Assessment of changes in microbial community structure during operation of an ammonia biofilter with molecular tools

Biofiltration has been used for two decades to remove odors and various volatile organic and inorganic compounds in contaminated off-gas streams. Although biofiltration is widely practiced, there have been few studies of the bacteria responsible for the removal of air contaminants in biofilters. In this study, molecular techniques were used to identify bacteria in a laboratory-scale ammonia biofilter. Both 16S rRNA and ammonia monooxygenase (amoA) genes were used to characterize the heterotrophic and ammonia-oxidizing bacteria collected from the biofilter during a 102-day experiment. The overall diversity of the heterotrophic microbial population appeared to decrease by 38% at the end of the experiment. The community structure of the heterotrophic population also shifted from predominantly members of two subdivisions of the Proteobacteria (the beta and gamma subdivisions) to members of one subdivision (the gamma subdivision). An overall decrease in the diversity of ammonia monooxygenase genes was not observed. However, a shift from groups dominated by organisms containing Nitrosomonas-like and Nitrosospira-like amoA genes to groups dominated by organisms containing only Nitrosospira-like amoA genes was observed. In addition, a new amoA gene was discovered. This new gene is the first freshwater amoA gene that is closely affiliated with Nitrosococcus oceanus and the particulate methane monooxygenase gene from the methane oxidizers belonging to the gamma subdivision of the Proteobacteria.     

bdGas carburizing of steel with furnace atmospheres formedin situ from methane and air and from butane and air

Carburizing experiments were conducted at 927°C (1700°F) and 843°C (1550°F) using furnace atmospheres formed from methane and air and from butane and air introduced directly into the carburizing furnace. Gas flow rates were low to promote equilibration of the reaction products within the furnace. The air flow rate was held constant while the methane or butane flow was automatically regulated to maintain a constant oxygen potential, as measured by a zirconia oxygen sensor, within the furnace. In comparing the results of these experiments with earlier results obtained using propane and air, several differences were noted: (a) The methane content of the furnace atmosphere, measured by infrared analysis, was about twice as great when methane was the feed gas rather than propane or butane. This was true despite the fact that the mean residence time of the gas within the furnace was greater in the methane experiments. Methane appears to be less effective than propane or butane in reducing the CO₂ and H₂O contents to the levels required for carburizing. (b) There was a greater tendency for the CO content of the furnace atmosphere to decrease at high carbon potentials when methane is used instead of propane or butane. The decrease in CO content is due to hydrogen dilution caused by sooting in the furnace vestibule. These differences in behavior make propane or butane better suited than methane forin situ generation of carburizing atmospheres. However, there is no difference in the amount of carburizing occurring at a specified carbon potential when methane, propane, or butane are used as the feed gas in this process. J.A.Pieprzak, formerly a member of the Engineering and Research Staff     

Aerobic Methane Oxidation Coupled to Denitrification: Kinetics and Effect of Oxygen Supply

Aerobic methane oxidation coupled to denitrification (AME-D) is a process in which aerobic methanotrophs oxidize methane and release organic compounds that are used by coexisting denitrifiers as electron donors for denitrification. This process is potentially promising for denitrification of wastewater or landfill leachate poor in organic carbon using methane produced onsite as external electron donor. We studied the kinetics of an aerobic methane-oxidizing denitrifying culture and investigated the effect of dissolved oxygen (DO) concentration and air supply rate on AME-D using a batch reactor and a semicontinuous reactor setup. At methane concentrations of 18–33% in air and air flow rates of 15–35?mL?air?L?1?liquid?min?1, the DO concentration was less than 0.01?mg?L?1 and the nitrate removal reached a maximum value of 56.7?mg?NO3–N?g?1?VSS?d?1 with 79% being attributed to denitrification. When the air supply rate was increased to 70?mL?air?L?1?liquid?min?1 resulting in a drop in methane content to 10%, the DO concentration in the bioreactor rose to about 0.8–1.0?mg?L?1 and the total nitrate removal dropped to about 10?mg?NO3–N?g?1?VSS?d?1 with none of it being attributed to denitrification.     

Simulation of the Effect of an Increase in Methane on Air Temperature

The infrared radiative effect of methane was analyzed using the 2D. interactive chemical dynamical radiative SOCRATES model of the National Center for Atmospheric Research. Then, a sensitivity experiment, with the methane volume mixing ratio increased by 10%. was carried out to study the influence of an increase of methane on air temperature. The results showed that methane has a heating effect through the infrared radiative process in the troposphere and a cooling effect in the stratosphere. However, the cooling effect of the methane is much smaller than that of water vapor in the stratosphere and is negligible in the mesosphere. The simulation results also showed that when methane concentration is increased by 10%. the air temperature lowers in the stratosphere and mesosphere and increases in the troposphere. The cooling can reach 0.2 K at the stratopause and can vary from 0.2-0.4 K in the mesosphere, and the temperature rise varies by around 0.001-0.002 K in the troposphere. The cooling results from the increase of the infrared radiative cooling rate caused by increased water vapor and O3 concentration, which are stimulated by the increase in methane in most of the stratosphere. The infrared radiation cooling of methane itself is minor.The depletion of O3 stimulated by the methane increase results indirectly in a decrease in the rate of solar radiation heating, producing cooling in the stratopause and mesosphere. The tropospheric warming is mainly caused by the increase of methane, which produces infrared radiative heating. The increase in H2O and O3 caused by the methane increase also contributes to a rise in temperature in the troposphere.     

Enrichment of Methane Concentration via Separation of Gases using Vortex Tubes

The objective of this work was to determine if a vortex tube can be used as a gas separation device. A vortex tube is a simple mechanical device that has no moving parts. It separates a compressed inlet fluid into two streams, one hot and the other cold. There are a variety of theories to explain this separation. It has been hypothesized that a mixture of compressed gases flown into the vortex tube may separate into individual gas streams by virtue of differential centrifugal forces acting on them. During previous studies by others, conflicting results have been obtained using this hypothesis. Further study of the gas separation process in a vortex tube was carried out. An attempt has been made to separate methane and nitrogen gases using vortex tubes. This particular separation or the resulting enrichment of Methane concentration has applications in the mining industry. Methane is emitted in an underground coal mine. It leaks from the coal seams and is extremely hazardous for workers because of its high explosivity in air. A conventional but costly means of circumventing this problem is methane drainage before mining. Yet another effective method is to blow large amount of air through the mine to locally dilute methane concentration. The mixture of methane and air is directly passed into the atmosphere. There are advantages to separating methane from air at the ventilation exhaust of the mine. First, methane being a greenhouse gas has strict EPA emission standards, and second, methane can be directly used for generating power. In this experimental work, a laboratory size setup was used to investigate the feasibility of using a fixed geometry vortex tube for separating methane and nitrogen from a mixture. It was found that there was partial gas separation leading to a higher concentration of methane at one exit in comparison to the inlet and a lower concentration at the other exit.     

Catalytic performance of cerium iron complex oxides for partial oxidation of methane to synthesis gas

The cerium iron complex oxides oxygen carrier was prepared by the co-precipitation method. The reactions between methane and lattice oxygen from the complex oxides were investigated in a fixed micro-reactor system. The reduced oxygen carder could be re-oxidized by air and its initial state could be restored. The characterizations of the oxygen carders were studied using XRD, O2-TPD, and H2-TPR. The results showed that the bulk lattice oxygen of CeO2-Fe2O3 was found to be suitable for the partial oxidation of methane to synthesis gas. There were two kinds of oxygen species on the oxygen carrier： the stronger oxygen species that was responsible for the complete oxidation of methane, and the weaker oxygen species （bulk lattice oxygen） that was responsible for the selective oxidation of methane to CO and H2 at a higher temperature. Then, the lost bulk lattice oxygen could be selectively supplemented by air re-oxidation at an appropriate reaction condition. CeFeO3 appeared on the oxygen carrier after 10 successive redox cycles, however, it was not bad for the selectivity of CO and H2.     

煤矿乏风瓦斯变压吸附分离特性

以实验室活性炭吸附床为研究对象,建立了多维吸附床内煤矿乏风流动、吸附传质的数学模型.首先对活性炭富集煤矿乏风瓦斯过程进行了模拟,得到了各个循环步骤下床内详细的浓度分布和吸附量分布,模拟结果与实验结果符合较好.进而采用此模型,改变吸附压强、解吸压强和解吸温度等参数,对不同工况下瓦斯分离富集过程进行了对比模拟研究,揭示了煤矿乏风瓦斯变压吸附分离特性.     

Synthesis gas production using oxygen storage materials as oxygen carrier over circulating fluidized bed

A novel process for synthesis gas production over Circulating Fluidized Bed （CFB） using oxygen storage materials as oxygen carder was reported. First, oxygen in the air was chemically fixed and converted to lattice oxygen of oxygen storage materials over regenerator, and then methane was selectively oxidized to synthesis gas with lattice oxygen of oxygen storage materials over riser reactor. The results from simulation reaction of CFB by sequential redox reaction on a fixed bed reactor using lanthanum-based perovskite LaFeO3 and La0.8Sr0.2Fe0.9CO0.1O3 oxides prepared by sol-gel, suggested that the depleted oxygen species could be regenerated, and methane could be oxidized to synthesis gas by lattice oxygen with high selectivity. The partial oxidation of methane to synthesis gas over CFB using lattice oxygen of the oxygen storage materials instead of gaseous oxygen should be possibly applicable.     

Extreme Compaction Effects on Gas Transport Parameters and Estimated Climate Gas Exchange for a Landfill Final Cover Soil

Landfill sites have been implicated in greenhouse warming scenarios as a significant source of atmospheric methane. In this study, the effects of extreme compaction on the two main soil-gas transport parameters, the gas diffusion coefficient (Dp) and the intrinsic air permeability (ka), and the cumulative methane oxidation rate in a landfill cover soil were investigated. Extremely compacted landfill cover soil exhibited negligible inactive soil-air contents for both Dp and ka. In addition, greater Dp and ka were observed as compared with normal compacted soils at the same soil-air content (ε), likely because of reduced water-blockage effects under extreme compaction. These phenomena are not included in existing predictive models for Dp(ε) and ka(ε). On the basis of the measured data, new predictive models for Dp(ε) and ka(ε) were developed with model parameters (representing air-filled pore connectivity and water-blockage effects) expressed as functions of dry density (ρb). The developed Dp(ε) and ka(ε) models together with soil-water retention data for soils at normal and extreme compaction (ρb = 1.44 and 1.85??g?cm-3) implied that extremely compacted soils will exhibit lower Dp and ka at natural field-water content (-100??cm H2O of soil-water matric potential) because of much lower soil-air content. Numerical simulations of methane gas transport, including a first-order methane oxidation rate, were performed for differently compacted soils by using the new predictive Dp(ε) model. Model results showed that compaction-induced difference in soil-air content at a given soil-water matric potential condition is likely the most important parameter governing methane oxidation rates in extremely compacted landfill cover soil.     

Response diversity of pontine and deep cerebellar nuclear neurons to air puff stimulation of the eye in the alert cat

The discharge of antidromically identified brainstem and cerebellar nuclear neurons involved in the corneal reflex was recorded in the alert cat during corneal air puffs. Eye movements were measured with the search coil technique. Recorded sensory, motor, reticular formation and cerebellar nuclear neurons showed a wide diversity in latencies and patterns of response to air puff stimulation. This diversity suggests that each part of the circuit may contribute different properties to information processing for the corneal reflex, for sustained eyelid closure and, possibly, for the classical conditioning of the nictitating membrane response.     

甲烷燃烧催化材料发展概况

甲烷催化燃烧具有低温操作、环保、节能、长时间稳定燃烧、安全系数高等诸多优点，引起人们广泛关注。介绍了有关甲烷燃烧催化材料的一些最近发展动向，并提出了几种很有发展前景的甲烷燃烧催化材料。同时指出要实现催化材料的真正产业化，几个问题尚需解决：对于高活性的贵金属材料主要是提高贵金属的热分解温度，提高材料的高温稳定性；对于高温催化材料(如钙钛矿和六铝酸盐材料等)应努力提高材料的催化活性，并开发耐高温、抗热冲击、比表面大的载体(或活性涂层)材料。     

Double perovskite anti-supported rare earth oxide catalyst CeO_2/La_2CoFeO_6 for efficient ventilation air methane combustion

Ventilation air methane is one of available resources with a massive reserve.However,most of ventilation air methane is discharged into the air and pollutes the environment.Catalysts with high temperature resistance(>800℃)for ventilation air methane are very essential for utilization of the ventilation air methane.We mainly prepared catalysts CeO₂/La₂CoFeO₆and La₂CoFeO₆/CeO₂and comparative samples CeO₂and La₂CoFeO₆by the simple sol-gel method and calcined them under 9000C,and tested the catalytic performance of ventilation air methane combustion under the condition of 5 vol%H₂O.The experimental results show that the light-off temperature(T_1O)and complete combustion temperature(T₉₀)of the ventilation air methane combustion reaction of CeO₂/La₂CoFeO₆catalyst are 417.4 and 587.7℃,respectively.T_1Oand Tgo of La₂CoFeO₆/CeO₂only reach 425.5 and 615.8℃.The T₁₀and T_9Oof CeO₂/La₂CoFeO₆are 417.4 and 587.7℃,which are lower than those of La₂CoFeO₆[T₁₀=452.4℃and T₉₀=673.0℃)and La₂CoFeO₆/CeO₂(T₁₀=425.5℃and T₉₀=615.8℃).Therefore,the catalytic performance of the anti-supported rare earth oxide catalyst CeO₂/La₂CoFeO₆is better than that of La₂CoFeO₆and supported catalyst La₂CoFeO₆/CeO₂.     

工作面反风时采空区场量分布变动的数值模拟

结合华兴煤矿1318炮放面实例,运用数值模拟手段,描绘了工作面反风时采空区流场内漏风流,氧、CO和瓦斯各组分气体,以及温度等的分布变动过程,给出了反风时沿工作面边界各组分气体涌出量的变化规律.模拟在反风后,场内各组分气体含量分布重心发生倒置,原上游高温区被冷却,下游低温区逐渐转变为新的高温区,使采空区的温度上升过程重新回到一个相对较低的温度起点,使自燃升温得到一定的延缓.反风后,场内CO气体涌出量经历突降—回跳上升—缓慢衰减—再逐渐增加的跳动过程,瓦斯涌出量在经历大幅度突降和回跳后,其增幅度不大.用埋管抽放的办法能够防止因反风导致工作面内有害气体超限,同时给出了反风的实施条件,即必须确保采空区无明火.     

近距离高瓦斯煤层群倾斜高抽技术的应用研究

分析了沙曲矿14201工作面的瓦斯涌出特点,对倾斜高抽巷治理瓦斯的工艺技术参数进行了优化,观测了高抽巷治理瓦斯的效果．研究表明,在沙曲矿三软条件下近距离高瓦斯煤层群实施倾斜高抽技术治理瓦斯效果明显,能够抽放出大量的高浓度瓦斯,为工作面的安全生产提供了技术保障．     

Gas and particle emissions from housing in animal production

Animal agriculture is increasingly regarded as a source of pollutants such as gases, odours and particulates which may be both aggravating and ecologically harmful. An overview of the origin, number and quantity of pollutants emitted from animal housing and from manure stores is presented and possible means of preventing or reducing them are discussed. Of the 136 trace gases in the air of animal houses ammonia (NH3), methane (CH4) and nitrous oxide (N2O) present the greatest risk to the environment. The gases and particulates are emitted principally from freshly deposited and stored excreta, from animal feed, from litter and from the animals themselves. Total NH3 emissions from animal production in Germany are estimated as approximately 750,000 t/a. It is calculated that the average of which is higher than the average "critical loads" for most natural habitats. However, there is still a shortage of satisfactory information on the extent of emissions, in particular on those from naturally ventilated animal houses. NH3 has a direct effect on the trees in the vicinity of animal houses and is also transported long distances through the air contributing to eutrophication and acidification of water and soil. This frequently results in changes in plant ecology, hence reducing plant diversity. CH4 and N2O contribute to the "greenhouse effect". Emissions of CH4 from animal husbandry in Germany are estimated at about 1.5 Mt/a. This corresponds to 0.2% of the assumed global emission from all sources. There is still little knowledge about the quantities of N2O released from agricultural animals. The concentration of airborne microorganisms in livestock housing is between some 100 and several 1000 per liter of air.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cold jet: a method to obtain pure Schwann cell cultures without the need for cytotoxic, apoptosis-inducing drug treatment

Trace gases in exhaled air have been used as a simple means of assessing metabolic reactions. The investigations of trace gases derived from bacteria in human exhalation are usually hydrogen (H2) or methane (CH4). On the other hand, nitrous oxide (N2O) is also derived from microorganisms, especially denitrifying bacteria. Although many kinds of denitrifying bacteria have been isolated on and in the human body, there has been few concerning N2O. We studied 222 healthy people from the age of 5 to 85 years. The analysis of N2O in exhaled air was carried out by a infrared-photoacoustic (IR-PAS) analyzer. It was found that N2O ranged from 0 to 1670 ppbv in exhaled air and that 59% (131) of the subjects were producers of N2O. A highly significant relationship was observed between age and concentrations of N2O (r = 0.40, P < 0.01). The rate of production in young children and in the aged was significantly higher than that in adults aged 20-39 years (P < 0.01), and less than 30% were producers during puberty. The change of normal microflora on and in human body with aging may have caused the significant relationship between age and emissions of N2O.     

The effect of delta rays on the ionometric dosimetry of proton beams

The interface effects arising in the measurement of absorbed dose by ionization chambers, owing to the inhomogeneity between the walls and the gas, have been evaluated by an analytical model. The geometrical situation considered here is appropriate for representing the behaviour of a plane-parallel ionization chamber exposed to a radiotherapeutic beam of protons. Two gases, dry air and tissue equivalent gas (methane based), as well as six materials commonly used in ionization chamber walls, i.e. graphite, A-150 tissue equivalent plastic, C-522 air equivalent plastic, nylon type 6, polymethyl methacrylate and polystyrene, have been examined. The analysis of the results shows that, within the limits of the detector dimensions and proton energies commonly used in the dosimetry of radiotherapeutic beams, these effects, if not taken into account in the measurement interpretation, can entail deviations of up to about 2% with respect to the correct absorbed dose in gas.     

C2H6、C2H4、CO与H2对甲烷爆炸压力及动力学特性影响

为量化可燃气体爆燃引起的潜在危险性提供相关的基础数据,设计出在气体燃料加工、储存和运输过程中能够承受爆炸危险的容器。运用20 L球形气体爆炸系统,在不同初始温度（298～373 K）与不同的预混气体（CO、H₂、C₂H₄、C₂H₆）体积分数（0.4%～2.0%）条件下,获取了甲烷体积分数为7%与11%的甲烷?空气混合物的爆炸压力特性参数。此外,采用 CHEMKIN软件,模拟分析了不同体积分数的预混气体在爆炸过程中H·、O· 和·OH自由基摩尔分数的变化趋势,并进行了敏感性分析。结果表明,同一体积分数的预混气体,随初始温度的增加,最大爆炸压力呈线性降低,最大爆炸压力上升速率几乎恒定或下降。同一初始温度,对于甲烷体积分数为7%的甲烷?空气混合物,随着预混气体的体积分数增大到2%,其最大爆炸压力、最大爆炸压力上升速率均呈增大的趋势,而甲烷体积分数为11%的甲烷?空气混合物对应的最大爆炸压力与最大爆炸压力上升速率均呈减小趋势。随着预混气体体积分数的增加,甲烷体积分数为7%的甲烷?空气混合物在爆炸过程中H·、O·和·OH自由基摩尔分数峰值上升。O·和·OH自由基摩尔分数峰值在甲烷体积分数为11%的甲烷?空气混合物中呈下降趋势,H·自由基摩尔分数峰值有所上升。对于甲烷体积分数为7%与11%的甲烷?空气混合物,其影响甲烷的关键基元反应式不变,敏感性系数随预混气体体积分数的增加而减弱。      

模拟转炉底吹氧气和石灰粉的冷态及热态试验

为了研究转炉底吹氧气和石灰粉的冶炼工艺,进行了冷态和热态模拟试验.冷态模拟试验通过改变气源压力的方法,基本实现了对石灰粉流量的控制.喷粉罐的中路气流和下路气流发挥了主要作用.在内径6mm的输粉管和喷粉枪内径5mm的条件下实现了5min之内喷吹石灰粉6～9kg的目标.平均粉气比为11.2～23.3 kg/m3,输粉气平均...     

Lichens and moss as bioindicators and bioaccumulators in air pollution monitoring

In this study, we review research conducted in the La Spezia district during 1989, 1992, and 1994, using lichens and moss as indicators of air pollution. SO2 pollution was examined by means of an Index of Atmospheric Purity (IAP) based on the frequency of epiphytic lichen within a sampling grid. Metal deposits were estimated using the lichen Parmelia caperata and the moss Hypnum cupressiforme as bioaccumulators. IAP maps show progressive air quality improvement from 1989 to 1994. This trend correlates to a decrease in SO2 emissions during recent years that is attributed to the use of methane for residential heating and the closing of a coal-fired power plant. Metal contamination maps show that the most polluted area is now in the southeastern part of the gulf. The pattern of pollution coincides with the location of the chief pollution sources in the area. From 1989 to 1994, the metal concentrations in lichens decreased, but metal deposits in the southeastern area were cause for concern. High concentrations of lead in the area are related to emissions from a waste incinerator and a plant that produces lead oxide. Epidemiological investigations reveal that the area population has the highest levels of lead in their blood. The use of bioindicators and bioaccumulators permits long-term and large-scale monitoring of environmental pollutant levels in full agreement with traditional methods.