Ellermann, T., Massling, A., Løfstrøm, P, Winther, M., Nøjgaard, J. K. & Ketzel. M. 2012. Assessment of the air quality at the apron of Copenhagen Airport Kastrup in relation to the occupational environment. Aarhus University, DCE - Danish Centre for Environment and Energy, 51pp. - Technical report from DCE – Danish Centre for Environment and Energy No. 15. http://www2.dmu.dk/Pub/TR15.pdf

Summary

This report presents results from an assessment of air pollution at the apron[1] of Copenhagen Airport in relation to the working environment. The Assessment has been carried out during the period 2009 to 2011 by DCE - Danish Centre for Environment and Energy, Aarhus University (DCE) for Copenhagen Airports A/S. The present report is a translation of the original Danish version of the report (Ellermann et al., 2011).

The aim of the assessment was to investigate the air pollution at the apron and to identify sources of air pollution. The study focuses on the working environment. Therefore, the emphasis is on air pollution at the apron, with focus on the areas where the staff is mainly present during the working hours.

The assessment includes air pollutants, which are suspected to cause problems regarding the working environment at the apron. These are the following: Nitrogen oxides (NO and NO₂), sulfur dioxide (SO₂), the mass of particles with diameter below 2.5 µm (PM_{2. 5}), particle number[2] and their size distribution, particulate elemental carbon (soot), polycyclic aromatic hydrocarbons (PAH) and selected volatile organic compounds (VOC).

The assessment is based on a combination of measurements, compilation of an emission inventory and model calculations. The main elements are:

• Measurements of NO_X and PM_2.5 at the apron close to Gate B4 (Station B4 hereafter). Measurements of these compounds on the outskirts of Copenhagen Airport (Station East and West) are also included in the study. These measurements are performed by DCE for Copenhagen Airports A/S in connection with the monitoring of air quality at Copenhagen Airport.
• Measurements of particle number (6 – 700 nm in diameter)[3] and particle size at Station B4 and Stations East and West.
• Measurement campaign on the spatial distribution of air pollution at the apron.
• Measurement campaign on organic compounds, including PAH, selected VOC, particulate organic carbon and elemental carbon (soot).
• Measurement campaign on particle number and SO₂ and Station B4.
• Compilation of an emission inventory on the sources at the airport. The inventory includes emissions of NO_X, PM_2.5, VOC, carbon monoxide (CO) and total fuel consumption (jet fuel, diesel, etc.).
• Modeling of air pollution levels and source contributions. The model calculations include only NO₂, NO_X and PM_2.5. Model calculations for the apron itself are performed with a spatial resolution of 5 m x 5 m in order to better address the location of sources relative to the working areas and to assess the impact of buildings on the wind flow and dispersion of air pollution.

The study has led to the following main conclusions:

The concentrations of NO_X and SO₂ on the apron are below the levels at H.C. Andersens Boulevard (HCAB) measured in connection with the Danish air quality monitoring. HCAB is one of the busiest streets in Copenhagen (approximately 60,000 vehicles per day). Concentrations are also below the EU air quality limit values for these two compounds.

Measurements of VOC’s include organic substances that are partly found in the background air and partly expected to origin from sources at the apron (vehicles and aircraft), and which can cause adverse health effects. The measured VOC concentrations are in the same range or lower than typically found in urban background air in Copenhagen. N-octane and trimethyl benzene, which are related to jet fuel, are at a level of 2-6 times the levels measured in urban background, however the concentrations are still low. VOC’s are not routinely measured at HCAB, and therefore cannot be compared to the levels at a busy street. Only benzene is measured at HCAB. Measured benzene concentrations at the apron are below the levels at HCAB as well as the EU limit value.

Measurements also include aldehydes, which may cause sensory irritation of the eyes, nose and throat. Aldehydes are produced during combustion of jet fuel. The average concentrations (8 hour time-integrated measurements) of aldehydes at the apron are significantly below the levels expected to cause irritation. However, the peak concentrations for shorter time periods are unknown.

The study included a number of aspects on particle pollution in the airport. The results show that the particle number was about two to three times higher at the apron compared to HCAB. 85-90% of the particle numbers consist of particles with a diameter 6 – 40 nm. This particle fraction accounts for the difference between the particle number at the apron and HCAB. The ultrafine particles originate from combustion of jet fuel and diesel at the apron. At the outskirts of the airport, the particle number is about 20 – 40 % lower than at HCAB.

The larger particles with diameters up to 2.5 µm are measured by mass and called PM_2.5. The PM_2.5 level at the apron is approximately equivalent to HCAB while the PM_2.5 level at Station East and West are intermediate the levels measured at HCAB and urban background in Copenhagen. These particles originate mainly from sources outside the airport.

The particle-bound PAH concentration at the apron is about one third or less of the concentrations measured at HCAB. PAH concentrations are furthermore below the levels measured at the apron at the Leonardo Da Vinci Airport in Rome (Cavallo et al., 2006). The EU has established a limit value for benzo(a)pyrene (1 ng/m³), which is considered as representative for the carcinogenic PAH. The limit value is not exceeded in the 4-week measurement campaign.

Measurements also included elemental carbon (EC, also known as soot) in the particles. Levels at the airport are slightly less than half of the levels measured at HCAB. On the other hand, the amount of particulate organic carbon (OC) is comparable to HCAB, indicating that there must be a source of these substances on or near to the airport. This has not been studied in detail.

A geographically detailed emission inventory was compiled for NO_X, PM_2.5, VOC and CO. The uncertainty of the inventory is relatively high due to the many hundreds of different air pollution sources at the apron.

For NO_X and PM_2.5, the greatest share of emissions originates from handling vehicles[4], followed by the aircraft’s APU (auxiliary power units), aircraft main engines and the smallest proportion from traffic at the apron. For VOC and CO the emissions are dominated by contributions from the aircraft main engines.

Furthermore, the emission inventory indicates that up to half of the particle emissions from aircraft main engines are due to the high sulfur content of about 900 ppm in the jet fuel. The combustion of sulfate-rich fuels leads to the formation of sulfur-containing ultrafine particles. Measurements of sulfur dioxide also indicate a linkage between sulfur and the large particle number.

Model calculations have shown higher concentrations of NO_X at the apron compared to the measurements. A detailed comparison between model results and measurements indicate that the most likely reason for this difference is that the emission inventory results in too high emissions at the apron. Thus it is desirable to review the basic input data behind the emission inventory. Unfortunately, this has not been possible within the framework of this study. Instead, the model results have been adjusted empirically on the basis of the measurements. In this way the model calculations can be used to determine the spatial distribution of pollution and the relative source contributions.

The calculations show that NO_x at the apron originate primarily from background (44%) and handling (41%) with smaller contributions from the APU (7%), main engines (7%) and traffic at the apron (1%). The numbers refer to Station B4, which is located at Gate B4.

Model calculations show that PM_2.5 at the apron comes primarily from background (91%) with smaller contributions from handling (5.5%), APU (3.4%), main engines (0.4%) and traffic at the apron (0.1%).

Model calculations show that the apron is the location, where the airport staff is most likely exposed to elevated levels of NO_X and PM_2.5.

As mentioned above, the project did not include an emission inventory for particle numbers. It has therefore not been possible to make a proper assessment of the sources of particle number on the basis of model calculations. However, it is expected that handling, APU and main engines are the major sources for particle number while the background plays a minor role. Measures taken to reduce the high particle number at the apron should involve reduction measures for all the expected major sources.

In summary it can be concluded that the concentrations at the apron for the majority of the investigated air pollutants (NO_X, PM_2.5, PAH, VOC, particulate organic and elemental carbon) are below the levels measured at HCAB. Furthermore, at the apron there are no measured excedances of the air quality limit values for those air pollutants where limit values exist.

The particle number is the only deviation from this picture, since the levels measured at the apron is about two to three times higher than at HCAB. There is no air quality limit value for particle number.