Continuous NH3 Monitoring in Swiss National Air Quality Network

Omnisens Trace Gas Analyser TGA300 are photoacoustic based devices designed and optimized for continuous and automated ammonia measurement at subppb level with high temporal resolution. These combined featured are crucial for the survey of NH3 at national and international level and for understanding its role in the formation of ambient fine particulate matter (PM2.5). The time resolution and the intrinsic high dynamic range (0 to 6ppm) allow monitoring the contribution of farming activities like manuring whilst the excellent resolution (0.1ppb) is ideal for the measurement of ambient levels resulting from local emission and transboundary pollution, and for the validation of the associated theoretical models.

In 2002, EMPA, a Swiss institute responsible for air quality monitoring, and Omnisens started a successful collaboration in view of providing analyzers suitable for an automated network. Following a year test phase, the instruments were gradually deployed in the so called NABEL network, made of 16 fully automated stations spread over the Swiss territory, featuring urban and agricultural areas up to the alpine summits. TGA310 are currently installed at representative locations in the network. These activities are complemented by a dense network of passive samplers measuring NH3 as two weeks average values.

Apart from continuous measurement of NH3 in Switzerland, TGA310 provided important scientific results. For instance a correlation between NH3 concentration and road traffic was demonstrated and, at rural sites, the NH3 concentration was found to be in thermodynamic equilibrium with the aerosol phase during most time of the year.

Building on the Swiss experience, TGA310 are now gradually deployed in Europe and Japan.