Vergleichsmessungen zwischen Konimetrie und gravimetrischer Feinstaubprobenahme in Uranerzlagerstätten von Sachsen und Thüringen : Ergebnisse und Folgerungen für eine retrospektive Belastungsabschätzung

In a research project funded by the Hauptverband der gewerblichen Berufsgenossenschaften the dust concentrations in workplaces of former SDAG Wismut mines will be estimated retrospectively. The evaluation is to be performed on a gravimetric base. A large amount of konimetric measurement data for respirable dust is available from the successor company, the Wismut GmbH, beginning in the year 1960. Until the early eighties konimetry was the only measurement procedure applied on a routine base for the grouping of work procedures and job categories respectively. Even until 1990 it was the predominant procedure. Prerequisite for the recalculation of particle number concentrations into gravimetrical respirable dust concentration is the availability of a sufficient statistically sound recalculation function between the two methods. For this purpose a large number of intercomparison experiments between gravimetry and konimetry were performed in underground workplaces of the Wismut GmbH, steadily increasing the number of measurement instruments and the frequency of konimetric samples taken during the measurement intervals in the course of the experiments. Intercomparisons were performed in different lithologies representative for the conditions of uranium mining and under varying ventilation velocities in the range between 0.1 and 2.2 m/s. The preparation and treatment of the konimeter discs before the counting and the counting itself were performed according to the original standards of the former GDR and the requirements of the SDAG Wismut respectively. Nonplausible deviations between two identical konimetric measurements within the same experiment could be recognized and eliminated eventually by use of registrating tyndallometric devices in parallel. This was only done in proven single cases and thus only 64 of the total of 4300 konimetric data (i. e. 1.5%) had to be disregarded. This small number of not included singular data had no consequences for the statistical evaluation. While using all pairs of intercomparison measurements a non-linear regression curve was found to be the most appropriate fit. The correlation factor was found to be r=0.832. For the Thuringian uranium mining district a special recalculation function could be deviated with a regression factor of r=0.96. A further differentiation, for example according to different lithologies, was not possible as the number of measurement pairs was not sufficient to allow for the deduction of a satisfying specific recalculation function between particle number concentration and gravimetric concentration.