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951.
Surface water methane(CH4) and nitrous oxide(N2O) concentrations and fluxes were investigated in two subtropical coastal embayments(Bramble Bay and Deception Bay,which are part of the greater Moreton Bay, Australia). Measurements were done at 23 stations in seven campaigns covering different seasons during 2010–2012. Water–air fluxes were estimated using the Thin Boundary Layer approach with a combination of wind and currents-based models for the estimation of the gas transfer velocities. The two bays were strong sources of both CH4 and N2O with no significant differences in the degree of saturation of both gases between them during all measurement campaigns. Both CH4 and N2O concentrations had strong temporal but minimal spatial variability in both bays.During the seven seasons, CH4 varied between 500% and 4000% saturation while N2O varied between 128 and 255% in the two bays. Average seasonal CH4 fluxes for the two bays varied between 0.5 ± 0.2 and 6.0 ± 1.5 mg CH24/(m·day) while N2 O varied between 0.4 ± 0.1 and1.6 ± 0.6 mg N2O/(m2·day). Weighted emissions(t CO2-e) were 63%–90% N2 O dominated implying that a reduction in N2 O inputs and/or nitrogen availability in the bays may significantly reduce the bays' greenhouse gas(GHG) budget. Emissions data for tropical and subtropical systems is still scarce. This work found subtropical bays to be significant aquatic sources of both CH4 and N2O and puts the estimated fluxes into the global context with measurements done from other climatic regions. 相似文献
952.
The Maximum Experimental Safe Gap (MESG) is an important criterion to assess the propagation of flames through small gaps. This safety-related parameter is used to classify the flammable gases and vapors in explosion groups, which are fundamental to constructional explosion protection. It is used both, for the safe design of flameproof encapsulated devices as well as for selecting flame arresters appropriate to the individual application. The MESG of a fuel is determined experimentally according to the standard ISO/IEC 80079-20-1:2017 at normal conditions (20 °C, 1.0 bar) with air as oxidizing gas. The aim of this work is to investigate the effect of inert gas addition on the MESG in order to assess the effectiveness of inertization in constructional explosion protection. The term limiting experimental safe gap (SG) is used for the result of these measurements. The fuel-air mixtures (fuels: hydrogen, ethylene, propene, methane) used as representatives for the explosion groups in flame arrester testing were chosen and diluted with inert gas (nitrogen, carbon dioxide) before testing. The dependence of the limiting experimental safe gap on the total initial pressure, amount and nature of inert additive is discussed. The initial pressure was varied up to 2.0 bar to include increased pressure conditions used in flame arrester testing. Apart from the well-known reciprocal dependence on the initial pressure, the added inert gas results in an exponential increase of SG. This effect depends on the inertizing potential of the gas and is therefore different with nitrogen and carbon dioxide. The ranking of the fuels is the same as with MESG. As a result, various mixtures of the same limiting experimental safe gap can now be chosen and tested with an individual flame arrester to prove the concept of a constant and device-related limiting safe gap. The work was funded by BG-RCI in Heidelberg (PTB grant number 37056). 相似文献
953.
氧化锰八面体分子筛的合成及其对苯催化氧化性能 总被引:1,自引:1,他引:0
采用回流的方法,制备了氧化锰八面体分子筛(OMS-2)纳米棒.利用X射线衍射(XRD)、扫描电子显微镜(SEM)、氮气吸附-脱附、程序升温还原(H2-TPR)分别对产物进行晶型、形貌、孔径和H2还原性能进行分析,并考察不同煅烧温度下的催化剂对苯的催化氧化性能及300℃煅烧催化剂的稳定性.结果表明,煅烧温度对氧化锰八面体分子筛(OMS-2)的表面特征有显著的影响,煅烧温度越高,比表面积和孔容越小,平均孔径越大.同时随着煅烧温度的增加,催化剂对苯的催化氧化性能降低.经300℃煅烧的催化剂对苯的催化活性最佳,反应温度为200℃时,苯的转化率达到了50%;当反应温度为250℃时,苯的转化率达到90%.经300℃煅烧的催化剂在260℃下70 h内,对苯的催化氧化性能降低了5%,具有良好的稳定性. 相似文献
954.
Flaky and nanospherical birnessite and birnessite-supported Pt catalysts were successfully prepared and characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS) and N2 adsorption-desorption. Effects of the birnessite morphology and Pt reduction method on the catalytic activity for the complete oxidation of formaldehyde (HCHO) were investigated. It was found that flaky birnessite exhibited higher catalytic activity than nanospherical birnessite. The promoting effect of Pt on the birnessite catalyst indicated that the reduction method of the Pt precursor greatly influenced the catalytic performance. Flaky birnessite-supported Pt nanoparticles reduced by KBH4 showed the highest catalytic activity and could completely oxidize HCHO into CO2 and H2O at 50℃, whereas the sample reduced using H2-plasma showed lower activity for HCHO oxidation. The differences in catalytic activity of these materials were jointly attributed to the effects of pore structure, surface active sites exposed to HCHO and the dispersion of Pt nanoparticles. 相似文献
955.
以Fe(NO3)3为前驱物,制备了水合氧化铁吸附剂样品,以NaOH为解吸剂,研究了样品对模拟废水中磷酸根的吸附和解吸性能。结果表明,水合氧化铁对磷酸根有较好的吸附效果;随着pH的降低,水合氧化铁对磷酸根的吸附能力增强,在pH为2时吸附达92.5%;吸附前15 min吸附速率较快,约150 min达到平衡,吸附动力学曲线符合二级动力学模型;用水合氧化铁对初始浓度为50~100 mg/L模拟含磷废水吸附,随着初始浓度的增大,磷的去除率下降;水合氧化铁对磷酸根的吸附等温线较符合Langmuir吸附模型;用NaOH对水合氧化铁行解吸,浓度为40 g/L有最好的解吸率,60 min时达到解吸平衡。 相似文献
956.
以萘酚蓝黑为模型污染物,采用动力学方法研究了δ-MnO2颗粒杂质对亚微米级商品TiO2(C)、ZnO(C)和纳米级自制TiO2(N)、ZnO(N)光催化作用的影响,并通过紫外-可见漫反射光谱(UV-vis DRS)和荧光光致发光光谱(PL)对试样进行了表征。结果表明,δ-MnO2能导致2种TiO2严重失活,而对2种ZnO的光催化活性影响很小。δ-MnO2导致TiO2光催化剂失活的主要原因为:能提高TiO2的带隙能,以及作为深能级杂质促进光生电子与空穴之间的复合。 相似文献
957.
Nitrous oxide emission and reduction in a laboratory-incubated paddy soil response to pretreatment of water regime 总被引:9,自引:0,他引:9
IntroductionNitrousoxide (N2 O)isagreenhousegas.IncreasingatmosphericN2 Oconcentrationmayalsobedetrimentaltothestratosphericozonelayer(Crutzen ,1981) .AgriculturalsoilisamajorsourceofN2 O .MostN2 Ooriginateswithsoilprocesses,asanintermediateproductfrommic… 相似文献
958.
一氧化二氮(NO2)是一个重要的温室效应气体,一氧化氮(NO)对温室效应的产生也有间接的作用。土壤作为这两种气体的主要来源的重要性引起了人们的广泛重视。本文主要讨论了土壤中的氮素生物转化过程与NO2和NO的产生和再利用。以及影响土壤中温室效应气体的释放和吸收的环境条件。 相似文献
959.
960.