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1.
为查明土著微生物活动对高砷地下水形成的影响,利用河套平原高砷地下水中分离出的土著微生物(YH002)进行了微宇宙实验研究.实验结果表明: 高砷地下水中加入的葡萄糖提供了微生物生长所需要的碳源,微生物大量繁殖,分泌的有机酸使溶液的pH值降低.在缺氧条件下,溶液中的OD值最高达到了0.189,pH值最低为6.22;在有氧条件下,OD值最高达到了0.286,pH值最低为6.04.溶液中As(III)的初始质量浓度为74 μg/L,占总砷质量浓度的11.2%,在加入微生物和葡萄糖后,在缺氧和有氧条件下,As(III)的质量浓度分别为278 μg/L和310 μg/L,占总砷质量浓度的42%和47%.微宇宙实验说明地下水中的土著微生物能将As(V)还原成As(III).   相似文献   

2.
硫酸盐还原菌是厌氧环境中参与砷形态转化的重要微生物种群,其介导的生物地球化学循环过程对铁氧化物表面吸附态砷迁移转化的影响亟待深入研究.选取江汉平原典型高砷含水层原位沉积物分离纯化出一株严格厌氧硫酸盐还原菌Desulfovibrio JH-S1,对其进行砷和铁还原能力鉴定,并通过模拟培养实验探究硫酸盐还原菌参与下的铁矿物相转化对吸附态砷迁移的影响.Desulfovibrio JH-S1具有Fe(III)还原能力,无硫和有硫体系中Fe(III)均能被还原,但在硫酸盐充足条件下铁还原量显著增加;该菌株不具备As(V)还原能力,但添加硫酸盐的培养体系中As(V)去除率可达96%以上.Desulfovibrio JH-S1能够还原硫酸盐从而促进载砷的水铁矿还原转化为纤铁矿,并导致吸附的砷释放.江汉平原高砷含水层土著硫酸盐还原菌兼具硫酸盐/铁还原功能,参与了高砷含水层系统中砷-铁-硫耦合循环,对高砷地下水的形成具有重要作用.   相似文献   

3.
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   

4.
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   

5.
为探析长江口沉积物-水界面砷的迁移转化机制,本文分析了2019年夏季长江口4个站位上覆水和间隙水中总As浓度及形态的剖面变化特征,耦合氧化还原敏感元素(Fe、Mn和S)的剖面变化剖析了沉积物-水界面砷循环的Fe-Mn-S控制机制,同时结合砷相关功能基因探讨了沉积物-水界面砷迁移转化的微生物调控过程,估算了沉积物-水界面总As的扩散通量。结果表明,除A7-4站位外,长江口其他3个站位间隙水总As以As3+为主要存在形态,且总As浓度均在上覆水中为最低值(0.748~1.57 μg·L-1),而在间隙水中随着深度增加而逐渐增加并在6~9 cm深度达到峰值(7.14~26.9 μg·L-1)。间隙水总As及As3+浓度的剖面变化趋势与溶解态Fe2+、Mn2+相似,其均在中间层出现高值,说明沉积物Fe/Mn还原带砷的释放可能是随固相Fe(Ⅲ)或Mn(Ⅳ)的还原而转移到间隙水中的。氧化层和Fe/Mn还原带过渡区间隙水砷浓度与砷异化还原菌功能基因arrA和arsC丰度存在对应关系(除A1-3站外),说明砷异化还原菌将溶解As5+或固相As5+还原为溶解As3+可能是该过渡层砷迁移转化的另一重要过程。硫酸盐还原带的间隙水总As和As3+浓度降低,但由于间隙水的低S2-浓度不利于砷硫化物生成,因此深层间隙水砷可能与铁硫矿物结合而被移除。底层环境氧化还原条件是影响沉积物-水界面砷迁移转化的重要因素,随底层水DO浓度的降低,砷迁移转化更倾向于微生物还原控制。长江口沉积物-水界面总As的扩散通量为1.18×10-7~2.07×10-7 μmol·cm-2·s-1,均表现为沉积物间隙水中总As向上覆水释放,即沉积物是研究区域水体总As的来源之一。  相似文献   

6.
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52 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   

7.
张连凯  杨慧 《中国岩溶》2013,32(4):377-383
以广西南丹县里湖地下河作为研究区,对砷在地下河中的存在形态,迁移过程及其影响因素进行了分析。结果发现,里湖地下河中砷浓度较高且与人类活动密切相关;由于地下河中相对较低的氧化还原环境,使毒性更强的 As（Ⅲ）含量超过 As（V）,占总无机砷的53%,增加了该地区发生砷中毒的风险;总 As、As （III）和 As（V）在地下河中衰减了51%、36%、59%。相关性分析结果表明,沉积物中的 Fe、Ca、Mn、有机质及水体中的 Ca2＋与沉积物中的砷呈现显著正相关关系,有助于水体中砷的吸收;而水体中的 Cl-、SO 2-4、HCO -3与沉积物中的砷呈现负相关关系,不利于砷的吸附,其中 HCO -3的抑制作用最为明显。与非岩溶区水体相比,Ca 和 HCO -3成为影响砷迁移转化的主要因素,因此在岩溶地下河砷污染治理中应考虑岩溶区的水文地质特点,提高砷的污染治理效率。  相似文献   

8.
通过对典型区域剖面布设、环境地质钻探、现场取样、测试及数据分析，较详细地研究和分析了内蒙河套平原杭锦后旗沉积物中砷的地球化学特征及迁移释放机制。结果表明：杭锦后旗典型区沉积物中As的平均含量具有明显的分带性，且与沉积环境有密切相关，从盆地中心向盆地边缘逐渐增高，与Na、Cl元素的分布规律正好相反；沉积物中As含量与Sb、Fe、Mn、B、V含量正相关，与SiO2含量呈负相关，反映了沉积物中As的富集与地层中少砂石的含铁锰黏性沉积物有关；研究还表明，As被大量释放到地下水中并造成地下水As含量超标的主要机制与河套平原浅湖洼的还原环境有关。  相似文献   

9.
《地球科学》2011,36(3)
为查明土著微生物活动对高砷地下水形成的影响,利用河套平原高砷地下水中分离出的土著微生物(YH002)进行了微宇宙实验研究.实验结果表明:高砷地下水中加入的葡萄糖提供了微生物生长所需要的碳源,微生物大量繁殖,分泌的有机酸使溶液的pH值降低.在缺氧条件下,溶液中的OD值最高达到了0.189,pH值最低为6.22;在有氧条件...  相似文献   

10.
微生物活动对地下水水化学组分、氧化还原环境及砷的迁移转化有重要影响。研究高砷地下水系统的氧化还原分带性,有助于进一步理解微生物作用下地下水中砷的迁移转化规律,并为高砷地下水原位修复技术提供理论依据。在综述前人的研究成果的基础上,阐明了不同生物地球化学阶段砷的吸附、释放及固定过程,并刻画出高砷地下水系统的氧化还原分带性概念模型。在地下水环境中,微生物依次消耗(还原)溶解氧、NO-3、Fe(Ⅲ)、SO2-4和CO2等组分,氧化有机物获取能量。在溶解氧和NO-3还原阶段,地下水处于偏氧化环境,此时Fe(Ⅲ)还原受到抑制,其负载的砷不会释放到地下水中;当Fe(Ⅲ)还原时,地下水处于还原环境,会导致与之共存的砷释放,形成高砷地下水;而当SO2-4还原时,地下水处于强还原环境,产生的HS-与Fe2+形成的铁硫化物吸附或共沉淀砷,会降低地下水中的砷浓度。  相似文献   

11.
Incubation studies were carried out using 5 freshly collected sediments from shallow aquifers of the Hetao Basin, Inner Mongolia. The aquifer sediments covering a range of redox conditions, as indicated by their deep grey to yellow color were mixed with degassed artificial As solution or degassed deionized water at a ratio of solid to water of about 1:10 (wt./wt.). Suspensions which were either amended with glucose or autoclaved, were incubated in parallel with unamended suspensions. Five microcosm cultures of unamended sediments gradually release the equivalent of 0.03–0.30 μg/g As to the dissolved phase. The addition of glucose as a potential electron donor results in a marked stimulation in the mobilization of As (0.71–3.81 μg/g) in the amended incubations for all sediments. The quantity of As released accounts for 60–70% of As bound to Fe/Mn oxides in the original sediments. The microbially mediated mobilization of As with the organic nutrient as an electron donor is strongly associated with the As bound to Fe/Mn oxides, as well as the exchangeable As. During the incubations amended with glucose, 2–4% of the sediment Fe is released. The results suggest that the introduction of labile dissolved organic C into the yellowish sediment aquifers with As-free groundwater would reduce a significant proportion of the Fe(III) oxyhydroxides mediated by anaerobic bacteria respiration and increase groundwater As concentrations.  相似文献   

12.
Sediments from the Red River and from an adjacent floodplain aquifer were investigated with respect to the speciation of Fe and As in the solid phase, to trace the diagenetic changes in the river sediment upon burial into young aquifers, and the related mechanisms of arsenic release to the groundwater. Goethite with subordinate amounts of hematite were, using Mössbauer spectroscopy, identified as the iron oxide minerals present in both types of sediment. The release kinetics of Fe, As, Mn and PO4 from the sediment were investigated in leaching experiments with HCl and 10 mM ascorbic acid, both at pH 3. From the river sediments, most of the Fe and As was mobilized by reductive dissolution with ascorbic acid while HCl released very little Fe and As. This suggests As to be associated with an Fe-oxide phase. For oxidized aquifer sediment most Fe was mobilized by ascorbic acid but here not much As was released. However, the reduced aquifer sediments contained a large pool of Fe(II) and As that is readily leached by HCl, probably derived from an unidentified authigenic Fe(II)-containing mineral which incorporates As as well. Extraction with ascorbic acid indicates that the river sediments contain both As(V) and As(III), while the reduced aquifer sediment almost exclusively releases As(III). The difference in the amount of Fe(II) leached from river and oxidized aquifer sediments by ascorbic acid and HCl, was attributed to reductive dissolution of Fe(III). The reactivity of this pool of Fe(III) was quantified by a rate law and compared to that of synthetic iron oxides. In the river mud, Fe(III) had a reactivity close to that of ferrihydrite, while the river sand and oxidized aquifer sediment exhibited a reactivity ranging from lepidocrocite or poorly crystalline goethite to hematite. Mineralogy by itself appears to be a poor predictor of the iron oxide reactivity in natural samples using the reactivity of synthetic Fe-oxides as a reference. Sediments were incubated, both unamended and with acetate added, and monitored for up to 2 months. The river mud showed the fastest release of both Fe and As, while the effect of acetate addition was minor. This suggests that the presence of reactive organic carbon is not rate limiting. In the case of the river and aquifer sediments, the release of Fe and As was always stimulated by acetate addition and here reactive organic carbon was clearly the rate limiting factor. The reduced aquifer sediment apparently can sustain slower but prolonged microbially-driven release of As. The highly reactive pools of Fe(III) and As in the river mud could be due to reoxidation of As and Fe contained in the reducing groundwater from the floodplain aquifers that are discharging into the river. Deposition of the suspended mud on the floodplain during high river stages is proposed to be a major flux of As onto the floodplain and into the underlying aquifers.  相似文献   

13.
To understand the mechanism of arsenic mobilization from sediment to groundwater mediated by microorganism, vertical distribution of bacterial populations in aquifer sediments of the Hetao plain, Inner Mongolia was investigated by a two-step nested PCR-DGGE and 16S rRNA gene clone libraries, combined with sediment geochemistry. A borehole to 30 m depth was drilled and 11 sediment samples were collected. Lithological profile and different geochemical characteristics of sediments indicated a distinct transition of oxidizing–reducing environment along the depth of the sediment core. As(III) and Fe(II) concentrations elevated progressively from 10 m, simultaneously coupling with decrease of As(V) and Fe(III) concentrations, implying that reductive dissolution of arsenic-rich Fe(III) oxyhydroxides led to arsenic release. Results of DGGE displayed that sediment samples with higher concentrations of total arsenic and total organic carbon had lower population diversity, which suggested total arsenic concentrations were important to determine the population diversity of sediments. Bacterial communities of a sediment sample with the highest diversity and ratio of As(III) to total As were dominated by aerobic and facultative anaerobic bacteria and belonged to Alpha-, Beta-, and Gammaproteobacteria and Firmicutes group. Most of the retrieved sequences were closely related to high arsenic-resistance organisms, sulfide/thiosulfate oxidizers, denitrifiers, and aromatic hydrocarbon degraders. Thiobacillus distinctly predominated in clone library, which suggested that arsenic might be released by oxidized dissolution of sulfide minerals coupled to arsenate reduction or nitrate reduction in anaerobic condition. These data have important implications for understanding the microbially mediated arsenic mobilization in aquifers.  相似文献   

14.
Microcosm experiments were conducted to understand the mechanism of microbially mediated mobilization of Fe and As from high arsenic aquifer sediments. Arsenic-resistant strains isolated from aquifer sediments of a borehole specifically drilled for this study at Datong basin were used as inoculated strains, and glucose and sodium acetate as carbon sources for the experiments. In abiotic control experiments, the maximum concentrations of Fe and As were only 0.47 mg/L and 0.9 μg/L, respectively. By contrast, the maximum contents of Fe and As in anaerobic microcosm experiments were much higher (up to 1.82 mg/L and 12.91 μg/L, respectively), indicating the crucial roles of microbial activities in Fe and As mobilization. The observed difference in Fe and As release with different carbon sources may be related to the difference in growth pattern and composition of microbial communities that develop in response to the type of carbon sources.  相似文献   

15.
蒲阳河流域地下水水化学及同位素特征   总被引：3，自引：2，他引：1       下载免费PDF全文
保定西部山前地区位于太行山及华北平原交界带,为缓解极端气候灾害对生产生活的影响,维持地下水资源的可持续开发利用,开展相关的地下水水化学及同位素特征研究。研究区地下水化学类型以HCO3—Ca·Mg、HCO3·SO4—Ca·Mg及SO4·HCO3—Ca·Mg为主,区内地下水主要来源于大气降水,流域内地表水补给地下水;地下水中化学成分为Ca2＋、Mg2＋、HCO-3、SO2-4,主要来源于岩石风化作用,同时受到人类活动的影响,地下水中硝酸盐含量明显升高;由于受到褶皱构造的控制,流域的上游及平原区均出现年龄大于60年的地下水,多数岩溶水年龄较复杂,从现代水到大于60年的水均有分布。研究成果为流域内水资源的合理开发利用提供建议,区内岩溶地下水的开发将在一定程度上缓解极端天气的影响。  相似文献   

16.
Arsenic release experiments using natural indigenous microbial assemblages and natural sediment samples in Bangladesh have been performed. The As release appears to be facilitated by moderate organic input. Addition of some nutrients caused reducing conditions, which may generate the appropriate environment for Fe-reducing bacteria to become active. Detailed cellular phospholipid fatty acid (PLFA) analysis suggests the presence of SO4-reducing and Fe-reducing bacteria in the sediments. These Fe-reducing bacteria may serve as the agents catalyzing As release in the organic-rich sediments. 16S rDNA analysis of one cultured sample suggests the presence of clostridia, some of which are known to mediate Fe reduction. Based on new PLFA analyses, it is proposed that combined microbial processes of SO4 reduction to generate anaerobic conditions and Fe reduction to co-reduce As are important biogeochemical factors for As release in the Bangladesh sediments.  相似文献   

17.
Environmental geochemistry of high arsenic groundwater at Hetao plain was studied on the basis of geochemical survey of the groundwater and a core sediment. Arsenic concentration in groundwater samples varies from 76 to 1093 μg/L. The high arsenic groundwater mostly appears to be weakly alkaline. The concentrations of NO3− and SO42− are relatively low, while the concentrations of DOC, NH4+, dissolved Fe and sulfide are relatively great. Analysis of arsenic speciation in 21 samples shows that arsenic is present in the solution predominantly as As(III), while particulate arsenic constitutes about 10% of the total arsenic. Methane is detected in five samples with the greatest content being 5107 μg/L. The shallow aquifer in Hangjinhouqi of western Hetao plain is of strongly reducing condition. The arsenic content in 23 core sediment samples varies from 7.7 to 34.6 mg/kg, with great value in clay and mild clay layer. The obvious positive relationship in content between Fe2O3, Mn, Sb, B, V and As indicates that the distribution of arsenic in the sediments may be related to Fe and Mn oxides, and the mobilization of Sb, B and V may be affected by similar geochemical processes as that of As.  相似文献   

18.
The behavior of As in the subsurface environment was examined along a transect of groundwater monitoring wells at a Superfund site, where enhanced reductive dechlorination (ERD) is being used for the remediation of groundwater contaminated with chlorinated solvents. The transect was installed parallel to the groundwater flow direction through the treatment area. The ERD technology involves the injection of organic C (OC) to stimulate in situ microbial dechlorination processes. A secondary effect of the ERD treatment at this site, however, is the mobilization of As, as well as Fe and Mn. The concentrations of these elements are low in groundwater collected upgradient of the ERD treatment area, indicating that, in the absence of the injected OC, the As that occurs naturally in the sediment is relatively immobile. Batch experiments conducted using sediments from the site inoculated with an Fe(III)- and As(V)-reducing bacterium and amended with lactate resulted in mobilization of As, Fe and Mn, suggesting that As mobilization in the field is due to microbial processes.  相似文献   

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