Methodology for Chemical Speciation Measurements in the IMPROVE Network

Eldred, Robert

The IMPROVE (Interagency Monitoring of Protected Visual Environments) network collects PM2.5 particles on Teflon, nylon, and quartz filters using a modular, cyclone-based sampler with critical orifice flow control. Understanding the protocols of IMPROVE is important because IMPROVE will continue to provide background monitoring at Class I areas, and because the protocols for measuring chemical species in the Federal Reference Method network at urban and suburban sites will probably be similar. The IMPROVE filters are analyzed by seven methods to obtain concentrations of mass, elements H and Na-Pb, ions NO3- and SO4=, organic and elemental carbon, and the coefficient of absorption. The replicate precision for most analytical methods is approximately 4%. The artifacts for all methods except carbon are small or zero. The artifact problem for organic carbon is minimized by allowing each filter to reach saturation prior to collection. Redundant measurements by the three filters permit improved quality control. Comparisons of sulfur with sulfate and organic carbon with organic hydrogen permit assurance that (1) the calculated uncertainties are reasonable, (2) the analytical methods are correctly calibrated, (3) the flow rates of the various modules are in agreement, and (4) the individual concentrations are valid.