Mark J. Thomas

A Method of Predicting Point and Path- Averaged Ambient Air VOC Concentrations, Using Meteorological Data

A method of predicting point and path-averaged ambient air VOC concentrations is described. This method was developed for the case of a plume generated from a single point source, and is based on the relationship between wind directional frequency and concentration. One-minute means of wind direction and wind speed were used as inputs to a Gaussian dispersion model to develop this relationship. Both FTIR spectrometry and a whole-air sampling method were used to monitor VOC plumes during simulated field tests. One test set was also conducted using only whole-air samplers deployed in a closely-spaced network, thus providing an evaluation of the prediction technique free of any bias that might exist between the two analytical methods. Correlations between observed point concentrations and wind directional frequencies were significant at the 0.05 level in most cases. Predicted path-integrated concentrations, based on observed point concentrations and meteorological data, were strongly correlated with observed...

Infrared detection and analysis of vapor plumes using an airborne sensor

An airborne infrared (IR) line-scanner and a Fourier transform infrared (FT-IR) spectrometer operating in the 3- 5micrometers and 8-12micrometers spectral regions provide a rapid wide- area surveillance capability. The IR scene containing target vapors is mapped remotely with the wide fields of view (FOV) multi-spectral IR line-scanner using 14 bands. The narrow FOV FT-IR spectrometer permits remote verification of target vapor plume contents within the IR scene. The IR image and FT-IR interferogram analysis supply a near real-time detection that provides visual monitoring of potential downwind vapor hazards. This capability is demonstrated using the target vapor methanol. An active mono-static FT-IR configuration furnishes ground-truth monitoring for methanol released from an industrial stack and a nearby ground-level area. The airborne and ground-truth results demonstrate the usefulness of this approach in alerting first responders to potential downwind vapor hazards from an accidental release.

Airborne remote sensing for Deepwater Horizon oil spill emergency response

On April 28, 2010, the Environmental Protection Agencys (EPA) Airborne Spectral Photometric Environmental Collection Technology (ASPECT) aircraft was deployed to Gulfport, Mississippi to provide airborne remotely sensed air monitoring and situational awareness data and products in response to the Deepwater Horizon oil rig disaster. The ASPECT aircraft was released from service on August 9, 2010 after having flown over 75 missions that included over 250 hours of flight operation. ASPECTs initial mission responsibility was to provide air quality monitoring (i.e., identification of vapor species) during various oil burning operations. The ASPECT airborne wide-area infrared remote sensing spectral data was used to evaluate the hazard potential of vapors being produced from open water oil burns near the Deepwater Horizon rig site. Other significant remote sensing data products and innovations included the development of an advanced capability to correctly identify, locate, characterize, and quantify surface oil that could reach beaches and wetland areas. This advanced identification product provided the Incident Command an improved capability to locate surface oil in order to improve the effectiveness of oil skimmer vessel recovery efforts directed by the US Coast Guard. This paper discusses the application of infrared spectroscopy and multispectral infrared imagery to address significant issues associated with this national crisis. More specifically, this paper addresses the airborne remote sensing capabilities, technology, and data analysis products developed specifically to optimize the resources and capabilities of the Deepwater Horizon Incident Command structure personnel and their remediation efforts.

Airborne Mapping of Chemical Plumes in the Aftermath of Hurricanes Katrina and Rita

Infrared airborne spectral measurements were collected over the Gulf Coast area during the aftermath of Hurricanes Katrina and Rita. These measurements allowed surveillance for potentially hazardous chemical vapor releases from industrial facilities caused by storm damage. Data was collected with a mid-longwave infrared multispectral imager and a hyperspectral Fourier transform infrared spectrometer operating in a low altitude aircraft. Signal processing allowed detection and identification of targeted spectral signatures in the presence of interferents, atmospheric contributions, and thermal clutter. Results confirmed the presence of a number of chemical vapors. All detection results were immediately passed along to emergency first responders on the ground. The chemical identification, location, and vapor species concentration information were used by the emergency response ground teams for identification of critical plume releases and subsequent mitigation.

Preliminary Assessment of the Utility of Airborne Infrared Spectroscopic Analysis of Emissions from a Variety of Flooded Areas in the United States

Airborne passive hyperspectral infrared spectral measurements of chemical vapors in the atmosphere have been completed over a wide variety of locations throughout the United States. These measurements are part of the US EPA emergency response chemical disaster mitigation capability. Analysis and regional comparison of these atmospheric measurements reveals a glycol constituent, which has been noted during flooding conditions along the Southern Gulf Coast Region and the Midwestern United States. This discussion will describe several differences in the natural atmospheric background for vapor species identified in various regions of the country. There are two possible sources for this constituent in these regions one is a natural source the other is an anthropogenic source. The paper will highlight the usefulness of passive infrared spectral measurements to determine key atmospheric indicators correlated with locations of major flooding along with the identification of naturally occurring species.

A portable vapor cell for passive FT-IR spectrometer evaluation

Gravimetrically prepared aqueous binary solutions permit the generation of target vapors of methanol and ammonia in a portable vapor cell. A passive Fourier transform infrared (FT-IR) spectrometer monitors a short pathlength optical cell using a calibrated extended-blackbody background source. The temperature of the blackbody ranges from 5°C to 50°C in five degree increments. This temperature range simulates the radiance levels most often encountered for ambient temperature backgrounds in open-air field measurements. The solute liquid mole fractions determine the resultant vapor concentrations. The water component attenuates the target vapor concentration from that of the pure solute component depending on the solute liquid mole fraction. This study demonstrates the utility of a portable vapor cell using a series of binary aqueous solutions per target compound over the Beer’s Law range of infrared absorbances. These Beer’s Law infrared absorbances and blackbody radiance levels are within the linearity range of the passive FT-IR spectrometer and are representative of open-air field conditions.

Assessment of data intercomparability and data quality for multiple open-path FTIR systems

There exists little information concerning the quality of data generated from open-path Fourier transform infrared spectrometer (OP-FTIR) systems as applied to measuring toxic air pollutants. The U.S. Environmental Protection Agency, Region VII conducted a study designed to assess the intercomparability and data quality for several OP-FTIR systems. This paper describes the design of the study, presents the resulting data, and discusses the conclusions reached.

Art of atmospheric monitoring

Road, Kansas City, Kansas 66115D.F. GurkaU.S. Environmental Protection Agency, Quality Assurance DivisionEnvironmental Monitoring Systems Laboratory, Las Vegas, Nevada 89119ABSTRACTThe Department of Chemistry at Kansas State University has been developing and testing a mobileFourier transform infrared (FT-IR) spectrometer system. The main purpose of the mobile FT-IR spectrometersystem is for performing long-path atmospheric monitoring of volatile organic compounds (VOCs) from avariety of emission sources.15Testing of the FT-IR system began four years ago with controlled release of VOCS at the Universityof Kansas (stage 1). The testing has culminated with monitoring of sites where uncontrolled releases of VOCSare occurring and the site itself has little or no precharacterization (stage 3).1

Automated detection of radioisotopes from an aircraft platform by pattern recognition analysis of gamma-ray spectra

A generalized methodology was developed for automating the detection of radioisotopes from gamma-ray spectra collected from an aircraft platform using sodium-iodide detectors. Employing data provided by the U.S Environmental Protection Agency Airborne Spectral Photometric Environmental Collection Technology (ASPECT) program, multivariate classification models based on nonparametric linear discriminant analysis were developed for application to spectra that were preprocessed through a combination of altitude-based scaling and digital filtering. Training sets of spectra for use in building classification models were assembled from a combination of background spectra collected in the field and synthesized spectra obtained by superimposing laboratory-collected spectra of target radioisotopes onto field backgrounds. This approach eliminated the need for field experimentation with radioactive sources for use in building classification models. Through a bi-Gaussian modeling procedure, the discriminant scores that served as the outputs from the classification models were related to associated confidence levels. This provided an easily interpreted result regarding the presence or absence of the signature of a specific radioisotope in each collected spectrum. Through the use of this approach, classifiers were built for cesium-137 (137Cs) and cobalt-60 (60Co), two radioisotopes that are of interest in airborne radiological monitoring applications. The optimized classifiers were tested with field data collected from a set of six geographically diverse sites, three of which contained either 137Cs, 60Co, or both. When the optimized classification models were applied, the overall percentages of correct classifications for spectra collected at these sites were 99.9 and 97.9% for the 60Co and 137Cs classifiers, respectively.

Real-Time Radionuclide Identification and Mapping Capabilities of the U.S. Environmental Protection Agency’s Airborne Spectral Photometric Environmental Collection Technology

The U.S. Environmental Protection Agency, CBRN Consequence Management Advisory Team fields a fixed-wing aircraft known as the Airborne Spectral Photometric Environmental Collection Technology (ASPECT). ASPECT is a 24/7/365 response-ready asset that can be airborne within an hour and collecting chemical, radiological and photographic data anywhere in the continental United States within 9 hours of notification from its home base near Dallas, TX. A primary goal of the program is to provide actionable intelligence to decision makers within minutes of data collection via the aircraft satellite communication system while the aircraft is still flying. To achieve this goal, a new method to process airborne gamma spectroscopy data was investigated that effectively eliminates the need for traditional airborne calibration methods currently used in airborne systems (e.g., stripping coefficients, test lines, radon correction, altitude, and background corrections). The new algorithm provides nuclide identification near real-time and creates an radionuclide-specific map without user-interface input.