不同改良剂对镉污染土壤中小白菜吸收镉的影响

Effect of amendment on Cd uptake by Brassia chinensis in Cd-contaminated soils

  • 摘要: 采用盆栽试验, 研究了施用石灰、钙镁磷肥、泥炭、碱渣4种土壤改良剂对外加镉污染的赤红壤上小白菜产量、镉吸收量、土壤有效态镉及pH的影响。结果表明: 外加1 mg·kg-1和5 mg·kg-1镉对小白菜生物量无显著影响, 且1 mg·kg-1镉对小白菜生长有一定的促进作用; 施用改良剂对镉污染土壤上小白菜无显著增产效果。施用4种改良剂均能降低小白菜地上部镉含量, 作用效果为石灰≈泥炭>碱渣>钙镁磷肥。不同改良剂对小白菜根部镉含量影响不同, 泥炭和石灰在所有镉浓度下、钙镁磷肥在0和1 mg·kg-1镉浓度下可显著降低根部镉含量, 而碱渣无明显作用, 种植两茬规律一致。土壤有效态镉含量与pH呈显著负相关; 施用石灰、碱渣、钙镁磷肥使土壤pH显著升高, 有效态镉含量显著降低, 从而降低小白菜对镉的吸收; 泥炭可显著提高土壤pH, 虽降低土壤有效态镉作用效果不显著, 但显著降低小白菜体内镉含量, 这可能与土壤中形成难以被植物吸收的镉有机结合物有关。两茬蔬菜种植结果显示, 施用后期改良剂对镉污染的抑制效果也较明显。

     

    Abstract: The effects of 4 amendments lime, calcium-magnesium phosphate (Ca-Mg-P fertilizer), alkali slag and peat on biomass, Cd uptake of Brassia chinensis, and pH and DTPA-extracted Cd in Cd-contaminated soils were investigated in a pot experiment of two continuous crops of B. chinensis. The results show insignificant effects on B. chinensis biomass of additions of 1 mg·kg-1 and 5 mg·kg-1Cd. However, some form of promotion of biomass is noted under 1 mg·kg-1 Cd addition. Amendments do not significantly improve biomass, but remarkably decrease shoot Cd content in B. chinensis in Cd-polluted soils. The order of efficiency of the 4 amendments on reducing shoot Cd content is lime≈peat>alkali slag>Ca-Mg-P fertilizer. 4 amendments present different Cd-reduction effects on B. chinensis root. In the first and second crop, peat and lime decrease root Cd under all Cd treatments, while Ca-Mg-P fertilizer shows the same effect only under 0 and 1 mg·kg-1 Cd. Alkali slag shows not effect. There is a significantly negative correlation between soil DTPA-extracted Cd and pH. Lime, peat and Ca-Mg-P fertilizer increase soil pH, and decrease DTPA-extracted Cd, resulting in decreasing shoot Cd content in B. chinensis. Peat increases soil pH, but does not decrease DTPA-extracted Cd as much as pH. The main mechanism of Cd-reduction effect of peat on B. chinensis shoot could be related with the formation of organic-chelated Cd, which is difficult for B. chinensis to uptake. Comparison between the two crops indicates that amendments have a significantly decreasing effect on Cd content in B. chinensis in the second crop.

     

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