CHEERS · Chemical and Physical Properties and Source Apportionment of Airport Emissions in the context of European Air Quality Directives

Chemical and Physical Properties and Source Apportionment of Airport Emissions in the context of European Air Quality Directives

Background. Ambient air pollution, particularly airborne particulate matter (PM), exerts a large influence on public opinion and with policy-makers and the scientific community because of its known adverse effects on human health and its complex implications for climate. In 2013, following the evidence of severe effects upon public health, both outdoor air pollution and airborne particulate matter were included as known carcinogens (Class-1) by the International Agency for Research on Cancer. The transformation and combustion of fossil fuels are amongst the main sources worldwide impacting upon air quality for PM. Besides the well recognised sources which combust fossil fuels (e.g., road traffic, shipping, industries, domestic heating), aviation deserves particular attention because of the rapid growth of civil aviation (about +5% every year). This trend is expected to continue over the next decades. Objectives. The goals of the project CHEERS arise from the research needs associated with airport emissions. Therefore, the project aimed to investigate the impacts of major European airports upon local air quality, and the main goal was to quantify the impacts due to aircraft, road traffic and other sources alongside those generated by large cities operating major airports. In this context, the main airport selected in the project is London Heathrow (UK), which was amongst the busiest airports in Europe for arriving and departing passengers in 2012-2014 and is also recognised to be a major source of air pollution in the London area. However, it was of interest to expand the study also to the airport of Venice (Italy), which is located in a European hot-spot, i.e. where the levels of air pollutants are currently breaching most of the target or limit values imposed by European Directives. Experimental. A preliminary review on data available in the literature was carried out to summarise the main information about the topic. Consequently, the CHEERS project was planned as two main strands which were carried out independently at the two selected airports and focused upon: (1) the analysis of fine particulate matter (PM2.5) to quantify the impact of aircraft operations and road traffic upon local air quality; (2) the physical characterization of the aircraft plumes, giving particular attention to particles and their size distributions as an indicator of source and formation mechanisms. Results for Heathrow. A pilot study was conducted in Heathrow by analysing air quality data collected between 2005 and 2012 at 10 sites managed by the UK DEFRA. The pilot study was carried out to quantify the local impacts of the airport ii and to give some preliminary insights into the extent of pollution generated by the airport and motorways. The results of the upper limit assessment study showed that both road traffic and airport emissions are responsible for marked increments upon nitrogen oxide (NO+NO2=NOx) levels: the concentration increment arising from passage of air across the airport during airport activity (6 am-10 pm) is ca. 1-9 μg/m3 of NO2 and 2-20 μg/m3 of NOx at background stations. However, no significant impacts of road and flight traffic on PM concentrations were found. For the project CHEERS, data were collected at Harlington, a site located ~1 km from the airfield. Results of data of strand 1 revealed that the total particle number concentrations (PNC) were ~19.4•103 and ~21.6•103 particles/cm3 in summer (August-September 2014) and winter (December 2014-January 2015), respectively. Data analysis also revealed that the airport is a strong potential source for nucleation particles (14 to 30 nm), while Aitken (30 to 100 nm) and accumulation (0.1 to 1 μm) particles increased for air masses blowing from both the airfield and motorways. On the other hand, road traffic is the main potential source of black carbon (BC), particularly in summer. Concentrations of PM2.5 (strand 2) were 17 and 11 μg/m3 in summer and winter, respectively. Significant differences between summer and winter data were found for most analysed species, i.e. elemental carbon, Na+, NH4+,K+, Cl-, SO42-, oxalate, odd- and even- n-alkanes and many elements (e.g., V, Fe, Zn, As, Cd). Results for Venice. In Venice, samples were collected close (~300 m) to the runway. Results of strand 1 showed that in summer PNC was 13•103 particles/cm3, while concentrations of other pollutants followed the order (in μg/m3): CO (474)> O3 (76)> NOx (53)> NO2 (47)> PM2.5 (16)> NO (3.5)> BC (1.2)> SO2 (0.8). A source apportionment study was performed on wide range particle size spectra and BC. Six potential sources were identified and quantified: photochemical nucleation processes (~40% PNC); pollution linked to diurnal dynamics of the mixing layer and nocturnal condensation of ammonium nitrate (7.2% PNC); road traffic (29% PNC); and airport pollution (19% PNC). Remaining sources were linked to local resuspension and regional/transboundary transport (<3% PNC). Concentrations of PM2.5 (strand 2) were 17 and 11 μg/m3 in summer and winter, respectively. Significant differences between summer and winter data were found for most analysed species, i.e. elemental and organic carbon, Na+, NH4+,K+, Cl-, SO42-, oxalate, odd- and even- n-alkanes and many elements (e.g., V, Fe, Zn, As, Cd). Conclusions. Since the selected airports are located near large cities, their impact upon local air quality cannot be disregarded. As a consequence of this siting, it was also very difficult to differentiate between pollutants arising from airport operations and those from other potential sources in the area. Airport emissions at Heathrow revealed a large influence upon nucleation particles, whereas in Venice the influence was primarily upon particles peaking at 70-80 nm. On the contrary, no a large influence on BC, PM2.5 mass and its chemical composition was detected at either airport.

Data: CORDIS, © European Union