||Precision and Accuracy of a Beta Gauge for Aerosol Mass Determinations.
Courtney, William J. ;
Shaw, Robert W. ;
Dzubay, Thomas G. ;
||Northrop Services, Inc., Research Triangle Park, NC.;Environmental Sciences Research Lab., Research Triangle Park, NC.
Air pollution ;
Beta spectrometers ;
Performance evaluation ;
Gravimetric analysis ;
Air filters ;
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Results of an experimental determination of the precision and accuracy of a beta ray attenuation method for measurement of aerosol mass are presented. The instrumental precision for a short term experiment was 25 micrograms for a 6.5 sq cm deposit collected on approximately 1 microgram/sq cm Teflon filters; for a longer term experiment the precision was 27 micrograms. The precision of the gravimetric determinations of aerosol deposits was 22 micrograms for Teflon filters weighted to micrograms. Filter re-orientation and air density changes that were able to adversely affect the beta ray attenuation results are discussed. Beta ray attenuation results are in good agreement with gravimetric measurements on the same filter-collected aerosols. Using dichotomous samplers in Durham, NC, aerosols were collected on Teflon filters in two size ranges. A regression line was calculated implicitly assuming errors in both measurements of mass. The 90% confidence intervals lay within 21 micrograms of the regression line for mean fine fraction aerosol mass loadings of 532 micrograms and within 15 micrograms of the regression line for mean coarse fraction aerosol mass loadings of 392 micrograms.