Aircraft Arrival and Departure Contributions to Ultrafine Particle Size Distribution in a Near-Airport Community

Determining aviation-related contributions to ambient ultrafine particle (UFP) concentrations in complex, multisource environments is challenging; source-specific differences in particle size distribution may provide a mechanism for source attribution. We examined UFP concentrations and size distribution across 32 particle diameters at a monitoring site in close proximity to Boston Logan International Airport across a two-year period, incorporating covariates for flight activity and meteorology. Total particle number concentration (PNC) was ∼2-fold higher when the site was downwind of the airport. During these wind conditions, particles between 8 and 12 nm in diameter comprised the largest proportion of overall PNC observed, consistent with aircraft contributions. Particle size distribution differed substantially between hours of predominant aircraft arrivals (peak modal diameter 9-11 nm) versus departures (peak modal diameter 39-52 nm). Peak concentrations of particles between 9 and 11 nm were found in the winter and during afternoon hours. We conducted a principal component analysis (PCA) to confirm particle size distributions from aviation activity. PCA results showed that nucleation-mode particles (<30 nm in diameter), specifically those between 9 and 11 nm, were associated with landing aircraft on a nearby runway, especially when the monitor was downwind of the airport. Our findings confirm that aviation-specific UFP emissions are dominated by nucleation mode particles, with long-term size distribution information able to distinguish between aircraft operations in near-airport communities.