Photometer response determination based on aerosol physical characteristics.

Aerosol photometers often are calibrated against field measurements of total or respirable aerosol concentrations. However, the response of these instruments to a particular aerosol concentration level will change if there is a change in aerosol size distribution. To determine a predictable correction factor that relates photometer to gravimetric measurements of an aerosol, the authors performed an analysis of photometer response relative to particle size distribution, density, and refractive index. A series of trials was performed at different concentration levels using both Arizona road dust and ground corn dust. The correction factor was calculated from a knowledge of the instrument response pattern relative to particle size, as well as the ratios of actual dust density and refractive index relative to that of the dust used to calibrate the instruments. Results demonstrated that the calculated correction factors were within 10% of a correction factor predicted from the slope of a linear regression relating gravimetric measurements to the average of photometer readings taken during the sample period.