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Monitoring CO2 concentration and δ13C in an underground cavity using a commercial isotope ratio infrared spectrometer
Sophie Guillon1,2,
Pierre Agrinier2 &
Éric Pili1
Applied Physics B volume 119, pages 165–175 (2015)Cite this article
CO2 stable carbon isotopes are very attractive in environmental research to investigate both natural and anthropogenic carbon sources. Laser-based isotope ratio infrared spectrometers (IRIS) allow in situ continuous monitoring of CO2 isotopes, and therefore they have a potential for unprecedented understanding of carbon sources and dynamics with a high temporal resolution. Here we present the performance assessment of a commercial IRIS analyzer, including the measurement setup and the data processing scheme that we used. Even if the analyzer performs 1-Hz measurements, an integration time of the order of 1 h is commonly needed to obtain acceptable precision for δ13C. The main sources of uncertainty on δ13C come from the concentration dependence and from the temporal instability of the analyzer. The method is applied to the in situ monitoring of the CO2 carbon isotopes in an underground cavity (Roselend Natural Laboratory, France) during several months. On a weekly timescale, the temporal variability of CO2 is dominated by transient contamination by human breath. Discarding these anthropogenic contaminations, CO2 and δ13C backgrounds do not show diurnal or seasonal fluctuations. A CO2 flux released into the tunnel by the surrounding rocks is measured. The carbon isotope composition of this CO2, identified with a Keeling plot, is consistent with a main production by microbial respiration and a minor production from weathering of carbonate minerals. The presented instrument and application study are relevant to cave monitoring, whether to understand CO2 dynamics in visited and/or painted caves for preservation purposes or to understand paleoclimate recording in speleothems.
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CO2 stable isotopes are widely used to study the sources and fates of carbon in the atmosphere, hydrosphere and geosphere, as well as the exchanges between these reservoirs.
For around 10 years, commercial analyzers have been available, based on isotope ratio infrared spectroscopy (IRIS). These analyzers have a high temporal resolution and low power consumption and allow long-term continuous in situ monitoring of carbon isotopes in the field, which was not possible with classical isotope ratio mass spectrometry (IRMS). Several IRIS analyzers now exist for measuring CO2 carbon and oxygen isotopes that are based on different technologies [1–5]. However, studies using such commercial analyzers have revealed difficulties to obtain reliable and accurate data. They also emphasized the need for users to thoroughly assess the analyzers' performance in the field and to establish calibration strategies to correct raw data for the identified biases [3, 6]. Commercial IRIS instruments are often designed for atmospheric monitoring and present good accuracy at low and not strongly variable CO2 concentration [3, 7, 8]. But there is also a need for carbon isotope monitoring at higher and more variable concentrations, in volcanic [2] or underground [9] environments, as well as for soil [10] and fermentation plants monitoring [11].
Here we focus on CO2 carbon isotope monitoring in geological media, where the CO2 concentration is large and is known to be variable [12, 13]. First, the performances of the commercial analyzer were determined in the laboratory in terms of precision, linearity and response time, allowing to establish a data processing method. Then, we apply the method to the monitoring of CO2 in the atmosphere of an underground cavity during several months. The carbon cycle is investigated at the Roselend Natural Laboratory (French Alps) using isotope ratios, in order to identify the carbon sources and fates, to quantify respective fluxes, to appreciate the dynamics of the carbon system and to explain it in terms of forcing factors. Crystalline rocks, present around the Roselend tunnel, have indeed been showed to be net sources of CO2 to the atmosphere [14]. This article aims to show what can be done with supposedly easy-to-use commercial instruments and to emphasize the work that is required to obtain accurate and reliable data as well as the numerous caveats and the large uncertainties.
Commercial laser-based isotope analyzer
In this study, we used the Los Gatos Research CCIA-EP (CO2 Carbon Isotope Analyzer-Enhanced Performance, purchased in mid-2011), a commercial IRIS analyzer based on off-axis integrated cavity output spectroscopy. The technique is described in detail in [15]. This is an enhanced performance version of the instrument presented in [6]. It is mainly characterized by a better thermal insulation, aimed at decreasing the observed large sensitivity to external temperature variations. CO2 concentration, carbon and oxygen isotopes, as well as water content, are measured using absorption lines around 2.05 µm (D. Baer, pers. comm.). Pressure and temperature in the optical cavity are constant at 45.20 ± 0.05 °C and 39 torr, respectively. Air flow through the instrument is driven by its internal diaphragm pump and is around 0.5 L min−1. Data acquisition is done at 1 Hz.
Here, we mainly focus on the CO2 carbon isotope measurement because, from our point of view, oxygen isotope measurement with this instrument still requires improvement in precision and in the availability of calibration standards. CO2 carbon isotope composition is reported as δ13C versus VPDB standard (Vienna Pee Dee Belemnite), and reported in per mil (‰), where
$$\updelta^{13} \hbox{C}\left( {\permille} \right) = \left( {\frac{{R_{\text{sample}} }}{{R_{\text{VPDB}} }} - 1} \right) \times 1,\!000\,{\permille}$$
where \(R = ([{}^{13}{\text{C}}]/[{}^{12}{\text{C]}})_{{{\text{CO}}_{2} }}\).
Reference gases
Reference gases (Air Products) were used for the performance assessment of the analyzer in the laboratory as well as for calibration during field monitoring. For the reference gases to be as close as possible to the measured gases, they consisted of CO2 in a matrix with 78 % N2, 21 % O2 and 1 % Ar. Both these reference gases and the sample gases are passed through a drying unit, to keep moisture as constant and as low as possible in the analyzer. This drying unit (Fig. 1) consists in a 30-cm Nafion® tubing embedded in a desiccant (Drierite®) mounted in line with another Nafion® tubing embedded in a stainless tube, with a counterflow of dry air provided by the exhaust of the analyzer. This drying unit works as a true drying unit for the moist sample gases (with average moisture content of 12,000 ppm), whereas it actually acts as a humidifier for the dry reference gas streams. The average moisture content downstream this drying unit is of few thousands ppm. Reference gases A, F and G (Table 1) were used for the performance assessment in the laboratory. Reference gases B–E were used for calibration during field monitoring. CO2 concentrations of these reference gases correspond to the minimum and maximum values of CO2 concentration expected during monitoring, about 350–900 ppm. All CO2 and H2O concentrations are reported in parts per million per volume, noted ppm for the sake of brevity. CO2 concentrations are known within 0.5 % from the certified values given by the manufacturer. The δ13C values of these reference gases were measured by CF-IRMS (Gas Bench II and DeltaPlusXP, Thermo Finnigan) at the Institut de Physique du Globe de Paris. Precision on δ13C values is better than 0.3 ‰.
Experimental setup used for in situ monitoring of CO2 concentration and δ13C in the Roselend Natural Laboratory. See text for details. In the drying unit, the dashed lines stand for Nafion® tubings, the shaded zone for Drierite®
Table 1 CO2 concentration and carbon isotope composition δ13C of the reference gases used in this study
Performance assessment in the laboratory
Three tests were conducted in the laboratory to assess the performance of the analyzer.
First, the Allan–Werle deviation is a widely accepted tool in the diode-laser spectroscopy community that quantifies the intrinsic precision of the analyzer and highlights its stability or drift, in order to determine data integration time and frequency of calibrations. It is defined as the deviation between adjacent data as a function of data averaging time [16, 17]:
$$\sigma_{\text{Allan}}^{2} \left( \tau \right) = \frac{1}{2}\left\langle {\left( {\mathop \delta \limits^{ - }_{{t_{k} + \tau }} - \mathop \delta \limits^{ - }_{{t_{k} }} } \right)^{2} } \right\rangle , \quad\mathop \delta \limits^{ - }_{{t_{k} }} (\tau ) = \frac{1}{\tau }\mathop \smallint \limits_{{t_{k} }}^{{t_{k} + \tau }} \delta \left( t \right) dt$$
where τ is averaging time, 〈〉 is the expectation value, and k and k + τ are adjacent averaged data. The Allan–Werle deviation was determined from 2-h-long continuous measurements of reference gases, for CO2 concentration as well as for carbon and oxygen isotope compositions. This was done for three reference gases (A, F and G) with concentrations of 300, 2,002 and 17,800 ppm CO2.
Second, the response time of the analyzer following a stepwise change of concentration and isotope composition of the inlet gas was determined by switching between two reference gases (A–F, A–G and F–G). The response time determines the high-frequency limit of the CO2 dynamics that can be retrieved with this analyzer.
Third, the δ13C dependence on CO2 concentration is known to be one of the largest sources of uncertainty for IRIS analyzers [3, 7, 9, 18, 19] and needs to be carefully checked. Reference gases with 17,800 as well as 2,002 ppm CO2 concentrations (F and G, Table 1) were stepwise diluted by CO2-free synthetic air with 78 % N2, 21 % O2 (Air Products), using two mass flow controllers (SLA5850S, Brooks, range 1 L min−1). We assume that the mass flow controllers induce no fractionation.
The enhanced version of the Los Gatos Research IRIS analyzer has an improved thermal insulation, and measurements were taken either in the laboratory where temperature is controlled (at ±0.3 °C) or in an underground tunnel where the temperature is naturally very stable at 7.2 ± 0.2 °C. We therefore did not have to investigate the effect of ambient temperature variations on the measurement, which has nonetheless been shown to be a large source of drift and error [6, 7].
Monitoring of CO2 carbon dynamics in an underground cavity
The study site is the Roselend Natural Laboratory [20], located in the French Alps. This underground research laboratory mainly consists in a horizontal tunnel hosted in bare fractured crystalline rocks. The tunnel is 128-m long, with a 2.4-m diameter. It is naturally ventilated by ambient atmospheric air at its open end. All along the tunnel, water is dripping from rocks. At mid-length of the tunnel, a side excavation of approximately 9 m length and 3 m width, called Inner Room, was roughly isolated by a steel door and sealing foam.
An IRIS analyzer had already been used at this site to measure CO2 carbon dynamics in a small borehole [6]. Here we present a long-term monitoring of CO2 dynamics in the tunnel and in the Inner Room. The analyzer was installed in a portion of the tunnel where the water drip rate is very low, so that it did not require to be especially protected.
The experimental setup of the analyzer for in situ continuous monitoring is shown in Fig. 1. A multi-inlet unit with eight ports (MIU, Los Gatos Research) was used to automatically switch at selected time periods between the streamlines, one from the open tunnel, one from the isolated Inner Room and two from the non-diluted reference gases (B and E in 2013, C and D in 2014). The drying unit was installed between the MIU outlet and the analyzer inlet (Fig. 1). Air was drawn from the tunnel and from the reference gas cylinders through 6.4-mm external diameter PFA tubing. A similar, 8-m long tubing, passing through the rock above the Inner Room's door, was used to draw air from the Inner Room. This tubing was inserted 2 m inside the Inner Room. A pressure gauge and a 10-psi check valve (Swagelok®) were fixed at the inlet of the CCIA-EP, in order to prevent any overpressure that would damage the analyzer (Fig. 1).
During the monitoring period, from April to June 2013, and then from May to July 2014, the analyzer was measuring at 1-Hz rate the CO2 concentration and δ13C of air from the tunnel or from the Inner Room. The MIU automatically switched between the two sample streamlines every 2 h, while the high- and low-concentration reference gases were measured every 8 h during 5 min. The concentration dependence of the analyzer was checked manually every month, following the protocol presented above. This protocol has been defined according to the results of experiments about performance of the analyzer. No data were recorded during several periods due to various types of failures (laser drift, software error and power surge).
Performance of the analyzer
The Allan–Werle deviations for δ13C and δ18O were calculated following Eq. (1) [16, 17] and are presented in Fig. 2. Precision, given by the Allan–Werle deviation, increases with averaging time due to white noise averaging and also increases when CO2 concentration increases (Fig. 2). At CO2 concentration higher than 2,000 ppm, the optimum precision (σ = 0.05 ‰) for δ13C is reached for an averaging time of 200 s; while at 300 ppm, the optimum precision (σ = 0.08 ‰) is only reached after 900 s. For longer averaging time, precision gets worse due to long-term drift. A good precision (σ = 0.02 %) on CO2 concentration is obtained at 60 s averaging time. The precision on δ18O measurement (Fig. 2b) is one order of magnitude worse than of δ13C (Fig. 2a). An averaging time of 20 min is thus required to obtain a precision of σ = 0.4 ‰ for δ18O.
Allan plots for a δ13C and b δ18O of CO2 from three reference gases. Allan–Werle deviations were computed following [17], for reference gases with concentrations of 300 ppm (black), 2,002 ppm (dark gray) and 17,800 ppm (light gray). Precision (σ) for 1 s and 60 s averaging times, as well as best precision (σ min), are summarized in tables
As several combinations of reference gases were used to determine the response time of the analyzer, data were first normalized to the difference in concentration or isotope composition between the two measured gases. How fast the analyzer reaches a new steady state after a stepwise change in inlet composition is quantified using the 5–95 % response time [21], i.e., the time needed for the measurement to go from 5 to 95 % of the difference between the initial and final values. After a change in the sample gas concentrations and delta values at the inlet of the multi-inlet unit, the analyzer response remains stable and equal to the initial values for some time, while the inlet gas has already been changed. This delay is interpreted to be due to piston-like propagation of air through the tubing between the multi-inlet switching valve and the inlet of the optical cavity in the analyzer. The average delay that was obtained for this propagation is 20.3 ± 1.7 s and does not depend on the difference in concentration or isotope composition. Then, a classical exponential increase or decrease response was observed, with a 5–95 % response time on average of 30 s for CO2 concentration and 60–100 s for isotope composition values. This response time suggests the existence of dead volumes in the instrument that take some time to be purged. Response time cannot be reduced with the commercial analyzer used in this study, because cell pressure and flow rate cannot be changed.
Stepwise dilution with zero air was performed and repeated at various time intervals, for the two reference gases having 2,002 and 17,800 ppm CO2 concentrations (F, G, Table 1). Results for δ13C are presented in Fig. 3. The dependence of δ13C on the CO2 concentration can be up to 19 ‰ in the concentration range 300–17,800 ppm, and 6 ‰ in the more limited concentration range 300–1,000 ppm. At high CO2 concentrations, typically higher than 5,000 ppm, the dependence law is linear (Fig. 3a), with quite a good reproducibility of the slope (0.0013 ± 0.0002 ‰ ppm−1). At low CO2 concentration, the situation is more complex. The dependence law appears to be stable at the hourly timescale (data not shown). At the daily timescale, a strong variability is observed (Fig. 3b). However, the dependence law keeps the same shape, being randomly shifted (up to 5 ‰ in 24 h). This leads to propose a simple way to handle this correction while using the analyzer unattended: the shift and global shape of the law are evaluated every few hours by automatically running at least two reference gases, while the more detailed shape of the dependence law must be checked every month by manually running a stepwise dilution of a reference gas.
Concentration dependence of δ13C measurement. a up to 17,800 ppm CO2; b in the range 400–2,000 ppm CO2. δ13C is reported as raw values. Stepwise dilutions of reference gases G (a) and F (b) with CO2-free air were repeated several times
Calibration and data processing
For each data set acquired in the field, temperature in the optical cavity was monitored. It was stable within ±0.05 °C; therefore, no temperature correction was applied. While water concentration measured in the tunnel without using the drying unit was around 12,000 ppm, the measured water concentration using the drying unit slowly increased from 1,000 to 5,000 ppm during the whole measurement period, indicating the decreasing efficiency of the drying unit as the Drierite got progressively saturated. Longer Nafion tubing and more Drierite may mitigate this problem. Humidity levels were on average 1,000 ppm higher in samples than in reference gases. These humidity values, reduced and similar in sample and reference gases, allow us to reduce uncertainty linked to measurement and calibration.
Based on the above performance and concentration dependence measured in the laboratory, as well as on methodologies proposed by others [3, 7], the following calibration method was used to process the raw data. Raw data files from the CCIA-EP analyzer were first handled with a program written in Fortran, in order to:
sort out the data for the two samples and the two reference gases that were measured,
remove 2 min of data after switching from one sample to another,
reduce the amount of data by averaging them on a 1-min basis.
Although the 1-min averaging of the raw data does not give the best precision, as shown by the Allan–Werle deviation, this averaging time was chosen in order to reduce the large amount of data acquired at 1 Hz, while keeping a good temporal resolution. The two measured reference gases are used for calibrating concentrations as well as δ13C values, taking into account the dependence on concentration. From 300 s of measurement of the two reference gases conducted every 8 h, the first 100 s are removed, and CO2 concentration and δ13C values are averaged over the last 200 s. This leads to one average value of CO2 concentration and δ13C every 8 h, for each reference gas. A linear time interpolation is then used to reconstruct the time series of reference CO2 concentration and δ13C with a 1-min time step.
A linear calibration of the raw CO2 concentration ([CO2]meas) is then applied:
$$\left[ {{\text{CO}}_{2} } \right]_{\text{corr}} - \left[ {{\text{CO}}_{2} } \right]_{\text{meas}} = q\left( t \right) \cdot \left[ {{\text{CO}}_{2} } \right]_{\text{meas}} + r(t)$$
where [CO2]corr is the corrected CO2 concentration and q(t) and r(t) are the two calibration parameters, which vary with time. These parameters are determined at each time step (i.e., every minute in the presented case) from the interpolated CO2 concentrations for the two reference gases. The corrections for the concentration dependence on δ13C measurement, as well as calibration of δ13C value against the international PDB scale, are then applied. As we have no physical model for the concentration dependence law, and based on the concentration dependence measurements (Fig. 3b), we chose a linear relation between the shift on δ13C and the CO2 concentration:
$$\left( {\updelta^{13} {\text{C}}} \right)_{\text{corr}} - \left( {\updelta^{13} {\text{C}}} \right)_{\text{meas}} = u\left( t \right) \cdot \left[ {{\text{CO}}_{2} } \right]_{\text{corr}} + v(t)$$
where (δ13C)meas is the raw value of carbon isotope composition given by the analyzer, (δ13C)corr is the corrected value in the PDB scale, [CO2]corr is the concentration after calibration using Eq. (3), and u(t) and v(t) are two calibration parameters which vary with time. These parameters are determined from the interpolated δ13C values for the two reference gases. This relation is valid and can be applied only for CO2 concentrations in the range 400–1,000 ppm, where the concentration dependence law was shown to be linear (Fig. 3b). Corrected CO2 concentration and δ13C data are finally averaged with a 1-h time step. This time step gives a good accuracy, with a temporal resolution that is high enough to investigate most dynamics. The calibration and averaging procedures were automated using a MATLAB program.
Long-term field monitoring in an underground cavity
The raw measurements of the reference gases are presented in Fig. 4. When the analyzer was running unattended for weeks, large drifts of δ13C values were observed, especially between May and July, 2014. The temporal evolution of the calibration parameters q(t), r(t), u(t) and v(t), calculated as explained above, is shown in Fig. 5. The intercepts r(t) for [CO2] calibration (Fig. 5a) and v(t) for δ13C calibration (Fig. 5b) particularly vary with time, while the slopes q(t) and u(t) vary less. This is consistent with the previous observation that the concentration dependence law is randomly shifted with time, while varying monotonously on a daily timescale and keeping the same shape. Corrections that have to be applied to the raw δ13C values are of large amplitude, typically on average of −8 ‰, and vary with time. This seriously decreases the accuracy and the precision of the measurements.
Reference gases measurements of δ13C (a) and CO2 concentration (b) during a total of 3 months (April and June 2013, May to July 2014). The analyzer was set up in the tunnel. Two reference gases with high (gray, E in 2013, D in 2014) and low (black, B in 2013, C in 2014) CO2 concentrations were measured and used for calibration. See Table 1 for their CO2 concentration and δ13C values. Reported data are 1-min averages
Temporal stability of calibration parameters during the field monitoring period. a Slope q(t) (black) and intercept r(t) (gray) of the CO2 concentration correction according to Eq. (1). b Slope u(t) (black) and intercept v(t) (gray) of the δ13C correction according to Eq. (2)
The raw data obtained for the tunnel and the Inner Room were processed as detailed in the previous section. The corrected CO2 concentration and δ13C values are presented in Fig. 6. CO2 concentrations range from 400 to 1,000 ppm in the tunnel and from 530 to 800 ppm in the Inner Room. δ13C values in the tunnel and in the Inner Room range from −4 to −20 ‰. In the tunnel, transient peaks of CO2 concentration are observed on April 12, 2013, April 27, 2013, June 4, 2013, May 21, 2014 and July 11, 2014, because of the addition of CO2 produced by the breathing of people working in the tunnel. In 2014, these CO2 peaks are also observed in the Inner Room, simultaneously with those in the tunnel. In April 2013, CO2 concentration is observed to increase from 590 to 800 ppm in the Inner Room.
Monitoring of δ13C (a) and CO2 concentration (b) in the tunnel (black) and the Inner Room (red) from April to June 2013, and May to July 2014. Reported data are corrected, 1-h averages, after 2-point calibration using reference gases measured every 8 h (cf Fig. 3). Contamination by human breathing appears as spikes in CO2 concentrations and negative excursions in δ13C. Squares correspond to δ13C values measured by CF-IRMS on discrete samples taken from the tunnel (black) and the Inner Room (red)
Real-life performance of the IRIS analyzer and recommendations
Here we give some recommendations for in situ monitoring with the LGR CCIA-EP analyzer that can be extended to other commercial IRIS analyzers. A major focus has to be made on two points: (1) the instability of the analyzer with time and (2) the strong dependence of the measured δ13C on CO2 concentration.
Dealing with the temporal instability of the analyzer
It is generally noted that currently available IRIS analyzers, which display high theoretical and short-term laboratory performances, have significantly degraded performances when set in outdoor conditions. In addition to the intrinsic functioning of the analyzer and the aging of the laser, the long-term drift of the analyzer is caused by environmental parameter changes such as temperature and humidity. The sensitivity of the instrument to these varying conditions must then be carefully characterized in order to correct the raw data. In order to reduce the amplitude of corrections, we strongly advise users to work at regulating as much as possible the climatic ambiance of the analytical system. In particular, it is better to keep the water concentration as low and stable as possible, by drying sampled air and arranging the same amount of water in samples and reference gases.
Even if it is better to limit the amplitude of the corrections as much as possible, the errors induced by variable temperature or water concentration could also be considered and corrected if it is not possible to have such a well-controlled environment as in this experiment. Further experimental studies on the role of water content, and more generally on matrix effects, on δ13C measurement are required for a better understanding of the induced errors.
Although not mentioned in the instruction manual and not straightforward for all users, it is recommended that the analyzer run uninterrupted in order to limit instabilities and drifts. Because of this limited stability of the instrument, the status of the analyzer and of the measurements must be checked at least every week, and the potential laser wavelength drift as well as the quality of the fit of the absorption lines must be controlled.
Even if measurements are taken every second, an integration time of several minutes up to 1 h is required during field monitoring, in order to obtain a precision better than 0.5 ‰ for δ13C. At the moment, the LGR CCIA-EP does not allow us to investigate faster temporal dynamics, such as high-frequency data required for eddy covariance [22]. The eddy covariance (also known as eddy correlation or eddy flux) is a key atmospheric measurement technique to measure and calculate vertical turbulent fluxes within atmospheric boundary layers.
Dealing with the strong concentration dependence of the isotope ratio
The large amplitude of the concentration dependence correction (up to 8 ‰ for concentrations in the range 300–800 ppm) is the major source of uncertainty. A linear approximation for the concentration dependence law is commonly used for IRIS analyzers [3, 7, 18]. The concentration dependence law obtained in this study is consistent with this approximation, as least in the limited range of concentration that was investigated. A linear law proved to perform well for calibration of δ13C values during field monitoring. If fundamental spectroscopic information on the analyzer were available, this could potentially be used to determine the shape of the concentration dependence curves, based on physical principles. At present time, users have to rely on empirical laws with no spectroscopic basis.
Because of the instability of the analyzer, reference gases have to be measured frequently, at least twice a day, to track the concentration dependence law. As a linear law was used, at least two reference gases must be analyzed. These reference gases have to be carefully chosen to have the same matrix composition and to bracket the range of CO2 concentrations of the measured air.
Even if it was not the case in this study, addition of a third reference gas, with CO2 concentration in the measured range, would be very useful as a quality check. Regular checks of the concentration dependence law, on a weekly basis, are highly recommended in order to track any change in shape or too large drift. Validation of IRIS data against the traditional IRMS method is strongly advised. This was done here, at least with a limited number of comparison points. The agreement, and therefore the analyzer's performance, is not fully satisfactory, with a variable discrepancy of 1–4 ‰ (Fig. 6). As shown by the Allan–Werle deviation (Fig. 2a), a large uncertainty of 1–3 ‰ is expected due to the interval of 8 h between calibrations. This time interval could be reduced to 1 h, to reduce uncertainty, while keeping a reasonable consumption of reference gases and enough time for sample measurements.
Natural δ13C dynamics in an underground cavity
Contamination by human breathing and ventilation
Large peaks in CO2 concentration are observed in the tunnel on April 12, 2013, April 27, 2013, June 4, 2013, May 21, 2014 and July 11, 2014. They occurred when visits or field works were conducted in the tunnel and result from contamination by human respiration.
While all events increased CO2 concentration, only the largest (on May 21, 2014) significantly modified its δ13C, with a small negative peak (Fig. 6). Human breath has δ13C values between −20 and −23 ‰, with CO2 concentration of several percent [23–25]. As the isotope signature of human breathing is lower than that of the background in the tunnel (δ13C ≈ −8 to −15 ‰), the resulting δ13C decreases during CO2 peaks. In comparison, human breathing imprint in the air of the Inner Room was limited, thanks to its closed and roughly isolated door. However, the appearance of peaks in the Inner Room in May, 2014, indicates that the Inner Room became less isolated from the tunnel.
A simple mixing model between CO2 in the tunnel air and CO2 from human breathing can thus be used:
$$C_{\text{peak}} = x \,C_{\text{breath}} + \left( {1 - x} \right) \,C_{\text{tun}}$$
$$\delta_{\text{peak}} \cdot C_{\text{peak}} = x \,\delta_{\text{breath}} \cdot C_{\text{breath}} + \left( {1 - x} \right) \,\delta_{\text{tun}} \cdot C_{\text{tun}}$$
where x is the fraction of contamination, C peak (resp. δ peak) refers to peak value of CO2 concentration (resp. carbon isotope composition), C tun (resp δ tun) are the corresponding values in the tunnel before the peak and C breath (resp. δ breath) the values for human breathing. Peak and tunnel values are taken from the measurements; carbon isotope composition of exhaled air is supposed to be −23 ‰ [23]. From Eqs. (5) and (6), CO2 concentration in exhaled air is found to be around 15,000 ppm and the volume fraction of contamination by human breathing to be of 2 %. This value of C breath is lower than the few % measured directly in the exhaled air [24], which is explained by the rapid dilution of exhaled air by the low CO2 concentration tunnel air.
Depending on how many people are present in the tunnel, how long they stay and where they are located (or moving) with respect to the inlet of the IRIS analyzer, the shapes of the peaks may vary. A characteristic exponential decay results from the natural ventilation of the tunnel [26, 27]. These transient CO2 perturbations by human breathing can be used to quantify the natural ventilation in the tunnel. Assuming that the source of the CO2 perturbation is no more active after the peak and using a box model to describe the decay of the CO2 concentration, the following equation is obtained:
$$C\left( t \right) = \left( {C_{i} - C_{\infty } } \right) \cdot {\text{e}}^{{ - \lambda_{v} t}} + C_{\infty }$$
where C(t) is the CO2 concentration measured in the tunnel, C i is the maximum peak concentration, C ∞ the background CO2 concentration in the tunnel, and λ v is the ventilation rate (in s−1). For the large CO2 peak measured in the tunnel between May 21 and 28, 2014, C i = 715 ppm is the maximum initial concentration and C ∞ = 425 ppm is the final stable concentration after decay (Fig. 6). The best fit of the decay curve (R 2 = 0.91) is obtained for a ventilation rate λ v = 1.0 ± 0.2 10−5 s−1. This value of the ventilation rate is similar to the one obtained from other tracers (222Rn and SF6) for the same area of the tunnel [24]. A modified box model can then be applied to obtain the evolution of δ13C in the tunnel during the decay of the CO2 concentration:
$$\updelta^{13} C\left( t \right) = \frac{{\left( {\delta_{i} \cdot C_{i} - \delta_{\infty } \cdot C_{\infty } } \right) \cdot e^{{ - \lambda_{v} t}} + \delta_{\infty } \cdot C_{\infty } }}{{\left( {C_{i} - C_{\infty } } \right) \cdot e^{{ - \lambda_{v} t}} + C_{\infty } }}$$
where δ i and δ ∞ are, respectively, the peak and background carbon isotope compositions of CO2. With the value of the ventilation rate determined above for the decay of the CO2 concentration, an acceptable fit of the δ13C evolution is obtained (R 2 = 0.45). This poorer fit is explained by the limited range of variation in the δ13C values, not so large compared to the precision of the analyzer.
Contributing fluxes of CO2
First, discarding the peaks of anthropogenic origin, the averaged background CO2 concentrations in both the tunnel and the Inner Room are higher than that measured in the atmosphere (390 ± 10 ppm [28] ), with 410 ± 10 and 550 ± 10 ppm, respectively. Second, the increase in CO2 concentration observed in the Inner Room in April 2013 is lower than the more abrupt peaks of breathing contamination and occurred when there were no people working in the tunnel. These two observations have to be explained by another CO2 source in addition to atmosphere and respiration. These CO2 excesses indicate that a CO2 flux is coming from the rock (hereafter referred to as geogenic CO2) and allow us to estimate this flux. A simple mass balance leads to the differential equation governing the CO2 concentration in the tunnel or the Inner Room:
$$\frac{{{\text{d}}C}}{{{\text{d}}t}} = \frac{S}{V} \frac{R T}{{P_{\text{a}} M_{{{\text{CO}}_{2} }} }}\Phi - \lambda_{v } (C - C_{\text{a}} )$$
where C is the CO2 concentration in the tunnel or in the Inner Room, S (resp. V) is the surface area of the walls (in m2) (resp. the volume in m3), R is the ideal gas constant, T is the tunnel temperature (in K), P a is the average atmospheric pressure (850 hPa at the Roselend Natural Laboratory), \(M_{{{\text{CO}}_{2} }}\) = 44 g mol−1 is the molecular mass of CO2, C a = 380 ppm is the CO2 concentration in the atmosphere, λ v is the ventilation rate (in s−1), and Ф is the flux of CO2 released by the rock (in g m−2 day−1). At steady state, the flux Ф can be calculated from the average CO2 concentration C∞ that is measured in the tunnel or in the Inner Room according to the following equation:
$$\Phi = \frac{V}{S} \frac{{P_{\text{a}} M_{{{\text{CO}}_{2} }} }}{RT}\lambda_{v } \,(C_{\infty } - C_{\text{a}} )$$
Using a ventilation rate of 1.0 × 10−5 s−1 in the tunnel, as determined previously, a lower value of 3 × 10−6 s−1 in the Inner Room (according to [26]), and steady state concentrations of 410 and 550 ppm in the tunnel and the Inner Room, respectively, we obtained CO2 fluxes of 0.02 g m−2 day−1 in the tunnel and 0.05 g m−2 day−1 in the Inner Room. These values are 5–10 times lower than the one of 0.11 g m−2 day−1 previously obtained in a borehole (Perm 4) that laterally extends 2.3 m into the host rock from the tunnel wall [6]. This difference is explained by the difference of the spatial scale of the surfaces contributing to the CO2 flux (0.06 m2 for the borehole, 61 m2 for the Inner Room, and 98 m2 for the portion of tunnel where the analyzer is installed and which is delimited by plastic curtains [26] ). While the small borehole Perm 4 represents a high CO2 flux end-member, rock areas with high and low fluxes (corresponding chiefly to matrix-dominated and fracture-dominated areas) are averaged in the larger tunnel and Inner Room.
Sources of CO2
Carbon isotope composition gives insights into the sources of CO2 production and release from rocks. The data obtained in this study using the IRIS analyzer, in both the tunnel and the Inner Room, are plotted in a Keeling plot (δ13C vs. 1/[CO2], Fig. 7). Discrete air samples were also taken for CF-IRMS analysis from borehole Perm 4 and from Chamber C. Chamber C is a 60 m3 cavity, similar to the Inner Room, but isolated from the tunnel by an air-tight wall. Both Chamber C and borehole Perm 4 were completely isolated from the tunnel during the experiment, which allows CO2 to accumulate and leads to concentrations higher than those obtained in the tunnel and in the Inner Room. Both Chamber C and borehole Perm 4 remained free of contamination by human breathing.
Keeling plot (CO2 carbon isotope composition versus the inverse of the CO2 concentration) from long-term in situ monitoring in the tunnel (black squares) and the Inner Room (red squares) with the LGR CCIA-EP analyzer (IRIS). Reported data are corrected 1-h averages from Fig. 6, except for periods when the tunnel was contaminated by human breathing and that have been removed. Measurements of δ13C by CF-IRMS in samples taken from chamber C (red circles) and borehole Perm 4 (purple triangles) are also reported. The linear trend in the data highlighted by the gray lines corresponds to a 2 end-member mixing between atmospheric air (blue star, 430 ± 20 ppm CO2, δ13C = −7.7 ± 0.5 ‰, values determined from the Keeling plot and in the upper range from that given in [28]) and pore space air (≥10,000 ppm CO2, δ13C = −25 ± 2 ‰), this later value being determined from the intercept of the linear regression (gray circle)
CO2 in these four environments, tunnel, Inner Room, Chamber C and borehole Perm 4 consists in a mixing between atmospheric CO2 and geogenic CO2. This two end-member mixing corresponds to a linear trend in a Keeling plot. This is indeed what is observed here with the whole data set (Fig. 7). The carbon isotope composition of the CO2 released by the rock is given by the intercept of the mixing line with the vertical axis, following [29, 30]. The obtained value of δ13C = −25 ± 3 ‰ is consistent with that of −23.7 ± 0.5 ‰ obtained from a flux measurement performed in borehole Perm 4 [6].
Such isotope composition is at first order consistent with that of the CO2 degassed from HCO3 − dissolved in water dripping from the roof of the tunnel (with pH in the range 7.7–8.1) [6]. The δ13C value of dissolved HCO3 − was measured at −10.9 ± 1.5 ‰ [14], and the isotope fractionation at 7 °C between CO2 and dissolved HCO3 − is −9.6 ‰ [31, 32], which leads to a δ13C value of −20.5 ± 1.5 ‰ for degassed CO2. This range in isotope composition of HCO3 − is consistent with production by microbial and plant respiration of C3 organic matter [33], in the soil at the surface and in the 55 m of rocks above the tunnel, with some contribution from weathering of carbonate minerals [34].
No clear seasonal variability can be seen in the obtained data, neither for CO2 concentration nor for δ13C values (Fig. 6). In the Inner Room, no change in δ13C occurred during the increase in CO2 concentration observed April 2013. This suggests an increase in the intensity of the CO2 flux released by the rock without the addition of another CO2 source.
Further monitoring would be required to investigate in more detail the temporal variability of carbon isotope composition in dissolved HCO3 −, degassed CO2, carbon sources and transport processes.
The performance assessment of the commercial IRIS analyzer LGR CCIA-EP shows that despite fast measurement rate (1 Hz) and response time, an integration time of several minutes up to 1 h is required to obtain a precision better than 0.5 ‰ on δ13C, almost comparable to IRMS performance and required for discrimination of natural carbon sources. We emphasize the difficulties encountered by any user to process, correct and calibrate raw data. The two main sources of uncertainty that have to be carefully taken into account are the dependence of δ13C on CO2 concentration and the temporal instability of the analyzer.
As shown here as well as in other works using commercial IRIS analyzers [3, 7], there is a need for development and validation of data processing schemes, available to the users' community, in order to ensure accurate and reliable measurements.
IRIS analyzers offer an unprecedented possibility of long-term in situ monitoring of CO2 isotope composition in a variety of natural environments. This is very promising for understanding the spatial and temporal dynamics of δ13C and carbon sources, for example, by investigating the time variability of Keeling plot intercept, as it is done for ecosystem respiration [30].
The presented instrument and application study are relevant for monitoring underground cavities, whether to understand CO2 dynamics in visited and/or painted caves for preservation purposes [35] or to understand paleoclimate recording in speleothems [36]. However, in these applications with high CO2 concentrations or CO2 concentrations varying in a large range, using IRIS, remains very challenging at the moment. Further work would be required to validate protocols and data processing schemes adapted to these conditions and to the various commercial IRIS analyzers.
We presented in situ monitoring of CO2 and δ13C at the Roselend Natural Laboratory with a high temporal resolution and for a total of 3 months between April 2013 and July 2014. Transient peaks of CO2 concentration are due to contamination by human breathing and allow us to quantify the ventilation rate. Discarding these peaks, the CO2 background higher than the atmospheric one allows us to quantify a net CO2 flux that is shown to be contributed by the rock. δ13C of this geogenic CO2 flux is determined with a Keeling plot and is consistent with production by plant and microbial respiration at the surface as well as production from weathering of carbonate minerals in the rock. A one-month transient increase in CO2 concentration is observed, due to an increase in the geogenic CO2 flux, but no diurnal or seasonal variability of CO2 and δ13C is detected from the measurements.
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We thank Carine Chaduteau for her help with IRMS measurements. We thank Doug Baer, Feng Dong and other people at Los Gatos Research for their availability, advice and help in using this analyzer in specific conditions. Thanks go to Didier Mondelain for introducing us to laser-based isotope analysis and to Allan–Werle variance. Benjamin Richard is being thanked for the systematic analysis of the analyzer performance in the laboratory. We thank Erik Kerstel and an anonymous reviewer for their thoughtful comments that helped improving the manuscript. This is IPGP Contribution Number 3574.
CEA, DAM, DIF, 91297, Arpajon, France
Sophie Guillon & Éric Pili
Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Univ Paris Diderot, UMR 7154 CNRS, 75005, Paris, France
Sophie Guillon & Pierre Agrinier
Sophie Guillon
Pierre Agrinier
Éric Pili
Correspondence to Sophie Guillon.
Open Access This article is distributed under the terms of the Creative Commons Attribution License which permits any use, distribution, and reproduction in any medium, provided the original author(s) and the source are credited.
Guillon, S., Agrinier, P. & Pili, É. Monitoring CO2 concentration and δ13C in an underground cavity using a commercial isotope ratio infrared spectrometer. Appl. Phys. B 119, 165–175 (2015). https://doi.org/10.1007/s00340-015-6013-4
Issue Date: April 2015
Carbon Isotope Composition
Ventilation Rate
Isotope Ratio Mass Spectrometry
Underground Cavity
Keeling Plot


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All across the various environments of Monster Hunter World, hunters can find Bazelgeuse roaming the skies. While mainly found in the Elder's Recess, this monster has a habit of popping up in every location at one time or another to take on any large monster it comes across. While this beast does not have many standard attacks, it has a unique bomb mechanic that keeps the monster protected and makes it difficult to hunt. Let's take a look at some tips and tricks on navigating this monster's personal minefield.
Bazelgeuse has large scales covering the underside of its body, primarily on its neck and wide tail. These scales can be easily shaken off by the monster, and when agitated, will begin to glow bright red and explode after a few moments. While the hunter is attacking the monster they can be knocked off around it, making the area difficult to navigate and attack up close. When attacking the monster, it is very easy to accidentally hit one of the scales on the ground causing an explosion and knocking the hunter back. Try to agitate them while they are lying on the ground and move away quickly, out of the explosive range. Once one goes off, it will begin to set others off around it in a chain reaction that will clear out the area quickly.
At certain points during the battle, Bazelgeuse will fly high into the air where the monster will fly back and forth across the combat area of the map, shaking its body and laying down a trail of scales. After flying back and forth twice, the monster will then turn to its target and dive-bomb them, causing heavy blunt damage, massive knock-back, and setting off any scales near the point of impact to begin a chain reaction along the path it has laid down. When the monster begins this attack, try to agitate the scales right from the beginning to begin the chain reaction and clear out as many as possible before the dive-bomb happens. When the monster begins to fly into the ground, run to the left or right of the direction the monster is heading to get out of the impact zone as quickly as possible. If not far enough away, the aftershock can stagger the hunter, allowing an easy opening for a follow-up attack.
Bazelgeuse has two major basic attacks to watch out for. First, the monster will rise up on its hind legs and, after a few moments, body slam into the ground in front of it, causing knock-back and stagger if the hunter is too close to the impact. During this attack run away from the monster to avoid aftershock or, if too close to the monster, dive toward its tail to avoid the danger zone. Second, Bazelgeuse will charge forward slightly and slam its head into the ground, then while still moving forward, rear its head back throwing up rocks around the area in front of it. Once again, try to dodge out of the way toward the monster's tail to avoid the damage area in front of it. The most important thing to remember while navigating its basic attacks is to keep an eye out for any scales that have dropped around the monster and clear the blast radius any time they become agitated. Try to set them off with slinger ammo from a distance to avoid blast damage and keep the area clear as often as possible.
The main weak points on Bazelgeuse are its head, wings and tail. The head and wings can be broken and the tail can be cut off. The monster is highly weak against the thunder element, and takes medium level damage from both ice and dragon elemental damage. The paralysis, sleep and poison ailments are all effective against this monster, so taking along traps and bombs that cause these effects will help give the hunter an extra advantage against Bazelgeuse.
This hunt is difficult to learn how to navigate at first, so learning to navigate and micromanage the explosive scales during battle is the key to success. Keep consistent DPS around the monster's head and tail to wear it down and you will be carving this monster for parts in no time.


Welcome to Humor Nation. Bruce Lee is without a doubt one of the most physically fit human beings to have ever walked on this planet and there are so many amazing facts about this legendary martial artist. It is said that Bruce Lee could catch a fly easily with his bare hands, people were skeptical of his skills, but he showed off the skill occasionally to shut down the doubters. Bruce Lee could throw a punch faster than a person blinking his eyes. You might see the footage of him demonstrating his punches and kicks at the 'ultra-instinct' speed.
Even the films of Bruce Lee had to be slowed down in order to see the martial artist movements. Bruce Lee would move amazingly fast which was difficult for the cameras to capture. The cameras used back in the day were way too slow when compared to the speed of Bruce Lee. The actor had to be slowed down twice for the cameras.
Sadly, Bruce Lee died young and the world lost a great martial artist. And the world thought that it could never ever see someone like the great Bruce Lee, his speed, his talents, his quickness was forever lost. But then a miracle happened.
Bruce Lee was a great man, a legend. But now arguably there's an even more athletic, fit, quicker legend in this world.
Kiran Lee's has earned a mythological status. He has broken down thousands of doors with his talent. For his amazing work, this man should be given an honorary Ph.D.'s in orthodontics, gynecology, and proctology. It's not hard to understand why Kiran is such the big star that he is today. Aside from his looks, speed, quickness, wittiness, the man has a sense of humor, he also happens to have a 'Nunchaku' with the strength and endurance of a cheetah.
You might be surprised after reading this, but his 'Nunchaku' has been insured for up to one million dollars. But this instrument is so damn precious that women go crazy after seeing it.
Kiran Lee is a strong believer in the fitness of the body and the mind. He trains daily for hours! His training regimen is so hard and long that only a few men can last alongside him. Kiran Lee uses his special fitness training in helping the women who need a good and refreshing workout. This man not only makes the women flexible after his sessions but also shows them what they are capable of. The purpose of his life is to make every woman fit and flexible through his workout sessions. He aims to not only give them the physical bodily pleasure, but also an emotional peace. He believes that once women are satisfied then they will contribute greatly to society through their roles.
Wherever he goes, the first thing he notices in a woman is her…it's the muscles! Take a look at how the master is star struck by the finely toned abs and a beautiful athletic body of this woman. Only a legend like him can appreciate the greatness. While the other guy is staring at the breasts of the woman, Kiran Lee is observing carefully and thinking in his mind about how much hard work, struggle, sweat it must have required for the woman to attain such muscles.
Even the fitness freak women are aware of the mastery skills of Kiran. They flood his inbox on Twitter, Instagram with messages and requests to get enrolled in his special workout programme. But he is very selective, he only chooses the elite, the few lucky and special women in his programme to teach them the secrets of ultimate fitness. Take a look at how the master is assuring the woman that she will find happiness in her life through the hard work which she'll be doing in his special gym.
Take a look in the picture, Master Kiran Lee taking the fitness class of a woman. He can sense the stiffness in her body, he can see the lack of movement in her to move like water. Kiran Lee will give her the water after a good workout.
The secret to Kiran's unbelievable fitness and long endurance has been a subject of interest even for the scientists and researchers. Many research studies have been conducted to find out the secret to his fitness. Even the doctors performed many medical exams on him to discover the physiology of this man.
They were surprised to find out that the secret to his quickness, agility, and inhumane fitness is his Nunchaku. Yes, you read it right! This man has a Nunchaku which is the source of his strength and long endurance. His Nunchaku is long, hard, and when it's stroked, swung at full motion, it generates energy which powers this man. His Nunchaku can generate up to 2500KW of energy which can power many houses. But this great man uses this energy to remove the stress in women.


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Saturday, Dec 25, 2021, 10:30
Gov't signs MoU on acquisition of stakes in Aegon, Union
Image by Mirko Kuzmanovic / Shutterstock.com
The government has signed a memorandum of understanding with Vienna Insurance Group (VIG) on acquiring stakes in insurers Aegon Biztosító and Union Biztosító, Finance Minister Mihaly Varga said, according to a report by state news wire MTI.
If negotiations close successfully, the state could acquire 45% stakes in the two insurers, Varga said.
In a press release issued late Wednesday, VIG said it had reached an agreement with the government of Hungary "on the principles of a cooperation and the further course of action, which provides for a participation of 45% by the Hungarian state" in the Hungarian Aegon companies and Union Biztosító.
"The structure of the cooperation, which entails the controlling stake of and the operational management by VIG, is subject to further negotiations," VIG said.
"As a next step, VIG and Hungary will negotiate the participation and governance structure, will obtain the necessary board resolutions, and will apply for the approvals that are necessary for the implementation of the transaction," VIG added.
VIG, which owns Union Biztosito, announced in November 2020 that it agreed to acquire the businesses of Dutch peer Aegon in Hungary, Poland, Romania and Turkey for a price of EUR 830 million, a deal that would have made VIG market leader in Hungary.
In April 2021, VIG said its acquisition of Aegon's business in Hungary was denied by the Interior Ministry.
Under state-of-emergency powers vested by parliament, Hungary's government has been equipped with legal tools to block foreign takeovers of domestic companies.
In October, the European Commission said it opened a probe into the Interior Ministry's veto of the transaction because of a possible violation of the European Union's merger regulation.
Gov't issues decree on staple foods price rollback
Politics Domestic | Jan 17, 2022, 10:50
Gov't calls HUF 30 bln tender to support microbusinesses
Hungary limits immunity certificate validity to the inoculat...

redpajama_set_name: RedPajamaCommonCrawl


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The Open Secrets of Penny Slinger
The pioneering 'feminist surrealist' who turned her back on the artworld returns with a London solo show
"The absurdity of minor objects telling a major story is something I seek out"
A date with Michael Rakowitz (and his mum)
Two exclusive recipes from the artist's new cookbook
The photographer talks about the virtues of repetition and structure, his Instagram account and his latest series – on view at Sprüth Magers, Los Angeles, through 30 August
By Fi Churchman
A New World Literature
Adam Thirlwell and Hans Ulrich Obrist discuss art in the age of isolationism – and the show they curated for Manchester International Festival
Art in Context Africa, Part V: Ibrahim El-Salahi
The Sudan-born artist discusses the role of art in the social and political life of his homeland, from the April 2015 issue
By Mark Rappolt
Part of an ongoing survey in which artists, curators and cultural commentators explore the question of what African art (of the contemporary flavour) does or can do within various local contexts across the continent.
Ibrahim El-Salahi was born in Omdurman, Sudan, in 1930. His studies in painting at the School of Design at Gordon Memorial College were followed by a scholarship to the Slade in London, after which he returned to teach at the College of Fine and Applied Arts in Khartoum, becoming a leading figure in the movement later known as the Khartoum School. During the 1960s he was closely associated with the multidisciplinary pan-African Mbari Artist and Writers Club based in Ibadan, Nigeria, of which fellow associates included the novelists Wole Soyinka and Chinua Achebe, and the artist Jacob Lawrence. While maintaining an interest in the graphic forms of Sudanese calligraphy, El-Salahi's work has evolved through a number of distinct phases over the course of his six-decade-long career. At the Slade he had studied European art history going back to the Renaissance, as well as the work of modern masters, but on his return to Sudan, El-Salahi spent a significant period engaging with the natural colours, symbolism and decorative traditions of his home country.
In 1975, while working at the Department of Culture, he was incarcerated for more than six months at Cooper Prison following false accusations of antigovernmental activities. Following his release he left Sudan, living in exile in Qatar and the UK. Between the late 1970s and mid-90s, influenced by his experiences in jail, El-Salahi focused on composite, multipanelled works in black and white, of which perhaps the best known became the monumental nine-panel ink painting The Inevitable (1984–5). Since 1998 he has lived and worked in Oxford, England. El-Salahi's works form part of notable institutional collections, including those of MoMa, New York; the Smithsonian Institution, Washington; Iwalewa- Haus, Bayreuth; National Gallery of Victoria, Sydney, and the Newcastle Art Gallery, Australia. In 2013 he was the subject of a major retrospective at Tate Modern, the first such dedicated to African Modernism.
ArtReview
Do you think there's a difference between making art under a democracy and making art under a dictatorship?
Ibrahim El-Salahi
Working in a democracy is a lasting experience; working under a dictatorship is an incentive for doing something – sometimes you can be afraid of the consequences, but sometimes you have to say you have a definite message. There is a large work that I did that is now at the Johnson Museum of Art in Ithaca called The Inevitable and that was a reaction to a political situation. I had to make a statement, particularly as I was working in a safer place outside the country.
AR Did you feel guilty about being in a safer place?
IES No, I wished to be there, because when I came out of jail, I never wanted to leave Sudan at all. I thought of staying until I saw that regime down and out for good, but I had been invited to go to Qatar to help establish the Department of Culture – the same thing that had brought me back to Sudan after working in London as an Assistant Cultural Attache. [at the Sudanese Embassy].
AR What kind of role did art play in society in Sudan then? Was it something that people engaged with, did it have an impact?
IES It took time, particularly as there was no interest from the state in culture. It would only give a sort of lip service, but there was no real interest at all. So the artist is really left alone and trying to create his own public by him or herself continuously. It's not like in a democracy where there are artistic institutions that help, and you get support from the authorities. That was not created. The difficulty we had when I was asked to set up the Department of Culture (later on subsumed into the Ministry of Culture and Information) in the country was immense. We had to ask for a budget at the end of the year, to cover what was needed to help cultural development in the country. I was only given £2. The main items required were a bicycle and a messenger, but the top man in the country at the time, General Nimeiry, said that because there was a shortage of funds and so on, any ministry should only have 10 percent of its budget. So the budget for the bicycle was supposed to be £20, and they gave us £2. The man in charge of the accounts said, "Culture can give, because now we can buy a bicycle pump!"
Some things never change, 2011. © the artist. Courtesy the artist
AR When you were setting up the Department of Culture in Sudan, did you have to put your own tastes and interests as an artist to one side?
IES I had to stop [making art], because I knew that the job would need work day and night: we had to travel throughout the country to get to the sources of cultural heritage and find out where it was still alive so that it could be built upon. It was a period that was very, very difficult for me and I had to stop work. The same thing happened when I was working at the embassy in London between 1969 and 72: then I also had to stop work, except for a very, very few things. I left no time for myself at all; it was a drab period.
AR Obviously you have a commitment to a kind of public service, is that something you see as the role of art as well? Does the art you make reach out to a public?
IES By necessity. I think it's wrong for the artist to be put in any situation, but he has to do something other than: 'What is three plus four?' But I think if the artist is in some sort of institution that is very well established, then the artist is free to be left on his own to do whatever… For an artist, it's much better to be left on your own to do your work and then see what happens.
AR When you were painting The Inevitable, what impact did you hope that would have? Is it designed to be an inspiration, to make people aware of something? Can art change the political or social structure?
I believe in the fact that the message from the artist to the public is to let them think and develop their own idea about the work
IES I hope so, because the message I always have is something to start people thinking. I'm not working to give a direct message, but I want the people to absorb it from the work itself. I believe in the fact that the message from the artist to the public is to let them think and develop their own idea about the work. The message that I put in The Inevitable was that someday, sooner or later, people will rise against tyranny, and that is up to them as a group, and they have to have what it takes, what is needed, to work together and to have force enough to make the changes necessary. The message is embodied in the work itself.
AR How much can you as an artist be involved in the actual rising up and the getting together?
IES I think you have limits. As a painter, as an artist, you have to go to a certain point and then leave it.
AR Do you think the role that art plays has changed in Sudan over the last 50 years?
IES I think so. In terms of numbers, in terms of movements, in terms of attitude, in terms of facilities. It's still very difficult, but relatively speaking there's quite a lot. Of course now we have artists who are starting their own galleries and then other elements, foreign elements – the French Cultural Centre, American Cultural Centre, the British Council – and they are improving facilities with art exhibitions. Gradually they're developing.
AR Do you think that those agencies have their own 'foreign' agendas?
IES True, because these are people with their own programmes and their own agendas who wish to expand their own nature and influence – using art for a creative link with their own countries. As far as the artist is concerned, it's a matter of necessity, they have no place to go to except those facilities, and they have to use them. I remember when there were very, very few art students: people preferred to go into other sorts of work – to do engineering, medicine, law and so on. Because people used to say that being an artist was a waste of time. Now large numbers attend the art college. So the awareness about the importance of art in society has been expanded, there are different subjects within it. That tells of the development that has taken place, which is important.
AR Why do you think that development has happened?
IES By sheer necessity and the fact that afterwards they found that art – for instance graphic art – has a marketplace: the calligraphers all studying at art college, they are finding a big market. The fact that it can pay back, that it can give you something to live on, is important.
AR How was it when you were studying?
IES Well, at that time there were very few [students]. The art college started in 1960, the School of Design in 1946. At the time when I joined the college I was in the third batch. Before there were two batches: the first lot was only two students; the second about six or seven. In our time, there were about 16. Now hundreds attend art college. Not only this, but one of our colleagues who was in the first batch to study art in the School of Design, he started his own college, which is far more thriving than the official college – totally different, it's changing.
AR What sort of things did they teach you?
IES In the School of Design, it used to be painting, drawing, clay modelling, bookbinding, calligraphy, that kind of thing. On the side, a little bit of architecture, but it wasn't a proper study. Now the college itself has expanded and besides painting has textile design, electronics and computer studies and interior design and so forth. It has expanded itself definitely.
AR How is it for you now that you're famous and people know your work? Is it harder to work when people have expectations of what your work should be?
IES It is harder, because of all this responsibility, which I try to keep away from as much as possible, but in other words, it becomes inevitable, because people think that I have made it. It's quite a responsibility, which puts you in a situation where you become very careful about what you say and what you do. And you get criticism, sometimes for or against. I find I'm a kind of a role model for something that I never asked for at all. I get people coming into the studio and writing papers and so on. I go to Sudan usually every year: I go when I have spare time, and I spend about a month or a month-anda- half there. When I come back from Sudan and I start my work, I always tell my wife that I need a holiday. Well after midnight I will have visits from people who are concerned. I appreciate their concern and their appreciation. In my hometown, Omdurman, they did a huge celebration in my honour. I told them, 'Please don't do this for me,' but they had a big celebration. They were happy and proud that one of them has made it outside and become well known and so forth. I think it's something that is appreciated very much indeed as far as the public are concerned in the country. Not the government: the government, until now, has no interest at all in culture or heritage except as far as it concerns tourism, not aesthetics.
AR What are you working on at the moment?
IES Right now, I'm just thinking. I keep changing continuously, because I don't want to be put inside a style or a method. The work also changes because my body is changing. Also I don't want to be caught by what I've done in the past. For instance with this so-called School of Khartoum, my relationship was only in the first three years, from 1959 to 62: only that period, then I changed continuously.
AR Do you think art historians like that? Maybe it's not your choice – it's not you who gets to decide which box you get put in.
IES Yes, I mean, the box is always there. For art historians and art analysts and people who try to categorise things, it's much easier, but when they tie you to a certainty [that no longer exists], then that's a problem. That's quite a misrepresentation of what you are as yourself, as a whole. You are only linked up as a small part of what you were before and what you left behind. That said of course, I do understand it personally as a whole, and my work, no matter how different it is, is still me, little old me.
AR Yes, and you recognise it? It never seems that an older work might have been made by another person?
IES It has happened to me sometimes, because I used to draw continuously and in a different style. Many times if it's put in a different light or a portion of it has been shown as a detail, I ask myself, 'Have I done that really, I don't remember?' If it's the whole thing, then it falls in place – then you know exactly that you've done that kind of thing and relate to the body: you're the same person and the work is only a part of you at that level.
AR What kind of artists inspired you in the early days?
IES I heard about crazy old Van Gogh – this excited me very much indeed – his sunflowers and his brushstrokes. I hadn't seen it, but I used to hear of it from a friend of mine. He used to study in Egyptian secondary school and they were lucky enough to have someone who was clued up about art and artists and he used to come tell us about it. We lapped it up, excited about the work of an artist who was supposed to be mad and cut off his ear and was in the fields and had those sunflowers. That to me was quite exciting.
Still many chains to shed, 2011. © the artist. Courtesy the artist
AR Yes, was that the idea you had of what it was to be an artist? Do you have to be slightly mad?
IES No, at that time, no, no not particularly. I knew that I was mad already. But I think of it in terms of adding something of a flavour of yourself and your ideas. The other person who I grew very interested in, somebody in the past – pure Renaissance – was Giotto, but mainly because he turned a new leaf from the Gothic art into the beginnings of the Renaissance and to using the third dimension, the raw vision. Others like Alberti, Brunelleschi, the architects who made the visual and theoretical perspective, I got very much interested in them. I went to a course in Italy at that time, way back in 1955, on the background of the Renaissance, which had been run by the British Institute in Florence. That gave me a chance to go tour around all of the school of Giotto. And I find artists like Grünewald quite interesting, because he's quite individual, he doesn't follow any school at all. The whole thing is a matter of give and take. Sometimes there are some people whose work you see and you like: it doesn't mean that you are copying them, but you draw a parallel, you try to bring something of your own. Somehow you relate it to what you have seen and that goes for everything that you see – whether it's an old artist or a contemporary artist that is interesting and excites our mind – and you do something in response. That's the kind of thing you could say I've been influenced by.
Lately, The Inevitable was shown in Barcelona at the Museum of Picasso. One of the presenters of the TV station asked me, 'Have you been to inspect Picasso?' She was quite shocked when I said, 'No, I haven't been inside.' She said, 'But how?' I said, 'Well, actually what you see here is something derived from our own culture,' it's the rhythm of calligraphy and African motifs. This is what excited me and why I did that work. It might look to your eye like something related to Picasso, but I assure you it's not, but it's up to you if you see it. If you see it as something influenced by Picasso, let it be, because I present the work and my job has been finished, when the work is finished you can interpret it the way you want, it's a free world.
AR A lot of your own work seems to grow organically…
IES Yes, I work on a new piece, and because I do not know what shape it is going to take, I add pieces. This is something that I learnt in jail. In jail, if someone was found with a pencil or paper, then something terrible would happen. So I used to have smaller sheets of paper and I used to draw small embryo forms. Then I added little bits and I used to bury it in the sand outside the cell, just for fear of solitary confinement for 15 days. Anyway, when I came out, I recalled the same idea of making, and each work [within a group that constituted a larger whole] was framed separately. If you see it as only a particle of a whole, it has the whole in it as well. That kind of thing took me time. After I left jail, it took me 17-and-a-half years – from late 1970s up to the mid-90s – following the same trend, of this idea of the particle and the whole in black and white.
It's quite different to the European way: having this sketch, then you add things and you take things out of it and so on until it takes a form which this sketch suggested in the beginning. With my work I do not know what form, what shape, what size the work is going to take, and that's why I start a new piece. Each piece [of the work] has to be framed separately, because it's an embryo of an idea that I'm not aware of completely. Then when it grows together it creates a whole. This gives to me a relationship between the particle and the whole, between the individual and society, which is upmost in my mind. Until it reaches the whole, which is the human being. So the same thing in the relationship from a religious point of view: you can get the created and the creator.
AR Did you study physics?
IES No, because I know my limits.
AR Ah, but you've been talking like someone who did.
IES No, I wish I had, but I didn't. There is a saying in Arabic: 'He who works with what he has learnt, God will reward him with knowing what he does not know.' If you are limiting yourself to what you know and use it to the maximum extent, then you will be rewarded with something else. That is my cup of physics for the future.
AR During the Arab Spring you created drawings in a notebook. Was that about hope or frustration?
IES That was because I felt held back by the flu, a terrible flu and couldn't go to the studio, so I worked at home on this small notebook. I wished I was there to celebrate and to give a hand. The only way I could give a hand was just to make drawings and little things, because I couldn't get out. It was to celebrate the fact that this kind of idol, this kind of tyrant had fallen down, but I was afraid that other people might come and replace them and do the same if not worse.
AR The drawings that you made in the prison, were you able to take them out or did they just stay in the sand?
IES No, I left them in the sand, because when they called your name that means one of four things: either they're going to send you to another cell within the jail, or they're going to send you to another jail somewhere else in the country, or they're going to set you free or they're going to chop your head off. When they called my name, I just got my things and stood there until they took us to the security and left me and said, 'Go.'
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Features include: Koki Tanaka, Gregor Schneider, Renzo Martens, Renata Lucas, Africa - Art in Context V: Ibrahim El-Salahi
Art in Context Africa, Part IV: Osei Bonsu
on The Bare Necessities: Raw Material Company in Dakar
Art in Context Africa, Part III: Cristina De Middel
Artist project: This is what hatred did, 2014
Art in Context Africa, Part I: Sabelo Mlangeni's No Problem, and a visit to the site of Michelle Monareng's Removal to Radium
Art in Context Africa, Part II: Bonaventure Soh Bejeng Ndikung on Theo Eshetu
The London-born Ethiopian artist will be opening a solo show at Tiwani Contemporary in London this week; read our feature on notions of Past and Future Perfect in his work, from the October 2014 issue
Mark Rappolt
The Niesłuchowski Experiment
Tyler Coburn on how Simon Leung made Warren Niesłuchowski's lifestyle a work of art – from the archive
By Tyler Coburn
Cao Fei (and me)
Doretta Lau navigates the worlds of the Beijing-based artist, who's presenting a whole new body of work at the Centre Pompidou next week – from the archive
By Doretta Lau
The Companionable Franz West
How the late Austrian artist's convivial, shitpositive vision of sculpture reinvented public art
By Rosanna Mclaughlin
Isuma in Venice
At the Canadian Pavilion, the Inuit artist collective disputes the ideas of nationhood and representation on which the Venice Biennale was founded
Looking at Pictures with William Eggleston
An interview with the pioneering American photographer, whose work is on view at David Zwirner, London
Michael Lin & Richard Lin
Mark Rappolt on the subtleties of inter-generational artistic dialogue
Andrea Fraser on art, power and patronage after Donald Trump
Our Full Attention
Does conflict photography belong in a gallery?


A successful deployment of SD Elements begins with defining key roles of ownership for different aspects of the system. These roles are global in nature, meaning they are about overall usage of SD Elements rather than within a specific project. Defining owners ensures accountability. Since usage of SD Elements affects processes, owners are critical to driving adoption, customization, and operations.
While one person may play many or all of these roles in a smaller organization, several people are usually involved in a larger organization. In all cases, somebody needs to be appointed for each role. Lacking owners will lead to underuse of SD Elements and may in fact have a substantial impact on adoption.
The champion is responsible for spearheading adoption of SD Elements, from a technical standpoint. This is the most critical role in a deployment.
The content owner is responsible for customizing SD Elements content to include organization-specific policies, procedures, requirements, and language. In smaller organizations that are relatively new to application security, there may not be a need for a separate content owner.
The system administrator is responsible for the SD Elements virtual appliance. This role is only applicable to customers with an On-Site Deployment (OSD) virtual appliance.
The user administrator is responsible for user management and/or Single Sign On integration.
The project manager is responsible for overseeing large deployments of SD Elements.


text:
Dec. 12, 2004 / 3:30 AM
Today is Sunday, Dec. 12, the 347th day of 2004 with 19 to follow.
The moon is new. The morning stars are Mercury, Pluto, Jupiter, Saturn, Venus and Mars. The evening stars are Uranus and Neptune.
Those born on this date are under the sign of Sagittarius. They include John Jay, first chief justice of the U.S. Supreme Court, in 1745; abolitionist William Lloyd Garrison in 1805; French novelist Gustave Flaubert in 1821; Norwegian painter Edvard Munch in 1863; actor Edward G. Robinson in 1893; singer/actor Frank Sinatra in 1915; TV game show host Bob Barker in 1923 (age 81); former New York Mayor Edward Koch in 1924 (age 80); singers Connie Francis in 1938 (age 66) and Dionne Warwick in 1941 (age 63); talk show host Rush Limbaugh in 1951 (age 53); former Olympic gymnast Cathy Rigby in 1952 (age 52); musician Sheila E in 1959 (age 45); former tennis player Tracy Austin in 1962 (age 42); and actress Mayim Bialik in 1975 (age 29).
On this date in history:
In 1870, Joseph Hayne Rainey of South Carolina was sworn in as the first black to serve in the U.S. House.
In 1901, Italian physicist and radio pioneer Guglielmo Marconi sent the first radio transmission across the Atlantic Ocean.
In 1913, two years after it was stolen from the Louvre Museum in Paris, Leonardo da Vinci's masterpiece "The Mona Lisa" was recovered in a Florence, Italy, hotel room.
In 1917, Father Edward J. Flanagan, a 31-year-old Irish priest, opened the doors to Boys Town, a home for troubled and neglected children in Omaha, Neb. He lived by the adage, "There is no such thing as a bad boy."
In 1937, Japanese planes bombed and sank the U.S. gunboat Panay in the Yangtze River north of Nanking, China. Japan later said it was a mistake.
In 1968, stage and screen actress Tallulah Bankhead died at the age of 65.
In 1975, Sara Jane Moore said she willfully tried to kill President Ford. She is serving a life prison sentence.
In 1981, martial law was imposed in Poland.
In 1985, the crash of an Arrow Air DC-8 military charter on takeoff from Gander, Newfoundland, killed all 256 aboard, including 248 U.S. soldiers.
In 1989, five Central American presidents, including Nicaragua's Daniel Ortega, called for an end to the rebel offensive against El Salvador's U.S.-backed government.
In 1990, 15 people were killed and more than 260 injured in a pileup on a foggy Tennessee highway.
In 1991, the Russian parliament ratified a commonwealth treaty linking the three strongest Soviet republics in the nation's most profound change since the 1917 revolution.
Also in 1991, North and South Korea concluded an historic agreement to reunify peacefully after 46 years of division and animosity.
In 1992, Princess Anne, the only daughter of Queen Elizabeth II of Britain, became the first divorced royal in the inner circle to remarry when she wed Cmdr. Timothy Laurence.
In 1993, Russian voters approved a new Constitution.
In 1996, a French gunman took 35 hostages in a Paris office. The standoff ended without injuries.
In 1998, President Clinton began a trip to the Middle East that included a visit to the new Gaza International Airport in Palestinian territory.
In 2002, North Korea announced it would reactivate a nuclear reactor idle since 1994.
Also in 2002, the European Union invited 10 nations, including Poland and Hungary, to join its ranks in 2004.
In 2003, Paul Martin became Canada's 21st prime minister, succeeding Jean Chretien.
Also in 2003, armed men attacked military police near the Ivory Coast's national television station in Abijdan, leaving at least 19 people dead.
A thought for the day: Leon Blum wrote, "I have often thought morality may perhaps consist solely in the courage of making a choice."
Cathy Rigby
Edward J. Flanagan
Edward Koch
Leon Blum
Mayim Bialik
Timothy Laurence
Tracy Austin
William Lloyd Garrison


text:
Trump complains he didn't get a 'thank you' for McCain's funeral
By Maegan Vazquez, CNN
Updated 6:59 PM EDT, Wed March 20, 2019
Trump doubles down on attacks against late Sen. McCain
President Donald Trump complained Wednesday that he didn't receive a thank you for approving the funeral the late Sen. John McCain wanted, marking his latest grievance in his recent onslaught against the Arizona Republican.
"I endorsed him at his request, and I gave him the kind of funeral that he wanted, which as President I had to approve. I don't care about this. I didn't get thank you. That's OK. We sent him on the way. But I wasn't a fan of John McCain," Trump said during a speech Wednesday at a tank factory in Lima, Ohio.
Last year, McCain died of brain cancer, and as part of his services, lay in state in the Capitol building in Washington.
CNN previously reported that the senator, who had been held as a prisoner of war in Vietnam, did not want the President at his funeral. McCain's daughter, Meghan McCain, also revealed earlier this year that she wished Ivanka Trump and Jared Kushner, Trump's daughter and son-in-law and senior advisers, had not attended the funeral.
Fact-checking Trump's claim that McCain misled the White House on his Obamacare repeal vote
Trump's remark about the funeral came as the President has continued to denigrate the dead senator's legacy.
Last weekend, Trump attacked McCain in several tweets that targeted his ties to the controversial Russia dossier and his vote against repealing Obamacare. He also referred to McCain as being "last in his class" at the US Naval Academy.
On Tuesday, he continued his criticism, telling reporters at the White House that "I was never a fan of John McCain and I never will be."
The late senator's widow, Cindy McCain, publicized hateful messages she's been receiving since Trump's tweets, and daughter Meghan McCain has continued to respond to the President online and on ABC's "The View," where she's a co-host.
All the while, a growing number Republican members of Congress have been publicly pushing back on Trump's comments, defending McCain.
In front of factory workers at the Ohio plant on Wednesday, Trump dedicated a considerable amount of time in his speech to disparaging McCain.
"I have to be honest," Trump said, "I never liked him much. Hasn't been for me."
He said he probably "never will" like McCain, because "John McCain received a fake and phony dossier."
He also dug into McCain's now-famous vote against a repeal of the Affordable Care Act.
"When he finally had the chance to do it, he voted against repeal and replace," the President said. "Remember thumbs down?"
On Tuesday, Trump falsely accused McCain of misleading the White House over how he would vote.
Trump added Wednesday that veterans were on his side during the dispute, because McCain "didn't get the job done" with the Veterans Administration.
He also blamed McCain for wars in the Middle East.
"He was calling (President George W.) Bush, President Bush all the time, 'Get into the Middle East! Get in to the Middle East,' " Trump claimed, adding we've lost "tremendous health and tremendous lives in that war."
CNN's Nikki Carvajal and Devan Cole contributed to this report.