title: Contributions of aircraft arrivals and departures to ultrafine particle counts near Los Angeles International Airport.
abstract: BACKGROUND
  While commercial aircraft are known sources of ultrafine particulate matter (UFP), the relationship between airport activity and local real-time UFP concentrations has not been quantified. Understanding these associations will facilitate interpretation of the exposure and health risk implications of UFP related to aviation emissions.
  
  
  OBJECTIVE
  We used time-resolved UFP data along with flight activity and meteorological information to determine the contributions of aircraft departures and arrivals to UFP concentrations.
  
  
  METHODS
  Aircraft flight activity and near-field continuous UFP concentrations (≧ 6 nm) were measured at five monitoring sites over a 42-day field campaign at Los Angeles International Airport (LAX). We developed regression models of UFP concentrations as a function of time-lagged landing and take-off operations (LTO) activity, in the form of arrivals or departures weighted by engine-specific estimates of fuel consumption.
  
  
  RESULTS
  Our regression models demonstrate a strong association between departures and elevated total UFP concentrations at the end of the departure runway, with diminishing magnitude and time-lagged impacts with distance from the source. LTO activity contributed a median (95th, 99th percentile) UFP concentration of approximately 150,000 particles/cm(3) (2,000,000, 7,100,000) at a monitor at the end of the departure runway, versus 19,000 particles/cm(3) (80,000, 140,000), and 17,000 particles/cm(3) (50,000, 72,000) for monitors 250 m and 500 m further downwind, respectively.
  
  
  CONCLUSIONS
  We demonstrated significant contributions from aircraft departure activities to UFP concentrations in close proximity to departure runways, with evidence of rapid plume evolution in the near field. Our methods can inform source attribution and interpretation of dispersion modeling outputs.
authors.affiliation: Department of Environmental Health, Harvard School of Public Health, Boston, MA, USA. leonhsu@mail.harvard.edu
authors.forename: Hsiao-Hsien
authors.initials: HH
authors.lastname: Hsu
authors.forename: Gary
authors.initials: G
authors.lastname: Adamkiewicz
authors.forename: E Andres
authors.initials: EA
authors.lastname: Houseman
authors.forename: Darcy
authors.initials: D
authors.lastname: Zarubiak
authors.forename: John D
authors.initials: JD
authors.lastname: Spengler
authors.forename: Jonathan I
authors.initials: JI
authors.lastname: Levy
mesh_terms: D000393:Air Pollutants / Q000032:analysis*; D000401:Aircraft; D059028:Airports; D004784:Environmental Monitoring / Q000379:methods*; D015141:Los Angeles; D052638:Particulate Matter / Q000032:analysis*; D012044:Regression Analysis
chemical_list: D000393:Air Pollutants; D052638:Particulate Matter