可变电荷土壤中根-土相互作用与根/土界面的电化学特征

The interface between plant roots and soil particles is a critical zone for nutrients and pollutants entering into plant body from soils. However, few studies involved in the interaction between charged roots and soil particles and the effects of the interaction on electrochemical properties and chemical behaviors of chemicals at the interface until now and the mechanisms for the interaction between roots and soil particles are not well understood. In this project, the new methods will be developed based on electrochemical principles and corresponding analytical equipments will be set up to investigate the interaction between electric double layers on plant roots and soil particles in variable charge soils, and to elucidate the mechanisms for the effects of the interaction on the chemical behaviors of nutrients and heavy metals at interface between plant roots and soil particles. We will also investigate the acid-base reactions and chemical behaviors of aluminum at the interface between plant roots and soil particles, and study the relationship between the mechanisms for aluminum resistance of plants and their preferring absorption of ammonium or nitrate. The interrelationship between the interaction of electric double layers on roots and soil particles and acid-base reactions at interface between plant roots and soil particles will be elucidated based on the data obtained. The reduction-oxidation reactions at interface between roots and soil particles will be investigated to elucidate the relationship between the interactions among rice roots, iron plaque and soil particles and their effects on uptake of elements by rice. The reducing ability of root secretions under upland conditions will be studied, and the reducing dissolution of manganese oxides by root secretions at interface between plant roots and soil particles will also be investigated to discover the mechanisms for the reduction-oxidation reactions at root/soil interface. The project will break new research area of root/soil interface electrochemistry for soil electrochemistry. The results obtained in the project will provide useful references for nutrient management and environmental protection of variable charge soils.

根/土界面是营养元素和污染物进入植物体的关键区域，目前对带电的根表和土壤颗粒之间相互作用及其对界面电化学性质和化学物质的界面化学行为的影响的研究非常有限，对相关的作用机制知之甚少。本项目将根据电化学原理建立表征根/土界面双电层作用的方法，研制相应的测定装置。研究可变电荷土壤根/土界面双电层作用规律，阐明根/土界面双电层作用影响养分和重金属的界面化学行为的机制；研究根/土界面的酸碱反应与铝的界面化学行为，明确植物喜硝或喜铵特性与界面酸碱反应和耐铝机制的关系, 阐明根/土双电层作用与根/土酸碱反应互作的电化学机制；研究根/土界面的氧化还原反应，阐明水稻根-铁膜-土壤胶体颗粒相互作用与元素吸收的关系，明确旱作条件作物根系分泌物的还原能力及其与氧化锰在根/土界面的氧化还原反应的关系。本研究将为土壤电化学开辟根/土界面电化学新学术领域，研究结果将为可变电荷土壤的养分管理和土壤环境保护提供科学指导。

根/土界面是营养元素和污染物进入植物体的关键区域，目前对带电的根表和土壤颗粒之间相互作用及其对界面电化学性质和化学物质的界面化学行为的影响的研究非常有限，对相关的作用机制知之甚少。本项目将研发根/土界面电化学性质的新表征方法，研制相应的测定装置。研究可变电荷土壤根/土界面带电表面之间的相互作用、根/土界面的酸碱反应以及根/土界面的氧化还原反应。经过5年的研究，自行设计和制作一套测定土壤和植物根表面电化学性质的流动电位测定装置，研制一系列适用于不同带电表面电化学性质测定的测量池，建立了用于测定完整土壤zeta电位、完整植物根的zeta电位、土壤胶体与带电大颗粒和植物根与带电颗粒相互作用的流动电位方法。研究发现籼稻根系表面负电荷和官能团数量多于粳稻根系，因而前者对重金属Cu(II)和Cd(II)的吸附量多于后者。研究了水稻根与铁铝氧化物包被石英砂之间的相互作用、铁铝氧化物胶体悬液与石英砂之间的相互作用、蒙脱石和高岭石胶体悬液与铁铝氧化物包被石英砂之间的相互作用，发现这些带相反电荷的表面之间均存在扩散层重叠作用，并导致界面有效电荷减少。研究发现大肠杆菌、枯草芽孢杆菌和荧光假单胞菌等细菌与铁铝氧化物和可变电荷土壤之间存在强烈的相互作用，细菌吸附导致土壤和氧化物表面正电荷减少，负电荷增多。研究发现玉米和小麦吸收硝态氮后根系释放氢氧根对根际土壤酸度的改良作用，玉米和大豆根系吸附的铝主要以交换态和络合态存在。系统研究了铵态氮对水稻铝毒的缓解作用，阐明这一作用的生理机制。研究发现玉米和大豆根系分泌物的还原性物质对根际土壤中氧化锰具有还原作用；大豆根系吸附的Mn(II)主要以交换态存在；发现水稻根表铁膜及根系吸附的铝氧化物导致根系表面负电荷减少，根系对养分的吸附和吸收减小。本研究为土壤电化学开辟根/ 土界面电化学新学术领域，研究结果将为可变电荷土壤的养分管理和土壤环境保护提供科学指导。