They monitor NO2, SO2 and PM10 particles. The contracts started the 1st of January 2016 and the measurements are performed on behalf of Arvika and Trelleborg municipality and are made in accordance with the Swedish Environmental Protection Agency.
Both Arvika and Trelleborg monitoring stations have web sites where you can follow and read more about the measurements.
The monitoring stations in Trelleborg and Arvika are parts of the OPSIS BOO concept.