污染地下水零价铁原位反应带修复技术:理论·应用·展望

ZVI-IRZ(零价铁原位反应带)是一种新兴的地下水原位修复技术,具有工程造价低、施工简单、环境扰动小、修复效果好等优势, 而ZVI(零价铁)自身理化性质、场地的水文地球化学特征以及场地的污染状况等是影响修复效果的主要因素. 当前的研究内容主要包括IRZ(原位反应带)中ZVI的反应活性、稳定性、迁移性、生物毒性以及注入方式等方面. 在修复工程中存在的问题主要体现在:①ZVIs(细粒径零价铁)在含水介质中的迁移性较差,并且多采用Fe2+、pH等间接指标考察含水层中ZVIs的分布情况；②ZVIs表面钝化而诱发介质反应活性下降；③ZVIs的潜在生物环境效应尚不明确. 因此,需要加强对ZVIs表面改性手段、作用机制、老化特性、使用寿命、解钝化及钝化抑制技术等方面的理论与应用研究,还应关注ZVIs在环境中的归趋、转化机制和暴露路径,建立生态系统尺度上的评估体系； 同时,在实际应用中,需要在系统评估污染场地水文地质条件的基础上,加强对注入含水层中ZVIs及其反应产物的原位监测技术研发和监测体系完善. 

Development of a Zero-Valent Iron-Based In-situ Reactive Zones Technique for Remediation of Contaminated Groundwater

Abstract: A zero-valent iron (ZVI)-based in-situ reduction zone (IRZ) is a promising technique and an effective alternative to PRB (permeable reactive barrier) for remediation of contaminated groundwater. IRZ has received significant attention due to its low engineering cost, simple construction, fewer disturbances to the environment and high efficiency in degrading a broad range of contaminants found in aquifer systems. Based on a comprehensive literature review, it was determined that remediation efficiency is influenced by the physical and chemical properties of the ZVI, hydrogeochemical characteristics and contamination situation of the site. Developments in several key aspects are helpful for understanding its advantages and uncertainties. The areas include reactivity with a wide spectrum of organic and inorganic contaminants, methods to enhance the colloidal stability and mobility of ZVIs in subsurface environments, eco-toxicological impact of ZVIs and engineering measures. However, some problems exist when using the technique:1) poor mobilization of injected ZVIs in the aquifer; the placement of injected ZVIs during groundwater remediation monitored by indirect methods, such as Fe²⁺ and pH; 2) reduced reactivity of ZVIs caused by a series of corrosion reactions and precipitated amorphous and crystalline iron corrosion products; and 3) insufficient knowledge about potential biological and environmental effects. Given that, more efforts should be made to address the issues of surface modification, reaction mechanism, passivation behavior, longevity assessment, passivation rejuvenation and prevention. Moreover, the fate, transformation and exposure paths should be revealed, and ecosystem assessment should be established. For engineering applications, the hydrogeological conditions of the contaminated site should be pre-evaluated, and an advanced monitoring technical system should be developed to follow the fate of injected ZVIs particles and their corrosion products.