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Dr. Ram Hashmonay ARCADIS 4915 Prospectus Dr., Suite F Durham, NC 27713

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Extinction Spectroscopy for Characterization of Particulate Matter Size and Concentration in Fugitive Plumes. Dr. Ram Hashmonay ARCADIS 4915 Prospectus Dr., Suite F Durham, NC 27713. Method Description. OP-FTIR is an accepted method for gas measurements

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slide1

Extinction Spectroscopy for Characterization of Particulate Matter Size and Concentration in Fugitive Plumes

Dr. Ram Hashmonay

ARCADIS

4915 Prospectus Dr., Suite F

Durham, NC 27713

method description
Method Description
  • OP-FTIR is an accepted method for gas measurements
  • Particulate matter (PM) presence reveals a unique baseline structure (see below)
method description cont
Method Description (cont.)
  • Baseline structure can be predicted for a given size distribution and optical constants using Mie theory
  • We developed an inversion algorithm to retrieve the aerosol size distribution from extinction (scattering+absorption) measurements
  • Optical properties (constants) of specific PM may be determined using a bench-top FTIR spectrometer
mie theory
Mie Theory

Size Parameter a

d - particle diameter

l - wavelength

mie theory cont
Mie Theory (cont.)

Complex Refractive Index

m(l) = n(l)-ik(l)

n – scattering term (refraction and reflection)

k – absorption term

mie theory cont1
Mie Theory (cont.)

Extinction Efficiency:

  • Extinction efficiency of water in different part of the FTIR spectrum
slide7

Extinction as Function of Wavelength

  • sei - extinction for the ithwavelength
  • Qeij- dimensionless extinction efficiencies
  • Nj- number density for the jth aerosol size
  • dj- is the aerosol jth size class (diameter)
shower experiment
Shower Experiment
  • OP-FTIR beam through water condensation aerosol
  • Size distribution confirmed by aerosol probe
  • Known optical constants (see below)
slide16

Louisville Landfill Set-Up

Landfill

Dirt Road

OP-FTIR Beam

slide31

Conclusions

  • The first open-path optical technique to obtain real-time fugitive dust measurement and sizing
  • Measurement of liquid aerosol like water or pesticide drift
  • OP-FTIR can be used in field to gather multiple gases and PM emission data simultaneously
  • Extending the spectral range to the UV/VIS range will allow sizing of submicron PM