【作者】 刘琼；

【导师】 王广才； 郭华明；

【作者基本信息】 中国地质大学(北京) ， 环境科学与工程， 2012， 博士

【摘要】 世界上很多国家和地区都分布有高砷地下水。在缺少替代水源的情况下，当地居民长期饮用高砷地下水，将带来很大的健康隐患。为保证这些地区居民的饮用水安全，必须先对高砷水进行处理。生物修复法是目前除砷领域研究的热点之一，而大量耐砷微生物的发现和耐砷机理研究又为生物法除砷的发展提供了新的思路。本文分别选取了好氧铁氧化菌GE-1和厌氧铁氧化菌Strain 2002作为研究对象，利用室内实验研究了这两种菌的Fe(Ⅱ)氧化能力和耐砷性能，探讨了Fe(Ⅱ)氧化、铁沉降原因及耐砷机理。在此基础上，初步试验了这两种菌的除砷效果，并研究了菌存在对菱铁矿除砷系统的影响。好氧铁氧化菌GE-1分离自浸泡生锈铁丝的自来水，属于假单胞菌。单菌体为无色杆状菌，长为1-5μm。GE-1生长升高环境pH，并分泌出大量胞外酶，都有助于Fe(Ⅱ)的氧化和铁的沉降，最终生成结晶度较低的水铁矿。GE-1有很大的耐砷潜力，在As(Ⅲ/Ⅴ)浓度高达100 mg/L的水环境中依然能正常生长。厌氧铁氧化菌Strain 2002是前人从淡水湖沉积物中分离出的。单菌体为无孢子、有鞭毛的杆状菌，长为1-4μm。Strain 2002还原硝酸盐时，能同时以乙酸盐和Fe(Ⅱ)作为电子供体，导致Fe(Ⅱ)氧化。其Fe(Ⅱ)氧化和铁沉降的产物为包含菱铁矿、纤铁矿和针铁矿等在内的Fe(Ⅱ)和Fe(Ⅲ)混合矿物。Strain 2002耐As(V)能力要高于耐As(Ⅲ)能力，当水环境中的As(Ⅲ)浓度为2000μg/L时，Strain 2002的生长速度就会受到明显影响。在高砷环境中，GE-1和Strain 2002都会逐渐收缩。当砷环境中无铁时，它们都不能通过吸收或生物吸附来降低砷的浓度，也不能改变砷的价态。当砷环境中有Fe(Ⅱ)时，它们氧化Fe(Ⅱ)、沉降铁的产物朝着结晶更差、颗粒更细小的方向转化。生成的铁沉淀能通过吸附或共沉降作用来除砷，效果很好。在菱铁矿除砷系统中加入GE-1和Strain 2002后，由于引入了大量细菌，会造成吸附点位的减少和菱铁矿颗粒表面电荷的改变，不利于砷的去除。本文取得成果为建立耐砷铁氧化菌的除砷适用技术和研究砷的迁移转化规律提供了理论基础。更多还原

【Abstract】 High arsenic groundwaters have been found in many countries and areas. People,exposed to high-arsenic groundwater due to limited alternative water resources, mayhave severe health problems. Therefore, arsenic removal should be conducted forensuring the safety of drinking water. In recent years, bioremediation has receivedmuch attention on arsenic removal from aqueous solution. Moreover, a number ofmicroorganisms which survive in high As(III/V) environment have been reported.The findings of arsenic-resistant microorganisms and mechanism on their arsenictolerance give new ideas on arsenic bioremediation.This study investigated the potential of Fe(Ⅱ)-oxidizing bacteria in arsenictolerance and removal in aqueous environment. Aerobic Fe(Ⅱ)-oxidizing bacteriaGE-1 and anaerobic Fe(Ⅱ)-oxidizing bacteria Strain 2002 were selected. Mechasiamof Fe(Ⅱ) oxidization and Fe precipitation by theses bacteria were also revealed.Aerobic Fe(Ⅱ)-oxidizing bacteria GE-1 were isolated from the batch of tap waterand rusty iron wires. This strain was colorless and rod-shaped (1-5μm), belonging toPseudomonas sp. according to 16S rRNA gene sequences. The growth of GE-1increased solution pH and secreted extracellular enzymes, which contributed to Fe(Ⅱ)oxidization and Fe precipitation. XRD (X-ray diffraction) patterns indicated that Fedeposits by GE-1 in Fe-rich culture medium were low-crystallized ferrihydrites. GE-1had high arsenic tolerance, which even survived and propagated in 100 mg/L As(III/V)solutions.Anaerobic Fe(Ⅱ)-oxidizing bacteria Strain 2002 were rod-shaped (1-4μm),non-spore forming and flagellated, which were isolated from freshwater lakesediments by Weber et al. This strain was capable of utilizing acetate and Fe(Ⅱ) aselectron donor to reduce nitrate under heterotrophically growth conditions.FE-SEM/EDS (Field Emission Scanning Electron Microscope/Energy DispersiveSpectrometer) results showed that Fe deposits by Strain 2002 in Fe-rich culturemedium were mixed Fe(Ⅱ) and Fe(III) minerals containing siderite, lepidocrocite andgoethite. Strain 2002 had higher tolerance of As(V) than As(III). The growth wasobviously slow in 2000μg/L As(III) condition. In high As(III/V) environment, morphological characteristics of both strainsshowed similar changes, e.g., shrinking of long bacillus. Besides, with the absence ofFe(Ⅱ) and Fe(III), both strains neither removed arsenic nor change the species ofarsenic. With the presence of Fe(Ⅱ), these strains led to oxidization of Fe(Ⅱ) andprecipitation of Fe minerals, and produced smaller and less crystalline minerals.Adsorption on and co-precipitation with these biogenic Fe minerals greatlycontributed to high arsenic removal efficiency of Fe(Ⅱ)-oxidizing bacteria.The effect of GE-1 and Strain 2002 on arsenic removal by siderite were alsostudied when siderite was adopted as the adsorbent to remove arsenic. Results showedthat due to the introduction of bacteria into solution, adsorption sites and surfacecharge of siderite changed, which exerted negative influences on arsenic removal.These findings provided theoretical supports on developing applicable arsenicbioremediation by arsenic-resistant Fe(Ⅱ)-oxidizing bacteria and studyingtransformation and geological cycle of arsenic in nature.更多还原