不同水分条件下镉在土壤中形态转化的动态过程

[目的]研究不同土壤水分条件下,外源镉(Cd)进入土壤中的形态随时间的变化规律。[方法]采用室内培养,模拟不同湿度土壤,连续提取法进行Cd形态分析。[结果]外源Cd进入黑土后,交换态Cd在培养初期迅速下降,以后逐渐变慢并趋于平稳;碳酸盐结合态呈现先小幅度增加后减小的趋势;铁锰氧化物结合态Cd的含量在培养前30d内较快增加,而后趋于平衡;黑土中有机态Cd含量先增加后缓慢降低;残渣态Cd随培养时间的增加呈现逐渐增加的趋势;在培养前期碳酸盐态Cd含量淹水要高于水分适度条件,但淹水条件下交换态的下降更为迅速;适度水分时铁锰态Cd含量要显著高于淹水条件下的Cd含量。[结论]土壤湿度通过影响金属在土壤各相中的再分配强烈影响金属的可利用性,Cd在淹水条件下比水分适度条件下更容易达到一种稳定的状态。

Dynamic Process of the Morphological Transformation of Cadmium in Soil under Different Moisture Conditions

[Objective] This paper was to investigate the change rules of Cd morphology in soil with time under different water conditions.[Method] A simulated pot experiment was conducted in two water condition(field capacity moisture and saturated-paste regime).The analysis of Cd fractions in soil was by conducted sequential extraction.[Result] When entering into phaeozem,exchangeable Cd content(EX) decreased rapidly at initial stage,and then reached a balance gradually.Carbonate bound fraction Cd(CARB) increased marginally firstly and decreased afterwards,however it did not stabilize in incubation period.Iron manganese oxide bound fraction Cd(IMOB) increased rapidly in first 30 days of incubation,and then tended to be invariable.Residual Cd(RES) increased continuously with time.The reduction of CARB was faster in saturated-paste water regime than in field capacity moisture content regime.IMOB was higher in field capacity moisture content than in saturated-paste regime.[Conclusion] Soil moisture regime affected intensively bioavailability of Cd by altering the redistribution of metal in soil.Compared with field capacity moisture,Cd tended to be stable in saturated-paste regime.