Remote sensing studies in support of rational decision making for short- and long-term stewardship

This project seeks to develop a general-purpose method to create a computer-generated transmission spectra for H2O and CO2 using the HITRAN96 spectral line database and other software. Then, the synthetic background method is tested with two separate open path instruments. Open path spectroscopy when coupled with computed tomography has been shown to provide useful estimates of emission rates from area sources and to allow localization of emission hot spots. However, one limitation this technique has had is the problem of collecting a clean reference or background spectra. A pollutant-free background spectrum is generally needed to accurately detect and quantify the target gases in the sample beam. These problems have been experienced first hand on and off the Hanford DOE site. A solution to the background problem is to create a synthetic background using a computer model of the optical transmission through the atmosphere. In practice this means it is necessary to model the infrared absorbance of water and CO2, which are always present and the sample spectra and produce the strongest IR spectral lines that are temperature, pressure and instrument dependent. A general-purpose method is developed to create a computer-generated transmission spectra for H2O and CO2 using the HITRAN96 spectral line database and other software we are developing. Then the synthetic background method is tested with 2 separate open path instruments. Several other pollutant gases also can be modeled in this way, and thus these spectra can also be synthesized. These include both primary target gases at Hanford, gas, N2O and a gas identified as are current emission at the tank farm NH3. The goals of the project are to decrease the LOD for these compounds due to improved background and reference spectra, and to investigate the baseline spectra that remains after the new synthetic interfering and target species are removed. Previously it has been shown that the baseline can be used to obtain information of aerosols in the optical path; therefore a secondary goal of this effort is to develop a method to detect for aerosol releases as well as quantify gases.