The Mobile Observations of Ultrafine Particles (MOV-UP) Study: Winter 2018 Sampling

Abstract

The Mobile ObserVations of Ultrafine Particles (MOV-UP) Study is a two-year project intended to quantify air quality impacts of air traffic for communities located near, and below the flight paths of the SeaTac airport. The study aims to assess ultrafine particle concentrations within 10 miles of the airport in the directions of aircraft take-offs and landings over the course of 4 seasons. To date, sampling has been completed for Winter 2018. Over this time period, 16 days of mobile sampling were conducted using a suite of mobile instruments capable of detecting particles between 10-20, 20-36 and >36 nm in diameter on a 10 second time-scale. Black carbon (BC) particle concentration was collected on the 10 second scale as well as the full range of particle size distribution from 10 nm to 1 µm on the 1 minute time scale. The mean wind direction during the drives was from the SW. There were two days with wind from the NW, which resulted in reversal of the landing and take-off direction at the airport. A varimax rotated principal component analysis was performed on the 1 minute particle size distribution data and BC concentration, normalized to total particle count. Three components accounted for 74% of the variance observed. The first component, explaining 33% of the variance, shows high loadings of particles with median diameter of less than 20.5 nm. The second component, explaining 23% of the variance, shows high loadings of particles with median diameter of greater than 20.5 nm. The third component, explaining 18% of the variance, shows high proportion of black carbon. The geographic distribution of the component scores suggests that the first component is associated with the aircraft flight path. This study demonstrates the ability of mobile monitoring to detect variations in on-road particle size distribution that may be associated not only with vehicular traffic, but also with distance to flight path within 10 miles of an urban airport.