AM真菌对不同粒径土壤中Pb形态分布及根际转化的作用机制

Soil lead (Pb) pollution has become a global environmental issue that requires to be solved urgently and effectively. The speciation and transformation of Pb are the premise and basis for the analysis of its bioavailability, migration and remediation mechanisms. The combination of plant and arbuscular mycorrhiza (AM) as a new approach can promote the efficiency of phytoremediation, which has gradually attracted widespread interests, but the biological mechanism of AM fungi on speciation distribution and rhizosphere-induced transformation of Pb remains to be revealed. The project plans to use a split root system with four chambers as our culture container, using laser particle size analyzer, scanning electron microscopy, X-ray absorption fine structure spectra and other advanced methods to analyze the impact of AM fungi on composition of soil particle size fraction, and then clarify the distribution of Pb speciation in different particle size fractions. Further study will conduct to compare the features of Pb adsorption mode, product configuration and group coordination at the micro-surfaces of root-soil-mycelium. The kinetic characteristics of Pb adsorption-desorption in different soil particle size fractions will be also determined. Finally, a comprehensive analysis of the relationships among them and AM fungi colonization characteristics (colonization rate, etc.), the related environmental factors (soil pH, etc.) will carry out to reveal the kinetic and molecular mechanisms of AM fungi on Pb speciation distribution and rhizosphere-induced transformation. The project will deeply improve our understanding the mechanism of bioremediation, provide scientific basis for the development of effective remediation technologies and offer policy support to protect soils from contamination by Pb.

土壤铅（Pb）污染是当前亟待解决的世界性环境问题。Pb的形态与转化是解析其生物可给性、运移机制及污染修复机理的前提和基础。植物－菌根（AM）联合共生体作为强化植物修复的新途径逐渐成为国内外研究热点，但AM真菌影响土壤Pb形态分布及根际转化的生物学机理有待揭示。本项目拟采用四室分根隔网系统，利用激光粒度分析仪、扫描电镜能谱分析、X射线吸收精细结构光谱等研究手段，分析AM真菌对土壤粒径组成的影响，明确土壤Pb形态分布规律；比较不同粒径土壤中Pb在根－土－菌丝微界面的吸附方式、产物构型及基团配位等特征，明晰不同粒径土壤中Pb吸附－解吸的动力学过程；分析上述结果与AM真菌定殖特征（侵染率等）及相关环境因子（根际pH等）的关联性，揭示AM真菌对不同粒径土壤中Pb形态分布及根际转化的动力学及分子机制。研究成果将促进对生物修复机理的深入理解，并为发展土壤Pb污染高效修复途径及制订相关措施提供科学依据。

土壤重金属污染问题日趋突出，已成为全球面临的一项严重的环境问题。Pb的形态与转化是解析其生物可给性、运移机制及污染修复机理的前提和基础。丛枝菌根（AM）真菌作为强化植物修复的新途径逐渐成为国内外研究热点，但AM真菌调控土壤Pb形态分布及根际转化的机理有待深入研究。本项目利用分根隔网系统，明晰了AM真菌对重金属Pb植物修复效率的提高作用；确定了AM真菌对土壤粒径的影响及团聚体稳定性的促进作用；进一步以根际土壤区域为重点，证实了AM真菌和土壤粒径的交互作用对有机结合态Pb含量的显著影响；进一步比较了根际土壤、菌丝体和孢子中的Pb元素含量，证明了AM真菌的孢子对Pb的富集能力是菌丝体的3.91倍；然而，AM真菌对土壤Pb的分子形态影响不显著；综合运用结构方程模型与随机森林模型分析，揭示了AM真菌既可以通过影响土壤理化性质，也可以影响土壤团聚体稳定性及GRSP调控根际土壤Pb形态的转化。本研究阐明了AM真菌在调节土壤Pb形态转化的重要作用，并强调土壤团聚体及GRSP在此过程中所发挥的核心作用。研究成果将促进对生物修复机理的深入理解，并为发展土壤Pb污染高效修复途径及制订相关措施提供科学依据。