Significance of Sampling Time in Air Monitoring

Abstract

More efficient air sampling programs can be designed, and clearer interpretations of their data made, if important theoretical aspects are clearly understood. The choice of a sampling time is an important decision affecting the results. Empirical and theoretical calculations show that the averaging effect of sampling time attenuates responses to short period fluctuations in pollutant concentrations. Data for sulfur dioxide concentrations in six cities are examined. The body acts as a sampling mechanism also, and concentrations inside the body fluctuate less than those outside. These damping processes are quantitatively described. A significant biological parameter is the product of the biological half-life of a pollutant and the fraction of entrance to total resistance for its passage through the body. When sampling time is four times this parameter, attenuation of significant fluctuations is about the same in both samples and the body; when it is twice the parameter, the “sampling window” transmits all significant fluctuations better than the “biological window.” Shorter sampling periods appear to give unnecessary fine detail for biological application according to this theoretical model.