A new examination of the validity of the principle of beta radiation absorption for determinations of ambient air dust concentrations

Gauges that are based on the principle of β-ray absorption are still the best means of automating measurement of the mass of dust collected on filters in atmospheric pollution. But during the last few years, the validity of this principle has been questioned by contradictory data published in the literature. Within the framework of an EEC research contract, we are giving the results of laboratory examinations of two separate test assemblies of β-ray gauges (14C, 147Pm). The tests carried out include examination of the effect of a number of parameters that affect the quality of the measurement of mass: macroscopic characteristics of particle deposition, multi-element composition, presence phases, heterogeneities on analysis surface, assembly geometry. The results are compared with data found in existing literature. This study has enabled us to optimize the details of the β-gauge of an automatic measurer of sampled dusts on filters that are used to monitor the quality of ambient air, which indexes the samples of fine dust and determines their mass. We present the characteristics and the metrological qualities of this new measurement equipment. (author)