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采用水培方法,研究了紫花苜蓿吸收水溶液中Cd2+时根系与水环境的阳离子交换.考察了紫花苜蓿分别在0、1、2、4、8、12、24、72 h对0～10 mg.L-1 Cd2+体系中Cd2+的吸收效果,体系中Na+、K+、Mg2+、Ca2+、NH 4+阳离子的浓度变化,以及溶液pH变化.并以SPSS 13.0多重线性回归建立Cd2+吸收量与阳离子变化量模型.结果表明,紫花苜蓿对体系中Cd2+有一定吸收作用,72 h时对0.1、1、5、10 mg.L-1 Cd2+的吸收率分别为85.86%、52.14%、15.97%、7.81%;紫花苜蓿对Cd2+的吸收过程存在阳离子交换作用,除NH 4+外体系中Na+、K+、Mg2+、Ca2+离子浓度随时间均有一定的增大,分别增加了11.30%～61.72%、21.44%～98.73%、24.09%～48.90%、37.04%～191.96%;准二级动力学模型可以较好地描述体系中Na+、K+、Mg2+、Ca2+的变化规律,在Cd2+浓度为1、5、10 mg.L-1时准二级动力学模型对NH 4+变化规律的拟合也是合适的;紫花苜蓿对Cd2+吸收过程中体系pH下降,H+可能作为Cd2+竞争离子,影响紫花苜蓿根系对Cd2+的吸收能力;三元线性回归方程证明紫花苜蓿对Cd2+吸收量主要与Ca2+、Mg2+、Na+变化量有关,且其交换主要发生在Cd2+与二价阳离子之间.
The hydroponics method was used to study the cation exchange between roots and aqueous environment of alfalfa after absorbing Cd2 + in aqueous solution.The effects of alfalfa on 0, 1, 2, 4, 8, 12, 24, 72 h and 0-10 mg were investigated. The absorption of Cd2 + in L-1 Cd2 + system, the changes of Na +, K +, Mg2 +, Ca2 + and NH4 + cations in the system and the change of pH of the solution were determined by using SPSS 13.0 multiple linear regression model. The results showed that alfalfa had a certain absorption effect on Cd2 + in the system, and the absorption rates of Cd2 + at 0.1, 1, 5 and 10 mg · L-1 Cd2 + were 85.86%, 52.14%, 15.97% and 7.81% at 72 h, Alfalfa had a positive effect on cation exchange of Cd2 +. The concentrations of Na +, K +, Mg2 + and Ca2 + in algae increased by 11.30% -61.72% and 21.44% -98.73% with the exception of NH4 + , 24.09% -48.90% and 37.04% -191.96%, respectively. Quasi-second order kinetic model can well describe the variation of Na +, K +, Mg2 + and Ca2 + in the system, 1 quasi-second-order kinetic model fitting NH 4+ variation law is appropriate; alfalfa Cd 2+ absorption process The pH of the system decreased, H + might act as competitive ions for Cd2 +, affecting the Cd2 + uptake capacity of alfalfa roots. The ternary linear regression equation proved that Cd2 + uptake by alfalfa was mainly related to the changes of Ca2 +, Mg2 + and Na + Between Cd2 + and divalent cations.