A study to monitor UFP at Heathrow Airport was undertaken in the autumn of 2016. The objective was to assess the context of measurements at the airport compared to measurements at “typical” traffic, background and rural locations in the south east of England. Measurements were made at two airport locations at opposite ends of the airfield, to further understand the contribution of the airport to local air quality. Average concentrations at the airport, showed that total particle number concentrations the airport are typically lower than a traffic location and higher than an urban background location in London, matching the trends seen for NOx, PM10, PM2.5 and BC pollutants. However, the size distribution of the submicrometre particles at the airport is completely different to the London monitoring stations, with the airport PSD dominated by particles with a mode of 20nm. In contrast, measurements of PN in London have a significantly larger mode of 30nm.
This study demonstrated that the smallest particles are emitted exclusively from within the airport perimeter and are associated directly with aircraft. Analysis of the operating modes at the airport showed that aircraft departing from the airport emit particles in much higher numbers than those arriving. Nucleation mode particles from the airport are not strongly correlated with Black Carbon, but there does appear to be some correlation with nucleation mode particles and UV active BC (brown carbon) particles at LHR2. There is also modest association between nucleation mode particles and NO2.
The study showed that the classical air pollutants measured at Heathrow are very similar in concentration to typical urban environments in London and south east England, but particle numbers in the sub 30nm size range are markedly different to those measured in London.