Epiphaniometer, a new device for continuous aerosol monitoring

A new device is described, which allows continuous monitoring of aerosols of any kind. Air is continuously pumped through a closed chamber containing short-lived 211Pb atoms delivered by a 227Ac source. These atoms attach onto the aerosol particles. After transportation through a thin capillary to a filter and counting station the particles are detected by means of an α-detector for measuring the decay of 211Pb (via 211Bi). Due to the relatively short half-life of 211Pb, the system allows continuous monitoring of aerosols without changing or transporting the filter. The measured signal is proportional to the exposed Fuchs surface of the aerosol particles. In the case of environmental applications, the device is therefore most sensitive to particles contained in the accumulation mode. Due to its high sensitivity it also works well at the lowest particle concentrations of less than 100 ng m-3 with gas flow rates as low as 1 l min-1.