New Capability for In Situ Measurements of Particulate Matter Using Size-Selecting Nephelometers as Part of the SPARTAN Network.

The expanding SPARTAN ground network currently monitors particulate pollutants at 25 sites around the globe. The backbone of the SPARTAN measuring system is a suite of coordinated instruments that collect particles on filters for laboratory mass and composition analysis while a sensitive nephelometer provides a simultaneous time series of high temporal resolution light scattering measurements. The SPARTAN nephelometer (AirPhoton IN102) measures forward and backscatter independently at three wavelengths, and at time intervals of less than a minute. In addition, through a patent pending process, the instrument varies the cutoff size of the particles entering the optical chamber through automatic feedback to a variable flow fan that regulates the speed of the flow. In this way the nephelometer measures various particle size ranges between PM2.5 and PM10 on the order of 10 minutes. This provides an array of spectral, angular and size characterization of the particle scattering that can be used to constrain particle type. Time series from selected individual instruments and preliminary interpretation of the data will be presented. The SPARTAN configuration that combines these high temporal resolution constraints on aerosol type, coupled with the longer term detailed characterization of particle properties from laboratory analysis supports SPARTAN's goals of characterizing harmful particulate pollution to exposed populations and providing the data base from which to develop and test satellite-based methods to continue that characterization and monitoring.