The Automatic Aerosol Sampler
The automated aerosol sampler installed at Kohnen was constructed in the Institute of Environmental Physics (University of Heidelberg) mainly Dietmar Wagenbach, Susanne Preunkert and Rainer Fletterer. Especially we set a high value on reliable operation of each component down to a temperature of around -50°C. In principle, ambient air was sucked in through a single inlet and was directed to 22 sampling units each consisting of a PFA inline filter holder, a one-way inlet and outlet valve and a miniature vacuum pump. The 22 pumps were activated consecutively for a specified constant sampling time of 360 hours (15 days). This procedure greatly reduced the risk a total system breakdown by failure of a single central pump. For the central flow meter we used a microprocessor-controlled vane wheel sensor and from January 2005 on a mass flow meter.
There is a potential danger of passive sampling because of the long standing time of the aerosol filters. To minimize this effect, we avoided permanent contact of the filters with ambient air by isolating each filter with two tube squeezing magnetic valves. Because of occasional malfunction, we replaced these valves in January 2005 and installed two custom-made 22-way PFA valves driven by an electric motor equipped with a reduction gearing.
A programmable data logger controlled of the procedure cycle. The data logger was powered by autonomous Li-SO2 primary cells to ensure functioning even during main power outage, which was of vital importance for the whole procedure.
Diagram of the technical layout of the automated aerosol sampler installed at EDML (Kohnen Station). Abbreviations: P, carbon vane pumps (22); EF, exhaust filter; FH, filter holders (22); FM, flow meter; IV, inlet valves (22); OV outlet valves (22).