PM2.5 Chemical Speciation Network and Its Challenges
Jayanty, R. K., Gutknecht, W. F., Greene, L. C., Hardison, E. D., Peterson, M. R., O'Rourke, J. A., ... Homolya, J. B. (2002). PM2.5 Chemical Speciation Network and Its Challenges. In .
Particulate matter (PM) with particle aerodynamic diameters of 2.5 Fm and smaller (PM2.5) in ambient air has been associated with respiratory and other health-related problems in addition to contributing to atmospheric visibility impairment and regional haze. Negative health effects have been statistically correlated to total mass concentration (Fg/m3) of PM2.5 in ambient air, but whether the correlation is actually to total mass concentration or to concentrations of specific chemical species comprising PM2.5 has not yet been determined.On July 18, 1997, the U. S. Environmental Protection Agency (EPA) promulgated the new National Ambient Air Quality Standards (NAAQS) for PM. The NAAQS apply to the mass concentration of particles with aerodynamic diameters lower than 2.5 Fm (PM2.5) and 10 Fm (PM10). The deployment of a new PM2.5 monitoring network by EPA is a critical component in the national implementation of the PM2.5 NAAQS. The compliance (mass) monitoring portion of the network was established first. Data from the compliance network is used to determine attainment with the NAAQS. EPA soon supplemented the network with a chemical speciation monitoring program to provide complementary data on the chemical composition of PM2.5 for the purposes of identifying sources, developing implementation plans, and supporting ongoing health effects research. RTI has been given the responsibility of assisting State and local agencies in the operation of PM2.5 chemical speciation monitoring networks by providing filter media and analytical support for the analysis of air filters for gravimetric mass, elemental concentrations (sodium through lead), organic and elemental carbon, anions (ammonium, sodium, and potassium) and cations (sulfate and nitrate), and analysis of semivolatile organics and microscopic analysis of selected filters. The program has grown significantly over the last three years and currently RTI is providing chemical speciation support to over 225 PM2.5 monitoring sites established throughout the United States and Puerto Rico.Several challenges encountered in the operation of this program include sample handling, high blank levels for gravimetric mass on Teflon filters, high background levels for quartz and nylon filters, data validation, and reporting. For example, RTI has shown that the outgassing from the white Delrin® rings originally used in the MetOne sampler are a cause of high blank levels for the gravimetric mass on Teflon® filters. Subsequent, research performed at EPA/Montgomery confirmed RTI’s findings. Other challenges and their solutions implemented in the nationwide network, as well as a general overview of the PM2.5 Chemical Speciation Program, will be presented.