Real-Time Urban Monitoring of Ammonia in Ambient Air During the Deployment of a Cavity-Ring Down Spectroscopy Instrument in China and South Korea

Ammonia (NH₃) has been recognized as a critical contributor to air pollution not only on eutrophication and acidification of land and fresh waters, but also on the formation of aerosols with acidic pollutants such as sulfur dioxide (SO₂) and the oxides of nitrogen (NO_x) to produce the secondary particulate matter (PM) in the atmosphere. These particulate ammonium species degrade the quality of air and increase the health risk to people living in the polluted regions. Tracing and controlling the emission of NH₃ are important to reduce PM2.5 and PM10 in the air. The agriculture activities including usage of nitrogen-based fertilizers, the industrial and traffic emissions are believed to be responsible for the increase of NH₃ concentration in the atmosphere. Limited ammonia monitoring is currently a barrier for an in-depth understanding of the vital role of NH₃ in PM formation during pollution events.

Here we present a high-precision gas analyzer that utilizes the technique of Cavity Ring-Down Spectroscopy (CRDS) to measure ammonia concentration with new developments to specifically overcome the technical difficulties associated with real-time NH₃ monitoring. Its compact and rugged design combined with high precision and long-term stability allows the user to deploy the instrument in the field for continuous measurement of atmospheric NH₃ level. We will present results of urban NH₃ monitoring conducted during the field deployments of the Picarro G2103 ammonia analyzers in two cities located in China and in South Korea. The campaign demonstrates the fast response to the NH₃ concentration change in ambient air provides reliable and valuable real-time information about critical local NH₃ changes.