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A laser photoacoustic analysis of residual CO₂ and H₂O in larch stems.

Ageev B, Ponomarev Y, Sapozhnikova V, Savchuk D - Biosensors (Basel) (2014)

Bottom Line: Every so often, the results obtained from investigations into the effects of varying environmental conditions on the tree growth rate at the same sites and on the change in the carbon balance in plants, using traditional methods, are found to differ widely.Conclusions are made regarding the response of annual larch CO2 disc tree ring distributions to climatic parameters (temperatures and precipitation).The data about the CO2 disc content for different sites are compared.

View Article: PubMed Central - PubMed

Affiliation: Zuev Institute of Atmospheric Optics, Siberian Branch of the Russian Academy of Sciences, 1 Academician Zuev Square, Tomsk 634021, Russia. ageev@asd.iao.ru.

ABSTRACT
Every so often, the results obtained from investigations into the effects of varying environmental conditions on the tree growth rate at the same sites and on the change in the carbon balance in plants, using traditional methods, are found to differ widely. We believe that the reason for the ambiguity of the data has to do with failure to account for the role of the residual CO2 (and H2O) in the tree wood exhibiting a climate response. In our earlier work, the results of a laser photoacoustic gas analysis of CO2 and H2O vacuum-desorbed from disc tree rings of evergreen conifer trees were presented. In this paper, laser photoacoustic measurements of tree ring gases in deciduous conifer trees and CO2 carbon isotope composition determined by means of a mass spectrometer are given. Conclusions are made regarding the response of annual larch CO2 disc tree ring distributions to climatic parameters (temperatures and precipitation). The data about the CO2 disc content for different sites are compared.

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Coincidence of the CO2 and H2O absorption lines in the 10.6 µm region and the СO2 and H2O frequency dependence of the calculated absorption coefficients (km−1).
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biosensors-05-00001-f001: Coincidence of the CO2 and H2O absorption lines in the 10.6 µm region and the СO2 and H2O frequency dependence of the calculated absorption coefficients (km−1).

Mentions: A laser photoacoustic analysis based on different laser sources is a modern gas detection tool used to advantage in many applications for a long time. Our experimental system and a procedure for investigating the CO2 and H2O content in gas samples extracted under vacuum from disc tree rings were described elsewhere (see, for example, [7,8]). The measurements were performed by a laser photoacoustic (PA) spectrometer using a computerized model of a tunable waveguide 10.6 µm CO2 laser operating in four CO2 laser lines: 10 P (20, 16, 14) coinciding with the CO2 absorption lines and 10 R (20) coinciding with the CO2 and water-vapor absorption lines (CO2 + H2O). The wood in each of the rings was planed down with special chisels. Samples of the same weight were placed in four exposure chambers evacuated to obtain a short-term vacuum and provide wood-sorbed gas release. In all the measurements, the gas samples (P = 6–8 Torr) from the exposure chambers were admitted to an evacuated PA cell. A PA signal was generated due to nonradiative de-excitation of the energy absorbed in optical transitions by the gas under study. The absorbed power was determined directly from heat, and the PA signal was generated in the gas sample. The acoustic waves were then measured by a PA cell microphone. Therefore, the PA spectrum could be correlated with the optical absorption spectra of the sample. Once the system was calibrated, i.e., the absorption in gases with known concentration was measured, the calibration coefficient was found, and the absorbing component concentrations in the gas sample studied were determined. The experimental conditions (air was added to the PA cell to provide a pressure of 100 Torr) enabled us to obtain approximately the same absorption coefficients of the samples in the 10 P (20, 16 and 14) laser lines and provide maximum photoacoustic absorption detection sensitivity. The amplitudes U and Uair of the signals from the mixture under investigation and air were recorded, ΔU = U − Uair was determined, and the relative CO2 content in the gas sample for each disc tree ring was found, using a calibration curve. The amplitude of the photoacoustic signal was proportional to the CO2 and H2O concentrations of the absorbing components of the gas samples under study to within a constant calibration factor. The results were the mean of the measured values for the three laser lines, and the relevant correlation coefficients were 0.85–0.9. The ultimate absorption coefficient detection sensitivity of the spectrometer used was 2 × 10−5 cm−1 for a laser power of 70 mW, and the calibration measurement error was no more than ±5%. Figure 1 illustrates the coincidence of the CO2 and H2O spectra.


A laser photoacoustic analysis of residual CO₂ and H₂O in larch stems.

Ageev B, Ponomarev Y, Sapozhnikova V, Savchuk D - Biosensors (Basel) (2014)

Coincidence of the CO2 and H2O absorption lines in the 10.6 µm region and the СO2 and H2O frequency dependence of the calculated absorption coefficients (km−1).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4384077&req=5

biosensors-05-00001-f001: Coincidence of the CO2 and H2O absorption lines in the 10.6 µm region and the СO2 and H2O frequency dependence of the calculated absorption coefficients (km−1).
Mentions: A laser photoacoustic analysis based on different laser sources is a modern gas detection tool used to advantage in many applications for a long time. Our experimental system and a procedure for investigating the CO2 and H2O content in gas samples extracted under vacuum from disc tree rings were described elsewhere (see, for example, [7,8]). The measurements were performed by a laser photoacoustic (PA) spectrometer using a computerized model of a tunable waveguide 10.6 µm CO2 laser operating in four CO2 laser lines: 10 P (20, 16, 14) coinciding with the CO2 absorption lines and 10 R (20) coinciding with the CO2 and water-vapor absorption lines (CO2 + H2O). The wood in each of the rings was planed down with special chisels. Samples of the same weight were placed in four exposure chambers evacuated to obtain a short-term vacuum and provide wood-sorbed gas release. In all the measurements, the gas samples (P = 6–8 Torr) from the exposure chambers were admitted to an evacuated PA cell. A PA signal was generated due to nonradiative de-excitation of the energy absorbed in optical transitions by the gas under study. The absorbed power was determined directly from heat, and the PA signal was generated in the gas sample. The acoustic waves were then measured by a PA cell microphone. Therefore, the PA spectrum could be correlated with the optical absorption spectra of the sample. Once the system was calibrated, i.e., the absorption in gases with known concentration was measured, the calibration coefficient was found, and the absorbing component concentrations in the gas sample studied were determined. The experimental conditions (air was added to the PA cell to provide a pressure of 100 Torr) enabled us to obtain approximately the same absorption coefficients of the samples in the 10 P (20, 16 and 14) laser lines and provide maximum photoacoustic absorption detection sensitivity. The amplitudes U and Uair of the signals from the mixture under investigation and air were recorded, ΔU = U − Uair was determined, and the relative CO2 content in the gas sample for each disc tree ring was found, using a calibration curve. The amplitude of the photoacoustic signal was proportional to the CO2 and H2O concentrations of the absorbing components of the gas samples under study to within a constant calibration factor. The results were the mean of the measured values for the three laser lines, and the relevant correlation coefficients were 0.85–0.9. The ultimate absorption coefficient detection sensitivity of the spectrometer used was 2 × 10−5 cm−1 for a laser power of 70 mW, and the calibration measurement error was no more than ±5%. Figure 1 illustrates the coincidence of the CO2 and H2O spectra.

Bottom Line: Every so often, the results obtained from investigations into the effects of varying environmental conditions on the tree growth rate at the same sites and on the change in the carbon balance in plants, using traditional methods, are found to differ widely.Conclusions are made regarding the response of annual larch CO2 disc tree ring distributions to climatic parameters (temperatures and precipitation).The data about the CO2 disc content for different sites are compared.

View Article: PubMed Central - PubMed

Affiliation: Zuev Institute of Atmospheric Optics, Siberian Branch of the Russian Academy of Sciences, 1 Academician Zuev Square, Tomsk 634021, Russia. ageev@asd.iao.ru.

ABSTRACT
Every so often, the results obtained from investigations into the effects of varying environmental conditions on the tree growth rate at the same sites and on the change in the carbon balance in plants, using traditional methods, are found to differ widely. We believe that the reason for the ambiguity of the data has to do with failure to account for the role of the residual CO2 (and H2O) in the tree wood exhibiting a climate response. In our earlier work, the results of a laser photoacoustic gas analysis of CO2 and H2O vacuum-desorbed from disc tree rings of evergreen conifer trees were presented. In this paper, laser photoacoustic measurements of tree ring gases in deciduous conifer trees and CO2 carbon isotope composition determined by means of a mass spectrometer are given. Conclusions are made regarding the response of annual larch CO2 disc tree ring distributions to climatic parameters (temperatures and precipitation). The data about the CO2 disc content for different sites are compared.

Show MeSH
Related in: MedlinePlus