In situ measurement of the infrared absorption and extinction of chemical and biologically derived aerosols using flow-through photoacoustics.
In an effort to establish a more reliable set of optical cross sections for a variety of chemical and biological aerosol simulants, we have developed a flow-through photoacoustic system that is capable of measuring absolute, mass-normalized extinction and absorption cross sections. By employing a flow-through design we avoid issues associated with closed aerosol photoacoustic systems and improve sensitivity. Although the results shown here were obtained for the tunable CO2 laser waveband region, i.e., 9.20-10.80 microm, application to other wavelengths is easily achievable. The aerosols considered are categorized as biological, chemical, and inorganic in origin, i.e., Bacillus atrophaeus endospores, dimethicone silicone oil (SF-96 grade 50), and kaolin clay powder (alumina and silicate), respectively. Results compare well with spectral extinction measured previously by Fourier-transform infrared spectroscopy. Comparisons with Mie theory calculations based on previously published complex indices of refraction and measured size distributions are also presented.
Gurton
Kristan P
KP
US Army Research Laboratory, Harry Diamond Laboratories, 2800 Powder Mill Road, Adelphi, Maryland 20783-1145, USA. kgurton@arl.army.mil
Dahmani
Rachid
R
Ligon
David
D
Bronk
Burt V
BV
D000162:Acoustics; D000336:Aerosols / Q000032:analysis*; D000393:Air Pollutants / Q000032:analysis*; D001407:Bacillus / Q000302:isolation & purification; D001419:Bacteria / Q000302:isolation & purification*; D001704:Biopolymers / Q000032:analysis*; D004784:Environmental Monitoring / Q000295:instrumentation / Q000379:methods; D007616:Kaolin / Q000032:analysis; D012031:Refractometry / Q000295:instrumentation / Q000379:methods*; D012827:Silicone Oils / Q000032:analysis; D017550:Spectroscopy, Fourier Transform Infrared / Q000295:instrumentation / Q000379:methods*
D000336:Aerosols; D000393:Air Pollutants; D001704:Biopolymers; D012827:Silicone Oils; D007616:Kaolin