An Inter-laboratory and Inter-instrumental Comparison of Elemental Loadings on PM2.5 Samples from the Chemical Speciation Network (CSN)
COLLEEN MARCIEL ROSALES, Frank Weber, Tracy Dombek, Nicholas Spada, Nicole Hyslop,
University of California, Davis Abstract Number: 29
Working Group: Instrumentation and Methods
AbstractTo fully understand the health effects of particulate matter (PM), accurate instrumental techniques that describe each component are paramount; however, in the past, studies that compared elemental analysis for PM have identified that there is no “one-size-fits-all” technique that could detect all desired elements, but rather a combination of techniques provided a determination of the elements in PM. At present, the two most commonly used techniques for elemental analyses are energy-dispersive X-ray fluorescence spectroscopy (ED-XRF) and inductively coupled plasma mass spectrometry (ICP-MS). In this study, we aimed to determine which elements are better measured via ED-XRF and/or ICP-MS. We analyzed samples collected from various locations across the United States by the US Environmental Protection Agency (EPA) Chemical Speciation Network (CSN) sampling network, a long-term national monitoring program created in 2000 to support the implementation of the 1997 PM2.5 National Ambient Air Quality Standards (NAAQS). Elemental analysis was done three times on each filter: first, ED-XRF at UC Davis; second, ED-XRF at RTI International, and lastly, ICP-MS at RTI International. We find that some elements, like K, Sr, Zn, Cu, Pb, Ba, and Mg have very good inter-instrument agreement between ED-XRF and ICPMS, while some lighter elements (Na, Mg, and Al) are better measured using ED-XRF. On the other hand, majority of the metallic elements that are present in lower concentrations in PM such as Sb, Pb, V, As, Ag, Fe, Cd, Rb, Ti, Sr, Ce, Zn, Zr, and Cu are better measured with ICP-MS. Lastly, we find that while ICP-MS is better for lower detection limits, accurate determination of soil-related elements such as Ca, Mn, and Ti is highly dependent on the digestion method employed. A combination of well-developed ED-XRF and ICP-MS techniques is necessary to properly quantify the elemental composition of PM collected from urban areas.