二种钾肥对海泡石钝化修复镉污染土壤效应影响的研究

为了揭示钾肥对Cd污染土壤钝化修复效果的影响,为土壤钝化修复过程中合理施钾肥提供理论依据。本文选取不同剂量(含量以K2O计算,分别为0.1 g·kg~(-1)、0.2 g·kg~(-1)和0.3 g·kg~(-1))的KCl和K_2SO_4作为典型钾肥,以海泡石(10 g·kg~(-1))作为钝化材料,通过油菜盆栽试验,研究了两种钾肥在海泡石钝化条件下对Cd污染土壤修复效应的影响。结果表明:K_2SO_4显著增加了油菜的生物量,其增幅为6.06%~10.05%。与单施海泡石钝化相比,在海泡石钝化时施用KCl和K_2SO_4两种钾肥,油菜地上部茎叶Cd含量分别增加16.38%~60.73%和15.62%~25.19%;施用KCl和K_2SO_4对土壤p H未产生显著性影响,却显著地增加了土壤有效态Cd含量,其增幅分别为25.51%~34.65%和18.5%~24.96%。添加海泡石可使土壤的Zeta电位向负值方向移动,提高土壤对Cd的负载能力;但添加海泡石下施用KCl和K_2SO_4均能提高土壤的Zeta电位,降低土壤对Cd的负载能力。等温吸附试验同样表明,添加KCl和K_2SO_4均能降低海泡石对Cd的吸附量,在水溶液中海泡石对Cd的最大吸附量为5.30 mg·kg~(-1),添加KCl和K_2SO_4后吸附量分别降低至2.87 mg·g~(-1)和4.92 mg·g~(-1)。KCl和K_2SO_4显著改善了土壤中K、Mn、Cu和Zn等营养元素的有效态含量。从上述结果可以发现,在海泡石钝化修复Cd污染土壤过程中,施K_2SO_4对钝化效果的影响小于施KCl。

Effect of potassium fertilizers on immobilization remediation of Cd-polluted soils using sepiolite

Cadmium (Cd) is one of the most toxic pollutants in soil environments because of its persistence, toxicity and potential for bioaccumulation. Natural sepiolite has recently been found as a cost-effective material for immobilization remediation of metal-contaminated soils due to its low cost, high cation exchange capacity, and high specific surface area associated with the small particle sizes. In agricultural production, the application of various fertilizers is vital, but the effects of fertilizer addition to polluted soils on immobilization remediation have been little investigated. In previous studies on immobilization experiments, only remediation effects were emphasized. The effects of nutrient elements on remediation process promotion or inhibition has been largely ignored. For large application of immobilization remediation in different areas with various fertilizer forms, the impact of fertilizers on the process must be determined. In this research, natural sepiolite (10 g·kg^-1) was used as immobilization agent and meanwhile potassium chloride (KCl) and potassium sulphate (K₂SO₄) used as representative potassic fertilizers in rape pot experiments to determine the effects of potassic fertilizers on the process of immobilization remediation of Cd-polluted soil. The potassium fertilizer content was calculated as K₂O, with 0.1 g·kg^-1, 0.2 g·kg^-1 and 0.3 g·kg^-1, respectively. The results showed that rape biomass significantly increased (by 6.06%-10.05%) after the application of K₂SO₄, compared with sole sepiolite treatment. Cd contents in shoot increased respectively by 16.38%-60.73% and 15.62%-25.19% after the application of KCl and K₂SO₄. KCl and K₂SO₄ had little effects on soil pH, but increased exchangeable Cd concentration significantly (respectively by 25.51%-34.65% and 18.5%-24.96%). Sepiolite conduced Zeta potential of soil samples to shift in negative direction, while the addition of KCl and K₂SO₄ made the Zeta potential of soil samples increase. The maximum adsorption of Cd by sepiolite in aqueous solution was 5.30 mg·g^-1, but KCl and K₂SO₄ reduced sorption of Cd on sepiolite, with maximum sorption of respectively 2.87 mg·g^-1 and 4.92 mg·g^-1. Bioavailable fractions of K, Mn, Cu and Zn were enhanced significantly by the additions of KCl and K₂SO₄. Considering the various factors during passivation of sepiolite to Cd-contaminated soils therefore, the effect of application of K₂SO₄ on passivation was less than that of application of KCl. On the whole, K₂SO₄, rather than KCl, was recommended potassic fertilizer for remediation of Cd-contaminated soils using sepiolite.