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Hurdal – a regional background station

Foto: Dorothea Schulze, NILU

In forest east of Hurdal Lake stands what we call a regional background station. There, NILU measures tropospheric ozone, particles, carbonaceous compounds, and sulphur- and nitrogen-containing compounds in air, as well as inorganic compounds and heavy metals in the rain on behalf of the Norwegian Environment Agency.

The term “Regional background station” designates a station where long-range transported air pollution is measured. In other words, it measures substances that are transported by weather and wind from afar. The station is part of the European Monitoring and Evaluation Programme (EMEP). The purpose of EMEP is to monitor air pollution that is transported across borders in Europe.

Hurdal station has a close cooperation with the Norwegian Institute for Bioeconomy Research (NIBIO).
Hurdal is one of three Norwegian stations that are engaged in intensive forest surveillance. One of the objectives is to study the effects of air pollution on forests, soil and vegetation.


The monitoring station in Hurdal was originally established at Nordmoen in 1987. It was moved to its current position in 1998 because of the amount of local pollution at Nordmoen became excessive.

The monitoring station itself is fairly inconspicuous. It consists of two small arches and, on the ground, some instruments for collecting precipitation and particles.

Measurement instruments on the mast

What you will notice as you pass by Hurdal is the 25-metre mast. This is the only place where NILU has a mast this tall. The reason for this is that long-range transported air pollution at the site must be measured well above the treetops, the air is more representative of the region than it is in the forest.
The measurement instruments ride up and down from the top of the mast in a specially constructed box, a Rube Goldberg contraption that makes it possible to take samples at several heights. The filters in the instrument are changed every day by the station attendant.

This person is not a NILU employee but is commissioned by the Institute to do these tasks. The filters, precipitation samples and other samples are collected and sent to the NILU lab every week.

Currently, NIBIO is in the process of replacing the mast with a larger version that will reach higher and have room for more measurements. This is part of efforts to establish Hurdal station as part of the European Integrated Carbon Observation System (ICOS).

Data from regional background stations such as Hurdal must be gathered over a long time period if they are to be valuable for research and environmental management. A data series may need to span decades in order to be used to understand and document changes in the composition of the atmosphere. The measurements must also be performed correctly and with adequate frequency. It must be possible both to relate the composition of local air to transport and transformation in the atmosphere, and to compare local measurements with results obtained at other sites and in other countries.

Report with data from the monitoring station in Hurdal:

“Monitoring of long-range transported air pollutants in Norway. Annual report 2018.”: https://nilu.brage.unit.no/nilu-xmlui/handle/11250/2621490