电动力学介导下超富集植物根际土壤铅形态演变及富集特征变化机制

Phytoremediation (PR) of Lead (Pb) from contaminated soil is often difficult due to low solubility and biological activity of Pb. Electrokinetic (EK) can change the speciation and space distribution of Pb in contaminated soil. So EK is considered one of the greatest potential strengthening technologies to improve the Pb accumulation function of plants. However, how EK affect the Pb speciation evolution in rhizosphere soil and the variation mechanisms of Pb accumulation is still unclear. In this project, the Pb contaminated red soil around a lead and zinc mine in Yunnan Province and an indigenous hyperaccumulator (Silene viscidula Franch) are selected as the studying materials. The electrokinetic-assisted phytoremediation (EKAP) pot and water culture studies and leaching desorption of Pb contaminated soil will be conducted. The research objects include: (1) To clarify the effects of the interaction of EK and hyperaccumulator on the interface chemical properties of rhizosphere soil particles, root conformation, the rhizosphere secretion characteristics of low-molecular-weight organic acids (LMWOAs), and chemical properties water filled pore space. (2) To parse the relationship between the variation of physical and chemical properties of soil particles and water medium of rhizosphere soil and the Pb desorption and distribution under EK mediated, and between the redistribution of speciation and space of Pb in rhizosphere soil and Pb characteristics, flowing the main research idea of “EK - rhizosphere secretion characteristics - physical and chemical properties of soil particles and interflows - Pb desorption and redistribution”. (3) To reveal the affect mechanisms of EK on the evolution of Pb speciation in rhizosphere soil and Pb hyperaccumulative characteristics. The results will enrich understanding the interaction mechanisms of EK and plants, and promote a consummating the theory and application of EKAP.

污染土壤铅（Pb）溶解度和生物活性低，导致Pb植物修复（PR）难度较大。电动力学（EK）因可改变土壤Pb形态及空间分布，提升Pb植物富集效率，是最具潜力的强化植物修复技术之一，但电动力学是怎样影响根际土壤铅形态演变及铅富集变化机制，还不清楚。本项目拟以云南铅锌矿区Pb污染红壤和本土超富集植物滇白前，开展Pb污染土壤电动力学辅助植物修复（EKAP）盆栽、水培和淋溶解吸等试验，阐明电动力学与超富集植物互作对根际土壤界面化学性质、根系形态、根际LMWOAs分泌特征和土壤孔隙水化学性质的影响。以“电动力学—根际分泌特征—水土介质理化性质—Pb解吸再分布”为主线，解析电动力学介导下根际土壤水土介质理化性质变化与Pb解吸分配，Pb形态及空间再分布行为与铅富集特征的关系，揭示电动力学影响植物根际土壤Pb形态演变及其超富集特征的机制。研究结果能丰富EK与超富集植物互作机制认识，推动EKAP理论完善及应用。

污染土壤铅（Pb）溶解度和生物活性低，导致铅植物修复（PR）难度较大。电动力学（EK）因可改变土壤铅形态及空间分布，提升铅植物富集效率，是最具潜力的强化植物修复技术之一，但电动力学是怎样影响根际土壤铅形态演变及铅富集变化机制，还不清楚。本项目以云南铅锌矿区铅污染红壤和重金属超富集植物伴矿景天为研究对象，开展铅污染土壤电动力学辅助植物修复（EKAP）盆栽、水培和淋溶解吸等试验，阐明电动力学与超富集植物互作对根际土壤界面化学性质、根系形态、根际LMWOAs分泌特征和土壤孔隙水化学性质的影响。研究表明，电动力学显著改变水土介质pH，但阴极区碱化幅度显著小于阳极区酸化程度，伴矿景天耕作能有效缓解电场诱导的酸碱化趋势。电动力学作用显著提升土壤有效养分、活性有机质、阳离子交换量和孔隙水无机离子强度等指标含量，这些性质变化使得土壤中铅由可还原态和可氧化态向弱酸可提取态转化，电压梯度1.0V/cm铅弱酸可提取态含量提高达8.3倍。周期换向直流电场诱导铅逐渐累积分布于土壤中间区，电动力学因电位极化活化与间接溶解两种典型作用机制加快根际土壤水土介质重金属解离与交换，有效促进伴矿景天吸收累积土壤铅、镉，其地上/地下部分富集量均明显增加，但其铅的转运系数与电压梯度无显著相关性。伴矿景天生理生长特征对电场反馈敏感，电压梯度0.25~0.5V/cm时生物量增加显著，1.0V/cm时生物量与根系形态已受到明显抑制。电动力学介导下根际土壤水土介质pH、活性有机质、阳离子交换量和无机离子强度等理化指标变化与土壤铅形态转化、解吸分配存在很大相关关系。初步揭示了土壤颗粒表面电位极化活化直接作用和间接提高孔隙水铅溶解能力，可能是电动力学影响植物根际土壤铅形态转变及促进铅植物吸收富集的主要地下部机制。研究结果能丰富EK与超富集植物互作机制认识，推动EKAP理论完善及应用。