There is increasing evidence of potential health impacts from both aircraft noise and aircraft-associated ultrafine particles (UFP). Measurements of noise and UFP are however scarce near airports and so their variability and relationship are not well understood. Particle number size distributions and noise levels were measured at two locations near Gatwick airport (UK) in 2018–19 with the aim to characterize particle number concentrations (PNC) and link PNC sources, especially UFP, with noise. Positive Matrix Factorization was used on particle number size distribution to identify these sources. Mean PNC (7500–12,000 p cm−3) were similar to those measured close to a highly trafficked road in central London. Peak PNC (94,000 p cm−3) were highest at the site closer to the runway. The airport source factor contributed 17% to the PNC at both sites and the concentrations were greatest when the respective sites were downwind of the runway. However, the main source of PNC was associated with traffic emissions. At both sites noise levels were above the recommendations by the WHO (World Health Organisation). Regression models of identified UFP sources and noise suggested that the largest source of noise (LAeq-1hr) above background was associated with sources of fresh traffic and urban UFP depending on the site. Noise and UFP correlations were moderate to low suggesting that UFP are unlikely to be an important confounder in epidemiological studies of aircraft noise and health. Correlations between UFP and noise were affected by meteorological factors, which need to be considered in studies of short-term associations between aircraft noise and health.
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This factor, however, had different characteristics at the two sites. During the Horley campaign this factor had a very small contribution to the total particle number concentration (1%) and was low in concentration (130 p cm −3 ). This factor was moderately correlated with BC 880 and BC 370 and volatile PM 10 , as well as the secondary aerosol factor. Meteorological data showed that the concentration was highest with easterly wind directions. The diurnal profile was predominantly influenced by mixing layer dynamics and thus this factor has also been interpreted as an additional secondary aerosol factor. The highest concentrations coincided with higher wind speeds than for the first secondary aerosol factor and thus this might indicate that the origins were less local. This interpretation was supported by the higher correlation with volatile PM fraction.
This project was funded by the Medical Research Council (MRC; Project Reference MR/P023673/1). We would like to thank Gatwick Airport Ltd (GAL) for providing data on flight numbers and runway direction for the measurement period. The authors would also like to thank Ioar Rivas and Jamie Soussan for their help with data analysis and data collection, respectively.
- Airport emissions
- Particle number size distributions
- SIZE DISTRIBUTIONS
- SOURCE APPORTIONMENT
- Source apportionment
- ULTRAFINE PARTICLES
- Ultrafine particles