Open-path multi-species remote sensing with a broadband optical parametric oscillator

Area of Science:

• Environmental monitoring
• Spectroscopy
• Atmospheric chemistry

Background:

• Fugitive emissions from industrial sites pose environmental risks.
• Open-path remote sensing offers a method for monitoring these emissions.
• Volatile organic compounds (VOCs) require accurate quantification.

Purpose of the Study:

• To develop and demonstrate a path-integrated sensing system for simultaneous VOC measurements.
• To quantify hydrocarbon gas fluctuations above ambient levels.
• To assess the system's sensitivity and range for industrial emission monitoring.

Main Methods:

• Utilized Fourier-transform spectroscopy with 0.05-cm^-1 resolution.
• Employed an ultrafast optical parametric oscillator as a broadband mid-infrared source (3.1-3.5 µm).
• Performed path-integrated concentration measurements using a simple target at 70 m.

Main Results:

• Achieved simultaneous concentration measurements of water, methane, and ethane.
• Observed real-time concentration changes by simulating a fugitive emission (2% methane in air).
• Demonstrated a methane detection sensitivity of 595 ppb·m.

Conclusions:

• The developed system can resolve few-ppb concentrations of VOCs at 50-100 m ranges.
• This technology is critical for effective monitoring of fugitive industrial emissions.
• High signal-to-noise ratios enable accurate quantification of gas fluctuations.