氯化铵和茶皂素单独与复合施用土壤中镉赋存形态的差异

为探讨氯化铵（NH₄Cl）和茶皂素（tea saponin, TS）对镉（Cd）赋存形态的影响,以矿区Cd污染农田土壤为试验材料,采用室内土壤培养方法,模拟不同剂量的无机氮肥NH₄Cl和TS单施及复合施加对Cd污染农田土壤理化性质及Cd有效性的影响。结果表明：单独施加NH₄Cl和TS促进了土壤中残渣态Cd向弱酸提取态及可还原态Cd的转化,提高了土壤中Cd的生物有效性,且高剂量（60 mg/kg）NH₄Cl施加要优于低剂量（20 mg/kg）NH₄Cl;NH₄Cl（40 mg/kg）和TS（4 mg/kg）复合施加同样促进了土壤中残渣态Cd向弱酸提取态Cd的转化,增加Cd的有效性,且增加效果等同于高剂量的NH₄Cl和TS单独施加。逐步回归分析表明,pH和Cl ^-是影响土壤中Cd有效性的2个关键因子。因此,在实际植物修复工作中可通过适当的农艺措施提高土壤Cl ^-降低土壤pH以增加植物对Cd的累积量。此外,低剂量的NH₄Cl配施TS可显著增加土壤中Cd的生物有效性,避免高施用量NH₄Cl引起的土壤环境恶化。

Difference of Cadmium Speciations After Single or Mixd Application Ammonium Chloride and Tea Saponin in Soil

In order to investigate the effect of ammonium chloride (NH₄Cl) and tea saponin (TS) on cadmium speciations in soil, the Cd-contaminated agricultural soils around mining areas were used as the experimental material. The effects of different doses of NH₄Cl, TS and mixed application on the physical chemical properties of the Cd polluted agricultural soil and Cd availability were simulated. The chemical of cadmium speciations was transformed from residual fractions into acid extractable or oxidizable fractions by adding NH₄Cl or TS singly. NH₄Cl obviously improved available Cd in soil, and high (60 mg/kg) concentration of NH₄Cl was better than low (20 mg/kg). Moreover, the chemical cadmium speciations was transformed from residual fractions into acid extractable fractions and improved available Cd by adding the combination of NH₄Cl (40 mg/kg) and TS (4 mg/kg), and mixed application had the same effect with NH₄Cl or TS. Stepwise regression analysis showed that pH and Cl ^-were the two key factors affecting Cd availability in soil. In the actual phytoremediation work, in order to increase the Cd content of plants, we could take appropriate agronomic measures to increase Cl ^- or decrease pH in soil. Low concentration NH₄Cl and TS mixed application significantly would improve the Cd bioavailability and avoid soil environment destruction caused by high concentration NH₄Cl application.