Immission rate measuring apparatus

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The immission rate measuring apparatus ( IRMA , initially referred to as immission rate measuring device and immission rate measuring system ) is a sampling device for recording the deposition rate (deposition current density) of atmospheric substances on a vertical, cylindrical liquid surface. The IRMA was founded in the early 1970s under the direction of Dr. Siegbert Luckat in what was then the State Institute for Immission and Land Use Protection (LIB) of the State of North Rhine-Westphalia in Essen . The structure of the IRMA and a measurement method in which it is used was first published in 1972. In 1975 the LIB was granted a patent through the IRMA. There are three VDI guidelines in which the IRMA procedure, i.e. the procedure for determining deposition rates using the IRMA, is described: VDI 3794 Part 1 (2010), VDI 3794 Part 2 (2013) and VDI 3794 Part 3 (2009 ).

functionality

construction

The IRMA consists of a device base and an attachment. In the devices that have been commercially available up to now, the base contains a one-liter storage bottle, a peristaltic pump and a battery compartment for two mono cells . In-house built devices for research purposes are partly equipped with maintenance-free diaphragm pumps , with external power supply and with operating hours counters. The IRMA attachment consists of a funnel and a top plate, which are connected to one another with three rods. The so-called carrier body of the IRMA is mounted in this attachment. This is an extraction or Soxhlet sleeve that is attached to a flat cylinder, which in turn is screwed into the top plate of the attachment. In this way the sleeve hangs upright (ie with the round bottom down) over the funnel and between the three rods. This arrangement means that the wind can flow onto the carrier body from all directions almost unhindered. To operate the IRMA, the storage bottle is filled with a special liquid ( absorption liquid ) that is suitable for absorbing the atmospheric substances in question . The pump conveys this liquid into the paper felt of the carrier body, which it soaks and wets. In this way, a liquid film is created on the outer surface of the carrier body. The absorption liquid runs down in and on the carrier body and drips from its lower end through the funnel back into the storage bottle.

Sampling principle

For measurements in the open air, the IRMA is operated at a height of approx. 1.4 meters above the ground in a specially constructed, covered frame. Gases, solid particles and droplets from the surrounding air can now be deposited (deposited) on the liquid surface of the carrier body through diffusion and impaction . With the IRMA, the part of the dry and wet deposition is recorded that is caused by a horizontal movement component that is not caused by gravity. In this way, the absorption liquid is gradually enriched with substances absorbed from the air. Depending on the substances of which the deposition rate is to be determined, different absorption solutions are used in the IRMA. In the specialist literature, measuring methods with IRMA for determining the deposition rate of the sum of ammonia and ammonium compounds (NHx), of atmospheric fluorides , chlorides and sulfur oxides (SOx) and of atmospheric nitrogen oxides (NOy) are described.

Sample analysis and evaluation

During the sampling, a number of substances from the atmospheric air have accumulated in the IRMA absorption liquid. Not all of these substances are of interest for the measurement purpose. Therefore, after the sampling, only the quantities of some appropriately selected substances are determined using chemical-analytical methods . The respective accumulated amounts of substance in relation to the area of ​​the IRMA liquid film and the duration of the sampling are given as the measurement result. This gives the deposition current density (identical to: deposition rate, immission rate, immission current density) of the substance, usually given as the mass of substance per square meter and day.

Statement of the deposition rates determined with IRMA

In terms of its deposition resistance, the liquid surface used in the IRMA process does not necessarily correspond to a real surface at the measurement location, but only simulates a few selected properties of such real surfaces ( environmental simulation ). The surface resistance of the IRMA liquid film is mainly determined by the chemical properties of the absorption liquid used. The shape of the IRMA carrier body and the physical surface properties of the liquid significantly influence the aerodynamic (turbulent) resistance and the (quasi-laminar) resistance of the air boundary layer above the liquid film. Since these properties are uniform if the IRMAs used are operated in the same way and with the same type of liquid, the total deposition resistance is only varied by the atmospheric conditions at the measurement location during the measurement period, in particular by the wind speed . The deposition rates determined in this way are therefore related to the selected IRMA method, but comparable measured values ​​of a mean atmospheric state at a measuring location and in a measuring period over time and place.

Together with the data obtained using the Mankschem carousel , IRMA data can be used to create an impact register - a supplementary information system to the emissions and immission register.

Literature and Sources

  1. ↑ a b c Luckat, S. (1980): About the Immissions-Raten-Mess-Anlage. Dust - keeping the air clean, Vol. 40, pp. 425–427.
  2. ↑ a b c Luckat, S. (1972): A method for determining the immission rate of gaseous components. Dust - keeping the air clean, Vol. 32, pp. 484–486.
  3. ↑ German Patent Office: Patent 22 25 889 . Retrieved March 12, 2013.
  4. ↑ a b VDI 3794 sheet 1: Determination of immission rates - Determination of the immission rates for atmospheric fluorides, chlorides and sulfur oxides (SO x ) using the IRMA method. VDI / DIN manual for keeping the air clean, Volume 1, Berlin. First edition 1982, latest edition 2010.
    VDI 3794 Part 2: Determination of immission rates - Determination of the immission rate of ammonia and ammonium compounds using the IRMA method. VDI / DIN manual for keeping the air clean, Volume 1, Berlin. First edition 2003, latest edition 2013.
    VDI 3794 Part 3: Determination of immission rates - Determination of the immission rate of atmospheric nitrogen oxides (NO y ) using the IRMA method. VDI / DIN manual for keeping the air clean, Volume 1, Berlin. First and most recent edition 2009.
  5. ↑ a b Fiedler, J. (2005): Recording of nitrogen dioxide immission rates with the passive collector IRMA. Dissertation, Humboldt University Berlin, Institute of Geography.
  6. ↑ a b Schwela, D .; Radermacher, L. & Specovius, J. (1988): Dependence of SO 2 integrated exposure rates on SO 2 concentration, wind velocity, temperature, and relative humidity. Water, Air and Soil Pollution, Vol. 40, pp. 261-274.
  7. ↑ Entry on deposition velocity . In: IUPAC Compendium of Chemical Terminology (the “Gold Book”) . doi : 10.1351 / goldbook.D01602 Version: 2.3.3.
  8. ↑ Möller, D. (2003): Air - chemistry, physics, biology, cleanliness, law. Berlin, New York.
  9. ^ Prinz, B. & Stratmann, H. (1969): Proposals for definitions in the field of air pollution control. Dust - keeping the air clean, vol. 29, pp. 354–357.
  10. ↑ Entry on immission flux . In: IUPAC Compendium of Chemical Terminology (the “Gold Book”) . doi : 10.1351 / goldbook.I02969 Version: 2.3.3.
  11. ↑ DIN ISO 4225: Air quality - General aspects - Terms (ISO 4225: 1994). VDI / DIN manual for keeping the air clean, Volume 5, Berlin.
  12. ↑ Bach, R.-W. & Stratmann, H. (1983): Investigations to determine the absorption rate of the IRMA device with different flow conditions. LIS reports, No. 37, Essen.
  13. ^ Franz Joseph Dreyhaupt (ed.): VDI-Lexikon Umwelttechnik. VDI-Verlag Düsseldorf 1994, ISBN 3-18-400891-6 , p. 791.