During the cleanup of dioxin-contaminated soils from the Times Beach, Missouri, Superfund site, workers excavating a trench near the old City Park became nauseous from fumes emanating the excavation ditch. Investigations by US EPA and Missouri Department of Natural Resources found that approximately 12,000 square feet of soil was contaminated by toluene, ethylbenzene, and xylenes. During the remediation of this site, Open-Path FTIR was used to monitor the perimeter of the excavation and stockpile areas. The air monitoring data was collected and screened on a near real time basis to ensure that off-site workers and the public were protected. This paper outlines the air monitoring procedures used during the project and the difficulties encountered while sampling at the site.

A pilot study was performed in order to gather data to determine the efficiencies of two nearby CO flares. Each flare stack was about 150 feet high with the thermal rise of the flare raising the resulting plume to about 200 feet. Since there are no routinely accepted methods for determining flare emissions, especially for such high flares, the pilot study was designed to collect the appropriate data using open-path Fourier Transform Infrared (OP-FTIR) technology. There were a number of challenges both in physically setting up the equipment and in evaluating the resulting spectra: (1) The retroreflector needed to be hung on a 300 foot crane in order to have the plume centerlines near the center of the beam. (2) The positions of the crane and main OP-FTIR unit had to be determined in relation to availability of space at the appropriate downwind distances since this was an operating facility. (3) The tracer gases (SF₆ and CF₄) needed to be released at rates to provide sufficiently high downwind concentrations. (4) Sufficient upwind data needed to be collected to be able to subtract the background CO and CO₂ values with enough accuracy to provide data for efficiency calculation. (5) The spectra collected for the beam paths (approximately 300 to 350 m from main unit to retroreflector angled from ground level to approximately 100 meters) traversed a wide range of temperatures and to a certain degree pressures which would affect the determination of the plume concentrations. This paper presents a discussion of these challenges and the degrees to which they were met. Suggestions for improving such studies is also included.

Open-path Fourier transform-infrared (OP-FTIR) was used to collect emission data for a number of chemical compounds for several area sources at a northwestern industrial facility. The data collected was used in conjunction with meteorological measurements to assess the emission rate of several of the compounds from these area sources. The release of a tracer gas at a known emission rate and its subsequent measurement with the OP-FTIR allowed for correction of emission rates to account for local effects on the site specific vertical dispersion coefficients used for emission assessments. The methodology for emission rate assessment is presented, and the implications of correcting for site specific vertical dispersion are discussed. Four area source case studies are included for the study. Most of this data was collected during cold temperature conditions, and some of the data collected during the night time hours, this represents one of the first studies of site specific vertical dispersion under these conditions. Possible impacts of these conditions on emission rate determinations will be presented. The effectiveness of OP-FTIR as a tool for area source emission rate assessment will be evaluated. OP-FTIR was employed for data collection because of its ability to detect the compounds of interest accurately and with reasonable levels of detectability. Emission rate determinations were done for process ponds AA, and BB. Fence-line concentration measurements were also made north of pond AA. The on-site study was conducted from 11/10/97 through 11/26/97. The data collected indicated that moderate to significant levels of two target compounds were being emitted by both pond AA and pond BB. Emission rates were estimated using text book dispersion coefficients and found to overestimate actual emission rates based on tracer gas release significantly. One target compound's emission rate was found to also be related to wind speed.

The emission rates of diffuse and heterogeneous distributed sources are difficult to determine because point measurements are not representative. Therefore a method was further developed to determine gaseous emission rates by measurements of path-integrated mixing ratios with open-path spectroscopic systems in the exhaust plume (VOC, NH₃, CH₄, N₂O, CO, CO₂) and of meteorological parameters. Inverse dispersion modeling is used to quantify the emission rates afterwards with these data. The measurements are performed by Fourier Transform Infrared (FTIR) spectroscopy and Differential Optical Absorption Spectroscopy (DOAS) at 50 to 500 m optical path lengths about 1 to 20 m above ground level. The measurement accuracy for greenhouse gases and ammonia is about plus or minus 10% and for BTX about plus or minus 30%. The whole method was validated at a livestock building with a single exhaust chimney. The Gaussian model PAL was applied for inverse modeling to investigate limited pieces of land and isolated facilities in flat terrain. Including the accuracy of the dispersion simulations the determined emission rates have an error margin of about plus or minus 30%. Results of measurement campaigns are discussed as emission rates of ammonia from slurry spreading as well as of benzene from gas stations and a tank farm.

On-site determination of volatile organic pollutants in ground water supplies is important for remediation. A simple fiber- optic probe suitable for remote analysis using resonance enhanced multiphoton ionization has been developed and is used to determine the toluene concentration in water samples spiked with gasoline via a head space measurement. An optical fiber transmits a high power laser pulse (266 nm) to the sample, ionizing it, and the subsequent ions are collected with a platinum electrode. Measurements take approximately 1.5 minutes to perform, require no sample preparation, and have been demonstrated over distances of five meters. The limit of detection for toluene in water using this probe is 1.54 plus or minus 0.02 ppb (wt/wt). In addition to the 1 + 1 excitation, the feasibility of a 2 + 2 excitation scheme using 532 nm has been investigated.

The evolution of approaches to simultaneous real-time acquisition of analytical data from multiple locations is analyzed. Greatest emphasis is placed on optical time-of- flight (OTOF) chemical detection when the measurements are taken along the length of a single continuous extended-length 'distributed' sensing element. The attractive features of such distributed sensing element fabricated by immobilization of chemically sensitive reagents directly into the original cladding of a conventional plastic-clad silica (PCS) optical fiber are demonstrated. Several signal generation and processing methods are devised to address the requirements for spatially resolved chemical sensing. These requirements include high signal levels, a fairly uniform detection limit over the length of the sensing fiber, measurements with dynamically quenched fluorophores, and high spatial resolution. Applications of OTOF distributed chemical sensors for spatially resolved analyte mapping for environmental and process applications are discussed.

Raman spectroscopy was utilized to acquire resolved spectra of the neutral and zwitterion involved in the tautomeric solution equilibrium of 3-hydroxypyridine. As these species exist in varying proportion to one another at different temperatures, spectral measurements across a series of temperatures was required. Previously determined microequilibrium and enthalpy constants allowed the calculation of concentrations at all temperatures. This allowed for the deconvolution of component Raman spectra by multiple linear regression. The spectra are found to be similar, but contain significant structurally related differences, sufficient to distinguish one species from the other. To our knowledge, resolved Raman spectra of tautomers in water has not previously been reported.

The objective of this investigation was to develop a fast method for the in-situ characterization of chemicals solved in water based on Coherent Antistokes Raman Scattering (CARS). In order to test the potential of CARS as a tool for the in-situ spectroscopy scanning and multiplex CARS techniques were investigated. Polarization CARS (PCARS) was used to reduce the nonvibrational resonant signal generated by the electron cloud of the solvent molecules. The spectra of some alcohols and pollutants such as pyridine, nitrate and sulfate were investigated. Computer simulations were applied for the evaluation of the CARS spectra. The most evident advantage of CARS in comparison with other Raman methods is the very short time to achieve a spectrum. The shortest time to get a spectrum is limited by the length of the laser pulse (e.g. 5 ns). In addition no sample preparation is necessary.

A wide range of excitation and emission wavelengths is measured using the technique of two-dimensional (2D-) fluorescence spectroscopy. In a single, so called, two- dimensional fluorescence spectrum several biogenic fluorophors like proteins, vitamins and coenzymes can be detected simultaneously. This can give important information for bioprocess monitoring and control. An optical sensor (BioView^R) for on line fluorescence measurements at industrial (bio)-processes was used to get the results presented in this paper. This BioView^R-sensor is optimized to work in the harsh environment of production sites in biotechnological industry and -- using an optical light guide system with open-end detection -- it is very well suited for in vivo measurements, because it is non-invasive and the on line data can be performed in-situ.

A rapid and sensitive fluorescence assay for oxidative damage to calf thymus DNA is reported. A decrease in the transition temperature for strand separation resulted from exposure of the DNA to the reactive decomposition products of 3- morpholinosydnonimine (SIN-1) (i.e., nitric oxide, superoxide, peroxynitrite, hydrogen peroxide, and hydroxyl radicals). A decrease in melting temperature of 12 degrees Celsius was indicative of oxidative damage including single strand chain breaks. Double stranded (ds) and single stranded (ss) forms of DNA were determined using the indicator dyes ethidium bromide and PicoGreen. The change in DNA 'melting' curves was dependant on the concentration of SIN-1 and was most pronounced at 75 degrees Celsius. This chemically induced damage was significantly inhibited by sodium citrate, tris(hydroxymethyl)aminomethane (Tris), and diethylenetriaminepentaacetic acid (DTPA), but was unaffected by superoxide dismutase (SOD), catalase, ethylenediamine tetraacietic acid (EDTA), or deferoxamine. Lowest observable effect level for SIN-1-induced damage was 200 (mu) M.

In the present research it was attempted to test the effectiveness of low frequency radiation's such as those produced by microwaves in the degradation of pollutants normally present in domestic and industrial effluent. In order to avoid undue temperature increase, the multiple irradiation method was used. The work was performed initially using the o- chlorophenol as target compound, then extending the applications to the other isomers, to a surfactant such as sodium dodecylbenzenesulphonate and an organophosphorous pesticide such as paraoxon and finally applying the methodology to the solution of a problem as that one of the environmental impact of expired drugs disposal. In all the cases the positive effect of microwaves on the photodegradation rate was evidenced.

Because of their involvement in environmental pollutants, in carcinogenic activity, plastics, pharmaceuticals, synthesis of some laser dyes and presence in interstellar space etc., Polycyclic aromatic hydrocarbons (PAHs) are important. As their structure and properties can be varied systematically, they form a beautiful class of molecules for experimental and quantum chemical investigations. These molecules are being studied for last several years by using conventional spectroscopy. In recent years, Photoacoustic (PA) spectroscopy has emerged as a new non-destructive technique with unique capability and sensitivity. The PA effect is the process of generation of acoustic waves in a sample resulting from the absorption of photons. This technique not only reveals non- radiative transitions but also provides information about forbidden singlet-triplet transitions which are not observed normally by the conventional spectroscopy. The present paper deals with the spectroscopic studies of some PAH molecules by PA spectroscopy in the region 250 - 400 nm. The CNDO/S-CI method is used to calculate the electronic transitions with the optimized geometries. A good agreement is found between the experimental and calculated results.

We conducted a preliminary experiment in controlled ventilation chamber where a single source of Nitrous Oxide was released. A scanning Open Path Fourier Transform Infrared (OP- FTIR) system acquired Path Integrated Concentration (PIC) data of 19 beams scanned in a radial non-overlapping beam geometry. Prior to the experiment we conducted a calibration procedure by creating a homogeneous atmosphere inside the ventilation chamber. The Smooth Basis Function Minimization (SBFM) algorithm, which fits parametric distributions rather than fitting individual pixel concentrations, was used to reconstruct two-dimensional concentration maps from this beam geometry. The preliminary results show that good reconstructions are possible with this approach. Further, our calibration procedure could be suitable for any open path optical remote sensing instruments. In contrast to the complex beam geometries proposed in the past for CT, this radial scanning technique could be applied directly to air monitoring data from a variety of current optical sensing instruments. This development could vastly broaden the application of CT to obtain rapid reconstructions of ambient air pollution data.

In July 1997 the Republic of Korea became the 15th country to exceed 10-million registered motor vehicles. The number of cars has been increasing exponentially in Korea for the past 12 years opening an era of one car per household in this nation with a population of 44 million. The air quality effects of the growth of increasingly congested motor vehicle traffic in Seoul, home to more than one-fourth of the entire population, is of great concern to Korea's National Institute of Environmental Research (NIER). AIL's Open-Path FTIR air quality monitor, RAM 2000^TM, has been used to quantify the ozone increase over the course of a warm summer day. The RAM 2000 instrument was setup on the roof of the 6-story NIER headquarters. The retroreflector was sited 180-m away across a major highway where it was tripod-mounted on top of the 6- story Korean National Institute of Health facility. During the Open-Path FTIR data taking, NIER Air Physics Division research team periodically tethered an airborne balloon containing pump and a potassium iodide solution to obtain absolute ozone concentration results which indicated that the ambient ozone level was 50 ppb when the Open-Path FTIR measurements began. Total ozone concentrations exceeded 120 ppb for five hours between 11:30 AM and 4:30 PM. The peak ozone concentration measured was 199 ppb at 12:56 PM. The averaged concentration for five and a half hours of data collection was 145 ppb. Ammonia concentrations were also measured.

Recent improvements in signal processing techniques for Open- Path FTIR (OP-FTIR) have resulted in a dramatic reduction of detection limits for infrared active chemicals including ambient species. These lower detection limits opens the open- path FTIR technology to new applications involving monitoring and analyzing ambient air in urban settings. To test application of OP-FTIR technology to urban applications, an RAM2000^TM system was used over a seven-day period to measure ambient air-quality in an urban-industrial environment. Several of the ambient species which are ozone precursors and referred to as criteria pollutants in Title I of the Clean Air Act Amendment of 1990, have poor OP-FTIR detection limits because of overlap of their infrared absorption by very strong water vapor lines. Due to the high detection limits for sulfur dioxide and nitrogen dioxide, OP- FTIR has not been the technology of choice for measuring air quality in urban environments. In the present test, we were particularly interested in the improvements in the detection limits of the criteria pollutants, ozone, carbon monoxide, sulfur dioxide and nitrogen dioxide. Improvement in these detection limits will greatly increase the suitability of using OP-FTIR for measuring urban air quality and for measurement programs relating to the USEPA tropospheric ozone- photochemistry studies.

In February 1997, a pilot study was set up to evaluate the use of open-path Fourier Transform Infrared (OP-FTIR) technology for the determination of emission factors for ammonia at a dairy farm, alfalfa field, and waste water treatment plant in the San Joaquin Valley. In addition to the OP-FTIR monitoring, point sampling using active and passive denuder samplers and meteorological monitoring were also carried out. Limited tracer releases were made at the dairy farm and waste water treatment plant to assist in determining emission rates. This paper describes the OP-FTIR monitoring, tracer releases, meteorological monitoring and the resulting data with the implications for the determination of emission factors and improvements for future studies.

In summer 1998 a measurement campaign was performed at the lake Baldeney See in the south of the city of Essen in Germany. Two major goals should be achieved: First the intercomparison of several different remote sensing systems in real field measurements and second the determination of the ozone levels during summer with respect to the complex orographic and climatological situation of the lake Baldeney See which is intensely used as a recreational area. This paper only refers to the first results of the intercomparison of the remote sensing systems open-path FTIR, DOAS, and TDL and some interesting features of the ozone concentration results like secondary ozone peak concentration during night time.

Apodization functions used with FTIR instruments cause the response of the instruments to be nonlinear over the entire range of gas concentrations that are encountered in the atmosphere. FTIR remote sensors generally use the mathematical technique of classical least squares, along with a set of reference spectra to analyze the spectra. These reference spectra are normally supplied with the instrument and are taken at a single, specific concentration path-length product. At times, the atmospheric concentration path-length product is far removed from the concentration path-length product of the reference spectra, and this causes an error in the data. The error occurs because the mathematical process used in the final analysis of the data is linear but the instrument response is not. Classical least-squares, commonly used for this analysis, is a linear process that essentially multiplies the entire reference spectrum by a single multiplier over the wave number region used in the analysis. An important part of the analysis is how well the absorbance due to water vapor in the field spectrum is matched by the water vapor reference used in the analysis, and quite often this specific matching is not done very well. This paper explores the magnitude of the errors obtained when the reference concentration path- length product is not the same as that of the field spectrum - - for methane, which is of some environmental interest, and for water vapor specifically. This is done for the range of water vapor concentrations normally encountered in the atmosphere and for a range of temperatures.

During the last 10 years, open-path air monitors have evolved to yield reliable and effective measurements of single and multiple compounds on a real-time basis. To many individuals within the optical remote sensing community, the attributes of open-path and its the potential uses seem unlimited. Then why has the market has been stagnant for the last few years? The reason may center on how open-path information is applied and how well the end user understands that information. We constantly try to compare open-path data to risk/health or safety levels that are based for use at a single point and for a specific averaging period often far longer than a typical open-path data point. Often this approach is perceived as putting a square peg in a round hole. This perception may be well founded, as open-path data at times may need to go through extensive data manipulation and assumptions before it can be applied. This paper will review pervious open-path monitoring programs and their success in applying the data collected. We will also look at how open-path data is being currently used, some previous pitfalls in data use, alternate methods of data interpretation, and how open-path data can be best practically applied to fit current needs.

This paper describes the progress made to date in developing, testing, and refining a data reduction computer code, NONLIN, that alleviates many of the difficulties experienced in the analysis of open path FTIR data. Among the problems that currently effect FTIR open path data quality are: the inability to obtain a true I degree or background, spectral interferences of atmospheric gases such as water vapor and carbon dioxide, and matching the spectral resolution and shift of the reference spectra to a particular field instrument. This algorithm is based on a non-linear fitting scheme and is therefore not constrained by many of the assumptions required for the application of linear methods such as classical least squares (CLS). As a result, a more realistic mathematical model of the spectral absorption measurement process can be employed in the curve fitting process. Applications of the algorithm have proven successful in circumventing open path data reduction problems. However, recent studies, by one of the authors, of the temperature and pressure effects on atmospheric absorption indicate there exist temperature and water partial pressure effects that should be incorporated into the NONLIN algorithm for accurate quantification of gas concentrations. This paper investigates the sources of these phenomena. As a result of this study a partial pressure correction has been employed in NONLIN computer code. Two typical field spectra are examined to determine what effect the partial pressure correction has on gas quantification.

Fourier-transform infrared (FT-IR) spectrometry has become a useful real-time in situ analytical technique for quantitative gas phase measurements. In fact, the U.S. Environmental Protection Agency (EPA) has recently approved open-path FT-IR monitoring for the determination of hazardous air pollutants (HAP) identified in EPA's Clean Air Act of 1990. To support infrared based sensing technologies, the National Institute of Standards and Technology (NIST) is currently developing a standard quantitative spectral database of the HAPs based on gravimetrically prepared standard samples. The procedures developed to ensure the quantitative accuracy of the reference data are discussed, including sample preparation, residual sample contaminants, data processing considerations, and estimates of error.

In situ measurements with the prototype of a portable fiber- optic sensor system for the monitoring of nonpolar hydrocarbons (HC) in ground water or industrial waste water are presented. This sensor system can be used for quantitative in situ analysis of pollutants such as aromatic solvents, fuels, mineral oils or chlorinated HCs in a broad concentration range from around 200 (mu) g(DOT) L^-1 up to a few 100 mg(DOT) L^-1. The sensing principle is based on solid phase extraction of analyte molecules into a hydrophobic silicone cladding of a quartz glass optical fiber and the direct absorptiometric measurement of the extracted species in the polymer through the evanescent wave. The sensor can be connected via all-silica fibers with a length of up to 100 m to a filter photometer developed at the IFIA, thus allowing even remote analysis in monitoring wells. This instrument provides a sum concentration signal of the extracted organic compounds by measuring the integral absorption at the C-H overtone bands in the near-infrared spectral range. In situ measurements with the sensor system were performed in a ground water circulation well at the VEGAS research facility (Universitat Stuttgart). Here, the sensor proved to trace the HC sum concentration of xylene isomers in process water pumped from the well to a stripper column. In further experiments the sensor was combined with an oil sampling device and was tested with simulated waste waters of a commercial vehicle plant contaminated with different types of mineral oil. In this case the sensor system was able to detect the presence of mineral oil films floating on water or oil-in-water emulsions with concentrations greater than 20 ppm (v/v) within a few minutes.

We have recently developed instrumentation capable of quickly characterizing or monitoring a site using laser-induced fluorescence (LIF) measurements made through a sapphire window near the tip of a cone penetrometer (CPT) probe as it advances through the subsurface. By incorporating ten laser wavelengths simultaneously and collecting a full three-dimensional fingerprint of the soil sample at a vertical resolution of approximately 2 cm, we have made advances in site characterization using this technique, which enjoys all the advantages of in situ measurements: no exposure to, handling, custody or generation of hazardous waste is involved, and results are available in near real time. This report presents the results of recent work at Otis Air National Guard Base. First, a simple one-dimensional measure of the fluorescence fingerprints was correlated with laboratory results for total petroleum hydrocarbons (TPH), as a potentially convenient way for an operator of our instrument to monitor the results of the LIF measurements in real time, as the probe advances. Second, and more importantly, results are presented to demonstrate the potential of the instrumentation to identify individual target species and to quantify their concentrations approximately. The samples collected on site for conventional laboratory analysis were also measured by LIF and the resulting excitation-emission matrices (EEMs) were analyzed for ten target polycyclic aromatic hydrocarbons (PAHs). Qualitative and semi-quantitative agreement between these two sets of results was obtained. The agreements were extended to the in situ LIF data taken 2 - 3 feet away.

The new method 'Dynamic Derivative-Spectroscopy' (DDS) is presented for contamination detection and monitoring in water. As a first application, the selective measurement of aromatic solvents is investigated. The feasibility of the new technique to measure such substances selectively at competitive measurement speed is demonstrated. Selective monitoring is in contrast to the conventional 'Total Organic Carbon'-method (TOC) which determines only the total load of organic carbon in waste water. A measurement in the ultraviolet spectral range is appropriate since water has a high transparency in the effective wavelength range of a commercial Deuterium lamp. Further, DDS is also attractive for process control in chemical industry. To enhance spectral features for discrimination between the single sample components the first and second derivative of the transmission signal are used by DDS. The DDS technique makes use of a small periodic modulation of transmission wavelength of a monochromator to generate these signals in an optical manner. The corresponding modulation of the spectroscopic signal is treated by phase sensitive detection, which results in signals that correspond approximately to the first and second mathematical derivatives of the transmission. Experimental detection limits are below 0.1 mg analyte per liter water by using 10 cm absorption path and 3 minutes measurement time.

We report on development of microscale sensing devices for toxic heavy metals. These sensors-on-a-chip feature coupling of a microfluidic channel system with sensitive electrochemical detection to analyze heavy metals in aqueous samples. We have demonstrated ppb level heavy metal detection and are currently working to address detection in multianalyte mixtures, using anodic stripping voltammetry (ASV). Pb and Hg detection were facile and sensitive at this device, using a gold microband electrode and exploiting the hydrodynamic features of the device to facilitate preconcentration. Metals could be easily detected in the presence of large nitrate and acid backgrounds, e.g., 0.1 M nitric acid and in the presence of oxygen.

Potential human exposure to airborne metals occurs in a broad number of government and civilian operations and processes. Included among these are hard chromium plating, firing ranges, metallurgy and metals processing, lead paint abatement, and decontamination and decommissioning activities at hazardous waste sites. Effective control of these fugitive emissions requires sensitive real time monitoring. Physical Sciences Inc. (PSI) has developed a real time monitor for lead and chromium based on spark-induced breakdown spectroscopy (SIBS). The basis of SIBS is a high energy breakdown creating atomic emission which is sensitively viewed with a radiometer. This technology has been successfully demonstrated to detect low ppbw ((mu) g/m³) concentrations of lead and chromium in incinerator stack gases (joint DoE/EPA test a Research Triangle Park in September 1997), airborne lead at a local firing range (in the airspace of the shooters and in the ventilation system), and chromium at a hard chromium electroplating facility. The PSI SIBS technology is being developed as an inexpensive real time monitor for toxic metals in a variety of applications including: process control, emission compliance and industrial hygiene. Our progress towards developing a commercially viable prototype will be reviewed.

Accurate, real time air quality measurements are difficult to make, because real time sensors for some gas species are not specific to a single gas. For example, some carbon dioxide sensors react to hydrogen sulfide. By combining the response of several types of real time gas sensors the Real-time Air Quality Monitoring System (RAQMS) accurately measures many different gases. The sensor suite for the INEEL's Real-time Air Quality Monitoring System (RAQMS) incudes seven, inexpensive, commercially-available chemical sensors for gases associated with air quality. These chemical sensors are marketed as devices to measure carbon dioxide, hydrogen sulfide, carbon monoxide, sulfur dioxide, nitrogen dioxide, water vapor and volatile organic compounds (VOC's). However, these chemical sensors respond to more than a single compound, e.g. both the VOC and the carbon dioxide sensors respond strongly to methane. This multiple sensor response to a given chemical is used to advantage in the RAQMS system, as patterns of responses by the sensors were found to be unique and distinguishable for several chemicals. Therefore, there is the potential that the seven sensors combined output can: (1) provide more accurate measurements of the advertized gases and (2) estimate the presence and quantity of additional gases. The patterns of sensor response can be thought of as clusters of data points in a seven dimensional space. One dimension for each sensor's output. For all of the gases tested, these clusters were separated enough that good quantitative results were obtained. As an example, the prototype RAQMS is able to distinguish methane from butane and predict accurate concentrations of both gases. A mathematical technique for estimating probability density functions from random samples is used to distinguish the data clusters from each other and to make gas concentration estimates. Bayes optimal estimates of gas concentration are calculated using the probability density function. The Bayes optimal estimates are analogous to least square error curve fits or regression analysis. A computer program was used to find the best parameters for the Bayes optimal estimating functions. The program implemented a probabilistic neural net.

Several procedures have been used in the past 20 years for limiting pollution peaks around industrial sites in the lower SEINE Valley, in France. Some deal with general anticyclonic situations where pollutant dispersion is very slow. Some newer procedures deal with 'plume type' peaks where steady winds direct pollution toward communities nearby. In order to demonstrate improvement possibilities of these procedures, two measurement campaigns have been performed using several techniques including: (1) Dispersion models (both Gaussian and Lagrangian). The dispersion models were used both a predictive tools and a-posteriori to judge the effect of emission reduction. The models were part of the ADSO software suite from Aria Technologies. (2) A long path (integrating) monitor, the SANOA UV-DOAS, in order to assess average pollutant concentrations along a line as opposed to point monitoring. During this program, an original set-up for checking the performances and calibration of DOAS instruments was developed at INERIS. (3) A large set (11) of point monitors for SO2. (4) Several wind sensors, including ultrasonic anemometers, and a SOund raDAR (SODAR). (5) Mesoscale wind forecasts (the ALADIN prediction from METEO France). During the campaign, all data was collected in real time and wind model predictions were input periodically into dispersion models. Measurement and model data have been analyzed a-posteriori to determine a better tailoring of emission reduction to real situations. The European Commission supported this program through the LIFE financial instrument.

Ion mobility spectrometry with a photoemissive electron source is a promising approach for monitoring vapors of highly electronegative species such as chlorinated solvents and explosives. Electrons are generated over well-defined intervals by ultraviolet irradiation of a metal plate or metal-coated window by either a flashlamp or a pulsed laser beam, so no gating of the drift process is required. The negative ion mobility spectrum of air exhibits features predominately due to clusters of oxygen anion with water molecules. These species readily transfer electrons to chlorinated aliphatic compounds that undergo dissociative electron attachment to generate chloride ions. The ion mobility spectra change in a predictable fashion, permitting real-time detection of chlorinated species at low ppmV concentration. In this presentation we shall describe our methodology, display the response characteristics of our instrument, and summarize our investigations of the relevant ion-molecule reactions.

Several years of effort in IR polarimetry have brought us convincing evidence of its effectiveness in differentiating man made objects from natural backgrounds. Adding modern focal plane array (FPA) technology (either cooled or uncooled) makes it possible to combine the benefits of polarimetry with the power of hyperspectral imaging. Aerodyne Research is embarked on a stepwise, controlled-risk development program with the objective of fielding an innovative and affordable hyperspectral imaging IR polarimeter. Proof-of-concept demonstrations are conducted for each significant technology increment as part of the prototype development effort. These steps, two demonstrated and two yet to be demonstrated, are: (1) LWIR (non-imaging) Spectral Polarimeter to demonstrate the effectiveness of combined polarimetric and hyperspectral discriminating capabilities in observations on static scenes; (2) LWIR Uncooled FPA Imaging (broadband) Polarimeter to test the sensitivity of an affordable Uncooled FPA in a broadband configuration against static scenes; (3) Multispectral Imaging Polarimeter to quantify clutter rejection performance improvements to be realized in multispectral polarimetry; and (4) Hyperspectral Imaging IR Polarimeter designed with optimal spatial and spectral resolution and sufficient throughput to achieve the reliable performance required in surface mine and UXO detection applications. Results from the ongoing proof-of- concept demonstrations in simulated surface mine detection will be presented.

The detection of landmines and buried objects requires methods that can cover large areas rapidly while providing the required sensitivity to detect the optical and spectroscopic contrasts in soil properties that can reveal their presence. These conditions on contrast and coverage can be met by capturing images of the soil at wavelengths which are sensitive to the properties modified by the presence of buried objects. In this work we investigate both imaging and scanning methods which may have some utility for the detection problem. In the imaging approach, we capture hyperspectral reflection images using an acousto-optic tunable filter (AOTF) and fluorescence images using a long-pass filter. For the scanning method, we acquire data point-by-point over a two-dimensional grid with a single emitter/detector pair. The results illustrate the potential of these two approaches for detection of landmines and buried objects.

This paper introduces a new demining technique based on the photo-acoustic interaction, together with results from photo- acoustic experiments. We have buried different types of targets (metal, rubber and plastic) in different media (sand, soil and water) and imaged them by measuring reflection of acoustic waves generated by irradiation with a CO₂ laser. Research has been focused on the signal acquisition and signal processing. A deconvolution method using Wiener filters is utilized in data processing. Using a uniform spatial distribution of laser pulses at the ground's surface, we obtained 3D images of buried objects. The images give us a clear representation of the shapes of the underground objects. The quality of the images depends on the mismatch of acoustic impedance of the buried objects, the bandwidth and center frequency of the acoustic sensors and the selection of filter functions.

Infrared techniques can be used to detect buried objects such as landmines or shallow-buried waste, by taking advantage of the diurnal heating cycle. Improvements in performance may be expected with the addition of a microwave source to heat the ground and the buried objects. We describe an experiment to demonstrate the heating effect and a two-dimensional model which describes the phenomena involved. It is suggested that variations in heating with angle of incidence and microwave wavelength may be useful discriminants.

We present an analysis of statistical model based data-level fusion for near-IR polarimetric and thermal data, particularly for the detection of mines and mine-like targets. Typical detection-level data fusion methods, approaches that fuse detections from individual sensors rather than fusing at the level of the raw data, do not account rationally for the relative reliability of different sensors, nor the redundancy often inherent in multiple sensors. Representative examples of such detection-level techniques include logical AND/OR operations on detections from individual sensors and majority vote methods. In this work, we exploit a statistical data model for the detection of mines and mine-like targets to compare and fuse multiple sensor channels. Our purpose is to quantify the amount of knowledge that each polarimetric or thermal channel supplies to the detection process. With this information, we can make reasonable decisions about the usefulness of each channel. We can use this information to improve the detection process, or we can use it to reduce the number of required channels.

A concept is described for a Doppler Lidar capable of three- dimensional measurements. The concept is based on conventional line-of-sight lidar with multiple beams, each slightly displaced with respect to the other. A quadrature detection technique is used to provide sign determination so that three- dimensional velocities can be resolved unambiguously.

A shipborne fluorosensor laboratory has been built and used for extensive marine campaigns to monitor the quality of different seawaters including Mediterranean, Northern sea and Antarctic Ross sea. The core of the system is a compact lidar fluorosensor capable of single or dual laser excitation of the target. In the single excitation mode the detection of different chromophores characteristic of water impurities is possible, while the dual laser excitation is necessary to monitor the phytoplankton photosynthetic activity on the chlorophyll emission channel. A lamp spectrofluorometer, a pulsed amplitude fluorometer (PAM) and a solar radiance detector complete the set of instruments on board. Georeferenced data have been collected and released on thematic maps of the different seawater quality parameters (phytoplankton concentration, yellow matter, turbidity, biomass productivity, organic pollutants) remotely and in situ monitored during several marine campaigns.

Under contract to the US Air Force and Navy, Pacific Advanced Technology has developed a very sensitive hyperspectral imaging infrared camera that can perform remote imaging spectro-radiometry. One of the most exciting applications for this technology is in the remote monitoring of gas plume emissions. Pacific Advanced Technology (PAT) currently has the technology available to detect and identify chemical species in gas plumes using a small light weight infrared camera the size of a camcorder. Using this technology as a remote sensor can give advanced warning of hazardous chemical vapors undetectable by the human eye as well as monitor the species concentrations in a gas plume from smoke stack and fugitive leaks. Some of the gas plumes that have been measured and species detected using an IMSS imaging spectrometer are refinery smoke stacks plumes with emission of CO₂, CO, SO₂, NO_x. Low concentration vapor unseen by the human eye that has been imaged and measured is acetone vapor evaporating at room temperature. The PAT hyperspectral imaging sensor is called 'Image Multi-spectral Sensing or IMSS.' The IMSS instrument uses defractive optic technology and exploits the chromatic aberrations of such lenses. Using diffractive optics for both imaging and dispersion allows for a very low cost light weight robust imaging spectrometer. PAT has developed imaging spectrometers that span the spectral range from the visible, midwave infrared (3 to 5 microns) and longwave infrared (8 to 12 microns) with this technology. This paper will present the imaging spectral data that we have collected on various targets with our hyperspectral imaging instruments as will also describe the IMSS approach to imaging spectroscopy.

This optical tomography scanner for imaging (3D) applied density distribution as been evaluated for uniformity, resolution, and linearity. Signal to noise ratio of about 1000:1 in both line projection and in back projection reconstructed image has been obtained. Radiation-sensitive BANG^R polymer gels were studied using this system. Dose as low as 10 cGy up to 10 Gy for 6 MV X-ray and 6 MeV electrons from linear accelerator have been measured. Since the gels can be made UVlight sensitive, dose distribution could be used to measure exposure using this technique.

Direct-detection lidar has been demonstrated to be useful in locating probable sources of aerosol pollutants, and to some extent characterizing their density in a qualitative manner. Lidar has been less successful in producing quantitative maps of aerosol pollutants because it does not directly measure the quantity of interest. We describe a CO₂ lidar which has been used to measure airborne coal dust and propose its use in combination with a dispersion model to produce quantitative information.

More than twenty years have passed since the concept of combining Computed Tomography (CT) and Optical Remote Sensing (ORS) was first suggested to map air contaminants. However, there have been no commercial applications of CT-ORS due to a variety of reasons including hardware limitations and slow acceptance by the occupational and environmental scientific communities. A CT-ORS monitoring system provides the potential for near real-time mapping of multiple gases over large areas. Not just another nifty tool, this technology represents a major departure from conventional sampling methods and could allow us to understand chemical transport and exposure in ways, which are unavailable using conventional methods. Yet critical questions remain unanswered: which contaminant sources are most appropriate for this technology and how does this data apply to human exposure assessment? We discuss potential applications of CT-ORS, such a using open-path Fourier Transform Infrared spectroscopy for mapping leaks and evaluating worker exposures and quantifying emission flux from a process facility. Large scale (greater than 1 km) CT reconstructions could be obtained from a variety of ORS devices (Tunable Diode Laser, Differential Optical Absorption Spectroscopy, or Differential Absorption Lidar). Reconstructions could help locate industrial emissions and provide improved estimates of pollutant transport.

This paper presents a new approach to quantify emissions from fugitive gaseous air pollution sources. We combine Computed Tomography (CT) with Path-Integrated Optical Remote Sensing (PI-ORS) concentration data in a new field beam geometry. Path integrated concentrations are sampled in a vertical plane downwind from the source along several radial beam paths. An innovative CT technique, which applies the Smooth Basis Function Minimization (SBFM) method to the beam data in conjunction with measured wind data, is used to estimate the total flux from an area source. We conducted simulation study to evaluate the proposed methodology under two beam geometry and configurations. This approach was found to be robust for a wide range of fluctuating wind directions. In the very sparse beam geometry we examined (5 beam paths), successful emission rates were retrieved over a 70 degree range of wind directions.

Many industrial and environmental processes, including bioremediation, would benefit from the feedback and control information provided by a local multi-analyte chemical sensor. For most processes, such a sensor would need to be rugged enough to be placed in situ for long-term remote monitoring, and inexpensive enough to be fielded in useful numbers. The multi-analyte capability is difficult to obtain from common passive sensors, but can be provided by an active device that produces a spectrum-type response. Such new active gas microsensor technology has been developed at Argonne National Laboratory. The technology couples an electrocatalytic ceramic-metallic (cermet) microsensor with a voltammetric measurement technique and advanced neural signal processing. It has been demonstrated to be flexible, rugged, and very economical to produce and deploy. Both narrow interest detectors and wide spectrum instruments have been developed around this technology. Much of this technology's strength lies in the active measurement technique employed. The technique involves applying voltammetry to a miniature electrocatalytic cell to produce unique chemical 'signatures' from the analytes. These signatures are processed with neural pattern recognition algorithms to identify and quantify the components in the analyte. The neural signal processing allows for innovative sampling and analysis strategies to be employed with the microsensor. In most situations, the whole response signature from the voltammogram can be used to identify, classify, and quantify an analyte, without dissecting it into component parts. This allows an instrument to be calibrated once for a specific gas or mixture of gases by simple exposure to a multi-component standard rather than by a series of individual gases. The sampled unknown analytes can vary in composition or in concentration; the calibration, sensing, and processing methods of these active voltammetric microsensors can detect, recognize, and quantify different signatures and support subsequent analyses. The instrument can be trained to recognize and report expected analyte components (within some tolerance), but also can alarm when unexpected components are detected. Unknowns can be repeat-sampled to build a reference library for later post processing and verification.

We report a rapid and versatile organophosphorus hydrolase (OPH)-based method for measurement of organophosphate pesticides. This assay is based on a substrate-dependant change in pH near the active site of the enzyme. The pH change is monitored using fluorescein isothiocyanate (FITC) which is covalently immobilized to the enzyme. This method employs FITC-labeled enzyme adsorbed to polymethylmethacrylate beads. Analytes were measured using a microbead fluorescence analyzer. The dynamic concentration range for the assay extends from 25 (mu) M to 400 (mu) M for paraoxon with a detection limit of 8 (mu) M. This assay compared favorably to an HPLC method for monitoring the concentration of coumaphos in bioremediation filtrate samples.

Rapid assessment and monitoring of biological conditions in a subsurface environment is becoming more and more important as bioremediation approaches become widely used in environmental cleanup. Remediation monitoring is also more challenging for in-situ remedial approaches, such as bioventing, biosparging, or passive bioremediation, where conventional 'inlet' and 'outlet' monitoring can no longer be applied. A sensing approach using subsurface chemical sensors offers a cost- effective alternative for remediation monitoring. Additional benefits of deploying subsurface sensors include continuous and unattended measurement with minimum disturbance to the subsurface condition. In a series of field studies, an electrochemical oxygen sensor, a non-dispersive infrared (NDIR) carbon dioxide sensor, and two hydrocarbons sensors were employed for monitoring in-situ bioremediation of petroleum hydrocarbon contaminated soils. Biodegradation rates were effectively measured through an in-situ respiration measurement using subsurface oxygen and carbon dioxide sensors. The high sensitivity of the carbon dioxide sensor to small change in the concentration enables rapid respiration measurements. Subsurface hydrocarbon sensors offer a means to monitor the progress of remediation and the migration of contaminant vapors during the remediation. The chemical sensors tested are clearly cost effective for remediation monitoring. The strengths of oxygen and carbon dioxide sensors are complimentary to each other. Strengths and limitations of different hydrocarbon sensors were also noted. Balancing cost and performance of sensors is crucial for environmental remediation application.

Different sensing systems suitable for the determination of pesticides, metals and chlorinated organic compounds are described. The systems are based on the use of conjugated polymers and biological components that are sensitive to compounds commonly used as pesticides, chlorinated phenoxy herbicides or industrial chemicals. Biological molecules were immobilized on various carriers and were integrated in multiarray formats or in automated flow-through systems. This work describes the synthesis and characterization of polymers, biological conjugates and metabolites for the detection of a range of toxic chemicals, including chlorinated phenols, s- triazine herbicides, polychlorinated biphenyls, and heavy metals. The characteristic features of the different formats are given including a new promising approach for heavy metal detection using o-hydroxypyridylazo metal-protein conjugates.

Visualizing bacterial cells and describing their responses to the environment are difficult tasks. Their small size is the chief reason for the difficulty, which means that we must often use many millions of cells in a sample in order to determine what the average response of the bacteria is. However, an average response can sometimes mask important events in bacterial physiology, which means that our understanding of these organisms will suffer. We have used a variety of instruments to visualize bacterial cells, all of which tell us something different about the sample. We use a fluorescence activated cell sorter to sort cells based on the fluorescence provided by bioreporter genes, and these can be used to select for particular genetic mutations. Cells can be visualized by epifluorescent microscopy, and sensitive photodetectors can be added that allow us to find a single bacterial cell that is fluorescent or bioluminescent. We have also used standard photomultipliers to examine cell aggregates as field bioreporter microorganisms. Examples of each of these instruments show how our understanding of bacterial physiology has changed with the technology.

A study of the pH sensing characteristics of long lived Ru(II) complexes on a solid polymer support is presented. The systems selected were [Ru(Ph₂phen)₂DEAMbpy]²⁺ and [Ru(Ph₂phen)₂(DEAM)₂bpy]²⁺ (Ph₂phen equals 4,7-diphenyl-1, 10-phenanthroline, DEAMbpy equals 4-methyl-4'-(diethylamino)methyl-2,2'-bipyridine, (DEAM)₂bpy equals 4,4'-bis(diethylamino-methyl)-2,2'- bipyridine). The support is a very hydrophobic cyclic siloxane crosslinked with hydrophilic polyethylene oxide. Sensor preparation, based on hydrophobic binding of the sensor molecule to the polymer's hydrophobic pockets, is fast and convenient. While in solution both complexes have large changes in responses in the physiological pH range of 7 - 8, the polymer bound complexes show significantly different responses with pH. Either the magnitude of the response is reduced to too low a level to be valuable, or the pH of optimum response is shifted outside the 7 - 8 region. This muting and shifting of response is quite different from that observed for other pH sensor complexes on the same support. The possible origins of the effect are discussed. In spite of being unsuitable in the current formulation for physiological pHs [Ru(Ph₂phen)₂(DEAM)₂bpy]²⁺ shows useful response in both the 3 - 5 and 8 - 10 pH ranges.

Real-time calibrated atomic emission spectroscopy in stack exhaust using a continuously sustained microwave plasma is under development for trace metals monitoring. The plasma, in a shorted waveguide attached to the stack by a short sample line, is powered at 1.5 kW, 2.45 GHz. An undiluted stack slipstream is isokinetically directed into the plasma at a nominal flow of 14 liters per minute. A pneumatic nebulizer attached to the sample line can momentarily, on command, inject a known concentration of metals solution providing a real-time calibration. Recent testing has been performed on the exhaust stack of an incinerator at the Environmental Protection Agency (EPA) National Risk Management Laboratory in Research Triangle Park. Three hazardous metals were monitored, lead, chromium, and beryllium. These measurements were referenced to EPA Method-29. A total of twenty spiked stack exhaust tests were carried out. Ten one-hour tests at high concentration (40 - 60 (mu) g/actual m³) and ten one and half-hour tests at low concentration (10 - 15 (mu) g/actual m³). The microwave plasma monitor achieved measurement accuracies of approximately 20% for lead and beryllium and 40% for chromium with a threshold detection capability of less than 3 (mu) g/actual m³ for a time response of approximately 1-minute. Laboratory work is continuing to add mercury, arsenic, and cadmium to the monitored metals.

A spectrometer system consisting of a quartz acousto-optic tunable filter (AOTF) and an echelle grating has been assembled and tested for ICP-AES continuous emission monitoring of heavy metal and actinide elements in stack exhaust offgases introduced into an air plasma. The AOTF is a rapidly tunable bandpass filter that is used to select a small wavelength range (0.1 to 0.6 nm) of optical emission from the air plasma; the echelle grating provides high dispersion, yielding a spectral resolution of approximately 0.004 to 0.008 nm from 200 to 425 nm. The AOTF-echelle spectrometer, equipped with a photodiode array or CCD, provides rapid sequential multielement analysis capabilities. It is much more compact and portable than commercial ICP-AES echelle spectrometers, allowing use of the system in field and on-line process monitoring applications. Data will be presented that detail the resolution, detection limits, capabilities, and performance of the AOTF-echelle spectrometer for continuous emission monitoring of heavy metals (As, Be, Cd, Cr, Hg, and Pb) and actinides (including U isotopes). The potential use of the AOTF-echelle spectrometer with other emission sources and for other monitoring applications will be discussed.

Spectroscopic studies were performed both on uranium oxides as baseline and on uranium oxides artificially weathered under known laboratory conditions in air, varying humidity, carbon dioxide concentration, temperature and exposure to UV light. Spectroscopic techniques included photoluminescence and diffuse reflectance FTIR. Photoluminescence measurements were made using a Spex Fluorolog-3^TM spectrofluorometer with phosphorimeter. FTIR measurements were made using a Bomem MB157 FTIR spectrophotometer with DTGS detector and approximately 450 cm^-1 cut-off and a Graseby Selector^TM diffuse reflectance accessory with special cells and diamond dust as diluent and internal standard. Weathered-related reactions involving the uranium oxides that have been studied include oxidation and the formation of hydroxides and carbonates. Data are discussed with respect to both the reactions of the uranium oxides in the study and in context of reaction chemistry and mechanisms that have been previously documented. The results will be discussed in the context of environmental monitoring.

Digital filtering, principal component analysis (PCA), and an automated anomaly picker have been used to improve and automate target selection of unexploded ordnance (UXO). This is the first step in a three part program to develop new data analysis methods to automate target selection and improve discrimination of UXO from clutter and ordnance explosive waste (OEW) using magnetometry (Mag) and electromagnetic induction (EM) survey data. Traditionally, target detection has been accomplished by a time-consuming manual interactive data analysis approach. Experts screen the magnetometer data and select potential UXO targets based on their intuitive experience. EM data has been used in a secondary role in this process and the anomaly picking included classification and operator bias. In this program, the target detection step will use all of the data available and a separate classifier process will be used for identification and discrimination. Digital filtering is being used to enhance important features and reduce noise, while principal component analysis is being used to fuse three channels of data and reduce noise. Seven 50 meter-square data sets from two test sites were used to investigate these techniques. Features of interest are enhanced using filtering techniques. Inspection of the first- principal component suggests that data fusion of the magnetometer and EM data can be successfully accomplished. The new image consisting of circular features of varying diameters and intensities represent significant features present in all three data channels. Data with strong magnetometer and EM signals have the greatest intensity and in most cases noise is reduced. An automated anomaly picker has been designed to select targets from Mag, EM and PCA images. The method is fast and efficient as well as providing user options to control pick criteria.

We have measured radiation ((gamma) ray) induced loss of P- doped and Ge-doped fibers with different dopant concentrations and core diameters for different dose rates. The following conclusions can be obtained from our experiment: (1) The fibers we tested (P and Ge doped) have no evident recovery after (gamma) ray radiation. (2) No evident photo-bleaching effect had been observed by irradiating the fiber with diode laser of wavelength 630 micrometer. (3) Optical fiber with higher dopant concentration does not mean more sensitive. (4) For fiber length as short as 0.3 m, the sensitivity of P-doped fiber (0.6 - 0.8 dB/m for total dose of 4 Gy) is sufficient for the measurement of dose range for patients.

Three-dimensional optical memories which utilize two-photon processes have been proposed for use as a radiation dosimeter. The 'bits' stored by the optical memory are altered by the passage of radiation and can yield information about the dose and energy. In this work, the 'write' process of a two-photon optical memory is examined. This process uses a crossed-beam excitation scheme. By considering the spatial and temporal properties of the excitation sources used to drive the two- photon transitions, conditions are derived under which the number of absorption events due to the crossed-beams acting together outnumber the background events.