Implementation of microbial processes in the performance assessment of spent nuclear fuel repositories

Present strategies for the long-term disposal of high-level nuclear wastes are based on the construction of repositories hundreds of meters below the earth surface. Although the surrounding host-rocks are relatively isolated from the light at the earth surface they are by no means lifeless. Microorganisms rule the deep part of the biosphere and it is well established that their activity can alter chemical and physical properties of these environments. Microbial processes can directly and indirectly affect radionuclide migration in multiple ways. Within 6th FP IP FUNMIG the interplay between microbial biofilms and radionuclides and the effect of microbially induced redox transformations of Fe on radionuclide mobility have been investigated. For the first time, formation of U(V) as a consequence of microbial U(VI) reduction in a multi-species biofilm was detected in vivo by combining laser fluorescence spectroscopy and confocal laser scanning microscopy. Furthermore, it was demonstrated that addition of U(VI) can lead to increased respiratory activity in a biofilm. Increased respiration in a biofilm can create microenvironments with lower redox potential, and hence induce reduction of radionuclides. Transient mobilization of U was observed in experiments with Fe oxides containing adsorbed U(VI) in which the activity of SO₄-reducing organisms was mimicked by sulfide addition. Faster reaction of sulfide with Fe oxides compared to U(VI) reduction, and decreasing U(VI) adsorption due to the transformation of Fe oxides into FeS can explain the observed intermittent U mobilization. The presented research on microbe-radionuclide interactions performed within FUNMIG addresses only a few aspects of the potential role of microorganisms in the performance assessment of nuclear waste repositories. For this reason, additionally, this article provides a cursory overview of microbial processes which were not studied within the FUNMIG project but are relevant in the context of performance assessment. The following aspects are presented: (a) the occurrence and metabolic activity of microorganisms of several proposed types of host-rocks, (b) the potential importance of microorganisms in the near-field of nuclear waste repositories, (c) indirect effects of microbial processes on radionuclide mobility in the repository far-field, (d) binding of radionuclides to microbial biomass, (e) microbial redox transformations of radionuclides, and (f) the implementation of microbial processes in reactive transport models for radionuclide migration.     

Effects of flow rate and chemical oxygen demand removal characteristics on power generation performance of microbial fuel cells

Two microbial fuel cells with different oxygen supplies in the cathodic chamber were constructed. Electrogenic capabilities of both cells were compared under the same operational conditions. Results showed that binary quadratic equations can express the relationships between chemical oxygen demand degradation rate and chemical oxygen demand loading and between chemical oxygen demand removal rate and chemical oxygen demand loading in both cells. Good linear relationships between power output (voltage or power density) and flow rate and between power output and chemical oxygen demand degradation rate were only found on the cell with mechanical aeration in the cathodic chamber, but not on the cell with algal photosynthesis in the cathodic chamber. The relationships between power output and chemical oxygen demand removal rate and between power output and effluent chemical oxygen demand concentration on both cells can be expressed as binary quadratic equations. The optimum flow rates to obtain higher power density and higher Coulombic efficiency in the cell with mechanical aeration in the cathodic chamber (=0.85?mW/m² and 0.063%) and in the cell with algal photosynthesis in the cathodic chamber (=0.65?mW/m² and 0.05%) are about 1000 and 1460???L/min, respectively. The optimum chemical oxygen demand removal rates to obtain higher power density and higher Coulombic efficiency in the cell with mechanical aeration in the cathodic chamber (=1.2?mW/m² and 0.064%) and in the cell with algal photosynthesis in the cathodic chamber (=0.81?mW/m² and 0.051%) are about 40.5 and 36.5%, respectively.     

石墨对污泥中厌氧微生物代谢产物及其性能的影响

矿物材料对废水厌氧处理及厌氧污泥改性具有十分重要的作用,而微生物代谢产物是生物处理系统的重要组分,在提高污染物去除率和甲烷产量等方面也起到非常重要的作用。本研究对矿物材料石墨和厌氧微生物共存体系内溶解性微生物产物(soluble microbial product,SMP)和胞外聚合物(extracellular polymeric substances,EPS)进行了分析表征。结果表明,石墨对EPS和SMP的组成和含量影响显著,主要是由于石墨的吸附作用及其对石墨颗粒的环境毒性所致。红外光谱分析表明,添加石墨体系内SMP与EPS的基团种类并未发生明显改变,但含量有所改变。三维荧光分析结果显示,SMP的主要荧光类物质为色氨酸类似物和腐殖质(辅酶NADH),而EPS的主要荧光类物质为色氨酸类似物和腐殖酸,石墨能明显降低色氨酸类似物及腐殖酸类物质的产生。石墨会减弱微生物的相对疏水性,提高表面自由能,有利于微生物团聚体的形成。     

The effect of opium poppy oil diesel fuel mixture on engine performance and emissions

Recently, decreasing of fossil fuel reserves and their negative effect on environment have increased the interest in alternative energy sources. One of the alternative energy sources is vegetable oils. In this study, blends of 50 % opium poppy oil — 50 % diesel fuel mixture are tested as alternative fuel on a single cylinder, 4-stroke, air cooled, pre-combustion chamber diesel engine at different speeds and its effects on engine performance and emissions are investigated. When compared to the diesel fuel as average, engine torque and power decrease at 4 % and 5.73 %, respectively. Specific fuel consumption increases by using of 50% opium poppy oil — 50 % diesel fuel mixture. When compared to the diesel fuel as average, carbon monoxide and nitrogen oxides emissions of 50 % opium poppy oil — 50 % diesel fuel mixture decrease to 15.5 % and 5.9 %, respectively. Diesel fuel-opium poppy oil mixture has been found notably successful and environment friendly as an alternative fuel for diesel engines.     

Electrogenic capabilities of gram negative and gram positive bacteria in microbial fuel cell combined with biological wastewater treatment

The voltage and the power production of two gram negative and two gram positive bacteria in four identical continuous flow microbial fuel cells combined with biological wastewater treatment units were evaluated and compared in the present study. Each microbial fuel cell and biological treatment unit was operated at four different flow rates and four different external load resistances. The results show that overall removal efficiency of chemical oxygen demand for all four systems can reach more than 85.5 %. Each pure culture has different power generation performance that can be affected by some factors, such as wastewater characteristics, influent flow rate and hydraulic retention time of reactor. Good linear relationships between the flow rate and the potential and between the flow rate and the power density on four pure cultures at different external load resistances were found. Comamonas testosteroni has better power generation performance than Arthrobacter polychromogenes, especially at higher flow rate. Although Pseudomonas putida also showed higher power generation than Corynebacterium glutamicum, the difference was not statistically significant. It seems that gram negative bacteria could display higher power generation than gram positive bacteria at higher flow rate. However, more evidence is required to provide stronger proof for the difference of power generation between gram negative and gram positive bacteria.     

Evaluating the effect of active ions on the early performance of soft clay solidified by modified biomass waste-rice husk ash

Acta Geotechnica - Soft clay generally cannot be directly used as subgrade material due to its poor engineering characteristics. The application of rice husk ash (RHA) for the solidification of...     

高岭土对煤生物产气的影响及微生物群落响应

高岭土是自然界较常见的无机矿物,对微生物的生长代谢有促进作用,煤中赋存大量高岭土,而有关其对煤生物产气影响的报道确较少。为探究高岭土对煤生物产气的影响,以陕西榆林煤为研究对象,以驯化的微生物作为产气菌群,通过在培养基中添加不同质量分数的高岭土进行煤生物模拟产气,利用气相色谱仪、酶标仪、傅里叶红外光谱仪、Illumina高通量测序平台,研究CH₄产量、总挥发性脂肪酸(Volatile Fatty Acids, VFAs)浓度、辅酶F₄₂₀含量、产气前后煤的有机官能团和微生物群落结构的变化。结果表明:高岭土的添加影响生物产气过程,0~8.0%高岭土添加量可明显分为2个区间,0~1.0%和2.0%~8.0%,产甲烷量、累积产甲烷量和F₄₂₀在2个区间内呈先升后降趋势,而乙酸和VFAs浓度变化趋势相反;模拟生物产气50 d后,添加高岭土实验组(0.5%)每克煤累积产甲烷量最高可达216 μmol,较空白组提高55.4%;同时,添加高岭土可以提高辅酶F₄₂₀的含量,最高可达48.93 ng/L,也有助于煤中的醇、酚—OH、—NH—和—NH₂被微生物利用。高岭土对煤生物产气体系中细菌种群结构的影响规律不明显,仅Firmicutes(厚壁菌门)在0~1.0%和2.0%~8.0%添加区间呈现先增后减的变化趋势;相比之下,高岭土的添加对古菌丰度变化影响较明显,体系中的古菌主要是Euryarchaeota(广古菌门),其中,Methanosarcina(甲烷八叠球菌属)和Methanobacterium(甲烷杆菌属)是古菌中丰度最高的种属,Euryarchaeota和Methanosarcina丰度在0~1.0%和2.0%~8.0%区间内与甲烷累积产量变化、F₄₂₀变化趋势一致,Methanobacterium却和VFAs变化趋势一致。由此得出,高岭土的添加会影响榆林煤的生物产气,其产甲烷量、VFAs、F₄₂₀酶活性、微生物群落结构和煤中有机官能团组成均会发生变化,这为后续研究煤中无机矿物对煤的生物产气的影响提供参考。      

Non-parallelism between the effect of microbial flocculants on sewerage disposal and the flocculation rate

1 IntroductionMicrobial flocculant (MBF) is one of the naturalmacromolecular organic compounds, which is producedby some microorganisms and has a high flocculationfunction ( Cheng Wen et al., 2003). It has beencalled“the third-generation flocculant”beca…     

烟草叶中异构和反异构烷烃的成因及其光合作用C同位素分馏效应

烟草叶是目前惟一可以通过生物合成得到大量异构和反异构烷烃的植物,然而许多文献对化合物中甲基碳位和奇偶碳数的变化成因未提及.对其成因进行了文献追踪,并对温室不同生长条件(温度、CO2和光照)下培育的烟草叶中的长链正构烷烃、异构和反异构烷烃的单体稳定C同位素组成进行了分析,以期对烟草叶中特殊脂类化合物的生物化学合成同位素分馏效应进行探索研究.与正构烷烃和异构烷烃相比,反异构烷烃的δ13C值平均相对偏重2‰,证明反异构烷烃确实具有不同的合成前身物(2-甲基丁酰辅酶A).比起甲基基团,脱羧反应很可能使得乙酰辅酶A的羧基基团δ13C值偏轻.本研究中异构烷烃和正构烷烃δ13C值的相似性,说明乙酰辅酶A和前身物2-甲基丙酰辅酶A(C4-CoA)之间的C同位素组成很可能是相似的.用水量越多,烟草叶中异构、反异构烷烃和正构烷烃稳定C同位素组成越偏轻.与强光条件比,弱光条件下培育的烟草叶中正构烷烃的稳定C同位素组成偏轻约2.2‰,异构和反异构烷烃稳定C同位素组成也分别偏轻1.8‰和1.9‰.温度对烟草叶正构烷烃、异构烷烃和反异构烷烃的稳定C同位素组成影响甚小,与Farquhar(1980)有关植物体C同位素组成的报道相吻合.     

Sorption properties of 1, 3, 5-trichlorobenznene on kerogen

Kerogen is an important organic matter fraction widely spread in soils and sediments. It plays a major role in the sorption and sequestration of hydrophobic organic contaminants （HOCs） such as trichlorobenzene （TCB）. It is known that kerogen is geochemically heterogeneous due to the differences in source materials and diagenesis history. We hypothesized that kerogen derived from different source materials and diagenetic history exhibits different sorption properties for TCB. We employed two different kerogen materials （coals） as the original materials and two series of kerogen for a given series with an identical source material but different alteration history were yielded through thermal treatment at temperature ranging from 200 to 500℃. The original and treated materials were characterized for their physicochemical properties. Sorption experiments were conducted with batch reactor systems using 1, 3, 5-TCB as the HOCs sorbates and the original and treated materials as the sorbents.     

Molecular and isotopic analyses of the hydroxy acids, dicarboxylic acids, and hydroxicarboxylic acids of the Murchison meteorite

The hydroxymonocarboxylic acids, dicarboxylic acids, and hydroxydicarboxylic acids of the Murchison meteorite were analyzed as their tert-butyldimethylsilyl derivatives using combined gas chromatography-mass spectrometry. The hydroxydicarboxylic acids have not been found previously in meteorites. Each class of compounds is numerous with carbon chains up to C8 or C9 and many, if not all, chain and substitution position isomers represented at each carbon number. The alpha-hydroxycarboxylic acids and alpha-hydroxydicarboxylic acids correspond structurally to many of the known meteoritic alpha-aminocarboxylic acids and alpha-aminodicarboxylic acids, a fact that supports the proposal that a Strecker synthesis was involved in the formation of both classes of compounds. Isotopic analyses show these acids to be D-rich relative to terrestrial organic compounds as expected; however, the hydroxy acids appear to be isotopically lighter than the amino acids with respect to both carbon and hydrogen. The latter finding would not be expected if both classes of compounds came exclusively from common precursors as would have been the case for a Strecker synthesis.     

页岩气开采的相关实验、模型和环境效应

页岩气是一种重要的非常规天然气资源,正在改变世界能源、经济和政治格局。渗透率是评价页岩气藏商业开采可行性的重要参数之一,由于页岩的致密性,页岩气的流动机理不同于常规气藏,因此,页岩储层渗透率测试和页岩气流动模型已成为当前国际研究的热点课题之一。在对页岩气开采技术简单介绍的基础上,综述了页岩储层渗透率测试的试验和理论研究现状,分析了气体吸附对页岩渗透率的影响。阐述了页岩气流动模型的最新进展,分析了双重孔隙模型描述气体迁移的准确性,提出了描述均匀储层中页岩气解吸-扩散-渗流多级运移模型。评述了页岩气开采的温室效应和对地下水的影响,并简单介绍了适合页岩气开采的新技术即无水压裂开采技术,即采用CO2对页岩气藏分段压裂,同时将CO2埋存于废弃井中。最后,对页岩储层渗透率测试和页岩气流动模型研究的新发展以及无水压裂技术进行了展望。     

The effect of storms on Finnish dairy farms: electrical outage statistics and the effect on milk production

Natural Hazards - Due to technological advancement, agricultural production is increasingly dependent on electricity. At the same time, power delivery infrastructures are challenged by extreme...     

The effect of long-term reclamation on enzyme activities and microbial community structure of saline soil at Shangyu, China

Reclamation of saline soil plays an important role in supporting high population growth in China. To evaluate the effects of reclamation and sustainability of salt-affected land production, soil chemical properties, enzyme activities, microbial community structure and function in sites reclaimed in 1976, 1984 and 1996 were characterized. The 2009 site was left to succession fallow and chosen as a control site. Results showed that electrical conductivity (EC) and pH decreased rapidly after the soil forming process started. An accumulation of soil organic C as a result of farming was observed. In all sites, inorganic N and available P were increased within 33 years after reclamation and commencement of agriculture. As a result of reclamation, soil enzyme activity (β-glucosidase, phosphatase, urease and arylsulfatase) was increased. There were no significant differences in soil enzyme activity between the sites reclaimed in 1976 and 1984, with the exception of phosphatase. Carbon source utilization patterns were less diverse in control soil than in treatment sites. The activities of reclamation resulted in synthesis of new phospholipid fatty acids (14:0, 17:1 c9, 16:0 2OH, 17:0 10Me, i17:0, 20:4 ω6c). Principal component analyses showed that the sites reclaimed in 1976 and 1984 clustered together and were distinct from 1996. Taken together, reclamation showed significantly increased soil quality and microbial activity. EC was the main limiting soil quality characteristic, which showed a comparative steady state after a reclamation time of 33 years. Differences in soil enzyme activity and microbial community function after long-term reclamation have potential to be reflected in soil functional integrity and ecosystem service.     

The effect of hydrothermal impregnation of Ni,Co, and Cu on HZSM-5 in the nitrogen oxide removal

The selective catalytic reduction (SCR) of nitrogen oxides on M/ZSM-5 (M = Cu, Ni, Co) catalysts was investigated. The catalysts were prepared using hydrothermal impregnation of the metal chlorides and nitrates on ZSM-5. The catalysts were characterized by nitrogen absorption/desorption, X-ray diffraction, Fourier transform infrared (FTIR) spectroscopy, ultraviolet–visible diffusion reflection spectroscopy (UV–Vis DRS), temperature-programmed reduction (TPR), N₂O chemisorption and ammonia temperature-programmed desorption. The performance tests for SCR of NO were carried out in a fixed-bed reactor from 250 to 400 °C. During the impregnation, part of the aluminum was eliminated from the zeolite framework due to the acidity of the metal salt solution and heating process as indicated by the reduction in the intensity of XRD peaks and variations in the positions of the FTIR vibrational bands. The Cu(Cl)/ZSM-5 catalyst exhibited NO conversions over 90% over the entire temperature range. The other catalysts showed comparable activities, but the catalysts prepared with chloride salt precursors demonstrated higher activity than those based on nitrate as the precursor. Moreover, the TPR reduction peaks of the metal ion in catalysts prepared with chloride precursor were lower, and their UV–Vis absorption bands revealed bathochromic transfers with higher intensities. Concurrent with these changes, the activity of the catalyst increased. The TPR profiles indicated that Cu and Ni both had an oxidation number of +2, whereas Co was present in the oxidation number of +2 and +3. The mass transfer limitation analysis showed that for particles in millimeter size range or larger significant intra-particle mass transfer limitation would be expected.     

The effect of pH and natural microbial phosphatase activity on the speciation of uranium in subsurface soils

The biomineralization of U(VI) phosphate as a result of microbial phosphatase activity is a promising new bioremediation approach to immobilize uranium in both aerobic and anaerobic conditions. In contrast to reduced uranium minerals such as uraninite, uranium phosphate precipitates are not susceptible to changes in oxidation conditions and may represent a long-term sink for uranium in contaminated environments. So far, the biomineralization of U(VI) phosphate has been demonstrated with pure cultures only. In this study, two uranium contaminated soils from the Department of Energy Oak Ridge Field Research Center (ORFRC) were amended with glycerol phosphate as model organophosphate source in small flow-through columns under aerobic conditions to determine whether natural phosphatase activity of indigenous soil bacteria was able to promote the precipitation of uranium(VI) at pH 5.5 and 7.0. High concentrations of phosphate (1-3 mM) were detected in the effluent of these columns at both pH compared to control columns amended with U(VI) only, suggesting that phosphatase-liberating microorganisms were readily stimulated by the organophosphate substrate. Net phosphate production rates were higher in the low pH soil (0.73 ± 0.17 mM d⁻¹) compared to the circumneutral pH soil (0.43 ± 0.31 mM d⁻¹), suggesting that non-specific acid phosphatase activity was expressed constitutively in these soils. A sequential solid-phase extraction scheme and X-ray absorption spectroscopy measurements were combined to demonstrate that U(VI) was primarily precipitated as uranyl phosphate minerals at low pH, whereas it was mainly adsorbed to iron oxides and partially precipitated as uranyl phosphate at circumneutral pH. These findings suggest that, in the presence of organophosphates, microbial phosphatase activity can contribute to uranium immobilization in both low and circumneutral pH soils through the formation of stable uranyl phosphate minerals.     

The effect of sedimentation on the primary production of benthic microflora

During February 1978, 20 cm of rain over a seven day period caused an enormous deposition of fine-grained sediments in the eastern arm of Mugu Lagoon, California. For February–July 1978, this deposition decreased the net primary production of the benthic community by an estimated 6.5 fold. The persistence of the fine-grained sediment over much of the lagoon will continue to render these areas lower in exportable organic carbon.     

A comparative study of the hydroxy acids from the Murchison, GRA 95229 and LAP 02342 meteorites

The hydroxy acid suites extracted from the Murchison (MN), GRA 95229 (GRA) and LAP 02342 (LAP) meteorites have been investigated for their molecular, chiral and isotopic composition. Substantial amounts of the compounds have been detected in all three meteorites, with a total abundance that is lower than that of the amino acids in the same stones. Overall, their molecular distributions mirror closely that of the corresponding amino acids and most evidently so for the LAP meteorite. A surprising l-lactic acid enantiomeric excess was found present in all three stones, which cannot be easily accounted by terrestrial contamination; all other compounds of the three hydroxy acid suites were found racemic. The branched-chain five carbon and the diastereomer six-carbon hydroxy acids were also studied vis-a-vis the corresponding amino acids and calculated ab initio thermodynamic data, with the comparison allowing the suggestion that meteoritic hydroxyacid at these chain lengths formed under thermodynamic control and, possibly, at a later stage than the corresponding amino acids. ¹³C and D isotopic enrichments were detected for many of the meteoritic hydroxy acids and found to vary between molecular species with trends that also appear to correlate to those of amino acids; the highest δD value (+3450‰) was displayed by GRA 2-OH-2-methylbutyric acid. The data suggest that, while the amino- and hydroxy acids likely relate to common presolar precursor, their final distribution in meteorites was determined to large extent by the overall composition of the environments that saw their formation, with ammonia being the determining factor in their final abundance ratios.     

Effect of fuel molecules on properties and activity of KOH/calcium aluminate nanocatalyst for biodiesel production

New technologies such as microwaves have gained a large deal of attention from scientists and industries who sought increased rate of production processes. In this study, microwave irradiation was utilized to produce a novel KOH/Ca₁₂Al₁₄O₃₃ nanocatalyst used for biodiesel production. As support, calcium aluminate was prepared by microwave combustion method using different fuels including urea, glycine, sorbitol, and citric acid. The samples were then impregnated by KOH to improve their catalytic activities for microwave-enhanced transesterification of canola oil for biodiesel production. Results of XRD, BET, FTIR, TG, EDX, and FE-SEM analyses showed differences in physicochemical properties of the samples when using different fuels with different flame characteristics and combustion temperatures. Only the urea-fueled sample showed the crystalline structure of monocalcium aluminate (CaAl₂O₄), with the other samples exhibiting amorphous structure of CaO–Al₂O₃. However, all samples, except for that prepared by citric acid, transformed to crystalline structure of Ca₁₂Al₁₄O₃₃ by calcination during KOH impregnation. Among the samples, the KOH/Ca₁₂Al₁₄O₃₃ nanocatalyst prepared by sorbitol showed the highest activity in microwave-enhanced biodiesel production because of its large surface area, pore size, and basicity, converting 93.4% of canola oil to biodiesel at a methanol-to-oil molar ratio of 18, catalyst concentration of 4 wt%, and microwave output power of 450 W in 60 min of reaction time. Moreover, the sample showed well-distributed particle sizes without any agglomeration, so that it could easily maintain its level of activity for several rounds of use.     

The effect of gross primary production, net primary production and net ecosystem exchange on the carbon fixation by chemical weathering of basalt in northeastern Iceland

The overall objective of this study is to define and interpret the annual dissolved inorganic carbon (DIC) flux in selected river catchments in North Eastern Iceland. The flux stems primarily from chemical weathering of basalt. The DIC flux out of the catchments is compared with the spatial distribution of the various vegetation communities and their gross primary production (GPP), net primary production (NPP) and net ecosystem exchange (NEE). There is no correlation between the DIC flux and the GPP, but one between DIC and NPP. The DIC flux is highly dependent on the NEE, which in turn is governed by the area extent of wetlands in these catchments. A variation by a factor 5 of the NEE results in a variation by a factor 2.8 in the river dissolved inorganic flux.