茶多酚和铜对可变电荷土壤钙镁释放的影响

通过批平衡试验,研究茶多酚、铜和体系pH对可变电荷土壤释放钙镁离子的影响。研究发现,铜离子初始浓度为2.0mmol/L,最终体系pH为5.0时,随着茶多酚添加量的增加,可变电荷土壤表面的负电荷增加,土壤表面释放的钙镁离子量减少。茶多酚初始添加量为20 g/kg,最终体系pH为5.0时,随着铜离子初始浓度的升高,可变电荷土壤对铜离子的吸附量增加,铜离子通过与钙镁离子发生离子交换,形成对吸附位点的竞争,从而增加钙镁离子的释放。茶多酚初始添加量为20 g/kg,铜离子浓度为2.0 mmol/L,随着pH的升高,可变电荷土壤钙镁离子释放量下降。在相同pH条件下,茶多酚可以通过自身的吸附增加可变电荷土壤表面负电荷,减少可变电荷土壤钙镁离子的释放量。研究结果可为茶园土壤酸化和污染控制提供参考。

Effects of Tea Polyphenols and Cu on Release of Ca and Mg from Variable-charge Soils

Batch experiments were conducted to investigate the effects of tea polyphenols, Cu and pH on the releases of Ca and Mg from two variable-charge soils (an Oxisol and an Ultisol). When the initial concentration of Cu was 2.0 mmol/L and the final system pH was 5.0, the releases of Ca and Mg from variable-charge soils decreased with the dosage increase of tea polyphenols, because of the surface negative charge was increased due to the presence of tea polyphenols. When the initial concentration of tea polyphenols was 20 g/kg and the final system of pH was 5.0, the releases of Ca and Mg from invariable-charge soils increased with the increase of initial concentration of Cu. The increase of initial concentration of Cu increased the adsorption of Cu by variable-charge soils. Cu exchanged with adsorbed Ca and Mg on the soils and competed for adsorption sites with Ca and Mg, which enhanced the releases of Ca and Mg from the two soils. When the initial concentration of tea polyphenols was 20 g/kg and initial concentration of Cu was 2.0 mmol/L, the releases of Ca and Mg from variable-charge soils decreased with the increase of suspension pH due to the increase in negative surface charge on the soils and electrostatic adsorption of Ca and Mg by the soils. At the same pH, tea polyphenols increased the negative charge of variable-charge soils and thus reduced the releases of Ca and Mg from variable-charge soils. The results above can provide useful references for the control of soil acidification and heavy metal pollution in tea gardens.