Arsenic release from microbial reduction of scorodite in the presence of electron shuttle in flooded soil

Scorodite (FeAsO₄·H₂O) is a common arsenic-bearing (As-bearing) iron mineral in nearsurface environments that could immobilize or store As in a bound state.In flooded soils,microbe induced Fe(Ⅲ) or As(Ⅴ) reduction can increase the mobility and bioavailability of As.Additionally,humic substances can act as electron shuttles to promote this process.The dynamics of As release and diversity of putative As(Ⅴ)-reducing bacteria during scorodite reduction have yet to be investigat...     

微生物铁氧化作用对砷迁移转化的影响

采用厌氧培养的方法,从砷污染的水稻上中富集依赖硝酸盐的铁氧化菌群,通过监测培养体系中Fe和A$的形态变化模拟水稻厌氧条件下微生物铁氧化过程对As迁移转化的影响.结果表明,约96%外源添加的Fe(Ⅱ)可在10d内氧化成Fe(Ⅲ),As(Ⅲ)对Fe(Ⅱ)的初期氧化速率具有一定的抑制作用;在微生物铁氧化过程中,As(Ⅲ)被氧...     

磷酸铁污泥的生物还原释磷及其影响因素研究

以污水处理厂化学除磷工艺产生的磷酸铁(FePO4)污泥为研究对象,在厌氧条件下,考察了铁还原细菌(IRB)还原FePO4释放磷的可行性,并探讨了不同碳源、C/Fe摩尔比、添加蒽醌-2,6-二磺酸盐(AQDS)对IRB利用FePO4还原释磷的影响.研究结果表明,通过驯化可从普通活性污泥富集IRB,且利用IRB可对难溶性沉淀FePO4进行生物还原.IRB能够利用葡萄糖、乙酸钠及丙酸钠作为唯一电子供体,使FePO4发生异化还原,产生Fe(Ⅱ)并释放磷酸盐,且泥水混合液中Fe(Ⅱ)累积量与上清液中磷累积量变化趋势一致.在等摩尔碳量前提下,葡萄糖为碳源时释磷率可达51.6%,比乙酸钠和丙酸钠分别高13.8%和20.3%;以葡萄糖为碳源,C/Fe摩尔比为5:1时释磷率最大;添加电子穿梭体AQDS可使FePO4污泥释磷率提高12.6%.     

Bacterial reduction and release of adsorbed arsenate on Fe(Ⅲ)-, Al- and coprecipitated Fe(Ⅲ)/Al-hydroxides

Mobilization of arsenic under anaerobic conditions is of great concern in arsenic contaminated soils and sediments. Bacterial reduction of As(V) and Fe(Ⅲ) influences the cycling and partitioning of arsenic between solid and aqueous phase. We investigated the impact of bacterially mediated reductions of Fe(Ⅲ)/Al hydroxides-bound arsenic(V) and iron(Ⅲ) oxides on arsenic release. Our results suggested that As(V) reduction occurred prior to Fe(Ⅲ) reduction, and Fe(Ⅲ) reduction did not enhance the release of arsenic. Instead, Fe(Ⅲ) hydroxides retained their dissolved concentrations during the experimental process, even though the new iron mineral-magnetite formed. In contrast, the release of reduced As(Ⅲ) was promoted greatly when aluminum hydroxides was incorporated. Thus, the substitution of aluminum hydroxides may be responsible for the release of arsenic in the contaminated soils and sediments, since aluminum substitution of Fe(Ⅲ) hydroxides universally occurs under natural conditions.     

沼渣与硫酸亚铁共处置含铬土壤的协同机制研究

利用沼渣和硫酸亚铁对含铬土壤进行共处置,在初步优化处置工艺参数后对共处置的协同效应进行验证,并通过XPS分析和微生物群落分析揭示了协同效用机理.结果表明,沼渣和硫酸亚铁共处置含铬土壤可实现土壤Cr (VI)含量低至未检出(检出限0.2mg/kg),优于硫酸亚铁处置法.共处置还原速率高于沼渣单独处置.微生物群落结构分析表明共处置组别细菌群落丰度与多样性高于沼渣单独处置,共处置土壤铬还原菌的相对丰度明显提高.此外,共处置组别内铁还原菌和硫酸盐还原菌的相对丰度也显著提升.通过XPS分析,共处置后的土壤中存在Fe (Ⅱ)、亚硫酸盐和硫化物,结合微生物群落分析结果,证实了铁和硫催化微生物还原六价铬过程.本研究为低碳型高浓度Cr (VI)污染土壤的治理提供新的思路.     

菌株Enterococcus sp.ZQ21异化还原Fe(Ⅲ)及产氢性质分析

一些发酵型异化铁还原细菌同时具有异化铁还原与产氢的能力,该类细菌在环境污染修复的同时能够解决能源问题,具有广阔应用前景。本文以海洋沉积物中异化铁还原细菌Enterococcus sp. ZQ21为研究对象,设置不同形态Fe(Ⅲ),分析菌株ZQ21异化铁还原与产氢性质。结果表明,当氢氧化铁和柠檬酸铁为电子受体时,菌株ZQ21以柠檬酸铁为电子受体时Fe(Ⅲ)还原效率较高,其酶活性分别为3.66 U和4.40 U。同时,菌株ZQ21在异化铁还原培养体系中具有产氢能力,以柠檬酸铁和氢氧化铁为电子受体进行厌氧发酵培养时,体系累积产氢量分别为(1395.30 ± 4.79）mL/L和（174.30 ± 3.23）mL/L,均显著高于对照组[(23.20 ± 2.09) mL/L]。通过液相发酵产物分析,在柠檬酸铁和氢氧化铁不同形态Fe(Ⅲ)培养条件下,菌株ZQ21分别表现出乙醇型发酵和丁酸型发酵产氢代谢类型。菌株Enterococcus sp. ZQ21具有异化铁还原和产氢能力,进一步拓宽发酵型异化铁还原细菌种质资源。     

巢湖沉积物磷铁硫形态记录及其环境变化指示

分析了巢湖表层和柱状沉积物中磷（P）、铁（Fe）和硫（S）元素的形态组成、分布、相互关系及其指示的湖泊环境变化.西半湖S3采样点位柱状沉积物总磷（TP）记录表明,巢湖西半湖区自20世纪60年代开始受人类活动影响逐步明显,其中钙磷（Ca-P）指示的流域径流输入增加早于铁铝磷（Fe/Al-P）指示的居民生活污水输入;西半湖区沉积物15~0cm有机质埋藏持续增加伴随着pH值的逐步升高,指示了水体富营养化导致藻类生产力（光合作用）提高并显著影响pH值;而东半湖S7采样点位柱状沉积物磷形态则记录了东半湖区不同的环境变化特征.巢湖沉积物活性铁组分以Fe （Ⅱ）为主,S3和S7沉积剖面Fe （Ⅲ）/Fe （Ⅱ）值整体均呈上升趋势且与Fe （Ⅲ）同步变化,表明其比值由Fe （Ⅲ）变化驱动;Fe （Ⅲ）/Fe （Ⅱ）指示沉积物上层为弱氧化性,其余层位为还原性环境.沉积物还原性无机硫（RIS）以酸可挥发性硫（AVS）为主,沉积物高有机质含量、低元素硫和还原条件降低了AVS向黄铁矿硫（CRS）的转化.巢湖沉积物中与P,S结合的Fe占比很小,高Fe/P和Fe/S比值会抑制沉积物磷的释放,导致柱状剖面P,Fe和S之间的相互作用关系整体上并不显著.     

Accelerated anaerobic dechlorination of DDT in slurry with Hydragric Acrisols using citric acid and anthraquinone-2,6-disulfonate (AQDS)

The application of electron donor and electron shuttle substances has a vital influence on electron transfer,thus may affect the reductive dechlorination of 1,1,1-trichoro-2,2-bis(p-chlorophenyl)ethane(DDT) in anaerobic reaction systems.To evaluate the roles of citric acid and anthraquinone-2,6-disulfonate(AQDS) in accelerating the reductive dechlorination of DDT in Hydragric Acrisols that contain abundant iron oxide,a batch anaerobic incubation experiment was conducted in a slurry system with four treatments of(1) control,(2) citric acid,(3) AQDS,and(4) citric acid + AQDS.Results showed that DDT residues decreased by 78.93%–92.11% of the initial quantities after 20 days of incubation,and 1,1-dichloro-2,2-bis(4-chlorophenyl)-ethane(DDD) was the dominant metabolite.The application of citric acid accelerated DDT dechlorination slightly in the first 8 days,while the methanogenesis rate increased quickly,and then the acceleration effect improved after the 8th day while the methanogenesis rate decreased.The amendment by AQDS decreased the Eh value of the reaction system and accelerated microbial reduction of Fe(III) oxides to generate Fe(II),which was an efficient electron donor,thus enhancing the reductive dechlorination rate of DDT.The addition of citric acid + AQDS was most efficient in stimulating DDT dechlorination,but no significant interaction between citric acid and AQDS on DDT dechlorination was observed.The results will be of great significance for developing an efficient in situ remediation strategy for DDT-contaminated sites.     

不同浓度锌处理下水稻幼苗对镉的累积效应

为探究锌(Zn)对水稻镉(Cd)累积的影响及其根表铁膜所发挥的作用,选取Cd高累积型水稻品种中9优547(简称"Z547")和Cd低累积型水稻品种金优402(简称"J402"),采用温室水培试验,研究0、2、5、10、15和20μmol/L等6个Zn浓度下水稻幼苗对Cd的累积效应,以及不同浓度Zn处理对根表铁膜生成量的影响.结果表明:①随着c(Zn)的增加,Z547和J402水稻幼苗生物量均呈先增后减的趋势,分别在c(Zn)为2和10μmol/L时达到最大值.②Z547和J402水稻幼苗中w(Cd)均呈先降后增的趋势,分别在c(Zn)为5和2μmol/L时达到最小值;当水稻幼苗中w(Cd)达到最小值时,Z547根和地上部中w(Cd)分别为31.65和11.47 mg/kg,J402根和地上部中w(Cd)分别为22.58和14.36 mg/kg.③不同浓度Zn处理下水稻幼苗各部位中w(Cd)均与根表铁膜中w(Mn)、w(Fe)、w(Fe+Mn)呈显著正相关,高铁膜处理水稻幼苗中w(Cd)显著高于低铁膜处理,表明根表铁膜生成量的增加会促进Cd在水稻幼苗中的累积.研究显示,当c(Zn)较低时...     

Characterization of bacterial community and iron corrosion in drinking water distribution systems with O3-biological activated carbon treatment

Bacterial community structure and iron corrosion were investigated for simulated drinking water distribution systems(DWDSs) composed of annular reactors incorporating three different treatments: ozone, biologically activated carbon and chlorination(O_3-BAC-Cl_2);ozone and chlorination(O3-Cl_2); or chlorination alone(Cl_2). The lowest corrosion rate and iron release, along with more Fe_3O_4 formation, occurred in DWDSs with O_3-BAC-Cl_2 compared to those without a BAC filter. It was verified that O_3-BAC influenced the bacterial community greatly to promote the relative advantage of nitrate-reducing bacteria(NRB)in DWDSs. Moreover, the advantaged NRB induced active Fe(III) reduction coupled to Fe(II) oxidation, enhancing Fe_3O_4 formation and inhibiting corrosion. In addition, O_3-BAC pretreatment could reduce high-molecular-weight fractions of dissolved organic carbon effectively to promote iron particle aggregation and inhibit further iron release. Our findings indicated that the O_3-BAC treatment, besides removing organic pollutants in water, was also a good approach for controlling cast iron corrosion and iron release in DWDSs.     

不同Fe(III)对活性污泥异化铁还原及除磷影响研究

以SBBR反应器活性污泥作为铁还原菌菌种来源,采用兼性厌氧/严格厌氧恒温培养试验,投加不同Fe(III)考察各条件下的异化铁还原能力,同时比较对磷的去除效果.结果表明:2种条件下Fe(III)还原能力具有较好的一致性,依次为:Fe(OH)3>氧化铁皮>青矿>红矿,其中严格厌氧条件下较好.同时,除磷效果与其呈正相关,富集培养至7d, Fe(OH)3及氧化铁皮体系出水磷浓度均达到2mg/L以下,之后继续降低,最终达到0.5mg/L以下.结合异化铁还原除磷机理,可以证明,不同Fe(III)表面吸附作用对TP的去除贡献较小,其主要作用为铁还原菌驱动下的化学沉淀去除.     

三价铁促进生物氧化锰稳定土壤砷的效果和机制

通过室内模拟实验,研究了三价铁对生物氧化锰（BMO）稳定化砷污染土壤的促进效果与作用机制.实验结果表明：三价铁的添加提高了BMO对土壤中砷的稳定化效率,当三价铁以质量分数百分比（以Fe计）为0.5%、1%、2%和4%添加时,砷的稳定化效率由单独BMO处理的63.02%增加至86.04%、93.86%、96.56%和97.98%;由连续提取实验结果可知,添加三价铁能够促进土壤中砷的结合形态由可交换态、专属吸附态向无定型铁锰结合态和结晶型铁锰结合态转变,增强土壤中砷的稳定化作用;风险分析进一步表明添加三价铁后砷的环境风险由中风险转变为低风险;矿物晶体结构分析表明,添加三价铁后土壤中出现水铁矿、纤铁矿等次生铁氧化物,这些铁氧化物对土壤中砷有良好的吸附固定能力.总体而言,三价铁的存在能够提高BMO对砷污染土壤的稳定化效率,但三价铁的添加量不宜过高,否则会引起土壤酸化问题.     

Enhanced U(VI) bioreduction by alginate-immobilized uranium-reducing bacteria in the presence of carbon nanotubes and anthraquinone-2,6-disulfonate

Uranium-reducing bacteria were immobilized with sodium alginate, anthraquinone-2, 6-disulfonate (AQDS), and carbon nanotubes (CNTs). The effects of different AQDS-CNTs contents, U(IV) concentrations, and metal ions on U(IV) reduction by immobilized beads were examined. Over 97.5% U(VI) (20 mg/L) was removed in 8 hr when the beads were added to 0.7% AQDS-CNTs, which was higher than that without AQDS-CNTs. This result may be attributed to the enhanced electron transfer by AQDS and CNTs. The reduction of U(VI) occurred at initial U(VI) concentrations of 10 to 100 mg/L and increased with increasing AQDS-CNT content from 0.1% to 1%. The presence of Fe(III), Cu(II) and Mn(II) slightly increased U(VI) reduction, whereas Cr(VI), Ni(II), Pb(II), and Zn(II) significantly inhibited U(VI) reduction. After eight successive incubation-washing cycles or 8 hr of retention time (HRT) for 48 hr of continuous operation, the removal efficiency of uranium was above 90% and 92%, respectively. The results indicate that the AQDS-CNT/AL/cell beads are suitable for the treatment of uranium-containing wastewaters.     

施硅对水稻铁膜砷固定和体内砷转运的影响

水稻铁膜对砷(As)的固定及其体内As的转运深刻影响着糙米中As的累积.施硅(Si)能够抑制水稻对As的累积,然而,施Si如何调控铁膜对As的固定和水稻各部位的As向糙米的转运,相关机制目前尚未十分清楚.以As超标土壤中的水稻铁膜为研究对象,通过开展不同Si处理水平的土壤盆栽试验,研究施Si对水稻根表铁膜固定As和各组织器官中As向糙米转运的影响及作用机制.结果表明,Si2(0.66 g·kg^-1)处理显著提高了水稻根系CAT(1.81倍)、SOD(7.98倍)和POD(1.25倍)酶活性,增加了铁膜中的DCB-Fe含量(44.35%),提高了铁膜的表面粗糙度(108.91%),导致铁膜的DCB-As含量明显升高(88.32%);而且,Si2处理显著增加了水稻根中As的累积率,降低了根和叶对As的转运能力,最终导致糙米中As含量的显著降低(53.12%).施Si增强水稻根表铁膜对As固定的原因可归结于Si促进铁膜的形成和增大铁膜的表面粗糙度,而施Si抑制根和叶中As向糙米的转运则可能与Si竞争水稻体内As的转运蛋白,促进As-巯基络合物形成以及增强As液泡区隔化等...     

AQS对Shewanella oneidensis MR-1还原含Cd聚合硫酸铁絮体的影响

考察了一种典型的溶解性腐殖质蒽醌-2-磺酸钠(disodium anthraquinone-2-sulfonate,AQS)存在时,典型异化铁还原菌Shewanella oneidensis MR-1在厌氧条件下还原含镉聚铁絮体的过程。结果表明:AQS的存在促进了含Cd絮体中Fe(Ⅲ)的还原,也促进了Cd~(2+)的释放。相比无AQS体系,存在AQS的体系中,Fe~(2+)和Cd~(2+)达到最高浓度的时间均有所缩短,最高浓度也更高;且低浓度AQS的促进效果明显高于高浓度AQS;AQS的存在没有改变二次矿物的种类,仍是针铁矿和磁铁矿,但降低了矿物的结晶度,且AQS浓度越高,改变越明显。存在AQS的体系中,菌体结合的Cd~(2+)更多,且镉的直接释放和间接释放风险均增大,低浓度AQS体系中镉的直接释放风险更大。     

草酸对微生物还原高岭土中铁的作用机制

通过微生物试验,比较了草酸浓度对微生物还原高岭土中Fe(Ⅲ)所起的作用;用环境扫描电镜(ESEM)和能量弥散X-射线谱图(EDS)分析了处理前后高岭土的结构变化。结果表明,在异化铁还原菌（dissimilatory iron reducing bacteria,DIRB）存在下,加入0.2 g/L的草酸,对Fe(Ⅲ)的还原效果最好;草酸浓度过高或过低对Fe(Ⅲ)的还原都有抑制,当草酸浓度为1.5 g/L时,微生物活性完全被抑制,此时Fe(Ⅲ)的还原量较低。化学对比试验表明,高岭土中Fe(Ⅲ)的还原随草酸浓度的增加逐渐增大,当草酸浓度达到13.0 g/L时,化学处理1 d后Fe(Ⅲ)的还原量与微生物处理4 d后Fe(Ⅲ)的还原量相当。ESEM和EDS的测试结果表明,高岭土中微生物还原Fe(Ⅲ)的过程,并不改变高岭土的主要结构,铁元素被微生物选择性的还原。     

Citrobacter sp.EBS8对施氏矿物和黄钾铁矾的还原溶解及相转化行为的影响

铁硫酸盐次生矿物广泛存在于酸性矿山废水（AMD）污染流域沉积物中,是多种有毒有害重金属的沉淀库.硫酸盐还原菌对矿物的还原作用可破坏矿物的稳定性从而引起共沉淀重金属的释放.在前期研究中发现柠檬酸杆菌Citrobacter sp.存在于AMD流域沉积物中,且在还原条件下具有较强的硫酸盐还原能力.因此,探究其对铁硫次生矿物的还原溶解及矿物晶相转化行为的影响尤为重要.本研究选取矿区沉积物中典型的铁硫次生矿物施氏矿物和黄钾铁矾为研究对象,在实验室条件下考察了从AMD污染沉积物中筛选到的菌株Citrobacter sp.EBS8对矿物的还原溶解及相转化的影响.结果表明,在缺氧、中性pH及电子供体足量时,在EBS8的作用下施氏矿物和黄钾铁矾均出现了明显的还原溶解现象.菌株EBS8可利用乳酸盐作为电子供体还原SO₄^2-和Fe（III）.SEM结果显示,施氏矿物在反应初期出现表面毛刺不平现象,黄钾铁矾发生由外向内的逐层溶解,矿物转化过程中都出现空壳形貌.XRD检测到施氏矿物组的主要转化产物为菱铁矿和蓝铁矿,黄钾铁矾体系中主要是蓝铁矿和马基诺矿.这些结果有助于了解AMD污染沉积物中铁硫酸盐矿物的转化行为及为AMD污染治理提供理论支撑.     

Shewanella oneidensis MR-1异化还原Fe(III)介导的As(III)氧化转化

在实验室模拟条件下,研究了Shewanella oneidensis MR-1作用下Fe(III)还原和As(III)氧化动力学及其影响因素.结果表明,Fe(III)被还原为Fe(II)的同时伴随着As(III)氧化为As(V);S. oneidensis MR-1 在含低浓度As(III)培养基上生长良好,在高浓度培养基上生长被抑制;As(III)通过制约菌体的生长与活性来抑制Fe(III)异化还原.同样,适量浓度的Fe(III)含量对As(III)氧化转化有很强的促进作用,但是过高浓度的Fe(III)浓度使得溶液中产生过多的Fe(II),从而对As(III)氧化转化有一定程度的抑制作用.此外,弱碱环境更有利于As(III)氧化转化.     

Ligand effects on arsenite removal by zero-valent iron/O2: Dissolution, corrosion, oxidation and coprecipitation

Ligands may increase the yields of reactive oxygen species (ROS) in zero-valent iron (ZVI)/O₂ systems. To clarify the relationship between the properties of ligands and their effects on the oxidative removal of contaminants, five common ligands (formate, acetate, oxalate, ethylenediaminetetraacetic acid (EDTA), and phosphate) as well as acetylacetone (AA) were investigated with arsenite (As(III)) as the target contaminant at three initial pH values (3.0, 5.0, and 7.0). The addition of these ligands to the ZVI/O₂ system resulted in quite different effects on As(III) removal. EDTA enhanced the oxidation of As(III) to arsenate (As(V)) but inhibited the removal of As(V). Oxalate was the only ligand in this work that accelerated both the removal of As(III) and As(V). By analyzing the ligand effects from the four aspects: dissolution of surface iron (hydr)oxides, corrosion of ZVI, reaction with ROS, and interference with precipitation, the following properties of ligands were believed to be important: ability to provide dissociable protons, complexation ability with iron, and reactivity with ROS. The complexation ability is a double-edged sword. It could enhance the generation of ROS by reducing the reduction potential of the Fe(III)/Fe(II) redox couple, but also could inhibit the removal of arsenic by coprecipitation. The elucidated relationship between the key property parameters of ligands and their effects on the ZVI/O₂ system is helpful for the rational design of effective ZVI/ligand/O₂ systems.     

Dissimilatory Fe(III) reduction characteristics of paddy soil extract cultures treated with glucose or fatty acids

Dissimilatory Fe(Ⅲ) reduction is a universal process with irreplaceable biological and environmental importance in anoxic environments. Our knowledge about Fe(Ⅲ) reduction predominantly comes from pure cultures of dissimilatory Fe(Ⅲ) reducing bacteria (DFRB). The objective of this study was to compare the effects of glucose and a selection of short organic acids (citrate, succinate, pyruvate, propionate, acetate, and formate) on Fe(Ⅲ) reduction via the anaerobic culture of three paddy soil solutions with Fe(OH)3 as the sole electron acceptor. The results showed significant differences in Fe(Ⅲ) reduction among the three paddy soil solutions and suhstrate types. Bacteria from the Sichuan paddy soil responded quickly to substrate supply and showed higher Fe(Ⅲ) reducing activity than the other two soil types. Bacteria in the Jiangxi paddy soil culture solution could not use propionate as a source of electrons for Fe(Ⅲ) reduction. Similarly, bacteria in the Jilin paddy soil culture could not use succinate effectively. Pyruvate was readily used by cultures from all three paddy soil solutions, thus indicating that there were some similarities in substrate utilization by bacteria for Fe(Ⅲ) reduction. The use of glucose and citrate as substrate for dissimilatory Fe(Ⅲ) reduction indicates important ecological implications for this type of anoxic respiration.