Evaluation of the carbon isotopic effects of NDIR and CRDS analyzers on atmospheric CO2 measurements

Non-dispersive infrared(NDIR) and cavity ring-down spectroscopy(CRDS) CO_2 analyzers use 12CO_2 isotopologue absorption lines and are insensitive to all or part of other CO_2-related isotopologues. This may produce biases in CO_2 mole fraction measurements of a sample if its carbon isotopic composition deviates from that of the standard gases being used. To evaluate and compare the effects of carbon isotopic composition on NDIR and CRDS CO_2 analyzers, we prepared three test sample air cylinders with varying carbon isotopic abundances and calibrated them against five standard cylinders with ambient carbon isotopic composition using CRDS and NDIR systems. We found that the CO_2 mole fractions of the sample cylinders measured by G1301(CRDS) were in good agreement with those measured by Lo Flo(NDIR). The CO_2 values measured by both instruments were higher than that of a CO_2 isotope measured by G2201i(CRDS) analyzer for a test cylinder with depleted carbon isotopic composition δ~(13)C =-36.828‰, whereas no obvious difference was found for other two test cylinders with δ~(13)C=-8.630‰ and δ~(13)C=-15.380‰, respectively. According to the theoretical and experimental results, we concluded that the total CO_2 mole fractions of samples with depleted isotopic compositions can be corrected on the basis of their 12CO_2 values calibrated by standard gases using Lo Flo and G1301 if the δ~(13)C and δ18O values are known.     

Les argiles bleues du Cambrien inférieur de Saint-Pétersbourg et leur fissuration. Implications pour des stockages souterrains

The Lower Cambrian Saint Petersburg blue clays are composed of predominant illite and chlorite, sometimes accompanied by kaolinite. The <0.1 μm fraction has a high content of illite–smectite mixed layers. Particle-size distribution is more than 50% of clay particles and about 30% of silts. These blue clays correspond to plastic (and soft) clays; they may be compared to the Callovian clays of Bure (France), where storage of natural waste is envisaged. To cite this article: M. Arnould et al., C. R. Geoscience 334 (2002) 1135–1140.

Résumé

Les « argiles bleues » du Cambrien Inférieur de Saint-Pétersbourg sont constituées d'illite dominante et de chlorite, avec parfois présence de kaolinite. Des interstratifiés illite/montmorillonite sont très abondants dans la phase <0,1 μm. Du point de vue granulométrique, outre plus de 50% de particules argileuses, il existe une phase silteuse de l'ordre de 30%. Du point de vue pétrophysique, ce sont des argiles plastiques, de consistance molle. Elles sont subhorizontales et ont jusqu'à 116 m d'épaisseur. Outre l'absence de métamorphisme, malgré leur âge, leur caractère le plus remarquable est leur réseau de fracturation, bien observable en carrière. Les joints sont nets, sans remplissage ni cimentation. Les plans verticaux sont particulièrement développés. Le volume unitaire des blocs de matrice ne dépasse guère 1 m³. Des traces d'oxydation témoignent de circulations d'eau. Ces argiles silteuses anciennes peuvent aider à mieux connaı̂tre et comprendre les argilites silteuses épigénétiques calloviennes du site de Bure (Haute-Marne, France), où un stockage souterrain de déchets nucléaires est envisagé. Pour citer cet article : M. Arnould et al., C. R. Geoscience 334 (2002) 1135–1140.     

Stochastic gravitational fluctuations of stellar or galactic systems with a fractal distribution of field sources

The stochastic gravitational fluctuations for a fractal mass distribution are analyzed by means of a functional integral approach. A general method is developed for evaluating the stochastic properties of vectorial additive random fields generated by a variable number of point sources obeying inhomogeneous Poisson statistics. A closed expression for the generating functional of the field is given in terms of the generating functional of the sources. The moments of the resulting vectorial field are finite if the correlation functions of the sources have short tails. In this case all cumulants of the field can be computed exactly: they are averages of the central moments of sources computed in terms of the probability density of the position of a source. The method is applied for analyzing the stochastic gravitational fluctuations generated by a fractal distribution of field sources (stars or galaxies). For a Newtonian force law the correlation functions of the sources are slowly decaying, the cumulants of the stochastic gravitational field are infinite and the probability density of the field intensityF is given by a Lévy fractal stable law with a scaling exponentH depending on the fractal dimensiond _f of the distribution of stars or galaxies:H =d _f /2.     

Resonant behaviour of MHD waves on magnetic flux tubes

The absorption of solar five-min oscillations by sunspots is interpreted as the resonant absorption of sound waves by a magnetic cylinder. The absorption coefficient is calculated both analytically under certain simplifying assumptions, and numerically under more general conditions. The observed magnitude of the absorption coefficient, which is up to 0.5 or even more, can be explained for suitable ranges of parameters. Limitations in the present model are also discussed.     

Les hyaloclastites de la rive nord du lac Kivu (Congo)

Geological environment and origin of the palagonitised tuff volcanoes of the Kivu. Petrographical features (lapilli, palagonitisation, gangue). Their magmatic minerals and xenoliths.     

Announcement Internatioal Society for Diatom Research and Nederlands-Vlaamse Kring van Diatomisten

Announcement Internatioal Society for Diatom Research and Nederlands-Vlaamse Kring van Diatomisten     

Solar radio fluxes as indices of solar activity

The daily solar radio flux values at 9400, 3750, 2000 and 1000 MHz and at 2800 MHz observed since 1957 at Toyokawa and Ottawa, respectively, have been used to provide new information on the solar radio fluxes as indices of solar activity. After an examination of the yearly mean values at each frequency, another investigation based on mean ratios during periods of 18 or 6 months indicates that a close connection is observed between the radio fluxes in the cm region and that anomalies related to calibration problems can be detected. The regression analysis of the daily values of the fluxes during at least 25 years and a special test on the sensitivity may provide final information on the stability of the data with respect to time and solar activity. The method is capable of detecting long-term trends corresponding to instrumental drifts. Such information is essential to our understanding of anomalies detected in the observations of u.v. and X-ray irradiances. However, such a method is based on a linear relationship. When a quadratic form, as it is observed in the decimeter region, is adopted, the effect of the various levels of activity in a solar cycle must be considered.     

Non-adiabatic discrete Alfvén waves in coronal loops and prominences

Discrete Alfvén waves in coronal loops and prominences are investigated in non-ideal magnetohydrodynamics. The non-ideal effects included are anisotropic, thermal conduction, and optically thin radiation. The classic ideal Alfvén continuum is not altered by these non-ideal effects, but the discrete Alfvén modes, which exist under certain conditions above or below the Alfvén continuum in ideal MHD, are shown to be influenced by non-adiabatic effects.The existence of discrete, non-adiabatic Alfvén waves, and their damping and overstability are examined for 1D cylindrical equilibrium states with twisted magnetic fields. First, analytic results are obtained for modes of high radial order by means of a WKB-analysis. The subspectrum of discrete Alfvén modes is computed with a numerical code, with particular emphasis on the modes of low radial order. The results show that discrete Alfvén waves are of potential importance for solar applications and also that the information obtained with the WKB-analysis is of limited use in this context.Research Assistant of the Belgian National for Scientific Research.     

In situ measurements of sediment settling characteristics in floodplains using a LISST‐ST

Due to a lack of data on settling velocities (w_s) and grain size distributions (GSDs) in ?oodplain environments, sedimentation models often use calibrated rather than measured parameters. Since the characteristics of suspended matter differ from those of deposited sediment, it is impossible to derive the w_s and GSD from the latter. Therefore, one needs to measure in situ suspended sediment concentrations (SSCs), settling velocities, effective grain sizes and sedimentation ?uxes. For this purpose we used the LISST‐ST, a laser particle sizer combined with a settling tube. In 2002 (twice) and 2004, we located the LISST‐ST with an optical backscatter sensor and sediment traps in two ?oodplains in The Netherlands: one along the unembanked IJssel River, another along the embanked Waal River. Measurements revealed that the SSC in the ?oodplains varied in relation to the SSC in the river channel. Smaller ?ocs dominated the SSC, while larger ?ocs dominated the potential sedimentation ?uxes. The in situ GSD in the IJssel ?oodplain was signi?cantly coarser than in the Waal ?oodplain, while the dispersed median grain sizes were equal for both ?oodplains. Therefore, the dispersed median grain size was two to ?ve times smaller than the effective one. The in situ grain size exhibited a signi?cant positive relationship with w_s, although the w_s for the largest ?ocs showed high variability. Consequently, the variability in sedimentation ?uxes was also large. In the actual sedimentation ?uxes, and hence in sedimentation models, in situ grain sizes up to about 20 µm can be neglected. In ?oodplain sedimentation models the relation between settling velocity and in situ grain size can be used instead of Stokes's law, which is only valid for dispersed grain sizes. These models should also use adequate data on ?ow conditions as input, since these strongly in?uence the suspended sediment characteristics. Copyright © 2005 John Wiley & Sons, Ltd.