Immobilization of heavy metals in rhizosphere soils : formulation of phytostabilization technology

为了在靶场土壤中制定成功的植物稳定策略，了解重金属如何在分子水平上在根际土壤中固定是至关重要的。本研究旨在探讨不同植物根际土壤中Pb形态的改变，以及Pb颗粒在根际土壤中的溶解度及其对土壤生态系统的影响。利用扩展x射线吸收精细结构（EXAFS）光谱和化学萃取技术研究了5种不同植物根际土壤中铅的形态和溶解度。EXAFS分析表明，铅主要以PbCO_3形式存在，Pb吸附于有机质中，Pb吸附于成土白云石和/或水合铁中。块状土壤和根际土壤的EXAFS光谱比较表明，Pb在精细结构上存在显著差异，表明根际过程对Pb进行了修饰。变性梯度凝胶电泳结果表明，污染土壤中植物的生长使细菌种群更加丰富，根际土壤的总体条带剖面比对照土壤亮。pH值为~7的土壤细菌多样性增强。

To formulate successful phytostabilization strategies in a shooting range soil, understanding how heavy metals are immobilized at the molecular level in the rhizosphere soil is critical. The objectives of this study were to investigate i) how Pb speciation was modified in the rhizosphere soils of various plant species, and ii) solubility of Pb pellet in rhizosphere and subsequent impacts on soil ecosystems. Lead (Pb) speciation and solubility in rhizosphere soils of five different plant species were investigated using extended X-ray absorption fine structure (EXAFS) spectroscopy and chemical extraction. The EXAFS analysis indicated that Pb occurred as PbCO_3, Pb sorbed to organic matter, and Pb sorbed to pedogenic birnessite and/or ferrihydrite in the bulk soil. Comparison of the EXAFS spectra between bulk and rhizosphere soils demonstrated notable differences in fine structure, indicating that Pb species had been modified by rhizosphere processes. Denatured gradient gel electrophoresis demonstrated that Plant growth in the contaminated soil appeared to enrich bacterial populations since the general band profile exhibited in the rhizosphere soil was brighter than the control soil. Bacterial diversity was enhanced in the soil with the pH value of～7.