玉米秸秆生物炭对稻田土壤砷、镉形态的影响

Effects of waterlogging and application of bio-carbon from corn stalks on the physico-chemical properties and the forms of arsenic and cadmium in arsenic and cadmium-contaminated soils

通过室内土壤培养的方法模拟稻田土壤环境,研究淹水环境下添加(1%添加量)不同温度制备的玉米秸秆生物炭(CB-300、CB-400、CB-500)对砷、镉复合污染稻田土壤氧化还原电位(Eh)、pH值及不同形态砷、镉含量动态变化的影响.结果表明,热解温度会影响玉米秸秆生物炭的理化性质,热解温度由300℃升至500℃,玉米秸秆生物炭芳香性增加,亲水性和极性降低,灰分含量增加,pH值升高.淹水环境下添加玉米秸秆生物炭处理相比对照(CK)可提高土壤pH值0.20~1.24,升高幅度大小为CB-500>CB-400>CB-300>CK,随着培养时间的延长,pH值趋于平衡状态;淹水环境下土壤氧化还原电位均迅速下降,且不同处理组间存在显著差异,生物炭制备温度越高下降效果越明显,培养至第96 d时氧化还原电位降到最低.CK、CB-300、CB-400、CB-500处理组弱酸可提取态镉含量由淹水前的73.55%分别降至63.46%、57.73%、54.50%、53.94%,随着培养时间的延长,土壤中弱酸可提取态及可氧化态镉逐渐向残渣态及可还原态镉转化.土壤pH值与弱酸可提取态镉含量之间呈显著负相关关系.淹水环境下土壤可交换态砷含量升高,玉米秸秆生物炭的施加导致土壤交换态、Ca-结合态、Al-结合态和Fe-结合态砷含量逐渐上升,上升幅度分别为75.68%、20.92%、13.49%、48.66%,残渣态砷含量下降;土壤pH值与交换态砷含量之间呈显著正相关关系.研究结果可为砷、镉复合污染稻田安全生产与阻控提供数据支持.

Effects of corn stover biochar （ 1% addition） prepared at different temperatures （300,400 and 500 ℃ ） on pH, oxidation-reduction potential and arsenic and cadmium contents in arsenic-cadmium polluted paddy soil under waterlogged conditon were investigated by indoor soil incubation. The corn stover bioehar prepared at 300,400 and 500 ℃ were designated as CB-300, CB-400 and CB-500, respectively, with no addition of CB as blank control. The results showed that pyrolysis temperature has a significant effect on physical and chemical properties of corn straw. Increasing the pyrolysis temperature from 300 ℃ to 500℃ resulted in increases in aromatieity （corresponding to decrease in hydrophilicity and polarity）, ash content and pH in corn stalks. Addition of corn straw bioeoke increased The soil pH increased from 0.2 to 1.24 after addition of corn straw bioeoke in soil, compared with CK and followed the order： CB-500〉CB-400〉CB-300〉CK, and the pH reached equilibrium with prolongation of culture.The redox potential of soil under flooded condition decreased rapidly, and there was significant difference among different treatments. The higher the temperature of biocarbon preparation, the more obvious decreases in redox potential.The redox potential decreased to the lowest at 96th day. The percentage of extractable Cd in CK, CB-300, CB-400 and CB-500 decreased from 73.55% to 63.46%, 57.73%, 54.50% and 53.94%, respectively, and the cadmium changed from extractable and oxidizablestate to the residual and reducible state, with the extension of culture time. Soil pH exhibited a significant negative correlation with weak acid extractable cadmium. The content of exchangeable arsenic in the soil under waterlogged condition increased, and the exchangeable arsenic, calcium arsenic, aluminum arsenic and iron arsenic in the soil were increased by 75.68%, 20.92% and 13.49% and 48.66%, respectively, however, residue- state arsenic dcreased. There was a significant positive correlation between soil pH and exchangeable arsenic. This study can provide statistic datafor safe agricultural production on arsenic-cadmium polluted paddy soil.