Abstract

A novel instrument that is capable of taking spectral extinction measurements over long optical paths (approximately 1–100 m) in the UV, visible, and IR ranges is described. The instrument is fully automated, and the extinction spectrum is acquired in almost real time (approximately 5–10 s) with a resolution of ∼3 nm. Its sensitivity and accuracy were estimated by tests carried out in a clean room that showed that, for optical paths between 50 and 100 m, the extinction coefficient can be detected at levels of ∼10-5 m-1. Tests carried out on calibrated latex particles showed that, when it was combined with an appropriate inversion method, the technique could be profitably applied to characterize airborne particulate distributions. By carrying out measurements over optical paths of ∼100 m, the instrument is also capable of detecting extinction coefficients that are due to aerosol concentrations well below the limits imposed by the European Economic Community for atmospheric pollution (150 µg/m3). Scaled over optical paths of ∼10 m, the limit imposed for particle emissions from industrial plants (10 mg/m3) can also be detected sensitively.

© 2001 Optical Society of America

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References

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  1. G. Kasper, J. H. Vincent, eds., “Abstracts of the 5th International Aerosol Conference 1998,” J. Aerosol Sci. 29, S295–S318 (1998).
  2. R. M. Harrison, R. E. van Grieken, eds., Atmospheric Particles (Wiley, New York, 1998).
  3. C. F. Bohren, D. R. Huffman, Absorption and Scattering of Light by Small Particles (Wiley, New York, 1983).
  4. G. Yamamoto, M. Tanaka, “Determination of aerosol size distribution from spectral attenuation measurements,” Appl. Opt. 8, 447–453 (1968).
    [CrossRef]
  5. E. Trakhovsky, S. G. Lipson, A. D. Devir, “Atmospheric aerosols investigated by inversion of experimental transmittance data,” Appl. Opt. 21, 3005–3010 (1982).
    [CrossRef] [PubMed]
  6. H. Grassl, “Determination of aerosol size distributions from spectral attenuation measurements,” Appl. Opt. 10, 2534–2538 (1971).
    [CrossRef] [PubMed]
  7. R. Hitzenberger, R. Rizzi, “Retrieved and measured aerosol mass size distributions: a comparison,” Appl. Opt. 25, 546–553 (1986).
    [CrossRef] [PubMed]
  8. M. D. King, D. M. Byrne, B. M. Herman, J. A. Reagan, “Aerosol size distributions obtained by inversion of spectral optical depth measurements,” J. Atmos. Sci. 35, 2153–2167 (1978).
    [CrossRef]
  9. E. E. Uthe, “Particle size evaluations using multiwavelength extinction measurements,” Appl. Opt. 21, 454–459 (1982).
    [CrossRef] [PubMed]
  10. G. Ramachandran, D. Leith, L. Todd, “Extraction of spatial aerosol distributions from multispectral light extinction measurements with computed tomography,” J. Opt. Soc. Am. A 11, 144–154 (1994).
    [CrossRef]
  11. K. Rajeev, K. Parameswaran, “Iterative method for the inversion of multiwavelength lidar signals to determine aerosol size distribution,” Appl. Opt. 37, 4690–4700 (1998).
    [CrossRef]
  12. F. Ferri, A. Bassini, E. Paganini, “Modified version of Chahine algorithm to invert spectral extinction data for particle sizing,” Appl. Opt. 34, 5829–5839 (1995).
    [CrossRef] [PubMed]
  13. F. Ferri, A. Bassini, E. Paganini, “Commercial spectrophotometer for particle sizing,” Appl. Opt. 36, 885–891 (1997).
    [CrossRef] [PubMed]
  14. W. L. Wolfe, G. J. Zissis, eds., The Infrared Handbook (Environmental Research Institute of Michigan, Ann Arbor, Mich., 1989), p. 111.
  15. W. Restani, R. Mari, Tutela dell’Ambiente Atmosferico (Pirola, Milan, Italy, 1995), Chap. 3.
  16. C. van de Hulst, Light Scattering by Small Particles (Dover, New York, 1981), p. 127 and 388.
  17. S. Twomey, Introduction to the Mathematics of Inversion in Remote Sensing and Indirect Measurements (Elsevier, Amsterdam, 1977).
  18. A. Deepak, M. A. Box, “Forward scattering corrections for optical extinction measurements in aerosol media. 1. Monodispersions,” Appl. Opt. 17, 2900–2908 (2000).
    [CrossRef]
  19. A. Deepak, M. A. Box, “Forward scattering corrections for optical extinction measurements in aerosol media. 2. Polydispersions,” Appl. Opt. 17, 3169–3176 (1978).
    [CrossRef] [PubMed]
  20. G. Zaccanti, P. Bruscaglioni, “Deviation from the Lambert–Beer law in the transmittance of a light beam through diffusing media: experimental results,” J. Mod. Opt. 35, 229–242 (1988).
    [CrossRef]
  21. J. Heintzenberg, H. Muller, H. Quenzel, E. Thomalla, “Information content of optical data with respect to aerosol properties: numerical studies with a randomized minimization-search-technique inversion algorithm,” Appl. Opt. 20, 1308–1315 (1981).
    [CrossRef] [PubMed]
  22. C. E. Junge, Air Chemistry and Radioactivity (Academic, New York, 1963).
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    [CrossRef]
  24. K. T. Whitby, “The physical characteristics of sulfur aerosols,” Atmos. Environ. 12, 135–139 (1978).
    [CrossRef]
  25. C. T. Lee, J. J. Tsai, “Aerosol light-scattering coefficient and size distributions in a suburban area in Taiwan,” J. Aerosol Sci. 29, S651–S652 (1998).
    [CrossRef]
  26. M. Born, E. Wolf, Principles of Optics (Pergmon, New York, 1959), p. 94.
  27. D. D. McRae, “The refractive index of individual cigarette smoke droplets,” J. Colloid Interface Sci. 87, 117–123 (1982).
    [CrossRef]
  28. M. Kerker, M. J. Sculley, W. A. Farone, A. J. Kassman, “Optical properties of cigarette smoke aerosols,” Appl. Opt. 17, 3030–3031 (1978).
    [CrossRef] [PubMed]
  29. I. P. Chung, D. Dunn-Rankin, “In situ light scattering measurements of mainstream and sidestream cigarette smoke,” Aerosol Sci. Technol. 24, 85–101 (1996).
    [CrossRef]

2000 (1)

1998 (3)

G. Kasper, J. H. Vincent, eds., “Abstracts of the 5th International Aerosol Conference 1998,” J. Aerosol Sci. 29, S295–S318 (1998).

C. T. Lee, J. J. Tsai, “Aerosol light-scattering coefficient and size distributions in a suburban area in Taiwan,” J. Aerosol Sci. 29, S651–S652 (1998).
[CrossRef]

K. Rajeev, K. Parameswaran, “Iterative method for the inversion of multiwavelength lidar signals to determine aerosol size distribution,” Appl. Opt. 37, 4690–4700 (1998).
[CrossRef]

1997 (1)

1996 (1)

I. P. Chung, D. Dunn-Rankin, “In situ light scattering measurements of mainstream and sidestream cigarette smoke,” Aerosol Sci. Technol. 24, 85–101 (1996).
[CrossRef]

1995 (1)

1994 (1)

1992 (1)

G. Ramachandran, D. Leith, “Extraction of aerosol-size distributions from multispectral light extinction data,” Aerosol Sci. Technol. 17, 303–325 (1992).
[CrossRef]

1988 (1)

G. Zaccanti, P. Bruscaglioni, “Deviation from the Lambert–Beer law in the transmittance of a light beam through diffusing media: experimental results,” J. Mod. Opt. 35, 229–242 (1988).
[CrossRef]

1986 (1)

1982 (3)

1981 (1)

1978 (4)

A. Deepak, M. A. Box, “Forward scattering corrections for optical extinction measurements in aerosol media. 2. Polydispersions,” Appl. Opt. 17, 3169–3176 (1978).
[CrossRef] [PubMed]

K. T. Whitby, “The physical characteristics of sulfur aerosols,” Atmos. Environ. 12, 135–139 (1978).
[CrossRef]

M. D. King, D. M. Byrne, B. M. Herman, J. A. Reagan, “Aerosol size distributions obtained by inversion of spectral optical depth measurements,” J. Atmos. Sci. 35, 2153–2167 (1978).
[CrossRef]

M. Kerker, M. J. Sculley, W. A. Farone, A. J. Kassman, “Optical properties of cigarette smoke aerosols,” Appl. Opt. 17, 3030–3031 (1978).
[CrossRef] [PubMed]

1971 (1)

1968 (1)

Bassini, A.

Bohren, C. F.

C. F. Bohren, D. R. Huffman, Absorption and Scattering of Light by Small Particles (Wiley, New York, 1983).

Born, M.

M. Born, E. Wolf, Principles of Optics (Pergmon, New York, 1959), p. 94.

Box, M. A.

Bruscaglioni, P.

G. Zaccanti, P. Bruscaglioni, “Deviation from the Lambert–Beer law in the transmittance of a light beam through diffusing media: experimental results,” J. Mod. Opt. 35, 229–242 (1988).
[CrossRef]

Byrne, D. M.

M. D. King, D. M. Byrne, B. M. Herman, J. A. Reagan, “Aerosol size distributions obtained by inversion of spectral optical depth measurements,” J. Atmos. Sci. 35, 2153–2167 (1978).
[CrossRef]

Chung, I. P.

I. P. Chung, D. Dunn-Rankin, “In situ light scattering measurements of mainstream and sidestream cigarette smoke,” Aerosol Sci. Technol. 24, 85–101 (1996).
[CrossRef]

Deepak, A.

Devir, A. D.

Dunn-Rankin, D.

I. P. Chung, D. Dunn-Rankin, “In situ light scattering measurements of mainstream and sidestream cigarette smoke,” Aerosol Sci. Technol. 24, 85–101 (1996).
[CrossRef]

Farone, W. A.

Ferri, F.

Grassl, H.

Heintzenberg, J.

Herman, B. M.

M. D. King, D. M. Byrne, B. M. Herman, J. A. Reagan, “Aerosol size distributions obtained by inversion of spectral optical depth measurements,” J. Atmos. Sci. 35, 2153–2167 (1978).
[CrossRef]

Hitzenberger, R.

Huffman, D. R.

C. F. Bohren, D. R. Huffman, Absorption and Scattering of Light by Small Particles (Wiley, New York, 1983).

Junge, C. E.

C. E. Junge, Air Chemistry and Radioactivity (Academic, New York, 1963).

Kassman, A. J.

Kerker, M.

King, M. D.

M. D. King, D. M. Byrne, B. M. Herman, J. A. Reagan, “Aerosol size distributions obtained by inversion of spectral optical depth measurements,” J. Atmos. Sci. 35, 2153–2167 (1978).
[CrossRef]

Lee, C. T.

C. T. Lee, J. J. Tsai, “Aerosol light-scattering coefficient and size distributions in a suburban area in Taiwan,” J. Aerosol Sci. 29, S651–S652 (1998).
[CrossRef]

Leith, D.

G. Ramachandran, D. Leith, L. Todd, “Extraction of spatial aerosol distributions from multispectral light extinction measurements with computed tomography,” J. Opt. Soc. Am. A 11, 144–154 (1994).
[CrossRef]

G. Ramachandran, D. Leith, “Extraction of aerosol-size distributions from multispectral light extinction data,” Aerosol Sci. Technol. 17, 303–325 (1992).
[CrossRef]

Lipson, S. G.

Mari, R.

W. Restani, R. Mari, Tutela dell’Ambiente Atmosferico (Pirola, Milan, Italy, 1995), Chap. 3.

McRae, D. D.

D. D. McRae, “The refractive index of individual cigarette smoke droplets,” J. Colloid Interface Sci. 87, 117–123 (1982).
[CrossRef]

Muller, H.

Paganini, E.

Parameswaran, K.

Quenzel, H.

Rajeev, K.

Ramachandran, G.

G. Ramachandran, D. Leith, L. Todd, “Extraction of spatial aerosol distributions from multispectral light extinction measurements with computed tomography,” J. Opt. Soc. Am. A 11, 144–154 (1994).
[CrossRef]

G. Ramachandran, D. Leith, “Extraction of aerosol-size distributions from multispectral light extinction data,” Aerosol Sci. Technol. 17, 303–325 (1992).
[CrossRef]

Reagan, J. A.

M. D. King, D. M. Byrne, B. M. Herman, J. A. Reagan, “Aerosol size distributions obtained by inversion of spectral optical depth measurements,” J. Atmos. Sci. 35, 2153–2167 (1978).
[CrossRef]

Restani, W.

W. Restani, R. Mari, Tutela dell’Ambiente Atmosferico (Pirola, Milan, Italy, 1995), Chap. 3.

Rizzi, R.

Sculley, M. J.

Tanaka, M.

Thomalla, E.

Todd, L.

Trakhovsky, E.

Tsai, J. J.

C. T. Lee, J. J. Tsai, “Aerosol light-scattering coefficient and size distributions in a suburban area in Taiwan,” J. Aerosol Sci. 29, S651–S652 (1998).
[CrossRef]

Twomey, S.

S. Twomey, Introduction to the Mathematics of Inversion in Remote Sensing and Indirect Measurements (Elsevier, Amsterdam, 1977).

Uthe, E. E.

van de Hulst, C.

C. van de Hulst, Light Scattering by Small Particles (Dover, New York, 1981), p. 127 and 388.

Whitby, K. T.

K. T. Whitby, “The physical characteristics of sulfur aerosols,” Atmos. Environ. 12, 135–139 (1978).
[CrossRef]

Wolf, E.

M. Born, E. Wolf, Principles of Optics (Pergmon, New York, 1959), p. 94.

Yamamoto, G.

Zaccanti, G.

G. Zaccanti, P. Bruscaglioni, “Deviation from the Lambert–Beer law in the transmittance of a light beam through diffusing media: experimental results,” J. Mod. Opt. 35, 229–242 (1988).
[CrossRef]

Aerosol Sci. Technol. (2)

G. Ramachandran, D. Leith, “Extraction of aerosol-size distributions from multispectral light extinction data,” Aerosol Sci. Technol. 17, 303–325 (1992).
[CrossRef]

I. P. Chung, D. Dunn-Rankin, “In situ light scattering measurements of mainstream and sidestream cigarette smoke,” Aerosol Sci. Technol. 24, 85–101 (1996).
[CrossRef]

Appl. Opt. (12)

G. Yamamoto, M. Tanaka, “Determination of aerosol size distribution from spectral attenuation measurements,” Appl. Opt. 8, 447–453 (1968).
[CrossRef]

A. Deepak, M. A. Box, “Forward scattering corrections for optical extinction measurements in aerosol media. 1. Monodispersions,” Appl. Opt. 17, 2900–2908 (2000).
[CrossRef]

A. Deepak, M. A. Box, “Forward scattering corrections for optical extinction measurements in aerosol media. 2. Polydispersions,” Appl. Opt. 17, 3169–3176 (1978).
[CrossRef] [PubMed]

J. Heintzenberg, H. Muller, H. Quenzel, E. Thomalla, “Information content of optical data with respect to aerosol properties: numerical studies with a randomized minimization-search-technique inversion algorithm,” Appl. Opt. 20, 1308–1315 (1981).
[CrossRef] [PubMed]

E. E. Uthe, “Particle size evaluations using multiwavelength extinction measurements,” Appl. Opt. 21, 454–459 (1982).
[CrossRef] [PubMed]

E. Trakhovsky, S. G. Lipson, A. D. Devir, “Atmospheric aerosols investigated by inversion of experimental transmittance data,” Appl. Opt. 21, 3005–3010 (1982).
[CrossRef] [PubMed]

R. Hitzenberger, R. Rizzi, “Retrieved and measured aerosol mass size distributions: a comparison,” Appl. Opt. 25, 546–553 (1986).
[CrossRef] [PubMed]

F. Ferri, A. Bassini, E. Paganini, “Commercial spectrophotometer for particle sizing,” Appl. Opt. 36, 885–891 (1997).
[CrossRef] [PubMed]

K. Rajeev, K. Parameswaran, “Iterative method for the inversion of multiwavelength lidar signals to determine aerosol size distribution,” Appl. Opt. 37, 4690–4700 (1998).
[CrossRef]

F. Ferri, A. Bassini, E. Paganini, “Modified version of Chahine algorithm to invert spectral extinction data for particle sizing,” Appl. Opt. 34, 5829–5839 (1995).
[CrossRef] [PubMed]

H. Grassl, “Determination of aerosol size distributions from spectral attenuation measurements,” Appl. Opt. 10, 2534–2538 (1971).
[CrossRef] [PubMed]

M. Kerker, M. J. Sculley, W. A. Farone, A. J. Kassman, “Optical properties of cigarette smoke aerosols,” Appl. Opt. 17, 3030–3031 (1978).
[CrossRef] [PubMed]

Atmos. Environ. (1)

K. T. Whitby, “The physical characteristics of sulfur aerosols,” Atmos. Environ. 12, 135–139 (1978).
[CrossRef]

J. Aerosol Sci. (2)

C. T. Lee, J. J. Tsai, “Aerosol light-scattering coefficient and size distributions in a suburban area in Taiwan,” J. Aerosol Sci. 29, S651–S652 (1998).
[CrossRef]

G. Kasper, J. H. Vincent, eds., “Abstracts of the 5th International Aerosol Conference 1998,” J. Aerosol Sci. 29, S295–S318 (1998).

J. Atmos. Sci. (1)

M. D. King, D. M. Byrne, B. M. Herman, J. A. Reagan, “Aerosol size distributions obtained by inversion of spectral optical depth measurements,” J. Atmos. Sci. 35, 2153–2167 (1978).
[CrossRef]

J. Colloid Interface Sci. (1)

D. D. McRae, “The refractive index of individual cigarette smoke droplets,” J. Colloid Interface Sci. 87, 117–123 (1982).
[CrossRef]

J. Mod. Opt. (1)

G. Zaccanti, P. Bruscaglioni, “Deviation from the Lambert–Beer law in the transmittance of a light beam through diffusing media: experimental results,” J. Mod. Opt. 35, 229–242 (1988).
[CrossRef]

J. Opt. Soc. Am. A (1)

Other (8)

M. Born, E. Wolf, Principles of Optics (Pergmon, New York, 1959), p. 94.

C. E. Junge, Air Chemistry and Radioactivity (Academic, New York, 1963).

R. M. Harrison, R. E. van Grieken, eds., Atmospheric Particles (Wiley, New York, 1998).

C. F. Bohren, D. R. Huffman, Absorption and Scattering of Light by Small Particles (Wiley, New York, 1983).

W. L. Wolfe, G. J. Zissis, eds., The Infrared Handbook (Environmental Research Institute of Michigan, Ann Arbor, Mich., 1989), p. 111.

W. Restani, R. Mari, Tutela dell’Ambiente Atmosferico (Pirola, Milan, Italy, 1995), Chap. 3.

C. van de Hulst, Light Scattering by Small Particles (Dover, New York, 1981), p. 127 and 388.

S. Twomey, Introduction to the Mathematics of Inversion in Remote Sensing and Indirect Measurements (Elsevier, Amsterdam, 1977).

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Figures (14)

Fig. 1
Fig. 1

Optical layout of the instrument. Abbreviations are defined in text.

Fig. 2
Fig. 2

Behavior of the extinction coefficient measured in a class 100,000 clean room. (U.S. Federal Standard 209E). The four curves show four different instrument configurations. The peaks are due to absorption bands of the gases dispersed in air, mainly O2 and H2O (see also Fig. 10 below).

Fig. 3
Fig. 3

Behavior of the extinction coefficient of calibrated 0.73-µm-radius latex spheres for several sample volume fractions that vary from 3.29 × 10-5 to 2.78 × 10-8 (top to bottom). The spheres were dispersed in water and confined in a cell with a 10-mm optical path. Symbols represent the experimental data, whereas solid curves are the extinction data reconstructed on the basis of the recovered distributions. For clarity, the symbols for the two lowest (and noisiest) curves are different from all the others.

Fig. 4
Fig. 4

Retrieved distributions obtained by inversion of the data of Fig. 3. The top and bottom curves refer to volume fractions of 2.16 × 10-5 and 4.98 × 10-7, respectively. The arrow indicates the nominal average radius. For clarity, only some of the distributions that correspond to the data of Fig. 3 are displayed. They correspond to the 2nd, 3rd, 4th, 5th, and 7th curves of Fig. 3 (top to bottom).

Fig. 5
Fig. 5

Errors in the recovered parameters that characterize the distributions of Fig. 4 as a function of sample concentration: (a) rms deviations between the experimental and the recovered data, (b) percentage deviations between the recovered average radius and the nominal one, (c) percentage deviations between the recovered and the actual sample concentrations. The dashed vertical lines indicate the equivalent limits for atmospheric pollution and emissions from chimneys imposed by the EEC (see text).

Fig. 6
Fig. 6

Behavior of the extinction coefficient for calibrated latex spheres dispersed in water and confined in a cell with a 10-mm optical path. The radii of the spheres were 0.326 and 1.12 µm. Symbols represent the measured extinction data, whereas curves are the results of the inversion procedure.

Fig. 7
Fig. 7

Extinction coefficient corresponding to the lowtran model for a clean rural atmosphere characterized by a ground-level visibility of 23 km. The symbols are the synthetic data provided by the model; the curve shows the data reconstructed on the basis of the recovered distribution (see Fig. 8). The data are not uniformly distributed along the wavelength axis because they were taken to avoid the spectral regions where the absorption bands of the gases dispersed in atmosphere are present.

Fig. 8
Fig. 8

Comparison of the theoretical distribution predicted by the lowtran model and the distribution obtained by inversion of the data of Fig. 7 (dashed curve). The range of radii used for the inversion was 0.02–1 µm.

Fig. 9
Fig. 9

Picture of the environment where the measurements in the underground corridor were taken. The instrumental setup, together with the projection–detection head and the retroreflectors, is also shown.

Fig. 10
Fig. 10

Comparison of the transmission spectra predicted by the lowtran model and those measured in the 100,000 class clean room and in the underground corridor. The curves are for an optical path of 68 m.

Fig. 11
Fig. 11

Comparison of the extinction coefficients predicted by the lowtran model (circles) and that measured in the underground corridor (squares). We obtained the two spectra from the corresponding curves of Fig. 10 by selecting the wavelengths at which the absorption bands caused by gases dispersed in atmosphere are not present. The solid curves are the data reconstructed on the basis of the recovered distributions (see Fig. 12).

Fig. 12
Fig. 12

Comparison of the volume fraction distribution expected for the lowtran model (solid curve) and the two distributions obtained by inversion of the data of Fig. 11. The distribution that corresponds to the measurement in the underground corridor (dotted curve) is definitively much different from the distribution recovered by inversion of the synthetic lowtran data (dashed curve), with an overall volume fraction higher than a factor of ∼2.

Fig. 13
Fig. 13

Comparison of the extinction coefficients that are due to cigarette-smoke aerosols that were kept in the oral cavity (a) for a few seconds and (b) for ∼10 s. Symbols represent the measured extinction data, whereas the curves are the data reconstructed on the basis of the recovered distributions (see Fig. 14).

Fig. 14
Fig. 14

Comparison of the particle size distributions recovered by inversion of the data of Fig. 13. (a) The smoke kept in the oral cavity for only a few seconds exhibits a very narrow distribution with an average radius of ∼0.20 µm. Conversely, the distribution of the smoke kept longer is much broader, with an average radius of ∼0.43 µm.

Equations (2)

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PT=P0 exp-αλd,
αλ=πr2Qextr, λ, mNrdr,

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