壳聚糖对镉污染土壤中油菜生长及镉含量的影响

Effects of Chitosan on the Growth and Cadmium Adsorption of Rape in Cadmium-contaminated Soil

通过盆栽试验,以油菜为实验材料,用不同浓度(0、0.25、0.50、1.00、2.00、5.00、10.00、20.00g/kg)壳聚糖分别处理镉污染(含Cd2+为25mg/kg)土壤,研究油菜生长及其对镉的吸收.结果表明低浓度(≤1.00g/kg)的壳聚糖对油菜的生长有促进作用,而较高浓度(>1.00g/kg)时,随着土壤中壳聚糖浓度的升高,油菜的根长、鲜重、干重、可溶性糖和可溶性蛋白等生理指标不断下降;油菜植株体内Cd2+的浓度随着壳聚糖浓度的升高而升高,而土壤中Cd2+的浓度逐渐降低;在壳聚糖浓度为1.00g/kg时,土壤中Cd2+的浓度明显下降,之后随着浓度的升高,趋于平稳.这说明壳聚糖能促进油菜对Cd2+的吸收,提高油菜对镉污染土壤的修复效果.但由于油菜对Cd2+耐受性的局限性,大于1.00g/kg的壳聚糖促进油菜对镉的吸收,油菜植株也受到镉的毒害,生物量下降,修复效果下降.

In this paper, the growth and cadmium adsorption of rape（Brassica campestris L.） in Cdcontaminated（contained 25 mg/kg Cd2＋） soil under different concentrations of chitosan（0, 0.25, 0.50, 1.00, 2.00, 5.00, 10.00 and 20.00 g/kg） were studied by pot experiment. The results showed that lower concentrations（ ≤ 1.00 g/kg） of chitosan promoted the growth of rape, but the root length, fresh weight, dry weight of rape, and the physiological index of rape leaf（soluble sugar and soluble protein） all declined with the increasing concentrations of chitosan under higher concentrations of chitosan（1.00 g/kg）; the Cd2＋content in rape plant increased with the increasing concentrations of chitosan, while the soil Cd2＋content declined with the increasing concentrations of chitosan; soil Cd2＋ content clearly decreased at 1.00 g/kg concentration of chitosan, then tended to level off with the increasing concentrations of chitosan. It indicated that chitosan may promote the cadmium adsorption of rape, and improve the phytoremediation efficiency of rape for Cd-contaminated soil. However, the higher concentrations of chitosan（1.00 g/kg） would lower the phytoremediation efficiency, because that the toxic effect of Cd2＋ on rape growth and the decrease of biomass, which resulted from the higher concentrations of chitosan（1.00 g/kg） promoted the cadmium adsorption of rape, due to the rape has no tolerance to high concentrations of cadmium.