ECN publication
Development of instrumentation for the measurement of atmosphericconcentrations of acidifying compounds
Published by: Publication date:
ECN 1996
ECN report number: Document type:
ECN-C--96-039 ECN publication
Number of pages: Full text:
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Several novel techniques have been developed for sampling and detectionof atmospheric trace constituents. A diffusion denuder is described for the continuous measurement of atmospheric ammonia. This compact instrument is fully automated and suited for routine deployment in field studies. The precision is sufficiently high for micrometeorological studies of air-surface exchange of ammonia. A new principle of sampling aerosol particles by means of steam injection with the consequent collection of grown droplets has been established. On the basis of the new sampling principle a prototype of an aerosol sampler was designed which is capable of sampling particles quantitatively down to several nanometers in diameter. During measurements the sampler proved to be stable, working without any assistance for extended periods of time. Comparison of the sampler with filter packs during measurements of ambient-air aerosols showed that the sampler gives good results. An automated system has been developed for the collection, in-line preconcentration and analysis of acidifying atmospheric gases. Collection of HCl, HNO2, HNO3 and SO2 from ambient air is carried out with a wet annular denuder. The manifold described with two sample loops and two concentrator columns operating in parallel allows automated collection and analysis of two air samples per hour. A computer programme has been developed for automated performance. It allows the system to run unattendedly during extended periods as all the functions, including data processing, are computer-controlled. Factors affecting the performance are reported. Ambient measurements for Petten, The Netherlands, are presented which show the capability of the system for continuous monitoring of atmospheric acidifying gases. A simplified Seld instrument for the continuous measurement of HCl, HNO2, HNO3 and SO2 was constructed, which is based on the same principles as the apparatus described above. The applicability of the system is demonstrated in a measurement campaign at Petten, The Netherlands. 23 figs., 3 tabs., 39 refs.

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