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No. 201: The Danish Air Quality Monitoring Programme. Annual Summary for 2015

Ellermann, T., Nygaard, J., Nøjgaard, J.K., Nordstrøm, C., Brandt, J., Christensen, J., Ketzel, M., Massling, A. & Jensen, S.S. 2016. The Danish Air Quality Monitoring Programme. Annual Summary for 2015. Aarhus University, DCE – Danish Centre for Environment and Energy, 65 pp. Scientific Report from DCE – Danish Centre for Environment and Energy No. 201. dce2.au.dk/pub/SR201.pdf

Summary

This report presents the result from the Danish Air Quality Monitoring Programme in 2015. 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 eleven monitoring stations; nine stations situated in the four largest cities, two stations located in background areas and a minor station in a suburban area. 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), polycyclic aromatic hydrocarbons (PAHs) and a number of heavy metals including lead (Pb), arsenic (As), cadmium (Cd), mercury (Hg) nickel (Ni), and a number of volatile organic compounds (VOCs) 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.

The permitted number of exceedances in a year of the diurnal limit value of 50 µg/m3 for PM10 was not exceeded at any station in the measuring network. Likewise, there were no exceedances of the annual limit values for PM10 (40 µg/m3) and PM2.5 (25 µg/m3 from 2015). The average exposure indicator (AEI) has decreased with 25% since 2010.                          

The number of particles in ambient air was about 14,000 particles per cm3 as annual average at the street station H.C. Andersens Boulevard. This is roughly a factor of 3 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 was about 1.6 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) 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 have decreased from 2014 to 2015 for most of the stations. At H.C. Andersens Boulevard (HCAB/1103) there were still elevated concentrations of NO2 compared to the situation before 2010 due to a permanent change in the traffic lanes at the street segment in front of the measurement station. Additionally, there has been a gradually decrease in the concentrations during the last years in parallel to the decrease observed at Jagtvej.

Model calculations at selected streets in Copenhagen and Aalborg indicate that the limit value was exceeded at 9 out of 98 calculated streets in Copenhagen but not at any streets in Aalborg in 2015. The number of street segments with model calculated exceedances has decreased to one third of the value in 2010.

The ozone levels in 2015 were on the same level as in 2014. No clear trend is observed for the average ozone concentration. The information threshold of 180 µg/m3 was not exceeded in 2015. The target value for the maximum daily 8 hours mean ozone concentration of 120 µg/m3 was not exceeded, but the long-term objective for this parameter was exceeded at all Danish stations. The læong term objective has not entered into force.

Measurements of volatile organic compounds (VOCs) at the urban background in Copenhagen showed concentration levels between 0.01 µg/m3 and 0.75 µg/m3 for the selected 17 different compounds. VOCs can act as ozone precursors, and the aim of these measurements is to improve the general understanding of the ozone formation on a European level. 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 concentrations of particle bound PAH were performed at H.C. Andersens Boulevard, Copenhagen and at the suburban measurement station at Hvidovre. The average concentration of benzo[a]pyrene was 0.29 ng/m3 and 0.25 ng/m3 at H.C. Andersens Boulevard and Hvidovre, respectively. The target value for benzo[a] pyrene (1 ng/m3) was not exceeded in 2015.

Measurements of the chemical content in PM2.5 showed that 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 of DCE (http://dce.au.dk/en/authorities/air/), in Danish
(http://dce.au.dk/myndigheder/luft/).