sole and main form transporting in sand and sandy-loam soils relatively low in soil organic matter and high in cation exchange capacity, respectively. The presence of TiO2 nanoparticles actually increased the movability of Cu by 8 432 and 32 times in sand and sandy-loam soils, respectively. However, this enhanced phenomenon was significantly reduced in silt-sandy-loam and loam soils. In silt-sandy-loam soil, only 1.35％ of Cu was transported in TiO2-nanoparticle-associated form. In loam soil, soluble Cu was the sole form in transportation and TiO2 nanoparticles were no longer the carrier. During the transport through soils, the previously adsorbed Cu on TiO2 nanoparticles were effectively stripped off and extent of the stripping depended on soil properties. Soil organic matter demonstrated a strong tendency to get into chelation with Cu, therefore soil organic matter is an important factor that determines desorption of Cu from TiO2 nanoparticles. The higher the content of soil organic matter in the soil, the easier for it to compete for Cu adsorption with TiO2 nanoparticles and the higher the Cu desorption rate in the soil.