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

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1mg·kg-1和5mg·kg-1镉对小白菜生物量无显著影响,且1mg·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1mg·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。

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-1 Cd.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≈peatalkali slagCa-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.