The measurement of PM_(2.5), including semi-volatile components, in the EMPACT program: results from the Salt Lake City Study

摘要

The Salt Lake City EPA Environmental Monitoring for Public Access and Community Tracking (EMPACT) project, initiated in October 1999, is designed to evaluate the usefulness of a newly developed real-time continuous monitor (RAMS) for total (non-volatile plus semi-volatile) PM_(2.5) mass and the health relevance of PM_(2.5) measured by this method as compared to other measurements of PM_(2.5) parameters. Ammonium nitrate and semi-volatile organic compounds (SVOC) are significant components of fine particles in many urban atmospheres. These components however, are not properly measured by current EPA accepted methods, such as the PM_(2.5) FRM, due to loss of semi-volatile material (SVM) from the filter during sampling. Continuous PM_(2.5) mass measurements are attempted using methods such as the R&P TEOM monitor. This method however, heats the sample to remove particle-bound water. This results in evaporation of significant amounts of semi-volatile material. Similarly, continuous carbonaceous material monitors are expected to lose semi-volatile organic material during sample collection. Continuous RAMS and collocated TEOM monitor data have been obtained at the EMPACT sampling site in Salt lake City, Utah during a 2-year period. Results obtained for the continuous determination of total PM_(2.5) mass with the RAMS have been validated by comparison with results obtained from collocated PC-BOSS diffusion denuder integrated samples at the EMPACT sampling site in Salt Lake City, Utah during three intensive sampling periods (winter 1999-2000, summer 2000, and winter 2000-2001). While the RAMS is shown to measure total PM_(2.5), including semi-volatile nitrate and organic material, commercially available semi-continuous TEOM and C monitors do not reliably measure these species.