共查询到18条相似文献，搜索用时 109 毫秒
1.
微生物参与铁氧化物矿物的还原性溶解是高砷地下水形成的关键过程,其中具有砷还原功能的微生物如何参与含水层砷释放的生物地球化学过程亟待研究.利用从江汉平原典型高砷含水层中厌氧条件下分离出的四株细菌(Citrobacter sp.JH-1、Clostridium sp.JH-6、Exiguobacterium sp.JH-13、Paenibacillus sp.JH-33),通过室内厌氧模拟培养实验,查明其砷、铁还原能力,并通过分别与铁氧化物矿物及原位沉积物共同培养,探究原位含水层微生物参与的砷释放机理.结果表明:四株细菌均具有厌氧条件下砷、铁还原功能,Citrobacter sp.JH-1砷还原能力最强,96 h内还原的As(Ⅴ)浓度为2.22 μmol/L.其中Citrobacter sp.JH-1不仅可在厌氧和有氧条件下还原溶液中的As(Ⅴ),还可在厌氧条件下还原溶液中的Fe(Ⅲ)和无定型的水铁矿,在与含水层沉积物共培养12 d后,沉积物中铁与砷的释放量分别为510 mg/kg及1 150 μg/kg.江汉平原含水层中的原位微生物兼具砷/铁还原功能,在厌氧条件下可还原沉积物中的铁氧化物矿物并促进砷的释放,为深入揭示高砷地下水成因机理与地下水砷污染的防控提供重要科学依据. 相似文献
2.
硫在铁和砷的生物地球化学循环中发挥着重要作用,但地下水系统中硫循环的中间产物S(0)对细菌转化铁和砷的影响尚不清楚.采用室内模拟实验,研究硫参与下细菌D2201对液相和载砷针铁矿中Fe(III)和As(V)的还原作用.结果表明:细菌D2201具有很强的铁还原能力,可以将液相中74%的Fe(III)还原;加入硫后,细菌还原S(0)产生的S(-II)使铁还原率提高到94%.但是,硫没有明显影响细菌对砷的还原.在实验初期,细菌明显加速了载砷针铁矿的还原,最终还原释放到液相中的Fe(II)浓度为32.12 μmol/L;硫的加入增强了细菌对载砷针铁矿的还原,还原溶解的Fe(II)增加至284.13 μmol/L,同时,砷的释放量也增加了1.6倍.这些结果表明硫显著促进了细菌对针铁矿的还原溶解并加速砷的释放.XRD和SEM-EDS结果显示,细菌还原针铁矿但不改变其矿相,而硫的加入也仅使矿物发生一定程度的团聚,并没有使其转变为其他矿物,也未导致砷的再吸附. 相似文献
3.
反硝化菌的耐砷驯化及其对水铁矿吸附态砷迁移转化的影响 总被引：2，自引：0，他引：2
采集缺氧活性污泥进行室内微生物驯化,培养耐砷反硝化菌。把耐砷反硝化菌、营养液和吸附As(V)的水铁矿在厌氧条件下培养,研究反硝化菌代谢作用下,系统中Fe、Mn、NO3-和As形态的动态变化。结果表明,缺氧活性污泥中的反硝化菌具有一定的耐砷能力。在砷含量500μg/L以内,其反硝化强度基本不受砷的影响。在吸附有砷的水铁矿体系中,反硝化菌所产生的反硝化作用可导致溶液中NO3-含量的降低、Fe含量的升高、As含量降低,且As(III)所占比例增加。这说明,体系中水铁矿的还原性溶解和As(V)的还原性解吸已经发生。As含量降低的原因是,在培养体系中水铁矿的含量高,Fe的释放量只占很小比例,表层水铁矿被还原后,在次表层形成新的水铁矿吸附位,这种新吸附位不仅可以吸附溶液中已经存在的As,而且能够再吸附由于还原性溶解和解吸所释放出的As。 相似文献
4.
为了研究厌氧微生物作用下沉积物中砷的形态转化及固液界面的分配过程对砷的环境行为与归趋的影响,通过采集锦州湾清洁沉积物进行负载砷,利用微生物培养与非生物培养实验,对比研究厌氧微生物作用下砷铁硫共还原条件下污染体系中砷的环境行为与归趋。实验结果表明在培养的42 d周期内,液相的总砷量首先砷浓度保持降低趋势,而后再次升高。在培养第3~7 d时液相的As5+迅速被还原,约26%的溶解态砷从液相移除,97%以上的As5+被还原为As3+。同时微生物作用下固相中90%以上铁氧化物矿物逐渐转化为次生的亚铁矿物,固相中结晶态铁氧化物发生明显活化,而硫酸盐还原产物硫离子综合调控体系中游离的亚铁离子和As3+。因此,厌氧微生物还原条件下,砷,铁,硫同步发生还原,硫离子调控体系中砷和铁环境行为,硫化亚铁成为亚铁矿物的主要形态,硫化砷是砷的主要归趋。 相似文献
5.
地下水中铵根、砷、溶解铁的共存是一个普遍现象。它们之间发生强烈的相互作用,并影响地下水系统的氮循环和砷迁移转化。文章在系统总结地下水氮循环过程及影响因素、地下水氮循环功能微生物及特征、地下水砷富集的水文地球化学过程等国内外研究现状的基础上,深入分析了地下水系统中的氮循环过程（硝化、反硝化、铁铵氧化、厌氧铵氧化、硝酸根异化还原产铵等）对地下水砷迁移转化的影响,总结出含水层中铁氧化物和溶解态Fe(II)的动态转化是氮循环影响地下水中砷迁移转化的重要桥梁。据此提出不同氧化还原环境的含水层中氮循环过程、地下水氮循环与砷迁移转化耦合机理、Fe(III)-Fe(II)的循环-地下水氮循环-砷迁移转化之间的相互作用过程、地表水-地下水相互作用带氮-铁-砷的循环过程及其对人类活动的响应等是今后该领域需要关注的重要科学问题和主要发展趋势。这些科学问题的解决不仅有利于识别地下水中氮的来源和迁移转化,而且有利于提高对高砷地下水富集机理的整体认识。 相似文献
6.
微生物对砷的地球化学行为的影响——暨地下水砷污染机制的最新研究进展 总被引：7，自引：0，他引：7
砷在自然界中广泛存在，近年来砷污染对人类健康造成的危害越来越引人关注。微生物在自然界中长期与砷共存，进化出不同的生物转化机制，在自然水体中微生物主要参与砷的不同氧化价态之间的转化过程，即As(V)和As(III)之间的氧化还原作用。砷酸盐异化还原菌（Dissimilatory Arsenate Respiring Prokaryote, DARP）可以将As(V)还原为As(III)，化能自养亚砷酸盐氧化菌（Chemoautotrophic Arsenite Oxidizer, CAO）和异养亚砷酸盐氧化菌（Heterotrophic Arsenite Oxidizer, HAO）可以将As(III)氧化为As(V)。这些砷代谢微生物在分类和代谢能力上都具有很大的多样性，它们广泛参与了砷的生物地球化学循环的关键步骤，对特定环境条件下砷的地球化学行为产生重要影响，进而参与了砷的全球循环。在盐碱湖莫诺（Mono）湖中砷的不同价态分层存在，CAO与DARP的紧密偶联共同参与了莫诺湖中的砷的地球化学循环。在孟加拉三角洲的地下含水层中，微生物参与了将砷从固相迁移到水相的关键步骤，最终导致了地下水中的砷污染。 相似文献
7.
砷是土壤中重要的(类)重金属污染物,其毒性主要取决于在环境中的形态及氧化还原状态。游离态Fe(Ⅱ)(Fe(Ⅱ)_(aq))驱动铁(氢)氧化物晶相重组过程是土壤铁循环的重要组成,对土壤中重金属的吸附、固定、钝化等环境行为有重要影响。本研究采用~(57)Fe稳定同位素示踪方法研究厌氧条件下Fe(Ⅱ)_(aq)驱动针铁矿晶相重组过程中砷的氧化还原及形态变化过程。结果显示,在只有针铁矿存在的对照处理中,针铁矿本身对As(Ⅲ)没有氧化作用,但83%的As(Ⅲ)被吸附到针铁矿表面。在Fe(Ⅱ)_(aq)和针铁矿共存体系中,Fe(Ⅱ)_(aq)可与针铁矿中结构态Fe(Ⅲ)发生铁原子交换,As(Ⅲ)的存在降低了铁原子交换速率。同时,在Fe(Ⅱ)_(aq)驱动针铁矿晶相转化过程中,77%的As(Ⅲ)被氧化成As(Ⅴ),As活性降低。另外,部分吸附在针铁矿表面的As(Ⅲ)和氧化转化后的As(Ⅴ)通过针铁矿的晶格单元包裹或取代Fe结构位的形式被针铁矿结构化固定,从而进一步降低了As的活性。 相似文献
8.
含水层沉积物中含铁矿物的特征与活性会影响砷的迁移转化行为。通过内蒙古含水层沉积物含铁矿物的溶解、还原动力学实验,研究了沉积物含铁矿物特征和活性及其与砷运移的关系。结果表明,沉积物中具还原活性的铁氧化物总量(m0)与岩性有关,细砂为52 μmol/g,黏土为45 μmol/g。初始还原速率k′均在10-5 s-1的数量级。表征活性均匀度的参数γ值介于合成铁氧化物矿物和表层沉积物之间。沉积物中Fe(Ⅲ)氧化物的还原活性主要介于人造纤铁矿与针铁矿的活性水平范围内。沉积物中可能存在两类活性水平不同的Fe(Ⅲ)氧化物。As更倾向于吸附在活性较强的Fe(Ⅲ)氧化物上。还原环境中,活性较强的Fe(Ⅲ)氧化物的还原性溶解,促进了沉积物中砷的释放。 相似文献
9.
《吉林大学学报(地球科学版)》2015,(Z1)
<正>水体中砷的迁移转化行为受其赋存形态影响。一般有氧水体和缺氧水体中,常见的无机砷形态为砷酸根(HAs O42-,H2As O4-和As O43-)或亚砷酸(H3As O3);在一些含硫的缺氧水体中,元素硫参与砷的地球化学循环,与之形成含砷硫化物沉淀或者可溶的硫代砷(thioarsenic species)。硫代砷形态十分复杂,按照砷的价态可分为硫代As(V)(thioarsenate,H3AsVOx S4-x,x=0~3)和硫代As(III)(thioarsenite,H3AsIIIOx S3-x,x 相似文献
10.
通过两种还原型微生物铁还原菌JF-5和硫酸盐还原菌SRB对模拟酸矿废水中Fe~(3+)和SO~(2-)_4的还原作用合成纳米FeS,并将该生物纳米FeS包覆在灰岩表面,以提高灰岩可渗透反应墙(PRBs)对酸矿废水中砷的去除能力。通过批吸附实验研究As(Ⅴ)的静态吸附机理,柱实验研究As(Ⅴ)在包覆灰岩柱中的动态吸附和迁移,结果表明,包覆层生物FeS粒径为纳米级,并呈现一定晶形,能有效提高灰岩表面的比表面积和对As(Ⅴ)的吸附能力,红外光谱分析表明化学吸附为主要吸附机制;生物纳米FeS包覆灰岩静态吸附实验最大吸附量为187.46μg/g,达到纯灰岩吸附量(6.64μg/g)的30倍;JF-5和SRB形成的生物包覆吸附性质优于SRB和Fe(Ⅱ),二者对As(Ⅴ)的吸附能力都远大于纯灰岩对As(Ⅴ)的滞留能力。 相似文献
11.
Arsenic repartitioning during biogenic sulfidization and transformation of ferrihydrite 总被引：4，自引：0，他引：4
Iron (hydr)oxides are strong sorbents of arsenic (As) that undergo reductive dissolution and transformation upon reaction with dissolved sulfide. Here we examine the transformation and dissolution of As-bearing ferrihydrite and subsequent As repartitioning amongst secondary phases during biotic sulfate reduction. Columns initially containing As(V)-ferrihydrite coated sand, inoculated with the sulfate reducing bacteria Desulfovibrio vulgaris (Hildenborough), were eluted with artificial groundwater containing sulfate and lactate. Rapid and consistent sulfate reduction coupled with lactate oxidation is observed at low As(V) loading (10% of the adsorption maximum). The dominant Fe solid phase transformation products at low As loading include amorphous FeS within the zone of sulfate reduction (near the inlet of the column) and magnetite downstream where Fe(II)(aq) concentrations increase; As is displaced from the zone of sulfidogenesis and Fe(III)(s) depletion. At high As(V) loading (50% of the adsorption maximum), sulfate reduction and lactate oxidation are initially slow but gradually increase over time, and all As(V) is reduced to As(III) by the end of experimentation. With the higher As loading, green rust(s), as opposed to magnetite, is a dominant Fe solid phase product. Independent of loading, As is strongly associated with magnetite and residual ferrihydrite, while being excluded from green rust and iron sulfide. Our observations illustrate that sulfidogenesis occurring in proximity with Fe (hydr)oxides induce Fe solid phase transformation and changes in As partitioning; formation of As sulfide minerals, in particular, is inhibited by reactive Fe(III) or Fe(II) either through sulfide oxidation or complexation. 相似文献
12.
Mining and metallurgical processing of gold and base metal ores can lead to the release of arsenic into the aqueous environment as a result of the weathering and leaching of As-bearing minerals during processing and following disposal. Arsenic in process solutions and mine drainage can be effectively stabilized through the precipitation of ferrihydrite. However, under anaerobic conditions imposed by burial and waste cover systems, ferrihydrite is susceptible to microbial reduction. This research, stimulated by the paucity of information and limited understanding of the microbial reduction of arsenical ferrihydrite, was conducted on synthetic adsorbed and co-precipitated arsenical 6-line ferrihydrite (Fe/As molar ratio of 10/1) using Shewanella sp. ANA-3 and Shewanella putrefaciens CN32 in a chemically defined medium containing 0.045 mM phosphate concentration. Both bacteria were equally effective in their reducing abilities around pH 7, resulting in initial rates of formation of dissolved As(III) of 0.10 μM/h for the adsorbed, and 0.08 μM/h for the co-precipitated arsenical 6-line ferrihydrite samples. The solid phases in the post-reduction samples were characterized by powder X-ray diffraction (XRD), micro-XRD, scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron microprobe and X-ray absorption spectroscopy (XAS) techniques. The results indicate the formation of secondary phases such as a biogenic Fe(II)–As(III) compound, akaganeite, goethite, hematite and possibly magnetite during bacterial reduction experiments. Holes and bacterial imprints measuring about 1–2 μm were observed on the surfaces of the secondary phases formed after 1200 h of reduction. This study demonstrates the influence of Fe and As reducing bacteria on the release of significant concentrations of more mobile and toxic As(III) species from arsenical 6-line ferrihydrite, more readily from the adsorbed than from the co-precipitated ferrihydrite. 相似文献
13.
Reductive dissolution of arsenic-bearing ferrihydrite 总被引：2，自引：0，他引：2
Jasmine J. Erbs Brian C. Reinsch Gregory V. Lowry Subir K. Banerjee 《Geochimica et cosmochimica acta》2010,74(12):3382-8833
Ferrihydrites were prepared by coprecipitation (COP) or adsorption (ADS) of arsenate, and the products were characterized using solid-state methods. In addition, the kinetics of reductive dissolution by hydroquinone of these well-characterized materials were quantified. Characterization and magnetism results indicate that the 10 wt% As COP ferrihydrite is less crystalline and possibly has smaller crystallite size than the other ferrihydrites, which all have similar crystallinity and particle size. The results from reductive dissolution experiments show similar reaction rates, reaction mechanism, and activation energy for ferrihydrite precipitated with or without added arsenate. However, a marked decrease in reactivity was observed for 10 wt% As ADS ferrihydrite. The decrease is not attributed to differences in activation energy but rather the preferential blocking of active sites on the ferrihydrite surface. Results demonstrate that arsenic may be released by the reductive dissolution of arsenic-bearing ferrihydrite regardless of whether the arsenic is coprecipitated with or adsorbed onto the ferrihydrite. However, under these reaction conditions, release from materials with adsorbed arsenate greatly exceeds that from materials with coprecipitated arsenate. In fact, a considerable amount of arsenic was released from the 10 wt% ADS ferrihydrite before reductive dissolution was initiated. Therefore, the characterization of arsenate-bearing iron oxide materials to determine the method of arsenate incorporation into structures—perhaps by quantification of Fe-Fe coordination with EXAFS spectroscopy—may lead to improved predictions of the large-scale release of arsenic within aquifer systems under reducing conditions. 相似文献
14.
宁夏银川平原是继河套平原之后,在黄河流域发现的又一个高砷地下水分布区.为了总结其高砷地下水的水化学特征,并探索水化学因素对地下水砷释放和富集的影响机制,本文以银川平原北部（银北平原）作为典型研究区,采取野外水文地质调查、水样采集与测试、砷与水化学组分散点图相关分析及水文地球化学方法进行了综合研究.结果表明,银北平原地下水砷含量在0.2~177 μg/L之间;高砷地下水（大于50 μg/L） pH值多在7.5~8.5,水化学类型主要为HCO3-Na·Ca、Cl·HCO3-Na及Cl·HCO3-Na·Ca型,Eh多在-200~-100 mV.银北平原砷含量较高的地下水中COD、NH4+、HCO3-含量相应也较高,而NO3-和SO42-含量较低.高砷富有机质的冲-湖积含水层经过长期演化,形成偏碱性的中强还原性地下水环境和特殊的水化学特征,也具备极大的砷释放能力.较高的pH导致砷从铁锰氧化物或氢氧化物等水合物或黏土矿物表面解吸.其次部分铁锰氧化物在高pH、低Eh条件下可被还原为低价态可溶性铁锰,从而使与其结合的砷也得以释放进入地下水中.此外重碳酸根与砷酸根、亚砷酸根的竞争吸附行为促使含水层砷的解吸. 相似文献
15.
查明地下水中砷的时间变异性规律及机理是高砷地下水研究的难点和热点, 也是防控地下水砷污染的根本.选择在雨季前后对浅层潜水和孔隙承压水进行了动态监测.研究表明地下水砷含量和形态与地下水位波动存在明显的响应关系: 雨季开始后随着地下水位抬升, 地下水还原环境增强, As(Ⅴ)和Asp转化成As(Ⅲ), 颗粒态铁大幅降低, 导致水中溶解的砷和铁大幅增加, 地下水砷含量在雨季达到最高且As(Ⅲ)所占比例达到90%;雨季结束后随着水位逐渐降低, 地下水中As(Ⅲ)所占比例和溶解的砷含量下降.农业活动对浅层潜水砷形态季节性变化有明显的影响.孔隙承压水的砷形态分布变化较浅层潜水幅度大, 其变化与水位波动存在滞后效应.自然或人为活动引起的地下水位季节性变化改变了含水层的氧化还原环境, 补给水源与地下水之间的混合过程带来新的物质输入促进地下水系统中砷的迁移转化. 相似文献
16.
贵德盆地三河流域高砷地下水中溶解性有机物三维荧光特性及其指示意义 总被引：1，自引：0，他引：1
溶解性有机物(dissolved organic matter, DOM)可以通过多种方式控制含水层中砷的迁移转化。贵德盆地承压含水层地下水砷含量显著高于潜水含水层。为查明承压水中溶解性有机物对砷浓度的影响,对研究区地表水、潜水以及承压水进行吸光度和三维荧光光谱的分析,利用平行因子分析法确定了水样中有机物成分及荧光特征。结果表明,贵德盆地水体中DOM包含陆源类腐殖质(C1)、受人为影响的腐殖质(C2)、类醌化合物(C3)和微生物来源的腐殖质(C4)4种组分。陆源类腐殖质C1可在地下水中富集,占总有机质的40%~55%。相比于地下水,C2和C3则在地表水中占据较高的比例。高砷承压水中C2、C3所占比例高于低砷潜水。其中,C1可以通过络合作用促进溶解性砷浓度的提高,C3作为电子穿梭体可以促进含砷铁氧化物或氢氧化物的还原性溶解从而释放砷。微生物降解有机质生成的HCO-3可以与砷竞争吸附,促进砷的解吸附。此外,还原性溶解产生的Fe(II)与HCO-3形成FeCO3固定一部分的砷。该研究表明,地下水中的天然有机物通过络合作用和作为电子穿梭体促进铁氧化物还原导致地下水砷的富集,为分析黄河上游地区高砷地下水的成因提供理论依据。 相似文献
17.
江汉平原被确认为我国南方新的饮水型砷中毒病区,目前对于江汉平原高砷地下水的成因机理研究还有待完善.综合运用水文地球化学分析与PHREEQC地球化学模拟计算,分析了地下水和沉积物中REE分异特征及其沿地下水流向形态变化规律.江汉平原地下水REE含量为0.032~0.843 μg/L,富集LREE,具显著Eu正异常,且地下水中Eu异常与As含量呈正相关关系.地下水中REE形态主要以LnCO3+及Ln(CO3)2-为主,沿地下水流向LnCO3+降低、Ln(CO3)22-升高.地下水REE浓度分布受到HCO3-的络合作用及Fe氧化物矿物的还原性解吸附过程控制,径流途径中继承沉积物矿物的REE配分模式及Fe氧化物矿物对LREE的优先解吸附可能是地下水富集LREE的原因,并且沿流向上REE形态分布受到pH控制.研究区中Eu含量及Eu正异常对地下水As富集程度具有一定的指示意义. 相似文献
18.
Groundwater As concentrations >WHO limit (10 μg/L) are frequently found in the Po Plain (N. Italy). Although several hypotheses on As mobilization exist (i.e., reductive dissolution driven by peat degradation), the mechanisms of As release and subsequent attenuation acting in the multilayer aquifer in the Po Plain were poorly understood.The present work aims at implementing a reactive transport modeling of the aquifer system in Cremona, affected by As <183 μg/L, in order to quantify and test the feasibility of As release by the reductive dissolution of Fe-oxides driven by the degradation of peat contained in leaky aquitards and As attenuation downstream by the co-precipitation in iron sulfides.The model, based on a partial equilibrium approach, revealed that the observed As, Fe and Mn chemistry could be mostly explained by the simultaneous equilibrium between Fe-oxide and sulfate reduction and FeS precipitation and by the equilibrium of rhodochrosite precipitation/dissolution. Model results, together with litholog analysis, supported the assumption of peat as the likely source of organic matter driving As release. The model fitted to measured data showed that the peak in the organic carbon degradation rate at 20–40 m below surface (average of 0.67 mM/y), corresponding to the shallow peaty aquitard and the upper portion of the underlying semiconfined aquifer, is associated with the peak of net release of As (average of 0.32 μM/y) that is followed just downstream by a net precipitation in iron sulfides at 40–60 m below surface (average of 0.30 μM/y). These results support the assumptions of peaty aquifers as drivers of As release and iron sulfides as As traps. The model also outlined the following aspects that could have a broad applicability in other alluvial As affected aquifers worldwide: (a) shallow peaty aquitards may have a greater role in driving the As release since they likely have young and more reactive organic matter; (b) the occurrence of Fe-oxide reduction and FeS precipitation, that represent the As source and sink, together with sulfate reduction occurring simultaneously close to equilibrium may restrict the As mobility limiting the extent of contamination just downstream the source of organic matter that drives its release. 相似文献