季节性冻融作用对土壤吸附稀土元素镧的影响

The effect of seasonal freeze-thaw on the soil adsorption of rare earth elements lanthanum

通过室内模拟,研究冻融作用对土壤理化性质的影响,并分析不同冻融频次对土壤吸附稀土元素镧的影响,探究其影响机制。结果表明,随着冻融频次的增加,土壤pH升降变化幅度不大;有机质在冻融频次为二次时,达到最大值42. 61 g/kg,且随着冻融频次的增加呈现下降趋势;游离氧化铁由7. 67 g/kg下降到3. 62 g/kg后上升到13. 47 g/kg。同时,土壤对稀土元素镧的吸附量随冻融频次的增加而逐渐减小。经过8次冻融,土壤对镧的最大吸附量由1. 89 mg/g下降到1. 09 mg/g,说明冻融作用对土壤吸附稀土元素镧有抑制作用,这与冻融作用改变了土壤的理化性质有关。冻融作用改变了土壤对稀土元素镧的吸附机制,使专性吸附向非专性吸附转变,促进了稀土元素镧向土壤中的解吸和释放,增加了土壤中镧的生态风险。

This study treated the rare earth element lanthanum as the experimental object to research the influence of the freeze-thaw on the soil physical and chemical properties,and analyze the different freezing and thawing frequency influence on soil adsorption of rare earth element lanthanum,and explore its effect mechanism.The results showed that:With the increasing of freeze-thaw frequency,the change of soil pH was not great.The organic matter reached a maximum of 42.61 g/kg when the freeze-thaw frequency was twice,and with the extension of the freeze-thaw cycle it decreased.The free iron oxide rose from 7.67 g/kg to 3.62 g/kg and then up to 13.47 g/kg.As the initial lanthanum concentration phase,the adsorption capacity of lanthanum on rare earth elements decreased with the increasing of freeze-thaw frequency.After eight times of freeze-thaw,the maximum soil of lanthanum decreased from 1.89 mg/g to 1.09 mg/g,which explained freeze-thaw reduced the adsorption quantity of rare earth element lanthanum in soil.It had something to do with changes of soil physical and chemical properties by freeze-thaw.The freeze-thaw caused the change of the soil adsorption mechanism of lanthanum,which caused the transformation of the obligatory adsorption to non-obligatory adsorption.So it was beneficial to the desorption and release of lanthanum in the soil.