Abstract for presentation at 14th IUAPPA World Congress

This paper compares PM_2.5 chemical speciation results obtained by three laboratories that have supported sampling and analysis for the State of Texas – Desert Research Institute (DRI), RTI International (RTI), and the University of California Davis (UCD). RTI is the USEPA contractor laboratory for its national Speciation Trends Network (STN) and analyzed all Texas' STN samples from 2000 through October 2004. DRI is the PM_2.5 Federal Reference Method/Federal Equivalent Method (FRM/FEM) contractor for the State of Texas and assumed responsibility for the chemical speciation analysis and support of Texas’ 20 PM_2.5 supplemental speciation sites in November 2004 (core network sites remained with RTI). UCD is the contractor for the National Park Service's IMPROVE program which has two long-term sites in Texas and one tempory intercomparison site at Houston Deer Park.
The intercomparison includes results from four general sources: (1) a test bed site in Austin used to assess collocated precision of the supplemental speciation measurements, comparability of chemical speciation results between DRI and RTI, and the suitability of using different filters and analysis methods; (2) collocated speciation results at Big Bend between the Texas supplemental samplers and the IMPROVE samplers; (3) collocated STN speciation samplers at Deer Park and temporarily collocated IMPROVE samplers; and (4) inter-laboratory comparisons from EPA's chemical speciation QA program and less formal comparisons.
Issues include potential offsets (biases) between laboratories, reported analytical sensitivity and uncertainty, precision, and data validation conventions.