Significance of Sampling Time in Air Monitoring

Concentrations of six metals in the air of eight cities

“…Although the sampling time does not affect the observed arithmetic mean, it does slightly affect the geometric standard deviation. A study (5) of continuous monitoring data for sulfur dioxide during 1962-1964 showed empirically that the geometric standard deviation varied with the sampling time raised to an exponent which was -0.02 for Chicago, -0.04 for Los Angeles, -0.05 for Washington, DC, -0.07 for Philadelphia, and -0.10 for both Cincinnati and San Francisco. This study theoretically explained some of the complexities of the effects of sampling times on resulting data.…”

Authors’ Reply

“…As specified in the first sentence of our note, 1 the proposed method is designed for assessing the impact of widespread conversion of small combustion sources from oil to coal. Our approach has roots in the empirical work of Larsen 2 and Saltzman 3 and in the use of mass balance implicit in many…”

Comments

“…1 Also, there is evidence that unless special precautions are taken, the aerosol samples may be altered while in storage; e.g., neutralization of acids by ubiquitous ammonia may occur. 3 Adequately sensitive and "nondestructive" methods exist for analysis of all elements typically found in ambient particles, but not for oxygen, and, until recently, not for total carbon either. Recent efforts by Marias 4 and Lewis 5 led to the development of a gamma ray excitation technique by which the on-filter aerosol sample can be analyzed nondestructively for total carbon with acceptable accuracy.…”