Purpose:

Currently, no standard protocol exists for making nonpoint source measurements of air emission flux. An accurate and cost-effective method is needed to quantify nonpoint air emissions from Department of Defense (DoD) sources. Current estimation techniques for nonpoint sources based on emission factors are imprecise and typically overestimate emissions drastically. Multiple point measurements are locally accurate but may not be representative of the entire plume, and it is costly to obtain the quantities required. The purpose of this project is to demonstrate standardized nonpoint source measurement methods based on path-integrated optical remote sensing (PI-ORS) and computed tomography, developed by ARCADIS in Research Triangle Park, NC. To facilitate regulatory approval, an approved Environmental Protection Agency (EPA) protocol and methods will be developed in close collaboration with the EPA Emission Measurement Center.

Description:

Path-integrated optical remote sensing [e.g., open-path Fourier-transform infrared (OP-FTIR) spectroscopy] uses multiple beam paths and optimizing algorithms to give a time-averaged, mass-equivalent concentration field across a plume of contaminant, from which the emission rate can be determined without dispersion modeling. Reflectors are deployed in a radial asymmetric pattern that includes the emission area source, from which the approximate boundaries of the plume's origin can be determined. When the plume is located, the array of reflectors is redeployed in a vertical plane immediately downwind and centered across the plume's origin. The PI-ORS system scans from reflector to reflector in a constant pattern, separately accumulating values for each reflector to generate a long-term average in each spatial element. The novelty is in placing a two-dimensional array of reflectors so the absorption information can be directly translated, by a tomographic algorithm, into time-averaged area concentrations without using dispersion model estimates. Source strength is effectively the product of the sum of the area concentration elements multiplied by the average wind speed during the determinations.

Benefits:

Advantages of the PI-ORS/tomography technology include accuracy and low cost. The alternative is to use an array of Summa canisters and reverse dispersion models, which both require intensive and very expensive post analyses. PI-ORS/tomography avoids inaccuracies introduced by assumptions required for the dispersion modeling. PI-ORS also allows samples to be taken at intervals of minutes instead of hours, giving information on temporal variations of emissions that simply is not available with a canister method. (Anticipated Project Completion - 2005)

Contact:

Mr. Patrick Sullivan
AFRL/MLQF
139 Barnes Drive, Suite 2
Tyndall AFB, FL 32403-5323
Telephone: (850) 283-0430
Fax: (850) 283-9707
E-mail: patrick.sullivan@tyndall.af.mil