Open-Path Laser Absorption Sensor for Mobile Measurements of Atmospheric Ammonia.

Area of Science:

• Environmental Science
• Analytical Chemistry
• Sensor Technology

Background:

• Anthropogenic ammonia emissions, primarily from agriculture, pose risks to environmental and human health.
• Accurate detection and quantification of ammonia are crucial for mitigation strategies.
• Mobile sensing platforms offer scalable, high-throughput measurement capabilities but require compact, low-power sensors.

Purpose of the Study:

• To develop and present a compact, low-power ammonia sensor system for mobile applications.
• To demonstrate the sensor's performance in laboratory and field conditions.
• To enable autonomous, real-time monitoring of ammonia emissions.

Main Methods:

• Wavelength modulation spectroscopy (WMS) integrated with a Herriott multi-pass cell.
• Utilized a quantum cascade laser (QCL) operating at 10.33 µm.
• Employed an open-path configuration for enhanced time-response and mitigation of sticky-gas effects.

Main Results:

• The developed sensor package is small (~20 L), lightweight (~3.5 kg), and battery-powered (<30 W).
• Laboratory tests demonstrated high accuracy (<~2%) and precision (~4 ppb in 1 s).
• Successful initial field deployments were conducted using ground vehicles and a fixed-wing unmanned aerial vehicle (UAV).

Conclusions:

• The presented WMS-based ammonia sensor is suitable for mobile deployment due to its compact size, low power consumption, and autonomous operation.
• The sensor achieves high accuracy and precision, meeting the demands for environmental monitoring.
• Field deployments confirm the viability of the sensor for real-time ammonia emission detection from various mobile platforms.