In Situ and Loss-Free Detection of Nitrate Radical via Open-Path Cavity-Enhanced Absorption Spectroscopy: Indoor Air...

Area of Science:

• Atmospheric Chemistry
• Spectroscopy
• Air Quality Monitoring

Background:

• Nitrate radical (NO3) is a key atmospheric oxidant.
• Current optical cavity methods for NO3 measurement face significant sampling losses, especially in humid or particle-laden air, leading to uncertainties.

Purpose of the Study:

• To introduce and validate an open-path cavity-enhanced absorption spectroscopy (OP-CEAS) method for NO3 measurement.
• To address the limitations of closed-path systems, particularly sampling losses and interferences.

Main Methods:

• Development of an OP-CEAS system for ambient NO3 detection.
• Implementation of an algorithm with a dynamic reference library and real-time H2O cross-section calculation to correct for water vapor and environmental fluctuations.
• Testing the system in a typical indoor environment.

Main Results:

• The OP-CEAS method demonstrated negligible sampling loss and enhanced measurement performance compared to closed-path CEAS.
• The developed algorithm effectively eliminated interferences from water vapor and environmental drifts.
• Robust NO3 measurements were achieved even under elevated humidity conditions.
• High NO3 levels were detected in an indoor environment, indicating potential for indoor oxidant chemistry research.

Conclusions:

• The OP-CEAS approach offers a robust, loss-free method for continuous NO3 measurements.
• This technology provides a dependable tool for indoor air quality assessment and the study of indoor atmospheric chemistry.