11:00 AM - 1:00 PM
[AAS11-P08] Continuous carbonyl sulfide concentration measurement using a portable mid-infrared laser spectrometer
Keywords:Carbonyl sulfide, Carbon dioxide, Laser spectrometer
Carbonyl sulfide (COS) is the most abundant sulfur-containing gas in the ambient atmosphere, with an average mixing ratio of 500 parts per trillion (ppt) by volume in the troposphere. Plant leaves consume COS during photosynthetic CO2 assimilation, however, they do not emit COS to the atmosphere through respiration. This assimilation-respiration difference sets COS as a potential tool to distinguish between CO2 fixation and emission by photosynthesis and respiration. As large uncertainties in the COS budget remain under natural environmental conditions, field measurements of COS and CO2 concentrations are required for testing and validating the COS tracer method.
Recently, a portable continuous COS concentration analyzer using a mid-infrared laser-based has been put on the market. However, the precision of the COS measurement of the analyzer was insufficient, and it was necessary to inject calibration gas many times in a short time. In order to reduce gas consumption, we have examined the mid-infrared laser-based analyzer to improve its stability. We have tested its suitability to obtain accurate and high precision measurements of COS. To stabilize the laser intensity, the temperature around the laser cell was controlled by a double thermostatic bath. This temperature control of the laser cell reduced the standard deviation of the measurement by more than half and the frequency of calibration gas injections by less than one-third. We report this technical examination and the results of actual observations of COS concentrations in a forest ecosystem in Japan.
Acknowledgment:
SOD and KK want to express their gratitude to Shohei Hattori for proposing the MIRApico as a COS concentration analyzer implemented in this report.
Recently, a portable continuous COS concentration analyzer using a mid-infrared laser-based has been put on the market. However, the precision of the COS measurement of the analyzer was insufficient, and it was necessary to inject calibration gas many times in a short time. In order to reduce gas consumption, we have examined the mid-infrared laser-based analyzer to improve its stability. We have tested its suitability to obtain accurate and high precision measurements of COS. To stabilize the laser intensity, the temperature around the laser cell was controlled by a double thermostatic bath. This temperature control of the laser cell reduced the standard deviation of the measurement by more than half and the frequency of calibration gas injections by less than one-third. We report this technical examination and the results of actual observations of COS concentrations in a forest ecosystem in Japan.
Acknowledgment:
SOD and KK want to express their gratitude to Shohei Hattori for proposing the MIRApico as a COS concentration analyzer implemented in this report.