COMPARISON OF 3 METHODS OF PARTICULATE MEASUREMENT IN CHICAGO AIR

Simultaneous measurements of suspended particulate concentrations were taken in Chicago over an 8-month period with an integrating nephelometer, a 6-stage fractionating sampler, and a Hi-Vol air sampler. The correlation coefficient (r) between light scattering coefficient, bscat, and the Hi-Vol measurements was 0.75. The light scattering coefficient was found to be highly correlated with the impactor stages which had cut-off diameters of 0.38 μm (r = 0.79) and 0.84 μm (r = 0.89). These associations were independent of relative humidity. In contrast, correlations between bscat and all other size fractions, and with TSP, were greatly affected by relative humidity. Relatively strong relationships were also found between NO2, O3 and bscat which support the contention that nephelometer measurements are a reflection of photochemical activity. © 1979.