Initial Characterization of Fine Particulate Matter (PM_(2.5)) Collected by the National Federal Reference Monitoring Network

摘要

The PM_(2.5) Federal Reference Monitoring (FRM) network was established as part of the implementation of the PM_(2.5) National Ambient Air Quality Standard with monitor deployment beginning in January 1999. The purpose of this report is to provide a characterization of fine particulate matter concentrations measured by the FRM and equivalent methods network for 1999. Data collected between January to December, 1999 were polled from the USEPA Aerometric Information Retrieval System (AIRS). For the purpose of this analysis, data which were fiagged with qualifiers related to laboratory and monitor malfunctions were removed from the data set. Analyses of PM_(2.5) concentrations were performed for selected metropolitan statistical areas (MSAs) and broader predefined regions of the country. The temporal variability of PM_(2.5) concentrations was examined on seasonal timescales. The spatial variability of PM_(2.5) concentrations was examined within several MSAs and on regional scale. Data obtained during 1999 by the PM_(2.5) FRM network were also compared to data obtained in a number of specialized field studies conducted in prior years. The seasonal variability of PM_(2.5) concentrations shows distinct differences in patterns moving from East to West. There is an overall shift in the highest seasonal mean concentrations from the summer to the winter in moving from East to West and are related to differences in source characteristics. Spatial analyses were conducted on data from several MSAs across the country. Some locations showed a linear decrease in the correlation coefficient between sites as the distance between them increases. For many MSAs, however, coefficients of determination between sites remained relatively high (R~2 >=0.7) for distances up to 100 km, supporting the hypothesis that PM_(2.5) is essentially a regional pollutant. A number of other characteristics of the data set will also be presented.