scholarly journals First continuous measurements of δ<sup>18</sup>O-CO<sub>2</sub> in air with a Fourier transform infrared spectrometer

2015 ◽  
Vol 8 (2) ◽  
pp. 579-592 ◽  
Author(s):  
S. N. Vardag ◽  
S. Hammer ◽  
M. Sabasch ◽  
D. W. T. Griffith ◽  
I. Levin
Keyword(s):  
Fourier Transform ◽  
Temporal Resolution ◽  
Isotope Ratio ◽  
Regional Scale ◽  
Fourier Transform Infrared ◽  
Ambient Air ◽  
Measurement Precision ◽  
High Temporal Resolution ◽  
Significance Level ◽  
Gas Measurements

Abstract. The continuous in situ measurement of δ18O in atmospheric CO2 opens a new door to differentiating between CO2 source and sink components with high temporal resolution. Continuous 13C–CO2 measurement systems have already been commercially available for some time, but until now, only few instruments have been able to provide a continuous measurement of the oxygen isotope ratio in CO2. Besides precise 13C/12C observations, the Fourier transform infrared (FTIR) spectrometer is also able to measure the 18O / 16O ratio in CO2, but the precision and accuracy of the measurements have not yet been evaluated. Here we present a first analysis of δ18O-CO2 (and δ13C-CO2) measurements with the FTIR analyser in Heidelberg. We used Allan deviation to determine the repeatability of δ18O-CO2 measurements and found that it decreases from 0.25‰ for 10 min averages to about 0.1‰ after 2 h and remains at that value up to 24 h. We evaluated the measurement precision over a 10-month period (intermediate measurement precision) using daily working gas measurements and found that our spectrometer measured δ18O-CO2 to better than 0.3‰ at a temporal resolution of less than 10 min. The compatibility of our FTIR-spectrometric measurements to isotope-ratio mass-spectrometric (IRMS) measurements was determined by comparing FTIR measurements of cylinder gases and ambient air with IRMS measurements of flask samples, filled with gases of the same cylinders or collected from the same ambient air intake. Two-sample t tests revealed that, at the 0.01 significance level, the FTIR and the IRMS measurements do not differ significantly from each other and are thus compatible. We describe two weekly episodes of ambient air measurements, one in winter and one in summer, and discuss what potential insights and new challenges combined highly resolved CO2, δ13C-CO2 and δ18O-CO2 records may provide in terms of better understanding regional scale continental carbon exchange processes.

scholarly journals First measurements of continuous δ<sup>18</sup>O-CO<sub>2</sub> with a Fourier Transform InfraRed spectrometer in Heidelberg, Germany

2014 ◽  
Vol 7 (7) ◽  
pp. 6501-6528
Author(s):  
S. N. Vardag ◽  
S. Hammer ◽  
M. Sabasch ◽  
D. W. T. Griffith ◽  
I. Levin
Keyword(s):  
Fourier Transform ◽  
Temporal Resolution ◽  
Regional Scale ◽  
Fourier Transform Infrared ◽  
Ambient Air ◽  
High Temporal Resolution ◽  
Exchange Processes ◽  
Infrared Spectrometer ◽  
Gas Measurements ◽  
The Fourier Transform

Abstract. The continuous in-situ measurement of δ18O in atmospheric CO2 opens a new door to differentiating between CO2 source and sink components with high temporal resolution. Continuous 13C-CO2 measurement systems have been commercially available already for some time, but until now, only few instruments have been able to provide a continuous measurement of the oxygen isotope ratio in CO2. Besides precise 13C/12C observations, the Fourier Transform InfraRed (FTIR) spectrometer also measures the 18O/16O ratio of CO2, but the precision and accuracy of the measurements has not been evaluated yet. Here we present a first analysis of δ18O-CO2 (and δ13C-CO2) measurements with the FTIR in Heidelberg. We find that our spectrometer measures 18O in CO2 with a reproducibility of better than 0.3‰ at a temporal resolution of less than 10 min, as determined from surveillance gas measurements over a period of ten months. An Allan deviation test shows that the δ18O repeatability reaches 0.15‰ for half-hourly means. The compatibility of our spectroscopic measurements was determined by comparing FTIR measurements of calibration gases and ambient air to mass-spectrometric measurements of flask samples, filled with the cylinder gases or episodically collected over a diurnal cycle (event). We found that direct cylinder gas measurements agree to 0.01 ± 0.04‰ (mean and standard deviation) for δ13C-CO2 and 0.01 ± 0.11‰ for δ18O. Two weekly episodes of recent ambient air measurements, one in winter and one in summer, are discussed in view of the question, which potential insights and new challenges combined highly resolved δ18O-CO2 and δ13C-CO2 records may provide in terms of better understanding regional scale continental carbon exchange processes.

scholarly journals In situ observations of the isotopic composition of methane at the Cabauw tall tower site

2016 ◽  
Vol 16 (16) ◽  
pp. 10469-10487 ◽  
Author(s):  
Thomas Röckmann ◽  
Simon Eyer ◽  
Carina van der Veen ◽  
Maria E. Popa ◽  
Béla Tuzson ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
High Precision ◽  
Temporal Resolution ◽  
Isotope Ratio ◽  
Mesoscale Model ◽  
Ambient Air ◽  
High Temporal Resolution ◽  
Model Calculations ◽  
Dual Isotope

Abstract. High-precision analyses of the isotopic composition of methane in ambient air can potentially be used to discriminate between different source categories. Due to the complexity of isotope ratio measurements, such analyses have generally been performed in the laboratory on air samples collected in the field. This poses a limitation on the temporal resolution at which the isotopic composition can be monitored with reasonable logistical effort. Here we present the performance of a dual isotope ratio mass spectrometric system (IRMS) and a quantum cascade laser absorption spectroscopy (QCLAS)-based technique for in situ analysis of the isotopic composition of methane under field conditions. Both systems were deployed at the Cabauw Experimental Site for Atmospheric Research (CESAR) in the Netherlands and performed in situ, high-frequency (approx. hourly) measurements for a period of more than 5 months. The IRMS and QCLAS instruments were in excellent agreement with a slight systematic offset of (+0.25 ± 0.04) ‰ for δ13C and (−4.3 ± 0.4) ‰ for δD. This was corrected for, yielding a combined dataset with more than 2500 measurements of both δ13C and δD. The high-precision and high-temporal-resolution dataset not only reveals the overwhelming contribution of isotopically depleted agricultural CH4 emissions from ruminants at the Cabauw site but also allows the identification of specific events with elevated contributions from more enriched sources such as natural gas and landfills. The final dataset was compared to model calculations using the global model TM5 and the mesoscale model FLEXPART-COSMO. The results of both models agree better with the measurements when the TNO-MACC emission inventory is used in the models than when the EDGAR inventory is used. This suggests that high-resolution isotope measurements have the potential to further constrain the methane budget when they are performed at multiple sites that are representative for the entire European domain.

scholarly journals In-situ observations of the isotopic composition of methane at the Cabauw tall tower site

2016 ◽  
Author(s):  
Thomas Röckmann ◽  
Simon Eyer ◽  
Carina van der Veen ◽  
Maria E. Popa ◽  
Béla Tuzson ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
High Precision ◽  
Temporal Resolution ◽  
Isotope Ratio ◽  
Mesoscale Model ◽  
Ambient Air ◽  
Model Calculations ◽  
Dual Isotope ◽  
Methane Budget

Abstract. High precision analyses of the isotopic composition of methane in ambient air can potentially be used to discriminate between different source categories. Due to the complexity of isotope ratio measurements, such analyses have generally been performed in the laboratory on air samples collected in the field. This poses a limitation on the temporal resolution at which the isotopic composition can be monitored with reasonable logistical effort. Here we present the performance of a dual isotope ratio mass spectrometric system (IRMS) and a quantum cascade laser absorption spectroscopy (QCLAS) based technique for in-situ analysis of the isotopic composition of methane under field conditions. Both systems were deployed at the Cabauw experimental site for atmospheric research (CESAR) in the Netherlands and performed in-situ, high-frequency (approx. hourly) measurements for a period of more than 5 months. The IRMS and QCLAS instruments were in excellent agreement with a slight systematic offset of +(0.05 ± 0.03) ‰ for δ13C and –(3.6 ± 0.4) ‰ for δD. This was corrected for, yielding a combined dataset with more than 2500 measurements of both δ13C and δD. The high precision and temporal resolution dataset does not only reveal the overwhelming contribution of isotopically depleted agricultural CH4 emissions from ruminants at the Cabauw site, but also allows the identification of specific events with elevated contributions from more enriched sources such as natural gas and landfills. The final dataset was compared to model calculations using the global model TM5 and the mesoscale model FLEXPART-COSMO. The results of both models agree better with the measurements when the TNO-MACC emission inventory is used in the models than when the EDGAR inventory is used. This suggests that high-resolution isotope measurements have the potential to further constrain the methane budget, when they are performed at multiple sites that are representative for the entire European domain.

THE USE OF A TRANSPORTABLE FOURIER TRANSFORM INFRARED (FTIR) SPECTROMETER FOR THE DIRECT MEASUREMENT OF SOLVENTS IN BREATH AND AMBIENT AIR—I: METHANOL

AIHAJ ◽  
1992 ◽  
Vol 53 (4) ◽  
pp. 221-227 ◽  
Author(s):  
Alfred Franzblau ◽  
Steven P. Levine ◽  
Lou Ann Burgess ◽  
Qing-shan Qu ◽  
Richard M. Schreck ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Direct Measurement ◽  
Fourier Transform Infrared ◽  
Ambient Air ◽  
Ftir Spectrometer

scholarly journals QUAL-NET, a high temporal resolution eutrophication model in large hydrographic networks

2017 ◽  
Author(s):  
Camille Minaudo ◽  
Florence Curie ◽  
Yann Jullian ◽  
Nathalie Gassama ◽  
Florentina Moatar
Keyword(s):  
Temporal Resolution ◽  
Regional Scale ◽  
River System ◽  
High Temporal Resolution ◽  
Model Quality ◽  
Deterministic Models ◽  
Time Model ◽  
Complex Interactions ◽  
Drainage Networks ◽  
Loire River

Abstract. To allow climate change impact assessment on river system water quality, the scientific community lacks efficient deterministic models able to simulate hydrological and biogeochemical processes in drainage networks at the regional scale, with a fine temporal resolution and with water temperature explicitly determined. The model QUALity-NETwork (QUAL-NET) was developed and tested on the Middle Loire River Corridor, a sub-catchment of the Loire River (France), prone to eutrophication. Hourly variations computed by the model helped disentangle the complex interactions existing between hydrological and biological processes across different timescales. Phytoplankton variations in the Loire River were governed by phosphorus availability and transit time. Model QUAL-NET showed that a large amount of phytoplankton cells growing in the upper part of the studied corridor was recycled through the microbial loop, which enhanced phytoplankton growth, explaining why severe blooms still occur in the Loire River despite large P input reductions.

scholarly journals Technical note: Coupling infrared gas analysis and cavity ring down spectroscopy for autonomous, high-temporal-resolution measurements of DIC and <i>δ</i><sup>13</sup>C–DIC

2017 ◽  
Vol 14 (5) ◽  
pp. 1305-1313 ◽  
Author(s):  
Mitchell Call ◽  
Kai G. Schulz ◽  
Matheus C. Carvalho ◽  
Isaac R. Santos ◽  
Damien T. Maher
Keyword(s):  
Temporal Resolution ◽  
Isotope Ratio ◽  
Inorganic Carbon ◽  
Dissolved Inorganic Carbon ◽  
Stable Isotope Ratio ◽  
Small Sample ◽  
High Temporal Resolution ◽  
Precision Data ◽  
Simple Method ◽  
Cavity Ring Down

Abstract. A new approach to autonomously determine concentrations of dissolved inorganic carbon (DIC) and its carbon stable isotope ratio (δ13C–DIC) at high temporal resolution is presented. The simple method requires no customised design. Instead it uses two commercially available instruments currently used in aquatic carbon research. An inorganic carbon analyser utilising non-dispersive infrared detection (NDIR) is coupled to a Cavity Ring-down Spectrometer (CRDS) to determine DIC and δ13C–DIC based on the liberated CO2 from acidified aliquots of water. Using a small sample volume of 2 mL, the precision and accuracy of the new method was comparable to standard isotope ratio mass spectrometry (IRMS) methods. The system achieved a sampling resolution of 16 min, with a DIC precision of ±1.5 to 2 µmol kg−1 and δ13C–DIC precision of ±0.14 ‰ for concentrations spanning 1000 to 3600 µmol kg−1. Accuracy of 0.1 ± 0.06 ‰ for δ13C–DIC based on DIC concentrations ranging from 2000 to 2230 µmol kg−1 was achieved during a laboratory-based algal bloom experiment. The high precision data that can be autonomously obtained by the system should enable complex carbonate system questions to be explored in aquatic sciences using high-temporal-resolution observations.

scholarly journals Toward real-time measurement of atmospheric mercury concentrations using cavity ring-down spectroscopy

2010 ◽  
Vol 10 (6) ◽  
pp. 2879-2892 ◽  
Author(s):  
X. Faïn ◽  
H. Moosmüller ◽  
D. Obrist
Keyword(s):  
Temporal Resolution ◽  
Time Resolution ◽  
Pulse Repetition Frequency ◽  
Ambient Air ◽  
Atmospheric Mercury ◽  
Dye Laser ◽  
High Temporal Resolution ◽  
Cavity Ring Down Spectroscopy ◽  
Absorption Measurements ◽  
Cavity Ring Down

Abstract. Cavity ring-down spectroscopy (CRDS) is a direct absorption technique that utilizes path lengths up to multiple kilometers in a compact absorption cell and has a significantly higher sensitivity than conventional absorption spectroscopy. This tool opens new prospects for study of gaseous elemental mercury (Hg0) because of its high temporal resolution and reduced sample volume requirements (<0.5 l of sample air). We developed a new sensor based on CRDS for measurement of (Hg0) mass concentration. Sensor characteristics include sub-ng m−3 detection limit and high temporal resolution using a frequency-doubled, tuneable dye laser emitting pulses at ~253.65 nm with a pulse repetition frequency of 50 Hz. The dye laser incorporates a unique piezo element attached to its tuning grating allowing it to tune the laser on and off the Hg0 absorption line on a pulse-to-pulse basis to facilitate differential absorption measurements. Hg0 absorption measurements with this CRDS laboratory prototype are highly linearly related to Hg0 concentrations determined by a Tekran 2537B analyzer over an Hg0 concentration range from 0.2 ng m−3 to 573 ng m−3, implying excellent linearity of both instruments. The current CRDS instrument has a sensitivity of 0.10 ng Hg0 m−3 at 10-s time resolution. Ambient-air tests showed that background Hg0 levels can be detected at low temporal resolution (i.e., 1 s), but also highlight a need for high-frequency (i.e., pulse-to-pulse) differential on/off-line tuning of the laser wavelength to account for instabilities of the CRDS system and variable background absorption interferences. Future applications may include ambient Hg0 flux measurements with eddy covariance techniques, which require measurements of Hg0 concentrations with sub-ng m−3 sensitivity and sub-second time resolution.

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