Determination of optimal storage conditions for particle samples

Results are presented from laboratory studies on how to store particle samples to preserve them for chemical, physical, and biologic testing. Surrogate samples for power plant plume fly ash were created by using electrostatic precipitator (ESP) hopper ash. Particles of diameters less than 10 mu m were suspended and mixed with three polycyclic aromatic hydrocarbons (PAH), one nitro-PAH, salt, and sulfuric acid. The particle mixture was then collected on filters to create surrogate samples. Samples were stored for periods of 30 and 120 days at either 20 or -79 plus or minus 1 degree C as well as under a set of variable conditions of temperature, light, and humidity. Gas chromatography/mass spectrometry and scanning electron microscopy with energy dispersive analysis were used to characterize changes in organic and elemental composition, particle size distribution, and particle morphology.