Continuous Monitoring of the Methane Concentration in the Atmosphere by IR Spectrometry with a 1.66-μm Diode Laser

Nakaya, Toshiro; Kobayashi, Kensei; Akagi, Tetsuya; Kimura, Kiyoshi; Tai, Hideo

doi:10.2116/analsci.16.1211

Cited by 5 publications

(3 citation statements)

References 8 publications

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“…Methane concentrations were measured using a laser methane gas detector (SA3C15A; Anritu Co. Ltd., Atsugi, Japan), which can yield atmospheric concentrations at the ppm level. Nakaya et al (2000) reported that atmospheric methane concentrations determined by this technique are in agreement with gas chromatography measurements done with a flame ionization detector. The laser detector method has been applied to monitor methane emissions in paddy fields .…”

Section: Measurements Of Methane Concentration In the Atmospheresupporting

confidence: 65%

Estimation of methane emission rates from a rice paddy field using a naturally ventilated tunnel

et al. 2012

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A novel system for monitoring methane emission from a flooded paddy field was developed in order to quantify the greenhouse gas emission in near‐natural conditions. A paddy field planted with rice was covered by a semi‐open vinyl tunnel (1.8 × 10 × 2.5 m), and the methane concentrations inside and outside the tunnel were measured continuously from the booting stage to the ripening stage (August–September) using a methane gas detector. Methane emission rates were calculated on an hourly basis from the differences between the internal and external methane concentrations and the natural diffusion rates determined using a tracer gas method. The results indicated that the paddy field emitted 0.41–1.32 g methane m−2 day−1 during the two growth stages. The vinyl tunnel had no adverse effect on the growth and yield of rice plants inside. Despite the disadvantage of non‐accurate estimation under windy conditions, the technique is considered to be of potential value for evaluating methane emissions from a flooded paddy field.

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Section: Measurements Of Methane Concentration In the Atmospheresupporting

confidence: 65%

Estimation of methane emission rates from a rice paddy field using a naturally ventilated tunnel

et al. 2012

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“…Remote gas sensing and concentration measurements are mainly based on utilization of laser lidars [4] and "open path" sensing systems [5], which bring the average concentration level of gases along the laser beam propagation path. Usage of these systems in water conditions is not possible due to high attenuation level of water medium.…”

Section: Remote Measurementmentioning

confidence: 99%

Remote intelligent concentration measurement of gas dissolved in water

Kukhtin¹

2010

J. Phys.: Conf. Ser.

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“…During the 1980s, TDLAS systems quickly emerged as a practical trace-gas sensing method for airborne atmospheric research (e.g. Hastie and Miller, 1985;Schiff et al, 1983;Webster, 1988) and were further refined through the development of field-deployable atmospheric research systems (D'Amato et al, 2002;Durry and Pouchet, 2002;Gardiner et al, 2010;Gurlit et al, 2005;Iseki, 2004;Nakaya et al, 2000;Richard et al, 2002;Simpson et al, 1995;Uehara et al, 1997;Wienhold et al, 1994).…”

Section: Advancements In Tdlasmentioning

confidence: 99%

Design of an Optical Fiber-Coupled Sensor for Ambient Methane Measurement

Schoonbaert¹

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A tunable diode laser system was developed for remote monitoring of ambient methane using fiber optically connected all-optical sensor heads. Experiments were performed to quantitatively evaluate the influence of selected system hardware and software configurations, with the further goal of enabling measurements of ambient methane concentrations over an intrinsically-safe fiber optic network at sufficient precision and sensitivity to detect unknown fugitive emission sources. The designed system could switch between the sweep integration (SI) and wavelength modulation spectroscopy (WMS) detection methods, which inferred the methane volume mixing ratio from an absorption or second-harmonic (2f) feature respectively. Signals controlling the laser injection current were optimized to balance trade-offs between measurement precision and system sensitivity, and fiber optic components were thermally stabilized to reduce system drift. Starting from this base system, experiments were performed to evaluate the effectiveness of theory-based and experimental calibration methods, software and dual laser approaches to estimating the absorption-free intensity, different signal processing approaches to suppress effects of residual amplitude modulation (RAM) of the laser output intensity, and methods to reduce system drift. Tests also considered effects of varying fiber lengths between the central laser control hardware and the remotely located optical sensor heads. Finally, long-term stability was evaluated by quantifying bias (drift) and precision uncertainty in tests up to 16 months after initial calibration. The best measurement performance was achieved using the WMS method with thermally stabilized optical components within the central control hardware combined with a theory-based calibration, automated daily calibration supported by concurrent softwarebased estimation of the absorption-free intensity, and pair-wise averaging of the 2f feature maxima in each sweep period to suppress effects of RAM. At an averaging time of 1 s and methane concentrations between 1.0 and 50 ppm v , the system implementing the 2f-WMS method surpassed the methane volume mixing ratio measurement targets with a precision of 1.6 ppm v (absorbance of 6.57×10 -7 cm -1 ) and lower detection limit (LDL) of 1.5 ppm v (6.13×10 -7 cm -1 ). In achieving these values, thermal stabilization was responsible for a 93% reduction in the precision uncertainty; adding the concurrent software-based absorption-free intensity estimate netted a further reduction of 73%; and implementing RAM suppression via pair-wise averaging of the resolved 2f features within each sweep period technique allowed a further reduction of 9%.3

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Continuous Monitoring of the Methane Concentration in the Atmosphere by IR Spectrometry with a 1.66-μm Diode Laser

Cited by 5 publications

References 8 publications

Estimation of methane emission rates from a rice paddy field using a naturally ventilated tunnel

Estimation of methane emission rates from a rice paddy field using a naturally ventilated tunnel

Remote intelligent concentration measurement of gas dissolved in water

Design of an Optical Fiber-Coupled Sensor for Ambient Methane Measurement

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