Thermodynamic influences on size fractionated measurements (PM 2.5, PM 10) of ambient aerosols

Abstract

Mass concentrations of PM 10 and PM 2.5 are planned as new standards for the monitoring of ambient air quality in the European Union. Standard procedure is the removal of particles >10 µm and >2.5 µm aerodynamic diameter, respectively, by impaction in a preseparator. Different samplers work according to different principles of flow control. The influence of ambient temperature, pressure and relative humidity on different devices is calculated to estimate the comparability of various aerosol samplers. Therefore, the effects of these ambient factors on the volume flow as well as on the cut-off d_p50 are investigated. In a second step, the influence of relative humidity on the flow control device is calculated. The results show that the cut-off shifts (up to 6.4%) for varying ambient conditions. Therefore, the influence on the impaction process should not be neglected and an ‘ideal sampler’ would measure temperature, pressure and relative humidity and adapt the volume flow to avoid a systematic error in the cut-off.

References

1. Proposal for a Council directive relating to limit values for sulphur dioxide, oxides of nitrogen, particulate matter and lead in ambient air, European Union, 1998.
2. DIN EN 12341 Air quality, Determination of the PM 10 fraction of suspended particulate matter, Reference method and field test procedure to demonstrate reference equivalence of measurement methods; German version EN12341: 1998; Berlin, 03–1999.
3. US EPA 1987, Ambient monitoring reference and equivalent methods, Federal Register 40 CFR Part 53, 1 July 1987.
4. VDI 2066 Part 5, Fraktionierende Staubmessung nach dem Impaktionsverfahren, Kaskadenimpaktor, November 1994, Berlin.
5. T. M. Peters and R. W. Vanderpool, Modification and Evaluation of the WINS Impactor, R.T.I. report No. 6360–011, Sept. 1996.
6. VDI 2066 Part 1, Staubmessungen in stroömenden Gasen; Gravimetrische Bestimmung der Staubbeladung, Übersicht, October 1975, Berlin.
7. P. Profos and T. Pfeifer, Handbuch der industriellen Meβtechnik, Oldenbourg Verlag, 6. Auflage, 1994.
8. LICOR Dew Point Meter, LI 610 Portable Dew Point Generator, Handbook, LICOR, 1991.
9. K. Mennicken, Durchflußmessung aus der Kraft auf angeströmte Körper (Schwebekörper-Durchflußmesser), in Hengstenberg, Messen und Regeln in der chemischen Technik, Berlin, 1964, pp. 366–373.
10. VDI 2463 Part 1, Messen der Massenkonzentration von Partikeln in der Außenluft, Grundlagen, Entwurf, July 1997, Berlin.
11. Installation And Operating Instructions: Brooks Mass flow Controller, Issue 7, Brooks Instrument Division, Hatfield, PA, 08-1989.
12. US EPA 1987, Revisions to the National Ambient Air Quality Standard for Particulate Matter, Federal Register 52 (July 1) 24634–24750.