人工加强地下环境产生羟基自由基及其对PFOA迁移转化的影响

Perfluorooctanoic acid (PFOA) has been detected in various environmental media and even in human beings due to its extensive use in manufacturing industrial, medical and commercial products. It is the subject of increasing regulatory interest because of its potential to bioaccumulate, growing evidence of its toxicity to animals, and environmental persistence. Unlike most other persistent and bioaccumulative organic pollutants, PFOA is water-soluble, and do not bind well to soil or sediments, thus, it migrates easily and causes serious contamination to groundwater. Radical Hydroxyl (•OH A very strong is reactive oxygen species whose oxidizing ability is Second only to fluorine in the environment (oxidation potential: 2.8 V). Due to of its strongly Oxidizing ability, it can oxidize almost all of the organics and redox- active elements, contributing of their transformation. For a long time, sunlight is believed of be essential for •OH production in natural environment until 2012 when oxygenation of reduced aquatic of dissolved organic matter(DOM) and iron was ported to produce •OH. And then oxygenation was found can produce abundant •OH in subsurface environment. However, little is known about of the production of •OH from the interaction of O2 and subsurface environments along with the associated Impact environmental impact. Overall, this study is to investigate the potential of hydroxyl radical generation active by oxygen in subsurface environment. and how artificial enhancement of hydroxyl radical generation could affect the transport and transformation of PFOA in the underground environment. This study will provide a new option of in-situ control and remediation technologies for organic contamination.

全氟辛酸(PFOA)作为一种新型有机污染物，在环境介质中被广泛检出，因其具有生物毒性，潜在的生物蓄积性和环境持久性而广泛的引起了科学家的注意。PFOA水溶性好，迁移转化速度快，容易造成地下水的严重污染。已有的研究表明微生物、沉积物和有机质对PFOA的迁移转化影响作用甚微，而羟基自由基能氧化PFOA，使其转化为更短链的全氟化合物。地表环境中产生的羟基自由基对物质碳循环及污染物的迁移转化存在非常重要的意义，而地下水环境中产生羟基自由基这一现象及意义长期被忽略。本研究主要探讨地下还原环境介质在氧气的作用下产生羟基自由基的潜能，并通过人为强化增加地下环境中产生羟基自由基的量，研究地下水环境中产生羟基自由基这一化学反应过程对在地下环境中PFOA迁移转化的影响。本研究人为强化地下水中羟基自由基的反应过程，并利用其氧化性影响地下水中难降解有机物的迁移转化，将对地下水有机污染的防控和修复提供新的思路。

构建地下水沉积物氧化反应体系，概化了地下水产生羟基自由基过程，其中高铁质黑产羟基自由基的量累积可达27.6μM。建立地下含水层氧化产生羟基自由基反应模型，评价了地下环境产生自由基的条件，即沉积物中具有还原性物质，处于氧化和还原交替的地下水位波动带。地下水沉积物环境氧化产生羟基自由基受地下水中氧气含量，还原性铁含量以及有机质的含量的影响。通过模拟实验，评价了地下环境产生羟基自由基的可持续性，结果显示溶液态和固态的还原性物质都对产羟基自由基有贡献，固相还原性物质是地下水环境氧化持续产氢的主要因素。柱实验模拟了PFOA在不同环境中迁移的情况，PFOA的迁移受环境中离子强度，有机质和还原性物质含量共同影响。较高浓度二价铁环境中PFOA的滞留明显。通过人工加强地下环境产羟基自由基实现降低PFOA在水环境的迁移性。地下水中的氯离子、碳酸根和有机质会竞争地下水中产的生的自由基。我们研究显示，饮用地下水中已经检出了多种全氟化合物。本研究利用人工加强的方式，让有利的地下环境产生羟基自由基，加速PFOA的矿化，是地下水中全氟化合物控制的一种新思路。