Abstract |
A cascade impactor network operating from 1970 through 1972 at eight urban and two nonurban sites indicated that the median size of airborne particles on a mass basis appeared to increase over the sampling period. Quarterly variations in the median size were associated with seasonal changes, decreasing in summer but increasing in winter. The general upward trend in the size of airborne particles appeared to be associated with the reduction in automotive emissions that can lead to the formation of fine, secondary aerosols. Other possible explanations, however, were examined in addition to an evaluation of the limitations of the cascade impactor used in the network. |