Routine Microscopic Examination of Dust Deposition.

From 1962 until 1977 weekly dust deposition samples were taken at Freiburg i. Br. using dust deposition plates. The plates were evaluated continuously by gravimetric and microscopic methods. As a typical anthropogenic component, combustion products were observed and counted under the microscope. Microscopic evaluation reveals therefore valuable data. Simultaneous dust deposition measurements with the Bergerhoff instrument showed that lower dust weights obtained by deposition plates were not only caused by losses of deposited matter by precipitation but also by a lowered sampling efficiency for very coarse dust components. The results of both methods agree much better, when a roof was used to protect the deposition plates against precipitation. For the purpose of particle measurements in health resorts by the Deutscher Wetterdienst the properties of dust deposition plates and the evaluation methods have been further improved in the last years.