生物质炭改良酸性土壤的电化学特性试验研究
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浙江大学环境与资源学院

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国家自然科学基金(41977005)和国家重点研发计划项目(2016YFD0200302)资助


Experimental Study on Electrochemical Characteristics of Acid Soil Amended by Biochar
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College of Environmental and Resource Sciences, Zhejiang University

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Supported by the National Natural Science Foundation of China (No. 41977005) and the National Key Research & Development Program of China (No. 2016YFD0200302)

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    摘要:

    设置五种有机物料(水稻秸秆、玉米秸秆、小麦秸秆、稻壳和竹子)制备的生物质炭改良酸性土壤的田间小区试验,以不施生物质炭为对照(CK),运用电化学阻抗谱法研究了不同生物质炭对酸性土壤电化学特性的影响。结果表明,不同处理的等效电路拓扑结构一致,但电路元器件参数存在差异;Nyquist图表现为高频区圆弧和低频区斜线的形式,各曲线与横坐标的截距对应等效电路中土壤多孔层电阻R2,圆弧半径对应电荷转移电阻R3,Bode图中不同生物质炭改良酸性土壤的阻抗模值随频率增大整体呈减小趋势。通过Z-view软件对等效电路拟合可知,不同生物质炭改良酸性土壤对各元件参数值的影响为孔隙溶液电阻R1减小,土壤多孔层电阻R2增大和电容C1减小,电荷转移电阻R3和扩散阻抗系数W增大,以及CPE-T值减小。其中,R1的减小表示土壤水溶性盐含量和CEC的增加;R2增大和C1减小表示土壤介质体系的导电能力降低;R3、W和CPE-T值的变化表示土壤体系的转移电荷能力降低和整体稳定性的提高。拟合参数值在一定程度上揭示了改良酸化对土壤pH和可溶性盐基离子含量的影响,同时丰富了电化学阻抗谱的研究范围。

    Abstract:

    【Objective】Climate change and the continuous impact of high-intensity human activities are intensifying soil acidification and has caused serious harm to the ecological environment and agricultural production. In recent years, studies on acid soils have focused on the effects and related mechanisms of soil conditioners on physicochemical properties and crop production, but the combined application of electrochemistry theory and other interdisciplinary principles have been given less attention. Electrochemical Impedance Spectroscopy (EIS) is an electrochemical measurement method using small-amplitude sinusoidal potential (or current) as a disturbance signal. Its application in the soil field has attracted much attention. In this study, EIS was combined with soil physical and chemical properties to analyze the electrochemical mechanism of biochar in improving acid soils. 【Method】A field study was conducted to amend acid soil by applying biochars produced from five biomass materials (rice straw, corn straw, wheat straw, rice husk, and bamboo). The EIS was used to study the influence of different biochars on the electrochemical characteristics of acid soil. 【Result】Results showed that the equivalent circuit topology structure was the same in different biochar-amended treatments, but the circuit component parameters were different. The equivalent circuit model was the charge transfer resistor R3 and diffusion resistor Rw at the electrode-solution interface in series, and in parallel with CPE. This part was connected in series with the soil porous layer resistor R2, and then in parallel with the soil porous layer capacitor C1. Finally, it was connected in series with pore solution resistor R1. The addition of biochar had regular effects on Nyquist and Bode diagrams. The Nyquist diagram was in the form of arcs in the high-frequency region and oblique lines in the low-frequency region. The intercepts of each curve and x-coordinate corresponded to the resistance R2 of the soil porous layer in an equivalent circuit, and a radius of each to a charge transfer resistance R3. In the Bode diagram, the impedance modulus of the modified soil amended with different biochars tended to decrease as the frequency increased. By fitting the equivalent circuit with Z-view software, it was found that the influence of different biochars on the parameter values of each element was related to changes in soil physicochemical properties. The addition of biochar increased soil contents of total soluble salts and CEC, and the concentration of free-moving ions increased, thus the electrochemical characteristics showed that the pore solution resistance R1 decreased. Since biochar was almost non-conductive, the conductive capacity of improved soil decreased, and the electrochemical characteristics showed that resistance R2 of the soil porous layer increased while capacitor C1 decreased. The cations of acid soil neutralized by biochar slowed down the process of charge transfer, increased the reaction resistance, and weaken the ability to store charge. Thus, this reduced the reaction speed and made the system more stable. The electrochemical characteristics were shown as the increase of transfer resistance R3 and diffusion impedance coefficient W, as well as the decrease of CPE-T value. 【Conclusion】The decrease of R1 indicated the increase of soil water-soluble salt content and CEC. The increase of R2 and the decrease of C1 indicated that the conductivity of the soil medium system decreased. The changes of R3, W and CPE-T indicated the charge transfer ability and overall stability of the soil system. The fitting parameters revealed the influence of modified acidification on soil pH and soluble base ions content to a certain extent, which enriched the scope of electrochemical impedance spectroscopy (EIS).

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杨彩迪,刘静静,卢升高.生物质炭改良酸性土壤的电化学特性试验研究[J].土壤学报,,[待发表]
YANG Caidi, LIU Jingjing, LU Shenggao. Experimental Study on Electrochemical Characteristics of Acid Soil Amended by Biochar[J]. Acta Pedologica Sinica,,[In Press]

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