Aarhus Universitets segl

No. 67: The Danish Air Quality Monitoring Programme. Annual Summary for 2012

Ellermann, T., Nøjgaard, J.K., Nordstrøm, C., Brandt, J., Christensen, J., Ketzel, M., Jansen, S., Massling, A. & Jensen, S. S. 2013: The Danish Air Quality Monitoring Programme. Annual Summary for 2012. Aarhus University, DCE – Danish Centre for Environment and Energy. 59 pp. Scientific Report from DCE – Danish Centre for Environment and Energy. No. 67. http://dce2.au.dk/pub/SR67.pdf


Summary and Conclusion

This report presents the result from the Danish Air Quality Monitoring Programme in 2012. The monitoring programme is carried out by the DCE - Danish Centre for Environment and Energy (DCE) at Aarhus University. The core part of this programme consists of continuous measurements at nine monitoring stations; seven stations situated in the four largest cities and two stations located in background areas. These measurements are supplemented with model calculations using DCE’s air quality models.

The aim of the program is to monitor air pollutants relevant to human health in accordance with the EU air quality directives. The programme includes measurements of sulphur dioxide (SO2), nitrogen oxides (NOx/NO2), particulate mass (PM10 and PM2.5), particle number, benzene (C6H6), toluene (C7H8), carbon monoxide (CO), ozone (O3), lead (Pb), arsenic (As), cadmium (Cd), mercury (Hg), nickel (Ni), and polycyclic aromatic hydrocarbons (PAH). In 2009 the programme was expanded with measurements of a number of volatile organic compounds (VOC’s) that are precursors for formation of ozone. The measurements and model calculations are used to evaluate the Danish air quality in relation to limit values as well as to follow trends. Further, the program serves as basis for determination of sources of the air pollutants, basis for evaluation of the impact of regulations of emissions and as basis for various research projects related to air quality.

In 2012 the daily limit value for PM10 were not exceeded at any station in the measuring network including stations where exceedances previously have occurred (e.g. the two traffic stations in Copenhagen). There were likewise no exceedances of the annual limit values for PM10 (40 µg/m3) and PM2.5 (25 µg/m3 from 2015).

The number of particles in ambient air was about 14000 particles per cm3 at the street station H.C. Andersens Boulevard. This is a factor of about 2.5 and 5 higher than in urban and rural background, respectively. A significant reduction in particle number has been observed since 2002.

The sodium content in PM10 on street stations were about 1.5 µg/m3 corresponding to an estimated annual salt content (NaCl) of about 4.0 µg/m3. High diurnal values of salt were observed during periods with winter salting of roads.

The annual limit value for NO2 (40 µg/m3 in 2011) was exceeded at one street station in Copenhagen (H.C. Andersens Boulevard), whereas no exceedances were observed in Odense, Aalborg and Aarhus. The NO2 concentrations decreased from 2011 to 2012 at part of the stations while no changes was observed at the remaining part. At H.C Andersens Boulevard (Copenhagen/1103) there were still elevated concentrations of NO2. The background for these elevated concentrations are currently investigated in an on-going project for the Danish Environmental Protection Agency.

Model calculations at selected streets in Copenhagen and Aalborg indicate that the limit value was exceeded at several streets in Copenhagen but not at any streets in Aalborg in 2012. In general, modelling confirmed that the street station at H.C. Andersens Boulevard (1103) in Copenhagen represents one of the most polluted streets in Copenhagen, whereas the traffic station in Aalborg (6153) represents a site with a pollution level around the average for the 31 selected streets in Aalborg.

The ozone levels were in 2012 almost the same as in 2011 at all rural and urban background stations and no clear trend was thus observed. The information threshold at 180 µg/m3 was exceeded once in 2012. The target value for the max 8 hours ozone concentration on 120 µg/m3 was not exceeded, but the long-term objective for this target was exceeded at all non-traffic stations.

The report presents results for volatile organic compounds (VOC) measured at the urban background in Copenhagen. VOC’s can act as ozone precursors, although the formation of ozone in Denmark is in general small due to moderate solar radiation. The ozone pollution in Denmark is to a large extent the result of long distance transport of pollutants from other European countries south of Denmark.

The levels of SO2 and heavy metals have decreased for more than two decades and are now far below the limit values. The limit values for benzene and CO are not exceeded and the levels have decreased for the last decade.

Measurements of particle bound PAH concentrations were performed at H.C. Andersens Boulevard, Copenhagen. The average concentration of benzo[a]pyrene was 0.25 ng/m3. The target value for benzo[a] pyrene (1 ng/m3) was not exceeded in 2012.

For the second time this report presents results from determination of the chemical content in PM2.5. The annual average concentrations of NH4+, Na+, K+, Mg2+, Cl-, NO3-, SO42- are very similar at the street station at H.C. Andersens Boulevard and at the rural station at Risø. The main difference between the two stations are for elemental carbon (EC), organic matter (OM) and Ca2+ where the concentrations are higher at the street station compared to the rural background station. This is mainly due to emissions of these compounds from the traffic in Copenhagen.

Actual data, annual and multi-annual summaries are available at the website