Emissions from aircraft operations can substantially increase concentrations of several pollutants in communities near airports, especially ultrafine particles (UFP), which have also been suggested to impact air quality up to several kilometers (km) downwind. Aircraft engines are tested for emissions of several pollutants, but none of the tests are specifically aimed at UFP. Here, data from two airports, Santa Monica Airport (SMO) and Los Angeles Insertional Airport (LAX) were analyzed to determine aircraft contribution to UFP concentrations at sites downwind of the two airports, respectively. At SMO, peak UFP concentrations associated with individual takeoff and landing operations were analyzed. A single variable linear regression was run separately for aircraft engine emission rates and takeoff and landing UFP peak concentrations to determine which, if any, parameters are predictive for UFP. Parameters included nitrogen oxides [NOx], carbon monoxide [CO], hydrocarbons [HC], smoke number [SN], and engine thrust identified in the International Civil Aviation Organization (ICAO) database. Data from the Los Angeles World Airports Air Quality and Source Apportionment Study were analyzed for relationships between particle concentration and wind direction, time of data, and aircraft. Additionally, contribution from arrival and departures by runway (24 and 25), arrivals compared to departures, and diurnal UFP concentrations is determined.

For SMO, we were able to assign specific peak UFP concentrations for both takeoff and landing operations with takeoff peaks significantly higher than landing. Using single variable linear regressions analysis showed using ICAO database parameters to predict UFP peak measurements is best made by using thrust (kN) and NOx. For LAX, multiple lines of evidence indicate aircraft landing operations are the primary contributor to UFP concentrations < 30 nm at two sites between 1,600 and 2,000 m downwind of LAX. Sub-30 nm UFP are highly elevated when the sites are downwind of arrival operations on one or both runways. Of the aircraft operation influence at the two sites, UFP concentrations < 30 nm are found to be primarily from arrivals on Runways 24 and 25. For the multivariate linear regression results, arrivals were significant when the two sites were downwind of the airport while departures were not.