Real-Time Measurements of Respirable Crystalline Silica, Kaolinite, Coal, and Calcite Dust with a Quantum Cascade Laser Equipped Photoacoustic Instrument

W. PATRICK ARNOTT, Charles Kocsis, Xiaoliang Wang, Bankole Osho, Samuel Taylor, Pedro Nascimento, Bjoern Bingham, Chauntelle Murphy, Michael Sandink, University of Nevada, Reno

     Abstract Number: 193
     Working Group: Instrumentation and Methods

Abstract
Practical, real-time measurements of speciated dust mass concentration (SDMC) are needed for health and ventilation applications in industrial applications such as mining. The most common method requires deposition of dust on filters through use of a vacuum pump, and subsequent Fourier Transform Infrared Spectroscopic analysis. We are developing a photoacoustic spectrometer (PAS) equipped with a tunable quantum cascade laser (QCL) to measure SDMC in real-time. In laboratory experiments, the QCL has been sequentially tuned to four wavelengths to quantify the SDMC of respirable crystalline silica (RCS), kaolinite, coal, and calcite. Each dust type also absorbs a little laser light at the other three wavelengths. A matrix of measurements quantifies the relationship between SDMC and aerosol light absorption at the four wavelengths. The inverse of this matrix provides SDMC from PAS measurements for a mixture containing all four dust types. Individual and mixed dust measurements demonstrate the current state of the art in PAS sampling of SDMC. Light absorption by water vapor can be used to calibrate the instrument. These measurements also have applications in the atmosphere to infrared radiative forcing by dust.