水稻秸秆生物炭对3种土壤水溶态Cd动态变化的影响

Effects of Rice Straw Biochar on Water-soluble Cd in Three Flooded Different Types of Soil

【目的】探讨淹水环境下生物炭对不同类型土壤中镉(Cd)的钝化效果,为生物炭修复镉污染稻田土壤提供科学依据。【方法】将外源Cd添加到黄壤、红壤性水稻土和棕壤中,分别设置对照和添加5%(W/W)生物炭处理,通过室内模拟试验探讨淹水条件下生物炭对不同土壤中Cd钝化效果的影响。【结果】淹水初期(1 d),与对照相比生物炭处理显著降低3种土壤溶液的pH值和土壤氧化还原电位值(Eh),但提高了土壤电导率值。随淹水时间增加,对照处理的3种土壤Eh值均逐渐降低,生物炭处理可使土壤氧化还原反应减缓。在淹水初期,对照处理下的3种土壤水溶态Cd含量由高到低依次为:黄壤(272.5μg·L^(−1))>红壤性水稻土(23.48μg·L^(−1))>棕壤(1.44μg·L^(−1)),生物炭处理的3种土壤水溶态Cd含量分别降低31.66%、75.04%和66.67%。随淹水时间增加,对照处理下黄壤和红壤性水稻土的水溶态Cd含量均逐渐降低,到淹水30 d时的降幅分别为89.34%和76.53%;而生物炭处理的水溶态Cd含量降低幅度较小,分别为85.41%和37.03%。淹水30 d之后,与对照处理相比,生物炭处理的黄壤、红壤性水稻土和棕壤有效态Cd含量分别降低17.3%、56.3%和12.4%。【结论】5%生物炭处理可显著降低3种土壤的水溶态Cd含量。但随淹水时间增加,3种土壤的对照处理与生物炭处理之间的水溶态Cd含量差值均缩小。淹水30 d后,与对照处理相比,生物炭对水稻土有效态Cd含量的降幅大于棕壤和黄壤。

【Objective】To investigate the effect of biochar made from rice straws on cadmium(Cd)immobilization in different types of soil under flooding.【Method】An in-lab experiment on 3 Cd-added different types of soil with or without a 5%addition of biochar made from rice straws was conducted under varied durations of flooding.The types of soils used were yellow soil,paddy soil derived from quaternary red clay,and brown soil.【Result】The biochar reduced pH and redox potential(Eh)but increased conductivity of the soils on the first day after flooding.As the flooding persisted,Eh in the soils reduced continuously,but the rate declined in the presence of the biochar.During the initial stage of flooding,the Cd contents in the soils were highest in the yellow soil at 272.5μg·L^(−1) followed by the paddy soil at 23.48μg·L^(−1),while the brown soil at 1.44μg·L^(−1) being the lowest.The Cd reductions by 31.66%in the yellow soil,75.04%in the paddy soil,and 66.67%in the brown soil were attributed to the added biochar.Under prolonged flooding,the Cd in the yellow and paddy soils gradually decreased even without the biochar addition.In 30d,the reductions were 89.34%on the yellow soil and 76.53%on the paddy soil.In comparison,the addition of the biochar brought about 85.41%Cd reduction on the yellow soil and 37.03%on the paddy soil.After 30d of flooding,the biochar out-performed control with the CaCl2-Cd contents in the yellow,paddy,and brown soils lowered by 17.3%,56.3%,and 12.4%,respectively.【Conclusion】By adding 5%of the rice straw biochar,the water-soluble Cd in the 3 different types of soil could be significantly reduced.Prolonged flooding made the effect less pronounced,and the biochar immobilization of Cd appeared more effective in the paddy soil than the other two soil types.