STI scientists identified sources of ambient aerosol at an elementary school adjacent to a freeway in Las Vegas, Nevada, by applying the U.S. EPA’s positive matrix factorization tool (EPA PMF) on particles measured with an aerosol mass spectrometer. Using a data set of more than 2 million data points, we identified several local aerosol sources and determined how ambient concentrations vary by time of day and wind direction.
EPA PMF error and diagnostic tools allowed us to easily
  • Evaluate factor stability
  • Resolve factors compared to known source profiles