In Mexico, there are several environmental issues which are being addressed under the current governmental legislation. One important issue is restoring sites belonging to Petroleos Mexicanos (PEMEX). PEMEX is a large government owned oil company that regulates and manages the oil reserves. These sites are primarily contaminated with weathered hydrocarbons which are a consequence of extracting millions of barrels of oil. Within the southern regions of Mexico there are sites which were contaminated by activities and spills that have occurred during the past 30 years. PEMEX has taken the leadership in correcting environmental problems and is very concerned about cleaning up the contaminated sites as quickly as possible. The most significant contaminated sites are located to the north of Veracruz and south of Tabasco. These sites areas are close to refineries or locations of oil exploration. The primary category of contaminants are hydrocarbons, among them asphaltens, aromatic and other contaminants. The concentration of the contaminants varies depending on the location of the sites, but it can reach as high as 500,000 ppm. PEMEX has been searching for appropriate, and cost- effective technologies to clean up these sites. Biologically based remediation activities are of primary interest to PEMEX. However, other treatment technologies such as chemical-physical methods, encapsulation and incineration are also being considered. The present report summarizes preliminary experiments that measured the feasibility of bioremediation for a contaminated site in southern Mexico.

A Scanning Fluorescence Microscope system for quantifying and mapping biological growth on stone is described. The system uses 488 nm light from an Argon-ion laser to excite the 685 nm fluorescence from the Chlorophyll-a in the algae and uses this as the means of mapping the biological material. The measured 685 nm fluorescence is shown to increase linearly with the quantity of algae on the stone surface. Application of the system to study the effectiveness of biocide treatment for the control of algae on stone is reported.

Environmental assessment is important to evaluate the overall health and ecological impact of domestic and industrial wastes. Biosensors are kinds of analytical devices which consist of biomaterials and transducers. Photoluminescence of recombinant E.coli containing lux related genes were used as indicators of environmental pollutions. This paper deals with sensitive and rapid optical sensing systems for monitoring BOD (Biochemical Oxygen Demand), toxic compounds and mutagens.

Bioremediation is the use of living systems, usually microorganisms, to treat a quantity of soil or water for the presence of hazardous wastes. Bioremediation has many advantages over other remediation approaches, including cost savings, versatility, and the ability to treat the wastes in situ. In order to study the processes of microbial bioremediation, we have constructed bacterial strains that incorporate genetically engineered bioreporter genes. These bioreporter genes allow the bacteria to be detected during in situ processes, as manifested by their ability to bioluminesce or to fluoresce. This bioreporter microorganisms are described, along with the technology for detecting them and the projects which are benefiting from their application.

Raman spectroscopy has many characteristics that make it a viable method for monitoring contaminants in the environment [1 ,2]. Most significant for the work discussed in this presentation is the ability to transmit the Raman excitation (visible or NIR laser light)and the Raman scattering over long distances of optical fibers. This will allow one to operate at a workstation that is far removed from the actual site of contamination. The other advantage of Raman over similar in-situ optical methods of analysis is a high degree of molecular specificity. Raman is capable of providing molecular identification of the analyte.

Survey methods for compositional analysis of nuclear wastes and contaminated soils are under development to support characterization prior to treatment and continued monitoring during remediation. Laser ablation in conjunction with optical spectroscopy and mass spectroscopy are attractive because of the safety and convenience of minimal sample handling and very small sampling volume. However, the signal intensities in analytic applications depend sensitively on the physical state of the sample (e.g., particle morphology, defect concentration, impurities, and presence of liquids). In this work, we examine how solid and condensed state properties of the sample affect the laser-substrate interaction, and the dynamic electronic, physical, and chemical processes which ultimately generate the signals that are detected for analytic purposes.

Fiber optic probes employing single channel laser excitation and fluorescence collection have been seeing increasing use for remote sensing applications. However, multi-channel systems offer enhanced capacity for qualitative and quantitative determination of analytes. We describe a system which employs simultaneous delivery of laser excitation wavelengths arising from stimulated Raman scattering. Separate fluorescence responses for each excitation channel are imaged through a spectrograph onto a CCD array detector. Each channel has a dedicated fiber optic pair to deliver and collect light. REsults will be presented which evaluate the capabilities of this type of spectrometer for determination of organic contaminant mixtures in various sample matrices.

A fiber optic probe for use in the in situ delineation of subsurface metal contamination is described. The probe is based on the technique of laser-induced breakdown spectroscopy and is designed for deployment via a standard cone penetrometer truck. Initial measurements of the detection limits of the probe on Pb and Cr contaminated sands are in the low ppm range.

Individual aerosol particles are analyzed on the fly by on- line laser desorption ionization. The aerosol is sampled directly into a mass spectrometer where individual particles are detected by light scattering and then ablated by a high energy laser pulse. Ions produced by the ablation event are analyzed by time-of-flight mass spectrometry. Potential applications include laboratory investigations of aerosol reactions, field measurements of ambient particles, and detection of aerosol products and contaminants in manufacturing processes.

Matrix-assisted laser desorption ionization (MALDI) is an effective ionization technique for mass spectrometry. It take advantages of some unique properties of certain organic chemicals to provide entrapment, isolation, vaporization, and ionization of the analyte of interest. While the main application of the MALDI technique is currently in the area of biological molecule analysis, it is possible to use this technique for monitoring polymer chemistry such as degradation processes. This is potentially important for studying and developing environmentally degradable polymers. Direct analysis of the analyte in real-world samples is possible with MALDI. However, there is a significant effect of the overall composition of a sample on the detectability and performance of MALDI. Two examples are given to illustrate the positive and negative effects of buffers, salts, and additives on the MALDI sample preparation.

Effective field monitoring systems are needed to improve the quality and increase the use of environmental monitoring. Most laboratory-based systems, although powerful tools for the laboratory analyst, are not well-suited for field applications. Continuous, in-situ sensors provide real time data with high accuracy and low cost for multiple analyses. Optical sensor technologies are highly accurate and sensitive, are capable of being used in-situ and are highly versatile in terms of their potential applications. Fiber Optic Chemical Sensors (FOCS^TM) utilize the characteristics of optical sensors to provide an effective tool for continuous environmental monitoring. The FOCS^TM technology has recently been adapted to a new platform: a chip-level, solid state, optical waveguide, chemical sensor. This new optical platform provides several advantages of the FOCS^TM, and further improves the effectiveness of optical sensors for environmental monitoring. The chip-level optical sensor platform has been used with different optical sensing mechanisms (e.g., refractive index, absorbance and fluorescence) for the detection of hydrocarbons, carbon monoxide, oxygen and pesticides.

Researchers at the Idaho National Engineering Laboratory with their industrial CRADA partner GEO-CENTERS demonstrated a fiber optic based VOC sensor at the Army Environmental Center technology demonstration at Dover Air Force Base. The sensor used during the demonstration was a single fiber optic cable coupled to an in situ sensor element contained in a cone penetrometer tip. The sensor's fluorescence response was measured at the surface using an optical breadboard-based instrument. Results from this demonstration showed that the sensor provided semi-quantitative results for total VOCs comparable to the historical values of VOCs. In addition, the demonstration identified several technical challenges for improvement of the sensor. This paper describes the analytical properties of the reversible sensing materials, construction of an improved sensor system, and the planned demonstration of the modified in- situ VOC sensor system. This sensor system is tentatively scheduled for demonstration at the Army Environmental Center's Aberdeen Proving Ground Test site. Improvements to the VOC sensor system include an optical configuration that will correct for soil matrix interferences and multiple sensing substrates to learn whether VOC selectivity can be achieved.

In the present paper results of our LIF measurements of mineral oils on soil surfaces are briefly described. In order to characterize the influence of the analytes on the LIF signals we have measured the photophysical properties of different mineral oils in solution. An attempt to correlate the analytical parameters of the LIF calibration curves on soil surfaces with the photophysical properties in solution is presented.

A sensitive absorbance measurement method based on multi- wave mixing optical method is demonstrated as an effective detector for capillary electrophoresis or liquid chromatography. The use of a single focusing lens to focus and mix the two input beams both simplifies the optical setup and utilizes the laser power very efficiently inside a small probe volume. Hence, inexpensive low-power (mW level) lasers can be used in this nonlinear multi-photon detection method, including low-power argon ion lasers, He-Ne lasers and laser diodes. The resulting small (pL range) probe volume (laser beam overlap zone) allows convenient interfacing of this detector to capillary-based electrophoresis or chromatography separation systems. Excellent signal collection efficiency (virtually 100%) for the collimated coherent signal beam, allows detection sensitivity levels similar to those of fluorescence-based methods, and yet wave-mixing detectors are applicable for both fluorescing and non-fluorescing flowing analytes. The coherent signal beam is generated by thermally-induced refractive-index spatial gratings formed by the two input beams, and hence, the signal strength also depends on some solvent properties. The wave-mixing detector is demonstrated to be effective for trace analysis, offering advantages such as detection in very small sample volumes, remote and in situ analysis, and convenient as well as efficient alignment enhancements obtained by the introduction of optical fibers into the detector optical setup.

Volatile aromatic hydrocarbons such as benzene, toluene, ethylbenzene, and xylenes (BTEX), and styrene, aniline, and phenol can be directly and sensitively detected in ambient air by resonance-enhanced multiphoton ionization (REMPI) spectroscopy. The REMPI spectra closely resemble conventional absorbance spectra, but the REMPI technique is far more sensitive. Detection limits for directly focused tunable laser light into the ionization cell are less than 10 ppbv for BTEX and less than 1 ppbv for styrene, aniline, and phenol. Benzene in aqueous solution was remotely detected down to concentrations at the (mu) g/L level by a headspace analysis in which light was delivered to the ionization cell over a 20-meter long optical fiber.

Advances in spectroscopic techniques have led to a better understanding of the atmospheric chemistry of volatile organic compounds (VOC). Two important atmospheric properties of VOC's are the hydroxyl radical (OH(DOT)) rate constant and OH(DOT)/VOC reaction products. Gas chromatography and gas chromatography/mass spectroscopy/infrared spectroscopy are currently used in our laboratory to obtain this data. The OH(DOT) rate constant and reaction products have been investigated for 2-ethoxyethyl acetate (CH₃C(equalsO)OCH₂CH₂OCH₂CH₃), a paint thinner and paint component. Using the spectroscopic techniques mentioned above, the first detailed atmospheric reaction mechanism for 2-ethoxyethyl acetate will be presented. New areas of atmospheric research utilizing spectroscopic techniques will be discussed.

Electrochemiluminescence (ECL) is an electrochemical means of generating light from certain organic-metal complexes (e.g., Cr, Os, or Ru with bipyridine) and other types of molecules. Thus, it may be possible to develop an ECL-based metals sensor or biosensor consisting of organic molecules coated onto electrodes which emit light only upon complexation of particular metal ions and application of a small voltage. Toxic metals in water sources are of environmental concern. Some marine invertebrates, such as tunicates (i.e., `sea squirts') and molluscs, are noted for their ability to concentrate toxic metals as much as 100 million-fold over ambient seawater concentrations. In the present work, extracts from a tunicate species, as well as synthetic tunicate blood pigments or `tunichromes', oysters, and other organisms are examined for intrinsic ECL in the presence and absence of various metal ions. Results suggest a promising novel, potentially sensitive, and specific means for metal ion detection based on ECL.

Field screening of fuel-contaminated soils using laser- induced fluorescence is a cost effective and timely method of characterizing contaminated sites. Data collected with laser-based screening tools are often extensive and difficult to interpret. Pattern recognition algorithms can be utilized to enable less highly trained personnel to identify contaminants. In this work, fluorescence intensity of various hydrocarbon fuels deposited on various soil types was measured as a function of emission wavelength and decay time, generating wavelength-time matrices. The data were arranged into a three mode array and subjected to trilinear decomposition (TLD). The results of the TLD were then utilized in pattern recognition schemes, specifically, linear discrimination and classification and hierarchical cluster analysis. Classification rates and clustering results indicate that these techniques can be very valuable tools in site characterization.

A sorbent-based gas chromatographic method provides continuous quantitative measurement of phosgene, hydrogen cyanide, and cyanogen chloride in ambient air. These compounds are subject to workplace exposure limits as well as regulation under terms of the Chemical Arms Treaty and Title III of the 1990 Clean Air Act amendments. The method was developed for on-sit use in a mobile laboratory during remediation operations. Incorporated into the method are automated multi-level calibrations at time weighted average concentrations, or lower. Gaseous standards are prepared in fused silica lined air sampling canisters, then transferred to the analytical system through dynamic spiking. Precision and accuracy studies performed to validate the method are described. Also described are system deactivation and passivation techniques critical to optimum method performance.

A field-deployable analyzer for the determination of metals in soils is described. The instrument is based on laser- induced breakdown spectroscopy (LIBS), a form of atomic emission spectroscopy. In the LIBS technique, powerful laser pulses are focused on the soil to form a series of microplasmas that vaporize and excite the elemental constituents of the soil. The plasma light is spectrally analyzed to determine the elemental composition. The results of an initial field test of the instrument are described and a brief critique of the results presented.

Eaton operates a corporate aircraft hanger facility in Battle Creek, Michigan. Tests showed that two underground storage tanks leaked. Investigation confirmed this release discharged several hundred gallons of Jet A kerosene into the soil and groundwater. The oil moved downward approximately 30 feet and spread laterally onto the water table. Test results showed kerosene in the adsorbed, free and dissolved states. Eaton researched and investigated three clean-up options. They included pump and treat, dig and haul and bioremediation. Jet fuel is composed of readily biodegradable hydrocarbon chains. This fact coupled with the depth to groundwater and geologic setting made bioremediation the low cost and most effective alternative. A recovery well was installed at the leading edge of the dissolved contamination. A pump moved water from this well into a nutrient addition system. Nutrients added included nitrogen, phosphorous and potassium. Additionally, air was sparged into the water. The water was discharged into an infiltration gallery installed when the underground storage tanks were removed. Water circulated between the pump and the infiltration basin in a closed loop fashion. This oxygenated, nutrient rich water actively and aggressively treated the soils between the bottom of the gallery and the top of the groundwater and the groundwater. The system began operating in August of 1993 and reduced jet fuel to below detection levels. In August of 1995 The State of Michigan issued a clean closure declaration to the site.

A ship borne laser fluorescence system, design for use in conjunction with conventional water sampling techniques, for the improved detection and quantification of surface oil is described. Oil detection is achieved by firing the amplitude modulated 488 nm output beam of an Argon ion laser at the sea surface. The resultant fluorescence and scattered laser light are collected using a simple telescope arrangement and processed using a lock-in amplifier. The system is capable of detecting surface oil coatings of 20 (mu) l/m² with an operating range of up 6 - 20 m.

A very simple pH sensor is described which is suitable for in-situ measurement of groundwater. It uses fiber optics to transmit and receive light to and from a sensor which is based on the use of bleed-proof pH paper. The typical components for a single channel cost around 20 pounds.

An ammonia monitor designed for in situ smoke stack or exhaust duct applications is discussed here. A probe composed of a diffusion cell with a protected multipass optical measurement cavity provides the optical interaction with the sample. Other components of the system include signal processing electronics and an embedded PC104 computer platform. This instrument is useful in a wide variety of ammonia monitoring and process control applications, particularly ammonia-based NO_x control technologies, such as selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR). The in situ design eliminates sample handling problems, associated with extractive analysis of ammonia, such as sample line adsorption and heated sample trains and cells. The sensor technology exploited in this instrument is second harmonic spectroscopy using a near infrared diode laser. Data collected during field trials involving both SCR and SNCR applications demonstrate the feasibility and robust operation of this instrument in traditionally problematic operating environments. The instrument can measure other gases by changing the wavelength, either by changing the diode operational set point or by changing the diode. In addition, with straightforward modification the instrument can measure multiple species.

Multi-wave mixing spectroscopy is presented as a simple and sensitive laser method for elemental analysis at trace- concentration levels with sub-Doppler spectral resolution. Since the signal is a coherent beam, virtually 100% of the generated signal can be directed into a photodetector. The nonlinear signal has a cubic dependence on excitation intensity, and hence, laser power requirements are low, and mW-level continuous-wave lasers and nJ-level pulsed dye lasers can be used for this multi-photon spectroscopic setup. The optical alignment and beam quality requirements are relatively less demanding compared to other multi-photon methods, and hence, compact inexpensive lasers, including laser diodes, can be used. Since the coherence time and coherence length requirements are also relatively low, many types of laser sources can be used quite conveniently in this nonlinear spectroscopic setup. Parts-per-trillion level detection sensitivity can be obtained for a wide range of fluorescing and non-fluorescing analytes and matrices using various analytical atomizers. The graphite furnace atomizer offers many advantages, including convenient sample introduction for solid, liquid or gas analytes, high atomization temperature, clean atomization environment, and minimum source and chemical interferences, resulting in lower atomizer background noise. Taking advantage of the unique features of this multi-wave mixing optical method and those of a graphite furnace atomizer, one can obtain both excellent spectral resolution and detection sensitivity.

A real-time compound identification system for Fourier Transform Infrared Spectroscopy data has been based on the direct comparison of interferograms. Statistical pattern- recognition methods are applied to the feature extraction of infrared interferograms. Using large training sets, a real- time classification filter has been developed that is able to discriminate the specific-compound of infrared interferograms, and it has a very high probability. Our system can be used to identify several specific-compounds (several chemical vapors) of infrared interferograms of remote detection.

The opportunities of spatial-resolvable atmosphere monitoring and atmospheric pollutions' remote chemical analysis based on the CW-laser radiants are investigated. A frequency-responsive processing peculiarities of atmosphere remote sensing signals are described. Application of the mentioned approach for the limited hydrocarbons remote detection and sensing is discussed. The requirements to the CW-LIDAR' receiving and radiating systems parameters are formulated. The evaluations of the system sensitivity limit, measurement accuracy and accuracy increase ways are presented.

A family of multicomponent gas analyzers based on tunable diode lasers (TDL) are presented including: an open optical path 3-component gas analyzer for monitoring atmosphere pollution; a 4-gas component analyzer with a multipass cell, a multichannel TDL system with multipass cell and MIR fiber optics delivery, and a multichannel TDL analyzer for breath content gas analysis. A4B6 tunable diode lasers of different spectral region from 4 to 12 micron were used in every channel of the analyzers to obtain atmospheric transmission spectra and to measure concentration of studied gases. Main gaseous atmospheric pollutants like CO, NO, NH₃, CH₄, SO₂, etc. and some of breath gases could be measured at ppb concentration level in real time with these systems depending on customers requirements. The analyzers are driven by IBM compatible PC. The first results on field monitoring tests as well as on their application to human exhalation content analysis and human exposure monitoring are presented.

Using a genetic algorithm, we give here an account of the procedure to obtain the best vales for the parameters necessary to fit the efficiency for a X-ray detector. The values for some variables involved in quantitative PIXE analysis, were manipulated in a similar way as the genetic information is treated in a biological process. We carried out the algorithm until we reproduce, within the confidence interval, the elemental concentrations corresponding to a reference material.

The future need of safe disposal of chemical warfare agents and the increasing use of sulfur rich fuels make a quantitative understanding of the chemical reactions of similar containing compounds and their monitoring necessary. This report describes observations of the spectral emissions from the combustion of two different diffusion flames in a Seshadri type counterflow burner. These CH₄/air and H₂/air diffusion flames show almost identical flame structures in filtered CID camera and unfiltered color film pictures. Both display techniques show a single flame structure which is brightest in the near infrared. This structure exists as a thin band on the air inlet side of the burner close to the stagnation region. The location and spectral dependence of this radiation suggests spontaneous emission from vibration/rotation bands of the OH, e.g. the (3,0) lines centered at 950 nm and (4,0) lines at 730 nm. To explore the effects of sulfur containing hydrocarbons on the flame, (C₂H₅)₂S was added to the inlet air stream. The sulfur containing flames (with both CH₄ and H₂ as fuel) show the same emission bands as the unseeded flames with significant increases in spectral emission with increasing concentration of (C₂H₅)₂S in the oxidizer. As the mole fraction of (C₂H₅)₂S in air is increased from 0.3% to 2.0%, four new spectral bands successively appear, progressing from the stagnation region to the air inlet. Each of these thin bands radiates in the blue, i.e. wavelengths shorter than 500 nm. A single thin band close to the stagnation region increases with the (C₂H₅)₂S mole fraction and may be due to SH or SH₂ emissions. Radiation from the other three thin layers (about 1.5, 2.0 and 2.5 mm on the air inlet side) all increase with increasing (C₂H₅)₂S concentration. Consequently, they may be typical sulfur combustion products, such as CS, CS₂ or SO₂. At selected (C₂H₅)₂S concentrations, a bright red band appears, possibly S₂ emission.

The Site Characterization and Analysis Penetrometer System detects underground petroleum contamination using a laser induced fluorescence sensor that is hydraulically pushed into the ground by a 20 ton cone penetrometer truck. The sensitivity of the sensor depends on both the excitation wavelength and the composition of the petroleum contaminant. The efficiency of three laser sources (nitrogen laser at 337 nm, XeCl excimer laser at 308 nm and Nd:YAG laser at 266 nm) have been compared using soil spiked with fuels and various fuels dissolved in acetonitrile.