The H2/CO ratio of emissions from combustion sources: comparison of top-down with bottom-up measurements in southwest Germany

The hydrogen-to-carbon monoxide (H₂/CO) emission ratio of anthropogenic combustion sources was determined from more than two years of quasi-continuous atmospheric observations in Heidelberg (49°24' N, 8°42' E), located in the polluted Rhein-Neckar region. Evaluating concurrent mixing ratio changes of H₂ and CO during morning rush hours yielded mean molar H₂/CO ratios of 0.40 ± 0.06, while respective results inferred from synoptic pollution events gave a mean value of 0.31 ± 0.05 mole H₂/mole CO. After correction for the influence of the H₂ soil sink on the measured ratios, mean values of 0.46 ± 0.07 resp. 0.48 ± 0.07 mole H₂/mole CO were obtained, which are in excellent agreement with direct source studies of traffic emissions in the Heidelberg/Mannheim region (0.448 ± 0.003 mole H₂/mole CO). Including results from other European studies, our best estimate of the mean H₂/CO emission ratio from anthropogenic combustion sources (mainly traffic) ranges from 0.45 to 0.48 mole H₂/mole CO, which is about 20% smaller than the value of 0.59 mole H₂/mole CO which is frequently used as the basis to calculate global H₂ emissions from anthropogenic combustion sources.     

Application of a textural geospeedometer to the late‐stage magmatic history of MIL 03346

Abstract— Dynamic crystallization experiments performed on Fe‐rich, Al‐poor basalt are employed as a textural calibration set to quantify the late‐stage igneous history of nakhlite Miller Range (MIL) 03346. The ratio of crystal‐melt surface area to volume typifying morphologically distinct populations of Ca‐pyroxene has been shown to vary as a strong function of cooling rate (Hammer 2006). Furthermore, a texture of phenocrysts surrounded by finer‐grained groundmass crystals arises by sequential nucleation events during constant‐rate cooling, but multiple populations nucleate only if the cooling rate is 72 °C h^?1. Textural analysis of meteorite MIL 03346 reveals at least two distinct populations. The Ca‐pyroxene phenocryst and microphenocryst three dimensional (3D) aspect ratios are 112 ± 8.3 and 1530 ± 160 mm^?1, respectively. By comparison with the calibration set, the range of cooling rates consistent with 3D aspect ratios of both populations in MIL 03346 is ?20 °C h^?1An additional experiment was performed approximating a conductive heat transfer profile in order to interpret and apply results of constant‐rate cooling experiments to the natural cooling of magma. Results suggest that the textures of constant‐rate experiments parallel the initial period of rapid cooling in natural magma. Initial cooling rates of ?20 °C h^?1in the lava hosting MIL 03346 occur in conductively solidifying lava at depths of?0.4 m, constraining the minimum total thickness to 0.8 m. Crystal accumulation beginning in a subsurface reservoir and continuing after lava emplacement as an inflated pahoehoe sheet satisfies all textural constraints on the late‐stage igneous history of MIL 03346.     

Seasonal variation of the molecular hydrogen uptake by soils inferred from continuous atmospheric observations in Heidelberg, southwest Germany

The dominant sink of atmospheric molecular hydrogen (H₂) is its enzymatic destruction in soils. Quantitative estimates of the global sink strength, as derived from bottom-up process studies, are, however, still associated to large uncertainties. Here we present an alternative way to estimate atmosphere-to-soil flux densities, respectively deposition velocities of H₂, based on atmospheric H₂ and ²²²Rn observations in the boundary layer. Two and a half years of continuous measurements from a polluted site in the Rhine-Neckar area have been evaluated and night-time flux densities were calculated for situations of strong nocturnal boundary layer inversions using the Radon-Tracer Method. The influences from local anthropogenic combustion sources could be detected and successfully separated by parallel measurements of carbon monoxide. Inferred daily uptake fluxes in the Heidelberg catchment area range from 0.5 to 3 × 10⁻⁸ g H₂ m⁻² s⁻¹ with a mean value of (1.28 ± 0.31) × 10⁻⁸ g H₂ m⁻² s⁻¹. Uptake rates are about 25% larger during summer than during winter, when soil moisture is high, and diffusive transport of H₂ into the soil is inhibited. The mean deposition velocity is 3.0 ± 0.7 × 10⁻² cm s⁻¹_, which is very well in line with direct measurements on similar soil types in Europe and elsewhere.     

COMMODIFYING THE ATMOSPHERE: ‘PENNIES FROM HEAVEN’*?

The atmosphere may be the most valuable resource on Earth and is worth orders of magnitude more to society than it costs as a hazard. However, the atmosphere, and information about the atmosphere, are increasingly being transformed from being considered as part of a global commons to being conceived of as a global commodity to be bought and sold. There are three basic types of atmospheric commodity: firstly, the material atmosphere itself; secondly, the physical properties of the atmosphere; and thirdly, data or information or predictions about the atmosphere. The global expenditure on national meteorological and climatological services and research has now been surpassed by the value of new economic instruments such as weather derivatives and climate emissions trading. Atmospheric scientists, climatologists and physical geographers need to be critically aware of what the consequences, both positive and negative, of these developments for science and society might be. This is particularly the case as climate change is increasingly providing new discourses for companies and governments to exploit as the atmosphere becomes a tradable green resource. This paper attempts to construct an initial critical framework of analysis drawing from broader literatures on the commodification of nature.     

Mechanisms and Sources of Mantle Metasomatism: Major and Trace Element Compositions of Peridotite Xenoliths from Spitsbergen in the Context of Numerical Modelling

Mineral and whole-rock chemical data for peridotite xenolithsin basaltic lavas on Spitsbergen are examined to reassess mechanismsof melt–fluid interaction with peridotites and their relativerole versus melt composition in mantle metasomatism. The enrichmentpatterns in the xenoliths on primitive mantle-normalized diagramsrange from Th–La–Ce ‘inflections’ inweakly metasomatized samples (normally without amphibole) toa continuous increase in abundances from Ho to Ce typical foramphibole-bearing xenoliths. Numerical modelling of interactionbetween depleted peridotites and enriched melts indicates thatthese patterns do not result from simple mixing of the two end-membersbut can be explained by chromatographic fractionation duringreactive porous melt flow, which produces a variety of enrichmentpatterns in a single event. Many metasomatized xenoliths havenegative high field strength element and Pb anomalies and Srspikes relative to rare earth elements of similar compatibility,and highly fractionated Nb/Ta and Zr/Hf. Although amphiboleprecipitation can produce Nb–Ta anomalies, some of thesefeatures cannot be attributed to percolation-related fractionationalone and have to be a signature of the initial melt (possiblycarbonate rich). In general, chemical and mineralogical fingerprintsof a metasomatic medium are strongest near its source (e.g.a vein) whereas element patterns farther in the metasomatic‘column’ are increasingly controlled by fractionationmechanisms. KEY WORDS: Spitsbergen; lithospheric mantle; metasomatism; trace elements; theoretical modelling     

Investigation of parameters controlling the soil sink of atmospheric molecular hydrogen

Enclosure measurements have been performed on a bare mineral soil at an experimental field site near Heidelberg, Germany. From observed molecular hydrogen (H₂) mixing ratio changes in the enclosure, deposition velocities were calculated ranging from  8.4 × 10⁻³  to  8.2 × 10⁻² cm s⁻¹  and with an annual mean value of  3.1 × 10⁻² cm s⁻¹  . In the studied range of  2– 27 °C  , the uptake showed a significant temperature dependence. However, this turned out not to be the primary driving mechanism of the uptake flux. Soil moisture content, co-varying with temperature, was identified as the major parameter being responsible for the diffusive permeability of H₂ in the soil and the final rate of H₂ uptake. A simple Millington–Quirk diffusion model approach could largely explain this behaviour and yielded a diffusion path length of H₂ in the studied soil of only 0.2–1.8 cm, suggesting that total H₂ consumption occurs within the first few centimetres of the soil. The diffusion model, when applied to continuous measurements of soil moisture content, atmospheric pressure, temperature and the mixing ratio of H₂ in the atmosphere, could largely reproduce the measured deposition flux densities, assuming a mean thickness of the diffusion path length of 0.7 cm.     

星系金属丰度的研究进展(Ⅰ):定标方法

金属丰度是表征星系特征的重要参量,对于理解星系的形成与演化具有重要意义。随着观测设备的不断完善与发展,已经获得越来越多的星系(包括近邻星系、中等红移及高红移星系)金属丰度的观测资料。在光致电离模型方面也取得了很大进展．这些对于理解星系中金属及恒星成分的累积历史有非常重要的作用。有多种方法可以用来估计星系的金属丰度(主要是星际介质中气相的O丰度),介绍和评述了估计星系的O丰度的多种方法,包括电子温度的方法、R23方法以及其他一些“强线”比值的方法,并给出了相应的解析公式,同时介绍了电离星云的物理本质及由光致电离模型估计星系金属丰度的方法,还给出了估计星系的C和N元素丰度的方法。