Abstract

Carbon isotope ratio analysis using a laser-based technique has been performed in the field, on the gaseous emissions from an active volcano. We here describe that 13CO2/12CO2 determinations can be carried out in a quasi-continuous regime using a compact, selective and sensitive diode laser spectrometer at a wavelength of 2 µm. Within the Solfatara crater (near Naples, Italy), in a very harsh environment, we were able to determine relative 13CO2/12CO2 values, on the highest flux fumarole, with an accuracy of 0.5 ‰. Regular and frequent observations of the carbon isotopes in volcanic gases, which become possible with our methodology, are of the utmost importance for geochemical surveillance of volcanoes.

© 2004 Optical Society of America

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References

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  1. C. Panichi, G. La Ruffa, �??Stable isotope geochemistry of fumaroles: an insight into volcanic surveillance,�?? J. Geodyn. 32, 519-542 (2001).
    [CrossRef]
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    [CrossRef]
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    [CrossRef] [PubMed]
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    [CrossRef] [PubMed]
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    [CrossRef]
  7. E. R. Crosson et al., �??Stable isotope ratios using cavity ring-down spectroscopy: determination of 13C/12C for carbon dioxide in human breath,�?? Anal. Chem. 74, 2003-2007, (2002).
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    [CrossRef]
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    [CrossRef]
  12. Isotope ratios are, usually, expressed in δ-units. In the case of 13C/12C isotope ratio in carbon dioxide, the δ- value is given by: where R13 represent the abundance ratio [13C]/[12C]. Usually expressed in per mill (�?�), it is referred to the PDB-standard material (Belemnite of the Pee Dee formation in South Caroline, [13C]/[12C]=11237.2 10-6).
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    [CrossRef]
  14. S. P. Love, F. Goff, D. Counce, C. Siebe, and H. Delgado, �??Passive infrared spectroscopy of the eruption plume at Popocatépetl volcano, Mexico,�?? Nature 396, 563-567 (1998).
    [CrossRef]
  15. L. Gianfrani, G. De Natale, P. De Natale, �??Remote sensing of volcanic gases with a DFB-laser-based fiber spectrometer,�?? Appl. Phys. B: Lasers and Optics 70, 467-470 (2000).
  16. A. Rocco, G. De Natale, P. De Natale, G. Gagliardi, L. Gianfrani, �??A diode-laser-based spectrometer for insitu measurements of volcanic gases,�?? Appl. Phys. B: Lasers and Optics 78, 235-240 (2004).
    [CrossRef]
  17. C. Panichi, G. Volpi, �?? Hydrogen, oxygen and carbon isotope ratios of Solfatara fumaroles (Phlegrean Fields, Italy): further insight into source processes,�?? J. Volcanol. Geotherm. Res. 99, 321-328 (1999).
    [CrossRef]
  18. D. Tedesco, P. Scarsi, �??Intensive gas sampling of noble gases and carbon at Vulcano Island (southern Italy),�?? J. Geophys. Res. 104, 10499-10510 (1999).
    [CrossRef]
  19. D. Weidmann, G. Wysocki, C. Oppenheimer, F. K. Tittel, �??Development of a compact quantum cascade laser spectrometer for field measurements of CO2 isotopes,�?? Appl. Phys. B: Lasers and Optics, DOI: 10.1007/s00340-004-1639-7 (2004).

Anal. Chem.

E. R. Th. Kerstel, R. van Trigt, N. Dam, J. Reuss, H. A. J. Meijer, �??Simultaneous determination of the 2H/1H, 17O/16O, and 18O/16O isotope abundance ratios in water by means of laser spectrometry,�?? Anal. Chem. 71, 5297-5303 (1999).
[CrossRef] [PubMed]

E. R. Crosson et al., �??Stable isotope ratios using cavity ring-down spectroscopy: determination of 13C/12C for carbon dioxide in human breath,�?? Anal. Chem. 74, 2003-2007, (2002).
[CrossRef] [PubMed]

R. van Trigt, E. R. Th. Kerstel, G. H. Visser, H. A. J. Meijer, �??Stable isotope ratio measurements on highly enriched water samples by means of laser spectrometry,�?? Anal. Chem. 73, 2445-2452 (2001).
[CrossRef] [PubMed]

Appl. Opt.

Appl. Phys. B: Lasers and Optics

L. Gianfrani, G. De Natale, P. De Natale, �??Remote sensing of volcanic gases with a DFB-laser-based fiber spectrometer,�?? Appl. Phys. B: Lasers and Optics 70, 467-470 (2000).

A. Rocco, G. De Natale, P. De Natale, G. Gagliardi, L. Gianfrani, �??A diode-laser-based spectrometer for insitu measurements of volcanic gases,�?? Appl. Phys. B: Lasers and Optics 78, 235-240 (2004).
[CrossRef]

G. Gagliardi, A. Castrillo, R. Q. Iannone, E. R. Th. Kerstel, L. Gianfrani, �??High-precision determination of the 13CO2/12CO2 isotope ratio using a portable 2.008-μm diode-laser spectrometer,�?? Appl. Phys. B: Lasers and Optics 77, 119-124 (2003).
[CrossRef]

M. Erdelyi, D. Richter, F. K. Tittel, �??13CO2/12CO2 isotopic ratio measurements using a difference frequencybased sensor operating at 4.35 μm,�?? Appl. Phys. B: Lasers and Optics 75, 289-295 (2002).
[CrossRef]

D. Weidmann, G. Wysocki, C. Oppenheimer, F. K. Tittel, �??Development of a compact quantum cascade laser spectrometer for field measurements of CO2 isotopes,�?? Appl. Phys. B: Lasers and Optics, DOI: 10.1007/s00340-004-1639-7 (2004).

Earth Planet. Sci. Lett.

D. Tedesco, P. Scarsi, �??Chemical (He, H2, CH4, Ne, Ar, N2) and isotopic (He, Ne, Ar, C) variations at Solfatara crater (southern Italy): mixing of different sources in relation to seismic activity,�?? Earth Planet. Sci. Lett. 171, 465-480 (1999).
[CrossRef]

J. Geodyn.

C. Panichi, G. La Ruffa, �??Stable isotope geochemistry of fumaroles: an insight into volcanic surveillance,�?? J. Geodyn. 32, 519-542 (2001).
[CrossRef]

J. Geophys. Res.

D. Tedesco, P. Scarsi, �??Intensive gas sampling of noble gases and carbon at Vulcano Island (southern Italy),�?? J. Geophys. Res. 104, 10499-10510 (1999).
[CrossRef]

J. Volcanol. Geotherm. Res.

C. Panichi, G. Volpi, �?? Hydrogen, oxygen and carbon isotope ratios of Solfatara fumaroles (Phlegrean Fields, Italy): further insight into source processes,�?? J. Volcanol. Geotherm. Res. 99, 321-328 (1999).
[CrossRef]

P. Allard, A. Maiorani, D. Tedesco, G. Cortecci, B. Turi, �??Isotopic study of the origin of sulfur and carbon in Solfatara fumaroles, Campi Flegrei caldera,�?? J. Volcanol. Geotherm. Res. 48, 139-159 (1991).
[CrossRef]

Nature

P. Francis, M. Burton, C. Oppenheimer, �??Remote measurements of volcanic gas composition by solar occultation spectroscopy,�?? Nature 396, 567-570 (1998).
[CrossRef]

S. P. Love, F. Goff, D. Counce, C. Siebe, and H. Delgado, �??Passive infrared spectroscopy of the eruption plume at Popocatépetl volcano, Mexico,�?? Nature 396, 563-567 (1998).
[CrossRef]

Opt. Express

Science

D. E. Murnick, B. J. Peer, �??Laser-based analysis of carbon isotope ratios,�?? Science 263, 945 (1994).
[CrossRef] [PubMed]

Other

Isotope ratios are, usually, expressed in δ-units. In the case of 13C/12C isotope ratio in carbon dioxide, the δ- value is given by: where R13 represent the abundance ratio [13C]/[12C]. Usually expressed in per mill (�?�), it is referred to the PDB-standard material (Belemnite of the Pee Dee formation in South Caroline, [13C]/[12C]=11237.2 10-6).

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Figures (5)

Fig. 1.
Fig. 1.

Sketch of the experimental setup. DL stands for diode laser, BS1 for a 50% beam splitter, BS2 for a 10% beam splitter, L for lens (L1 and L2 having 1-m and 5-cm focal lengths, respectively), PG for pressure gauge, V for pneumatically powered valve, S for electronic shutter, Ph for photodiode, RC and SC for reference and sample cell, respectively. Ph2 is used to monitor variations of the laser power.

Fig. 2.
Fig. 2.

Example of absorption spectra, recorded at Solfatara Volcano on September 15 and associated to the sampled volcanic gas (black line) as well as to the reference material (red line). The spectra are initially stored in the buffer of the digital lock-in amplifier as data vectors with 1000-record length, and subsequently transferred to a laptop computer through a GPIB-USB port, with an overall vertical resolution of 16 bit. The acquisition program, implemented in LABVIEW®, enables continuous operation in a fully automated way for several hours. The absorption features correspond to the 13CO2 P(16) line, of the ν1+2ν203 vibrational band, and to the 12CO2 R(17) line, belonging to the 2ν1+ν21-ν213 band.

Fig. 3.
Fig. 3.

Examples of repeated field measurements on volcanic CO2 gases, sampled by means of the flask-based method, in panel (a), and the direct collection system, in panel (b). Each point is the result of a non-linear least squares analysis of a pair of sample and reference spectra, resulting from a signal averaging procedure over 50 laser scans for (a) and 30 scans for (b). The overall acquisition time was about 83 and 50 minutes, respectively for the measurements’ set in (a) and (b).

Fig. 4.
Fig. 4.

Example of calibration check, performed during the field campaign of September 2004. The sample and reference cells are filled with the same CO2 gas. Each point is associated to a pair of spectra, obtained after averaging over 30 laser scans. The mean δ13C value fully agrees with the expected zero value, within one standard error. This test confirms that a good accuracy level could be maintained during in-situ operation of the spectrometer.

Fig. 5.
Fig. 5.

Demonstration of field operation of the diode laser spectrometer in a quasi-continuous monitoring regime. Each point is associated to a set of ten measurements. The error bars correspond to two times the standard error. The horizontal lines indicate the range of laboratory IRMS determinations on gaseous samples sporadically collected from June 6, 2003, to September 20, 2004.

Tables (1)

Tables Icon

Table 1. In-situ isotope ratio determinations on volcanic CO2 collected through the off-line sampling system. In two cases, a pair of flasks has been filled nearly at the same time.

Equations (1)

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ε = ( δ 13 C + 1 ) ( X Δ 1 ( 1 Δ ) X 1 )

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