Power-modulated integrated path differential absorption lidar for probing benzene concentration

Area of Science:

• Atmospheric Remote Sensing
• Laser Spectroscopy
• Environmental Monitoring

Background:

• Accurate regional atmospheric benzene detection is crucial for environmental and health assessments.
• Traditional methods face limitations in real-time, open-path monitoring capabilities.
• Differential absorption lidar (DIAL) techniques offer potential for selective gas detection.

Purpose of the Study:

• To introduce and demonstrate a novel power-modulated integrated path differential absorption (PM-IPDA) lidar system for regional benzene detection.
• To evaluate the system's performance, including its detection limit and real-time monitoring capabilities.
• To assess the system's robustness against interfering gases and noise sources.

Main Methods:

• Utilized two tunable interband cascade lasers (ICLs) operating at approximately 3.2 µm (3236.6 nm and 3187.1 nm) for PM-IPDA lidar.
• Employed a fast Fourier transform algorithm for data retrieval with a time resolution of 0.1 s.
• Optimized modulated frequency to 10 kHz and addressed wavelength fluctuations through system design.

Main Results:

• The PM-IPDA lidar demonstrated effective mitigation of interference from H2O, CH4, and HCl.
• Laboratory experiments confirmed the system's ability to reduce errors from 1/f noise.
• Open-path experiments achieved a benzene detection limit of approximately 0.60 mg·m⁻³.

Conclusions:

• The developed PM-IPDA lidar system is suitable for regional, open-path, real-time benzene detection.
• The system's design minimizes impacts from wavelength fluctuations and interfering atmospheric gases.
• This technology offers a promising solution for continuous environmental monitoring of benzene.