Composition and major sources of organic compounds in urban aerosols

Total suspended particles (TSP), collected during June 2002 to July 2003 in Guangzhou, a typical economically developed city in South China, were analyzed for the organic compound compositions using gas chromatography–mass spectrometry (GC/MS). Over 140 organic compounds were detected in the aerosols and grouped into different classes including n-alkanes, hopanoids, polycyclic aromatic hydrocarbons, alkanols, fatty acids, dicarboxylic acids excluding oxalic acid, polyols/polyacids, lignin products, phytosterols, phthalates and water-soluble sugars. The total amounts of the identified organic compounds including unresolved complex mixture (UCM) ranged from 3112 ng/m³ in spring to 5116 ng/m³ in winter, comprising on seasonal average 2.8% of TSP. Primary organic compounds peaked in winter although there are no heating systems burning fuels in Guangzhou. The highest saccharide levels occurred in fall due to agricultural activities. This study demonstrated that utilization of fossil fuels, biomass burning, soil resuspension and plastic/refuse burning are the major contributors to the identified organic compounds in the urban atmosphere of South China.     

Lander radioscience for obtaining the rotation and orientation of Mars

The paper presents the concept, the objectives, the approach used, and the expected performances and accuracies of a radioscience experiment based on a radio link between the Earth and the surface of Mars. This experiment involves radioscience equipment installed on a lander at the surface of Mars. The experiment with the generic name lander radioscience (LaRa) consists of an X-band transponder that has been designed to obtain, over at least one Martian year, two-way Doppler measurements from the radio link between the ExoMars lander and the Earth (ExoMars is an ESA mission to Mars due to launch in 2013). These Doppler measurements will be used to obtain Mars’ orientation in space and rotation (precession and nutations, and length-of-day variations). More specifically, the relative position of the lander on the surface of Mars with respect to the Earth ground stations allows reconstructing Mars’ time varying orientation and rotation in space.Precession will be determined with an accuracy better by a factor of 4 (better than the 0.1% level) with respect to the present-day accuracy after only a few months at the Martian surface. This precession determination will, in turn, improve the determination of the moment of inertia of the whole planet (mantle plus core) and the radius of the core: for a specific interior composition or even for a range of possible compositions, the core radius is expected to be determined with a precision decreasing to a few tens of kilometers.A fairly precise measurement of variations in the orientation of Mars’ spin axis will enable, in addition to the determination of the moment of inertia of the core, an even better determination of the size of the core via the core resonance in the nutation amplitudes. When the core is liquid, the free core nutation (FCN) resonance induces a change in the nutation amplitudes, with respect to their values for a solid planet, at the percent level in the large semi-annual prograde nutation amplitude and even more (a few percent, a few tens of percent or more, depending on the FCN period) for the retrograde ter-annual nutation amplitude. The resonance amplification depends on the size, moment of inertia, and flattening of the core. For a large core, the amplification can be very large, ensuring the detection of the FCN, and determination of the core moment of inertia.The measurement of variations in Mars’ rotation also determines variations of the angular momentum due to seasonal mass transfer between the atmosphere and ice caps. Observations even for a short period of 180 days at the surface of Mars will decrease the uncertainty by a factor of two with respect to the present knowledge of these quantities (at the 10% level).The ultimate objectives of the proposed experiment are to obtain information on Mars’ interior and on the sublimation/condensation of CO₂ in Mars’ atmosphere. Improved knowledge of the interior will help us to better understand the formation and evolution of Mars. Improved knowledge of the CO₂ sublimation/condensation cycle will enable better understanding of the circulation and dynamics of Mars’ atmosphere.     

Realization of X-ray telescopes–from design to performance

For more than 45 years the building of X-ray telescopes for solar and astronomical observations has been practised with significant performance improvement. The various techniques applied are reviewed emphazising the impact of proper mirror material choice, grinding and polishing improvements and the role of metrology.     

哀牢山-红河剪切带左行走滑作用起始时间约束

位于哀牢山-红河剪切带NW延伸方向上的点苍山变质杂岩体遭受强烈的左行走滑剪切变形、变质作用改造,岩石中保存了典型的高温矿物组合以及由它们构成的宏观和微观高温变形构造特征,其中糜棱岩中具有极其发育的长石矿物拉伸线理而形成典型的L与LS型构造岩是其一个明显的特征。本文对点苍山地区高温糜棱岩主要矿物开展了显微构造与矿物变形、变形机制及组构分析,并对于遭受高温糜棱岩化改造的一个花岗质岩体开展了SHRIMP锆石U-Pb定年分析。结果表明岩石中长石、角闪石、石英等主要矿物具有典型的达角闪岩相条件下的高温晶质塑性变形和动态生长特征,它们也为走滑剪切变形活动提供了充分的微观构造证据。对于点苍山高温糜棱岩化改造的眼球状或似斑状二长花岗岩的显微构造分析结果表明,这套花岗质岩石从走滑剪切前期岩浆的侵位之后经历了早期强烈的岩浆期后交代作用—亚岩浆流动—高温固态塑性剪切变形的递进演化过程。由此可见,岩浆的上升与就位受左行走滑剪切作用的制约,岩体又遭受了强烈剪切变形改造。同时对这套构造前期就位花岗质岩石中的锆石进行定年分析,获得33.88±0.32Ma的岩浆结晶年龄,为此,我们有充分的理由认为,在点苍山地区哀牢山-红河剪切带左行走滑剪切作用的起始时间至少应该为早渐新世30.88±0.32Ma。     

A high‐resolution relative time scale for the Viséan Stage (Carboniferous) of the Kulm Basin (Rhenish Mountains,Germany)

The Viséan (Carboniferous) sedimentary succession of the basinal Kulm facies (Rhenish Mountains) was investigated in detail in order to achieve a high‐resolution stratigraphic subdivision and correlation. Additionally, the ranges of fossil index taxa (ammonoids), fossil marker beds, volcaniclastic horizons and sedimentary features (e.g. colour changes) were integrated in the correlation. As a result, a comprehensive database was compiled, which contains 190 stratigraphic events of the Viséan interval of this area. Several sections are almost completely composed of shales, which are regarded to represent a slow but constant basinal background sedimentation of the Kulm facies. The thickness of lithological homogeneous sections thus indicates an approximately linear record of time and the average thicknesses of biozones and positions of stratigraphic events can easily be calculated from the compiled database. The result is an approximately time‐linear biostratigraphic scale for the Viséan Stage of the Kulm Basin. Given a numerical length of the Viséan Stage of ca. 19 Ma, 190 stratigraphic events give a mean resolution of 100 000 years. This is unique in Palaeozoic stratigraphy. Copyright © 2008 John Wiley & Sons, Ltd.     

The topography of Iapetus' leading side

We have used Cassini stereo images to study the topography of Iapetus' leading side. A terrain model derived at resolutions of 4-8 km reveals that Iapetus has substantial topography with heights in the range of −10 km to +13 km, much more than observed on the other middle-sized satellites of Saturn so far. Most of the topography is older than 4 Ga [Neukum, G., Wagner, R., Denk, T., Porco, C.C., 2005. Lunar Planet. Sci. XXXVI. Abstract 2034] which implies that Iapetus must have had a thick lithosphere early in its history to support this topography. Models of lithospheric deflection by topographic loads provide an estimate of the required elastic thickness in the range of 50-100 km. Iapetus' prominent equatorial ridge [Porco, C.C., and 34 colleagues, 2005. Science 307, 1237-1242] reaches widths of 70 km and heights of up to 13 km from their base within the modeled area. The morphology of the ridge suggests an endogenous origin rather than a formation by collisional accretion of a ring remnant [Ip, W.-H., 2006. Geophys. Res. Lett. 33, doi:10.1029/2005GL025386. L16203]. The transition from simple to complex central peak craters on Iapetus occurs at diameters of 11±3 km. The central peaks have pronounced conical shapes with flanking slopes of typically 11° and heights that can rise above the surrounding plains. Crater depths seem to be systematically lower on Iapetus than on similarly sized Rhea, which if true, may be related to more pronounced crater-wall slumping (which widens the craters) on Iapetus than on Rhea. There are seven large impact basins with complex morphologies including central peak massifs and terraced walls, the largest one reaches 800 km in diameter and has rim topography of up to 10 km. Generally, no rings are observed with the basins consistent with a thick lithosphere but still thin enough to allow for viscous relaxation of the basin floors, which is inferred from crater depth-to-diameter measurements. In particular, a 400-km basin shows up-domed floor topography which is suggestive of viscous relaxation. A model of complex crater formation with a viscoplastic (Bingham) rheology [Melosh, H.J., 1989. Impact Cratering. Oxford Univ. Press, New York] of the impact-shocked icy material provides an estimate of the effective cohesion/viscosity at . The local distribution of bright and dark material on the surface of Iapetus is largely controlled by topography and consistent with the dark material being a sublimation lag deposit originating from a bright icy substrate mixed with the dark components, but frost deposits are possible as well.     

Comparison of Five Numerical Codes for Automated Tracing of Coronal Loops

The three-dimensional (3D) modeling of coronal loops and filaments requires algorithms that automatically trace curvilinear features in solar EUV or soft X-ray images. We compare five existing algorithms that have been developed and customized to trace curvilinear features in solar images: i) the oriented-connectivity method (OCM), which is an extension of the Strous pixel-labeling algorithm (developed by Lee, Newman, and Gary); ii) the dynamic aperture-based loop-segmentation method (developed by Lee, Newman, and Gary); iii) unbiased detection of curvilinear structures (developed by Steger, Raghupathy, and Smith); iv) the oriented-direction method (developed by Aschwanden); and v) ridge detection by automated scaling (developed by Inhester). We test the five existing numerical codes with a TRACE image that shows a bipolar active region and contains over 100 discernable loops. We evaluate the performance of the five codes by comparing the cumulative distribution of loop lengths, the median and maximum loop length, the completeness or detection efficiency, the accuracy, and flux sensitivity. These algorithms are useful for the reconstruction of the 3D geometry of coronal loops from stereoscopic observations with the STEREO spacecraft, or for quantitative comparisons of observed EUV loop geometries with (nonlinear force-free) magnetic field extrapolation models.     

Authigenic albite in carbonate rocks – a tracer for deep-burial brine migration?

Euhedral, post-depositional albite from the Eastern and Western Alps, the western Carpathians and some Greek islands was examined petrographically and geochemically to gain insights into the nature of feldspar reactions in carbonate rocks. This study focuses on coarsely crystalline, homogeneously nucleated albite in order to avoid problems related to the presence of inseparable detrital material in fine-grained albite varieties. All albite samples show a very restricted compositional variability and are typically ≥ 99 mol% Ab component. Unit-cell parameters determined by Rietveld analysis are slightly more variable than previously accepted, but confirm high Al–Si ordering characteristic of low albite. The oxygen isotopic composition of albite ranges from + 19·4‰ to + 28·3‰ VSMOW. There is no direct relationship between the δ¹⁸O value and the inferred temperature of albite formation, nor is there one with stoichiometry. The coarse crystal size (up to several millimetres in diameter), petrographic evidence showing albite cross-cutting stylolites, greater abundance of albite in carbonate rocks subject to high-grade diagenetic or weak metamorphic overprinting and available fluid inclusion data suggest that albite precipitation is favoured at higher temperatures in carbonates than in sandstones. Pore fluids were invariably brines, as suggested by the inferred high positive δ¹⁸O_fluid values, the common association of albite-bearing carbonates and evaporites and reports of saline fluid inclusions in albite. The presence of authigenic albite may thus be a useful tracer of palaeobrine–carbonate reactions, particularly in deep-burial and incipient metamorphic settings.     

Evaluation of recent hydro-climatic changes in four tributaries of the Niger River Basin (West Africa)

West Africa experienced severe drought during the 1970s and 1980s, posing a threat to water resources. A wetter climate more recently suggests recovery from the drought. The Mann-Kendall trend and Theil-Sen’s slope estimator were applied to detect probable trends in weather elements in four sub-basins of the Niger River Basin between 1970 and 2010. The cross-entropy method was used to detect breakpoints in rainfall and runoff, Spearman’s rank test for correlation between the two, and cross-correlation analysis for possible lags. Results showed an overall increase in rainfall and runoff and a decrease in sunshine duration. Spearman’s coefficients suggest significant (5%) moderate to strong rainfall–runoff correlation for three sub-basins. A significant lower runoff was observed around 1979, with a rainfall break around 1992, indicating possible cessation of the drought. Temperatures increased significantly, at 0.02–0.05°C year^-1, with a negative wind speed trend for most stations. Half of the stations exhibited an increase in potential evapotranspiration.

EDITOR M.C. Acreman

ASSOCIATE EDITOR Not assigned     

Hydrological system analysis and modelling of the Kara River basin (West Africa) using a lumped metric conceptual model

This paper discusses the analysis and modelling of the hydrological system of the basin of the Kara River, a transboundary river in Togo and Benin, as a necessary step towards sustainable water resources management. The methodological approach integrates the use of discharge parameters, flow duration curves and the lumped conceptual model IHACRES. A Sobol sensitivity analysis is performed and the model is calibrated by applying the shuffled complex evolution algorithm. Results show that discharge generation in three nested catchments of the basin is affected by landscape physical characteristics. The IHACRES model adequately simulates the rainfall–runoff dynamics in the basin with a mean modified Nash-Sutcliffe efficiency measure of 0.6. Modelling results indicate that parameters controlling rainfall transformation to effective rainfall are more sensitive than those routing the streamflow. This study provides insights into understanding the catchment’s hydrological system. Nevertheless, further investigations are required to better understand detailed runoff generation processes.

EDITOR M.C. Acreman; ASSOCIATE EDITOR N Verhoest